WO2018143847A1 - Attribution de séquence de synchronisation flexible - Google Patents

Attribution de séquence de synchronisation flexible Download PDF

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Publication number
WO2018143847A1
WO2018143847A1 PCT/SE2017/050909 SE2017050909W WO2018143847A1 WO 2018143847 A1 WO2018143847 A1 WO 2018143847A1 SE 2017050909 W SE2017050909 W SE 2017050909W WO 2018143847 A1 WO2018143847 A1 WO 2018143847A1
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Prior art keywords
wireless network
synchronization sequences
sequences
synchronization
sequence
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PCT/SE2017/050909
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English (en)
Inventor
Johan AXNÄS
Andres Reial
Henrik Sahlin
Naga Vishnu Kanth IRUKULAPATI
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Telefonaktiebolaget Lm Ericsson (Publ)
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Publication of WO2018143847A1 publication Critical patent/WO2018143847A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H04L27/2613—Structure of the reference signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J13/00—Code division multiplex systems
    • H04J13/16—Code allocation
    • H04J13/22—Allocation of codes with a zero correlation zone
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2668—Details of algorithms
    • H04L27/2673—Details of algorithms characterised by synchronisation parameters
    • H04L27/2675—Pilot or known symbols
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W56/00—Synchronisation arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
    • H04J2011/0096—Network synchronisation

Definitions

  • a User Equipment device When a User Equipment device (UE) is powered on, wakes from a low-power state, or when it moves between cells in Long Term Evolution (LTE) Release 8 and later, it receives and synchronizes to downlink signals in a cell search procedure.
  • the purpose of this cell search is to identify the best cell and to achieve time and frequency synchronization to the network in downlink (i.e., from the base station to the UE).
  • Synchronization sequences preferably possess "good" auto and cross-correlation properties to minimize missed detection (i.e., where a transmitted synchronization signal is not detected) and false alarm (i.e., where a UE detects a synchronization signal based on a sequence which was not transmitted) probability and provide good time/frequency offset estimates.
  • LTE Third Generation Partnership Project (3GPP) Technical Specification (TS) 36.21 1 the preamble sequences are generated from cyclic shifts of one or several root Zadoff-Chu (ZC) sequences. Basically, there are a number of available sequences for the UE to select for use for random access in one cell. For example, in an LTE system there are 64 sequences that can be used for random access.
  • each time the UE is about to do the random access one sequence out of the 64 sequences is selected. A collision will occur if several UEs select the same sequence, and such a collision could result in random access failure for some or all UEs. Thus, the probability that multiple UEs choose the same sequence should be low. The larger the number of different available sequences, the smaller the probability of random access failure due to collision.
  • degradation of cross-correlation performance may be acceptable if the address space can be increased.
  • R1 -1700034 RACH preamble design for NR
  • R1 -1700034 RACH preamble design for NR
  • R1 -1700034 RACH preamble design for NR
  • R1 -1700034 includes a second dimension of N time shifts of a chosen M- sequence.
  • the total address space is then roughly N 2 , instead of N for traditional ZC- or M-sequences.
  • Figure 1 indicates that cross-correlation between different M-sequence shifts is uniform and low if the same ZC root is used, and becomes larger and random for different roots.
  • Figure 2 illustrates that cross-correlation between two ZC roots with the same M-sequence shift superimposed resembles the classical ZC-only cross-correlation. However, when different M-sequence shifts are applied, the cross-correlation also becomes random and uneven.
  • a method of operation of a network node in a wireless network comprises determining an operation mode for the wireless network or a part of the wireless network and determining, from at least two possible sets of synchronization sequences, based on the operation mode, a synchronization sequence set to be used by a plurality of entities in the wireless network or the part of the wireless network.
  • the at least two possible sets of synchronization sequences comprise a first set of synchronization sequences comprising a first number of synchronization sequences and a second set of synchronization sequences comprising a second number of synchronization sequences, wherein the second number is less than the first number.
  • the second set of synchronization sequences is a subset of the first set of synchronization sequences. In this manner, the first set of synchronization sequences can be used when a large number of synchronization sequences is needed; otherwise, the smaller second set of synchronization sequences can be used, which improves synchronization sequence detection.
  • a default allocation for the plurality of entities is to use the first set of synchronization sequences. In some other
  • a default allocation for the plurality of entities is to use the second set of synchronization sequences.
  • determining the operation mode for the wireless network or the part of the wireless network comprises determining the operation mode for the wireless network or the part of the wireless network based on a number of unique synchronization sequences that need to be supported. Further, in some embodiments, determining the operation mode for the wireless network or the part of the wireless network based on the number of unique synchronization sequences that need to be supported comprises determining the number of unique synchronization sequences that need to be supported based on node deployment in the wireless network or the part of the wireless network node density in the wireless network or the part of the wireless network, propagation conditions in the wireless network or the part of the wireless network, antenna array sizes used in the wireless network or the part of the wireless network, and number of current or statistical wireless devices in the wireless network or the part of the wireless device.
  • determining the synchronization sequence set to be used comprises selecting the first set of synchronization sequences if the number of unique synchronization sequences that need to be supported is greater than a threshold. In some embodiments, determining the
  • synchronization sequence set to be used comprises selecting the second set of synchronization sequences if the number of unique synchronization sequences that need to be supported is less than a threshold.
  • the first set of synchronization sequences is a ZCxM sequence set that uses cyclic versions of an M-sequence as different cover extensions of a set of cyclic-shifted Zadoff-Chu (ZC) sequences.
  • the second set of synchronization sequences is a subset of the ZCxM sequence set.
  • the subset of the ZCxM sequence set is a subset using ZC roots only without multiplication with any M-sequence.
  • the subset of the ZCxM sequence set is a subset using a fixed M-sequence and a range of ZC roots.
  • the subset of the ZCxM sequence set is: a subset of the ZCxM sequence set that uses a fixed M-sequence and a range of ZC roots, a subset using a fixed ZC root and a range of M-sequence shifts, and a subset using M-sequence shifts only.
  • the first set of synchronization sequences mixes multiple sequences comprising one or more M-sequences, one or more Gold sequences, and/or one or more Barker sequences.
  • the second set of synchronization sequences is a subset of the first set of synchronization sequences.
  • the method further comprises determining per- entity allocations for the plurality of entities, respectively, from the
  • a network node for a wireless network is adapted to determine an operation mode for the wireless network or a part of the wireless network and determine, from at least two possible sets of synchronization sequences based on the operation mode, a synchronization sequence set to be used by a plurality of entities in the wireless network or the part of the wireless network.
  • a network node for a wireless network comprises a network interface and/or at least one radio unit, at least one processor, and memory.
  • the memory stores instructions executable by the at least one processor whereby the network node is operable to determine an operation mode for the wireless network or a part of the wireless network and determine, from at least two possible sets of synchronization sequences based on the operation mode, a synchronization sequence set to be used by a plurality of entities in the wireless network or the part of the wireless network.
  • a network node for a wireless network comprises a first determining module operable to determine an operation mode for the wireless network or a part of the wireless network and a second determining module operable to determine, from at least two possible sets of synchronization sequences based on the operation mode, a synchronization sequence set to be used by a plurality of entities in the wireless network or the part of the wireless network.
  • Embodiments of a method of operation of a wireless network for synchronization sequence selection are also disclosed.
  • the method comprises determining a number of required synchronization sequences based on one or both of network conditions and a number of wireless devices in the wireless network and selecting a synchronization sequence set from at least two possible sets with different sequence set size/performance trade-offs based on the number of required synchronization sequences.
  • the method further comprises determining an allocation of the synchronization sequence set to individual entities in the wireless network and configuring the entities with the sequences according to the allocation.
  • a method of operation of a wireless device in a wireless network comprises receiving, from a network node in the wireless network, a configuration to use one or more synchronization sequences, the one or more synchronization sequences being from one of at least two sets of synchronization sequences and utilizing at least one of the one or more synchronization sequences.
  • the at least two sets of synchronization sequences comprise a first set of synchronization sequences comprising a first number of synchronization sequences and a second set of synchronization sequences comprising a second number of synchronization sequences, wherein the second number is less than the first number.
  • the second set of synchronization sequences is a subset of the first set of synchronization sequences.
  • the one of the at least two sets of synchronization sequences varies based on an operation mode of the wireless network or a part of the wireless network in which the wireless device is located. In some embodiments, the operation mode for the wireless network or the part of the wireless network is based on a number of unique
  • the number of unique synchronization sequences that need to be supported is based on node deployment in the wireless network or the part of the wireless network, node density in the wireless network or the part of the wireless network, propagation conditions in the wireless network or the part of the wireless network, antenna array sizes used in the wireless network or the part of the wireless network, and number of current or statistical wireless devices in the wireless network or the part of the wireless device.
  • the first set of synchronization sequences is a ZCxM sequence set that uses cyclic versions of an M-sequence as different cover extensions of a set of cyclic-shifted ZC sequences.
  • a default allocation for the wireless device is to use the first set of
  • a default allocation for the wireless device is to use the second set of synchronization sequences.
  • the second set of synchronization sequences is a subset of the ZCxM sequence set.
  • the subset of the ZCxM sequence set is a subset using ZC roots only without multiplication with any M-sequence.
  • the subset of the ZCxM sequence set is a subset using a fixed M-sequence and a range of ZC roots.
  • the subset of the ZCxM sequence set is: a subset of the ZCxM sequence set that uses a fixed M-sequence and a range of ZC roots, a subset using a fixed ZC root and a range of M-sequence shifts, and a subset using M-sequence shifts only.
  • the first set of synchronization sequences mixes multiple sequences comprising one or more M-sequences, one or more Gold sequences, and/or one or more Barker sequences.
  • the second set of synchronization sequences is a subset of the first set of synchronization sequences.
  • a wireless device for a wireless network is adapted to receive, from a network node in the wireless network, a
  • the one or more synchronization sequences being from one of at least two sets of
  • the wireless device is further adapted to utilize at least one of the one or more synchronization sequences.
  • a wireless device for a wireless network comprises one or more transceivers and circuitry operable to cause the wireless device to: receive, from a network node in the wireless network, a configuration to use one or more synchronization sequences, the one or more synchronization sequences being from one of at least two sets of
  • synchronization sequences and utilize at least one of the one or more synchronization sequences.
  • a wireless device for a wireless network comprises a receiving module and a utilizing module.
  • the receiving module is operable to receive, from a network node in the wireless network, a
  • the one or more synchronization sequences being from one of at least two sets of
  • the utilizing module is operable to utilize at least one of the one or more synchronization sequences.
  • Figure 1 illustrates cross-correlations with 21 M-sequence shifts, nine Zadoff-Chu (ZC) sequence shifts, and two ZC roots;
  • Figure 2 illustrates cross-correlations with 126 ZC roots and two shifts of an M-sequence;
  • Figure 3 illustrates one example of a wireless system (e.g., a cellular communications network) in which embodiments of the present disclosure may be implemented;
  • a wireless system e.g., a cellular communications network
  • Figure 4 is a flow chart that illustrates the operation of a network node according to some embodiments of the present disclosure
  • Figure 5 illustrates examples of synchronization sequence sets for different modes
  • Figure 6 is a flow chart that illustrates the operation of a wireless device according to some embodiments of the present disclosure
  • Figures 7 and 8 illustrate example embodiments of a wireless device
  • Figures 9 through 1 1 illustrate example embodiments of a network node.
  • Radio Node As used herein, a "radio node” is either a radio access node or a wireless device.
  • Radio Access Node As used herein, a “radio access node” or “radio network node” is any node in a radio access network of a cellular
  • a radio access node includes, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high- power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), and a relay node.
  • a base station e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network
  • a high- power or macro base station e.g., a micro base station, a pico base station, a home eNB, or the like
  • Core Network Node is any type of node in a core network.
  • Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P- GW), a Service Capability Exposure Function (SCEF), or the like.
  • MME Mobility Management Entity
  • P- GW Packet Data Network Gateway
  • SCEF Service Capability Exposure Function
  • Wireless Device As used herein, a “wireless device” is any type of device that has access to (i.e., is served by) a cellular communications network by wirelessly transmitting and/or receiving signals to a radio access node(s). Some examples of a wireless device include, but are not limited to, a User Equipment device (UE) in a 3GPP network and a Machine Type Communication (MTC) device.
  • UE User Equipment device
  • MTC Machine Type Communication
  • Network Node As used herein, a "network node” is any node that is either part of the radio access network or the core network of a cellular communications network/system.
  • a set of synchronization sequences allocated to UEs and/or TRPs and/or beams and/or cells is configured (e.g., dynamically) based on the required number of sequences to support in a respective usage scenario.
  • a full expanded (e.g., size-N 2 ) address space i.e., a full expanded set of synchronization sequences
  • a required number of synchronization sequences is "high" (e.g., greater than a predefined or configurable threshold). This is the case, e.g., when there are so many entities (cells, TRPs, beams, and/or UEs) that require unique
  • the original, limited-size (size-N) address space i.e., an original or non-expanded set of synchronization sequences
  • the limited-size address space is sufficient, only original, low cross-correlation sequences are allocated to, e.g., UEs and/or TRPs and/or beams and/or cells, depending on the particular implementation.
  • the set of synchronization sequences allocated is configured for either a "few-UEs mode” or a "many-UEs mode.”
  • PRACH Physical Random Access Channel
  • R1 -1700034 RACH preamble design for NR
  • 3GPP TSG-RAN WG1 NR Ad Hoc Meeting, Spokane, USA, January 16-20, 2017 hereinafter "R1 -1700034”
  • each TRP/cell is allocated one root and a subset of shifts, or one shift and a subset of roots.
  • the M-sequence component could be omitted).
  • the sequence allocation includes both multiple M-sequence shifts and multiple Zadoff-Chu (ZC) roots.
  • ZC Zadoff-Chu
  • FIG 3 illustrates one example of a wireless system 10 (e.g., a cellular communications network such as, for example, a 3GPP 5G or NR network) in which embodiments of the present disclosure may be implemented.
  • a number of wireless devices 12 e.g., UEs
  • wireless access nodes 14 e.g., gNBs
  • the radio access nodes 14 are connected to a core network 18.
  • the core network 18 includes one or more core network nodes 19 (e.g., MMEs, Serving Gateways (S-GWs), and/or the like).
  • MMEs Mobility Management Entity
  • S-GWs Serving Gateways
  • Figure 4 is a flow chart that illustrates the operation of a network node (e.g., a radio access node 14 or a core network node 19) (i.e., the operation of a control entity implemented in a network node) according to some embodiments of the present disclosure.
  • a network node e.g., a radio access node 14 or a core network node 19
  • the non-extended set of sequences is a subset of the extended set of sequences or another set of sequences that is structurally related to the extended set and has good cross- correlation properties with respect to the extended set (e.g., version of the extended set where one of the component sequences is removed).
  • the network node determines whether to allocate the full extended set of sequences or the normal non-extended set of sequences based on one or more criteria.
  • the full extended set of sequences is a ZCxM sequence set as defined in R1 -1700034.
  • the ZCxM sequence set Z uses cyclic versions of an M-sequence as different cover extensions of original, limited-size LTE quasi-orthogonal sequences S, and can be written mathematically as: where is tne set of original cyclic-shifted ZC sequences, in which each sequence is written as
  • N CJ ,2N cs ,- - - ⁇ (N zc -l) represents cyclic shifts of a root ZC sequence with cyclic shift gap N cs .
  • T h ⁇ w(k + is a cover extension of the original set S obtained by multiplying all sequences in S with a common M-sequence cyclic-shifted by h .
  • a binary M-sequence can be defined as
  • « is a primitive element of the Galois field GF(2 m ) .
  • the ZCxM sequence set Z is only one example of the full extended sequence set.
  • Many other design options can be designed according to the same principles, e.g., mixing multiple M-sequences, Gold sequences, Barker sequences, and other synchronization sequences.
  • Extended sequences can be formed according to, e.g., principles ⁇ M1 -sequence x M2- sequence ⁇ , ⁇ Goldl sequence x Gold2 sequence ⁇ , and ⁇ M-sequence x Gold sequence ⁇ , etc.
  • the normal, or non-extended, set of sequences is the sequence set S (i.e., the set of original cyclic-shifted ZC sequences).
  • a set of possible operation modes includes a few- entities (e.g., few UEs and/or TRPs and/or cells and/or beams) operation mode and a many-entities (e.g., a many UEs and/or TRPs and/or cells and/or beams) operation mode.
  • a few- entities e.g., few UEs and/or TRPs and/or cells and/or beams
  • a many-entities e.g., a many UEs and/or TRPs and/or cells and/or beams
  • the network node i.e., the control entity implemented in the network node
  • statistical data can be used to determine the number of wireless devices 12 in the relevant part(s) of the network since the instantaneous exact number may be unknown.
  • the network knows the number of wireless devices 12 currently in the relevant part(s) of the network or the handover process.
  • some statistical averaging may be performed since mode switching (e.g., switching between the few-entities mode and the many-entities mode) is preferably performed infrequently, at the time scale of, e.g., at least tens of minutes or hours.
  • the mode may be determined based on wireless device density (e.g., cell density, beam density, TRP density, and/or wireless device density).
  • wireless device density e.g., cell density, beam density, TRP density, and/or wireless device density
  • the mode may be determined in step 100 based on the number of TRPs and/or the number of cells and/or the number of beams per unit area (e.g., in the case of Primary Synchronization Signal (PSS)) or the number of wireless devices per TRP or cell group, per TRP or cell, per beam, etc., in the order of likelihood.
  • PSS Primary Synchronization Signal
  • the mode is selected independently in different regions or parts of the network, e.g., a set of TRPs served by the same node (e.g., baseband unit), the density in this particular region may be used as the relevant information for determining the mode.
  • the density in this particular region may be used as the relevant information for determining the mode.
  • determining the mode is a question of (1 ) how many sequences the non-expanded set supports and (2) how many wireless devices there are in the system - or trying to access the system - that need unique sequences.
  • (1 ) is given by the signal design and is known ahead of time.
  • (2) may be determined by, e.g., statistics (e.g., historical access volumes at the same period during the day/week).
  • the instantaneous (recent) access volumes may be used. In that case, if the number of actually utilized sequences is robustly lower than the non-expanded set size, the latter may be invoked. If it exceeds a heuristic robustness threshold, e.g. the rate of PRACH failures due to sequence collisions, the expanded set is employed.
  • the network node determines the sequence (sub)set to use based on the determined operation mode (step 102).
  • the full extended set of sequences may be utilized when in the many-entities mode, as determined in step 100.
  • a subset of the full extended sequence set i.e., the normal non-extended set
  • the normal non-extended set is a subset of the full extended set of sequences where only one of the component sequences is varying, or where one of the component sequences is removed. This is elaborated upon below.
  • steps 100 and 102 are described above in terms of the operation mode, steps 100 and 102 can also be described as follows.
  • the operation mode is determined. In some embodiments, this can also be described as determining a number of required synchronization sequences, e.g., based on network conditions and/or the number of wireless devices in the wireless network or the relevant part of the wireless network.
  • Step 102 can then be described as, in some embodiments, selecting a synchronization sequence set from at least two possible sets with different sequence set sizes and/or performance trade-offs based on the number of required synchronization sequences.
  • the network node divides the total set of available sequences (as determined in step 102) among the entities (UEs and/or TRPs and/or cells and/or beams), preferably according to some systematic structure (step 1 04).
  • one entity e.g., a cell
  • one of the sequences is constant in the many-entities mode, or a contiguous subset of the optimal, single-component sequence set.
  • the network node allocates the sequences to the entities and configures the entities for operation using the allocated sequences via control signaling protocols, similar to legacy solutions (step 106).
  • the PRACH preamble sequence allocation to the UE is achieved via initial System Information (SI) in Master Information Block (MIB) or the Physical Broadcasting Channel (PBCH) or Remaining Minimum SI (RMSI) transmission, mobility measurement signals via node-to-UE Radio Resource Control (RRC) signaling, while the control entity may inform other network nodes via node-to- node RRC signaling.
  • SI System Information
  • MIB Master Information Block
  • PBCH Physical Broadcasting Channel
  • RRC Radio Resource Control
  • the various entities use the allocated and configured sequences for, e.g., synchronization/detection/measurements.
  • the default allocation may be to use many- entity sequence sets to all UEs and/or TRPs and/or cells and/or beams as the starting point.
  • step 102 may amount to identifying UE, TRP, cell, or beam groups for which the large set is
  • Those groups are then allocated few-entities subsets and the UEs, TRPs, cells, or beams are allocated sections of the subset as described below.
  • step 102 identifies UE, TRP, cell, or beam groups for which large sets are required, e.g., due to dense cell deployment where the UE can hear many cells at a time, or a large number of UEs in the system. Those groups are then allocated many-entities subsets.
  • the sequence set for few-entities mode may be a subset of the full extended sequence set for the many-entities mode or a separate set of sequences.
  • the few-entities mode sequence set selection can be depicted as shown in Figure 5.
  • the full set of hashed circles represents the full extended synchronization sequence set for the many- entities mode. Each circle corresponds to a length-N sequence.
  • the following subsets of the full extended synchronization sequence set can be defined as sequence sets for the few-entities mode:
  • a second subset type that corresponds to omitting multiplication with the M-sequence altogether, which is equivalent to assuming a trivial, all-ones M-sequence that is near-orthogonal with all other M-sequence primitive polynomials and shifts. This may be the preferred selection scheme due to best cross-correlation properties within the set.
  • a third subset type that corresponds to selecting a fixed ZC root and a range of M-sequence shifts as the subset.
  • the selected subset can then be allocated to multiple UEs and/or TRPs and/or cells and/or beams so that each entity is allowed to use a predetermined number of subset elements, e.g., certain ZC roots or M- sequence shifts.
  • this corresponds to allocating sections of the selected row/column to each UE and/or TRP and/or cell and/or beam.
  • the delays of the sequences can be assumed to be zero such that the cross-correlations between sequences are only evaluated without delays between sequences.
  • one M-sequence and one set of several different root sequences of ZC are allocated for all the UEs within one cell. This corresponds to the first 1 26 indices in Figure 2.
  • ZC sequences are known to have very good cross-correlation properties and correspond to one column in Figure 5.
  • Different cells can have different M- sequences.
  • received signal strength from UEs in other cells are lower (in average) as compared to signals from UEs within the same cell. Due to these power reductions, having low cross-correlations between cells is not as important as low cross-correlations between sequences from UEs within the cell or a TRP.
  • one M-sequence and one set of several different root sequences of ZC are allocated for all the UEs within one beam.
  • the spatial separations between the UEs in the different beams will improve detection in terms of false detections between the beams. This is because received signal strength from UEs in other beams are lower (in average) as compared to signals from UEs within the same beam.
  • Figure 4 is a flow chart that illustrates the operation of a network node
  • Figure 6 illustrates the corresponding operation of a wireless device 12 according to embodiments of the present disclosure.
  • the network node determines a per-entity allocation for each of multiple entities in the wireless network and configures those entities.
  • Those entities may include other network nodes (e.g., a radio access node(s) 14) and wireless devices 12.
  • a wireless device 12 receives a configuration from a network node to use one or more synchronization sequences, where the one or more synchronization sequences are from one of at least two sets of synchronization sequences as described above (step 200).
  • the wireless device 12 utilizes at least one of the one or more synchronization sequences with which it is configured (step 202). For example, if the synchronization sequences are synchronization sequences used as Random Access Channel (RACH) preambles, the wireless device 12 selects and uses one of the configured synchronization sequences for RACH.
  • RACH Random Access Channel
  • RACH preamble is only one example use of the configured synchronization sequence(s). Many other examples for both downlink and uplink scenarios are disclosed herein.
  • R1 -1700298 NR PRACH Design
  • 3GPP TSG-RAN WG1 NR adhoc, Spokane, USA January 16-20, 2017
  • R1 -1700298 That design achieves various performance advantages by using repeated transmission of a short uplink sequence. Due to the length of the short symbols, the address space (the number of unique sequences) is shorter than the design used in LTE. The natural address space is sufficient in many cases, but possibly not all. By applying the present disclosure, the fraction of the network where lower-performing sequences are used is limited.
  • Some examples of applying embodiments of the present disclosure in the downlink may be the cell synchronization signal (PSS / Secondary
  • Synchronization Signal in LTE
  • MRSs Mobility Reference Signals
  • Such signals may need to be unique per individual nodes/cells/TRPs/beams, or in some embodiments additionally per individual UEs.
  • the sequence set selection according to the present disclosure may be static or long-term, based on node deployments, antenna array sizes, and long-term statistics of the number of UEs in the parts of the network.
  • the selection may be dynamic, e.g., responsive to the time-varying presence of UEs in the system.
  • Different parts (regions/areas, neighborhoods, node clusters, TRP groups) of the network may use different operating modes and different sequences set types. At the boundaries of such regions, the different types of sequences can still be separated since their cross-correlation properties are acceptable (although they may be suboptimal).
  • Embodiments of the present disclosure have been described using the ZCxM sequence design as an example. However, many other design options can be designed according to the same principles - mixing multiple M- sequences, Gold sequences, Barker sequences, and other synchronization sequences. Extended sequences can be formed according to principles ⁇ M1 - sequence x M2-sequence ⁇ , ⁇ Goldl sequence x Gold2 sequence ⁇ , and ⁇ M- sequence x Gold sequence ⁇ , etc.
  • Embodiments of the present disclosure are also applicable when multiple component sequences are used to create a composite sequence with larger address space, e.g., by using the available sequences to send two shorter sequences.
  • the baseline design is to transmit one length-63 M-sequence in 63 resource elements.
  • two length-31 M-sequences can be transmitted instead, yielding a product address space of 961 .
  • detection performance of the expanded design is not as good as the original single sequence.
  • This example provides an alternative example of address space - performance trade-off and a sequence set selection opportunity to prioritize one or the other, depending on network conditions.
  • FIG. 7 is a schematic block diagram of the wireless device 12 (e.g., UE) according to some embodiments of the present disclosure.
  • the wireless device 12 includes circuitry 20 comprising one or more processors 22 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), Digital Signal Processors (DSPs), and/or the like) and memory 24.
  • the wireless device 12 also includes one or more transceivers 26 each including one or more
  • the functionality of the wireless device 12 described above may be implemented in hardware (e.g., via hardware within the circuitry 20 and/or within the processor(s) 22) or be implemented in a combination of hardware and software (e.g., fully or partially implemented in software that is, e.g., stored in the memory 24 and executed by the processor(s) 22).
  • a computer program including instructions which, when executed by the at least one processor 22, causes the at least one processor 22 to carry out at least some of the functionality of the wireless device 12 according to any of the embodiments described herein is provided.
  • a carrier containing the aforementioned computer program product is provided.
  • the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).
  • FIG 8 is a schematic block diagram of the wireless device 12 (e.g., UE) according to some other embodiments of the present disclosure.
  • the wireless device 12 includes one or more modules 34, each of which is
  • the module(s) 34 provide the functionality of the wireless device 12 described herein.
  • the modules 34 include, in some embodiments, a receiving module operable to receive a configuration from the network node as described above with respect to, e.g., step 200 of Figure 6 and a utilizing module operable to use at least one of the two configured synchronization sequences as described above with respect to, e.g., step 202 of Figure 6.
  • FIG. 9 is a schematic block diagram of a network node 36 (e.g., a radio access node 14 such as, for example, a gNB or a network node such as a core network node 19) according to some embodiments of the present disclosure.
  • the network node 36 includes a control system 38 that includes circuitry comprising one or more processors 40 (e.g., CPUs, ASICs, DSPs, FPGAs, and/or the like) and memory 42.
  • the control system 38 also includes a network interface 44.
  • the network node 36 is a radio access node 14
  • the network node 36 also includes one or more radio units 46 that each include one or more transmitters 48 and one or more receivers 50 coupled to one or more antennas 52.
  • the functionality of the network node 36 e.g., the functionality of the radio access node 14 described above may be fully or partially implemented in software that is, e.g., stored in the memory 42 and executed by the processor(s) 40.
  • FIG. 10 is a schematic block diagram that illustrates a virtualized embodiment of the network node 36 (e.g., the radio access node 14 or core network node 19) according to some embodiments of the present disclosure.
  • a "virtualized" network node 36 is a network node 36 in which at least a portion of the functionality of the network node 36 is implemented as a virtual component (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)).
  • the network node 36 optionally includes the control system 38, as described with respect to Figure 9.
  • the network node 36 is the radio access node 14
  • the network node 36 also includes the one or more radio units 46, as described with respect to Figure 9.
  • the control system 38 (if present) is connected to one or more processing nodes 54 coupled to or included as part of a network(s) 56 via the network interface 44.
  • the one or more radio units 46 (if present) are connected to the one or more processing nodes 54 via a network interface(s).
  • all of the functionality of the network node 36 described herein may be implemented in the processing nodes 54 (i.e., the network node 36 does not include the control system 38 or the radio unit(s) 46).
  • Each processing node 54 includes one or more processors 58 (e.g., CPUs, ASICs, DSPs, FPGAs, and/or the like), memory 60, and a network interface 62.
  • functions 64 of the network node 36 described herein are implemented at the one or more processing nodes 54 or distributed across the control system 38 (if present) and the one or more processing nodes 54 in any desired manner.
  • some or all of the functions 64 of the network node 36 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 54.
  • additional signaling or communication between the processing node(s) 54 and the control system 38 (if present) or alternatively the radio unit(s) 46 (if present) is used in order to carry out at least some of the desired functions.
  • the control system 38 may not be included, in which case the radio unit(s) 46 (if present) communicates directly with the processing node(s) 54 via an appropriate network interface(s).
  • higher layer functionality e.g., layer 3 and up and possibly some of layer 2 of the protocol stack
  • the network node 36 may be implemented at the processing node(s) 54 as virtual components (i.e., implemented "in the cloud")
  • lower layer functionality e.g., layer 1 and possibly some of layer 2 of the protocol stack
  • a computer program including instructions which, when executed by the at least one processor 40, 58, causes the at least one processor 40, 58 to carry out the functionality of the network node 36 or a processing node 54 according to any of the embodiments described herein is provided.
  • a carrier containing the aforementioned computer program product is provided.
  • the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as the memory 42, 60).
  • Figure 1 1 is a schematic block diagram of the network node 36 (e.g., the radio access node 14 or a core network node 19) according to some other embodiments of the present disclosure.
  • the network node 36 includes one or more modules 66, each of which is implemented in software.
  • the module(s) 66 provide the functionality of the network node 36 described herein.
  • the module(s) 66 may comprise, for example, a first determining module operable to perform the function of step 100 of Figure 4, a second determining module operable to perform the function of step 102 of Figure 4, a third determining module (optional) operable to perform the function of step 104 of Figure 4, and an allocating and configuring module (optional) operable to perform the function of step 106 of Figure 4.
  • Embodiment 1 A method in a wireless network (10) for synchronization sequence selection, comprising: determining a number of required synchronization sequences based on one or both of network
  • Embodiment 2 The method of embodiment 1 further comprising determining an allocation of the synchronization sequence set to individual entities in the wireless network (10); and configuring the entities with the sequences according to the allocation.
  • Embodiment 3 A method of operation of a network node (14, 19) in a wireless network (10), comprising: determining (100) an operation mode for the wireless network (10) or a part of the wireless network (10); and
  • Embodiment 4 The method of embodiment 3 wherein the at least two possible sets of synchronization sequences comprise: a first set of synchronization sequences comprising a first number of synchronization sequences; and a second set of synchronization sequences comprising a second number of synchronization sequences, wherein the second number is less than the first number.
  • Embodiment 5 The method of embodiment 4 wherein determining (100) the operation mode for the wireless network (10) or the part of the wireless network (10) comprises determining (1 00) the operation mode for the wireless network (10) or the part of the wireless network (10) based on a number of unique synchronization sequences that need to be supported.
  • Embodiment 6 The method of embodiment 5 wherein determining (100) the operation mode for the wireless network (10) or the part of the wireless network (1 0) based on the number of unique synchronization
  • sequences that need to be supported comprises determining the number of unique synchronization sequences that need to be supported based on node deployment in the wireless network (1 0) or the part of the wireless network (10), node density in the wireless network (10) or the part of the wireless network (10), propagation conditions in the wireless network (10) or the part of the wireless network (10), antenna array sizes used in the wireless network (10) or the part of the wireless network (10), and number of current or statistical wireless devices (12) in the wireless network (10) or the part of the wireless device (10).
  • Embodiment 7 The method of embodiment 6 wherein determining (102) the synchronization sequence set to be used comprises selecting the first set of synchronization sequences if the number of unique synchronization sequences that need to be supported is greater than a threshold.
  • Embodiment 8 The method of embodiment 6 or 7 wherein
  • determining (102) the synchronization sequence set to be used comprises selecting the second set of synchronization sequences if the number of unique synchronization sequences that need to be supported is less than a threshold.
  • Embodiment 9 The method of any one of embodiments 4 to 8 wherein the first set of synchronization sequences is a ZCxM sequence set that uses cyclic versions of an M-sequence as different cover extensions of a set of cyclic-shifted ZC sequences.
  • Embodiment 10 The method of embodiment 9 wherein the second set of synchronization sequences is a subset of the ZCxM sequence set.
  • Embodiment 1 1 The method of embodiment 10 wherein the subset of the ZCxM sequence set is: a subset of the ZCxM sequence set that uses a fixed M-sequence and a range of ZC roots, a subset using ZC roots only, a subset using a fixed ZC root and a range of M-sequence shifts, and a subset using M- sequence shifts only.
  • Embodiment 12 The method of any one of embodiments 4 to 8 wherein the first set of synchronization sequences mixes multiple sequences comprising one or more M-sequences, one or more Gold sequences, and/or one or more Barker sequences.
  • Embodiment 13 The method of embodiment 12 wherein the second set of synchronization sequences is a subset of the first set of synchronization sequences.
  • Embodiment 14 A network node (14, 19, 36) for a wireless network (10) adapted to perform the method of any one of embodiments 1 to 13.
  • Embodiment 15 A network node (14, 19, 36) for a wireless network (10), comprising: a network interface (44, 62) and/or at least one radio unit (46); at least one processor (40, 58); and memory (42, 60) storing instructions executable by the at least one processor (40, 58) whereby the network node (14, 19, 36) is operable to perform the method of any one of embodiments 1 to 13.
  • Embodiment 16 A network node (14, 19, 36) for a wireless network (10), comprising: one or more modules (66) operable to perform the method of any one of embodiments 1 to 13.

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  • Computer Networks & Wireless Communication (AREA)
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  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne des systèmes et des procédés pour déterminer et configurer des séquences de synchronisation pour des entités dans un réseau sans fil à partir de différents ensembles de séquences de synchronisation en fonction, par exemple, des conditions de réseau et/ou du nombre de dispositifs sans fil. Dans certains modes de réalisation, un procédé de fonctionnement d'un nœud de réseau dans un réseau sans fil comprend la détermination d'un mode de fonctionnement pour le réseau sans fil ou d'une partie du réseau sans fil et la détermination, à partir d'au moins deux ensembles possibles de séquences de synchronisation sur la base du mode de fonctionnement, d'un ensemble de séquences de synchronisation à utiliser par une pluralité d'entités dans le réseau sans fil ou la partie du réseau sans fil. Dans certains modes de réalisation, ceci permet d'utiliser un ensemble étendu de séquences de synchronisation lorsqu'un grand nombre de séquences de synchronisation est nécessaire ; sinon, un ensemble plus petit non étendu de séquences de synchronisation peut être utilisé, ce qui améliore la détection de la séquence de synchronisation.
PCT/SE2017/050909 2017-02-06 2017-09-15 Attribution de séquence de synchronisation flexible WO2018143847A1 (fr)

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