WO2018031166A1 - Global navigation satellite system (gnss) based synchronization source selection and reselection for vehicle-to-vehicle (v2v) communication - Google Patents

Global navigation satellite system (gnss) based synchronization source selection and reselection for vehicle-to-vehicle (v2v) communication Download PDF

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Publication number
WO2018031166A1
WO2018031166A1 PCT/US2017/041584 US2017041584W WO2018031166A1 WO 2018031166 A1 WO2018031166 A1 WO 2018031166A1 US 2017041584 W US2017041584 W US 2017041584W WO 2018031166 A1 WO2018031166 A1 WO 2018031166A1
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Prior art keywords
gnss
synchronization
synchronization source
interruption
circuitry
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PCT/US2017/041584
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French (fr)
Inventor
Andrey Chervyakov
Dmitry Belov
Alexey Khoryaev
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Intel Corporation
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Publication of WO2018031166A1 publication Critical patent/WO2018031166A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H04W56/001—Synchronization between nodes
    • H04W56/0015—Synchronization between nodes one node acting as a reference for the others

Definitions

  • GLOBAL NAVIGATION SATELLITE SYSTEM BASED SYNCHRONIZATION SOURCE SELECTION AND RESELECTION FOR VEHICLE-TO- VEHICLE (V2V)
  • LTE Long-Term Evolution
  • LTE-A 3GPP LTE- Advanced
  • Next-generation wireless cellular communication systems based upon LTE and LTE-A systems are being developed, such as a fifth generation (5G) wireless system / 5G mobile networks system, New Radio (NR) Access Technology, etc.
  • 5G fifth generation
  • 5G mobile networks system 5G mobile networks system
  • NR New Radio
  • Vehicular communication systems are networks in which vehicles and roadside units are the communicating nodes, providing each other with information, such as safety warnings, traffic information, etc., thereby creating the "connected cars" concept.
  • LTE technology may provide vehicles with wireless connections among each other (e.g., vehicle to vehicle or V2V communication) and to the Internet.
  • LTE-based V2X services (vehicle-to-vehicle or V2V, vehicle-to- infrastructure/network or V2I/N, vehicle-to-pedestrian V2P, etc.) were recently introduced (e.g., in LTE Release 14).
  • FIG. 1 schematically illustrates a Vehicle to Vehicle (V2V) communication system for synchronizing a UE in a vehicle using one of possibly multiple synchronization sources, according to some embodiments.
  • V2V Vehicle to Vehicle
  • FIG. 2 schematically illustrates, in high level, details of the UE of Fig. 1, according to some embodiments.
  • Fig. 3 illustrates a method for a UE to select and/or reselect an appropriate synchronization source to use as timing and/or frequency reference for one or more sidelink channels, according to some embodiments.
  • Fig. 4 illustrates transmission (TX) chain and/or reception (RX) chain activity during a synchronization source change to or from a GNSS synchronization source, according to some embodiments.
  • Fig. 5 illustrates synchronization source reselection being applied during a last symbol of a V2V subframe, according to some embodiments.
  • Fig. 6 illustrates an eNB and a UE, according to some embodiments.
  • FIG. 7 illustrates hardware processing circuitries for an eNB that supports a
  • UE selecting and/or reselecting appropriate synchronization sources for synchronizing the UE's sidelink channels, according to some embodiments.
  • Fig. 8 illustrates hardware processing circuitries for a UE for selecting and/or reselecting appropriate synchronization sources for synchronizing the UE's sidelink channels, according to some embodiments.
  • Fig. 9 illustrates a method for a UE to initiate an interruption while changing a synchronization reference source of the UE, according to some embodiments.
  • Fig. 10 illustrates a method for a UE to evaluate a GNSS synchronization source for at least a threshold period of time, before selecting another synchronization source or before resecting the GNSS synchronization source for resynchronization, according to some embodiments.
  • FIG. 11 illustrates an architecture of a system of a network, according to some embodiments.
  • Fig. 12 illustrates example components of a device, according to some embodiments.
  • Fig. 13 illustrates example interfaces of baseband circuitry, according to some embodiments.
  • sidelink channels in V2V communication, sidelink channels (or physical channels) may be used for communicating between UEs in vehicles.
  • the sidelink channels in a vehicle based UE may be synchronized (e.g., timing
  • eNB Evolved Node-B
  • UE vehicle based UE
  • GNSS Navigation Satellite System
  • signals are represented with lines. Some lines may be thicker, to indicate a greater number of constituent signal paths, and/or have arrows at one or more ends, to indicate a direction of information flow. Such indications are not intended to be limiting. Rather, the lines are used in connection with one or more exemplary embodiments to facilitate easier understanding of a circuit or a logical unit. Any represented signal, as dictated by design needs or preferences, may actually comprise one or more signals that may travel in either direction and may be implemented with any suitable type of signal scheme.
  • connection means a direct electrical, mechanical, or magnetic connection between the things that are connected, without any intermediary devices.
  • coupled means either a direct electrical, mechanical, or magnetic connection between the things that are connected or an indirect connection through one or more passive or active intermediary devices.
  • circuit or “module” may refer to one or more passive and/or active components that are arranged to cooperate with one another to provide a desired function.
  • signal may refer to at least one current signal, voltage signal, magnetic signal, or data/clock signal.
  • A, B, and/or C means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).
  • combinatorial logic and sequential logic discussed in the present disclosure may pertain both to physical structures (such as AND gates, OR gates, or XOR gates), or to synthesized or otherwise optimized collections of devices implementing the logical structures that are Boolean equivalents of the logic under discussion.
  • the term "eNB” may refer to a legacy eNB, a next-generation or NR gNB, a 5G eNB, an Access Point (AP), a Base Station or an eNB communicating on the unlicensed spectrum, and/or another base station for a wireless communication system.
  • the term "UE” may refer to a legacy UE, a next-generation or NR UE, a 5G UE, an STA, and/or another mobile equipment for a wireless communication system.
  • Various embodiments of eNBs and/or UEs discussed below may process one or more transmissions of various types. Some processing of a transmission may comprise receiving, conducting, and/or otherwise handling a transmission that has been received. In some embodiments, an eNB or UE processing a transmission may determine or recognize the transmission's type and/or a condition associated with the transmission. For some embodiments, an eNB or UE processing a transmission may act in accordance with the transmission's type, and/or may act conditionally based upon the transmission's type. An eNB or UE processing a transmission may also recognize one or more values or fields of data carried by the transmission.
  • Processing a transmission may comprise moving the transmission through one or more layers of a protocol stack (which may be implemented in, e.g., hardware and/or software-configured elements), such as by moving a transmission that has been received by an eNB or a UE through one or more layers of a protocol stack.
  • a protocol stack which may be implemented in, e.g., hardware and/or software-configured elements
  • Various embodiments of eNBs and/or UEs discussed below may also generate one or more transmissions of various types. Some generating of a transmission may comprise receiving, conducting, and/or otherwise handling a transmission that is to be transmitted. In some embodiments, an eNB or UE generating a transmission may establish the transmission's type and/or a condition associated with the transmission. For some embodiments, an eNB or UE generating a transmission may act in accordance with the transmission's type, and/or may act conditionally based upon the transmission's type. An eNB or UE generating a transmission may also determine one or more values or fields of data carried by the transmission.
  • Generating a transmission may comprise moving the transmission through one or more layers of a protocol stack (which may be implemented in, e.g., hardware and/or software-configured elements), such as by moving a transmission to be sent by an eNB or a UE through one or more layers of a protocol stack.
  • a protocol stack which may be implemented in, e.g., hardware and/or software-configured elements
  • Fig. 1 schematically illustrates a Vehicle to Vehicle (V2V) communication system 100 for synchronizing a UE in a vehicle 102 using one of possibly multiple synchronization sources, according to some embodiments.
  • Fig. 1 illustrates only two vehicles 102 and 106, although the system 100 may include a larger number of vehicles.
  • V2V Vehicle to Vehicle
  • each vehicle 102, 106 may include or embed communications equipment, such as a UE that may communicate in accordance with the V2V communication protocol.
  • a vehicle 102 may have an integrated, inbuilt, or an associated UE.
  • vehicle and the term "UE within the vehicle” (or vehicle based UE, or simply UE) may be used interchangeably.
  • a reference to the vehicle 102 may refer to the physical vehicle 102 and/or to a UE embedded within (or otherwise associated with) the vehicle 102. Accordingly, the vehicle 102 may also be referred to as UE 102.
  • a reference to the vehicle 106 may refer to the physical vehicle 106 and/or to a UE embedded within (or otherwise associated with) the vehicle 106.
  • the vehicle 106 may also be referred to as UE 106. Because the UEs 102, 106 may be integrated within respective vehicles, the UEs 102, 106 may also be referred to as vehicle based UEs.
  • the UE 102 may also communicate with the UE 106
  • the UE 102 may communicate with the UE 106 using one or more sidelink channels.
  • the UE 102 may communicate with a eNB 108 using appropriate wireless communication protocol on a cellular link (e.g. Uu link), e.g., using LTE, NR, 5G, or another communication protocol.
  • the UE 106 may communicate with the eNB 108, or with another eNB (not illustrated in the figure).
  • the UE 102 may also communicate with one or more satellites associated with a Global Navigation Satellite System (GNSS) 104.
  • GNSS Global Navigation Satellite System
  • Examples of GNSS 104 may include, for example, Global Positioning System (GPS), Globalnaya Navigazionnaya Sputnikovaya Sistema (GLONASS), Galileo, BeiDou, or other regional satellite systems.
  • GPS Global Positioning System
  • GLONASS Globalnaya Navigazionnaya Sputnikovaya
  • Galileo BeiDou
  • BeiDou BeiDou
  • FIG. 1 schematically illustrates a single satellite with reference to the label 104
  • the label 104 may represent multiple satellites associated with the GNSS 104.
  • the UE 102 may receive signals from one or more satellites of the GNSS 104, and may use the signals for synchronizing timing and/or frequency of sidelink channels of the UE 102, where the sidelink channels of the UE 102 may be used for V2V communication.
  • a reference to the GNSS 104 may imply to one or more components of the GNSS system 104, e.g., including one or more satellites associated with the GNSS system 104.
  • the UE 102 may use assistance from the GNSS 104 in order to adjust timing and/or frequency for the LTE sidelink channels transmission and/or reception.
  • the UE 102 may use signals from a GNSS disciplined oscillator, and such synchronization may be valid across multiple carriers.
  • GNSS synchronization may ensure relatively good accuracy in terms of timing reference and carrier frequency, however under certain conditions the accuracy of synchronization using the GNSS 104 may have relative degradation (e.g. Non-Line-Of-Sight (NLOS) satellites, blocked satellites, etc.).
  • NLOS Non-Line-Of-Sight
  • Using signals from satellites of the GNSS 104 for synchronizing the UE 102 may also be referred as herein as GNSS based synchronization.
  • the UE 102 may also receive synchronization signals from the eNB 108, and may synchronize the timing reference and/or carrier frequency (e.g., associated with the sidelink channels of the UE 102) based on the synchronization signals from the eNB 108.
  • the signals used to perform synchronization in such a manner may include PSS (Primary Synchronization Signal), SSS (Secondary Synchronization Signal), CRS (Cell-specific Reference Signal), and/or the like.
  • PSS Primary Synchronization Signal
  • SSS Secondary Synchronization Signal
  • CRS Cell-specific Reference Signal
  • Using signals from the eNB 108 for synchronizing the UE 102 may also be referred as herein as eNB based synchronization.
  • the UE 102 may also use signals from other UEs (e.g.,
  • the UE 106 may receive sidelink signals transmitted from other UEs (e.g., UE 106).
  • the signals from other UEs, which may be used to perform synchronization in the UE 102, may include SLSS (Sidelink
  • Synchronization Signals such as PSSS (Primary Sidelink Synchronization Signal), SSSS (Secondary Sidelink Synchronization Signal), PSBCH (Physical Sidelink Broadcast
  • UE based synchronization may also be referred as herein as UE based synchronization.
  • one or more synchronization sources may be available, where examples of such synchronization sources may be GNSS 104, eNB 108, other UEs (e.g., UE 106).
  • different synchronization source may have different priorities, e.g., depending on the scenario and network configuration parameters (e.g. GNSS based synchronization may be configured to have higher priority comparing to the eNB based synchronization).
  • priorities may be user configurable, and/or set by the carrier.
  • a V2V capable UE such as UE 102, may use the synchronization method with the highest priority and reasonably good signal quality, e.g., in order to derive timing and frequency synchronization (e.g., derive transmit timing reference and adjust carrier frequency for signal transmission and reception).
  • the GNSS based synchronization sources may have higher priority comparing to other synchronization sources (e.g., compared to eNB based or UE based sources).
  • the quality of the GNSS signal may be relatively poor and may not allow achieving sufficient synchronization accuracy (e.g., GNSS based synchronization may become worse compared to other synchronization sources).
  • Fig. 2 schematically illustrates, in high level, details of the UE 102 of Fig. 1, according to some embodiments.
  • the UE 102 may comprise GNSS circuitry 204 for communicating with the GNSS 104.
  • the GNSS circuitry 204 may be incorporated in a chipset, which may also be referred to as a GNSS chipset.
  • the UE 102 may also comprise LTE circuitry 208 for communicating with the eNB 108 and/or for communicating with other UEs (e.g., UE 106, via sidelink channels).
  • the LTE circuitry 208 may be incorporated in a chipset, which may also be referred to as a LTE chipset.
  • the LTE circuitry 208 may include RF (Radio
  • UE 102 may include numerous other components, such components are not illustrated in Fig. 2 for purposes of illustrative clarity.
  • the GNSS circuitry 204 may process signals received from one or more satellites associated with the GNSS 104.
  • an antenna and/or a receiver (not illustrated in Fig. 2) of the UE 102 may receive signals from the satellites associated with the GNSS 104, and the GNSS circuitry 204 may process the received signals.
  • the GNSS circuitry 204 may provide synchronization input to the LTE circuitry 208.
  • the GNSS circuitry 204 may provide the synchronization input to the LTE circuitry 208, which the LTE circuitry 208 may use to synchronize one or more sidelink channels of the UE 102 (e.g., if GNSS based
  • the GNSS circuitry 204 may provide the synchronization input to the LTE circuitry 208, for example, in the form of a reference signal from an output of the GNSS disciplined oscillator.
  • satellites of the GNSS 104 may maintain one or more GNSS disciplined oscillators.
  • the GNSS circuitry 204 may receive a reference signal from a GNSS disciplined oscillator of a GNSS satellite, and may transmit the reference signal to the LTE circuitry 208 (e.g., if GNSS based synchronization is used by the UE 102), to enable the LTE circuitry 208 to synchronize its sidelink channels based on the reference signal.
  • the GNSS circuitry 204 may also provide additional control information to the LTE circuitry 208, e.g., to characterize the reference signal.
  • the GNSS circuitry 204 may provide information to the
  • the LTE circuitry 208 on the GNSS synchronization signal quality (also referred to as “GNSS quality metrics” or as “GNSS quality metrics M”).
  • the GNSS circuitry 204 may provide the GNSS quality metrics M to the LTE circuitry 208 with a certain periodicity, e.g., with a periodicity of TGNSS_Update (although in some other embodiment, the GNSS circuitry 204 may provide the GNSS quality metrics M to the LTE circuitry 208
  • the GNSS quality metrics M may comprise an estimate of the GNSS reference signal timing accuracy, an estimate of the GNSS reference signal frequency accuracy, a signal strength and/or signal quality, information on the GNSS signal availability (e.g. GNSS signal is available or not), and/or one or more other metrics to characterize reference signal reliability of the GNSS 104.
  • the estimate of the GNSS reference signal timing accuracy may be associated with a metric Ml
  • the estimate of the GNSS reference signal frequency accuracy may be associated with a metric M2, and so on.
  • the LTE circuitry 208 e.g., an LTE modem within the LTE
  • the LTE circuitry 208) may estimate a GNSS synchronization reliability (R), e.g., based on the GNSS quality metrics M received from the GNSS circuitry 204.
  • the GNSS synchronization reliability may indicate a reliability of the GNSS 104 as a synchronization source. For example, if the signal strength or signal quality received from the GNSS 104 is relatively strong or good (e.g., better than a threshold), the GNSS 104 may be considered as a reliable synchronization source, as discussed herein below.
  • the LTE circuitry 208 may estimate the GNSS synchronization reliability R by, for example, comparing the GNSS quality metrics M to one or more thresholds.
  • the LTE circuitry 208 may perform pre-processing of the input GNSS quality metrics M (or derivatives of the GNSS quality metrics M), e.g., before comparing individual ones of the metric Mi to a corresponding threshold Ti.
  • pre-processing may comprise, for example, averaging several estimates of a metric Mi over a sliding time window, or some other type of averaging.
  • the GNSS synchronization is estimated to be reliable for a specific 1 th quality metric Mi in case the GNSS signal is better than the target threshold requirement Ti, otherwise signal is considered unreliable. Whether the metric Mi is better than the corresponding threshold Ti may be based on comparing the metric Mi with the corresponding threshold Ti.
  • a metric Mi is associated with a timing accuracy, or a frequency accuracy.
  • the GNSS synchronization is estimated to be reliable for the metric Mi (e.g., the GNSS signal is assumed to be better than the target threshold requirement Ti, and Ri is assigned the first value of 1) if Mi ⁇ Ti.
  • the GNSS synchronization is estimated to be not reliable for the metric Mi (e.g., the GNSS signal is assumed to be not better than the target threshold requirement Ti, and Ri is assigned the second value of 0) if Mi > Ti.
  • the metric Mi is associated with a quality (e.g., a quality of reference signals received form the GNSS 104).
  • the GNSS synchronization is estimated to be reliable for the metric Mi (e.g., the GNSS signal is assumed to be better than the target threshold requirement Ti, and Ri is assigned the first value of 1) if Mi > Ti.
  • the GNSS synchronization is estimated to be not reliable for the metric Mi (e.g., the GNSS signal is assumed to be not better than the target threshold requirement Ti, and Ri is assigned the second value of 0) if Mi ⁇ Ti.
  • each of the metrics Ml, ... , MN may be compared with a corresponding one of the thresholds TI, ... , TN, respectively, and the reliabilities RI, ... , RN, respectively, may be estimated.
  • the comparison against the threshold may be performed for multiple metrics Mi (e.g. time and frequency accuracy, quality, etc.).
  • the selection criteria may be expected to be satisfied for all metrics (e.g. timing accuracy, frequency accuracy, and quality has to be better than the threshold), e.g., to select the GNSS 104 as the synchronization source.
  • the metrics Ri may have to satisfy the selection criteria for the GNSS 104 to be selected as the
  • a corresponding threshold Tl may be defined as the LTE V2V transmit timing accuracy requirement for GNSS synchronization.
  • the threshold Tl associated with transmit timing accuracy may be 12 * Ts, where Ts may be about 1/(15000x2048) seconds. Ts has been discussed in 3GPP Technical Standard (TS) 36.211, Section 4. In an example, Ts may be a system sampling time.
  • a synchronization reliability Rl may be 1 if an associated timing accuracy metric Ml ⁇ (12 * Ts) (e.g., the accuracy is better than ⁇ 12 * Ts); and the synchronization reliability Rl may be 0 if the associated timing accuracy metric Ml > 12 * Ts.
  • a corresponding threshold T2 may be defined as a LTE V2V transmit frequency accuracy requirement for the GNSS synchronization.
  • the threshold T2 associated with the frequency accuracy metric M2 may be 0.1 ppm (parts per million) (e.g., accuracy of ⁇ 0.1 ppm).
  • GNSS synchronization reliability R 1
  • the UE 102 may decide on a synchronization source selection and/or reselection.
  • the decision to select and/or reselect a synchronization source may follow the following algorithm 1.
  • R 0
  • UE may attempt to select another synchronization source (e.g., use UE based synchronization or eNB based synchronization).
  • UE may start using GNSS
  • algorithm 1 provides a decision-making mechanism to select and/or resect a synchronization source for synchronizing sidelink channels of the UE 102 for V2V communication.
  • non-GNSS synchronization source (or synchronization source other than GNSS) may imply one or more of eNB based
  • algorithm 1 may result in frequent reselection of synchronization sources (e.g., frequent switching among the synchronization sources).
  • the UE 102 may enter an interruption period during which the UE 102 may not communicate effectively.
  • the UE 102 may implement an evaluation period of time, Tevaluate. For example, during the evaluation time period Tevaluate, the UE 102 may check whether a synchronization source is reliable or not.
  • the UE 102 may evaluate the GNSS synchronization source reliability for at least a threshold period of time (e.g., few seconds), before changing the synchronization reference source from GNSS to another synchronization reference source.
  • a threshold period of time e.g., few seconds
  • the UE 102 may evaluate the GNSS synchronization source for at least a threshold period of time (e.g., few seconds), e.g., for the purpose of deciding whether to perform selection and/or reselection of a new synchronization source.
  • a threshold period of time e.g., few seconds
  • the evaluation time period Tevaluate may be applied, for example, prior to, during and/or subsequent to comparing the GNSS quality metrics Mi to corresponding threshold Ti.
  • the evaluation time period Tevaluate may have a first value (e.g., Tevaluate_reliable) if the GNSS synchronization source is determined to be reliable; and the evaluation time period Tevaluate may have a second value (e.g., Tevaluate unreliable) if the GNSS synchronization source is determined to be unreliable.
  • the evaluation time period may be extended for other synchronization sources as well (e.g., eNB based synchronization source, UE based synchronization source, etc.).
  • the evaluation period Tevaluate may be implemented when, for example, the UE 102 is synchronized to the GNSS system 104, and the UE 102 is to change to a different synchronization source. In some embodiments, during the evaluation period Tevaluate, the UE 102 may evaluate the GNSS synchronization source reliability.
  • Fig. 3 illustrates a method 300 for a UE (e.g., UE 102) to select and/or reselect an appropriate synchronization source to use as timing and/or frequency reference for one or more sidelink channels, according to some embodiments.
  • a UE e.g., UE 102
  • methods that may relate to the UE 102 (or other implementations of a UE discussed herein later) and associated hardware processing circuitry are discussed below.
  • the actions in the method of Fig. 3 are shown in a particular order, the order of the actions can be
  • machine readable storage media may have executable instructions that, when executed, cause UE 102 and/or hardware processing circuitry included in the UE 102 to perform an operation comprising the method of Fig. 3.
  • Such machine readable storage media may include any of a variety of storage media, like magnetic storage media (e.g., magnetic tapes or magnetic disks), optical storage media (e.g., optical discs), electronic storage media (e.g., conventional hard disk drives, solid-state disk drives, or flash-memory-based storage media), or any other tangible storage media or non- transitory storage media.
  • an apparatus may comprise means for performing various actions and/or operations of the method 300 of Fig. 3.
  • the method 300 may comprise, at 304, processing one or more reference signals from a GNSS system (e.g., GNSS system 104).
  • a GNSS system e.g., GNSS system 104.
  • the processing may be performed by the GNSS circuitry 204.
  • GNSS synchronization signal quality metrics (e.g., GNSS quality metrics M discussed herein) may be generated.
  • the GNSS synchronization signal quality metrics may be generated by the LTE circuitry 208.
  • GNSS synchronization reliability (e.g., GNSS synchronization reliability R) may be evaluated (e.g., by the LTE circuitry 208).
  • the UE 102 may select or reselect an appropriate synchronization source for synchronizing its sidelink channels.
  • the UE 102 may perform the evaluation of the GNSS synchronization reliability for at least a threshold period of time (e.g., Tevaluate), before the UE 102 is to select another synchronization source at 316.
  • a threshold period of time e.g., Tevaluate
  • operations of the UE 102 may be interrupted. For example, such interruption may allow the UE 102 (e.g., the LTE circuitry 208) to adjust the transmission and/or reception (TX/RX) chains parameters. For example, due to the change in the synchronization source, parameters associated with a phase locked loop (PLL) may have to be changed.
  • PLL phase locked loop
  • a non-GNSS based synchronization source e.g. eNB based, or UE based
  • GNSS-based synchronization source e.g. eNB based, or UE based
  • Such an interruption period may enable the change of the synchronization source from a GNSS source to a non-GNSS source, or from a non-GNSS source to a GNSS source.
  • the UE 102 may interrupt (e.g., is allowed to interrupt) a transmission chain operation and/or a receive chain operation for a period Tinterrupt, e.g., during the synchronization source change to/from the GNSS synchronization source.
  • the interruption in operation may include interruption to signal transmission and/or reception.
  • the interruption period Tinterrupt may take one or more subframes.
  • the interruption period Tinterrupt may comprise up to one subframe (e.g., the Tinterrupt may be less than or equal to one subframe).
  • Such delay may be, for example, used to align the interruption with a subframe boundary (e.g., such that the interruption may not start in between a subframe).
  • the UE 102 may interrupt transmit and receive operation on the V2V carrier(s), e.g., one or more carriers in which the UE 102 is making transmissions and reception of V2V signals.
  • the interruption may be applicable to one or more of sidelink channels, uplink channels, and/or downlink channels.
  • the interruption may be applicable to one or more of V2V sidelink channels or sidelink signals, such as PSSCH (Physical Sidelink Shared Channel), PSCCH (Physical Sidelink Control Channel), PSBCH (Physical Sidelink Broadcast Channel), SLSS (Sidelink Synchronization Signals), etc.
  • the UE 102 may also interrupt operation on other carriers (e.g., on Primary Cell (PCell), activated Secondary Cells (SCells), etc.).
  • PCell Primary Cell
  • SCells activated Secondary Cells
  • the UE 102 may inform the eNB 108 about an upcoming interruption on the UE side, e.g., due to a change in the synchronization source. For example, the UE 102 may inform the eNB 108 on the anticipated interruption at the UE side via some dedicated signaling.
  • the interruption period Tinterrupt may be applicable for a synchronization source change to and/or from the GNSS synchronization source, the interruption period Tinterrupt (or a similar interruption period) may also be applicable for synchronization source change not involving the GNSS synchronization source. For example, when there is a synchronization source change between eNB based source and UE based source, the interruption period Tinterrupt (or a similar interruption period) may also be applicable.
  • Fig. 4 illustrates transmission (TX) chain and/or reception (RX) chain activity
  • the activity 400 is with respect to time.
  • the activity 400 may be applicable for sidelink TX chain and/or sidelink RX chain of the UE 102.
  • the UE 102 may have active sidelink
  • the UE 102 may use a non-GNSS synchronization source (e.g., eNB or EU based synchronization source), or a GNSS based synchronization source for synchronizing its sidelink channels.
  • a non-GNSS synchronization source e.g., eNB or EU based synchronization source
  • a GNSS based synchronization source for synchronizing its sidelink channels.
  • the UE 102 may make a decision to change the synchronization source from or to GNSS based synchronization source. For example, at time tl, the UE may decide to change the synchronization source from a non-GNSS based synchronization source to a GNSS based synchronization source, or from a GNSS based synchronization source to a non-GNSS based synchronization source.
  • the decision to change the synchronization source may be reached using an appropriate manner, e.g., using Algorithm 1 discussed herein previously, using the method 300 of Fig. 3, and/or the like.
  • the UE 102 may interrupt the TX/RX chain between time t2 and t3.
  • the time t2 may align with a start of a subframe boundary.
  • the delay between time tl and t2 may be to align the interruption period with a subframe boundary.
  • the time between t2 and t3 may be the interruption period Tinterrupt.
  • the UE 102 may perform the synchronization source switching, and may perform operations associated with such synchronization source switching. For example, due to the change in the synchronization source, parameters associated with a PLL may be changed during the interruption period Tinterrupt.
  • the UE 102 may operate in accordance with the new synchronization source, and the TX/RX chain may be active again from time t3.
  • the interruption period Tinterrupt may last for one or more subframes (e.g., last for one subframe).
  • the interruption period Tinterrupt may last for one or more subframes (e.g., last for one subframe).
  • the interruption period may last for one or more subframes (e.g., last for one subframe).
  • Tinterrupt may be referred to as long interruption time.
  • the synchronization source reselection (e.g., switching of the synchronization source, which may necessitate change of time and/or frequency reference) may not require the long interruption time of Fig. 4.
  • some impacts on the overall V2V demodulation performance may happen.
  • the synchronization source reselection is done during the V2V transmission, the transmitted packet may become corrupted (e.g. in case there is noticeable timing and/or frequency offset between the synchronization sources).
  • the packet reception may fail in case UE 102 changes the timing and/or frequency reference during the packet reception.
  • V2V physical layer structure may be implemented using a last symbol of individual V2V subframes (e.g., subframes in the sidelink channels) may not be used for sidelink signal transmission.
  • the synchronization source reselection may be performed during the last symbol of a V2V subframe, as illustrated in Fig. 5.
  • Fig. 5 illustrates synchronization source reselection being applied during a last symbol of a V2V subframe, according to some embodiments.
  • example subframes (N-l), N, and (N+l) are illustrated.
  • the subframes may be used for V2V communication.
  • the subframes may be used for sidelink channels.
  • the UE uses a synchronization source 1 during the subframe (N-l).
  • the UE 102 may decide on the synchronization source reselection (e.g., switch from the synchronization source 1 to a synchronization source 2) during subframe N, as illustrated in Fig. 5.
  • the UE 102 may continue using the synchronization source 1 for V2V communication in the subframe N.
  • the UE 102 may perform the switching of the time reference and/or the frequency reference from synchronization source 1 to the synchronization source 2 during the last symbol of subframe N. Because the last symbol of the subframe N is not anyway used for any transmission and/or reception, there may not be possibility of packets getting corrupted due to the synchronization source reselection during the last symbol of subframe N.
  • the UE 102 may use synchronization source 2 for V2V communication in the subframe (N+l).
  • the synchronization source 1 may be one of GNSS based synchronization source, UE based synchronization source, or eNB based
  • the synchronization source 2 may be another of GNSS based synchronization source, UE based synchronization source, or eNB based synchronization source.
  • the UE 102 may perform continuous monitoring of the SLSS transmissions from other UEs.
  • continuous monitoring of the SLSS transmissions from other UEs may result in drop of the SL transmissions from the UE 102, and/or may also lead to additional power consumption.
  • the UE 102 may refrain from using SLSS monitoring (e.g., continuous SLSS monitoring).
  • SLSS monitoring e.g., continuous SLSS monitoring
  • eNB based synchronization source has higher priority than SyncRef UE based synchronization (e.g., eNB based synchronization source has higher priority SLSS) and the UE 102 is located in network coverage with relatively good eNB-UE link quality (e.g., the eNB-UE link quality is better than a threshold)
  • SLSS monitoring e.g., continuous SLSS monitoring
  • the UE 102 may refrain from monitoring (e.g., continuously monitoring) SLSS transmissions from other UEs.
  • the eNB-UE link quality is low (e.g., the eNB-
  • the UE 102 may perform SLSS monitoring (e.g., may monitor SLSS transmissions from other UEs).
  • eNB based synchronization source has higher priority than SLSS based synchronization and (ii) eNB-UE link quality (e.g. RSRP) is above certain threshold, the UE 102 may not be allowed to drop its own sidelink transmissions and may refrain from monitoring SLSS transmission from other UEs.
  • eNB-UE link quality e.g. RSRP
  • Fig. 6 illustrates an eNB and a UE, according to some embodiments.
  • Fig. 6 includes block diagrams of an eNB 610 and a UE 630 which are operable to co-exist with each other and other elements of an LTE network. High-level, simplified architectures of eNB 610 and UE 630 are described so as not to obscure the embodiments. It should be noted that in some embodiments, eNB 610 may be a stationary non-mobile device. In some embodiments, the UE 630 of Fig. 6 may correspond to any UE discussed herein.
  • the eNB 610 is coupled to one or more antennas 605, and UE 630 is similarly coupled to one or more antennas 625.
  • UE 630 is similarly coupled to one or more antennas 625.
  • eNB 610 may incorporate or comprise antennas 605, and UE 630 in various embodiments may incorporate or comprise antennas 625.
  • antennas 605 and/or antennas 625 may comprise one or more directional or omni-directional antennas, including monopole antennas, dipole antennas, loop antennas, patch antennas, microstrip antennas, coplanar wave antennas, or other types of antennas suitable for transmission of RF signals.
  • antennas 605 are separated to take advantage of spatial diversity.
  • eNB 610 and UE 630 are operable to communicate with each other on a network, such as a wireless network (e.g., using licensed or unlicensed spectrum). eNB 610 and UE 630 may be in communication with each other over a wireless communication channel 650, which has both a downlink path from eNB 610 to UE 630 and an Uplink path from UE 630 to eNB 610.
  • a wireless network e.g., using licensed or unlicensed spectrum
  • eNB 610 may include a physical layer circuitry 612, a MAC (media access control) circuitry 614, a processor 616, a memory 618, and a hardware processing circuitry 620.
  • MAC media access control
  • physical layer circuitry 612 includes a transceiver 613 for providing signals to and from UE 630.
  • Transceiver 613 provides signals to and from UEs or other devices using one or more antennas 605.
  • MAC circuitry 614 controls access to the wireless medium.
  • Memory 618 may be, or may include, a storage media/medium such as a magnetic storage media (e.g., magnetic tapes or magnetic disks), an optical storage media (e.g., optical discs), an electronic storage media (e.g., conventional hard disk drives, solid-state disk drives, or flash-memory-based storage media), or any tangible storage media or non-transitory storage media.
  • Hardware processing circuitry 620 may comprise logic devices or circuitry to perform various operations.
  • processor 616 and memory 618 are arranged to perform the operations of hardware processing circuitry 620, such as operations described herein with reference to logic devices and circuitry within eNB 610 and/or hardware processing circuitry 620.
  • eNB 610 may be a device comprising an application processor, a memory, one or more antenna ports, and an interface for allowing the application processor to communicate with another device.
  • UE 630 may include a physical layer circuitry 632, a MAC circuitry 634, a processor 636, a memory 638, a hardware processing circuitry 640, a wireless interface 642, and a display 644.
  • a person skilled in the art would appreciate that other components not shown may be used in addition to the components shown to form a complete UE.
  • physical layer circuitry 632 includes a transceiver 633 for providing signals to and from eNB 610 (as well as other eNBs). Transceiver 633 provides signals to and from eNBs or other devices using one or more antennas 625.
  • MAC circuitry 634 controls access to the wireless medium.
  • Memory 638 may be, or may include, a storage media/medium such as a magnetic storage media (e.g., magnetic tapes or magnetic disks), an optical storage media (e.g., optical discs), an electronic storage media (e.g., conventional hard disk drives, solid-state disk drives, or flash-memory -based storage media), or any tangible storage media or non-transitory storage media.
  • Wireless interface 642 may be arranged to allow the processor to communicate with another device.
  • Display 644 may provide a visual and/or tactile display for a user to interact with UE 630, such as a touch-screen display.
  • Hardware processing circuitry 640 may comprise logic devices or circuitry to perform various operations.
  • processor 636 and memory 638 may be arranged to perform the operations of hardware processing circuitry 640, such as operations described herein with reference to logic devices and circuitry within UE 630 and/or hardware processing circuitry 640.
  • UE 630 may be a device comprising an application processor, a memory, one or more antennas, a wireless interface for allowing the application processor to communicate with another device, and a touch-screen display.
  • FIG. 6 depicts embodiments of eNBs, hardware processing circuitry of eNBs, UEs, and/or hardware processing circuitry of UEs, and the embodiments described with respect to Figs. 1-5 can operate or function in the manner described herein with respect to any of the figures.
  • eNB 610 and UE 630 are each described as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements and/or other hardware elements.
  • the functional elements can refer to one or more processes operating on one or more processing elements. Examples of software and/or hardware configured elements include Digital Signal Processors (DSPs), one or more microprocessors, DSPs, Field-Programmable Gate Arrays (FPGAs), Application Specific Integrated Circuits (ASICs), Radio-Frequency Integrated Circuits (RFICs), and so on.
  • DSPs Digital Signal Processors
  • FPGAs Field-Programmable Gate Arrays
  • ASICs Application Specific Integrated Circuits
  • RFICs Radio-Frequency Integrated Circuits
  • Fig. 7 illustrates hardware processing circuitries for an eNB that supports a
  • an eNB may include various hardware processing circuitries discussed below, which may in turn comprise logic devices and/or circuitry operable to perform various operations.
  • eNB 610 (or various elements or components therein, such as hardware processing circuitry 620, or combinations of elements or components therein) may include part of, or all of, these hardware processing circuitries.
  • one or more devices or circuitries within these hardware processing circuitries may be implemented by combinations of software-configured elements and/or other hardware elements.
  • processor 616 and/or one or more other processors which eNB 610 may comprise
  • memory 618 and/or other elements or components of eNB 610 (which may include hardware processing circuitry 620) may be arranged to perform the operations of these hardware processing circuitries, such as operations described herein with reference to devices and circuitry within these hardware processing circuitries.
  • processor 616 (and/or one or more other processors which eNB 610 may comprise) may be a baseband processor.
  • an apparatus of eNB 610 (or another eNB or base station), which may be operable to communicate with one or more UEs on a wireless network, may comprise hardware processing circuitry 700.
  • hardware processing circuitry 700 may comprise one or more antenna ports 705 operable to provide various transmissions over a wireless communication channel (such as wireless communication channel 650).
  • Antenna ports 705 may be coupled to one or more antennas 707 (which may be antennas 605).
  • hardware processing circuitry 700 may incorporate antennas 707, while in other embodiments, hardware processing circuitry 700 may merely be coupled to antennas 707.
  • Antenna ports 705 and antennas 707 may be operable to provide signals from an eNB to a wireless communications channel and/or a UE, and may be operable to provide signals from a UE and/or a wireless communications channel to an eNB.
  • antenna ports 705 and antennas 707 may be operable to provide transmissions from eNB 610 to wireless communication channel 650 (and from there to UE 630, or to another
  • antennas 707 and antenna ports 705 may be operable to provide
  • Hardware processing circuitry 700 may comprise various circuitries operable in accordance with the various embodiments discussed herein. With reference to Fig. 7, hardware processing circuitry 700 may comprise a first circuitry 710 and a second circuitry 720.
  • First circuitry 710 may be operable to cause transmission of reference signals to a UE, e.g., to enable the optionally synchronize with the reference signals (e.g., if the UE selects the eNB as a synchronization source).
  • Second circuitry 720 may be operable to cause transmission of other signals with the UE.
  • hardware processing circuitry 700 may be coupled to a transceiver circuitry for at least one of: generating transmissions, scheduling UL
  • transmissions encoding transmissions, processing transmissions, or decoding transmissions.
  • first circuitry 710 and/or second circuitry 720 may be implemented as separate circuitries. In other embodiments, first circuitry 710 and/or second circuitry 720 may be combined and implemented together in a circuitry without altering the essence of the embodiments.
  • Fig. 8 illustrates hardware processing circuitries for a UE for selecting and/or reselecting appropriate synchronization sources for synchronizing the UE's sidelink channels, according to some embodiments.
  • a UE may include various hardware processing circuitries discussed below, which may in turn comprise logic devices and/or circuitry operable to perform various operations.
  • UE 630 (or various elements or components therein, such as hardware processing circuitry 640, or combinations of elements or components therein) may include part of, or all of, these hardware processing circuitries.
  • one or more devices or circuitries within these hardware processing circuitries may be implemented by combinations of software-configured elements and/or other hardware elements.
  • processor 636 and/or one or more other processors which UE 630 may comprise
  • memory 638 and/or other elements or components of UE 630 (which may include hardware processing circuitry 640) may be arranged to perform the operations of these hardware processing circuitries, such as operations described herein with reference to devices and circuitry within these hardware processing circuitries.
  • processor 636 (and/or one or more other processors which UE 630 may comprise) may be a baseband processor.
  • an apparatus of UE 630 (or another UE or mobile handset), which may be operable to communicate with one or more eNBs on a wireless network, may comprise hardware processing circuitry 800.
  • hardware processing circuitry 800 may comprise one or more antenna ports 805 operable to provide various transmissions over a wireless communication channel (such as wireless
  • Antenna ports 805 may be coupled to one or more antennas 807 (which may be antennas 625).
  • hardware processing circuitry 800 may incorporate antennas 807, while in other embodiments, hardware processing circuitry 800 may merely be coupled to antennas 807.
  • Antenna ports 805 and antennas 807 may be operable to provide signals from a UE to a wireless communications channel and/or an eNB, and may be operable to provide signals from an eNB and/or a wireless communications channel to a UE.
  • antenna ports 805 and antennas 807 may be operable to provide transmissions from UE 630 to wireless communication channel 650 (and from there to eNB 610, or to another eNB).
  • antennas 807 and antenna ports 805 may be operable to provide transmissions from a wireless communication channel 650 (and beyond that, from eNB 610, or another eNB) to UE 630.
  • Hardware processing circuitry 800 may comprise various circuitries operable in accordance with the various embodiments discussed herein. With reference to Fig. 8, hardware processing circuitry 800 may comprise a first circuitry 810, a second circuitry 820, and/or a third circuitry 830.
  • first circuitry 810 may be operable to determine to change a synchronization reference source of the UE from a first synchronization source to a second synchronization source.
  • one of the first synchronization source or the second synchronization source is a GNSS synchronization source.
  • Second circuitry 820 may be operable to initiate an interruption of at least one of a signal transmission of the UE or a signal reception of the UE for an interruption period.
  • Third circuitry 830 may be operable to change the synchronization reference source of the UE from the first synchronization source to the second synchronization source, during the interruption for the interruption period.
  • interruption period comprises up to one subframe. In some embodiments, the interruption period comprises one or more subframes.
  • second circuitry 820 may be operable to initiate the interruption of one or more of PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink Synchronization Signals) signals.
  • PSSCH Physical Sidelink Shared Channel
  • PSCCH Physical Sidelink Control Channel
  • PSBCH Physical Sidelink Broadcast Channel
  • SLSS Segment Synchronization Signals
  • second circuitry 820 may be operable to initiate the interruption of sidelink signals transmitted between the UE and a second UE.
  • second circuitry 820 may be operable to initiate the interruption of V2V (Vehicle-to-Vehicle) sidelink signals.
  • second circuitry 820 may be operable to initiate the interruption to align with a boundary of at least one of a transmission subframe or a reception subframe. In some embodiments, second circuitry 820 may be operable to initiate the interruption during a last symbol of a V2V (Vehicle-to-Vehicle) subframe. In some embodiments, the UE may utilize the
  • the UE may generate a signal for transmission to the eNB, the signal to inform the eNB about the interruption.
  • synchronization source is one of a Serving Cell, a Primary Cell, or a second UE.
  • first circuitry 810 may be operable to synchronize, to a
  • second circuitry 820 may be operable to evaluate the GNSS synchronization source for at least a threshold period of time from the first time, before selecting another synchronization source or before resecting the GNSS synchronization source for resynchronization.
  • the another synchronization source comprises one of a Serving Cell, a Primary Cell, or a second UE.
  • the threshold period of time comprises one or more seconds.
  • the second circuitry 820 may be operable to receive reference signals from one or more satellites associated with the GNSS; estimate a reliability of the GNSS as a synchronization source, based on the reference signals; and evaluate the GNSS synchronization source, based on the reliability of the GNSS as a synchronization source.
  • the second circuitry 820 may be operable to estimate a first GNSS quality metric, based on the reference signals; compare the first GNSS quality metric to a first threshold metric; and estimate the reliability of the GNSS as the synchronization source, based on the comparing.
  • the first GNSS quality metric is associated with a timing accuracy of the reference signals. In some embodiments, the first threshold metric is 12 * Ts, where Ts is about 1/(15000x2048) seconds. In some embodiments, the first GNSS quality metric is associated with a frequency accuracy of the reference signal.
  • first circuitry 810, second circuitry 820, and/or third circuitry 830 may be implemented as separate circuitries. In other embodiments, first circuitry 810, second circuitry 820, and third circuitry 830 may be combined and
  • Fig. 9 illustrates a method 900 for a UE to initiate an interruption while changing a synchronization reference source of the UE, according to some embodiments.
  • the method 900 that may relate to UE 630 and hardware processing circuitry 640 are discussed below.
  • the actions in the method of Fig. 9 are shown in a particular order, the order of the actions can be modified. Thus, the illustrated
  • embodiments can be performed in a different order, and some actions may be performed in parallel. Some of the actions and/or operations listed in Fig. 9 are optional in accordance with certain embodiments. The numbering of the actions presented is for the sake of clarity and is not intended to prescribe an order of operations in which the various actions must occur. Additionally, operations from the various flows may be utilized in a variety of combinations.
  • machine readable storage media may have executable instructions that, when executed, cause UE 630 and/or hardware processing circuitry 640 to perform an operation comprising the method of Fig. 9.
  • Such machine readable storage media may include any of a variety of storage media, like magnetic storage media (e.g., magnetic tapes or magnetic disks), optical storage media (e.g., optical discs), electronic storage media (e.g., conventional hard disk drives, solid-state disk drives, or flash- memory-based storage media), or any other tangible storage media or non-transitory storage media.
  • an apparatus may comprise means for performing various actions and/or operations of the method 900 of Fig. 9.
  • the method 900 may be in accordance with the various embodiments discussed herein.
  • the method 900 may comprise, at 904, determining to change a synchronization reference source of a UE from a first synchronization source to a second synchronization source.
  • one of the first synchronization source or the second synchronization source may be a GNSS synchronization source.
  • an interruption of at least one of a signal transmission of the UE or a signal reception of the UE may be initiated for an interruption period.
  • the synchronization reference source of the UE may be changed from the first synchronization source to the second
  • the interruption period may comprise up to one subframe. In some embodiments, the interruption period may comprise one or more subframes. In some embodiments, to perform the interruption, the method may comprise performing the interruption of one or more of PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink Synchronization Signals) signals. In some embodiments, to perform the interruption, the method may comprise performing the interruption of sidelink signals transmitted between the UE and a second UE. In some embodiments, to perform the interruption, the method may comprise performing the interruption of V2V (Vehicle-to-Vehicle) sidelink signals.
  • PSSCH Physical Sidelink Shared Channel
  • PSCCH Physical Sidelink Control Channel
  • PSBCH Physical Sidelink Broadcast Channel
  • SLSS Segment Link Synchronization Signals
  • the method may comprise performing the interruption to align with a boundary of at least one of a transmission subframe or a reception subframe. In some embodiments, to perform the interruption, the method may comprise performing the interruption during a last symbol of a V2V (Vehicle-to-Vehicle) subframe. In some embodiments, the method may comprise utilizing the synchronization reference source for time synchronization and/or frequency synchronization of one or more sidelink channels of the UE. In some embodiments, the method may comprise generating a signal for
  • another one of the first synchronization source or the second synchronization source is one of a Serving Cell, a Primary Cell, or a second UE.
  • Fig. 10 illustrates a method 1000 for a UE to evaluate a GNSS
  • a synchronization source for at least a threshold period of time, before selecting another synchronization source or before resecting the GNSS synchronization source for resynchronization, according to some embodiments.
  • the method 1000 that may relate to UE 630 and hardware processing circuitry 640 are discussed below.
  • the actions in the method of Fig. 10 are shown in a particular order, the order of the actions can be modified. Thus, the illustrated embodiments can be performed in a different order, and some actions may be performed in parallel. Some of the actions and/or operations listed in Fig. 10 are optional in accordance with certain embodiments. The numbering of the actions presented is for the sake of clarity and is not intended to prescribe an order of operations in which the various actions must occur. Additionally, operations from the various flows may be utilized in a variety of combinations.
  • machine readable storage media may have executable instructions that, when executed, cause UE 630 and/or hardware processing circuitry 640 to perform an operation comprising the method of Fig. 10.
  • Such machine readable storage media may include any of a variety of storage media, like magnetic storage media (e.g., magnetic tapes or magnetic disks), optical storage media (e.g., optical discs), electronic storage media (e.g., conventional hard disk drives, solid-state disk drives, or flash- memory-based storage media), or any other tangible storage media or non-transitory storage media.
  • an apparatus may comprise means for performing various actions and/or operations of the method 1000 of Fig. 910.
  • the method 1000 may be in accordance with the various embodiments discussed herein.
  • the method 1000 may comprise, at 1004, synchronizing, to a GNSS synchronization source and at a first time, at least one of a timing or a frequency associated with one or more sidelink channels of the UE.
  • the GNSS may be synchronizing, to a GNSS synchronization source and at a first time, at least one of a timing or a frequency associated with one or more sidelink channels of the UE.
  • synchronization source may be evaluated for at least a threshold period of time from the first time, before selecting another synchronization source or before resecting the GNSS synchronization source for resynchronization.
  • a memory of the UE may store an identification or an indication of the threshold period of time (e.g., store a duration of the threshold period of time).
  • the another synchronization source may comprise one of a Serving Cell, a Primary Cell, or a second UE.
  • the threshold period of time may comprise one or more seconds.
  • the method may comprise receiving reference signals from one or more satellites associated with the GNSS; estimating a reliability of the GNSS as a synchronization source, based on the reference signals; and evaluating the GNSS synchronization source, based on the reliability of the GNSS as a synchronization source.
  • the method may comprise estimating a first GNSS quality metric, based on the reference signals; comparing the first GNSS quality metric to a first threshold metric; and estimating the reliability of the GNSS as the synchronization source, based on the comparing.
  • the first GNSS quality metric may be associated with a timing accuracy of the reference signals.
  • the first threshold metric may be 12 * Ts, where Ts is a system sampling time.
  • the first GNSS quality metric may be associated with a frequency accuracy of the reference signal.
  • Fig. 11 illustrates an architecture of a system 1100 of a network in accordance with some embodiments.
  • the system 1100 is shown to include a user equipment (UE) 1101 and a UE 1102.
  • the UEs 1101 and 1102 are illustrated as smartphones (e.g., handheld touchscreen mobile computing devices connectable to one or more cellular networks), but may also comprise any mobile or non-mobile computing device, such as Personal Data Assistants (PDAs), pagers, laptop computers, desktop computers, wireless handsets, or any computing device including a wireless communications interface.
  • PDAs Personal Data Assistants
  • pagers pagers
  • laptop computers desktop computers
  • wireless handsets wireless handsets
  • any of the UEs 1101 and 1102 can comprise an Internet of Things (IoT) UE, which can comprise a network access layer designed for low-power IoT applications utilizing short-lived UE connections.
  • An IoT UE can utilize technologies such as machine-to-machine (M2M) or machine-type communications (MTC) for exchanging data with an MTC server or device via a public land mobile network (PLMN), Proximity -Based Service (ProSe) or device-to-device (D2D) communication, sensor networks, or IoT networks.
  • M2M or MTC exchange of data may be a machine-initiated exchange of data.
  • An IoT network describes interconnecting IoT UEs, which may include uniquely identifiable embedded computing devices (within the Internet infrastructure), with short-lived
  • the IoT UEs may execute background applications (e.g., keep-alive messages, status updates, etc.) to facilitate the connections of the IoT network.
  • background applications e.g., keep-alive messages, status updates, etc.
  • the UEs 1101 and 1102 may be configured to connect, e.g., communicatively couple, with a radio access network (RAN)— in this embodiment, an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) 1110.
  • RAN radio access network
  • E-UTRAN Evolved Universal Mobile Telecommunications System
  • the UEs 1101 and 1102 utilize connections 1103 and 1104, respectively, each of which comprises a physical communications interface or layer (discussed in further detail below); in this example, the connections 1103 and 1104 are illustrated as an air interface to enable communicative coupling, and can be consistent with cellular communications protocols, such as a Global System for Mobile Communications (GSM) protocol, a code- division multiple access (CDMA) network protocol, a Push-to-Talk (PTT) protocol, a PTT over Cellular (POC) protocol, a Universal Mobile Telecommunications System (UMTS) protocol, a 3GPP Long Term Evolution (LTE) protocol, a fifth generation (5G) protocol, a New Radio (NR) protocol, and the like.
  • GSM Global System for Mobile Communications
  • CDMA code- division multiple access
  • PTT Push-to-Talk
  • POC PTT over Cellular
  • UMTS Universal Mobile Telecommunications System
  • LTE Long Term Evolution
  • 5G fifth generation
  • NR New Radio
  • the UEs 1101 and 1102 may further directly exchange communication data via a ProSe interface 1105.
  • the ProSe interface 1105 may alternatively be referred to as a sidelink interface comprising one or more logical channels, including but not limited to a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Discovery Channel (PSDCH), and a Physical Sidelink Broadcast Channel (PSBCH).
  • PSCCH Physical Sidelink Control Channel
  • PSSCH Physical Sidelink Shared Channel
  • PSDCH Physical Sidelink Discovery Channel
  • PSBCH Physical Sidelink Broadcast Channel
  • both ProSe and V2V interface of a UE may use sidelink physical channels, such as PSSCH, PSCCH, PSBCH, etc.
  • the UE 1102 is shown to be configured to access an access point (AP) 1106 via connection 1107.
  • the connection 1107 can comprise a local wireless connection, such as a connection consistent with any IEEE 802.11 protocol, wherein the AP 1106 would comprise a wireless fidelity (WiFi®) router.
  • WiFi® wireless fidelity
  • the AP 1106 is shown to be connected to the Internet without connecting to the core network of the wireless system (described in further detail below).
  • the E-UTRAN 1110 can include one or more access nodes that enable the connections 1103 and 1104.
  • These access nodes can be referred to as base stations (BSs), NodeBs, evolved NodeBs (eNBs), next Generation NodeBs (gNB), RAN nodes, and so forth, and can comprise ground stations (e.g., terrestrial access points) or satellite stations providing coverage within a geographic area (e.g., a cell).
  • BSs base stations
  • eNBs evolved NodeBs
  • gNB next Generation NodeBs
  • RAN nodes and so forth, and can comprise ground stations (e.g., terrestrial access points) or satellite stations providing coverage within a geographic area (e.g., a cell).
  • the E-UTRAN 1110 may include one or more RAN nodes for providing macrocells, e.g., macro RAN node 1111, and one or more RAN nodes for providing femtocells or picocells (e.g., cells having smaller coverage areas, smaller user capacity, or higher bandwidth compared to macrocells), e.g., low power (LP) RAN node 1112.
  • macro RAN node 1111 e.g., macro RAN node 1111
  • femtocells or picocells e.g., cells having smaller coverage areas, smaller user capacity, or higher bandwidth compared to macrocells
  • LP low power
  • any of the RAN nodes 1111 and 1112 can terminate the air interface protocol and can be the first point of contact for the UEs 1101 and 1102.
  • any of the RAN nodes 1111 and 1112 can fulfill various logical functions for the E-UTRAN 1110 including, but not limited to, radio network controller (RNC) functions such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management.
  • RNC radio network controller
  • the UEs 1101 and 1102 can be configured to communicate using Orthogonal Frequency-Division Multiplexing (OFDM) based communication signals with each other or with any of the RAN nodes 1111 and 1112 over a multicarrier communication channel in accordance various communication techniques, such as, but not limited to, an Orthogonal Frequency-Division Multiple Access (OFDMA) communication technique (e.g., for downlink communications) or a Single Carrier Frequency Division Multiple Access (SC-FDMA) communication technique (e.g., for uplink, ProSe, sidelink communications, V2V communications, etc.), although the scope of the OFDM OFDM (OFDMA) communication technique (e.g., for downlink communications) or a Single Carrier Frequency Division Multiple Access (SC-FDMA) communication technique (e.g., for uplink, ProSe, sidelink communications, V2V communications, etc.), although the scope of the OFDM OFDM (OFDMA) communication technique (e.g., for downlink communications)
  • the OFDM signals can comprise a plurality of orthogonal subcarriers.
  • a downlink resource grid can be used for downlink transmissions from any of the RAN nodes 1111 and 1112 to the UEs 1101 and 1102, while uplink transmissions can utilize similar techniques.
  • the grid can be a time-frequency grid, called a resource grid or time-frequency resource grid, which is the physical resource in the downlink in each slot.
  • a time-frequency plane representation is a common practice for OFDM systems, which makes it intuitive for radio resource allocation.
  • Each column and each row of the resource grid corresponds to one OFDM symbol and one OFDM subcarrier, respectively.
  • the duration of the resource grid in the time domain corresponds to one slot in a radio frame.
  • the smallest time-frequency unit in a resource grid is denoted as a resource element.
  • Each resource grid comprises a number of resource blocks, which describe the mapping of certain physical channels to resource elements.
  • Each resource block comprises a collection of resource elements; in the frequency domain, this may represent the smallest quantity of resources that currently can be allocated.
  • the physical downlink shared channel may carry user data and higher-layer signaling to the UEs 1101 and 1102.
  • the physical downlink control channel (PDCCH) may carry information about the transport format and resource allocations related to the PDSCH channel, among other things. It may also inform the UEs 1101 and 1102 about the transport format, resource allocation, and H-ARQ (Hybrid Automatic Repeat Request) information related to the uplink shared channel.
  • downlink scheduling assigning control and shared channel resource blocks to the UE 1102 within a cell
  • the downlink resource assignment information may be sent on the PDCCH used for (e.g., assigned to) each of the UEs 1101 and 1102.
  • the PDCCH may use control channel elements (CCEs) to convey the control information.
  • CCEs control channel elements
  • the PDCCH complex-valued symbols may first be organized into quadruplets, which may then be permuted using a sub- block interleaver for rate matching.
  • Each PDCCH may be transmitted using one or more of these CCEs, where each CCE may correspond to nine sets of four physical resource elements known as resource element groups (REGs).
  • Four Quadrature Phase Shift Keying (QPSK) symbols may be mapped to each REG.
  • QPSK Quadrature Phase Shift Keying
  • the PDCCH can be transmitted using one or more CCEs, depending on the size of the downlink control information (DCI) and the channel condition.
  • DCI downlink control information
  • There can be four or more different PDCCH formats defined in LTE with different numbers of CCEs (e.g., aggregation level, L l, 2, 4, or 8).
  • Some embodiments may use concepts for resource allocation for control channel information that are an extension of the above-described concepts.
  • some embodiments may utilize an enhanced physical downlink control channel (EPDCCH) that uses PDSCH resources for control information transmission.
  • the EPDCCH may be transmitted using one or more enhanced the control channel elements (ECCEs). Similar to above, each ECCE may correspond to nine sets of four physical resource elements known as an enhanced resource element groups (EREGs). An ECCE may have other numbers of EREGs in some situations.
  • EPCCH enhanced physical downlink control channel
  • ECCEs enhanced the control channel elements
  • each ECCE may correspond to nine sets of four physical resource elements known as an enhanced resource element groups (EREGs).
  • EREGs enhanced resource element groups
  • An ECCE may have other numbers of EREGs in some situations.
  • a sidelink resource grid may be used for sidelink transmissions between the UEs 1101 and 1102.
  • the grid may be a time-frequency grid, called a resource grid or time-frequency resource grid, which may be the physical resource in the sidelink in each slot.
  • a time-frequency plane representation may be used in OFDM systems, which may make it intuitive for radio resource allocation.
  • Each column and each row of the resource grid corresponds to one OFDM (SC-FDMA) symbol and one OFDM (SC-FDMA) subcarrier, respectively.
  • the duration of the resource grid in the time domain may correspond to one slot in a radio frame.
  • the smallest time-frequency unit in a resource grid may be denoted as a resource element.
  • Each resource grid may comprise a number of resource blocks, which may describe the mapping of certain physical channels to resource elements.
  • Each resource block comprises a collection of resource elements; in the frequency domain, this may represent the smallest quantity of resources that currently can be allocated.
  • the physical sidelink shared channel may carry user data between different UEs.
  • the physical sidelink control channel may carry information about the transport format and resource allocations related to the PSSCH channel, among other things. It may also inform the UEs 1101 and 1102 about the transport format, resource allocation, etc.
  • the E-UTRAN 1110 is shown to be communicatively coupled to a core network— in this embodiment, an Evolved Packet Core (EPC) network 1120 via an S I interface 1113.
  • EPC Evolved Packet Core
  • the SI interface 1113 is split into two parts: the S l-U interface 1114, which carries traffic data between the RAN nodes 1111 and 1112 and the serving gateway (S-GW) 1122, and the SI -mobility management entity (MME) interface 1115, which is a signaling interface between the RAN nodes 1111 and 1112 and MMEs 1121.
  • S-GW serving gateway
  • MME SI -mobility management entity
  • the EPC network 1120 comprises the MMEs 1121, the S-
  • the MMEs 1121 may be similar in function to the control plane of legacy Serving General Packet Radio Service (GPRS) Support Nodes (SGSN).
  • the MMEs 1121 may manage mobility aspects in access such as gateway selection and tracking area list management.
  • the HSS 1124 may comprise a database for network users, including subscription-related information to support the network entities' handling of communication sessions.
  • the EPC network 1120 may comprise one or several HSSs 1124, depending on the number of mobile subscribers, on the capacity of the equipment, on the organization of the network, etc.
  • the HSS 1124 can provide support for routing/roaming, authentication, authorization, naming/addressing resolution, location dependencies, etc.
  • the S-GW 1122 may terminate the SI interface 1113 towards the E-UTRAN
  • the S-GW 1122 may be a local mobility anchor point for inter-RAN node handovers and also may provide an anchor for inter-3GPP mobility. Other responsibilities may include lawful intercept, charging, and some policy enforcement.
  • the P-GW 1123 may terminate an SGi interface toward a PDN.
  • the P-GW 1123 may terminate an SGi interface toward a PDN.
  • the 1123 may route data packets between the EPC network 1120 and extemal networks such as a network including the application server 1130 (alternatively referred to as application function (AF)) via an Internet Protocol (IP) interface 1125.
  • the application server 1130 may be an element offering applications that use IP bearer resources with the core network (e.g., UMTS Packet Services (PS) domain, LTE PS data services, etc.).
  • PS Packet Services
  • LTE PS data services etc.
  • the P-GW 1123 is shown to be communicatively coupled to an application server 1130 via an IP communications interface 1125.
  • the application server 1130 can also be configured to support one or more communication services (e.g., Voice-over-Internet Protocol (VoIP) sessions, PTT sessions, group communication sessions, social networking services, etc.) for the UEs 1101 and 1102 via the EPC network 1120.
  • VoIP Voice-over-Internet Protocol
  • PTT sessions PTT sessions
  • group communication sessions social networking services, etc.
  • the P-GW 1123 may further be a node for policy enforcement and charging data collection.
  • Policy and Charging Enforcement Function (PCRF) 1126 is the policy and charging control element of the EPC network 1120.
  • PCRF Policy and Charging Enforcement Function
  • HPLMN Home Public Land Mobile Network
  • IP-CAN Internet Protocol Connectivity Access Network
  • HPLMN Home Public Land Mobile Network
  • V-PCRF Visited PCRF
  • VPLMN Visited Public Land Mobile Network
  • the PCRF 1126 may be communicatively coupled to the application server 1130 via the P-GW 1123.
  • the application server 1130 may signal the PCRF 1126 to indicate a new service flow and select the appropriate Quality of Service (QoS) and charging parameters.
  • the PCRF 1126 may provision this rule into a Policy and Charging Enforcement Function (PCEF) (not shown) with the appropriate traffic flow template (TFT) and QoS class of identifier (QCI), which commences the QoS and charging as specified by the application server 1130.
  • PCEF Policy and Charging Enforcement Function
  • TFT traffic flow template
  • QCI QoS class of identifier
  • Fig. 12 illustrates example components of a device 1200 in accordance with some embodiments.
  • the device 1200 may include application circuitry 1202, baseband circuitry 1204, Radio Frequency (RF) circuitry 1206, front-end module (FEM) circuitry 1208, one or more antennas 1210, and power management circuitry (PMC) 1212 coupled together at least as shown.
  • the components of the illustrated device 1200 may be included in a UE or a RAN node.
  • the device 1200 may include less elements (e.g., a RAN node may not utilize application circuitry 1202, and instead include a processor/controller to process IP data received from an EPC).
  • the device 1200 may include additional elements such as, for example, memory /storage, display, camera, sensor, or input/output (I/O) interface.
  • additional elements such as, for example, memory /storage, display, camera, sensor, or input/output (I/O) interface.
  • the components described below may be included in more than one device (e.g., said circuitries may be separately included in more than one device for Cloud-RAN (C- RAN) implementations).
  • C- RAN Cloud-RAN
  • the application circuitry 1202 may include one or more application processors.
  • the application circuitry 1202 may include circuitry such as, but not limited to, one or more single-core or multi-core processors.
  • the processor(s) may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.).
  • the processors may be coupled with or may include memory /storage and may be configured to execute instructions stored in the memory /storage to enable various applications or operating systems to run on the device 1200.
  • processors of application circuitry 1202 may process IP data packets received from an EPC.
  • the baseband circuitry 1204 may include circuitry such as, but not limited to, one or more single-core or multi-core processors.
  • the baseband circuitry 1204 may include one or more baseband processors or control logic to process baseband signals received from a receive signal path of the RF circuitry 1206 and to generate baseband signals for a transmit signal path of the RF circuitry 1206.
  • Baseband processing circuity 1204 may interface with the application circuitry 1202 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 1206.
  • the baseband circuitry 1204 may include a third generation (3G) baseband processor 1204A, a fourth generation (4G) baseband processor 1204B, a fifth generation (5G) baseband processor 1204C, or other baseband processor(s) 1204D for other existing generations, generations in development or to be developed in the future (e.g., second generation (2G), sixth generation (6G), etc.).
  • the baseband circuitry 1204 e.g., one or more of baseband processors 1204A-D
  • baseband processors 1204A-D may be included in modules stored in the memory 1204G and executed via a Central Processing Unit (CPU) 1204E.
  • the radio control functions may include, but are not limited to, signal modulation/demodulation,
  • modulation/demodulation circuitry of the baseband circuitry 1204 may include Fast-Fourier Transform (FFT), precoding, or constellation mapping/demapping functionality.
  • FFT Fast-Fourier Transform
  • encoding/decoding circuitry of the baseband circuitry 1204 may include convolution, tail-biting convolution, turbo, Viterbi, or Low Density Parity Check (LDPC) encoder/decoder functionality.
  • LDPC Low Density Parity Check
  • encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other embodiments.
  • the baseband circuitry 1204 may include one or more audio digital signal processor(s) (DSP) 1204F.
  • the audio DSP(s) 1204F may be include elements for compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments.
  • Components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some embodiments.
  • some or all of the constituent components of the baseband circuitry 1204 and the application circuitry 1202 may be implemented together such as, for example, on a system on a chip (SOC).
  • SOC system on a chip
  • the baseband circuitry 1204 may provide for communication compatible with one or more radio technologies.
  • the baseband circuitry 1204 may support communication with an evolved universal terrestrial radio access network (EUTRAN) or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN).
  • EUTRAN evolved universal terrestrial radio access network
  • WMAN wireless metropolitan area networks
  • WLAN wireless local area network
  • WPAN wireless personal area network
  • Embodiments in which the baseband circuitry 1204 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry.
  • RF circuitry 1206 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium.
  • the RF circuitry 1206 may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network.
  • RF circuitry 1206 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 1208 and provide baseband signals to the baseband circuitry 1204.
  • RF circuitry 1206 may also include a transmit signal path which may include circuitry to up-convert baseband signals provided by the baseband circuitry 1204 and provide RF output signals to the FEM circuitry 1208 for transmission.
  • the receive signal path of the RF circuitry 1206 may include mixer circuitry 1206a, amplifier circuitry 1206b and filter circuitry 1206c.
  • the transmit signal path of the RF circuitry 1206 may include filter circuitry 1206c and mixer circuitry 1206a.
  • RF circuitry 1206 may also include synthesizer circuitry 1206d for synthesizing a frequency for use by the mixer circuitry 1206a of the receive signal path and the transmit signal path.
  • the mixer circuitry 1206a of the receive signal path may be configured to down-convert RF signals received from the FEM circuitry 1208 based on the synthesized frequency provided by synthesizer circuitry 1206d.
  • the amplifier circuitry 1206b may be configured to amplify the down-converted signals and the filter circuitry 1206c may be a low-pass filter (LPF) or band-pass filter (BPF) configured to remove unwanted signals from the down-converted signals to generate output baseband signals.
  • Output baseband signals may be provided to the baseband circuitry 1204 for further processing.
  • the output baseband signals may be zero-frequency baseband signals, although this is not a requirement.
  • mixer circuitry 1206a of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect.
  • the mixer circuitry 1206a of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 1206d to generate RF output signals for the FEM circuitry 1208.
  • the baseband signals may be provided by the baseband circuitry 1204 and may be filtered by filter circuitry 1206c.
  • the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a of the transmit signal path may include two or more mixers and may be arranged for quadrature downconversion and upconversion, respectively.
  • the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection).
  • the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a may be arranged for direct downconversion and direct upconversion, respectively.
  • the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a of the transmit signal path may be configured for super-heterodyne operation.
  • the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect.
  • the output baseband signals and the input baseband signals may be digital baseband signals.
  • the RF circuitry 1206 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry 1204 may include a digital baseband interface to communicate with the RF circuitry 1206.
  • ADC analog-to-digital converter
  • DAC digital-to-analog converter
  • a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect.
  • the synthesizer circuitry 1206d may be a fractional -N synthesizer or a fractional N/N+l synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable.
  • synthesizer circuitry 1206d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider.
  • the synthesizer circuitry 1206d may be configured to synthesize an output frequency for use by the mixer circuitry 1206a of the RF circuitry 1206 based on a frequency input and a divider control input.
  • the synthesizer circuitry 1206d may be a fractional N/N+l synthesizer.
  • frequency input may be provided by a voltage controlled oscillator (VCO), although that is not a requirement.
  • VCO voltage controlled oscillator
  • Divider control input may be provided by either the baseband circuitry 1204 or the applications processor 1202 depending on the desired output frequency.
  • a divider control input (e.g., N) may be determined from a look-up table based on a channel indicated by the applications processor 1202.
  • Synthesizer circuitry 1206d of the RF circuitry 1206 may include a divider, a delay-locked loop (DLL), a multiplexer and a phase accumulator.
  • the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DP A).
  • the DMD may be configured to divide the input signal by either N or N+l (e.g., based on a carry out) to provide a fractional division ratio.
  • the DLL may include a set of cascaded, tunable, delay elements, a phase detector, a charge pump and a D-type flip-flop.
  • the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line.
  • Nd is the number of delay elements in the delay line.
  • synthesizer circuitry 1206d may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other.
  • the output frequency may be a LO frequency (fLO).
  • the RF circuitry 1206 may include an IQ/polar converter.
  • FEM circuitry 1208 may include a receive signal path which may include circuitry configured to operate on RF signals received from one or more antennas 1210, amplify the received signals and provide the amplified versions of the received signals to the RF circuitry 1206 for further processing.
  • FEM circuitry 1208 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 1206 for transmission by one or more of the one or more antennas 1210.
  • the amplification through the transmit or receive signal paths may be done solely in the RF circuitry 1206, solely in the FEM 1208, or in both the RF circuitry 1206 and the FEM 1208.
  • the FEM circuitry 1208 may include a TX/RX switch to switch between transmit mode and receive mode operation.
  • the FEM circuitry may include a receive signal path and a transmit signal path.
  • the receive signal path of the FEM circuitry may include an LNA to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 1206).
  • the transmit signal path of the FEM circuitry 1208 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry 1206), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 1210).
  • PA power amplifier
  • the PMC 1212 may manage power provided to the baseband circuitry 1204.
  • the PMC 1212 may control power-source selection, voltage scaling, battery charging, or DC-to-DC conversion.
  • the PMC 1212 may often be included when the device 1200 is capable of being powered by a battery, for example, when the device is included in a UE.
  • the PMC 1212 may increase the power conversion efficiency while providing desirable implementation size and heat dissipation characteristics.
  • Fig. 12 shows the PMC 1212 coupled only with the baseband circuitry 1204.
  • the PMC 1212 may be additionally or alternatively coupled with, and perform similar power management operations for, other components such as, but not limited to, application circuitry 1202, RF circuitry 1206, or FEM 1208.
  • Processors of the application circuitry 1202 and processors of the baseband circuitry 1204 may be used to execute elements of one or more instances of a protocol stack.
  • processors of the baseband circuitry 1204 alone or in combination, may be used execute Layer 3, Layer 2, or Layer 1 functionality, while processors of the application circuitry 1204 may utilize data (e.g., packet data) received from these layers and further execute Layer 4 functionality (e.g., transmission communication protocol (TCP) and user datagram protocol (UDP) layers).
  • Layer 3 may comprise a radio resource control (RRC) layer, described in further detail below.
  • RRC radio resource control
  • Layer 2 may comprise a medium access control (MAC) layer, a radio link control (RLC) layer, and a packet data convergence protocol (PDCP) layer, described in further detail below.
  • Layer 1 may comprise a physical (PHY) layer of a UE/RAN node, described in further detail below.
  • Fig. 13 illustrates example interfaces of baseband circuitry in accordance with some embodiments.
  • the baseband circuitry 1204 of Fig. 12 may comprise processors 1204A-1204E and a memory 1204G utilized by said processors.
  • Each of the processors 1204A-1204E may include a memory interface, 1304A-1304E, respectively, to send/receive data to/from the memory 1204G.
  • the baseband circuitry 1204 may further include one or more interfaces to communicatively couple to other circuitries/devices, such as a memory interface 1312 (e.g., an interface to send/receive data to/from memory extemal to the baseband circuitry 1204), an application circuitry interface 1314 (e.g., an interface to send/receive data to/from the application circuitry 1202 of Fig. 12), an RF circuitry interface 1316 (e.g., an interface to send/receive data to/from RF circuitry 1206 of Fig.
  • a memory interface 1312 e.g., an interface to send/receive data to/from memory extemal to the baseband circuitry 1204
  • an application circuitry interface 1314 e.g., an interface to send/receive data to/from the application circuitry 1202 of Fig. 12
  • an RF circuitry interface 1316 e.g., an interface to send/receive data to/from RF circuitry 1206 of
  • a wireless hardware connectivity interface 1318 e.g., an interface to send/receive data to/from Near Field Communication (NFC) components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components
  • a power management interface 1320 e.g., an interface to send/receive power or control signals to/from the PMC 1212.
  • DRAM Dynamic RAM
  • Example 1 An apparatus of a User Equipment (UE) operable to communicate with an Evolved Node B (eNB) on a wireless network, comprising: a memory to store instructions; and one or more processors to execute the stored instructions to perform:
  • UE User Equipment
  • eNB Evolved Node B
  • a synchronization reference source of the UE determines that a synchronization reference source of the UE is to be changed from a first synchronization source to a second synchronization source, wherein one of the first synchronization source or the second synchronization source is a Global Navigation Satellite System (GNSS) synchronization source; initiate an interruption for an interruption period of at least one of a signal transmission of the UE or a signal reception of the UE; and change the synchronization reference source of the UE from the first synchronization source to the second synchronization source, during the interruption for the interruption period.
  • GNSS Global Navigation Satellite System
  • Example 2 The apparatus of example 1 or some other example herein, wherein the interruption period comprises up to one subframe.
  • Example 3 The apparatus of example 1 or some other example herein, wherein the interruption period comprises one or more subframes.
  • Example 4 The apparatus of any of examples 1-3 or some other example herein, wherein to initiate the interruption, the one or more processors are to: initiate the interruption of transmission or reception of one or more of: PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink Synchronization Signals) signals.
  • PSSCH Physical Sidelink Shared Channel
  • PSCCH Physical Sidelink Control Channel
  • PSBCH Physical Sidelink Broadcast Channel
  • SLSS Segment Link Synchronization Signals
  • Example 5 The apparatus of any of examples 1-4 or some other example herein, wherein the UE is a first UE, and wherein to initiate the interruption, the one or more processors are to: initiate the interruption of transmission or reception of sidelink signals transmitted between the first UE and a second UE.
  • Example 6 The apparatus of any of examples 1-5 or some other example herein, wherein to initiate the interruption, the one or more processors are to: initiate the interruption of transmission or reception of V2V (Vehicle-to-Vehicle) sidelink signals.
  • V2V Vehicle-to-Vehicle
  • Example 7 The apparatus of any of examples 1-6 or some other example herein, wherein to initiate the interruption, the one or more processors are to: initiate the interruption of transmission or reception to align with a boundary of at least one of: a transmission subframe, or a reception subframe.
  • Example 8 The apparatus of any of examples 1-7 or some other example herein, wherein to initiate the interruption, the one or more processors are to: initiate the interruption of transmission or reception during a last symbol of a V2V (Vehicle-to-Vehicle) subframe.
  • V2V Vehicle-to-Vehicle
  • Example 9 The apparatus of any of examples 1-8 or some other example herein, wherein the one or more processors are to: utilize the synchronization reference source for at least one of: a time synchronization for transmission or reception of one or more sidelink physical channels of the UE, or a frequency synchronization for transmission or reception of one or more sidelink physical channels of the UE.
  • Example 10 The apparatus of any of examples 1-9 or some other example herein, wherein the one or more processors are to: generate, for transmission to the eNB, a signal to inform the eNB about the interruption of transmission or reception.
  • Example 11 The apparatus of any of examples 1-10 or some other example herein, wherein one of the first synchronization source or the second synchronization source is one of: a Serving Cell, a Primary Cell, or a second UE.
  • Example 12 The apparatus of any of examples 1 to 11 or some other example herein, comprising a transceiver circuitry for generating transmissions and processing transmissions.
  • Example 13 A User Equipment (UE) device comprising an application processor, a memory, one or more antennas, a wireless interface for allowing the application processor to communicate with another device, and a touch-screen display, the UE device including the apparatus of any of examples 1 to 12 or some other example herein.
  • UE User Equipment
  • Example 14 Machine readable storage media having machine executable instructions that, when executed, cause one or more processors of a User Equipment (UE) to perform an operation comprising: determine that a synchronization reference source of the UE is to be changed from a first synchronization source to a second synchronization source, wherein one of the first synchronization source or the second synchronization source is a Global Navigation Satellite System (GNSS) synchronization source; initiate an interruption for an interruption period of at least one of a signal transmission of the UE or a signal reception of the UE; and change the synchronization reference source of the UE from the first synchronization source to the second synchronization source, during the interruption for the interruption period.
  • GNSS Global Navigation Satellite System
  • Example 15 The machine readable storage media of example 14 or some other example herein, wherein the interruption period comprises up to one subframe.
  • Example 16 The machine readable storage media of example 14 or some other example herein, wherein the interruption period comprises one or more subframes.
  • Example 17 The machine readable storage media of any of examples 14-16 or some other example herein, wherein to initiate the interruption, the operation comprises: initiate the interruption of transmission or reception of one or more of: PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink Synchronization Signals) signals.
  • PSSCH Physical Sidelink Shared Channel
  • PSCCH Physical Sidelink Control Channel
  • PSBCH Physical Sidelink Broadcast Channel
  • SLSS Segment Link Synchronization Signals
  • Example 18 The machine readable storage media of any of examples 14-17 or some other example herein, wherein the UE is a first UE, and wherein to initiate the interruption, the operation comprises: initiate the interruption of transmission or reception of sidelink signals transmitted between the first UE and a second UE.
  • Example 19 The machine readable storage media of any of examples 14-18 or some other example herein, wherein to initiate the interruption, the operation comprises: initiate the interruption of transmission or reception of V2V (Vehicle-to-Vehicle) sidelink signals.
  • V2V Vehicle-to-Vehicle
  • Example 20 The machine readable storage media of any of examples 14-19 or some other example herein, wherein to initiate the interruption, the operation comprises: initiate the interruption of transmission or reception of one or more sidelink signals of the UE.
  • Example 21 The machine readable storage media of any of examples 14-20 or some other example herein, wherein to perform the interruption, the operation comprises: initiate the interruption of transmission or reception to align with a boundary of at least one: of a transmission subframe, or a reception subframe.
  • Example 22 The machine readable storage media of any of examples 14-21 or some other example herein, wherein to initiate the interruption, the operation comprises: initiate the interruption of transmission or reception during a last symbol of a V2V (Vehicle- to-Vehicle) subframe.
  • V2V Vehicle- to-Vehicle
  • Example 23 The machine readable storage media of any of examples 14-22 or some other example herein, the operation comprising: utilize the synchronization reference source for at least one of: a time synchronization of one or more sidelink physical channels of the UE, or a frequency synchronization of one or more sidelink physical channels of the UE.
  • Example 24 The machine readable storage media of any of examples 14-23 or some other example herein, the operation comprising: generate, for transmission to the eNB, a signal to inform the eNB about the interruption.
  • Example 25 The machine readable storage media of any of examples 14-24 or some other example herein, wherein one of the first synchronization source or the second synchronization source is one of: a Serving Cell, a Primary Cell, or a second UE.
  • Example 26 An apparatus of a User Equipment (UE) operable to
  • eNB Evolved Node B
  • eNB Evolved Node B
  • eNB Evolved Node B
  • processors to: synchronize, to a Global Navigation Satellite System (GNSS) synchronization source and at a first time, at least one of: a timing associated with one or more sidelink channels of the UE, or a frequency associated with one or more sidelink channels of the UE, and evaluate the GNSS synchronization source for at least a threshold period of time from the first time, before selecting another synchronization source or before reselecting the GNSS synchronization source for synchronization; and a memory to store an indication of the threshold period of time.
  • GNSS Global Navigation Satellite System
  • Example 27 The apparatus of example 26 or some other example herein, wherein the another synchronization source comprises one of: a Serving Cell, a Primary Cell, or a second UE.
  • Example 28 The apparatus of any of examples 26-27 or some other example herein, wherein the threshold period of time comprises one or more seconds.
  • Example 29 The apparatus of any of examples 26-28 or some other example herein, wherein to evaluate the GNSS synchronization source, the one or more processors are to: process one or more signals received from one or more satellites associated with the GNSS synchronization source; estimate a reliability of the GNSS as a synchronization source, based on the one or more reference signals; and evaluate the GNSS synchronization source, based on the reliability of the GNSS as a synchronization source.
  • Example 30 The apparatus of example 29 or some other example herein, wherein to estimate the reliability of the GNSS as the synchronization source, the one or more processors are to: estimate a first GNSS quality metric, based on the one or more reference signals; compare the first GNSS quality metric to a first threshold metric; and estimate the reliability of the GNSS as the synchronization source, based on the comparison of the first GNSS quality metric to the first threshold metric.
  • Example 31 The apparatus of example 30 or some other example herein, wherein the first GNSS quality metric is associated with a timing accuracy of the reference signals.
  • Example 32 The apparatus of example 31 or some other example herein, wherein the first threshold metric is a system sampling time Ts multiplied by twelve.
  • Example 33 The apparatus of example 30 or some other example herein, wherein the first GNSS quality metric is associated with a frequency accuracy of the reference signal.
  • Example 34 A User Equipment (UE) device comprising an application processor, a memory, one or more antennas, a wireless interface for allowing the application processor to communicate with another device, and a touch-screen display, the UE device including the apparatus of any of examples 26 to 33 or some other example herein.
  • UE User Equipment
  • Example 35 The apparatus of any of examples 26 to 33 or some other example herein, comprising a transceiver circuitry for generating transmissions and processing transmissions.
  • Example 36 Machine readable storage media having machine executable instructions that, when executed, cause one or more processors of a User Equipment (UE) to perform an operation comprising: synchronize, to a Global Navigation Satellite System (GNSS) synchronization source and at a first time, at least one of: a timing associated with one or more sidelink channels of the UE, or a frequency associated with one or more sidelink channels of the UE; and evaluate the GNSS synchronization source for at least a threshold period of time from the first time, before selecting another synchronization source or before reselecting the GNSS synchronization source for synchronization.
  • GNSS Global Navigation Satellite System
  • Example 37 The machine readable storage media of example 36 or some other example herein, wherein the another synchronization source comprises one of: a Serving Cell, a Primary Cell, or a second UE.
  • Example 38 The machine readable storage media of any of examples 36-37 or some other example herein, wherein the threshold period of time comprises one or more seconds.
  • Example 39 The machine readable storage media of any of examples 36-38 or some other example herein, wherein to evaluate the GNSS synchronization source, the operation comprises: process one or more signals received from one or more satellites associated with the GNSS; estimate a reliability of the GNSS as a synchronization source, based on the one or more reference signals; and evaluate the GNSS synchronization source, based on the reliability of the GNSS as a synchronization source.
  • Example 40 The machine readable storage media of any of examples 36-39 or some other example herein, wherein to estimate the reliability of the GNSS as the synchronization source, the operation comprises: estimate a first GNSS quality metric, based on the one or more reference signals; compare the first GNSS quality metric to a first threshold metric; and estimate the reliability of the GNSS as the synchronization source, based on the comparison of the first GNSS quality metric to the first threshold metric.
  • Example 41 The machine readable storage media of example 40 or some other example herein, wherein the first GNSS quality metric is associated with a timing accuracy of the reference signals.
  • Example 42 The machine readable storage media of example 41 or some other example herein, wherein the first threshold metric is a system sampling time Ts multiplied by twelve.
  • Example 43 The machine readable storage media of example 40 or some other example herein, wherein the first GNSS quality metric is associated with a frequency accuracy of the reference signal.
  • Example 44 A method comprising: determining that a synchronization reference source of the UE is to be changed from a first synchronization source to a second synchronization source, wherein one of the first synchronization source or the second synchronization source is a Global Navigation Satellite System (GNSS) synchronization source; initiating an interruption for an interruption period of at least one of a signal transmission of the UE or a signal reception of the UE; and changing the synchronization reference source of the UE from the first synchronization source to the second
  • GNSS Global Navigation Satellite System
  • Example 45 The method of example 44 or some other example herein, wherein the interruption period comprises up to one subframe.
  • Example 46 The method of example 44 or some other example herein, wherein the interruption period comprises one or more subframes.
  • Example 47 The method of any of examples 44-46 or some other example herein, wherein to initiate the interruption, the method comprises: initiating the interruption of transmission or reception of one or more of: PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink Synchronization Signals) signals.
  • PSSCH Physical Sidelink Shared Channel
  • PSCCH Physical Sidelink Control Channel
  • PSBCH Physical Sidelink Broadcast Channel
  • SLSS Segmentlink Synchronization Signals
  • Example 48 The method of any of examples 44-46 or some other example herein, wherein to perform the interruption, the method comprises: initiating the interruption of transmission or reception to align with a boundary of at least one: of a transmission subframe, or a reception subframe.
  • Example 49 The method of any of examples 44-46 or some other example herein, wherein to initiate the interruption, the method comprises: initiating the interruption of transmission or reception during a last symbol of a V2V (Vehicle-to-Vehicle) subframe.
  • V2V Vehicle-to-Vehicle
  • Example 50 The method of any of examples 44-46 or some other example herein, further comprising: utilizing the synchronization reference source for at least one of: a time synchronization of one or more sidelink physical channels of the UE, or a frequency synchronization of one or more sidelink physical channels of the UE.
  • Example 51 The method of any of examples 44-46 or some other example herein, further comprising: generating, for transmission to the eNB, a signal to inform the eNB about the interruption.
  • Example 52 The method of any of examples 44-46 or some other example herein, wherein one of the first synchronization source or the second synchronization source is one of: a Serving Cell, a Primary Cell, or a second UE.
  • Example 53 A method to operate a User Equipment (UE), the method comprising: synchronizing, to a Global Navigation Satellite System (GNSS) synchronization source and at a first time, at least one of: a timing associated with one or more sidelink channels of the UE, or a frequency associated with one or more sidelink channels of the UE; and evaluating the GNSS synchronization source for at least a threshold period of time from the first time, before selecting another synchronization source or before reselecting the GNSS synchronization source for synchronization.
  • GNSS Global Navigation Satellite System
  • Example 54 The method of example 53 or some other example herein, wherein the another synchronization source comprises one of: a Serving Cell, a Primary Cell, or a second UE.
  • Example 55 The method of any of examples 53-54 or some other example herein, wherein the threshold period of time comprises one or more seconds.
  • Example 56 The method of any of examples 53-54 or some other example herein, wherein to evaluate the GNSS synchronization source, the method comprises:
  • Example 57 The method of any of examples 53-54 or some other example herein, wherein to estimate the reliability of the GNSS as the synchronization source, the method comprises: estimating a first GNSS quality metric, based on the one or more reference signals; comparing the first GNSS quality metric to a first threshold metric; and estimating the reliability of the GNSS as the synchronization source, based on the comparison of the first GNSS quality metric to the first threshold metric.
  • Example 58 The method of example 57 or some other example herein, wherein the first GNSS quality metric is associated with a timing accuracy of the reference signals.
  • Example 59 The method of example 58 or some other example herein, wherein the first threshold metric is a system sampling time Ts multiplied by twelve.
  • Example 60 The machine readable storage media of example 59 or some other example herein, wherein the first GNSS quality metric is associated with a frequency accuracy of the reference signal.

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Abstract

Described is an apparatus of a User Equipment (UE). The apparatus may comprise a first circuitry, a second circuitry, and a third circuitry. The first circuitry may be operable to determine to change a synchronization reference source of the UE from a first synchronization source to a second synchronization source, wherein one of the first synchronization source or the second synchronization source is a Global Navigation Satellite System (GNSS) synchronization source. The second circuitry may be operable to initiate an interruption of at least one of a signal transmission of the UE or a signal reception of the UE for an interruption period. The third circuitry may be operable to change the synchronization reference source of the UE from the first synchronization source to the second synchronization source, during the interruption for the interruption period.

Description

GLOBAL NAVIGATION SATELLITE SYSTEM (GNSS) BASED SYNCHRONIZATION SOURCE SELECTION AND RESELECTION FOR VEHICLE-TO- VEHICLE (V2V)
COMMUNICATION
CLAIM OF PRIORITY
[0001] The present application claims priority under 35 U.S.C. § 119(e) to United
States Provisional Patent Application Serial Number 62/401,718, filed September 29, 2016 and entitled "RRM PROCEDURES FOR LTE V2V SYNCHRONIZATION SOURCE SELECTION AND RESELECTION," and to United States Provisional Patent Application Serial Number 62/373893, filed August 11, 2016 and entitled "RRM PROCEDURES FOR LTE V2V GNSS-BASED SYNCHRONIZATION SOURCE SELECTION AND
RESELECTION," which are herein incorporated by reference in its entirety.
BACKGROUND
[0002] A variety of wireless cellular communication systems have been implemented, including a 3rd Generation Partnership Project (3GPP) Universal Mobile
Telecommunications System, a 3GPP Long-Term Evolution (LTE) system, and a 3GPP LTE- Advanced (LTE-A) system. Next-generation wireless cellular communication systems based upon LTE and LTE-A systems are being developed, such as a fifth generation (5G) wireless system / 5G mobile networks system, New Radio (NR) Access Technology, etc.
[0003] Vehicular communication systems are networks in which vehicles and roadside units are the communicating nodes, providing each other with information, such as safety warnings, traffic information, etc., thereby creating the "connected cars" concept. For example, LTE technology may provide vehicles with wireless connections among each other (e.g., vehicle to vehicle or V2V communication) and to the Internet. To address the strong interest of the automobile industry and the cellular network operators in the "connected cars" concept, LTE-based V2X services (vehicle-to-vehicle or V2V, vehicle-to- infrastructure/network or V2I/N, vehicle-to-pedestrian V2P, etc.) were recently introduced (e.g., in LTE Release 14).
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The embodiments of the disclosure will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the disclosure. However, while the drawings are to aid in explanation and understanding, they are only an aid, and should not be taken to limit the disclosure to the specific embodiments depicted therein.
[0005] Fig. 1 schematically illustrates a Vehicle to Vehicle (V2V) communication system for synchronizing a UE in a vehicle using one of possibly multiple synchronization sources, according to some embodiments.
[0006] Fig. 2 schematically illustrates, in high level, details of the UE of Fig. 1, according to some embodiments.
[0007] Fig. 3 illustrates a method for a UE to select and/or reselect an appropriate synchronization source to use as timing and/or frequency reference for one or more sidelink channels, according to some embodiments.
[0008] Fig. 4 illustrates transmission (TX) chain and/or reception (RX) chain activity during a synchronization source change to or from a GNSS synchronization source, according to some embodiments.
[0009] Fig. 5 illustrates synchronization source reselection being applied during a last symbol of a V2V subframe, according to some embodiments.
[0010] Fig. 6 illustrates an eNB and a UE, according to some embodiments.
[0011] Fig. 7 illustrates hardware processing circuitries for an eNB that supports a
UE selecting and/or reselecting appropriate synchronization sources for synchronizing the UE's sidelink channels, according to some embodiments.
[0012] Fig. 8 illustrates hardware processing circuitries for a UE for selecting and/or reselecting appropriate synchronization sources for synchronizing the UE's sidelink channels, according to some embodiments.
[0013] Fig. 9 illustrates a method for a UE to initiate an interruption while changing a synchronization reference source of the UE, according to some embodiments.
[0014] Fig. 10 illustrates a method for a UE to evaluate a GNSS synchronization source for at least a threshold period of time, before selecting another synchronization source or before resecting the GNSS synchronization source for resynchronization, according to some embodiments.
[0015] Fig. 11 illustrates an architecture of a system of a network, according to some embodiments.
[0016] Fig. 12 illustrates example components of a device, according to some embodiments. [0017] Fig. 13 illustrates example interfaces of baseband circuitry, according to some embodiments.
DETAILED DESCRIPTION
[0018] In some embodiments, in V2V communication, sidelink channels (or physical channels) may be used for communicating between UEs in vehicles. In some embodiments, the sidelink channels in a vehicle based UE may be synchronized (e.g., timing
synchronization and/or frequency synchronization reference used for transmission and/or reception of sidelink channels) based on synchronization or reference signals received from an Evolved Node-B (eNB) (e.g., referred to as eNB based synchronization), based on synchronization signals received from another vehicle based UE (e.g., referred to as UE based synchronization), and/or based on signals received from satellites of a Global
Navigation Satellite System (GNSS) (e.g., referred to as GNSS based synchronization).
[0019] In the following description, numerous details are discussed to provide a more thorough explanation of embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring embodiments of the present disclosure.
[0020] Note that in the corresponding drawings of the embodiments, signals are represented with lines. Some lines may be thicker, to indicate a greater number of constituent signal paths, and/or have arrows at one or more ends, to indicate a direction of information flow. Such indications are not intended to be limiting. Rather, the lines are used in connection with one or more exemplary embodiments to facilitate easier understanding of a circuit or a logical unit. Any represented signal, as dictated by design needs or preferences, may actually comprise one or more signals that may travel in either direction and may be implemented with any suitable type of signal scheme.
[0021] Throughout the specification, and in the claims, the term "connected" means a direct electrical, mechanical, or magnetic connection between the things that are connected, without any intermediary devices. The term "coupled" means either a direct electrical, mechanical, or magnetic connection between the things that are connected or an indirect connection through one or more passive or active intermediary devices. The term "circuit" or "module" may refer to one or more passive and/or active components that are arranged to cooperate with one another to provide a desired function. The term "signal" may refer to at least one current signal, voltage signal, magnetic signal, or data/clock signal. The meaning of "a," "an," and "the" include plural references. The meaning of "in" includes "in" and "on."
[0022] The terms "substantially," "close," "approximately," "near," and "about" generally refer to being within +/- 10% of a target value. Unless otherwise specified the use of the ordinal adjectives "first," "second," and "third," etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner.
[0023] It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.
[0024] The terms "left," "right," "front," "back," "top," "bottom," "over," "under," and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions.
[0025] For the purposes of the present disclosure, the phrases "A and/or B" and "A or
B" mean (A), (B), or (A and B). For the purposes of the present disclosure, the phrase "A, B, and/or C" means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).
[0026] In addition, the various elements of combinatorial logic and sequential logic discussed in the present disclosure may pertain both to physical structures (such as AND gates, OR gates, or XOR gates), or to synthesized or otherwise optimized collections of devices implementing the logical structures that are Boolean equivalents of the logic under discussion.
[0027] In addition, for purposes of the present disclosure, the term "eNB" may refer to a legacy eNB, a next-generation or NR gNB, a 5G eNB, an Access Point (AP), a Base Station or an eNB communicating on the unlicensed spectrum, and/or another base station for a wireless communication system. For purposes of the present disclosure, the term "UE" may refer to a legacy UE, a next-generation or NR UE, a 5G UE, an STA, and/or another mobile equipment for a wireless communication system.
[0028] Various embodiments of eNBs and/or UEs discussed below may process one or more transmissions of various types. Some processing of a transmission may comprise receiving, conducting, and/or otherwise handling a transmission that has been received. In some embodiments, an eNB or UE processing a transmission may determine or recognize the transmission's type and/or a condition associated with the transmission. For some embodiments, an eNB or UE processing a transmission may act in accordance with the transmission's type, and/or may act conditionally based upon the transmission's type. An eNB or UE processing a transmission may also recognize one or more values or fields of data carried by the transmission. Processing a transmission may comprise moving the transmission through one or more layers of a protocol stack (which may be implemented in, e.g., hardware and/or software-configured elements), such as by moving a transmission that has been received by an eNB or a UE through one or more layers of a protocol stack.
[0029] Various embodiments of eNBs and/or UEs discussed below may also generate one or more transmissions of various types. Some generating of a transmission may comprise receiving, conducting, and/or otherwise handling a transmission that is to be transmitted. In some embodiments, an eNB or UE generating a transmission may establish the transmission's type and/or a condition associated with the transmission. For some embodiments, an eNB or UE generating a transmission may act in accordance with the transmission's type, and/or may act conditionally based upon the transmission's type. An eNB or UE generating a transmission may also determine one or more values or fields of data carried by the transmission. Generating a transmission may comprise moving the transmission through one or more layers of a protocol stack (which may be implemented in, e.g., hardware and/or software-configured elements), such as by moving a transmission to be sent by an eNB or a UE through one or more layers of a protocol stack.
[0030] Fig. 1 schematically illustrates a Vehicle to Vehicle (V2V) communication system 100 for synchronizing a UE in a vehicle 102 using one of possibly multiple synchronization sources, according to some embodiments. Fig. 1 illustrates only two vehicles 102 and 106, although the system 100 may include a larger number of vehicles.
[0031] In some embodiments, each vehicle 102, 106 may include or embed communications equipment, such as a UE that may communicate in accordance with the V2V communication protocol. For example, a vehicle 102 may have an integrated, inbuilt, or an associated UE. As such, the term "vehicle" and the term "UE within the vehicle" (or vehicle based UE, or simply UE) may be used interchangeably. Thus, for example, a reference to the vehicle 102 may refer to the physical vehicle 102 and/or to a UE embedded within (or otherwise associated with) the vehicle 102. Accordingly, the vehicle 102 may also be referred to as UE 102. Similarly, a reference to the vehicle 106 may refer to the physical vehicle 106 and/or to a UE embedded within (or otherwise associated with) the vehicle 106. The vehicle 106 may also be referred to as UE 106. Because the UEs 102, 106 may be integrated within respective vehicles, the UEs 102, 106 may also be referred to as vehicle based UEs.
[0032] In some embodiments, the UE 102 may also communicate with the UE 106
(e.g., associated with the vehicle 106) on a direct UE to UE link (e.g. PC5 link), e.g., using an appropriate V2V communication standard. In an example, the UE 102 may communicate with the UE 106 using one or more sidelink channels.
[0033] In some embodiments, the UE 102 may communicate with a eNB 108 using appropriate wireless communication protocol on a cellular link (e.g. Uu link), e.g., using LTE, NR, 5G, or another communication protocol. The UE 106 may communicate with the eNB 108, or with another eNB (not illustrated in the figure).
[0034] In some embodiments, the UE 102 may also communicate with one or more satellites associated with a Global Navigation Satellite System (GNSS) 104. Examples of GNSS 104 may include, for example, Global Positioning System (GPS), Globalnaya Navigazionnaya Sputnikovaya Sistema (GLONASS), Galileo, BeiDou, or other regional satellite systems.
[0035] Fig. 1 schematically illustrates a single satellite with reference to the label 104
- however the label 104 may represent multiple satellites associated with the GNSS 104. For example, the UE 102 may receive signals from one or more satellites of the GNSS 104, and may use the signals for synchronizing timing and/or frequency of sidelink channels of the UE 102, where the sidelink channels of the UE 102 may be used for V2V communication. A reference to the GNSS 104 may imply to one or more components of the GNSS system 104, e.g., including one or more satellites associated with the GNSS system 104.
[0036] For example, the UE 102 may use assistance from the GNSS 104 in order to adjust timing and/or frequency for the LTE sidelink channels transmission and/or reception. For example, the UE 102 may use signals from a GNSS disciplined oscillator, and such synchronization may be valid across multiple carriers. GNSS synchronization may ensure relatively good accuracy in terms of timing reference and carrier frequency, however under certain conditions the accuracy of synchronization using the GNSS 104 may have relative degradation (e.g. Non-Line-Of-Sight (NLOS) satellites, blocked satellites, etc.). Using signals from satellites of the GNSS 104 for synchronizing the UE 102 (e.g., synchronizing parameters associated with the sidelink channels of the UE 102) may also be referred as herein as GNSS based synchronization.
[0037] In some embodiments, the UE 102 may also receive synchronization signals from the eNB 108, and may synchronize the timing reference and/or carrier frequency (e.g., associated with the sidelink channels of the UE 102) based on the synchronization signals from the eNB 108. In an example, the signals used to perform synchronization in such a manner may include PSS (Primary Synchronization Signal), SSS (Secondary Synchronization Signal), CRS (Cell-specific Reference Signal), and/or the like. Using signals from the eNB 108 for synchronizing the UE 102 (e.g., synchronizing parameters associated with the sidelink channels) may also be referred as herein as eNB based synchronization.
[0038] In some embodiments, the UE 102 may also use signals from other UEs (e.g.,
UE 106 associated with the vehicle, an UE in a roadside infrastructure, an UE carried by a pedestrian, etc.) for synchronization purposes. For example, the UE 102 may receive sidelink signals transmitted from other UEs (e.g., UE 106). The signals from other UEs, which may be used to perform synchronization in the UE 102, may include SLSS (Sidelink
Synchronization Signals), such as PSSS (Primary Sidelink Synchronization Signal), SSSS (Secondary Sidelink Synchronization Signal), PSBCH (Physical Sidelink Broadcast
Channel), etc. Using signals from other UEs for synchronizing the UE 102 (e.g., synchronizing parameters associated with the sidelink channels of the UE 102) may also be referred as herein as UE based synchronization.
[0039] Thus, to synchronize one or more sidelink channels of the UE 102, one or more synchronization sources may be available, where examples of such synchronization sources may be GNSS 104, eNB 108, other UEs (e.g., UE 106). In some embodiments, different synchronization source may have different priorities, e.g., depending on the scenario and network configuration parameters (e.g. GNSS based synchronization may be configured to have higher priority comparing to the eNB based synchronization). In some embodiments, such priorities may be user configurable, and/or set by the carrier. A V2V capable UE, such as UE 102, may use the synchronization method with the highest priority and reasonably good signal quality, e.g., in order to derive timing and frequency synchronization (e.g., derive transmit timing reference and adjust carrier frequency for signal transmission and reception). Merely as an example, the GNSS based synchronization sources may have higher priority comparing to other synchronization sources (e.g., compared to eNB based or UE based sources). However, under certain conditions, the quality of the GNSS signal may be relatively poor and may not allow achieving sufficient synchronization accuracy (e.g., GNSS based synchronization may become worse compared to other synchronization sources). Therefore, to ensure that the UE 102 is using an optimal, a near optimal, or a suitable synchronization source, one or more criteria may be used to make selection and/or reselection of the GNSS as a synchronization source, as discussed in further details herein. [0040] Fig. 2 schematically illustrates, in high level, details of the UE 102 of Fig. 1, according to some embodiments. In some embodiments, the UE 102 may comprise GNSS circuitry 204 for communicating with the GNSS 104. In some embodiments, the GNSS circuitry 204 may be incorporated in a chipset, which may also be referred to as a GNSS chipset.
[0041] In some embodiments, the UE 102 may also comprise LTE circuitry 208 for communicating with the eNB 108 and/or for communicating with other UEs (e.g., UE 106, via sidelink channels). In some embodiments, the LTE circuitry 208 may be incorporated in a chipset, which may also be referred to as a LTE chipset.
[0042] In some embodiments, the LTE circuitry 208 may include RF (Radio
Frequency) circuitry and/or Baseband circuitry, such as LTE modem (not illustrated in Fig. 2). Although the UE 102 may include numerous other components, such components are not illustrated in Fig. 2 for purposes of illustrative clarity.
[0043] In some embodiments, the GNSS circuitry 204 may process signals received from one or more satellites associated with the GNSS 104. For example, an antenna and/or a receiver (not illustrated in Fig. 2) of the UE 102 may receive signals from the satellites associated with the GNSS 104, and the GNSS circuitry 204 may process the received signals.
[0044] In some embodiments, the GNSS circuitry 204 may provide synchronization input to the LTE circuitry 208. For example, the GNSS circuitry 204 may provide the synchronization input to the LTE circuitry 208, which the LTE circuitry 208 may use to synchronize one or more sidelink channels of the UE 102 (e.g., if GNSS based
synchronization is used by the UE 102 to synchronize its sidelink channels). In some embodiments, the GNSS circuitry 204 may provide the synchronization input to the LTE circuitry 208, for example, in the form of a reference signal from an output of the GNSS disciplined oscillator. For example, although not illustrated in Fig. 2, satellites of the GNSS 104 may maintain one or more GNSS disciplined oscillators. The GNSS circuitry 204 may receive a reference signal from a GNSS disciplined oscillator of a GNSS satellite, and may transmit the reference signal to the LTE circuitry 208 (e.g., if GNSS based synchronization is used by the UE 102), to enable the LTE circuitry 208 to synchronize its sidelink channels based on the reference signal. In some embodiments, the GNSS circuitry 204 may also provide additional control information to the LTE circuitry 208, e.g., to characterize the reference signal.
[0045] In some embodiments, the GNSS circuitry 204 may provide information to the
LTE circuitry 208 on the GNSS synchronization signal quality (also referred to as "GNSS quality metrics" or as "GNSS quality metrics M"). In an example, the GNSS circuitry 204 may provide the GNSS quality metrics M to the LTE circuitry 208 with a certain periodicity, e.g., with a periodicity of TGNSS_Update (although in some other embodiment, the GNSS circuitry 204 may provide the GNSS quality metrics M to the LTE circuitry 208
intermittently, e.g., when there is an update in the GNSS quality metrics M). In some embodiments, the GNSS quality metrics M may comprise one or more metric, such as metric Ml, ... , MN, etc., generally referred to as metric Mi, where i = 1, ... , N.
[0046] In some embodiments, the GNSS quality metrics M may comprise an estimate of the GNSS reference signal timing accuracy, an estimate of the GNSS reference signal frequency accuracy, a signal strength and/or signal quality, information on the GNSS signal availability (e.g. GNSS signal is available or not), and/or one or more other metrics to characterize reference signal reliability of the GNSS 104. For example, the estimate of the GNSS reference signal timing accuracy may be associated with a metric Ml, the estimate of the GNSS reference signal frequency accuracy may be associated with a metric M2, and so on.
[0047] In some embodiments, the LTE circuitry 208 (e.g., an LTE modem within the
LTE circuitry 208) may estimate a GNSS synchronization reliability (R), e.g., based on the GNSS quality metrics M received from the GNSS circuitry 204. The GNSS synchronization reliability may indicate a reliability of the GNSS 104 as a synchronization source. For example, if the signal strength or signal quality received from the GNSS 104 is relatively strong or good (e.g., better than a threshold), the GNSS 104 may be considered as a reliable synchronization source, as discussed herein below.
[0048] In some embodiments, the LTE circuitry 208 may estimate the GNSS synchronization reliability R by, for example, comparing the GNSS quality metrics M to one or more thresholds. For example, the GNSS quality metrics M may comprise metric Mi, i = 1, ... , N, and each metric Mi may be compared to a corresponding threshold Ti of a set of thresholds T. In some embodiments, the GNSS synchronization reliability R may comprise a plurality of GNSS synchronization reliabilities Ri, i = 1, ... , N, e.g., corresponding to the metrics Mi.
[0049] In some embodiments, the LTE circuitry 208 (e.g., a LTE modem in the LTE circuitry 208) may perform pre-processing of the input GNSS quality metrics M (or derivatives of the GNSS quality metrics M), e.g., before comparing individual ones of the metric Mi to a corresponding threshold Ti. Such pre-processing may comprise, for example, averaging several estimates of a metric Mi over a sliding time window, or some other type of averaging.
[0050] In some embodiments, the GNSS synchronization is estimated to be reliable for a specific 1th quality metric Mi in case the GNSS signal is better than the target threshold requirement Ti, otherwise signal is considered unreliable. Whether the metric Mi is better than the corresponding threshold Ti may be based on comparing the metric Mi with the corresponding threshold Ti.
[0051] For example, assume that the GNSS synchronization reliability R comprises a plurality of GNSS synchronization reliabilities Ri, i = 1, ... , N, e.g., corresponding to the plurality of metrics Mi. A GNSS synchronization reliability Ri may be assigned a first value (e.g., a value of 1, or Ri = 1) if the GNSS synchronization is reliable for metric Mi (e.g., if the metric Mi is better than the corresponding threshold Ti). On the other hand, a GNSS synchronization reliability Ri may be assigned a second value (e.g., a value of 0, or Ri = 0) if the GNSS synchronization is not reliable for metric Mi (e.g., if the metric Mi is not better than the corresponding threshold Ti).
[0052] For example, assume a metric Mi is associated with a timing accuracy, or a frequency accuracy. In such a case, the GNSS synchronization is estimated to be reliable for the metric Mi (e.g., the GNSS signal is assumed to be better than the target threshold requirement Ti, and Ri is assigned the first value of 1) if Mi < Ti. On the other hand, the GNSS synchronization is estimated to be not reliable for the metric Mi (e.g., the GNSS signal is assumed to be not better than the target threshold requirement Ti, and Ri is assigned the second value of 0) if Mi > Ti.
[0053] In another example, assume the metric Mi is associated with a quality (e.g., a quality of reference signals received form the GNSS 104). In such a case, the GNSS synchronization is estimated to be reliable for the metric Mi (e.g., the GNSS signal is assumed to be better than the target threshold requirement Ti, and Ri is assigned the first value of 1) if Mi > Ti. On the other hand, the GNSS synchronization is estimated to be not reliable for the metric Mi (e.g., the GNSS signal is assumed to be not better than the target threshold requirement Ti, and Ri is assigned the second value of 0) if Mi < Ti.
[0054] Thus, each of the metrics Ml, ... , MN may be compared with a corresponding one of the thresholds TI, ... , TN, respectively, and the reliabilities RI, ... , RN, respectively, may be estimated. Thus, in some embodiments, the comparison against the threshold may be performed for multiple metrics Mi (e.g. time and frequency accuracy, quality, etc.). In some embodiments, the selection criteria may be expected to be satisfied for all metrics (e.g. timing accuracy, frequency accuracy, and quality has to be better than the threshold), e.g., to select the GNSS 104 as the synchronization source. For example, in such a case, the GNSS synchronization reliability R may be equal to a minimum of Rl, ... , RN, e.g., R = min(Ri).
[0055] In some other embodiments, only some (but not necessarily all) the metrics Ri may have to satisfy the selection criteria for the GNSS 104 to be selected as the
synchronization source.
[0056] In some embodiments, if the GNSS circuitry 204 provides a reference signal timing accuracy metric (e.g., corresponding to metric Ml), a corresponding threshold Tl may be defined as the LTE V2V transmit timing accuracy requirement for GNSS synchronization. Merely as an example, the threshold Tl associated with transmit timing accuracy may be 12 * Ts, where Ts may be about 1/(15000x2048) seconds. Ts has been discussed in 3GPP Technical Standard (TS) 36.211, Section 4. In an example, Ts may be a system sampling time. Thus, a synchronization reliability Rl may be 1 if an associated timing accuracy metric Ml < (12 * Ts) (e.g., the accuracy is better than ±12 * Ts); and the synchronization reliability Rl may be 0 if the associated timing accuracy metric Ml > 12 * Ts.
[0057] In some embodiments, if the GNSS circuitry 204 provides a reference signal frequency accuracy metric (e.g., metric M2), a corresponding threshold T2 may be defined as a LTE V2V transmit frequency accuracy requirement for the GNSS synchronization. Merely as an example, the threshold T2 associated with the frequency accuracy metric M2 may be 0.1 ppm (parts per million) (e.g., accuracy of ±0.1 ppm).
[0058] In some embodiments, the GNSS 104 may be considered as a reliable synchronization source (e.g., GNSS synchronization reliability R = 1) if both the timing and frequency accuracy requirements are satisfied (e.g., if Rl and R2 associated with the timing and frequency accuracy requirement, respectively, are 1). Otherwise, the GNSS 104 may be considered as an unreliable synchronization source (e.g., GNSS synchronization reliability R = 0).
[0059] In some embodiments, once the UE 102 (e.g., the LTE circuitry 208) determines that the GNSS 104 may be considered as a reliable synchronization source for synchronizing one or more sidelink channels, the UE 102 may decide on a synchronization source selection and/or reselection. The decision to select and/or reselect a synchronization source may follow the following algorithm 1.
[0060] Algorithm 1 :
(1) If UE 102 is already using a GNSS-based synchronization source: (la) If the GNSS synchronization is estimated to be unreliable (e.g., R = 0), then UE may attempt to select another synchronization source (e.g., use UE based synchronization or eNB based synchronization).
(lb) If the GNSS synchronization is estimated to be reliable (e.g., R = 1) and GNSS synchronization source has higher priority other synchronization sources (e.g., UE based synchronization or eNB based synchronization), UE may continue using GNSS-based synchronization source.
(2) If UE is using non-GNSS synchronization source:
(2a) If the GNSS synchronization is reliable (R = 1) and GNSS synchronization source has higher priority than other synchronization sources (e.g., UE based synchronization or eNB based synchronization), then UE may start using GNSS
synchronization source.
(2b) If the GNSS synchronization is estimated to be unreliable (R = 0), then UE may not attempt to select GNSS synchronization source.
[0061] Thus, algorithm 1 provides a decision-making mechanism to select and/or resect a synchronization source for synchronizing sidelink channels of the UE 102 for V2V communication.
[0062] For the purposes of this disclosure, non-GNSS synchronization source (or synchronization source other than GNSS) may imply one or more of eNB based
synchronization or UE based synchronization).
[0063] In some embodiments, algorithm 1 may result in frequent reselection of synchronization sources (e.g., frequent switching among the synchronization sources). As discussed herein later, while switching between two synchronization sources, the UE 102 may enter an interruption period during which the UE 102 may not communicate effectively. In some embodiments, to avoid too frequent reselection of synchronization sources (e.g., too frequent switching among the synchronization sources), the UE 102 may implement an evaluation period of time, Tevaluate. For example, during the evaluation time period Tevaluate, the UE 102 may check whether a synchronization source is reliable or not.
[0064] In some embodiments, when a UE (e.g., UE 102) is synchronized to the GNSS synchronization source directly, before selection and/or reselection of a new synchronization reference source, the UE 102 may evaluate the GNSS synchronization source reliability for at least a threshold period of time (e.g., few seconds), before changing the synchronization reference source from GNSS to another synchronization reference source. [0065] In some embodiments, when a UE (e.g., 102) is synchronized to a GNSS synchronization source directly, the UE 102 may evaluate the GNSS synchronization source for at least a threshold period of time (e.g., few seconds), e.g., for the purpose of deciding whether to perform selection and/or reselection of a new synchronization source.
[0066] For example, if a GNSS signal is estimated to be unreliable for quality metrics estimated during the evaluation time period Tevaluate, then the GNSS signal may be considered as unreliable (e.g., R=0), and the UE may attempt to select another
synchronization source. In another example, if the GNSS signal is estimated to be reliable for quality metrics estimated during the evaluation time period Tevaluate, then the signal can be considered as reliable (e.g., R=l), and GNSS synchronization source selection may be performed (e.g., if the UE 102 is using another synchronization source).
[0067] In some embodiments, the evaluation time period Tevaluate may be applied, for example, prior to, during and/or subsequent to comparing the GNSS quality metrics Mi to corresponding threshold Ti. In some embodiments, the evaluation time period Tevaluate may have a first value (e.g., Tevaluate_reliable) if the GNSS synchronization source is determined to be reliable; and the evaluation time period Tevaluate may have a second value (e.g., Tevaluate unreliable) if the GNSS synchronization source is determined to be unreliable. In some embodiments, the evaluation time period may be extended for other synchronization sources as well (e.g., eNB based synchronization source, UE based synchronization source, etc.).
[0068] In some embodiments, the evaluation period Tevaluate may be implemented when, for example, the UE 102 is synchronized to the GNSS system 104, and the UE 102 is to change to a different synchronization source. In some embodiments, during the evaluation period Tevaluate, the UE 102 may evaluate the GNSS synchronization source reliability.
[0069] Fig. 3 illustrates a method 300 for a UE (e.g., UE 102) to select and/or reselect an appropriate synchronization source to use as timing and/or frequency reference for one or more sidelink channels, according to some embodiments. With reference to Fig. 3, methods that may relate to the UE 102 (or other implementations of a UE discussed herein later) and associated hardware processing circuitry are discussed below. Although the actions in the method of Fig. 3 are shown in a particular order, the order of the actions can be
modified. Thus, the illustrated embodiments can be performed in a different order, and some actions may be performed in parallel. Some of the actions and/or operations listed in Fig. 3 are optional in accordance with certain embodiments. The numbering of the actions presented is for the sake of clarity and is not intended to prescribe an order of operations in which the various actions must occur. Additionally, operations from the various flows may be utilized in a variety of combinations.
[0070] Moreover, in some embodiments, machine readable storage media may have executable instructions that, when executed, cause UE 102 and/or hardware processing circuitry included in the UE 102 to perform an operation comprising the method of Fig. 3. Such machine readable storage media may include any of a variety of storage media, like magnetic storage media (e.g., magnetic tapes or magnetic disks), optical storage media (e.g., optical discs), electronic storage media (e.g., conventional hard disk drives, solid-state disk drives, or flash-memory-based storage media), or any other tangible storage media or non- transitory storage media.
[0071] In some embodiments, an apparatus may comprise means for performing various actions and/or operations of the method 300 of Fig. 3.
[0072] Returning to Fig. 3, various methods may be in accordance with the various embodiments discussed herein. The method 300 may comprise, at 304, processing one or more reference signals from a GNSS system (e.g., GNSS system 104). In some
embodiments, the processing may be performed by the GNSS circuitry 204.
[0073] At 308, GNSS synchronization signal quality metrics (e.g., GNSS quality metrics M discussed herein) may be generated. In some embodiments, the GNSS synchronization signal quality metrics may be generated by the LTE circuitry 208.
[0074] At 312, GNSS synchronization reliability (e.g., GNSS synchronization reliability R) may be evaluated (e.g., by the LTE circuitry 208). At 316, the UE 102 may select or reselect an appropriate synchronization source for synchronizing its sidelink channels.
[0075] In some embodiments, if the UE 102 is already synchronized with the GNSS system 104 during execution of the block 312, the UE 102 may perform the evaluation of the GNSS synchronization reliability for at least a threshold period of time (e.g., Tevaluate), before the UE 102 is to select another synchronization source at 316.
[0076] In some embodiments, during a change of the LTE V2V synchronization source to and/or from the GNSS synchronization source, operations of the UE 102 may be interrupted. For example, such interruption may allow the UE 102 (e.g., the LTE circuitry 208) to adjust the transmission and/or reception (TX/RX) chains parameters. For example, due to the change in the synchronization source, parameters associated with a phase locked loop (PLL) may have to be changed. [0077] In some embodiments, the change in the LTE V2V synchronization source
(e.g., used for synchronizing sidelink channels) may include a change from a non-GNSS based synchronization source (e.g. eNB based, or UE based) to a GNSS-based
synchronization source, or from the GNSS-based synchronization source to a non-GNSS based synchronization source.
[0078] Various embodiments of this disclosure discuss introduction of a dedicated
LTE modem TX/RX chain operation interruption period. Such an interruption period may enable the change of the synchronization source from a GNSS source to a non-GNSS source, or from a non-GNSS source to a GNSS source.
[0079] In some embodiments, the UE 102 may interrupt (e.g., is allowed to interrupt) a transmission chain operation and/or a receive chain operation for a period Tinterrupt, e.g., during the synchronization source change to/from the GNSS synchronization source. In some embodiments, the interruption in operation may include interruption to signal transmission and/or reception. In some embodiments, the interruption period Tinterrupt may take one or more subframes. In some embodiments, the interruption period Tinterrupt may comprise up to one subframe (e.g., the Tinterrupt may be less than or equal to one subframe).
[0080] In some embodiments, there may be a delay between the time when the UE
102 decides to change the synchronization source and the time when the interruption period Tinterrupt commences. Such delay may be, for example, used to align the interruption with a subframe boundary (e.g., such that the interruption may not start in between a subframe).
[0081] In some embodiments, during the interruption period Tinterrupt, the UE 102 may interrupt transmit and receive operation on the V2V carrier(s), e.g., one or more carriers in which the UE 102 is making transmissions and reception of V2V signals. In some embodiments, the interruption may be applicable to one or more of sidelink channels, uplink channels, and/or downlink channels. In some embodiments, the interruption may be applicable to one or more of V2V sidelink channels or sidelink signals, such as PSSCH (Physical Sidelink Shared Channel), PSCCH (Physical Sidelink Control Channel), PSBCH (Physical Sidelink Broadcast Channel), SLSS (Sidelink Synchronization Signals), etc. In some embodiments, the UE 102 may also interrupt operation on other carriers (e.g., on Primary Cell (PCell), activated Secondary Cells (SCells), etc.).
[0082] In some embodiments, the UE 102 may inform the eNB 108 about an upcoming interruption on the UE side, e.g., due to a change in the synchronization source. For example, the UE 102 may inform the eNB 108 on the anticipated interruption at the UE side via some dedicated signaling. [0083] Although in some embodiments the interruption period Tinterrupt may be applicable for a synchronization source change to and/or from the GNSS synchronization source, the interruption period Tinterrupt (or a similar interruption period) may also be applicable for synchronization source change not involving the GNSS synchronization source. For example, when there is a synchronization source change between eNB based source and UE based source, the interruption period Tinterrupt (or a similar interruption period) may also be applicable.
[0084] Fig. 4 illustrates transmission (TX) chain and/or reception (RX) chain activity
400 during a synchronization source change to or from a GNSS synchronization source, according to some embodiments. The activity 400 is with respect to time. The activity 400 may be applicable for sidelink TX chain and/or sidelink RX chain of the UE 102.
[0085] Referring to Fig. 4, prior to time t2, the UE 102 may have active sidelink
TX/RX chains. The UE 102 may use a non-GNSS synchronization source (e.g., eNB or EU based synchronization source), or a GNSS based synchronization source for synchronizing its sidelink channels.
[0086] At time tl (which may occur before to time t2), the UE 102 may make a decision to change the synchronization source from or to GNSS based synchronization source. For example, at time tl, the UE may decide to change the synchronization source from a non-GNSS based synchronization source to a GNSS based synchronization source, or from a GNSS based synchronization source to a non-GNSS based synchronization source. The decision to change the synchronization source may be reached using an appropriate manner, e.g., using Algorithm 1 discussed herein previously, using the method 300 of Fig. 3, and/or the like.
[0087] In some embodiments, the UE 102 may interrupt the TX/RX chain between time t2 and t3. For example, the time t2 may align with a start of a subframe boundary. Thus, the delay between time tl and t2 may be to align the interruption period with a subframe boundary.
[0088] In some embodiments, the time between t2 and t3 may be the interruption period Tinterrupt. In some embodiments, during this interruption period Tinterrupt, the UE 102 may perform the synchronization source switching, and may perform operations associated with such synchronization source switching. For example, due to the change in the synchronization source, parameters associated with a PLL may be changed during the interruption period Tinterrupt. [0089] From time t3 onwards, the UE 102 may operate in accordance with the new synchronization source, and the TX/RX chain may be active again from time t3.
[0090] In some embodiments, the interruption period Tinterrupt may last for one or more subframes (e.g., last for one subframe). In an example, the interruption period
Tinterrupt may be referred to as long interruption time.
[0091] In some embodiments, under certain implementation, the synchronization source reselection (e.g., switching of the synchronization source, which may necessitate change of time and/or frequency reference) may not require the long interruption time of Fig. 4. However, under such assumption, some impacts on the overall V2V demodulation performance may happen. For example, in case the synchronization source reselection is done during the V2V transmission, the transmitted packet may become corrupted (e.g. in case there is noticeable timing and/or frequency offset between the synchronization sources). Similarly, for V2V reception, the packet reception may fail in case UE 102 changes the timing and/or frequency reference during the packet reception.
[0092] In some embodiments, to avoid the above discussed potential issues, it may be possible to take into account the V2V physical layer structure. For example, a last symbol of individual V2V subframes (e.g., subframes in the sidelink channels) may not be used for sidelink signal transmission. In some embodiments, to void impacts on the demodulation performance, the synchronization source reselection may be performed during the last symbol of a V2V subframe, as illustrated in Fig. 5.
[0093] Fig. 5 illustrates synchronization source reselection being applied during a last symbol of a V2V subframe, according to some embodiments. In Fig. 5, example subframes (N-l), N, and (N+l) are illustrated. In an example, the subframes may be used for V2V communication. In an example, the subframes may be used for sidelink channels.
[0094] In some embodiments, a last symbol of each of the subframes (N-l), N, and
(N+l) are illustrated using shaded diagonal lines. In some embodiments, during the last symbol of each subframe, there may not be any sidelink signal transmission and/or reception.
[0095] Assume, for example, that the UE uses a synchronization source 1 during the subframe (N-l). The UE 102 may decide on the synchronization source reselection (e.g., switch from the synchronization source 1 to a synchronization source 2) during subframe N, as illustrated in Fig. 5. The UE 102 may continue using the synchronization source 1 for V2V communication in the subframe N.
[0096] In some embodiments, the UE 102 may perform the switching of the time reference and/or the frequency reference from synchronization source 1 to the synchronization source 2 during the last symbol of subframe N. Because the last symbol of the subframe N is not anyway used for any transmission and/or reception, there may not be possibility of packets getting corrupted due to the synchronization source reselection during the last symbol of subframe N. The UE 102 may use synchronization source 2 for V2V communication in the subframe (N+l).
[0097] In some embodiments, the synchronization source 1 may be one of GNSS based synchronization source, UE based synchronization source, or eNB based
synchronization source; and the synchronization source 2 may be another of GNSS based synchronization source, UE based synchronization source, or eNB based synchronization source.
[0098] In some embodiments, for V2V communication, the UE 102 may perform continuous monitoring of the SLSS transmissions from other UEs. However, such continuous monitoring of the SLSS transmissions from other UEs may result in drop of the SL transmissions from the UE 102, and/or may also lead to additional power consumption.
[0099] In some embodiments, under some conditions, the UE 102 may refrain from using SLSS monitoring (e.g., continuous SLSS monitoring). For example, in case eNB based synchronization source has higher priority than SyncRef UE based synchronization (e.g., eNB based synchronization source has higher priority SLSS) and the UE 102 is located in network coverage with relatively good eNB-UE link quality (e.g., the eNB-UE link quality is better than a threshold), then SLSS monitoring (e.g., continuous SLSS monitoring) may be redundant. Accordingly, the UE 102 may refrain from monitoring (e.g., continuously monitoring) SLSS transmissions from other UEs.
[00100] In some embodiments, in case the eNB-UE link quality is low (e.g., the eNB-
UE link quality is worse than a threshold), then there may be an increased probability that eNB synchronization may be lost. In such a situation, the UE 102 may perform SLSS monitoring (e.g., may monitor SLSS transmissions from other UEs).
[00101] In some embodiments, if (i) eNB based synchronization source has higher priority than SLSS based synchronization and (ii) eNB-UE link quality (e.g. RSRP) is above certain threshold, the UE 102 may not be allowed to drop its own sidelink transmissions and may refrain from monitoring SLSS transmission from other UEs.
[00102] In some embodiments, if (i) eNB based synchronization source has higher priority than SLSS based synchronization and (ii) eNB-UE link quality (e.g. RSRP) is below certain threshold, the UE 102 may be allowed to drop certain percentage of its own SL transmissions and may monitor SLSS transmission from other UEs. [00103] Fig. 6 illustrates an eNB and a UE, according to some embodiments. Fig. 6 includes block diagrams of an eNB 610 and a UE 630 which are operable to co-exist with each other and other elements of an LTE network. High-level, simplified architectures of eNB 610 and UE 630 are described so as not to obscure the embodiments. It should be noted that in some embodiments, eNB 610 may be a stationary non-mobile device. In some embodiments, the UE 630 of Fig. 6 may correspond to any UE discussed herein.
[00104] In some embodiments, the eNB 610 is coupled to one or more antennas 605, and UE 630 is similarly coupled to one or more antennas 625. However, in some
embodiments, eNB 610 may incorporate or comprise antennas 605, and UE 630 in various embodiments may incorporate or comprise antennas 625.
[00105] In some embodiments, antennas 605 and/or antennas 625 may comprise one or more directional or omni-directional antennas, including monopole antennas, dipole antennas, loop antennas, patch antennas, microstrip antennas, coplanar wave antennas, or other types of antennas suitable for transmission of RF signals. In some MIMO (multiple-input and multiple output) embodiments, antennas 605 are separated to take advantage of spatial diversity.
[00106] eNB 610 and UE 630 are operable to communicate with each other on a network, such as a wireless network (e.g., using licensed or unlicensed spectrum). eNB 610 and UE 630 may be in communication with each other over a wireless communication channel 650, which has both a downlink path from eNB 610 to UE 630 and an Uplink path from UE 630 to eNB 610.
[00107] As illustrated in Fig. 6, in some embodiments, eNB 610 may include a physical layer circuitry 612, a MAC (media access control) circuitry 614, a processor 616, a memory 618, and a hardware processing circuitry 620. A person skilled in the art will appreciate that other components not shown may be used in addition to the components shown to form a complete eNB.
[00108] In some embodiments, physical layer circuitry 612 includes a transceiver 613 for providing signals to and from UE 630. Transceiver 613 provides signals to and from UEs or other devices using one or more antennas 605. In some embodiments, MAC circuitry 614 controls access to the wireless medium. Memory 618 may be, or may include, a storage media/medium such as a magnetic storage media (e.g., magnetic tapes or magnetic disks), an optical storage media (e.g., optical discs), an electronic storage media (e.g., conventional hard disk drives, solid-state disk drives, or flash-memory-based storage media), or any tangible storage media or non-transitory storage media. Hardware processing circuitry 620 may comprise logic devices or circuitry to perform various operations. In some embodiments, processor 616 and memory 618 are arranged to perform the operations of hardware processing circuitry 620, such as operations described herein with reference to logic devices and circuitry within eNB 610 and/or hardware processing circuitry 620.
[00109] Accordingly, in some embodiments, eNB 610 may be a device comprising an application processor, a memory, one or more antenna ports, and an interface for allowing the application processor to communicate with another device.
[00110] As is also illustrated in Fig. 6, in some embodiments, UE 630 may include a physical layer circuitry 632, a MAC circuitry 634, a processor 636, a memory 638, a hardware processing circuitry 640, a wireless interface 642, and a display 644. A person skilled in the art would appreciate that other components not shown may be used in addition to the components shown to form a complete UE.
[00111] In some embodiments, physical layer circuitry 632 includes a transceiver 633 for providing signals to and from eNB 610 (as well as other eNBs). Transceiver 633 provides signals to and from eNBs or other devices using one or more antennas 625. In some embodiments, MAC circuitry 634 controls access to the wireless medium. Memory 638 may be, or may include, a storage media/medium such as a magnetic storage media (e.g., magnetic tapes or magnetic disks), an optical storage media (e.g., optical discs), an electronic storage media (e.g., conventional hard disk drives, solid-state disk drives, or flash-memory -based storage media), or any tangible storage media or non-transitory storage media. Wireless interface 642 may be arranged to allow the processor to communicate with another device. Display 644 may provide a visual and/or tactile display for a user to interact with UE 630, such as a touch-screen display. Hardware processing circuitry 640 may comprise logic devices or circuitry to perform various operations. In some embodiments, processor 636 and memory 638 may be arranged to perform the operations of hardware processing circuitry 640, such as operations described herein with reference to logic devices and circuitry within UE 630 and/or hardware processing circuitry 640.
[00112] Accordingly, in some embodiments, UE 630 may be a device comprising an application processor, a memory, one or more antennas, a wireless interface for allowing the application processor to communicate with another device, and a touch-screen display.
[00113] Elements of Fig. 6, and elements of other figures having the same names or reference numbers, can operate or function in the manner described herein with respect to any such figures (although the operation and function of such elements is not limited to such descriptions). For example, Figs. 1-2 also depict embodiments of eNBs, hardware processing circuitry of eNBs, UEs, and/or hardware processing circuitry of UEs, and the embodiments described with respect to Figs. 1-5 can operate or function in the manner described herein with respect to any of the figures.
[00114] In addition, although eNB 610 and UE 630 are each described as having several separate functional elements, one or more of the functional elements may be combined and may be implemented by combinations of software-configured elements and/or other hardware elements. In some embodiments of this disclosure, the functional elements can refer to one or more processes operating on one or more processing elements. Examples of software and/or hardware configured elements include Digital Signal Processors (DSPs), one or more microprocessors, DSPs, Field-Programmable Gate Arrays (FPGAs), Application Specific Integrated Circuits (ASICs), Radio-Frequency Integrated Circuits (RFICs), and so on.
[00115] Fig. 7 illustrates hardware processing circuitries for an eNB that supports a
UE selecting and/or reselecting appropriate synchronization sources for synchronizing the UE's sidelink channels, according to some embodiments. With reference to Fig. 6, an eNB may include various hardware processing circuitries discussed below, which may in turn comprise logic devices and/or circuitry operable to perform various operations. For example, in Fig. 6, eNB 610 (or various elements or components therein, such as hardware processing circuitry 620, or combinations of elements or components therein) may include part of, or all of, these hardware processing circuitries.
[00116] In some embodiments, one or more devices or circuitries within these hardware processing circuitries may be implemented by combinations of software-configured elements and/or other hardware elements. For example, processor 616 (and/or one or more other processors which eNB 610 may comprise), memory 618, and/or other elements or components of eNB 610 (which may include hardware processing circuitry 620) may be arranged to perform the operations of these hardware processing circuitries, such as operations described herein with reference to devices and circuitry within these hardware processing circuitries. In some embodiments, processor 616 (and/or one or more other processors which eNB 610 may comprise) may be a baseband processor.
[00117] Returning to Fig. 7, an apparatus of eNB 610 (or another eNB or base station), which may be operable to communicate with one or more UEs on a wireless network, may comprise hardware processing circuitry 700. In some embodiments, hardware processing circuitry 700 may comprise one or more antenna ports 705 operable to provide various transmissions over a wireless communication channel (such as wireless communication channel 650). Antenna ports 705 may be coupled to one or more antennas 707 (which may be antennas 605). In some embodiments, hardware processing circuitry 700 may incorporate antennas 707, while in other embodiments, hardware processing circuitry 700 may merely be coupled to antennas 707.
[00118] Antenna ports 705 and antennas 707 may be operable to provide signals from an eNB to a wireless communications channel and/or a UE, and may be operable to provide signals from a UE and/or a wireless communications channel to an eNB. For example, antenna ports 705 and antennas 707 may be operable to provide transmissions from eNB 610 to wireless communication channel 650 (and from there to UE 630, or to another
UE). Similarly, antennas 707 and antenna ports 705 may be operable to provide
transmissions from a wireless communication channel 650 (and beyond that, from UE 630, or another UE) to eNB 610.
[00119] Hardware processing circuitry 700 may comprise various circuitries operable in accordance with the various embodiments discussed herein. With reference to Fig. 7, hardware processing circuitry 700 may comprise a first circuitry 710 and a second circuitry 720.
[00120] First circuitry 710 may be operable to cause transmission of reference signals to a UE, e.g., to enable the optionally synchronize with the reference signals (e.g., if the UE selects the eNB as a synchronization source). Second circuitry 720 may be operable to cause transmission of other signals with the UE.
[00121] In some embodiments, hardware processing circuitry 700 may be coupled to a transceiver circuitry for at least one of: generating transmissions, scheduling UL
transmissions, encoding transmissions, processing transmissions, or decoding transmissions.
[00122] In some embodiments, first circuitry 710 and/or second circuitry 720 may be implemented as separate circuitries. In other embodiments, first circuitry 710 and/or second circuitry 720 may be combined and implemented together in a circuitry without altering the essence of the embodiments.
[00123] Fig. 8 illustrates hardware processing circuitries for a UE for selecting and/or reselecting appropriate synchronization sources for synchronizing the UE's sidelink channels, according to some embodiments. With reference to Fig. 6, a UE may include various hardware processing circuitries discussed below, which may in turn comprise logic devices and/or circuitry operable to perform various operations. For example, in Fig. 6, UE 630 (or various elements or components therein, such as hardware processing circuitry 640, or combinations of elements or components therein) may include part of, or all of, these hardware processing circuitries.
[00124] In some embodiments, one or more devices or circuitries within these hardware processing circuitries may be implemented by combinations of software-configured elements and/or other hardware elements. For example, processor 636 (and/or one or more other processors which UE 630 may comprise), memory 638, and/or other elements or components of UE 630 (which may include hardware processing circuitry 640) may be arranged to perform the operations of these hardware processing circuitries, such as operations described herein with reference to devices and circuitry within these hardware processing circuitries. In some embodiments, processor 636 (and/or one or more other processors which UE 630 may comprise) may be a baseband processor.
[00125] Returning to Fig. 8, an apparatus of UE 630 (or another UE or mobile handset), which may be operable to communicate with one or more eNBs on a wireless network, may comprise hardware processing circuitry 800. In some embodiments, hardware processing circuitry 800 may comprise one or more antenna ports 805 operable to provide various transmissions over a wireless communication channel (such as wireless
communication channel 650). Antenna ports 805 may be coupled to one or more antennas 807 (which may be antennas 625). In some embodiments, hardware processing circuitry 800 may incorporate antennas 807, while in other embodiments, hardware processing circuitry 800 may merely be coupled to antennas 807.
[00126] Antenna ports 805 and antennas 807 may be operable to provide signals from a UE to a wireless communications channel and/or an eNB, and may be operable to provide signals from an eNB and/or a wireless communications channel to a UE. For example, antenna ports 805 and antennas 807 may be operable to provide transmissions from UE 630 to wireless communication channel 650 (and from there to eNB 610, or to another eNB). Similarly, antennas 807 and antenna ports 805 may be operable to provide transmissions from a wireless communication channel 650 (and beyond that, from eNB 610, or another eNB) to UE 630.
[00127] Hardware processing circuitry 800 may comprise various circuitries operable in accordance with the various embodiments discussed herein. With reference to Fig. 8, hardware processing circuitry 800 may comprise a first circuitry 810, a second circuitry 820, and/or a third circuitry 830.
[00128] In some embodiments, first circuitry 810 may be operable to determine to change a synchronization reference source of the UE from a first synchronization source to a second synchronization source. In an example, one of the first synchronization source or the second synchronization source is a GNSS synchronization source. Second circuitry 820 may be operable to initiate an interruption of at least one of a signal transmission of the UE or a signal reception of the UE for an interruption period. Third circuitry 830 may be operable to change the synchronization reference source of the UE from the first synchronization source to the second synchronization source, during the interruption for the interruption period.
[00129] In some embodiments, interruption period comprises up to one subframe. In some embodiments, the interruption period comprises one or more subframes. In some embodiments, second circuitry 820 may be operable to initiate the interruption of one or more of PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink Synchronization Signals) signals. In some embodiments, second circuitry 820 may be operable to initiate the interruption of sidelink signals transmitted between the UE and a second UE. In some embodiments, second circuitry 820 may be operable to initiate the interruption of V2V (Vehicle-to-Vehicle) sidelink signals. In some embodiments, second circuitry 820 may be operable to initiate the interruption to align with a boundary of at least one of a transmission subframe or a reception subframe. In some embodiments, second circuitry 820 may be operable to initiate the interruption during a last symbol of a V2V (Vehicle-to-Vehicle) subframe. In some embodiments, the UE may utilize the
synchronization reference source for time synchronization and/or frequency synchronization of one or more sidelink channels of the UE. In some embodiments, the UE may generate a signal for transmission to the eNB, the signal to inform the eNB about the interruption. In some embodiments, another one of the first synchronization source or the second
synchronization source is one of a Serving Cell, a Primary Cell, or a second UE.
[00130] In some embodiments, first circuitry 810 may be operable to synchronize, to a
GNSS synchronization source and at a first time, at least one of timing or frequency associated with one or more sidelink channels of the UE. In some embodiments, second circuitry 820 may be operable to evaluate the GNSS synchronization source for at least a threshold period of time from the first time, before selecting another synchronization source or before resecting the GNSS synchronization source for resynchronization. In some embodiments, the another synchronization source comprises one of a Serving Cell, a Primary Cell, or a second UE. In some embodiments, the threshold period of time comprises one or more seconds. In some embodiments, to evaluate the GNSS synchronization source, the second circuitry 820 may be operable to receive reference signals from one or more satellites associated with the GNSS; estimate a reliability of the GNSS as a synchronization source, based on the reference signals; and evaluate the GNSS synchronization source, based on the reliability of the GNSS as a synchronization source. In some embodiments, to estimate the reliability of the GNSS as the synchronization source, the second circuitry 820 may be operable to estimate a first GNSS quality metric, based on the reference signals; compare the first GNSS quality metric to a first threshold metric; and estimate the reliability of the GNSS as the synchronization source, based on the comparing. In some embodiments, the first GNSS quality metric is associated with a timing accuracy of the reference signals. In some embodiments, the first threshold metric is 12 * Ts, where Ts is about 1/(15000x2048) seconds. In some embodiments, the first GNSS quality metric is associated with a frequency accuracy of the reference signal.
[00131] In some embodiments, first circuitry 810, second circuitry 820, and/or third circuitry 830 may be implemented as separate circuitries. In other embodiments, first circuitry 810, second circuitry 820, and third circuitry 830 may be combined and
implemented together in a circuitry without altering the essence of the embodiments.
[00132] Fig. 9 illustrates a method 900 for a UE to initiate an interruption while changing a synchronization reference source of the UE, according to some embodiments. With reference to Fig. 6, the method 900 that may relate to UE 630 and hardware processing circuitry 640 are discussed below. Although the actions in the method of Fig. 9 are shown in a particular order, the order of the actions can be modified. Thus, the illustrated
embodiments can be performed in a different order, and some actions may be performed in parallel. Some of the actions and/or operations listed in Fig. 9 are optional in accordance with certain embodiments. The numbering of the actions presented is for the sake of clarity and is not intended to prescribe an order of operations in which the various actions must occur. Additionally, operations from the various flows may be utilized in a variety of combinations.
[00133] Moreover, in some embodiments, machine readable storage media may have executable instructions that, when executed, cause UE 630 and/or hardware processing circuitry 640 to perform an operation comprising the method of Fig. 9. Such machine readable storage media may include any of a variety of storage media, like magnetic storage media (e.g., magnetic tapes or magnetic disks), optical storage media (e.g., optical discs), electronic storage media (e.g., conventional hard disk drives, solid-state disk drives, or flash- memory-based storage media), or any other tangible storage media or non-transitory storage media. [00134] In some embodiments, an apparatus may comprise means for performing various actions and/or operations of the method 900 of Fig. 9.
[00135] Returning to Fig. 9, the method 900 may be in accordance with the various embodiments discussed herein. The method 900 may comprise, at 904, determining to change a synchronization reference source of a UE from a first synchronization source to a second synchronization source. In some embodiments, one of the first synchronization source or the second synchronization source may be a GNSS synchronization source. At 908, an interruption of at least one of a signal transmission of the UE or a signal reception of the UE may be initiated for an interruption period. At 912, the synchronization reference source of the UE may be changed from the first synchronization source to the second
synchronization source, during the interruption for the interruption period.
[00136] In some embodiments, the interruption period may comprise up to one subframe. In some embodiments, the interruption period may comprise one or more subframes. In some embodiments, to perform the interruption, the method may comprise performing the interruption of one or more of PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink Synchronization Signals) signals. In some embodiments, to perform the interruption, the method may comprise performing the interruption of sidelink signals transmitted between the UE and a second UE. In some embodiments, to perform the interruption, the method may comprise performing the interruption of V2V (Vehicle-to-Vehicle) sidelink signals. In some embodiments, to perform the interruption, the method may comprise performing the interruption to align with a boundary of at least one of a transmission subframe or a reception subframe. In some embodiments, to perform the interruption, the method may comprise performing the interruption during a last symbol of a V2V (Vehicle-to-Vehicle) subframe. In some embodiments, the method may comprise utilizing the synchronization reference source for time synchronization and/or frequency synchronization of one or more sidelink channels of the UE. In some embodiments, the method may comprise generating a signal for
transmission to the eNB, the signal to inform the eNB about the interruption. In some embodiments, another one of the first synchronization source or the second synchronization source is one of a Serving Cell, a Primary Cell, or a second UE.
[00137] Fig. 10 illustrates a method 1000 for a UE to evaluate a GNSS
synchronization source for at least a threshold period of time, before selecting another synchronization source or before resecting the GNSS synchronization source for resynchronization, according to some embodiments. With reference to Fig. 6, the method 1000 that may relate to UE 630 and hardware processing circuitry 640 are discussed below. Although the actions in the method of Fig. 10 are shown in a particular order, the order of the actions can be modified. Thus, the illustrated embodiments can be performed in a different order, and some actions may be performed in parallel. Some of the actions and/or operations listed in Fig. 10 are optional in accordance with certain embodiments. The numbering of the actions presented is for the sake of clarity and is not intended to prescribe an order of operations in which the various actions must occur. Additionally, operations from the various flows may be utilized in a variety of combinations.
[00138] Moreover, in some embodiments, machine readable storage media may have executable instructions that, when executed, cause UE 630 and/or hardware processing circuitry 640 to perform an operation comprising the method of Fig. 10. Such machine readable storage media may include any of a variety of storage media, like magnetic storage media (e.g., magnetic tapes or magnetic disks), optical storage media (e.g., optical discs), electronic storage media (e.g., conventional hard disk drives, solid-state disk drives, or flash- memory-based storage media), or any other tangible storage media or non-transitory storage media.
[00139] In some embodiments, an apparatus may comprise means for performing various actions and/or operations of the method 1000 of Fig. 910.
[00140] Returning to Fig. 10, the method 1000 may be in accordance with the various embodiments discussed herein. The method 1000 may comprise, at 1004, synchronizing, to a GNSS synchronization source and at a first time, at least one of a timing or a frequency associated with one or more sidelink channels of the UE. At 1008, the GNSS
synchronization source may be evaluated for at least a threshold period of time from the first time, before selecting another synchronization source or before resecting the GNSS synchronization source for resynchronization.
[00141] In some embodiments, a memory of the UE may store an identification or an indication of the threshold period of time (e.g., store a duration of the threshold period of time). In some embodiments, the another synchronization source may comprise one of a Serving Cell, a Primary Cell, or a second UE. In some embodiments, the threshold period of time may comprise one or more seconds. In some embodiments, to evaluate the GNSS synchronization source, the method may comprise receiving reference signals from one or more satellites associated with the GNSS; estimating a reliability of the GNSS as a synchronization source, based on the reference signals; and evaluating the GNSS synchronization source, based on the reliability of the GNSS as a synchronization source. In some embodiments, to estimate the reliability of the GNSS as the synchronization source, the method may comprise estimating a first GNSS quality metric, based on the reference signals; comparing the first GNSS quality metric to a first threshold metric; and estimating the reliability of the GNSS as the synchronization source, based on the comparing. In some embodiments, the first GNSS quality metric may be associated with a timing accuracy of the reference signals. In some embodiments, the first threshold metric may be 12 * Ts, where Ts is a system sampling time. In some embodiments, the first GNSS quality metric may be associated with a frequency accuracy of the reference signal.
[00142] Fig. 11 illustrates an architecture of a system 1100 of a network in accordance with some embodiments. The system 1100 is shown to include a user equipment (UE) 1101 and a UE 1102. The UEs 1101 and 1102 are illustrated as smartphones (e.g., handheld touchscreen mobile computing devices connectable to one or more cellular networks), but may also comprise any mobile or non-mobile computing device, such as Personal Data Assistants (PDAs), pagers, laptop computers, desktop computers, wireless handsets, or any computing device including a wireless communications interface.
[00143] In some embodiments, any of the UEs 1101 and 1102 can comprise an Internet of Things (IoT) UE, which can comprise a network access layer designed for low-power IoT applications utilizing short-lived UE connections. An IoT UE can utilize technologies such as machine-to-machine (M2M) or machine-type communications (MTC) for exchanging data with an MTC server or device via a public land mobile network (PLMN), Proximity -Based Service (ProSe) or device-to-device (D2D) communication, sensor networks, or IoT networks. The M2M or MTC exchange of data may be a machine-initiated exchange of data. An IoT network describes interconnecting IoT UEs, which may include uniquely identifiable embedded computing devices (within the Internet infrastructure), with short-lived
connections. The IoT UEs may execute background applications (e.g., keep-alive messages, status updates, etc.) to facilitate the connections of the IoT network.
[00144] The UEs 1101 and 1102 may be configured to connect, e.g., communicatively couple, with a radio access network (RAN)— in this embodiment, an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) 1110. The UEs 1101 and 1102 utilize connections 1103 and 1104, respectively, each of which comprises a physical communications interface or layer (discussed in further detail below); in this example, the connections 1103 and 1104 are illustrated as an air interface to enable communicative coupling, and can be consistent with cellular communications protocols, such as a Global System for Mobile Communications (GSM) protocol, a code- division multiple access (CDMA) network protocol, a Push-to-Talk (PTT) protocol, a PTT over Cellular (POC) protocol, a Universal Mobile Telecommunications System (UMTS) protocol, a 3GPP Long Term Evolution (LTE) protocol, a fifth generation (5G) protocol, a New Radio (NR) protocol, and the like.
[00145] In this embodiment, the UEs 1101 and 1102 may further directly exchange communication data via a ProSe interface 1105. The ProSe interface 1105 may alternatively be referred to as a sidelink interface comprising one or more logical channels, including but not limited to a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Discovery Channel (PSDCH), and a Physical Sidelink Broadcast Channel (PSBCH). In some embodiments, both ProSe and V2V interface of a UE may use sidelink physical channels, such as PSSCH, PSCCH, PSBCH, etc.
[00146] The UE 1102 is shown to be configured to access an access point (AP) 1106 via connection 1107. The connection 1107 can comprise a local wireless connection, such as a connection consistent with any IEEE 802.11 protocol, wherein the AP 1106 would comprise a wireless fidelity (WiFi®) router. In this example, the AP 1106 is shown to be connected to the Internet without connecting to the core network of the wireless system (described in further detail below).
[00147] The E-UTRAN 1110 can include one or more access nodes that enable the connections 1103 and 1104. These access nodes (ANs) can be referred to as base stations (BSs), NodeBs, evolved NodeBs (eNBs), next Generation NodeBs (gNB), RAN nodes, and so forth, and can comprise ground stations (e.g., terrestrial access points) or satellite stations providing coverage within a geographic area (e.g., a cell). The E-UTRAN 1110 may include one or more RAN nodes for providing macrocells, e.g., macro RAN node 1111, and one or more RAN nodes for providing femtocells or picocells (e.g., cells having smaller coverage areas, smaller user capacity, or higher bandwidth compared to macrocells), e.g., low power (LP) RAN node 1112.
[00148] Any of the RAN nodes 1111 and 1112 can terminate the air interface protocol and can be the first point of contact for the UEs 1101 and 1102. In some embodiments, any of the RAN nodes 1111 and 1112 can fulfill various logical functions for the E-UTRAN 1110 including, but not limited to, radio network controller (RNC) functions such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management. [00149] In accordance with some embodiments, the UEs 1101 and 1102 can be configured to communicate using Orthogonal Frequency-Division Multiplexing (OFDM) based communication signals with each other or with any of the RAN nodes 1111 and 1112 over a multicarrier communication channel in accordance various communication techniques, such as, but not limited to, an Orthogonal Frequency-Division Multiple Access (OFDMA) communication technique (e.g., for downlink communications) or a Single Carrier Frequency Division Multiple Access (SC-FDMA) communication technique (e.g., for uplink, ProSe, sidelink communications, V2V communications, etc.), although the scope of the
embodiments is not limited in this respect. The OFDM signals can comprise a plurality of orthogonal subcarriers.
[00150] In some embodiments, a downlink resource grid can be used for downlink transmissions from any of the RAN nodes 1111 and 1112 to the UEs 1101 and 1102, while uplink transmissions can utilize similar techniques. The grid can be a time-frequency grid, called a resource grid or time-frequency resource grid, which is the physical resource in the downlink in each slot. Such a time-frequency plane representation is a common practice for OFDM systems, which makes it intuitive for radio resource allocation. Each column and each row of the resource grid corresponds to one OFDM symbol and one OFDM subcarrier, respectively. The duration of the resource grid in the time domain corresponds to one slot in a radio frame. The smallest time-frequency unit in a resource grid is denoted as a resource element. Each resource grid comprises a number of resource blocks, which describe the mapping of certain physical channels to resource elements. Each resource block comprises a collection of resource elements; in the frequency domain, this may represent the smallest quantity of resources that currently can be allocated. There are several different physical downlink channels that are conveyed using such resource blocks.
[00151] The physical downlink shared channel (PDSCH) may carry user data and higher-layer signaling to the UEs 1101 and 1102. The physical downlink control channel (PDCCH) may carry information about the transport format and resource allocations related to the PDSCH channel, among other things. It may also inform the UEs 1101 and 1102 about the transport format, resource allocation, and H-ARQ (Hybrid Automatic Repeat Request) information related to the uplink shared channel. Typically, downlink scheduling (assigning control and shared channel resource blocks to the UE 1102 within a cell) may be performed at any of the RAN nodes 1111 and 1112 based on channel quality information fed back from any of the UEs 1101 and 1102. The downlink resource assignment information may be sent on the PDCCH used for (e.g., assigned to) each of the UEs 1101 and 1102. [00152] The PDCCH may use control channel elements (CCEs) to convey the control information. Before being mapped to resource elements, the PDCCH complex-valued symbols may first be organized into quadruplets, which may then be permuted using a sub- block interleaver for rate matching. Each PDCCH may be transmitted using one or more of these CCEs, where each CCE may correspond to nine sets of four physical resource elements known as resource element groups (REGs). Four Quadrature Phase Shift Keying (QPSK) symbols may be mapped to each REG. The PDCCH can be transmitted using one or more CCEs, depending on the size of the downlink control information (DCI) and the channel condition. There can be four or more different PDCCH formats defined in LTE with different numbers of CCEs (e.g., aggregation level, L=l, 2, 4, or 8).
[00153] Some embodiments may use concepts for resource allocation for control channel information that are an extension of the above-described concepts. For example, some embodiments may utilize an enhanced physical downlink control channel (EPDCCH) that uses PDSCH resources for control information transmission. The EPDCCH may be transmitted using one or more enhanced the control channel elements (ECCEs). Similar to above, each ECCE may correspond to nine sets of four physical resource elements known as an enhanced resource element groups (EREGs). An ECCE may have other numbers of EREGs in some situations.
[00154] In some embodiments, a sidelink resource grid may be used for sidelink transmissions between the UEs 1101 and 1102. The grid may be a time-frequency grid, called a resource grid or time-frequency resource grid, which may be the physical resource in the sidelink in each slot. Such a time-frequency plane representation may be used in OFDM systems, which may make it intuitive for radio resource allocation. Each column and each row of the resource grid corresponds to one OFDM (SC-FDMA) symbol and one OFDM (SC-FDMA) subcarrier, respectively. The duration of the resource grid in the time domain may correspond to one slot in a radio frame. The smallest time-frequency unit in a resource grid may be denoted as a resource element. Each resource grid may comprise a number of resource blocks, which may describe the mapping of certain physical channels to resource elements. Each resource block comprises a collection of resource elements; in the frequency domain, this may represent the smallest quantity of resources that currently can be allocated. There are several different physical sidelink channels that are conveyed using such resource blocks.
[00155] The physical sidelink shared channel (PSSCH) may carry user data between different UEs. The physical sidelink control channel (PSCCH) may carry information about the transport format and resource allocations related to the PSSCH channel, among other things. It may also inform the UEs 1101 and 1102 about the transport format, resource allocation, etc.
[00156] The E-UTRAN 1110 is shown to be communicatively coupled to a core network— in this embodiment, an Evolved Packet Core (EPC) network 1120 via an S I interface 1113. In this embodiment the SI interface 1113 is split into two parts: the S l-U interface 1114, which carries traffic data between the RAN nodes 1111 and 1112 and the serving gateway (S-GW) 1122, and the SI -mobility management entity (MME) interface 1115, which is a signaling interface between the RAN nodes 1111 and 1112 and MMEs 1121.
[00157] In this embodiment, the EPC network 1120 comprises the MMEs 1121, the S-
GW 1122, the Packet Data Network (PDN) Gateway (P-GW) 1123, and a home subscriber server (HSS) 1124. The MMEs 1121 may be similar in function to the control plane of legacy Serving General Packet Radio Service (GPRS) Support Nodes (SGSN). The MMEs 1121 may manage mobility aspects in access such as gateway selection and tracking area list management. The HSS 1124 may comprise a database for network users, including subscription-related information to support the network entities' handling of communication sessions. The EPC network 1120 may comprise one or several HSSs 1124, depending on the number of mobile subscribers, on the capacity of the equipment, on the organization of the network, etc. For example, the HSS 1124 can provide support for routing/roaming, authentication, authorization, naming/addressing resolution, location dependencies, etc.
[00158] The S-GW 1122 may terminate the SI interface 1113 towards the E-UTRAN
1110, and routes data packets between the E-UTRAN 1110 and the EPC network 1120. In addition, the S-GW 1122 may be a local mobility anchor point for inter-RAN node handovers and also may provide an anchor for inter-3GPP mobility. Other responsibilities may include lawful intercept, charging, and some policy enforcement.
[00159] The P-GW 1123 may terminate an SGi interface toward a PDN. The P-GW
1123 may route data packets between the EPC network 1120 and extemal networks such as a network including the application server 1130 (alternatively referred to as application function (AF)) via an Internet Protocol (IP) interface 1125. Generally, the application server 1130 may be an element offering applications that use IP bearer resources with the core network (e.g., UMTS Packet Services (PS) domain, LTE PS data services, etc.). In this embodiment, the P-GW 1123 is shown to be communicatively coupled to an application server 1130 via an IP communications interface 1125. The application server 1130 can also be configured to support one or more communication services (e.g., Voice-over-Internet Protocol (VoIP) sessions, PTT sessions, group communication sessions, social networking services, etc.) for the UEs 1101 and 1102 via the EPC network 1120.
[00160] The P-GW 1123 may further be a node for policy enforcement and charging data collection. Policy and Charging Enforcement Function (PCRF) 1126 is the policy and charging control element of the EPC network 1120. In a non-roaming scenario, there may be a single PCRF in the Home Public Land Mobile Network (HPLMN) associated with a UE's Internet Protocol Connectivity Access Network (IP-CAN) session. In a roaming scenario with local breakout of traffic, there may be two PCRFs associated with a UE's IP-CAN session: a Home PCRF (H-PCRF) within a HPLMN and a Visited PCRF (V-PCRF) within a Visited Public Land Mobile Network (VPLMN). The PCRF 1126 may be communicatively coupled to the application server 1130 via the P-GW 1123. The application server 1130 may signal the PCRF 1126 to indicate a new service flow and select the appropriate Quality of Service (QoS) and charging parameters. The PCRF 1126 may provision this rule into a Policy and Charging Enforcement Function (PCEF) (not shown) with the appropriate traffic flow template (TFT) and QoS class of identifier (QCI), which commences the QoS and charging as specified by the application server 1130.
[00161] Fig. 12 illustrates example components of a device 1200 in accordance with some embodiments. In some embodiments, the device 1200 may include application circuitry 1202, baseband circuitry 1204, Radio Frequency (RF) circuitry 1206, front-end module (FEM) circuitry 1208, one or more antennas 1210, and power management circuitry (PMC) 1212 coupled together at least as shown. The components of the illustrated device 1200 may be included in a UE or a RAN node. In some embodiments, the device 1200 may include less elements (e.g., a RAN node may not utilize application circuitry 1202, and instead include a processor/controller to process IP data received from an EPC). In some embodiments, the device 1200 may include additional elements such as, for example, memory /storage, display, camera, sensor, or input/output (I/O) interface. In other embodiments, the components described below may be included in more than one device (e.g., said circuitries may be separately included in more than one device for Cloud-RAN (C- RAN) implementations).
[00162] The application circuitry 1202 may include one or more application processors. For example, the application circuitry 1202 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) may include any combination of general-purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.). The processors may be coupled with or may include memory /storage and may be configured to execute instructions stored in the memory /storage to enable various applications or operating systems to run on the device 1200. In some embodiments, processors of application circuitry 1202 may process IP data packets received from an EPC.
[00163] The baseband circuitry 1204 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 1204 may include one or more baseband processors or control logic to process baseband signals received from a receive signal path of the RF circuitry 1206 and to generate baseband signals for a transmit signal path of the RF circuitry 1206. Baseband processing circuity 1204 may interface with the application circuitry 1202 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 1206. For example, in some embodiments, the baseband circuitry 1204 may include a third generation (3G) baseband processor 1204A, a fourth generation (4G) baseband processor 1204B, a fifth generation (5G) baseband processor 1204C, or other baseband processor(s) 1204D for other existing generations, generations in development or to be developed in the future (e.g., second generation (2G), sixth generation (6G), etc.). The baseband circuitry 1204 (e.g., one or more of baseband processors 1204A-D) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 1206. In other embodiments, some or all of the functionality of baseband processors 1204A-D may be included in modules stored in the memory 1204G and executed via a Central Processing Unit (CPU) 1204E. The radio control functions may include, but are not limited to, signal modulation/demodulation,
encoding/decoding, radio frequency shifting, etc. In some embodiments,
modulation/demodulation circuitry of the baseband circuitry 1204 may include Fast-Fourier Transform (FFT), precoding, or constellation mapping/demapping functionality. In some embodiments, encoding/decoding circuitry of the baseband circuitry 1204 may include convolution, tail-biting convolution, turbo, Viterbi, or Low Density Parity Check (LDPC) encoder/decoder functionality. Embodiments of modulation/demodulation and
encoder/decoder functionality are not limited to these examples and may include other suitable functionality in other embodiments.
[00164] In some embodiments, the baseband circuitry 1204 may include one or more audio digital signal processor(s) (DSP) 1204F. The audio DSP(s) 1204F may be include elements for compression/decompression and echo cancellation and may include other suitable processing elements in other embodiments. Components of the baseband circuitry may be suitably combined in a single chip, a single chipset, or disposed on a same circuit board in some embodiments. In some embodiments, some or all of the constituent components of the baseband circuitry 1204 and the application circuitry 1202 may be implemented together such as, for example, on a system on a chip (SOC).
[00165] In some embodiments, the baseband circuitry 1204 may provide for communication compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 1204 may support communication with an evolved universal terrestrial radio access network (EUTRAN) or other wireless metropolitan area networks (WMAN), a wireless local area network (WLAN), a wireless personal area network (WPAN). Embodiments in which the baseband circuitry 1204 is configured to support radio communications of more than one wireless protocol may be referred to as multi-mode baseband circuitry.
[00166] RF circuitry 1206 may enable communication with wireless networks using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 1206 may include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry 1206 may include a receive signal path which may include circuitry to down-convert RF signals received from the FEM circuitry 1208 and provide baseband signals to the baseband circuitry 1204. RF circuitry 1206 may also include a transmit signal path which may include circuitry to up-convert baseband signals provided by the baseband circuitry 1204 and provide RF output signals to the FEM circuitry 1208 for transmission.
[00167] In some embodiments, the receive signal path of the RF circuitry 1206 may include mixer circuitry 1206a, amplifier circuitry 1206b and filter circuitry 1206c. In some embodiments, the transmit signal path of the RF circuitry 1206 may include filter circuitry 1206c and mixer circuitry 1206a. RF circuitry 1206 may also include synthesizer circuitry 1206d for synthesizing a frequency for use by the mixer circuitry 1206a of the receive signal path and the transmit signal path. In some embodiments, the mixer circuitry 1206a of the receive signal path may be configured to down-convert RF signals received from the FEM circuitry 1208 based on the synthesized frequency provided by synthesizer circuitry 1206d. The amplifier circuitry 1206b may be configured to amplify the down-converted signals and the filter circuitry 1206c may be a low-pass filter (LPF) or band-pass filter (BPF) configured to remove unwanted signals from the down-converted signals to generate output baseband signals. Output baseband signals may be provided to the baseband circuitry 1204 for further processing. In some embodiments, the output baseband signals may be zero-frequency baseband signals, although this is not a requirement. In some embodiments, mixer circuitry 1206a of the receive signal path may comprise passive mixers, although the scope of the embodiments is not limited in this respect.
[00168] In some embodiments, the mixer circuitry 1206a of the transmit signal path may be configured to up-convert input baseband signals based on the synthesized frequency provided by the synthesizer circuitry 1206d to generate RF output signals for the FEM circuitry 1208. The baseband signals may be provided by the baseband circuitry 1204 and may be filtered by filter circuitry 1206c.
[00169] In some embodiments, the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a of the transmit signal path may include two or more mixers and may be arranged for quadrature downconversion and upconversion, respectively. In some embodiments, the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a may be arranged for direct downconversion and direct upconversion, respectively. In some embodiments, the mixer circuitry 1206a of the receive signal path and the mixer circuitry 1206a of the transmit signal path may be configured for super-heterodyne operation.
[00170] In some embodiments, the output baseband signals and the input baseband signals may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternate embodiments, the output baseband signals and the input baseband signals may be digital baseband signals. In these alternate embodiments, the RF circuitry 1206 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry and the baseband circuitry 1204 may include a digital baseband interface to communicate with the RF circuitry 1206.
[00171] In some dual-mode embodiments, a separate radio IC circuitry may be provided for processing signals for each spectrum, although the scope of the embodiments is not limited in this respect.
[00172] In some embodiments, the synthesizer circuitry 1206d may be a fractional -N synthesizer or a fractional N/N+l synthesizer, although the scope of the embodiments is not limited in this respect as other types of frequency synthesizers may be suitable. For example, synthesizer circuitry 1206d may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer comprising a phase-locked loop with a frequency divider. [00173] The synthesizer circuitry 1206d may be configured to synthesize an output frequency for use by the mixer circuitry 1206a of the RF circuitry 1206 based on a frequency input and a divider control input. In some embodiments, the synthesizer circuitry 1206d may be a fractional N/N+l synthesizer.
[00174] In some embodiments, frequency input may be provided by a voltage controlled oscillator (VCO), although that is not a requirement. Divider control input may be provided by either the baseband circuitry 1204 or the applications processor 1202 depending on the desired output frequency. In some embodiments, a divider control input (e.g., N) may be determined from a look-up table based on a channel indicated by the applications processor 1202.
[00175] Synthesizer circuitry 1206d of the RF circuitry 1206 may include a divider, a delay-locked loop (DLL), a multiplexer and a phase accumulator. In some embodiments, the divider may be a dual modulus divider (DMD) and the phase accumulator may be a digital phase accumulator (DP A). In some embodiments, the DMD may be configured to divide the input signal by either N or N+l (e.g., based on a carry out) to provide a fractional division ratio. In some example embodiments, the DLL may include a set of cascaded, tunable, delay elements, a phase detector, a charge pump and a D-type flip-flop. In these embodiments, the delay elements may be configured to break a VCO period up into Nd equal packets of phase, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.
[00176] In some embodiments, synthesizer circuitry 1206d may be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency may be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and used in conjunction with quadrature generator and divider circuitry to generate multiple signals at the carrier frequency with multiple different phases with respect to each other. In some embodiments, the output frequency may be a LO frequency (fLO). In some embodiments, the RF circuitry 1206 may include an IQ/polar converter.
[00177] FEM circuitry 1208 may include a receive signal path which may include circuitry configured to operate on RF signals received from one or more antennas 1210, amplify the received signals and provide the amplified versions of the received signals to the RF circuitry 1206 for further processing. FEM circuitry 1208 may also include a transmit signal path which may include circuitry configured to amplify signals for transmission provided by the RF circuitry 1206 for transmission by one or more of the one or more antennas 1210. In various embodiments, the amplification through the transmit or receive signal paths may be done solely in the RF circuitry 1206, solely in the FEM 1208, or in both the RF circuitry 1206 and the FEM 1208.
[00178] In some embodiments, the FEM circuitry 1208 may include a TX/RX switch to switch between transmit mode and receive mode operation. The FEM circuitry may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuitry may include an LNA to amplify received RF signals and provide the amplified received RF signals as an output (e.g., to the RF circuitry 1206). The transmit signal path of the FEM circuitry 1208 may include a power amplifier (PA) to amplify input RF signals (e.g., provided by RF circuitry 1206), and one or more filters to generate RF signals for subsequent transmission (e.g., by one or more of the one or more antennas 1210).
[00179] In some embodiments, the PMC 1212 may manage power provided to the baseband circuitry 1204. In particular, the PMC 1212 may control power-source selection, voltage scaling, battery charging, or DC-to-DC conversion. The PMC 1212 may often be included when the device 1200 is capable of being powered by a battery, for example, when the device is included in a UE. The PMC 1212 may increase the power conversion efficiency while providing desirable implementation size and heat dissipation characteristics.
[00180] While Fig. 12 shows the PMC 1212 coupled only with the baseband circuitry 1204. However, in other embodiments, the PMC 1212 may be additionally or alternatively coupled with, and perform similar power management operations for, other components such as, but not limited to, application circuitry 1202, RF circuitry 1206, or FEM 1208.
[00181] Processors of the application circuitry 1202 and processors of the baseband circuitry 1204 may be used to execute elements of one or more instances of a protocol stack. For example, processors of the baseband circuitry 1204, alone or in combination, may be used execute Layer 3, Layer 2, or Layer 1 functionality, while processors of the application circuitry 1204 may utilize data (e.g., packet data) received from these layers and further execute Layer 4 functionality (e.g., transmission communication protocol (TCP) and user datagram protocol (UDP) layers). As referred to herein, Layer 3 may comprise a radio resource control (RRC) layer, described in further detail below. As referred to herein, Layer 2 may comprise a medium access control (MAC) layer, a radio link control (RLC) layer, and a packet data convergence protocol (PDCP) layer, described in further detail below. As referred to herein, Layer 1 may comprise a physical (PHY) layer of a UE/RAN node, described in further detail below. [00182] Fig. 13 illustrates example interfaces of baseband circuitry in accordance with some embodiments. As discussed above, the baseband circuitry 1204 of Fig. 12 may comprise processors 1204A-1204E and a memory 1204G utilized by said processors. Each of the processors 1204A-1204E may include a memory interface, 1304A-1304E, respectively, to send/receive data to/from the memory 1204G.
[00183] The baseband circuitry 1204 may further include one or more interfaces to communicatively couple to other circuitries/devices, such as a memory interface 1312 (e.g., an interface to send/receive data to/from memory extemal to the baseband circuitry 1204), an application circuitry interface 1314 (e.g., an interface to send/receive data to/from the application circuitry 1202 of Fig. 12), an RF circuitry interface 1316 (e.g., an interface to send/receive data to/from RF circuitry 1206 of Fig. 12), a wireless hardware connectivity interface 1318 (e.g., an interface to send/receive data to/from Near Field Communication (NFC) components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components), and a power management interface 1320 (e.g., an interface to send/receive power or control signals to/from the PMC 1212.
[00184] Reference in the specification to "an embodiment," "one embodiment," "some embodiments," or "other embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some embodiments, but not necessarily all embodiments. The various appearances of "an embodiment," "one embodiment," or "some embodiments" are not necessarily all referring to the same embodiments. If the specification states a component, feature, structure, or characteristic "may," "might," or "could" be included, that particular component, feature, structure, or characteristic is not required to be included. If the specification or claim refers to "a" or "an" element, that does not mean there is only one of the elements. If the specification or claims refer to "an additional" element, that does not preclude there being more than one of the additional element.
[00185] Furthermore, the particular features, structures, functions, or characteristics may be combined in any suitable manner in one or more embodiments. For example, a first embodiment may be combined with a second embodiment anywhere the particular features, structures, functions, or characteristics associated with the two embodiments are not mutually exclusive.
[00186] While the disclosure has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations of such embodiments will be apparent to those of ordinary skill in the art in light of the foregoing description. For example, other memory architectures e.g., Dynamic RAM (DRAM) may use the
embodiments discussed. The embodiments of the disclosure are intended to embrace all such alternatives, modifications, and variations as to fall within the broad scope of the appended claims.
[00187] In addition, well known power/ground connections to integrated circuit (IC) chips and other components may or may not be shown within the presented figures, for simplicity of illustration and discussion, and so as not to obscure the disclosure. Further, arrangements may be shown in block diagram form in order to avoid obscuring the disclosure, and also in view of the fact that specifics with respect to implementation of such block diagram arrangements are highly dependent upon the platform within which the present disclosure is to be implemented (i.e., such specifics should be well within purview of one skilled in the art). Where specific details (e.g., circuits) are set forth in order to describe example embodiments of the disclosure, it should be apparent to one skilled in the art that the disclosure can be practiced without, or with variation of, these specific details. The description is thus to be regarded as illustrative instead of limiting.
[00188] The following examples pertain to further embodiments. Specifics in the examples may be used anywhere in one or more embodiments. All optional features of the apparatus described herein may also be implemented with respect to a method or process.
[00189] Example 1. An apparatus of a User Equipment (UE) operable to communicate with an Evolved Node B (eNB) on a wireless network, comprising: a memory to store instructions; and one or more processors to execute the stored instructions to perform:
determine that a synchronization reference source of the UE is to be changed from a first synchronization source to a second synchronization source, wherein one of the first synchronization source or the second synchronization source is a Global Navigation Satellite System (GNSS) synchronization source; initiate an interruption for an interruption period of at least one of a signal transmission of the UE or a signal reception of the UE; and change the synchronization reference source of the UE from the first synchronization source to the second synchronization source, during the interruption for the interruption period.
[00190] Example 2. The apparatus of example 1 or some other example herein, wherein the interruption period comprises up to one subframe.
[00191] Example 3. The apparatus of example 1 or some other example herein, wherein the interruption period comprises one or more subframes.
[00192] Example 4. The apparatus of any of examples 1-3 or some other example herein, wherein to initiate the interruption, the one or more processors are to: initiate the interruption of transmission or reception of one or more of: PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink Synchronization Signals) signals.
[00193] Example 5. The apparatus of any of examples 1-4 or some other example herein, wherein the UE is a first UE, and wherein to initiate the interruption, the one or more processors are to: initiate the interruption of transmission or reception of sidelink signals transmitted between the first UE and a second UE.
[00194] Example 6. The apparatus of any of examples 1-5 or some other example herein, wherein to initiate the interruption, the one or more processors are to: initiate the interruption of transmission or reception of V2V (Vehicle-to-Vehicle) sidelink signals.
[00195] Example 7. The apparatus of any of examples 1-6 or some other example herein, wherein to initiate the interruption, the one or more processors are to: initiate the interruption of transmission or reception to align with a boundary of at least one of: a transmission subframe, or a reception subframe.
[00196] Example 8. The apparatus of any of examples 1-7 or some other example herein, wherein to initiate the interruption, the one or more processors are to: initiate the interruption of transmission or reception during a last symbol of a V2V (Vehicle-to-Vehicle) subframe.
[00197] Example 9. The apparatus of any of examples 1-8 or some other example herein, wherein the one or more processors are to: utilize the synchronization reference source for at least one of: a time synchronization for transmission or reception of one or more sidelink physical channels of the UE, or a frequency synchronization for transmission or reception of one or more sidelink physical channels of the UE.
[00198] Example 10. The apparatus of any of examples 1-9 or some other example herein, wherein the one or more processors are to: generate, for transmission to the eNB, a signal to inform the eNB about the interruption of transmission or reception.
[00199] Example 11. The apparatus of any of examples 1-10 or some other example herein, wherein one of the first synchronization source or the second synchronization source is one of: a Serving Cell, a Primary Cell, or a second UE.
[00200] Example 12. The apparatus of any of examples 1 to 11 or some other example herein, comprising a transceiver circuitry for generating transmissions and processing transmissions.
[00201] Example 13. A User Equipment (UE) device comprising an application processor, a memory, one or more antennas, a wireless interface for allowing the application processor to communicate with another device, and a touch-screen display, the UE device including the apparatus of any of examples 1 to 12 or some other example herein.
[00202] Example 14. Machine readable storage media having machine executable instructions that, when executed, cause one or more processors of a User Equipment (UE) to perform an operation comprising: determine that a synchronization reference source of the UE is to be changed from a first synchronization source to a second synchronization source, wherein one of the first synchronization source or the second synchronization source is a Global Navigation Satellite System (GNSS) synchronization source; initiate an interruption for an interruption period of at least one of a signal transmission of the UE or a signal reception of the UE; and change the synchronization reference source of the UE from the first synchronization source to the second synchronization source, during the interruption for the interruption period.
[00203] Example 15. The machine readable storage media of example 14 or some other example herein, wherein the interruption period comprises up to one subframe.
[00204] Example 16. The machine readable storage media of example 14 or some other example herein, wherein the interruption period comprises one or more subframes.
[00205] Example 17. The machine readable storage media of any of examples 14-16 or some other example herein, wherein to initiate the interruption, the operation comprises: initiate the interruption of transmission or reception of one or more of: PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink Synchronization Signals) signals.
[00206] Example 18. The machine readable storage media of any of examples 14-17 or some other example herein, wherein the UE is a first UE, and wherein to initiate the interruption, the operation comprises: initiate the interruption of transmission or reception of sidelink signals transmitted between the first UE and a second UE.
[00207] Example 19. The machine readable storage media of any of examples 14-18 or some other example herein, wherein to initiate the interruption, the operation comprises: initiate the interruption of transmission or reception of V2V (Vehicle-to-Vehicle) sidelink signals.
[00208] Example 20. The machine readable storage media of any of examples 14-19 or some other example herein, wherein to initiate the interruption, the operation comprises: initiate the interruption of transmission or reception of one or more sidelink signals of the UE. [00209] Example 21. The machine readable storage media of any of examples 14-20 or some other example herein, wherein to perform the interruption, the operation comprises: initiate the interruption of transmission or reception to align with a boundary of at least one: of a transmission subframe, or a reception subframe.
[00210] Example 22. The machine readable storage media of any of examples 14-21 or some other example herein, wherein to initiate the interruption, the operation comprises: initiate the interruption of transmission or reception during a last symbol of a V2V (Vehicle- to-Vehicle) subframe.
[00211] Example 23. The machine readable storage media of any of examples 14-22 or some other example herein, the operation comprising: utilize the synchronization reference source for at least one of: a time synchronization of one or more sidelink physical channels of the UE, or a frequency synchronization of one or more sidelink physical channels of the UE.
[00212] Example 24. The machine readable storage media of any of examples 14-23 or some other example herein, the operation comprising: generate, for transmission to the eNB, a signal to inform the eNB about the interruption.
[00213] Example 25. The machine readable storage media of any of examples 14-24 or some other example herein, wherein one of the first synchronization source or the second synchronization source is one of: a Serving Cell, a Primary Cell, or a second UE.
[00214] Example 26. An apparatus of a User Equipment (UE) operable to
communicate with an Evolved Node B (eNB) on a wireless network, comprising: one or more processors to: synchronize, to a Global Navigation Satellite System (GNSS) synchronization source and at a first time, at least one of: a timing associated with one or more sidelink channels of the UE, or a frequency associated with one or more sidelink channels of the UE, and evaluate the GNSS synchronization source for at least a threshold period of time from the first time, before selecting another synchronization source or before reselecting the GNSS synchronization source for synchronization; and a memory to store an indication of the threshold period of time.
[00215] Example 27. The apparatus of example 26 or some other example herein, wherein the another synchronization source comprises one of: a Serving Cell, a Primary Cell, or a second UE.
[00216] Example 28. The apparatus of any of examples 26-27 or some other example herein, wherein the threshold period of time comprises one or more seconds.
[00217] Example 29. The apparatus of any of examples 26-28 or some other example herein, wherein to evaluate the GNSS synchronization source, the one or more processors are to: process one or more signals received from one or more satellites associated with the GNSS synchronization source; estimate a reliability of the GNSS as a synchronization source, based on the one or more reference signals; and evaluate the GNSS synchronization source, based on the reliability of the GNSS as a synchronization source.
[00218] Example 30. The apparatus of example 29 or some other example herein, wherein to estimate the reliability of the GNSS as the synchronization source, the one or more processors are to: estimate a first GNSS quality metric, based on the one or more reference signals; compare the first GNSS quality metric to a first threshold metric; and estimate the reliability of the GNSS as the synchronization source, based on the comparison of the first GNSS quality metric to the first threshold metric.
[00219] Example 31. The apparatus of example 30 or some other example herein, wherein the first GNSS quality metric is associated with a timing accuracy of the reference signals.
[00220] Example 32. The apparatus of example 31 or some other example herein, wherein the first threshold metric is a system sampling time Ts multiplied by twelve.
[00221] Example 33. The apparatus of example 30 or some other example herein, wherein the first GNSS quality metric is associated with a frequency accuracy of the reference signal.
[00222] Example 34. A User Equipment (UE) device comprising an application processor, a memory, one or more antennas, a wireless interface for allowing the application processor to communicate with another device, and a touch-screen display, the UE device including the apparatus of any of examples 26 to 33 or some other example herein.
[00223] Example 35. The apparatus of any of examples 26 to 33 or some other example herein, comprising a transceiver circuitry for generating transmissions and processing transmissions.
[00224] Example 36. Machine readable storage media having machine executable instructions that, when executed, cause one or more processors of a User Equipment (UE) to perform an operation comprising: synchronize, to a Global Navigation Satellite System (GNSS) synchronization source and at a first time, at least one of: a timing associated with one or more sidelink channels of the UE, or a frequency associated with one or more sidelink channels of the UE; and evaluate the GNSS synchronization source for at least a threshold period of time from the first time, before selecting another synchronization source or before reselecting the GNSS synchronization source for synchronization. [00225] Example 37. The machine readable storage media of example 36 or some other example herein, wherein the another synchronization source comprises one of: a Serving Cell, a Primary Cell, or a second UE.
[00226] Example 38. The machine readable storage media of any of examples 36-37 or some other example herein, wherein the threshold period of time comprises one or more seconds.
[00227] Example 39. The machine readable storage media of any of examples 36-38 or some other example herein, wherein to evaluate the GNSS synchronization source, the operation comprises: process one or more signals received from one or more satellites associated with the GNSS; estimate a reliability of the GNSS as a synchronization source, based on the one or more reference signals; and evaluate the GNSS synchronization source, based on the reliability of the GNSS as a synchronization source.
[00228] Example 40. The machine readable storage media of any of examples 36-39 or some other example herein, wherein to estimate the reliability of the GNSS as the synchronization source, the operation comprises: estimate a first GNSS quality metric, based on the one or more reference signals; compare the first GNSS quality metric to a first threshold metric; and estimate the reliability of the GNSS as the synchronization source, based on the comparison of the first GNSS quality metric to the first threshold metric.
[00229] Example 41. The machine readable storage media of example 40 or some other example herein, wherein the first GNSS quality metric is associated with a timing accuracy of the reference signals.
[00230] Example 42. The machine readable storage media of example 41 or some other example herein, wherein the first threshold metric is a system sampling time Ts multiplied by twelve.
[00231] Example 43. The machine readable storage media of example 40 or some other example herein, wherein the first GNSS quality metric is associated with a frequency accuracy of the reference signal.
[00232] Example 44. A method comprising: determining that a synchronization reference source of the UE is to be changed from a first synchronization source to a second synchronization source, wherein one of the first synchronization source or the second synchronization source is a Global Navigation Satellite System (GNSS) synchronization source; initiating an interruption for an interruption period of at least one of a signal transmission of the UE or a signal reception of the UE; and changing the synchronization reference source of the UE from the first synchronization source to the second
synchronization source, during the interruption for the interruption period.
[00233] Example 45. The method of example 44 or some other example herein, wherein the interruption period comprises up to one subframe.
[00234] Example 46. The method of example 44 or some other example herein, wherein the interruption period comprises one or more subframes.
[00235] Example 47. The method of any of examples 44-46 or some other example herein, wherein to initiate the interruption, the method comprises: initiating the interruption of transmission or reception of one or more of: PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink Synchronization Signals) signals.
[00236] Example 48. The method of any of examples 44-46 or some other example herein, wherein to perform the interruption, the method comprises: initiating the interruption of transmission or reception to align with a boundary of at least one: of a transmission subframe, or a reception subframe.
[00237] Example 49. The method of any of examples 44-46 or some other example herein, wherein to initiate the interruption, the method comprises: initiating the interruption of transmission or reception during a last symbol of a V2V (Vehicle-to-Vehicle) subframe.
[00238] Example 50. The method of any of examples 44-46 or some other example herein, further comprising: utilizing the synchronization reference source for at least one of: a time synchronization of one or more sidelink physical channels of the UE, or a frequency synchronization of one or more sidelink physical channels of the UE.
[00239] Example 51. The method of any of examples 44-46 or some other example herein, further comprising: generating, for transmission to the eNB, a signal to inform the eNB about the interruption.
[00240] Example 52. The method of any of examples 44-46 or some other example herein, wherein one of the first synchronization source or the second synchronization source is one of: a Serving Cell, a Primary Cell, or a second UE.
[00241] Example 53. A method to operate a User Equipment (UE), the method comprising: synchronizing, to a Global Navigation Satellite System (GNSS) synchronization source and at a first time, at least one of: a timing associated with one or more sidelink channels of the UE, or a frequency associated with one or more sidelink channels of the UE; and evaluating the GNSS synchronization source for at least a threshold period of time from the first time, before selecting another synchronization source or before reselecting the GNSS synchronization source for synchronization.
[00242] Example 54. The method of example 53 or some other example herein, wherein the another synchronization source comprises one of: a Serving Cell, a Primary Cell, or a second UE.
[00243] Example 55. The method of any of examples 53-54 or some other example herein, wherein the threshold period of time comprises one or more seconds.
[00244] Example 56. The method of any of examples 53-54 or some other example herein, wherein to evaluate the GNSS synchronization source, the method comprises:
processing one or more signals received from one or more satellites associated with the GNSS; estimating a reliability of the GNSS as a synchronization source, based on the one or more reference signals; and evaluating the GNSS synchronization source, based on the reliability of the GNSS as a synchronization source.
[00245] Example 57. The method of any of examples 53-54 or some other example herein, wherein to estimate the reliability of the GNSS as the synchronization source, the method comprises: estimating a first GNSS quality metric, based on the one or more reference signals; comparing the first GNSS quality metric to a first threshold metric; and estimating the reliability of the GNSS as the synchronization source, based on the comparison of the first GNSS quality metric to the first threshold metric.
[00246] Example 58. The method of example 57 or some other example herein, wherein the first GNSS quality metric is associated with a timing accuracy of the reference signals.
[00247] Example 59. The method of example 58 or some other example herein, wherein the first threshold metric is a system sampling time Ts multiplied by twelve.
[00248] Example 60. The machine readable storage media of example 59 or some other example herein, wherein the first GNSS quality metric is associated with a frequency accuracy of the reference signal.
[00249] An abstract is provided that will allow the reader to ascertain the nature and gist of the technical disclosure. The abstract is submitted with the understanding that it will not be used to limit the scope or meaning of the claims. The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.

Claims

CLAIMS We claim:
1. An apparatus of a User Equipment (UE) operable to communicate with an Evolved Node B (eNB) on a wireless network, comprising:
a memory to store instructions; and
one or more processors to execute the stored instructions to perform:
determine that a synchronization reference source of the UE is to be changed from a first synchronization source to a second synchronization source, wherein one of the first synchronization source or the second synchronization source is a Global Navigation
Satellite System (GNSS) synchronization source;
initiate an interruption for an interruption period of at least one of a signal transmission of the UE or a signal reception of the UE; and
change the synchronization reference source of the UE from the first synchronization source to the second synchronization source, during the interruption for the interruption period.
2. The apparatus of claim 1, wherein the interruption period comprises up to one subframe.
3. The apparatus of claim 1, wherein the interruption period comprises one or more subframes.
4. The apparatus of any of claims 1-3, wherein to initiate the interruption, the one or more processors are to:
initiate the interruption of transmission or reception of one or more of: PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink Synchronization Signals) signals.
5. The apparatus of any of claims 1-3, wherein the UE is a first UE, and wherein to initiate the interruption, the one or more processors are to:
initiate the interruption of transmission or reception of sidelink signals transmitted between the first UE and a second UE.
6. The apparatus of any of claims 1-3, wherein to initiate the interruption, the one or more processors are to:
initiate the interruption of transmission or reception of V2V (Vehicle-to-Vehicle) sidelink signals.
7. The apparatus of any of claims 1-3, wherein to initiate the interruption, the one or more processors are to:
initiate the interruption of transmission or reception to align with a boundary of at least one of: a transmission subframe, or a reception subframe.
8. The apparatus of any of claims 1-3, wherein to initiate the interruption, the one or more processors are to:
initiate the interruption of transmission or reception during a last symbol of a V2V (Vehicle-to-Vehicle) subframe.
9. The apparatus of any of claims 1-3, wherein the one or more processors are to:
utilize the synchronization reference source for at least one of: a time synchronization for transmission or reception of one or more sidelink physical channels of the UE, or a frequency synchronization for transmission or reception of one or more sidelink physical channels of the UE.
10. The apparatus of any of claims 1-3, wherein the one or more processors are to:
generate, for transmission to the eNB, a signal to inform the eNB about the interruption of transmission or reception.
11. The apparatus of any of claims 1-3, wherein one of the first synchronization source or the second synchronization source is one of: a Serving Cell, a Primary Cell, or a second UE.
12. Machine readable storage media having machine executable instructions that, when executed, cause one or more processors of a User Equipment (UE) to perform an operation comprising:
determine that a synchronization reference source of the UE is to be changed from a first synchronization source to a second synchronization source, wherein one of the first synchronization source or the second synchronization source is a Global Navigation Satellite System (GNSS) synchronization source;
initiate an interruption for an interruption period of at least one of a signal transmission of the UE or a signal reception of the UE; and
change the synchronization reference source of the UE from the first synchronization source to the second synchronization source, during the interruption for the interruption period.
13. The machine readable storage media of claim 12, wherein the interruption period comprises up to one subframe.
14. The machine readable storage media of claim 12, wherein the interruption period comprises one or more subframes.
15. The machine readable storage media of any of claims 12-14, wherein to initiate the interruption, the operation comprises:
initiate the interruption of transmission or reception of one or more of: PSSCH (Physical Sidelink Shared Channel) signals, PSCCH (Physical Sidelink Control Channel) signals, PSBCH (Physical Sidelink Broadcast Channel) signals, or SLSS (Sidelink
Synchronization Signals) signals.
16. The machine readable storage media of any of claims 12-14, wherein to perform the interruption, the operation comprises:
initiate the interruption of transmission or reception to align with a boundary of at least one: of a transmission subframe, or a reception subframe.
17. The machine readable storage media of any of claims 12-14, wherein to initiate the interruption, the operation comprises:
initiate the interruption of transmission or reception during a last symbol of a V2V (Vehicle-to-Vehicle) subframe.
18. The machine readable storage media of any of claims 12-14, the operation comprising: utilize the synchronization reference source for at least one of: a time synchronization of one or more sidelink physical channels of the UE, or a frequency synchronization of one or more sidelink physical channels of the UE.
19. The machine readable storage media of any of claims 12-14, the operation comprising:
generate, for transmission to the eNB, a signal to inform the eNB about the interruption.
20. The machine readable storage media of any of claims 12-14, wherein one of the first synchronization source or the second synchronization source is one of: a Serving Cell, a Primary Cell, or a second UE.
21. An apparatus of a User Equipment (UE) operable to communicate with an Evolved Node-B (eNB) on a wireless network, comprising:
one or more processors to:
synchronize, to a Global Navigation Satellite System (GNSS) synchronization source and at a first time, at least one of: a timing associated with one or more sidelink channels of the UE, or a frequency associated with one or more sidelink channels of the UE, and
evaluate the GNSS synchronization source for at least a threshold period of time from the first time, before selecting another synchronization source or before reselecting the GNSS synchronization source for synchronization; and
a memory to store an indication of the threshold period of time.
22. The apparatus of claim 21, wherein to evaluate the GNSS synchronization source, the one or more processors are to:
process one or more signals received from one or more satellites associated with the GNSS synchronization source;
estimate a reliability of the GNSS as a synchronization source, based on the one or more reference signals; and
evaluate the GNSS synchronization source, based on the reliability of the GNSS as a synchronization source.
23. The apparatus of claim 22, wherein to estimate the reliability of the GNSS as the synchronization source, the one or more processors are to:
estimate a first GNSS quality metric, based on the one or more reference signals; compare the first GNSS quality metric to a first threshold metric; and
estimate the reliability of the GNSS as the synchronization source, based on the comparison of the first GNSS quality metric to the first threshold metric.
24. The apparatus of claim 23, wherein the first GNSS quality metric is associated with a timing accuracy of the reference signals.
25. The apparatus of claim 24, wherein the first threshold metric is a system sampling time Ts multiplied by twelve.
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021062862A1 (en) * 2019-10-02 2021-04-08 Mediatek Singapore Pte. Ltd. Synchronization reference reselection procedure design for v2x communication
EP4135445A4 (en) * 2020-04-07 2024-05-01 LG Electronics, Inc. Method and apparatus for determining sidelink resources in nr v2x
EP4152838A1 (en) * 2021-09-17 2023-03-22 Nokia Technologies Oy Sidelink synchronization
WO2023041330A1 (en) * 2021-09-17 2023-03-23 Nokia Technologies Oy Sidelink synchronization

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