WO2019033327A1 - Techniques et appareils permettant d'identifier une cellule candidate pour le rétablissement d'une connexion radio - Google Patents

Techniques et appareils permettant d'identifier une cellule candidate pour le rétablissement d'une connexion radio Download PDF

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Publication number
WO2019033327A1
WO2019033327A1 PCT/CN2017/097795 CN2017097795W WO2019033327A1 WO 2019033327 A1 WO2019033327 A1 WO 2019033327A1 CN 2017097795 W CN2017097795 W CN 2017097795W WO 2019033327 A1 WO2019033327 A1 WO 2019033327A1
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WIPO (PCT)
Prior art keywords
base station
target cell
radio connection
user equipment
cell
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PCT/CN2017/097795
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English (en)
Inventor
Feng Chen
Peng Hu
Xuepan GUAN
Xiaochen Chen
Zhibin DANG
Lu Bai
Yong Hou
Jun Deng
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Qualcomm Incorporated
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Priority to PCT/CN2017/097795 priority Critical patent/WO2019033327A1/fr
Publication of WO2019033327A1 publication Critical patent/WO2019033327A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/19—Connection re-establishment
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/24—Reselection being triggered by specific parameters
    • H04W36/30—Reselection being triggered by specific parameters by measured or perceived connection quality data
    • H04W36/305—Handover due to radio link failure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W48/00—Access restriction; Network selection; Access point selection
    • H04W48/16—Discovering, processing access restriction or access information

Definitions

  • aspects of the present disclosure generally relate to wireless communication, and more particularly to techniques and apparatuses for identifying a candidate cell for radio connection reestablishment.
  • Wireless communication systems are widely deployed to provide various telecommunication services, such as telephony, video, data, messaging, and broadcasts.
  • Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, and/or the like) .
  • multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency divisional multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
  • CDMA code division multiple access
  • TDMA time division multiple access
  • FDMA frequency division multiple access
  • OFDMA orthogonal frequency division multiple access
  • SC-FDMA single-carrier frequency divisional multiple access
  • TD-SCDMA time division synchronous code division multiple access
  • LTE Long Term Evolution
  • UMTS Universal Mobile Telecommunications System
  • 3GPP Third Generation Partnership Project
  • LTE is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, using new spectrum, and integrating with other open standards using OFDMA on the downlink (DL) , SC-FDMA on the uplink (UL) , and multiple-input multiple-output (MIMO) antenna technology.
  • a method of wireless communication performed by a user equipment may include identifying a target cell for radio connection reestablishment using stored information identifying at least one base station that stores a radio connection context of the user equipment, wherein the target cell is provided by a particular base station of the at least one base station, and wherein the stored information is determined by the user equipment; and performing radio connection reestablishment with regard to the target cell.
  • a user equipment may include a memory and one or more processors operatively coupled to the memory.
  • the one or more processors may be configured to identify a target cell for radio connection reestablishment using stored information identifying at least one base station that stores a radio connection context of the user equipment, wherein the target cell is provided by a particular base station of the at least one base station, and wherein the stored information is determined by the user equipment; and perform radio connection reestablishment with regard to the target cell.
  • a non-transitory computer-readable medium may store one or more instructions for wireless communication.
  • the one or more instructions when executed by one or more processors of a user equipment, may cause the one or more processors to identify a target cell for radio connection reestablishment using stored information identifying at least one base station that stores a radio connection context of the user equipment, wherein the target cell is provided by a particular base station of the at least one base station, and wherein the stored information is determined by the user equipment; and perform radio connection reestablishment with regard to the target cell.
  • an apparatus for wireless communication may include means for identifying a target cell for radio connection reestablishment using stored information identifying at least one base station that stores a radio connection context of the apparatus, wherein the target cell is provided by a particular base station of the at least one base station, and wherein the stored information is determined by the apparatus; and means for performing radio connection reestablishment with regard to the target cell.
  • Fig. 1 is a diagram illustrating an example deployment in which multiple wireless networks have overlapping coverage, in accordance with various aspects of the present disclosure.
  • Fig. 2 is a diagram illustrating an example access network in an LTE network architecture, in accordance with various aspects of the present disclosure.
  • Fig. 3 is a diagram illustrating an example of a downlink frame structure in LTE, in accordance with various aspects of the present disclosure.
  • Fig. 4 is a diagram illustrating an example of an uplink frame structure in LTE, in accordance with various aspects of the present disclosure.
  • Fig. 5 is a diagram illustrating an example of a radio protocol architecture for a user plane and a control plane in LTE, in accordance with various aspects of the present disclosure.
  • Fig. 6 is a diagram illustrating example components of an evolved Node B and a user equipment in an access network, in accordance with various aspects of the present disclosure.
  • Figs. 7A and 7B are diagrams illustrating examples of identifying a candidate cell for radio connection reestablishment, in accordance with various aspects of the present disclosure.
  • Fig. 8 is a diagram illustrating an example process performed, for example, by a wireless communication device, in accordance with various aspects of the present disclosure.
  • CDMA code division multiple access
  • TDMA time division multiple access
  • FDMA frequency division multiple access
  • OFDMA orthogonal FDMA
  • SC-FDMA single carrier FDMA
  • a CDMA network may implement a radio access technology (RAT) such as universal terrestrial radio access (UTRA) , CDMA2000, and/or the like.
  • RAT radio access technology
  • UTRA may include wideband CDMA (WCDMA) and/or other variants of CDMA.
  • CDMA2000 may include Interim Standard (IS) -2000, IS-95 and IS-856 standards.
  • IS-2000 may also be referred to as 1x radio transmission technology (1xRTT) , CDMA2000 1X, and/or the like.
  • a TDMA network may implement a RAT such as global system for mobile communications (GSM) , enhanced data rates for GSM evolution (EDGE) , or GSM/EDGE radio access network (GERAN) .
  • GSM global system for mobile communications
  • EDGE enhanced data rates for GSM evolution
  • GERAN GSM/EDGE radio access network
  • An OFDMA network may implement a RAT such as evolved UTRA (E-UTRA) , ultra mobile broadband (UMB) , Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDM, and/or the like.
  • E-UTRA evolved UTRA
  • UMB ultra mobile broadband
  • IEEE Institute of Electrical and Electronics Engineers
  • Wi-Fi Wi-Fi
  • WiMAX IEEE 802.16
  • UTRA and E-UTRA may be part of the universal mobile telecommunication system (UMTS) .
  • 3GPP long-term evolution (LTE) and LTE-Advanced (LTE-A) are example releases of UMTS that use E-UTRA, which employs OFDMA on the downlink and SC-FDMA on the uplink.
  • UTRA, E-UTRA, UMTS, LTE, LTE-Aand GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP) .
  • CDMA2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) .
  • the techniques described herein may be used for the wireless networks and RATs mentioned above as well as other wireless networks and RATs.
  • Fig. 1 is a diagram illustrating an example deployment 100 in which multiple wireless networks have overlapping coverage, in accordance with various aspects of the present disclosure. However, wireless networks may not have overlapping coverage in aspects.
  • example deployment 100 may include an evolved universal terrestrial radio access network (E-UTRAN) 105, which may include one or more evolved Node Bs (eNBs) 110, and which may communicate with other devices or networks via a serving gateway (SGW) 115 and/or a mobility management entity (MME) 120.
  • E-UTRAN evolved universal terrestrial radio access network
  • eNBs evolved Node Bs
  • MME mobility management entity
  • example deployment 100 may include a radio access network (RAN) 125, which may include one or more base stations 130, and which may communicate with other devices or networks via a mobile switching center (MSC) 135 and/or an inter-working function (IWF) 140.
  • example deployment 100 may include one or more user equipment (UEs) 145 capable of communicating via E-UTRAN 105 and/or RAN 125.
  • E-UTRAN 105 may support, for example, LTE or another type of RAT.
  • E-UTRAN 105 may include eNBs 110 and other network entities that can support wireless communication for UEs 145.
  • Each eNB 110 may provide communication coverage for a particular geographic area.
  • the term “cell” may refer to a coverage area of eNB 110 and/or an eNB subsystem serving the coverage area on a specific frequency channel.
  • SGW 115 may communicate with E-UTRAN 105 and may perform various functions, such as packet routing and forwarding, mobility anchoring, packet buffering, initiation of network-triggered services, and/or the like.
  • MME 120 may communicate with E-UTRAN 105 and SGW 115 and may perform various functions, such as mobility management, bearer management, distribution of paging messages, security control, authentication, gateway selection, and/or the like, for UEs 145 located within a geographic region served by MME 120 of E-UTRAN 105.
  • E-UTRA Evolved Universal Terrestrial Radio Access
  • E-UTRAN Evolved Universal Terrestrial Radio Access Network
  • RAN 125 may support, for example, GSM or another type of RAT.
  • RAN 125 may include base stations 130 and other network entities that can support wireless communication for UEs 145.
  • MSC 135 may communicate with RAN 125 and may perform various functions, such as voice services, routing for circuit-switched calls, and mobility management for UEs 145 located within a geographic region served by MSC 135 of RAN 125.
  • IWF 140 may facilitate communication between MME 120 and MSC 135 (e.g., when E-UTRAN 105 and RAN 125 use different RATs) .
  • MME 120 may communicate directly with an MME that interfaces with RAN 125, for example, without IWF 140 (e.g., when E-UTRAN 105 and RAN 125 use a same RAT) .
  • E-UTRAN 105 and RAN 125 may use the same frequency and/or the same RAT to communicate with UE 145.
  • E-UTRAN 105 and RAN 125 may use different frequencies and/or RATs to communicate with UEs 145.
  • the term base station is not tied to any particular RAT, and may refer to an eNB (e.g., of an LTE network) or another type of base station associated with a different type of RAT.
  • any number of wireless networks may be deployed in a given geographic area.
  • Each wireless network may support a particular RAT and may operate on one or more frequencies.
  • a RAT may also be referred to as a radio technology, an air interface, and/or the like.
  • a frequency or frequency ranges may also be referred to as a carrier, a frequency channel, and/or the like.
  • Each frequency or frequency range may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs.
  • UE 145 may be stationary or mobile and may also be referred to as a mobile station, a terminal, an access terminal, a wireless communication device, a subscriber unit, a station, and/or the like.
  • UE 145 may be a cellular phone, a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, and/or the like.
  • PDA personal digital assistant
  • WLL wireless local loop
  • UE 145 may be included inside a housing 145’ that houses components of UE 145, such as processor components, memory components, and/or the like.
  • UE 145 may search for wireless networks from which UE 145 can receive communication services. If UE 145 detects more than one wireless network, then a wireless network with the highest priority may be selected to serve UE 145 and may be referred to as the serving network. UE 145 may perform registration with the serving network, if necessary. UE 145 may then operate in a connected mode to actively communicate with the serving network. Alternatively, UE 145 may operate in an idle mode and camp on the serving network if active communication is not required by UE 145.
  • UE 145 may operate in the idle mode as follows. UE 145 may identify all frequencies/RATs on which it is able to find a “suitable” cell in a normal scenario or an “acceptable” cell in an emergency scenario, where “suitable” and “acceptable” are specified in the LTE standards. UE 145 may then camp on the frequency/RAT with the highest priority among all identified frequencies/RATs. UE 145 may remain camped on this frequency/RAT until either (i) the frequency/RAT is no longer available at a predetermined threshold or (ii) another frequency/RAT with a higher priority reaches this threshold.
  • UE 145 may receive a neighbor list when operating in the idle mode, such as a neighbor list included in a system information block type 5 (SIB 5) provided by an eNB of a RAT on which UE 145 is camped. Additionally, or alternatively, UE 145 may generate a neighbor list.
  • a neighbor list may include information identifying one or more frequencies, at which one or more RATs may be accessed, priority information associated with the one or more RATs, and/or the like.
  • the number and arrangement of devices and networks shown in Fig. 1 are provided as an example. In practice, there may be additional devices and/or networks, fewer devices and/or networks, different devices and/or networks, or differently arranged devices and/or networks than those shown in Fig. 1. Furthermore, two or more devices shown in Fig. 1 may be implemented within a single device, or a single device shown in Fig. 1 may be implemented as multiple, distributed devices. Additionally, or alternatively, a set of devices (e.g., one or more devices) shown in Fig. 1 may perform one or more functions described as being performed by another set of devices shown in Fig. 1.
  • Fig. 2 is a diagram illustrating an example access network 200 in an LTE network architecture, in accordance with various aspects of the present disclosure.
  • access network 200 may include one or more eNBs 210 (sometimes referred to as “base stations” herein) that serve a corresponding set of cellular regions (cells) 220, one or more low power eNBs 230 that serve a corresponding set of cells 240, and a set of UEs 250.
  • eNBs 210 sometimes referred to as “base stations” herein
  • base stations low power eNBs 230 that serve a corresponding set of cells 240
  • UEs 250 a set of UEs 250.
  • Each eNB 210 may be assigned to a respective cell 220 and may be configured to provide an access point to a RAN.
  • eNB 110, 210 may provide an access point for UE 145, 250 to E-UTRAN 105 (e.g., eNB 210 may correspond to eNB 110, shown in Fig. 1) or may provide an access point for UE 145, 250 to RAN 125 (e.g., eNB 210 may correspond to base station 130, shown in Fig. 1) .
  • the terms base station and eNB may be used interchangeably, and a base station, as used herein, is not tied to any particular RAT.
  • UE 145, 250 may correspond to UE 145, shown in Fig. 1.
  • the eNBs 210 may perform radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and network connectivity (e.g., to SGW 115) .
  • one or more low power eNBs 230 may serve respective cells 240, which may overlap with one or more cells 220 served by eNBs 210.
  • the eNBs 230 may correspond to eNB 110 associated with E-UTRAN 105 and/or base station 130 associated with RAN 125, shown in Fig. 1.
  • a low power eNB 230 may be referred to as a remote radio head (RRH) .
  • the low power eNB 230 may include a femto cell eNB (e.g., home eNB (HeNB) ) , a pico cell eNB, a micro cell eNB, and/or the like.
  • HeNB home eNB
  • a modulation and multiple access scheme employed by access network 200 may vary depending on the particular telecommunications standard being deployed.
  • OFDM orthogonal frequency division multiplexing
  • SC-FDMA is used on the uplink (UL) to support both frequency division duplexing (FDD) and time division duplexing (TDD) .
  • FDD frequency division duplexing
  • TDD time division duplexing
  • the various concepts presented herein are well suited for LTE applications. However, these concepts may be readily extended to other telecommunication standards employing other modulation and multiple access techniques. By way of example, these concepts may be extended to Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB) .
  • EV-DO Evolution-Data Optimized
  • UMB Ultra Mobile Broadband
  • EV-DO and UMB are air interface standards promulgated by the 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations.
  • 3GPP2 3rd Generation Partnership Project 2
  • these concepts may also be extended to UTRA employing WCDMA and other variants of CDMA (e.g., such as TD-SCDMA, GSM employing TDMA, E-UTRA, and/or the like) , UMB, IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDM employing OFDMA, and/or the like.
  • WCDMA Wideband Code Division Multiple Access
  • UMB Universal Mobile Broadband Code Division Multiple Access 2000
  • CDMA2000 and UMB are described in documents from the 3GPP2 organization.
  • the actual wireless communication standard and the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system.
  • the eNBs 210 may have multiple antennas supporting MIMO technology.
  • MIMO technology enables eNBs 210 to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity.
  • Spatial multiplexing may be used to transmit different streams of data simultaneously on the same frequency.
  • the data streams may be transmitted to a single UE 145, 250 to increase the data rate or to multiple UEs 250 to increase the overall system capacity. This may be achieved by spatially precoding each data stream (e.g., applying a scaling of an amplitude and a phase) and then transmitting each spatially precoded stream through multiple transmit antennas on the DL.
  • the spatially precoded data streams arrive at the UE (s) 250 with different spatial signatures, which enables each of the UE (s) 250 to recover the one or more data streams destined for that UE 145, 250.
  • each UE 145, 250 transmits a spatially precoded data stream, which enables eNBs 210 to identify the source of each spatially precoded data stream.
  • Beamforming may be used to focus the transmission energy in one or more directions. This may be achieved by spatially precoding the data for transmission through multiple antennas. To achieve good coverage at the edges of the cell, a single stream beamforming transmission may be used in combination with transmit diversity.
  • OFDM is a spread-spectrum technique that modulates data over a number of subcarriers within an OFDM symbol.
  • the subcarriers are spaced apart at precise frequencies. The spacing provides “orthogonality” that enables a receiver to recover the data from the subcarriers.
  • a guard interval e.g., cyclic prefix
  • the UL may use SC- FDMA in the form of a DFT-spread OFDM signal to compensate for high peak-to-average power ratio (PAPR) .
  • PAPR peak-to-average power ratio
  • the number and arrangement of devices and cells shown in Fig. 2 are provided as an example. In practice, there may be additional devices and/or cells, fewer devices and/or cells, different devices and/or cells, or differently arranged devices and/or cells than those shown in Fig. 2. Furthermore, two or more devices shown in Fig. 2 may be implemented within a single device, or a single device shown in Fig. 2 may be implemented as multiple, distributed devices. Additionally, or alternatively, a set of devices (e.g., one or more devices) shown in Fig. 2 may perform one or more functions described as being performed by another set of devices shown in Fig. 2.
  • Fig. 3 is a diagram illustrating an example 300 of a downlink (DL) frame structure in LTE, in accordance with various aspects of the present disclosure.
  • a frame e.g., of 10 ms
  • Each sub-frame may include two consecutive time slots.
  • a resource grid may be used to represent two time slots, each time slot including a resource block (RB) .
  • the resource grid is divided into multiple resource elements.
  • a resource block includes 12 consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, 7 consecutive OFDM symbols in the time domain, or 84 resource elements.
  • a resource block For an extended cyclic prefix, a resource block includes 6 consecutive OFDM symbols in the time domain and has 72 resource elements. Some of the resource elements, as indicated as R 310 and R 320, include DL reference signals (DL-RS) .
  • the DL-RS include Cell-specific RS (CRS) (also sometimes called common RS) 310 and UE-specific RS (UE-RS) 320.
  • UE-RS 320 are transmitted only on the resource blocks upon which the corresponding physical DL shared channel (PDSCH) is mapped.
  • the number of bits carried by each resource element depends on the modulation scheme. Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate for the UE.
  • an eNB may send a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) for each cell in the eNB.
  • the primary and secondary synchronization signals may be sent in symbol periods 6 and 5, respectively, in each of subframes 0 and 5 of each radio frame with the normal cyclic prefix (CP) .
  • the synchronization signals may be used by UEs for cell detection and acquisition.
  • the eNB may send a Physical Broadcast Channel (PBCH) in symbol periods 0 to 3 in slot 1 of subframe 0.
  • PBCH Physical Broadcast Channel
  • the eNB may send a Physical Control Format Indicator Channel (PCFICH) in the first symbol period of each subframe.
  • the PCFICH may convey the number of symbol periods (M) used for control channels, where M may be equal to 1, 2 or 3 and may change from subframe to subframe. M may also be equal to 4 for a small system bandwidth, e.g., with less than 10 resource blocks.
  • the eNB may send a Physical HARQ Indicator Channel (PHICH) and a Physical Downlink Control Channel (PDCCH) in the first M symbol periods of each subframe.
  • the PHICH may carry information to support hybrid automatic repeat request (HARQ) .
  • the PDCCH may carry information on resource allocation for UEs and control information for downlink channels.
  • the eNB may send a Physical Downlink Shared Channel (PDSCH) in the remaining symbol periods of each subframe.
  • the PDSCH may carry data for UEs scheduled for data transmission on the downlink.
  • the eNB may send the PSS, SSS, and PBCH in the center 1.08 MHz of the system bandwidth used by the eNB.
  • the eNB may send the PCFICH and PHICH across the entire system bandwidth in each symbol period in which these channels are sent.
  • the eNB may send the PDCCH to groups of UEs in certain portions of the system bandwidth.
  • the eNB may send the PDSCH to specific UEs in specific portions of the system bandwidth.
  • the eNB may send the PSS, SSS, PBCH, PCFICH, and PHICH in a broadcast manner to all UEs, may send the PDCCH in a unicast manner to specific UEs, and may also send the PDSCH in a unicast manner to specific UEs.
  • Each resource element may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value.
  • Resource elements not used for a reference signal in each symbol period may be arranged into resource element groups (REGs) .
  • Each REG may include four resource elements in one symbol period.
  • the PCFICH may occupy four REGs, which may be spaced approximately equally across frequency, in symbol period 0.
  • the PHICH may occupy three REGs, which may be spread across frequency, in one or more configurable symbol periods. For example, the three REGs for the PHICH may all belong in symbol period 0 or may be spread in symbol periods 0, 1, and 2.
  • the PDCCH may occupy 9, 18, 36, or 72 REGs, which may be selected from the available REGs, in the first M symbol periods, for example. Only certain combinations of REGs may be allowed for the PDCCH.
  • a UE may know the specific REGs used for the PHICH and the PCFICH.
  • the UE may search different combinations of REGs for the PDCCH.
  • the number of combinations to search is typically less than the number of allowed combinations for the PDCCH.
  • An eNB may send the PDCCH to the UE in any of the combinations that the UE will search.
  • Fig. 3 is provided as an example. Other examples are possible and may differ from what was described above in connection with Fig. 3.
  • Fig. 4 is a diagram illustrating an example 400 of an uplink (UL) frame structure in LTE, in accordance with various aspects of the present disclosure.
  • the available resource blocks for the UL may be partitioned into a data section and a control section.
  • the control section may be formed at the two edges of the system bandwidth and may have a configurable size.
  • the resource blocks in the control section may be assigned to UEs for transmission of control information.
  • the data section may include all resource blocks not included in the control section.
  • the UL frame structure results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all of the contiguous subcarriers in the data section.
  • a UE may be assigned resource blocks 410a, 410b in the control section to transmit control information to an eNB.
  • the UE may also be assigned resource blocks 420a, 420b in the data section to transmit data to the eNB.
  • the UE may transmit control information in a physical UL control channel (PUCCH) on the assigned resource blocks in the control section.
  • the UE may transmit only data or both data and control information in a physical UL shared channel (PUSCH) on the assigned resource blocks in the data section.
  • a UL transmission may span both slots of a subframe and may hop across frequencies.
  • a set of resource blocks may be used to perform initial system access and achieve UL synchronization in a physical random access channel (PRACH) 430.
  • the PRACH 430 carries a random sequence and cannot carry any UL data/signaling.
  • Each random access preamble occupies a bandwidth corresponding to six consecutive resource blocks.
  • the starting frequency is specified by the network. That is, the transmission of the random access preamble is restricted to certain time and frequency resources. There is no frequency hopping for the PRACH.
  • the PRACH attempt is carried in a single subframe (e.g., of 1 ms) or in a sequence of few contiguous subframes and a UE can make only a single PRACH attempt per frame (e.g., of 10 ms) .
  • Fig. 4 is provided as an example. Other examples are possible and may differ from what was described above in connection with Fig. 4.
  • Fig. 5 is a diagram illustrating an example 500 of a radio protocol architecture for a user plane and a control plane in LTE, in accordance with various aspects of the present disclosure.
  • the radio protocol architecture for the UE and the eNB is shown with three layers: Layer 1, Layer 2, and Layer 3.
  • Layer 1 (L1 layer) is the lowest layer and implements various physical layer signal processing functions.
  • the L1 layer will be referred to herein as the physical layer 510.
  • Layer 2 (L2 layer) 520 is above the physical layer 510 and is responsible for the link between the UE and eNB over the physical layer 510.
  • the L2 layer 520 includes, for example, a media access control (MAC) sublayer 530, a radio link control (RLC) sublayer 540, and a packet data convergence protocol (PDCP) sublayer 550, which are terminated at the eNB on the network side.
  • MAC media access control
  • RLC radio link control
  • PDCP packet data convergence protocol
  • the UE may have several upper layers above the L2 layer 520 including a network layer (e.g., IP layer) that is terminated at a packet data network (PDN) gateway on the network side, and an application layer that is terminated at the other end of the connection (e.g., a far end UE, a server, and/or the like) .
  • IP layer e.g., IP layer
  • PDN packet data network gateway
  • the PDCP sublayer 550 provides retransmission of lost data in handover.
  • the PDCP sublayer 550 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between eNBs.
  • the RLC sublayer 540 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ) .
  • HARQ hybrid automatic repeat request
  • the MAC sublayer 530 provides multiplexing between logical and transport channels.
  • the MAC sublayer 530 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs.
  • the MAC sublayer 530 is also responsible for HARQ operations.
  • the radio protocol architecture for the UE and eNB is substantially the same for the physical layer 510 and the L2 layer 520 with the exception that there is no header compression function for the control plane.
  • the control plane also includes a radio resource control (RRC) sublayer 560 in Layer 3 (L3 layer) .
  • the RRC sublayer 560 is responsible for obtaining radio resources (i.e., radio bearers) and for configuring the lower layers using RRC signaling between the eNB and the UE.
  • Fig. 5 is provided as an example. Other examples are possible and may differ from what was described above in connection with Fig. 5.
  • Fig. 6 is a diagram illustrating example components 600 of a base station such as an eNB 110, 210, 230 and a UE 145, 250 in an access network, in accordance with various aspects of the present disclosure.
  • eNB 110, 210, 230 may include a controller/processor 605, a TX processor 610, a channel estimator 615, an antenna 620, a transmitter 625TX, a receiver 625RX, an RX processor 630, and a memory 635.
  • Fig. 6 is a diagram illustrating example components 600 of a base station such as an eNB 110, 210, 230 and a UE 145, 250 in an access network, in accordance with various aspects of the present disclosure.
  • eNB 110, 210, 230 may include a controller/processor 605, a TX processor 610, a channel estimator 615, an antenna 620, a transmitter 625TX, a receiver 625RX, an RX processor 630, and
  • UE 145, 250 may include a receiver RX, for example, of a transceiver TX/RX 640, a transmitter TX, for example, of a transceiver TX/RX 640, an antenna 645, an RX processor 650, a channel estimator 655, a controller/processor 660, a memory 665, a data sink 670, a data source 675, and a TX processor 680.
  • a receiver RX for example, of a transceiver TX/RX 640
  • a transmitter TX for example, of a transceiver TX/RX 640
  • an antenna 645 for example, an RX processor 650, a channel estimator 655, a controller/processor 660, a memory 665, a data sink 670, a data source 675, and a TX processor 680.
  • controller/processor 605 implements the functionality of the L2 layer.
  • the controller/processor 605 provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE 145, 250 based, at least in part, on various priority metrics.
  • the controller/processor 605 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE 145, 250.
  • the TX processor 610 implements various signal processing functions for the L1 layer (e.g., physical layer) .
  • the signal processing functions includes coding and interleaving to facilitate forward error correction (FEC) at the UE 145, 250 and mapping to signal constellations based, at least in part, on various modulation schemes (e.g., binary phase-shift keying (BPSK) , quadrature phase-shift keying (QPSK) , M-phase-shift keying (M-PSK) , M-quadrature amplitude modulation (M-QAM) ) .
  • FEC forward error correction
  • BPSK binary phase-shift keying
  • QPSK quadrature phase-shift keying
  • M-PSK M-phase-shift keying
  • M-QAM M-quadrature amplitude modulation
  • Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream.
  • the OFDM stream is spatially precoded to produce multiple spatial streams.
  • Channel estimates from a channel estimator 615 may be used to determine the coding and modulation scheme, as well as for spatial processing.
  • the channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 145, 250.
  • Each spatial stream is then provided to a different antenna 620 via a separate transmitter TX, for example, of transceiver TX/RX 625. Each such transmitter TX modulates an RF carrier with a respective spatial stream for transmission.
  • each receiver RX for example, of a transceiver TX/RX 640 receives a signal through its respective antenna 645.
  • Each such receiver RX recovers information modulated onto an RF carrier and provides the information to the receiver (RX) processor 650.
  • the RX processor 650 implements various signal processing functions of the L1 layer.
  • the RX processor 650 performs spatial processing on the information to recover any spatial streams destined for the UE 145, 250. If multiple spatial streams are destined for the UE 145, 250, the spatial streams may be combined by the RX processor 650 into a single OFDM symbol stream.
  • the RX processor 650 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT) .
  • the frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal.
  • the symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB 110, 210, 230. These soft decisions may be based, at least in part, on channel estimates computed by the channel estimator 655.
  • the soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB 110, 210, 230 on the physical channel.
  • the data and control signals are then provided to the controller/processor 660.
  • the controller/processor 660 implements the L2 layer.
  • the controller/processor 660 can be associated with a memory 665 that stores program codes and data.
  • the memory 665 may include a non-transitory computer-readable medium.
  • the controller/processor 660 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network.
  • the upper layer packets are then provided to a data sink 670, which represents all the protocol layers above the L2 layer.
  • Various control signals may also be provided to the data sink 670 for L3 processing.
  • the controller/processor 660 is also responsible for error detection using an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support HARQ operations.
  • ACK acknowledgement
  • NACK negative acknowledgement
  • a data source 675 is used to provide upper layer packets to the controller/processor 660.
  • the data source 675 represents all protocol layers above the L2 layer.
  • the controller/processor 660 implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based, at least in part, on radio resource allocations by the eNB 110, 210, 230.
  • the controller/processor 660 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB 110, 210, 230.
  • Channel estimates derived by a channel estimator 655 from a reference signal or feedback transmitted by the eNB 110, 210, 230 may be used by the TX processor 680 to select the appropriate coding and modulation schemes, and to facilitate spatial processing.
  • the spatial streams generated by the TX processor 680 are provided to different antenna 645 via separate transmitters TX, for example, of transceivers TX/RX 640. Each transmitter TX, for example, of transceiver TX/RX 640 modulates an RF carrier with a respective spatial stream for transmission.
  • the UL transmission is processed at the eNB 110, 210, 230 in a manner similar to that described in connection with the receiver function at the UE 145, 250.
  • Each receiver RX for example, of transceiver TX/RX 625 receives a signal through its respective antenna 620.
  • Each receiver RX for example, of transceiver TX/RX 625 recovers information modulated onto an RF carrier and provides the information to a RX processor 630.
  • the RX processor 630 may implement the L1 layer.
  • the controller/processor 605 implements the L2 layer.
  • the controller/processor 605 can be associated with a memory 635 that stores program code and data.
  • the memory 635 may be referred to as a computer-readable medium.
  • the controller/processor 605 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE 145, 250.
  • Upper layer packets from the controller/processor 605 may be provided to the core network.
  • the controller/processor 605 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.
  • one or more components of UE 145, 250 may be included in a housing 145’ , as shown in Fig 1.
  • One or more components of UE 145, 250 may be configured to perform identification of a candidate cell for radio connection reestablishment, as described in more detail elsewhere herein.
  • the controller/processor 660 and/or other processors and modules of UE 145, 250 may perform or direct operations of, for example, process 800 of Fig. 8 and/or other processes as described herein.
  • one or more of the components shown in Fig. 6 may be employed to perform example process 800 and/or other processes for the techniques described herein.
  • Fig. 6 The number and arrangement of components shown in Fig. 6 are provided as an example. In practice, there may be additional components, fewer components, different components, or differently arranged components than those shown in Fig. 6. Furthermore, two or more components shown in Fig. 6 may be implemented within a single component, or a single component shown in Fig. 6 may be implemented as multiple, distributed components. Additionally, or alternatively, a set of components (e.g., one or more components) shown in Fig. 6 may perform one or more functions described as being performed by another set of components shown in Fig. 6.
  • a UE 145, 250 may communicate with a base station, such as an eNB 110, 210, 230, via a radio connection with a cell provided by the eNB 110, 210, 230.
  • the radio connection may include a radio resource control (RRC) connection.
  • RRC radio resource control
  • the UE 145, 250 may perform an RRC establishment procedure, and may exchange security information with the eNB 110, 210, 230.
  • the eNB 110, 210, 230 may store context information, such as a UE context associated with the UE 145, 250.
  • the connection procedure can be expedited using the context information.
  • an eNB 110, 210, 230 provides multiple cells.
  • the context information may be used to establish a connection with any cell provided by the eNB 110, 210, 230, irrespective of whether the cell is the one via which the UE 145, 250 originally established the radio connection.
  • the UE 145, 250 may need to reestablish the radio connection.
  • the reestablishment can be with the same cell as the original radio resource connection, or with a different cell.
  • the reestablishment may succeed only if a target cell for the reestablishment has a valid UE context. In other words, the reestablishment may only succeed when the target cell is provided by an eNB 110, 210, 230 that stores valid context information.
  • the UE 145, 250 may not select a target cell based at least in part on whether the target cell has access to a valid UE context. This may lead to failure of the reestablishment procedure and switching of the UE 145, 250 to an idle mode, which may result in dropped calls and/or diminished network performance.
  • Techniques and apparatuses described herein provide the selection of a target cell for cell reestablishment based at least in part on whether a base station, such as an eNB, associated with (e.g., a base station providing) the target cell has access to context information for the UE 145, 250.
  • a base station such as an eNB
  • the UE 145, 250 may generate a list of eNBs that have stored context information for the UE 145, 250, and may select a target cell based at least in part on whether the target cell is provided by an eNB identified by the list.
  • the UE 145, 250 may generate a list of target cells for radio connection reestablishment based at least in part on the list of eNBs, and may pass the list to a lower protocol layer for selection of the target cell. In this way, the UE 145, 250 improves the likelihood of success of the radio connection reestablishment procedure and thereby improves network performance. Furthermore, when the UE 145, 250 generates the list of eNBs that store valid context information, burden on the eNB 110, 210, 230 is reduced, and messaging is reduced that would otherwise be needed to convey information identifying eNBs with valid context information from an eNB 110, 210, 230 to the UE 145, 250.
  • Figs. 7A and 7B are diagrams illustrating an example 700 of identifying a candidate cell for radio connection reestablishment, in accordance with various aspects of the present disclosure.
  • an eNB 110, 210, 230 may be associated with an eNB identifier (shown as an eNB ID of 16859) .
  • the eNB 110, 210, 230 may provide one or more cells, and the one or more cells may be associated with respective cell identifiers or cell identities.
  • the eNB 110, 210, 230 provides cells associated with respective cell identifiers of 26, 68, and 59.
  • the eNB identifier, the cell identifiers, and/or the cell identities may be defined in a particular specification, such as 3GPP Technical Specification (TS) 36.423.
  • a particular cell may be identified by the E-UTRAN Cell Global Identifier (E-CGI) , which is defined by Table 9.2.14 of TS 36.423.
  • E-CGI E-UTRAN Cell Global Identifier
  • the E-CGI may include a bit string (e.g., 28 bits) , and may be provided in system information (e.g., system information block 1 (SIB-1) ) .
  • SIB-1 system information block 1
  • a first portion of the bit string (e.g., a first 20 bits, a left-most 20 bits, and/or the like) may be the eNB identifier, and a second portion of the bit string (e.g., a remaining 8 bits and/or the like) may include the cell identifier and/or cell identity.
  • a second portion of the bit string (e.g., a remaining 8 bits and/or the like) may include the cell identifier and/or cell identity.
  • the eNB identifier and the cell identifiers or cell identities are shown in a non-binary representation (e.g., hexadecimal) , so that the bit lengths match the prescribed bit lengths of TS 36.423.
  • the eNB identifier, cell identifier, and/or cell identity may be in a different format, may have a different bit length, and/or the like.
  • a UE 145, 250 may perform an RRC connection establishment procedure with the eNB 110, 210, 230. As further shown, the UE 145, 250 may perform the RRC connection establishment procedure with a particular cell identified by a cell identifier of 26. For example, and as shown by the E-CGI of 1685926, the UE 145, 250 may perform the RRC connection establishment procedure with the cell based at least in part on the eNB identifier of 16859 and the cell identifier of 26.
  • the eNB 110, 210, 230 may store radio connection context information based at least in part on the RRC connection establishment procedure.
  • the radio connection context information may include information for reestablishing the RRC connection.
  • the radio connection context information may include information identifying the UE 145, 250, information identifying a user of the UE 145, 250, mobility information for the UE 145, 250, security information for the UE 145, 250, and/or the like.
  • the eNB 110, 210, 230 can use the radio connection context information to reestablish the RRC connection with any cell provided by the eNB 110, 210, 230 (e.g., any of the cells associated with cell identifiers 26, 68, and 59) .
  • the UE 145, 250 may add the eNB identifier to stored information identifying eNBs that are associated with radio connection context information.
  • the stored information may include information identifying eNB identifiers of one or more eNBs 110, 210, 230 that have stored radio connection context information for the UE 145, 250.
  • the UE 145, 250 may subsequently connect to a cell provided by an eNB 110, 210, 230 that stores the radio connection context information by identifying the eNB 110, 210, 230 using the stored information.
  • the UE 145, 250 may perform radio connection reestablishment.
  • the UE 145, 250 may perform radio connection reestablishment based at least in part on a lost radio connection, a mobility state of the UE 145, 250, a channel characteristic of the radio connection, and/or the like.
  • the radio connection reestablishment may include an RRC connection reestablishment procedure or a similar procedure.
  • the UE 145, 250 may identify a target cell, and may attempt to reestablish a radio connection with the target cell.
  • the radio connection reestablishment may be successful when the target cell has access to (e.g., because a base station, such as an eNB, associated with the target cell provides access to) radio connection context information for the UE 145, 250 (e.g., when an eNB 110, 210, 230 that provides the target cell has previously stored the radio connection context information) .
  • the UE 145, 250 may move to a radio connection idle mode (e.g., RRC idle mode) .
  • a radio connection idle mode e.g., RRC idle mode
  • the UE 145, 250 may identify a target cell using the stored information identifying eNBs that have stored radio connection context information for the UE 145, 250. For example, the UE 145, 250 may identify the target cell based at least in part on the target cell storing or having access to a valid UE context, according to the stored information. In some aspects, the UE 145, 250 may identify multiple different target cells (e.g., multiple candidate cells for cell reestablishment) that are associated with one or more eNBs 110, 210, 230 identified by the stored information.
  • multiple target cells e.g., multiple candidate cells for cell reestablishment
  • the UE 145, 250 may determine whether each cell that covers the UE is associated with an eNB 110, 210, 230 that has stored radio connection context information, and may identify those cells associated with eNBs 110, 210, 230 that have stored radio connection context information as target cells. In this way, the UE 145, 250 may determine a list of multiple, different target cells.
  • the UE 145, 250 may provide information identifying the target cell (or information identifying a list of target cells or candidate cells) to a lower protocol layer of the UE 145, 250, and the lower layer may perform the radio connection reestablishment process.
  • the lower layer may perform the radio connection reestablishment process.
  • the UE 145, 250 may perform the radio connection reestablishment with regard to a cell identified by an E-CGI of 1685968.
  • the E-CGI of 1685968 may include an eNB identifier corresponding to the eNB 110, 210, 230 that stored the radio connection context information, as described in connection with Fig. 7A, above.
  • the E-CGI may include a cell identifier corresponding to a cell provided by the eNB 110, 210, 230. In this way, the UE 145, 250 identifies a cell that has access to the radio connection context information for radio connection reestablishment.
  • the eNB 110, 210, 230 may reestablish the radio connection (e.g., the RRC connection) using the radio connection context information (e.g., without traversing through an RRC idle mode) .
  • the UE 145, 250 improves the likelihood of success of the radio connection reestablishment process by identifying one or more target cells that have access to radio connection context information for the UE 145, 250.
  • network performance may be improved.
  • Figs. 7A and 7B are provided as examples. Other examples are possible and may differ from what was described with respect to Figs. 7A and 7B.
  • Fig. 8 is a diagram illustrating an example process 800 performed, for example, by a wireless communication device, in accordance with various aspects of the present disclosure.
  • Example process 800 is an example where a user equipment (e.g., UE 145, 250) performs identification of a candidate cell for radio connection reestablishment.
  • a user equipment e.g., UE 145, 250
  • process 800 may include identifying a target cell for radio connection reestablishment using stored information identifying at least one base station that stores a radio connection context of a user equipment, wherein the target cell is provided by a particular base station of the at least one base station, and wherein the stored information is determined by the user equipment (block 810) .
  • the user equipment may identify a target cell for radio connection reestablishment.
  • the user equipment may identify the target cell using stored information identifying at least one base station (e.g., eNB 110, 210, 230) that stores a radio connection context of the user equipment.
  • the target cell may be provided by a particular base station of the at least one base station that has stored the radio connection context.
  • the stored information may be determined by the user equipment (e.g., based at least in part on previous radio connections via cells provided by the at least one base station) .
  • process 800 may include performing radio connection reestablishment with regard to the target cell (block 820) .
  • the user equipment may perform radio connection reestablishment with regard to the target cell.
  • the user equipment improves the likelihood of success of the radio connection reestablishment.
  • the at least one base station stores the radio connection context based at least in part on a previous radio connection of the at least one base station with the user equipment.
  • the previous radio connection is to a different cell than the target cell, wherein the different cell is provided by the particular base station.
  • the stored information is determined based at least in part on respective cell identities of cells provided by the at least one base station.
  • the target cell is identified based at least in part on system information identifying the target cell, wherein the system information indicates that the target cell is provided by the particular base station.
  • the system information includes a first portion and a second portion, wherein the first portion identifies the particular base station, and wherein the second portion identifies the target cell.
  • the stored information identifies the first portion of the system information for the at least one base station.
  • the user equipment may generate a list of target cells including the target cell, wherein the list identifies cells provided by the at least one base station based at least in part on the stored information, and wherein the radio connection reestablishment is performed based at least in part on the list.
  • process 800 may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in Fig. 8. Additionally, or alternatively, two or more of the blocks of process 800 may be performed in parallel.
  • the term component is intended to be broadly construed as hardware, firmware, or a combination of hardware and software.
  • a processor is implemented in hardware, firmware, or a combination of hardware and software.
  • satisfying a threshold may refer to a value being greater than the threshold, greater than or equal to the threshold, less than the threshold, less than or equal to the threshold, equal to the threshold, not equal to the threshold, and/or the like.
  • “at least one of: a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c) .

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

D'une manière générale, la présente invention se rapporte au domaine des communications sans fil. Selon certains aspects, un équipement d'utilisateur peut : identifier une cellule cible en vue du rétablissement d'une connexion radio à l'aide d'informations stockées qui identifient au moins une station de base stockant un contexte de connexion radio de l'équipement d'utilisateur, la cellule cible étant fournie par une station de base particulière de la ou des stations de base, et les informations stockées étant déterminées par l'équipement d'utilisateur; et exécuter un rétablissement de la connexion radio par rapport à la cellule cible. L'invention propose également de nombreux autres aspects.
PCT/CN2017/097795 2017-08-17 2017-08-17 Techniques et appareils permettant d'identifier une cellule candidate pour le rétablissement d'une connexion radio WO2019033327A1 (fr)

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