WO2021051218A1 - 一种侧链路重传方法 - Google Patents

一种侧链路重传方法 Download PDF

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Publication number
WO2021051218A1
WO2021051218A1 PCT/CN2019/105865 CN2019105865W WO2021051218A1 WO 2021051218 A1 WO2021051218 A1 WO 2021051218A1 CN 2019105865 W CN2019105865 W CN 2019105865W WO 2021051218 A1 WO2021051218 A1 WO 2021051218A1
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data packet
zone
resource
ues
psfch
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PCT/CN2019/105865
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English (en)
French (fr)
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张波
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张波
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Priority to PCT/CN2019/105865 priority Critical patent/WO2021051218A1/zh
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
    • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/30—Services specially adapted for particular environments, situations or purposes
    • H04W4/40—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/30—Services specially adapted for particular environments, situations or purposes
    • H04W4/40—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]
    • H04W4/46—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P] for vehicle-to-vehicle communication [V2V]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/14—Direct-mode setup

Definitions

  • the present invention relates to a communication method, in particular to a side link retransmission method in vehicle networking (V2X) communication that can effectively realize cooperative relay.
  • V2X vehicle networking
  • Vehicle-to-Everything Communication (V2X, Vehicle-to-Everything Communication) is the key technology of the future intelligent transportation system. It provides vehicle information through sensors, vehicle-to-vehicle terminals and electronic tags mounted on the vehicle, and uses various communication technologies to achieve vehicle-to-vehicle communication (V2V) and vehicle-to-vehicle communication (V2P, Vehicle-to- Pedestrian Communication) and Vehicle-to-Network Communication (V2N, Vehicle-to-Network Communication) can obtain a series of traffic information such as real-time road conditions, road information, and pedestrian information, thereby improving driving safety, reducing congestion, and improving traffic efficiency.
  • V2V vehicle-to-Everything Communication
  • V2V Vehicle-to-Everything Communication
  • V2V Vehicle-to-Everything Communication
  • V2P Vehicle-to-vehicle communication
  • V2N Vehicle-to-Network Communication
  • NR New Radio V2X
  • 3GPP 3rd Generation Partnership Project
  • NR V2X New Radio V2X
  • the NR V2X system will have a flexible design and support low-latency and high-reliability services.
  • the NR V2X system will also have higher system capacity and better coverage.
  • NR-V2X in order to achieve extremely high requirements such as Packet Reception Ratio (PRR), NR-V2X supports retransmission based on Hybrid Automatic Repeat reQuest (HARQ).
  • HARQ relies on the Physical Sidelink Feedback Channel (PSFCH), and the HARQ feedback process can be based on Option-1 (Option-1) or Option-2 (Option-2) mechanisms.
  • Option-1 (Option-1) If the Rx UE fails to decode the corresponding TB (Transport Block) after decoding the associated PSCCH, the Rx UE sends HARQ-NAK on the PSFCH. Otherwise, it does not send any signal on the PSFCH.
  • Option-2 If the Rx UE successfully decodes the corresponding TB, it sends HARQ-ACK on the PSFCH. If the Rx UE fails to decode the corresponding TB after decoding the associated PSCCH, the Rx UE sends HARQ-NAK on the PSFCH.
  • D2D Device-to-Device
  • the D2D link of the relay relies on the side link communication mechanism
  • the relay device-to-network communication relies on the normal LTE cellular mechanism.
  • the only impact of the Layer-3 relay function on the wireless standard specification is in the RRC function.
  • Layer-1 and Layer-2 relay functions are necessary.
  • the direct communication link between the device and the device is called the side link (or bypass) (Sidelink), which is similar to the uplink and downlink.
  • Sidelink or bypass
  • the former is called Physical Sidelink Control Channel (PSCCH), and the latter is called Physical Sidelink Shared Channel (PSSCH).
  • PSCCH is used to indicate the time-frequency domain resource location for PSSCH transmission, the modulation and coding scheme, and the priority of the data carried in the PSSCH, and the PSSCH is used to carry data.
  • Resource allocation can simply rely on a centralized mechanism; if it is in the coverage area, it is done through the gNB, or if it is outside the coverage area, it is done through the relay node.
  • this centralized mechanism implements resource selection through Mode-3; this method improves reliability by ensuring that there is no resource conflict between Tx UEs (Transmitter UEs). But it leads to a relatively large delay.
  • a new mechanism is applied to the selection of the V2X side link (Sidelink) resource pool, and the mechanism is related to the zone identification (for example, zone ID, Zone-ID).
  • zone identification for example, zone ID, Zone-ID
  • independent resources or resource pools are associated with geographic coordinates, and are (pre-)configured by the upper layer (pre) of V2X side link (Sidelink) communication.
  • the Tx UE Transmitter UE
  • the Tx UE uses its last geographic coordinates to implement the resource pool selection. Through the following formula, Tx UE determines the Zone-ID:
  • Zone-ID y 1 N x +x 1 ,
  • L is the length of the zone
  • W is the width of the zone
  • N x is the longitude of Zone-ID
  • N y is the latitude of Zone-ID
  • the information of L, W, N x and N y can be configured through the upper RRC or realized through a pre-configuration method.
  • (pre)configuration means configuration or preconfiguration.
  • the parameters L, W, N x , N y are configured by RRC (Radio Resource Control, Radio Resource Control) in Type-21 or Type-26 system information block (System Information Block, SIB) , Or pre-configured in the SL-V2X-Preconfiguration system. Therefore, N b bits are required to indicate the N x ⁇ N y Zone-IDs that constitute a zone block (ZB, Zone Block), where:
  • LTE-V2X communication data packets are relatively simple, only considering the arrival and transmission of periodic data packets, and the size of the data packets is also constant.
  • NR-V2X there are three types of communication transmission (Cast): broadcast (Broadcast), unicast (Unicast) and multicast (Groupcast).
  • the arrival of data packets can be either periodic or aperiodic.
  • the packet size can be constant or not.
  • Tx UE sends and exchanges location information through Zone-ID or geographic coordinates.
  • the Tx UE sends SCI (Sidelink Control Indication) through the PSCCH channel, and the receiving user (Rx UE, Receive UE) in the relevant group detects the SCI to obtain the Zone-ID or geographic coordinates of the Tx UE, and obtains the distance to the Tx UE.
  • SCI Systemlink Control Indication
  • Rx UE, Receive UE the receiving user
  • the hybrid automatic repeat request Hybrid Automatic Repeat reQuest, HARQ
  • Tx UE when a user (UE) is sending a data packet, the UE is defined as Tx UE, and when receiving a data packet, it is defined as Rx UE. Therefore, the same user is a Tx UE in a certain time slot (Time slot), and is a Rx UE in a certain time slot.
  • Time slot time slot
  • the relay function can be implemented by a relay node or a base station, or a Road Side Unit (RSU) placed on the ground, or a mobile cluster cluster head (Mobile Cluster Header), or more generally a vehicle UE. Since the relay node has high antenna gain and large transmission power, its coverage can be much larger. However, outside the coverage area, only the mobile cluster cluster head or the vehicle UE can be responsible for implementing the relay function. In order to enhance the relay coverage, the simple method is to repeat the transmission multiple times, but this method will increase the channel resource cost.
  • RSU Road Side Unit
  • Mobile Cluster Header Mobile Cluster Header
  • the Tx UE sends data packets to other Rx UEs, and some Rx UEs successfully detect the data packets, while some Rx UEs fail to detect the data packets.
  • Rx UE reception failure one is that the Rx UE receives a weak signal or experiences strong interference and the detection fails, and the other is that the Rx UE only installs a half-duplex system.
  • the half-duplex system means that once the UE is in the transmission mode, it cannot receive, and vice versa. Thereby reducing the receiving rate of data packets.
  • the purpose of the present invention is to provide a side link retransmission method to solve the problems raised in the above technical background.
  • the resource in this application may be the physical side link control channel PSSCH, the physical side link shared channel PSCCH, or the physical layer side link feedback channel PSFCH (Physical Sidelink Feedback Channel).
  • PSSCH Physical side link control channel
  • PSCCH physical side link shared channel
  • PSFCH Physical Layer side link feedback channel
  • the side link retransmission method provided by the present invention is preferably applied to multiple user equipment UEs that implement the relay function in the Internet of Vehicles architecture, that is, the Multi-UE Cooperative Relay (Multi-UE Cooperative Relay) retransmission method.
  • Multi-UE Cooperative Relay Multi-UE Cooperative Relay
  • Tx UE sends data packets to other Rx UEs in the group; some Rx UEs successfully detect the data packet, while some Rx UEs fail to detect the data packet; multi-UE cooperative relay is mainly The Rx UE that successfully detects the data packet is used as an R-UE (Relay UE) to complete the retransmission, that is, these R-UEs copy and send the same data packet to the Rx UE that fails to detect the data packet.
  • R-UE Relay UE
  • the side link retransmission method provided by the present invention includes:
  • each Tx UE sends the first data packet to the receiving device Rx UE; when some Rx UEs fail to receive the first data packet on the link, other Rx UEs successfully detect The first data packet, and re-encode the first data packet to generate the second data packet (generally the first data packet and the second data packet are exactly the same, unless the first data packet signaling is specifically implicit or Explicitly indicate), and then forward/retransmit the second data packet to the first data packet in the same resource (or different resource) initially used by the Tx UE at the same time.
  • the detection fails, and/or it works in a half-duplex state. Other UEs.
  • the sending device Tx UE and the receiving device Rx UE establish multicast communication
  • the method for multi-UE cooperative relay retransmission includes:
  • At least one sending device Tx UE sends the first data packet in the first time slot, at least one receiving device Rx UE successfully detects the first data packet sent by the data channel (for example, PSCCH and PSSCH), at least one receiving device Rx UE Fail to detect the first data packet;
  • the data channel for example, PSCCH and PSSCH
  • the receiving device Rx UE that failed to detect the first data packet sends sidelink feedback control information SFCI (Sidelink Feedback Control Information) on the physical layer side-chain feedback channel PSFCH (for example, depending on Option-1 (Option- 1) or Option-2 (Option-2 HARQ feedback mechanism), other UEs in the multicast communication receive it; wherein, the side-chain feedback control information is used to indicate whether the first data packet is detected ;
  • SFCI Segment Feedback Control Information
  • PSFCH Physical layer side-chain feedback channel
  • the packet is forwarded to other UEs in the second time slot; the sending device Tx UE that initially sent the first data packet (if more than two Tx UEs are sending the first data packet at the same time) detects the second data packet, it is resolved Half-duplex problem.
  • the receiving device Rx that failed to detect the first data packet receives the second data packet, and performs HARQ softening between the second data packet and the previously soft-stored first data packet. Combine, and then decode it, so as to realize the retransmission process by multi-UE cooperative relay;
  • the second time slot is a time slot after the first time slot.
  • the transmitting device Tx UE transmits the SCI through the physical side link control channel PSCCH, and the Tx UE uses an explicit mechanism (Explicit) or an implicit mechanism (Implicit) to notify the PSFCH resource index used for HARQ feedback and the resource index used for reconfiguration.
  • the coupling of resources can be performed in the time domain or the frequency domain; if the coupling is performed in the time domain, the resources in the frequency domain must be indicated by the SCI; if the coupling is performed in the frequency domain, the resources in the time domain must Instructed by SCI; resource coupling can also be done simultaneously in time domain and frequency domain.
  • the receiving device Rx UE that fails to detect the first data packet feeds back HARQ NAK and is received by other UEs in the multicast communication, this means that the PSCCH+PSSCH resource indicated by the SCI will be Multi-UE cooperative relay use; if it fails to detect that the receiving device Rx of the first data packet UE does not feedback HARQ NAK, the resource index of PSCCH+PSSCH indicated by SCI in the first data packet can be used by other Tx UEs Use, that is, the resources reserved by the SCI will be automatically released.
  • the receiving device Rx UE that successfully detects the first data packet receives HARQ NAK and/or knows that Tx UE half-duplex occurs, it acts as an R-UE to perform cooperative relay-based retransmission.
  • the UE when the user equipment UE is sending data packets, the UE is defined as Tx UE, and when receiving data packets, it is defined as Rx UE. Therefore, the same user equipment UE is a Tx UE in a certain time slot (Time slot), and is a Rx UE in a certain time slot.
  • the reasons for the failure of the transmission of the first data packet include: the Rx UE receives a weak signal or experiences strong interference, resulting in detection failure; or, the Rx UE only installs a half-duplex system.
  • the multi-UE cooperative relay is implemented by Layer-1 relay (Layer-1 Relay) or Layer-2 relay (Layer-2 Relay);
  • the Layer-1 relay only involves the physical layer in the relay process; wherein, only when the first data packet is successfully decoded, multiple (at least two) Rx UEs (R-UEs) are the same as Tx UEs.
  • the received first data packet is re-encoded.
  • the R-UE forwards the re-encoded second data packet on the same resource as the Tx UE initially used; In other words, R-UE must use the same physical side link control channel PSCCH and its related physical side link shared channel PSSCH. In this case, R-UE will not involve MAC scheduling and HARQ processes. But it is possible to implement Soft-Combining (for example, Chase Combining) on PSCCH and PSSCH;
  • the Layer-2 relay involves the physical layer and the MAC layer in the relay process; in the physical layer, only when the first data packet is successfully decoded, the R-UE and Tx UE re-encode the received data packet ; In the MAC layer, the R-UE receives at least one HARQ Negative-acknowledgement (NAK), and the R-UE forwards the recoded second data packet on the same resource as the Tx UE initially used; in this case , R-UE only involves simple scheduling (no rescheduling of resources). Generally, there is no need to consider channel conditions, data buffering status, and priority control. The scheduler only needs to simply judge whether cooperative retransmission should be performed.
  • NAK HARQ Negative-acknowledgement
  • the multi-UE cooperative relay is mainly implemented through Layer-2 relay.
  • the UE includes a primary R-UE (Primary R-UE) and/or a secondary R-UE (Secondary R-UE), where:
  • the primary R-UE is designated by a network or group member.
  • the primary R-UE can be a single R-UE or multiple R-UEs, and it must participate in multi-UE cooperative relay unless it does not correctly receive the Tx UE transmission
  • the first data packet ;
  • the secondary R-UE voluntarily participates in multi-UE coordinated relay. In most cases, the secondary R-UE can receive data packets from neighboring Tx UEs, and then forward them to neighboring Rx UEs.
  • the UE adopts a secondary R-UE.
  • the resources include primary relay resources (Primary Relay Resources) and secondary relay resources (Secondary Relay Resources), where:
  • the primary relay resource is indicated by the SCI on the physical side link control channel PSCCH of the first data packet, and is coupled to the first data packet; in most cases, it is the resource for transmitting the first data packet with the Tx UE Same; all R-UEs use the same primary relay resource to complete multi-UE coordinated relay.
  • the secondary relay resource is indicated by the SCI on the physical side link control channel PSCCH of the second data packet; that is, the R-UE can independently select the resource for forwarding the second data packet, and different R-UEs Different resources can be used.
  • the resource adopts a primary relay resource.
  • the Rx UE that successfully detects more than two first data packets may perform XoR (eXclusive OR) encoding on more than two first data packets, thereby improving side link transmission efficiency.
  • XoR eXclusive OR
  • the side link retransmission method provided by the present invention is preferably applied to multiple user equipment UEs that implement the relay function based on location area in the Internet of Vehicles architecture, that is, location area assisted relay Retransmission method.
  • location area assisted relay retransmission method in the case where the RCR (radio communication range) does not exceed the QCR (QoS communication range) is preferable.
  • N areas are divided, and N is a natural number; the area ID in the nth area is Zone-ID-n, and n is a natural number selected from 0 to N-1;
  • the Zone-ID-n area is occupied by I n UEs (I n is the number of UEs in the Zone-ID-n area);
  • the radio communication range between UEs RCR Radio Communication Range
  • QCR Quality of service communication Range
  • the transmitted data packet needs to reach which can be from the edge of an area to its next neighbor The distance to the edge of the area;
  • Zone-ID-(n-1), Zone-ID-n and Zone-ID-(n+1) are adjacently arranged in order
  • RCR includes Zone-ID-(n-1) and Zone-ID- The area of n, or the area including Zone-ID-n and Zone-ID-(n+1), QCR is across the zone-ID-(n-1), Zone-ID-n and Zone-ID-( The area of n+1), of course, can be farther; in this way, the size of each area can be determined according to the RCR range, so as to ensure that UEs in the same area can successfully communicate with each other; the distance of the area can be said to be the actual distance or RSRP Radio distance
  • the method includes:
  • the sending device Tx UE associated with Zone-ID-(n-1) and Zone-ID-(n+1) sends initial data packets, and with Zone-ID-(n-1), Zone-ID-n, Zone-ID-(n+1)
  • the associated receiving device Rx UE receives the initial data packet
  • All Rx UEs in the same area of Tx UE can successfully detect the initial data packet; the area associated with Zone-ID-n that is adjacent to Zone-ID-(n-1) and Zone-ID-(n+1) at the same time Some or all of the Rx UEs in can successfully detect the initial data packet; the Rx UE in the zone associated with the Zone-ID-(n+1) adjacent to the Zone-ID-(n-1) interval, or the zone associated with the Zone-ID-(n-1) -ID-(n+1) Interval adjacent Zone-ID-(n-1) Rx UE in the area associated, at least part of the UE failed to detect the initial data packet;
  • the Rx UE that successfully detects the initial data packet in Zone-ID-n performs XoR encoding on the initial data packet, and then places the re-encoded XoR encoded data packet in the same resource as the Tx UE initially used (a single resource or a limited number of resources). Resources) at the same time forwarding/retransmitting to other UEs that fail to detect initial data packets and/or work in a half-duplex state.
  • the initial data packet transmission can be performed by a Tx UE in the following Zone-ID (Type-1 zone) in the time slot t,
  • Zone-ID y 1 N x +x 1 , if (x 1 mod2) ⁇ (y 1 mod2);
  • the Tx UE-i n-1 associated with Zone-ID-(n-1) sends the first initial data packet
  • the first data packet will be successfully received by all Rx UEs in its own area.
  • the first initial data packet will also be successfully received by the Rx UE associated with Zone-ID-n.
  • the first initial data packet cannot be successfully received. Received by the Rx UE associated with Zone-ID-(n+1);
  • Tx UE-i n+1 associated with Zone-ID-(n+1) sends the second initial data packet
  • the second initial data packet will be successfully received by all Rx UEs in its own area.
  • the second initial data packet will also be successfully received by the Rx UE associated with Zone-ID-n.
  • the second initial data packet Unable to be received by the Rx UE associated with Zone-ID-(n-1);
  • R-UE-i n XoR encoded data packet Forward to Rx UEs in two neighboring areas associated with Zone-ID-(n-1) and Zone-ID-(n+1);
  • all Rx UEs associated with Zone-ID-(n-1) are aware of the first initial data packet in advance And by XoR decoding to detect All Rx UEs associated with Zone-ID-(n+1) are aware of the second initial data packet in advance And by XoR decoding to detect
  • the receiving device Rx UE associated with Zone-ID-(n-1) and Zone-ID-(n+1) is on the physical layer side-chain feedback channel PSFCH according to a preset strategy, to other UEs in the multicast Send sidelink feedback control information SFCI (Sidelink Feedback Control Information) including HARQ-NAK or HARQ-ACK, HARQ-NAK triggers Rx UEs that successfully detected the initial data packet in Zone-ID-n to retransmit one by one; among them, all
  • SFCI Segmentlink Feedback Control Information
  • HARQ-NAK triggers Rx UEs that successfully detected the initial data packet in Zone-ID-n to retransmit one by one; among them, all
  • the preset strategy includes any of the following methods:
  • Solution-1 If the decoding of the initial data packet fails, the receiving device Rx UE that failed to detect the initial data packet feeds back HARQ-NAK, and the PSFCH resource is only coupled with the initial data packet;
  • Scenario-2 If the initial data packet decoding fails, the receiving device Rx that failed to detect the initial data packet feeds back HARQ-NAK, and the PSFCH resource is coupled with the initial data packet and the receiving device Rx that feeds back HARQ-NAK to the zone-ID of the UE ;
  • Solution-3 The receiving device Rx UE feeds back HARQ-NAK or HARQ-ACK, and the PSFCH resource is coupled with the initial data packet and the receiving device Rx UE's Zone-ID that feeds back HARQ-NAK or HARQ-ACK.
  • the resource includes: a data packet resource (Data Packet Resource, DPR) used for initial data packet transmission and a cooperative relay resource (Cooperative Relay Resource, CRR) used for cooperative relay transmission.
  • DPR Data Packet Resource
  • CRR Cooperative Relay Resource
  • DPR and CRR are processed by Time Division Multiplexing (TDM) to avoid half-duplex problems;
  • TDM Time Division Multiplexing
  • Both DPR and CRR are associated with Zone-ID, use the same number of resources in the frequency domain, represented by L ZONE sub-channels (Sub-channel, SCH, each containing L ZONE Resource Blocks, RBs), and have them in the time domain
  • L ZONE sub-channels Sub-channel, SCH, each containing L ZONE Resource Blocks, RBs
  • L ZONE SCH and L DPR time slots form a DPR SCB block (SCH Block, SCB), and L ZONE SCH And L CRR time slot form the SCB block of CRR;
  • DPR the resource of the smallest transmission unit of SCH is denoted as DPR n,t (p)
  • CRR the resource of the smallest transmission unit is denoted as CRR n,t (p );
  • n Zone-ID
  • t is the time slot index in the time domain
  • p is the index of the SCH in the frequency domain
  • the parameters of L ZONE , L SCH , L DPR and L CRR are
  • the frequency domain and/or time slot resources used in the HARQ feedback process are reserved between DPR and CRR.
  • the resource is selected according to a preset rule, and the resource used for DPR and the resource used for CRR are coupled, so that all receiving devices Tx UE involved in the cooperative relay can implicitly select the same resource.
  • the preset rules include the following methods:
  • Rule-2 (XoR coded data packet sequence): Rx UE that successfully detects the initial data packet in each Zone-ID-n will sequentially number the XoR coded data packets according to the preset rules, and sequentially number the XoR coded data according to the order of numbers Packet to send;
  • Rule-3 In the configuration or pre-configuration of each SCB resource pool, the CRR resources are numbered sequentially according to preset rules. For example, the resource order is first predetermined from the direction of the slot index, and then from the SCH The index direction is determined, so that two-dimensional SCB resources can be formed;
  • Rule-4 The Rx UE that successfully detects the initial data packet in each Zone-ID-n selects the CRR resource configured or pre-configured in its own SCB, the sequence of the XoR encoded data packet, and the number of CRR resources Sequential one-to-one mapping.
  • the Tx UE sends the SCI and the associated PSSCH through the PSCCH, and the Rx UE receives the SCI and obtains QCR information; only in the QCR range, the Tx UE determines whether to feed back ACK or NAK according to the PSSCH decoding status.
  • the QCR information can be indicated by the SCI in an explicit or implicit way; among them,
  • the explicit way is that the SCI carries specific dedicated bits (for example, 3 bits) and directly indicates the QCR to the Rx UE;
  • the implicit method is that the SCI does not carry any additional bits, but reuses the existing initial packet priority information (for example, Priority Information, 3 bits) to indirectly indicate the QCR.
  • the existing initial packet priority information for example, Priority Information, 3 bits
  • the number of UEs involved in the cooperative relay can be based on the QCR information indicated by the SCI, and/or the initial data packet priority information, and/or the zone-ID relationship between the transmitter and receiver, and the candidate R-UE determines whether it should participate in the cooperation.
  • Relay that is, the number of R-UEs is not uniformly determined by the system, and can adaptively depend on the QoS and other requirements of each initial data packet.
  • the priority of the initial data packet or the size of the QCR is proportional to the number of R-UEs participating in the cooperative relay.
  • the XoR encoding includes: Type-1XoR-coding (Type-1XoR-coding) or Type-2XoR-coding (Type-2XoR-coding); wherein,
  • the MAC layer provides two or more transport blocks (TB) to the physical layer, which are sent by the Tx UE to the Rx UE through the wireless transmission link.
  • the scheduler in the MAC layer will notify the physical layer After channel coding, which TBs should be XoR encoded with each other; Tx UE sends the XoR encoded TB to Rx UE, and Rx UE performs XoR decoding on the received TB before channel decoding;
  • the MAC layer prepares and generates XoR-encoded TBs, and then is provided to the physical layer, that is, the physical layer does not need to know the information of the XoR encoding and does not need to change the physical layer structure.
  • the side link between UEs includes two types of link control information: one is the side link control information (Sidelink Control Information, SCI) transmitted through the Physical Sidelink Control Channel (PSCCH). ), the other is sidelink feedback control information (Sidelink Feedback Control Information, SFCI) transmitted through a physical sidelink feedback channel (Physical Sidelink Feedback Channel, PSFCH).
  • SCI Sidelink Control Information
  • SFCI Sidelink Feedback Control Information
  • the resource pool used for PSFCH may be:
  • any UE can use the common resource pool; or,
  • the resource pool can only be used by UEs located in the same area.
  • the public PSFCH resource pool is (pre-)configured, in which any UE can select PSFCH resources for HARQ feedback; as PSFCH resources, it can be coupled with PSCCH/PSSCH resources, and the coupled information It can be indicated by the SCI sent by the PSCCH, or mapped to each other by (pre)configuration.
  • the PSCCH must be used to transmit the relevant SCI and at the same time indicate the resources of the PSFCH; wherein there is a time interval between the PSCCH and its related PSFCH.
  • Tx UE transmits SCI information through PSCCH, and transmits related transport block (Transport Block, TB) through PSSCH, and SCI contains public PSFCH resource index information;
  • Rx UE receives SCI and its related data packets, and detects Whether there is an error; only when the Rx UE detects an error in the received data packet, the side link HARQ feedback is triggered; depending on HARQ option-1, all Rx UEs use the same PSFCH resource to feed back HARQ NAK .
  • the (pre-)configuration of the area-based PSFCH resource pool and the indication of the SCI for the PSFCH resource may be:
  • Each M resource in the PSFCH resource pool associated with Zone-ID-n can be indicated by index m;
  • ⁇ Indication bit in SCI The bit represents the selected index m.
  • the first PSFCH resource is allocated to the central area where the Tx UE is located
  • the second PSFCH resource is allocated to the first layer area centered on the Tx UE
  • the k-th PSFCH resource It is allocated to the (k-1)th layer area with Tx UE as the center until the last area layer in the QCR, and k is a natural number between 1 and the total number of layers.
  • the number of PSFCH resources in each regional layer should be individually (pre-)configured, and the rule is M 0 ⁇ M 1 ⁇ ... ⁇ M K-1 , where K is the number of regional layers in the QCR, which is also (pre) Configured.
  • each Rx UE detects the SCI on the PSCCH from one of the central Tx UEs, and then determines in which area the Rx UE is located based on the Zone-ID of the central Tx UE and the Zone-ID of the Rx UE. Floor. More preferably, according to the HARQ feedback mechanism, some Rx UEs (feedback Rx UEs) will each independently send corresponding SFCI (NAK) to the center Tx UE through the PSFCH associated with other regional layers. At the same time, SFCI It is also received by other UEs, and other UEs detect the SFCI from the feedback Rx UE, and cooperate to participate in the retransmission for the feedback Rx UE.
  • feedback Rx UEs will each independently send corresponding SFCI (NAK) to the center Tx UE through the PSFCH associated with other regional layers.
  • SFCI It is also received by other UEs, and other UEs detect the SFCI from the feedback Rx UE, and
  • the Rx UE obtains the area location of the Tx UE through the location coordinates, so the Rx UE can calculate the distance between the Tx UE and the Rx UE, thereby deriving which area layer the Rx UE belongs to. More preferably, Zone-ID does not need to be configured. Among them, the Tx UE needs to multicast its location coordinates, while the Rx UE only needs to know its own coordinates. For the PSFCH resource allocation used for HARQ feedback, the same (pre-)configuration method based on the regional layer can be maintained.
  • each Tx UE transmits location information on a data channel (eg, PSSCH channel) through RRC parameters, and each Rx UE updates the location information in the location table through the RRC parameters. Therefore, the location table (RRC parameters) should include the Tx UE location information and the related ID of the Tx UE; the UE can receive the Tx UE ID indicated by the SCI, and then look up the Tx UE ID in the RRC location table, and then obtain it implicitly The location of the corresponding Tx UE; therefore, the Tx UE only needs to send its UE ID through the SCI, and does not need the SCI to directly transmit location information.
  • a data channel eg, PSSCH channel
  • RRC parameters should include the Tx UE location information and the related ID of the Tx UE; the UE can receive the Tx UE ID indicated by the SCI, and then look up the Tx UE ID in the RRC location table, and then obtain it implicitly The location of the corresponding Tx UE; therefore, the T
  • the Tx UE can implicitly obtain the location area associated with the HARQ feedback UE, In this way, the AoD (Angle of Departure (AoD) of the relevant Tx UE is derived.
  • AoD Angle of Departure
  • the Tx UE located in Zone-ID-n performs initial data packet transmission through the PSCCH and its associated PSSCH, while the Rx UE located in other areas performs the corresponding reception; the Rx UE with the decoding error transmits the corresponding data through the activated PSFCH SFCI (NAK) for Tx UE; Tx UE obtains the zone-ID of the Rx UE with decoding error by detecting SFCI on PSFCH, and derives the AoD; Tx UE beamforming the data packet according to the derived AoD (Beamforming) Resend to the Rx UE that decoded the error.
  • the Rx UE with the decoding error transmits the corresponding data through the activated PSFCH SFCI (NAK) for Tx UE; Tx UE obtains the zone-ID of the Rx UE with decoding error by detecting SFCI on PSFCH, and derives the AoD; Tx UE beamforming the data packet according to the derived AoD (Be
  • the SCI sent by the Tx UE includes the PSFCH resource model index and PSFCH transmission timing information.
  • the Rx UE uses the PSFCH resource model to feed back the SFCI to the Tx UE, and the Tx UE detects its SFCI signal to identify and feed back the HARQ information of the UE and its Zone-ID.
  • the information contained in the SCI includes the transmission time difference between the PSCCH and the PSFCH, the PSFCH timing interval, and the PSFCH resource model index.
  • the Tx UE gradually increases its AoD resolution through different PSFCH resource models received at different transmission occasions.
  • beamforming is used for early retransmission in the subsequent transmission timing of the Tx UE, where the SCI sent on the PSCCH re-indicates the transmission time difference between the PSCCH and the PSFCH, the PSFCH timing interval, and the PSFCH resource model index; once with the Zone-ID-
  • the Rx UE associated with x detects SCI on the PSCCH, it knows that the information indicated by the previous SCI is covered by the current SCI.
  • the Tx UE associated with Zone-ID-n implicitly obtains the Zone-ID of the feedback UE associated with Zone-ID-x, where x is a natural number in the range of 0 to N-1, thus Tx UE Retransmission based on beamforming is performed adaptively.
  • the PSFCH resource model is arbitrarily (pre-)configured according to different situations, but each PSFCH resource model is composed of at least two base resources, and Rx UEs located in the same area can share PSFCH resources. If the Rx UE successfully detects the SCI, but fails to decode the data packet, the Rx UE can feed back HARQ NAK to the Tx UE with different PSFCH timings, and gradually increase the AoD resolution through different PSFCH timings.
  • the Tx UE can initially distinguish AoD and identify whether it is Rx UE in a single direction that needs to be retransmitted. Determine whether to use beamforming mechanism for retransmission; gradually improve the AoD resolution by detecting the second or higher PSFCH resource model.
  • a base resource is defined as a basic resource used for the PSFCH, which is used by the feedback UE to send its HARQ NAK.
  • PSFCH-based resources can be defined as frequency domain, time domain or code domain resources.
  • the PSFCH resource model and resource model set depend on the size of the ZB and base resources, and are composed of base resources.
  • Each PSFCH resource model that is combined has an independent index.
  • the PSFCH resource model is configured or pre-configured by RRC.
  • the SCI sent by the Tx UE contains the PSFCH resource model index and PSFCH transmission timing information.
  • the Rx UE uses the PSFCH resource model to feed back the SFCI to the Tx UE, and the Tx UE detects its SFCI signal to identify the HARQ information of the fed back UE and its Zone-ID.
  • the Tx UE gradually improves its AoD resolution through different PSFCH resource models received at different times.
  • Rx UE calculates the AoA (Angle of Arrival) between Tx UE and Rx UE according to their relative position coordinates, so Rx UE selects the PSFCH resource centered on Tx UE Perform HARQ feedback.
  • AoA is quantized by limited bits, and based on (pre)configuration, independent PSFCH resources are allocated to each quantized AoA. Therefore, the PSFCH resource set associated with each multicast transmission is only related to Tx UE and quantized AoA.
  • the Tx UE receives the corresponding PSFCH, it can implicitly calculate the AoD (Angle of Departure) and implement beamforming-based retransmission.
  • the present invention proposes coordinated relay based on location area, in which multiple Tx UEs use the same channel to forward the same data packet to the Rx UE cooperatively to enhance side link coverage.
  • the (pre)configuration of the PSFCH resource pool and the PSCCH resource of the physical side link control channel are redesigned. This new mechanism can also be applied to retransmission based on beamforming.
  • FIG. 1 is a schematic diagram of five UEs in Embodiment 1 performing multi-UE cooperative relay-side link multicast;
  • Fig. 2 is a process transition chart of multi-UE cooperative relay in the first embodiment
  • 3 is a schematic diagram of five UEs in the second embodiment using two independent sub-channels to perform multi-UE cooperative relay;
  • Fig. 5 is a schematic diagram of the area-based cooperative relay side link multicast of the fourth embodiment, in which the Tx UEs associated with Zone-ID-(n-1) and Zone-ID-(n+1) send data packets, The Rx UE associated with Zone-ID-n receives data packets;
  • Zone-ID-n acts as a relay to send data packets
  • Zone-ID-(n-1) and Zone-ID-(n+1) associated Rx UE receives data packets
  • FIG. 7 is a schematic diagram of the (pre)configuration of data channel resources in cooperative relay in the fifth embodiment
  • FIG. 8 is a schematic diagram of cooperative relay and resource selection in the fifth embodiment
  • Fig. 9 is the resource pool (pre-)configuration for PSFCH and the PSFCH resource indication method based on PSCCH in the sixth embodiment, where (a) is a public PSFCH resource pool, (b) is a PSFCH resource pool based on Zone-ID, And both are limited to a single ZB;
  • FIG. 10 is a schematic diagram of PSCCH and PSSCH transmission coupled with PSFCH resources in the sixth embodiment
  • Figure 11 is a schematic diagram of the area-based multi-UE cooperative relay in the sixth embodiment, in which (a) is the initial data packet transmission and reception, (b) is the HARQ NAK feedback of the area-based PSFCH resource, and (c) is the HARQ NAK feedback based on the area Location-based multi-UE cooperative relay retransmission;
  • Figure 12 is a schematic diagram of the area-based multi-UE cooperative relay in the seventh embodiment, in which (a) is initial data packet transmission and reception, (b) is HARQ NAK feedback based on PSFCH resources of the regional layer, and (c) is Location-based multi-UE cooperative relay retransmission;
  • Figure 13 is a simplified schematic diagram of the area-based multi-UE cooperative relay in the seventh embodiment, where (a) is the initial data packet transmission and reception, (b) is the simplified area-based PSFCH resource HARQ NAK feedback, ( c) Retransmit for location-based multi-UE cooperative relay;
  • Figure 14 is the location area assisted retransmission of the eighth embodiment, a) initial transmission and HARQ feedback, b) beam-based retransmission;
  • Figure 17 is an example of the PSFCH model of the Tx UE center.
  • PSFCH model of the Tx UE center there are three or two PSFCH models, a) Type-1 with three PSFCH cases; b) Type-1 with two PSFCH occasions;
  • Figure 18 is an example of a PSFCH model of the Tx UE center. For 16 AoDs, there are 4 PSFCH models and 4 PSFCH opportunities.
  • the present invention provides a side link retransmission method.
  • the present invention will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not used to limit the present invention.
  • the relay function can be implemented by a relay node or a base station, or a Road Side Unit (RSU) placed on the ground, or a mobile cluster cluster head (Mobile Cluster Header), or more generally a vehicle UE. Since the relay node has high antenna gain and large transmission power, its coverage can be much larger. However, outside the coverage area, only the mobile cluster cluster head or the vehicle UE can be responsible for implementing the relay function. In order to enhance the relay coverage, the simple method is to repeat the transmission multiple times, but this method will increase the channel resource cost.
  • RSU Road Side Unit
  • Mobile Cluster Header Mobile Cluster Header
  • Multi-UE Cooperative Relay which allows multiple relay UEs (R-UEs) to simultaneously send the same data packet by using the same resource (a single resource or a limited number of resources).
  • the Tx UE sends data packets to other Rx UEs; some of the Rx UEs successfully detect the data packets, while some Rx UEs fail to detect the data packets.
  • the Rx UE fails to receive one is that the Rx UE receives weak signals or experiences strong interference and the detection fails, and the other is that the Rx UE only installs a half-duplex system.
  • the half-duplex system means that once the UE is in the transmission mode, it cannot receive, and vice versa. Thereby reducing the receiving rate of data packets.
  • the multi-UE cooperative relay method solves two problems. That is, after successfully detecting the data packet, the R-UE re-encodes the same data, and then forwards/retransmits it to other Rx UEs that fail the initial data packet detection or have half-duplex problems. In this process, the R-UE preferably considers forwarding the same data packet in the same resource in order to improve the transmission efficiency of the side chain. Because if the maximum time offset (Timing Offset) between multiple R-UE transmissions is less than or equal to the cyclic prefix (Cyclic Prefix, CP) length, then multiple R-UEs will not send the same coded data packet on the same channel. Produce any inter-symbol interference. Multi-UE cooperative relay can be implemented by Layer-1 relay (Layer-1 Relay) or Layer-2 relay (Layer-2 Relay), as described below.
  • ⁇ Layer-1 relay Only the physical layer is involved in the relay process; among them, only when the data packet is successfully decoded, multiple R-UEs and Tx UEs re-encode the received data packets.
  • the R-UE In the predetermined time slot or the SCI indicator time slot initially sent by the Tx UE, the R-UE must forward the re-encoded data packet on the same physical resource as the Tx UE initially used; that is, the R-UE must use the same PSCCH (Physical Sidelink Control Channel) and its related PSSCH (Physical Sidelink shared Channel).
  • PSCCH Physical Sidelink Control Channel
  • PSSCH Physical Sidelink shared Channel
  • ⁇ Layer-2 relay The relay process involves the physical layer and the MAC layer.
  • the R-UE In the physical layer, only when the data packet is successfully decoded, the R-UE, like the Tx UE, re-encodes the received data packet.
  • the R-UE receives at least one HARQ Negative-acknowledgement (NAK), and the R-UE must forward the recoded data packet on the same physical resource as the Tx UE initially used.
  • NAK HARQ Negative-acknowledgement
  • R-UE only involves simple scheduling (without rescheduling resources), and generally does not need to consider channel conditions, data buffer status (Buffer Status), and priority control (Priority Control). The scheduler only needs to simply determine whether cooperative retransmission should be performed.
  • UEs can be classified into the following two types:
  • Primary R-UE This type of R-UE is designated by the network or group members.
  • the primary R-UE can be a single R-UE or multiple R-UEs, and it must participate in multi-UE coordinated relay unless it does not correctly receive the Tx UE data packet.
  • ⁇ Secondary R-UE This type of R-UE voluntarily participates in multi-UE coordinated relay. In most cases, the secondary R-UE can receive data packets from neighboring Tx UEs, and then forward them to neighboring Rx UEs.
  • whether to configure the primary R-UE and secondary R-UE can be determined according to the implementation situation.
  • ⁇ Primary Relay Resources This type of resource is indicated by the SCI on the PSCCH of the initial data packet and is coupled with the initial data packet. In most cases, it is the same as the resources used by the R-UE for initial data packet transmission.
  • ⁇ Secondary Relay Resources This type of resource is indicated by the SCI on the PSCCH of the retransmitted data packet. Therefore, R-UEs can autonomously select resources for forwarding data packets, and different R-UEs can use different resources.
  • whether to configure the primary relay resource and the secondary relay resource can be determined according to the implementation situation.
  • we do not consider the auxiliary relay resources and only assume that the primary relay resources are used in the multi-UE cooperative relay. In the following, the relay resources are simply unified into resources.
  • Figure 1 is a schematic diagram of five UEs performing multi-UE cooperative relay-side link multicast. As shown in Figure 1, there are five UEs performing multicast based on the multi-UE cooperative relay side link, and two UEs need to multicast data packets. The entire transmission process includes initial multicast, HARQ feedback, and retransmission based on multi-UE cooperative relay. It can be implemented in the following three stages:
  • Stage-1 As shown in Figure 1(a), in the initial multicast process, Tx UE1 and Tx UE3 use different frequency resources to send two data packets in the same time slot, and Rx UE2, Rx UE4 and Rx UE5 To receive.
  • the result of the data packet detection is that Rx UE2 and Rx UE4 successfully detect the data packet sent by the data channel (for example, PSSCH), but Rx UE5 fails to detect the corresponding data packet.
  • the control channel for example, PSCCH
  • the Rx UE can always obtain SCI information by decoding the data on the control channel, so as to know whether the corresponding data packet is also sent.
  • Phase-2 As shown in Figure 1(b), in the HARQ NAK feedback process, it depends on Option-1 (Option-1) HARQ feedback mechanism (it can also depend on Option-2), Rx UE5 is in two PSFCH Two side-chain feedback control information (Sidelink Feedback Control Information, SFCI) are sent on the upper side, and other UEs receive it. Note that under normal circumstances, the PSFCH works in the low signal-to-noise ratio (SNR, such as -5 to -3dB) range, and has a lower bit error rate (BER) than the data channel, so the reliability will be higher.
  • SNR signal-to-noise ratio
  • BER bit error rate
  • Stage-3 As shown in Figure 1(c), during the retransmission process, Rx UE2 and Rx UE4, which are relay UEs, successfully detect two data packets, and then re-encode them separately according to the decoded SCI information , And then forward it to other UEs.
  • Rx UE2 and Rx UE4 forward each data packet to be superimposed on an independent channel, and then are received by UE1 and UE3.
  • UE1 and UE3 detect the corresponding data packets, which solves the half-duplex problem.
  • UE5 receives each data packet, performs HARQ soft combination with the previous buffered data, and then decodes it, thereby realizing the retransmission process of the cooperative relay of multiple UEs.
  • Figure 2 depicts a process transition chart of multi-UE cooperative relay based on the same example.
  • Tx UE can use an explicit mechanism (Explicit) or an implicit mechanism (Implicit) to notify the PSFCH resource index for HARQ feedback and re-use.
  • the explicit mechanism is to use SCI to notify related resources; while the implicit mechanism is to couple the PSSCH resource index of the initial transmission with the resource index and retransmission resource index used for HARQ feedback.
  • Resource coupling can be performed in the time domain or the frequency domain, or both. If resource coupling is performed in the time domain, the resources in the frequency domain must be indicated by the SCI. Likewise, if resource coupling is performed in the frequency domain, the resources in the time domain must be indicated by the SCI.
  • Rx UE-5 feeds back HARQ NAK, and all UEs can receive it. Note that if there is no NAK feedback, the PSCCH+PSSCH resource indicated by the SCI in the initial data packet can be used by other Tx UEs. In other words, the resources reserved by the SCI will be automatically released.
  • Retransmission is usually triggered by HARQ NAK, and retransmission triggered by Tx UE half-duplex may depend on the area information of the Tx UE. This requires careful regularization of how to specify the operation of potential R-UEs in the MAC layer.
  • a single UE assisted relay In a single-UE assisted relay, only one R-UE is designated to participate in the reception from the Tx UE, and the received data packet is re-encoded, and then forwarded to the Rx UE that failed to receive the initial data packet. If the R-UE receives the initial data packet incorrectly, the relay retransmission will not be possible, resulting in a decrease in overall performance.
  • multi-UE cooperative relay multiple R-UEs are involved in receiving data packets from Tx UEs, and each of them re-encodes the received data packets, and then forwards them to the Rx UEs that failed to receive the initial data packets. In this way, the probability of successful relay will be significantly improved.
  • Multi-UE cooperative relay can provide at least three benefits:
  • the Rx UE as a relay UE can achieve retransmission. This greatly increases the probability of successful retransmission and can provide significant transmit diversity gain.
  • Figure 3 shows an example of initial transmission and retransmission, where five UEs can respectively use two independent sub-channels (Sub-channel) and need to transmit three data packets (Packet-1, Packet-2, Packet-3) at the same time .
  • ⁇ means that the data packet is decoded successfully, and ⁇ means that the decoding failed.
  • Tx UEs (UE1, UE3, UE4) send initial data packets in slot-1 (Slot-1) and slot-2 (Slot-2).
  • the R-UE performs data packet retransmission in slot-3 (Slot-3) and slot-4 (Slot-4).
  • the initial transmission in Slot-1 (Slot-1) and the retransmission in Slot-3 (Slot-3) are the same as the example in Figure 1, thereby solving the problem of relay retransmission and half-duplex.
  • the transmission in slot 2 (Slot-2) and slot 4 (Slot-4) is relatively simple, in which only a unique initial data packet is sent and retransmitted by UE3, UE4 and UE5.
  • the XoR (eXclusive OR) coding mechanism can be used to improve the transmission performance. For example, in slot-1 (Slot-1), if Rx UE-5 can detect one of data packet-1 and data packet-2, R-UE2 and R-UE4 can compare data packet-1 and Data packet-2 is XoR encoded, and a new data packet after XoR encoding is sent. The Rx UE decodes the XoR and then detects its own corresponding data packets, which can reduce the retransmission channel resources by half.
  • slot-1 slot-1
  • R-UE2 and R-UE4 can compare data packet-1 and Data packet-2 is XoR encoded, and a new data packet after XoR encoding is sent.
  • the Rx UE decodes the XoR and then detects its own corresponding data packets, which can reduce the retransmission channel resources by half.
  • the communication range can be divided into QoS communication range (QoS Communication Range, QCR) and radio communication range (Radio Communication Range, RCR).
  • QCR QoS Communication Range
  • RCR Radio Communication Range
  • the former is associated with the reliability of data packets required in QoS
  • the latter is associated with the physical distance between the Tx UE and the Rx UE that the transmitted radio waves can reach.
  • Figure 4 shows the relationship between area coverage and radio power intensity, where the radio power of the Tx UE located in the area is the largest, and then gradually decreases, thereby affecting the side link coverage.
  • radio waves are transmitted from the central area associated with Zone-ID-n, where Rx UEs associated with the same area can detect high power, which ensures low packet error rate (PER) and improves reliability .
  • This high power area is shown by the thick circled line.
  • This medium power area is defined as RCR and is shown by the dashed circle.
  • Multi-UE cooperative relay can expand the coverage, but it does not mean that the more UEs involved in cooperative relay, the better the relay performance. Therefore, it is very important to clarify the number of UEs and UE types that need to be involved in cooperative relay. In the present invention, we consider that only UEs associated with some Zone-IDs can be used as R-UEs.
  • the Tx UE sends the SCI and the associated PSSCH through the PSCCH, and the Rx UE receives the SCI and obtains QCR information. Only in the QCR range, the Tx UE judges whether to feed back ACK/NAK according to the PSSCH decoding status.
  • the QCR information can be indicated by the SCI in an explicit or implicit way.
  • the explicit way is that the SCI carries a specific dedicated bit (for example, 3 bits) and directly indicates the QCR to the Rx UE.
  • the implicit method is that the SCI does not carry any additional bits, but reuses existing packet priority information (for example, Priority Information, 3 bits) to indirectly indicate the QCR. Therefore, the implicit method needs to formulate and standardize (pre-)configure the mapping rules between QCR and packet priority.
  • the number of UEs involved in cooperative relaying can be based on the QCR information indicated by the SCI, and/or data packet priority information, and/or the zone-ID relationship of the transceiver end, etc., and the candidate R-UE judges whether it should participate in the cooperation.
  • the number of R-UEs is not determined uniformly by the system, but can adaptively depend on the QoS and other requirements of each data packet. For example, the R-UE obtains the distance from the HARQ feedback UE through Zone-ID, obtains QCR information and/or data packet priority information through SCI instructions, and then determines whether it should participate in cooperative relay according to predetermined rules or algorithms.
  • Zone-ID information we simply consider Zone-ID information to control and limit the number of UEs participating in cooperative relay.
  • XoR coding (XoR-coding, including encoding and decoding) can be divided into two types; Type-1XoR-coding (Type-1XoR-coding) is carried out at the physical layer, so the physical layer structure and physical layer procedures need to be standardized, and the type -2XoR coding (Type-2XoR-coding) is carried out at the MAC layer, so MAC layer specifications are required (at the same time, some physical layer corresponding specifications may also be required).
  • Type-1XoR-coding (Type-1XoR-coding) is carried out at the physical layer, so the physical layer structure and physical layer procedures need to be standardized
  • Type-2XoR coding (Type-2XoR-coding) is carried out at the MAC layer, so MAC layer specifications are required (at the same time, some physical layer corresponding specifications may also be required).
  • Type-1 XoR coding the MAC layer provides more than two TBs to the physical layer, which are sent by the Tx UE to the Rx UE through the wireless transmission link.
  • the scheduler in the MAC layer will notify the physical layer which TBs should XoR each other after channel coding.
  • the Tx UE sends the XoR-encoded TB to the Rx UE, and the Rx UE performs XoR decoding on the received TB before channel decoding.
  • the advantage of using Type-1 XoR coding is to enhance link performance through HARQ with soft combining, while improving channel efficiency.
  • the disadvantage is that it increases the specification work of the physical layer.
  • Type-2 XoR encoding the MAC layer prepares and generates XoR-encoded TB, which is then provided to the physical layer. Therefore, the physical layer does not need to know the information encoded by XoR, so there is no need to change the physical layer structure.
  • the advantage of using Type-2XoR coding is that it can improve channel efficiency, but does not require too many physical layer specifications. However, the disadvantage is that the physical layer will lose the data packet soft combining gain in the HARQ process.
  • Type-2 XoR coding is called network coding (Network Coding).
  • Layer-1 control signaling can effectively assist and realize Layer-2 relay.
  • the functions between Layer-1 and Layer-2 should be integrated with each other in order to effectively improve system performance.
  • HARQ feedback signaling and Layer-1 measurement information RSRP
  • RSRP Layer-1 measurement information
  • the definition of the area is limited to latitude, but it can be simply extended in longitude and latitude.
  • Figure 5 illustrates multiple areas, where each area is assigned a dedicated resource pool represented by a different color.
  • the RCR between UEs is the distance from the edge of one area to the edge of its neighboring area
  • QCR is the distance from the edge of one area to the edge of its next neighboring area (across three areas) .
  • QCR is greater than RCR, which causes communication coverage problems.
  • This application proposes coordinated relay based on location area and relies on the mutual cooperation of multiple R-UEs in the area.
  • the UE located in Zone-ID-n can be used as the R-UE.
  • the data packet will need to be sent from the Tx UE in Zone-ID-(n-1) to the Rx UE in Zone-ID-(n+1).
  • the data packet will also need to be sent from the Tx UE in Zone-ID-(n+1).
  • the Tx UE in +1) is sent to the Rx UE in Zone-ID-(n-1).
  • R-UE performs relay retransmission in two stages:
  • Tx UE associated with Zone-ID-(n-1) and Zone-ID-(n+1) sends initial data packets, and with Zone-ID-(n-1), Zone- The Rx UE associated with ID-n, Zone-ID-(n+1) receives the data packet.
  • All Rx UEs in the same area of Tx UE can successfully detect data packets. Due to the fading channel (Fading Channel) change, some Rx UEs in the neighbor area associated with Zone-ID-n can detect data packets and have a fairly high success rate. However, the Rx UE in the next neighboring area can occasionally detect data packets, but has a rather low success rate.
  • Phase-2 Cooperative relay will rely on multiple UEs in the same area to perform retransmission.
  • the four R-UEs associated with Zone-ID-n voluntarily send re-encoded data packets, which are related to Zone-ID-(n-1) and Zone-ID-(n+1)
  • the connected Rx UE receives the corresponding relayed data packet.
  • the cooperative relay mechanism can be extended to an area composed of N x ⁇ N y longitude and latitude, where Zone-ID can be marked as 0,1,...,N x N y .
  • the initial data packet transmission can be performed by the Tx UE in the following Zone-ID (Type-1 zone) in the time slot t,
  • Zone-ID y 1 N x +x 1 , if (x 1 mod2) ⁇ (y 1 mod2);
  • the initial packet transmission and relay-based retransmission can be sent in Type 1 (time slot t) and type 2 areas (time slot t+ ⁇ ), respectively, while another initial data packet transmission and relay-based corresponding Retransmissions will be switched to each other and can be sent in Type 2 (time slot t+1) and Type 1 areas (time slot t+1+ ⁇ ).
  • the XoR coding mechanism can be combined to perform multi-UE cooperative relay, so as to better improve the transmission efficiency.
  • Tx UE-i n-1 associated with Zone-ID-(n-1) sends data packets The data packet will be successfully received by all Rx UEs in its own area.
  • the data packet was successfully received by the Rx UE associated with Zone-ID-n.
  • the data packet cannot be received by the Rx UE associated with Zone-ID-(n+1).
  • the Tx UE-in+1 associated with Zone-ID-(n+1) sends data packets The data packet will be successfully received by all Rx UEs in its own area.
  • R-UE-i n XoR encoded data packet Forward to Rx UEs in the two neighboring areas associated with Zone-ID-(n-1) and Zone-ID-(n+1).
  • all Rx UEs associated with Zone-ID-(n-1) know the data packet in advance And by XoR decoding to detect Similarly, the Rx UE associated with Zone-ID-(n+1) can perform the same XoR decoding detection.
  • the resources of the R-UE associated with Zone-ID-n and forwarding XoR-encoded data packets can be reduced by half.
  • the R-UE In order for the R-UE associated with Zone-ID-n to perform cooperative relay-based retransmission, the R-UE must determine which data packets should be retransmitted and how to implement XoR-encoded retransmission.
  • the determination of the retransmission of the data packet depends on the type of HARQ feedback. Based on the HARQ feedback mechanism, NR-V2X supports two HARQ feedback options.
  • Option-1 If the Rx UE fails to decode the corresponding TB after decoding the associated PSCCH, the Rx UE sends HARQ-NAK on the PSFCH. Otherwise, it does not send any signal on the PSFCH.
  • ⁇ Option-2 (Option 2): If the Rx UE successfully decodes the corresponding TB, it sends HARQ-ACK on the PSFCH. If the Rx UE fails to decode the corresponding TB after decoding the associated PSCCH, the Rx UE sends HARQ-NAK on the PSFCH.
  • Alternative-1 If the data packet decoding fails, the Rx UE feeds back HARQ-NAK.
  • the PSFCH resource is only coupled with the initial transmission data packet.
  • This scheme belongs to Option-1 (Option-1).
  • the failed data packets must be retransmitted one by one by multiple R-UEs associated with Zone-ID-n. Taking the example in FIG. 6, a maximum of eight independent PSCCH/PSSCH resources are required to achieve retransmission.
  • Alternative-2 If the decoding of the data packet fails, the Rx UE feeds back HARQ-NAK.
  • the PSFCH resource is coupled with the initial transmission data packet and the Zone-ID of the feedback Rx UE. This means that the R-UE receiving the feedback HARQ-NAK can potentially identify the Zone-ID from the feedback UE.
  • This scheme also belongs to Option-1 (Option-1).
  • the R-UE associated with Zone-ID-n knows the reception status of the respective zones associated with Zone-ID-(n-1) and Zone-ID-(n+1). Therefore, the data package can be with XoR coding is implemented between them in order to reduce the retransmission channel resources used for R-UEs, thereby improving transmission efficiency.
  • Option-3 (Alternative-3): Rx UE feeds back HARQ ACK/NAK based on Option-2.
  • the feedback channel is coupled with the sent data packet and the feedback Rx UE. This means that when receiving HARQ ACK/NAK, the R-UE can identify the Rx UE ID from the feedback. Through the feedback information, the R-UE associated with Zone-ID-n knows the respective reception status of the Rx UEs in the three areas. This will add more retransmission packets to participate in the implementation of XoR coding opportunities.
  • the cooperative relay XoR coding in Scheme-3 is not always effective, and it depends heavily on the receiving state.
  • XoR coding should mainly rely on Scheme-2 to perform, and once the XoR coding conditions in Scheme-3 can be met, scheme-3 can be selectively used for execution. Because, the total resources used for option 3 must be less than the resources required for option 2.
  • the communication range is also different according to the data packets of different QoS requirements.
  • QCR can be extended to more areas, while RCR generally remains the same. Therefore, it will become more difficult to satisfy the QoS in the communication range, that is to say, it will become more challenging to rely on a constant RCR to realize side link communication with a large coverage area. For this reason, the same cooperative relay method is used, while the traditional multi-hop relay mechanism is adopted, and the side link communication with a large coverage area can be realized by combining the cooperation between multiple areas.
  • the half-duplex problem is one of the biggest problems in resource selection.
  • the resources used for retransmission are coupled with the resources used for initial transmission, so that the retransmission resources are transparent to all Rx UEs. This needs to be standardized for the resource (pre-)configuration and resource selection process.
  • TDM Time Division Multiplexing
  • DPR Data Packet Resource
  • CRR cooperative relay resource
  • Both DPR and CRR are associated with Zone-ID and use the same number of resources in the frequency domain, represented by L ZONE sub-channels (Sub-channel, SCH, each containing L ZONE Resource Blocks, RBs), which are owned in the time domain
  • L ZONE SCH and L DPR time slots form a DPR SCB block (SCH Block, SCB), and L ZONE SCH And L CRR time slot form the SCB block of CRR
  • DPR the resource of the smallest transmission unit of SCH is denoted as DPR n,t (p)
  • CRR the resource of the smallest transmission unit is denoted as CRR n,t (p );
  • n Zone-ID
  • t is the time slot index in the time domain
  • p is the index of the SCH in the frequency domain
  • the parameters of L ZONE , L SCH , L DPR and L CRR are determined
  • the DPR resource associated with Zone-ID-n in the second time slot and the third SCH can be expressed as DPR n,2 (3), and in the fifth time slot and the first SCH
  • the resources of the CRR associated with Zone-ID-(n+1) can be expressed as CRP n+1,5 (1).
  • the frequency domain and/or time slot resources used in the HARQ feedback process should be reserved between DPR and CRR.
  • the resource selection procedure should consider reducing the control signal overhead, which requires coupling the resources used for DPR with the resources used for CRR, so that all R-UEs involved in cooperative relay can implicitly select the same resource without any additional Control information. For this, the following predetermined rules should be considered:
  • the retransmission resources in the SCB of the CRR associated with the Zone-ID-n involved in the cooperative relay should correspond to those of Zone-ID-(n-1) and Zone-ID- (n+1)
  • the initial transmission resource in the SCB of the associated DPR In the time domain, the SCB of DPR and the SCB of CRR should be adjacent to each other.
  • ⁇ XoR encoded data packet sequence Based on the HARQ feedback mechanism, all UEs in the RCR can obtain the receiving state of the initial data packet. Depending on the specified rules, each R-UE can determine which XoR-encoded data packets need to be sent sequentially, for example, number the data packets in ascending order.
  • the XoR-encoded data packets should be sorted numerically according to the initial data packets associated with Zone-ID-(n-1) and time slots, and then associated with Zone-ID-(n+1) and time slots.
  • the initial packet This ensures that the numbers of all XoR encoded data packets will not conflict.
  • ⁇ CRR resource sequence In the (pre)configuration of each SCB resource pool, the resources are also numbered in sequence. For example, sort in ascending order.
  • the resource order may be predetermined from the direction of the slot index, and then determined from the direction of the SCH index. In this way, two-dimensional SCB resources can be formed.
  • ⁇ Resource selection The R-UE involved in the cooperative relay selects the resources of the (pre-)configured CRR in its own SCB.
  • the selection of resources is simply based on the one-to-one mapping method between the XoR-encoded data packet sequence and the CRR resource sequence.
  • this embodiment gives an example, as shown in FIG. 8.
  • Tx UE UE n-1,1 associated with Zone-ID-(n-1) and Tx UE UE n+1,1 associated with Zone-ID-(n+1) Select DPR n-1,1 and DPR n+1,1 to send the initial data packets S n-1,1 and S n+1,1 respectively.
  • These two data must be successfully received by all Rx UEs in the QCR, and the QCR spans the zone of Zone-ID-(n-1), Zone-ID-n and Zone-ID-(n+1).
  • Tx UE UE n-1,2 and S n+1,2 associated with Zone-ID-(n-1) and Zone-ID-(n+1) select DPR respectively n-1,2 and DPR n+1,2 to complete the transmission and reception of the initial data packets S n-1,2 and S n+1,2.
  • cooperative relay is performed in the reserved CRR, and the initial data packet in time slot-1 and time slot-2 in the adjacent area is retransmitted respectively.
  • CRR n,3 cooperative relay mainly assists the retransmission of data packets S n-1,1 and S n+1,1 .
  • CRR n,4 and CRR n+1,4 cooperative relay mainly assists data packets S n-1,2 and S n+1,2 , respectively, and S n,2 and S n+2,2 Retransmission.
  • data packets S n-1,1 and S n+1,1 are composed of Tx UE (UE UE) associated with Zone-ID-(n-1) and Zone-ID-(n+1).
  • n-1,1 and UE n+1,1 are sent and successfully received by three other UEs associated with the same Zone-ID.
  • the same data packet is not successfully received by the Rx UE associated with the next neighboring Zone-ID.
  • the same data packet cannot be received by UE n,1 associated with Zone-ID-n.
  • the data packets are The XoR codes of the three R-UEs respectively generate A n, i, t , and they are autonomously sent on the CRR n, 3 resources in time slot-3 in a cooperative relay manner, that is
  • n is the index of Zone-ID
  • UE n,1 associated with Zone-ID-n is affected by half-duplex, and UE n,3 associated with Zone-ID-n cannot be correctly connected to Zone-ID-( n-1)
  • Embodiment 6 is a diagrammatic representation of Embodiment 6
  • Link control information can be divided into two types; one is related to side link control information (Sidelink Control Information, SCI) transmitted through the physical side link control channel (Physical Sidelink Control Channel, PSCCH), and the other is through Sidelink Feedback Control Information (SFCI) transmitted by the Physical Sidelink Feedback Channel (PSFCH).
  • SCI Sidelink Control Information
  • SFCI Sidelink Feedback Control Information
  • PSFCH Physical Sidelink Feedback Channel
  • the relay function can be realized through multi-UE coordinated transmission. However, this does not mean that the more UEs participating in cooperative relaying, the better the system performance. There are at least two reasons for limiting the number of cooperative R-UEs:
  • the R-UE Once the R-UE participates in cooperative relay, it must forward the data packet to the corresponding Rx UE. Due to half-duplex restrictions, the R-UE cannot receive at the same time. This will reduce overall system performance.
  • the cooperative relay must be autonomously performed by a limited number of voluntary R-UEs, and the geographic location information can be used to decide whether to participate in the cooperative relay, so no additional feedback information is required.
  • PSSCH and PSCCH resource pools can be separately (pre-)configured according to Zone-ID.
  • PSFCH resource pools should also consider the same (pre-)configuration method .
  • the resource pools used for PSFCH can be divided into two categories: one is related to the public resource pool and has nothing to do with the geographical location of the UE. Any UE can use the public resource pool; the other is related to the Zone-ID-based resource pool. Related to the resource pool, the resource pool can only be used by UEs located in the same area.
  • the public PSFCH resource pool is (pre-)configured, in which any UE can select PSFCH resources for HARQ feedback.
  • the PSFCH resource can be coupled with the PSCCH/PSSCH resource, and the coupled information can be indicated by the SCI sent by the PSCCH, or be mapped to each other by (pre)configuration.
  • SCI SCI
  • the PSCCH must be used to transmit the relevant SCI and at the same time indicate the resources of the PSFCH. There is a certain time interval between the PSCCH and its related PSFCH.
  • the Tx UE transmits SCI information through the PSCCH, and transmits related transport blocks (Transport Block, TB) through the PSSCH, and the SCI contains public PSFCH resource index information.
  • the Rx UE receives the SCI and its related data packets and detects whether there are errors.
  • the HARQ feedback on the side link is triggered only when the Rx UE detects an error in the received data packet.
  • all Rx UEs use the same PSFCH resource to feed back HARQ NAK.
  • the PSFCH resource is only coupled with the initial data packet sent initially, and the Zone-ID associated with the feedback Rx UE cannot be distinguished. of.
  • ⁇ Indication bit in SCI The bit represents the selected index m.
  • the Zone-ID-based PSFCH resource pool can be independently (pre-)configured, wherein only UEs located in the same Zone-ID can select PSFCH resources for HARQ feedback.
  • the SCI will be used to indicate the PSFCH resource based on Zone-ID, where there is a uniform time interval between the PSCCH and the associated PSFCH.
  • the Tx UE multicasts SCI messages and related TBs through the PSSCH and PSSCH, and the SCI information includes a uniform index-1 for different Zone-IDs to indicate the PSFCH resources associated with the Zone-ID.
  • Rx UE receives SCI and related data packets, and detects whether there is an error.
  • the Rx UE Only when the Rx UE detects an error in the received data packet, the Rx UE will use the PSFCH resource associated with the same Zone-ID at its location to trigger the corresponding HARQ feedback. Among them, the feedback UE can be distinguished based on the zone-ID identification in each ZB, but the cost is that more PSFCH resources need to be used. In fact, if the (pre-)configured PSFCH resource pool is region-based, then N times resources need to be reserved for the PSFCH. The PSFCH resource reduction scheme will be discussed in Embodiment 7.
  • the number of PSFCH indication bits in the SCI is unchanged. This is because although the configuration of the area-based resource pool requires more parameters in the higher layers, only one index is required in these two cases.
  • the (pre-)configuration of the area-based PSFCH resource pool and the indication of the SCI for the PSFCH resource can be summarized as:
  • ⁇ Indication bit in SCI The bit represents the selected index.
  • the Tx UE and the R-UE can implicitly obtain the index n based on the blind detection of the PSFCH resource associated with the Zone-ID.
  • the three resource pools represented by Pool-1, Pool-2 and Pool-3 are (pre-)configured in Zone-ID-0 , Zone-ID-1, Zone-ID-2 in the three areas, among them, these areas have UE-1, UE-2, UE-3 respectively.
  • the resource pool only contains frequency resources.
  • Tx UE-1 in time slot-1 sends SCI information through the PSCCH, and sends its associated TB through the PSSCH corresponding to Zone-ID-0 (or resource pool-1).
  • the SCI contains indication information of PSFCH resources.
  • both Rx UEs learn the resource information of PSFCH-2 and PSFCH-3 allocated in time slot-4, and compare with the PSCCH of Tx UE-1 /PSSCH are coupled. Among them, PSFCH and PSCCH have an interval of two time slots.
  • Rx UE-2 and Rx UE-3 respectively determine whether the HARQ-NAK needs to be fed back to Tx UE-1 by decoding the associated TB.
  • Rx UE-2 Due to geographic relations, Rx UE-2 is close to Tx UE-1, and Tx UE-3 is far away from Tx UE-1. As a result, Rx UE-2 can correctly decode data packets on the PSSCH, but Rx UE-3 cannot. Due to the HARQ NAK feedback mechanism, Rx UE-3 feeds back the corresponding NAK to Tx UE-1 through PSFCH-3, while Rx UE-2 has been instructed to allocate PSFCH-2 but does not feed back any HARQ information. It should be emphasized that Rx UE-2 does not send any data in time slot-4, so it can receive SFCI from Rx UE-3. This is the beneficial reason for relying on the side link HARQ feedback of option-1 in the multi-UE cooperative relay. Also due to geographic relations, Rx UE-2 can ensure that SFCI is detected on PSFCH-3, but Tx UE-1 cannot.
  • Rx UE-2 can receive the SCI information of PSCCH and the feedback information of PSFCH-3, it knows the location of Tx UE-1 and Rx UE-3 respectively. Therefore, Rx UE-2 is voluntarily responsible Retransmission based on cooperative relay. In addition, from the perspective of geographic location, Rx UE-2 has a better transmission link than Tx UE-1, and the gain will be higher. Similarly, this example can be extended to multi-UE cooperative relay.
  • the UEs located in different areas are represented as UE-i, as shown in Figure 11, where the one located in Zone-ID-4 Tx UE-5 sends initial data packets, and other Rx UEs located in other areas receive correspondingly.
  • the Rx UE located in the RCR (in the center and the first layer, surrounded by thick lines) can correctly decode data packets, while the Rx UE is located outside the RCR but within the QCR (in the second layer, surrounded by thin lines) , The data packet may not be received correctly.
  • Rx UE-1 and Rx UE-11 in the second layer failed to receive data packets from Tx UE-5.
  • Rx UE-1 and Rx UE-11 will send two corresponding SFCI (NAK ) To Tx UE-5, and at the same time, it is also received by other UEs. Due to geographic reasons, only some UEs can detect SFCI and implicitly obtain their corresponding regional locations.
  • UE-2, UE-3,..., UE-6 can detect SFCI from Rx UE-1 and obtain its regional location
  • UE-5, UE-6,..., UE-10 can Rx UE-11 detects SFCI and obtains its regional location. Therefore, the UE that correctly detects the SFCI can become a candidate for multi-UE cooperative relay, and the UE among the candidates close to the feedback UE can voluntarily perform cooperative relay retransmission.
  • R-UE-2 and R-UE-3 as a relay cooperate to participate in the retransmission for Rx UE-1
  • R -UE-9 and R-UE-10 cooperate to participate in the retransmission of Rx UE-11. Since the cooperative relay uses the same channel, Rx UE-1 and Rx UE-11 do not need to distinguish which R-UEs participate in the cooperative relay retransmission.
  • the number of UEs participating in multi-UE coordinated relay retransmission is determined independently by the mutual area location between UEs. This can produce many benefits:
  • ⁇ It can significantly improve the coverage of PSFCH. This is because the Tx UE transmitting the initial data packet may not necessarily be able to detect the corresponding SFCI on the PSFCH, while the R-UE close to the feedback Rx UE can correctly detect the SFCI.
  • Zone-ID corresponding to the feedback UE can be implicitly obtained by other UEs, and only a part of R-UEs participate in cooperative relay. Therefore, from a half-duplex perspective, the system efficiency is greatly improved.
  • PSFCH resources are allocated in each zone layer (Zone-Tier).
  • PSFCH resource allocation is centered on the Tx UE involved in the initial transmission. This means that the first PSFCH resource is allocated to the central area where Tx UE is located, the second PSFCH resource is allocated to the first layer area centered on Tx UE, and so on, the k-th PSFCH resource is allocated to Tx
  • the UE is the central (k-1)th layer area until the last area layer in the QCR. Therefore, the number of PSFCH resources depends on the number of zone layers in the QCR, not the number of Zone-IDs.
  • all PSFCH resources are associated with PSCCH/PSSCH used for initial data packet transmission.
  • the Rx UE needs to explicitly or implicitly acquire the regional layer relationship with the Tx UE.
  • the number of PSFCH resources in each regional layer should be individually (pre-)configured, and the rule is M 0 ⁇ M 1 ⁇ ... ⁇ M K-1 , where K is the number of regional layers in the QCR. If the resource indication is performed separately for each regional layer, it may cause K times the signaling overhead to indicate the PSFCH resource in the SCI.
  • Figure 12 illustrates a multi-UE cooperative relay, where PSFCH resource allocation based on the regional layer is considered.
  • Figure 12(a) shows the transmission and reception of the initial data packet
  • Figure 12(c) shows the multi-UE cooperative relay transmission (same as the example in Figure 11).
  • Figure 12(b) the only difference is HARQ NAK feedback based on regional layer PSFCH resources, where three independent PSFCH resources are allocated in the central region, the first regional layer (light gray), and the second In the region layer (dark gray).
  • Each Rx UE detects the SCI on the PSCCH from Tx UE-5, and then determines which zone layer the Rx UE is located in based on the Zone-ID of the center Tx UE-5 and the Zone-ID of the Rx UE.
  • Rx UE-1 and Rx UE-11 will send two corresponding SFCIs (NAKs) to Tx UE-5 through the two PSFCHs associated with the second regional layer, and at the same time, they will be received by other UEs. Therefore, UE-2 and UE-3 detect SFCI from the feedback Rx UE-1, and UE-8, UE-9 and UE-10 detect SFCI from the feedback Rx UE-11.
  • UE-2 and UE-3 cooperate to participate in the retransmission for Rx UE-1, while UE-8, UE-9 and UE-10 cooperate to participate in the retransmission for Rx UE-11.
  • the Rx UE can obtain the regional location of the Tx UE through the location coordinates, the Rx UE can calculate the distance between the Tx UE and the Rx UE, thereby deriving which regional layer the Rx UE belongs to.
  • Zone-ID does not need to be configured, as shown in Figure 13, the zone layer can be simplified.
  • the Tx UE needs to multicast its location coordinates, while the Rx UE only needs to know its own coordinates.
  • each device is configured with multiple resource pools, each of which is associated with a reference signal
  • the received power (Reference Signal Received Power, RSRP) range is associated.
  • RSRP Reference Signal Received Power
  • the zone-tier width (in meters) and the number of zone-tiers in the QCR must also be (pre-defined). ) Configured. Therefore, the allocation mechanism based on the regional layer can significantly reduce PSFCH resources.
  • each Tx UE transmits location information on a data channel (eg, PSSCH channel) through RRC parameters, and each Rx UE updates the location information in the location table through the RRC parameters.
  • the location table should include the location information of the Tx UE and the relevant ID of the Tx UE.
  • the UE can receive the Tx UE ID indicated by the SCI, then look up the Tx UE ID in the RRC location table, and then implicitly obtain the corresponding Tx UE ID. Therefore, the Tx UE only needs to send its UE ID through the SCI, and does not need the SCI to directly transmit location information.
  • each PSFCH is associated with its UE ID. Therefore, as long as the Rx UE has sent its location to other UEs through RRC parameters, each Tx UE can know the location of each Rx UE.
  • Embodiment 8 is a diagrammatic representation of Embodiment 8
  • Retransmission may also rely on the transmit beamforming (Transmit Beamforming) mechanism.
  • Transmit Beamforming transmit Beamforming
  • the directions of receiving radio waves from Tx UEs are also different, so the initial transmission that relies on sending beamforming is not feasible.
  • such physical constraints are obviously reduced because the error probability of Rx UE receiving the initial packet is relatively low, that is, the number of UEs that need to be retransmitted in multicast is correspondingly reduced. This provides a unidirectional Rx UE beamforming transmitter opportunity for Tx UE.
  • Transmit beamforming can provide the following benefits:
  • the Tx UE can effectively use the high frequency band in the millimeter wave (mm Wave) (for example, the new ITS frequency band).
  • mm Wave millimeter wave
  • the transmitting and receiving beam width is much narrower than the microwave beam. Therefore, the narrow beam width leads to higher requirements for beam alignment between the transmitting end and the receiving end.
  • very high beam alignment sensitivity is required.
  • L1 control information eg, PSFCH
  • PSFCH L1 control information
  • the Tx UE In order to achieve transmit beamforming, the Tx UE needs transmit angle (Angle of Departure, AoD) information. For this reason, considering that the UE vehicle is running at a high speed, the Tx UE must obtain channel status information (Channel Status Information, CSI) feedback. This will greatly increase the feedback signaling overhead of the physical layer. In contrast, relying on the HARQ feedback mechanism can also obtain retransmitted AoD information based on beamforming without any additional signaling. Through Zone-ID-based PSFCH resource pool information associated with the PSCCH, or PSFCH resource information activated by the PSCCH, the Tx UE can implicitly obtain the location area associated with the HARQ feedback UE, thereby deriving the relevant AoD.
  • AoD Angle of Departure
  • Figure 14 illustrates beamforming-based retransmission assisted by the location area between Tx UE and Rx UE, which is performed in three transmission stages:
  • Tx UE-5 located in Zone-ID-4 performs initial data packet transmission through PSCCH and its associated PSSCH, while Rx UEs located in other areas receive correspondingly. Most Rx UEs can decode data packets correctly, but only a few Rx UEs decode incorrectly. As shown in Figure 14(a), only Rx UE-3 received the data packet in error.
  • the resources of the PSFCH used for the HARQ feedback of the Rx UE are (pre)configured.
  • the Rx UE uses the resources of the PSFCH or is associated with the PSCCH, or indicated on the PSCCH by the SCI, and is coupled with the Tx UE.
  • the Rx UE that decodes the error relies on the option-1 (Option-1) feedback mechanism to send the corresponding SFCI (NAK) through the activated PSFCH.
  • Option-1 Option-1
  • Rx UE-3 feeds back its corresponding HARQ NAK to Tx UE-5 through PSFCH.
  • Tx UE-5 implicitly obtains its location Zone-ID by detecting the SFCI on the PSFCH, and derives the AoD.
  • the resolution of the obtained AoD is about 45°.
  • the Rx UE that fails to receive may be far away from the Tx UE, and is generally located in the next neighbor area of the second layer or even more, but the resolution is the same.
  • the Tx UE sends data packets to the Rx UE by beamforming according to the derived AoD.
  • Tx UE-5 points the antenna beam to Rx UE-3 and sends data packets to Rx UE-3, which ensures the reliability of the retransmission link.
  • the retransmission should be performed adaptively by the Tx UE. Because, in some cases, beamforming-based retransmission may not be possible, such as:
  • ⁇ Tx UE and Rx UE are located in the same area, so AoD cannot be derived.
  • this situation rarely occurs because the radio link between the Tx UE and the Rx UE in the same area is generally good enough. In other words, if HARQ option-1 is considered, HARQ NAK feedback is not required.
  • ⁇ Tx UE detects multiple Rx UEs fed back by NAK, and these Rx UEs are in different areas. Generally, the antenna beam can only be adjusted to a single direction, and the multi-region situation cannot be dealt with.
  • Beam forming mechanism of the present disclosure can facilitate the retransmitted data packet, but is independent of resources will increase PSFCH N x ⁇ N y times. Therefore, we newly designed PSFCH resources with multiple patterns (Pattern), the purpose is to minimize the use of PSFCH resources, but at the same time can still obtain the feedback of the UE Zone-ID by detecting the PSFCH.
  • the PSFCH resources used for SFCI transmission are (pre-)configured or activated through the SCI on the PSCCH.
  • the PSFCH resource model can be divided into two types: one is the PSFCH resource model based on zone block (ZB), and the other is the PSFCH resource model centered on Tx UE.
  • ZB zone block
  • this embodiment proposes a new HARQ feedback procedure; it mainly uses Distributed PSFCH Resource Patterns (DFRP) to greatly reduce PSFCH resources.
  • DFRP Distributed PSFCH Resource Patterns
  • the DFRP resource model set (Set) is composed of PSFCH resource models and is configured by RRC or pre-configured in the system.
  • the base resource is defined as the basic resource used for the PSFCH, which is used by the feedback UE to send its HARQ NAK.
  • PSFCH-based resources can be defined as frequency domain, time domain or code domain resources.
  • n bs 2 b
  • b is an integer
  • b ⁇ 1 the number of base resources in the PSFCH.
  • the PSFCH resource model and resource model set depend on the size of the ZB and base resources, and are composed of base resources.
  • Each PSFCH resource model that is combined has an independent index.
  • the SCI sent by the Tx UE contains the PSFCH resource model index and PSFCH transmission timing information.
  • the Rx UE uses the PSFCH resource model to feed back the SFCI to the Tx UE, and the Tx UE detects its SFCI signal to identify the HARQ information of the fed back UE and its Zone-ID.
  • the Tx UE gradually improves its AoD resolution through different PSFCH resource models received at different times.
  • DFRP requires N DFRP 's PSFCH resources (including time and frequency domain resources) as
  • DFRP is mainly designed for beamforming-based retransmission. It is for a single Rx UE or for multiple Rx UEs located in the same area. These Rx UEs incorrectly receive data packets from the PSSCH. However, through DFRP detection, if the Tx UE obtains the Zone-ID information of multiple Rx UEs located in different areas, the Tx UE will consider retransmitting data packets with omnidirectional antennas.
  • the four PSFCH resource models are respectively composed of two base resources, one in light gray and the other in gray.
  • Rx UEs located in the same area can share PSFCH resources.
  • the Tx UE associated with Zone-ID-10 sends SCI to other Rx UEs through PSCCH.
  • the PSFCH resource model feeds back the HARQ NAK to the Tx-UE.
  • the information contained in the SCI includes the transmission time difference between the PSCCH and the PSFCH, the PSFCH timing interval, and the PSFCH resource model index.
  • the reason for including the PSFCH resource model index is that the Tx UE can adaptively control retransmission at any PSFCH timing. These parameters can be (pre)configured according to the situation.
  • the Tx UE associated with Zone-ID-10 implicitly obtains the Zone-ID of the feedback UE associated with Zone-ID-0, so that the Tx UE adaptively performs beamforming based Retransmission.
  • Zone-ID-0 In PSFCH transmission opportunity-1 (Occasion-1), the Rx UE associated with Zone-ID-0 sends HARQ NAK on PSFCH (light gray resource) based on resource model-1 (Pattern-1). Then, the Tx UE associated with Zone-ID-10 detects the NAK signal and roughly obtains the location of the feedback UE.
  • the possible location is one of Zone-ID-0, 1, 4, 5, or Zone-ID-10.
  • the Tx UE should immediately perform retransmission with omnidirectional antennas.
  • Occasion-2 In PSFCH Transmission Occasion-2 (Occasion-2), the Rx UE associated with Zone-ID-0 sends HARQ NAK on PSFCH (still light gray resource) based on Resource Model-2 (Pattern-2). Then, the Tx UE associated with Zone-ID-10 detects the NAK signal and obtains the location of the feedback UE. The possible location is one of Zone-ID-0, 1, 4, and 5.
  • the Tx UE associated with Zone-ID-10 immediately performs retransmission, otherwise it waits for the next SFCI to make a decision. Obviously, the AoD resolution obtained by Tx UE is improved compared with Chance-1.
  • Zone-ID-0 In PSFCH Transmission Occasion-3 (Occasion-3), the Rx UE associated with Zone-ID-0 sends HARQ NAK on PSFCH (still light gray resource) based on Resource Model-3 (Pattern-3). Then, the Tx UE associated with Zone-ID-10 detects the NAK signal and obtains the location of the feedback UE. The possible location is one of Zone-ID-0, 1.
  • the Tx UE associated with Zone-ID-10 immediately performs retransmission, otherwise it waits for the next SFCI to make a decision. Obviously, the resolution of the Zone-ID obtained by the Tx UE associated with Zone-ID-10 has been further improved.
  • the Rx UE associated with Zone-ID-0 sends HARQ NAK on PSFCH (dark gray resource) based on resource model-4 (Pattern-4). Then, the Tx UE associated with Zone-ID-10 detects the NAK signal and obtains the location of the feedback UE associated with Zone-ID-0. This is the highest resolution of the AoD associated with Zone-ID-0 obtained by the Tx UE.
  • Figure 16 shows an example of HARQ process with adaptive retransmission control, a) initial transmission with omnidirectional antenna, b) beamforming-based retransmission with directional antenna.
  • time slot-1 the initial transmission of the Tx UE associated with Zone-ID-10 is completed, and the PSFCH resources of the UE from timing-1 (slot-2) and timing-2 (slot-4) through Rx
  • the model receives NAK feedback to obtain the rough Zone-ID of the Rx UE, and then determines whether the AoD resolution is sufficient.
  • the Tx UE uses beamforming to perform early retransmission in time slot-6, where the SCI sent on the PSCCH re-indicates the transmission time difference between the PSCCH and the PSFCH, the PSFCH timing interval, and the PSFCH resource model index.
  • the Rx UE associated with Zone-ID-0 detects SCI on the PSCCH, it knows that the information indicated by the previous SCI is covered by the current SCI. In addition, whether to perform early retransmission depends on the judgment of the Tx UE itself.
  • Fig. 17 is an example of a PSFCH model within the communication range of zone ZB, in which Tx UE associated with Zone-ID-4 transmits SCI through PSCCH, and Rx UE in nine areas around Tx UE receives SCI.
  • Type-1 (Type-1), where the three PSFCH resource models are composed of two base resources, one is light gray and the other is gray.
  • Rx UEs located in the same area can share PSFCH resources. If the Rx UE successfully detects the SCI but fails to decode the data packet, the Rx UE feeds back HARQ NAK to the Tx UE based on the type-1 PSFCH model resource, so there are three PSFCH opportunities to send feedback signals.
  • This type uses three PSFCH opportunities to gradually increase the AoD resolution, and finally can reach 45° AoD resolution; the first PSFCH timing gets 180° resolution, the second PSFCH timing gets 90° resolution, the third PSFCH The timing is 45° resolution.
  • Model 1 if the Tx UE detects the feedback signal on both base resources, beamforming-based retransmission cannot be achieved, so that only data packet retransmission with omnidirectional antennas can be implemented. pass.
  • the first is that the Rx UE receives the wrong data packet and is in the same Zone-ID-4 as the Tx UE. The Rx UE will use two PSFCH-based resources to send feedback signals at the same time. The second is that two or more Rx UEs receive erroneous data packets, but in the area opposite to the Tx UE, different Rx UEs will use two PSFCH-based resources to send feedback signals.
  • Type-2 by using two PSFCH resource models, HARQ feedback can be performed more efficiently.
  • the PSFCH resource model-1 in Type-2 and the PSFCH resource model-1 in Type-1 are the same, and are used to roughly distinguish AoD.
  • the Tx UE can identify whether it is an Rx UE in a single direction, so as to determine whether the beamforming mechanism needs to be used for retransmission.
  • Model-2 the model design uses a combination of two PFSCH base resources and generates four indexes to implicitly indicate four Zone-IDs, namely:
  • the first PFSCH base resource (light gray) is associated with Zone-ID-3 and Zone-ID-5. This means that if the Rx UE is located in any area, it only sends SFCI on the base resource.
  • the second PFSCH base resource (dark gray) is associated with Zone-ID-1 and Zone-ID-7.
  • Zone-ID-0 and Zone-ID-8 have no associated resources. This means that if the Rx UE is located in any area, it does not send any signals.
  • Rx UE fails to decode more than two packets, a kind of ambiguity will be generated in Model-2.
  • the Rx UE can send SFCI through two PSFCH base resources. Therefore, without improving the accuracy of AoD, the Tx UE only relies on the AoD obtained in Model-1 to perform beamforming-based retransmission.
  • Figure 18 is an example of a PSFCH model in the communication range of zone ZB (5 ⁇ 5 zone), in which Tx UE associated with Zone-ID-12 transmits SCI through PSCCH, and Tx UE in 25 areas around Tx UE Rx UE receives SCI.
  • Rx UE can have four PSFCH opportunities to trigger HARQ feedback, of which only model-4 uses a combination of two PFSCH base resources to generate three indexes to implicitly indicate Three Zone-IDs.
  • Zone-ID-0 and Zone-ID-6 only need to have the same index to indicate AoD, and the same is true for Zone-ID-16 and Zone-ID-20. This can gradually increase the resolution of AoD to 180°, 90°, 45° and 22.5°.
  • the Tx UE can control the resolution of AoD and adaptively perform retransmission based on early beamforming, similar to the example in FIG. 16.
  • the side chain retransmission can be implemented based on the beamforming mechanism, especially when it comes to millimeter waves (mmWave).
  • mmWave millimeter waves
  • Control channels such as PSCCH and PSFCH can be performed in a lower frequency band (band below 6 GHz) to ensure a larger side link coverage.
  • -Data channels such as PSSCH can be carried out in high frequency bands (such as millimeter waves) to ensure higher side chain transmission capacity.
  • control information is relatively small, so it can be realized with a limited low frequency band, while the data information is much larger, so it can be realized with a high frequency band.
  • the former may not necessarily involve beamforming mechanisms, while the latter must involve beamforming mechanisms.
  • the UE location depends on the positioning area mechanism, but it can also be implemented based on location coordinates. Since the location of Tx UE is known in multicast, Rx UE calculates the AoA (Angle of Arrival) between Tx UE and Rx UE according to their relative position coordinates, so Rx UE selects the PSFCH resource centered on Tx UE Perform HARQ feedback. It is worth noting that AoA is quantized by limited bits, and based on (pre)configuration, independent PSFCH resources are allocated to each quantized AoA. Therefore, the PSFCH resource set associated with each multicast transmission is only related to Tx UE and quantized AoA. Once the Tx UE receives the corresponding PSFCH, it can implicitly calculate the AoD (Angle of Departure) and implement beamforming-based retransmission.
  • AoA Angle of Arrival
  • Retransmission based on beamforming can be performed by cooperative R-UEs of the same group (Groupcast Member), especially in the case of millimeter wave deployment.

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Abstract

一种侧链路重传方法，包括：至少有一个发送设备Tx UE，每个Tx UE向组播中的接收设备Rx UE发送第一数据包；当一些Rx UE接受链路上的第一数据包失败时，其它Rx UE成功检测到第一数据包，并对第一数据包进行再编码，生成第二数据包，然后将第二数据包在与Tx UE初始使用的相同资源中同时转发/重传给第一数据包检测失败、和/或在半双工状态下工作的其它UE。多个R-UE使用相同信道将相同数据包协作地转发到Rx UE，以增强侧链路覆盖。为了有效地实现协作中继，PSFCH的资源池的(预)配置和物理侧链路控制信道PSCCH资源被重新设计。这种新机制也可以应用于基于波束成形的重传。

Description

一种侧链路重传方法
本申请请求_____年____月____日申请的申请号为_________(发明名称：________)的中国专利申请的优先权。
技术领域
本发明涉及一种通信方法，尤其涉及一种车联网(V2X)通信中的可有效地实现协作中继的侧链路重传方法。
背景技术
车联网通信(V2X，Vehicle-to-Everything Communication)是未来智能交通运输系统的关键技术。它通过装载在车辆上的传感器、车载终端及电子标签提供车辆信息，采用各种通信技术实现车与车通信(V2V，Vehicle-to-Vehicle Communication)、车与人通信(V2P，Vehicle-to-Pedestrian Communication)以及车与网络通信(V2N，Vehicle-to-Network Communication)，从而可以获得实时路况、道路信息、行人信息等一系列交通信息，进而提高驾驶安全性，减少拥堵，提高交通效率等。在第三代合作伙伴计划(3GPP)release-15标准发布之后，NR(New Radio)V2X成为了重要的通信技术和研究课题。NR V2X系统将具有灵活的设计，支持低延迟和高可靠性的服务。另外，NR V2X系统还将具有更高的系统容量和更好的覆盖范围。
在NR-V2X中，为了实现诸如数据包接收比(Packet Reception Ratio，PRR)的超高要求，NR-V2X支持基于混合自动重传请求(Hybrid Automatic Repeat reQuest，HARQ)的重传。HARQ是依赖于物理层侧链反馈信道(Physical Sidelink Feedback Channel，PSFCH)，而HARQ反馈过程可以基于选项-1(Option-1)或选项-2(Option-2)机制。选项-1(Option-1)：如果在解码相关联的PSCCH之后Rx UE未能解码相应的TB(Transport Block)，则Rx UE在PSFCH上发送HARQ-NAK。否则它在PSFCH上不发送任何信号。选项-2(Option 2)：如果Rx UE成功解码相应的TB，则在PSFCH上发送HARQ-ACK。如果在解码相关联的PSCCH之后Rx UE未能解码相应的TB，则Rx UE在PSFCH上发送HARQ-NAK。
在设备到设备(Device-to-Device，D2D)中，引入了Layer-3中继来增强侧链路通信和侧链路发现机制的功能对实际的无线标准规范影响很小。中继的D2D链路依赖于侧链路通信机制，而中继设备到网络通信依赖于正常的LTE蜂窝机制。Layer-3中继功能对无线标准规范的唯一影响是在RRC功能。然而，为了提高NR V2X的可靠性，Layer-1和Layer-2中继功能是必要的。
在3GPP标准中，设备到设备之间的直接通信链路称为侧链路(或旁路)(Sidelink)，和上行链路、下行链路类似，侧链路上也存在控制信道和数据信道，前者称为物理侧链路控制信道(Physical Sidelink Control Channel，PSCCH)，后者称为物理侧链路共享信道 (Physical Sidelink Shared Channel，PSSCH)。PSCCH用于指示PSSCH传输的时频域资源位置、调制编码方式和PSSCH中承载的数据的优先级等，PSSCH用于承载数据。
资源分配可以简单地依赖于集中式机制；如果在覆盖范围内，则通过gNB完成，或者如果在覆盖范围之外，则通过中继节点完成。在LTE-V2X中，这种集中式机制是通过模式-3(Mode-3)方式来执行资源选择的；这种方式由于确保Tx UE(Transmitter UE)之间没有资源冲突从而提高了可靠性，但是导致比较大的迟延。
在LTE-V2X标准的5.10.13.2章节中，一个新的机制应用于V2X侧链路(Sidelink)资源池的选择，该机制与区域标识(例如区域ID，Zone-ID)有关。其中，独立的资源或资源池和地理坐标相关连，被V2X侧链路(Sidelink)通讯上层(予)配置。Tx UE(Transmitter UE)依赖于区域ID，只访问与Tx UE地理坐标相关的资源池，Tx UE利用其最后的地理坐标来实施资源池的选择。通过如下公式，Tx UE决定了Zone-ID：
Zone-ID＝y 1N x+x 1，
Figure PCTCN2019105865-appb-000001
其中，L为区域长度值，W为区域宽度值，N x为Zone-ID的经度，N y为Zone-ID纬度值，x和y分别为UE当前位置经度、纬度与参考坐标(0,0)之间的距离，x 1＝0,1,…,N x-1；y 1＝0,1,…,N y-1。
其中，L,W,N x和N y信息可以通过上层RRC来配置，或通过予配置方式来实现。在以下阐述中，(予)配置表示配置或予配置。
基于LTE-V2X标准说明，参数L、W、N x、N y或在Type-21或在Type-26系统信息块(System Information Block，SIB)中由RRC(Radio Resource Control，无线资源控制)配置，或者在SL-V2X-Preconfiguration系统中预配置。因此，需要N b个比特来标明构成区域块(ZB，Zone Block)的N x·N y个Zone-ID，其中：
Figure PCTCN2019105865-appb-000002
Figure PCTCN2019105865-appb-000003
为上限函数(Ceiling Function)。
在LTE-V2X中，通信数据包相对简单，只考虑周期数据包到达和发送，数据包大小也恒定。相反，在NR-V2X中，存在三种通信传输(Cast)类型：广播(Broadcast)、单播(Unicast)和组播(Groupcast)，数据包的到达可以是周期的也可以是非周期的，数据包大小可以是恒定也可以是不恒定的。在组播(Groupcast)中，Tx UE通过Zone-ID或地理坐标发送并交换位置信息。Tx UE通过PSCCH信道发送SCI(Sidelink Control Indication)，相关组内的接收用户(Rx UE，Receive UE)检测SCI获取Tx UE的Zone-ID或地理坐标，并获取与Tx UE的距离。通过和距离相关的混合自动重传请求(Hybrid Automatic Repeat reQuest，HARQ)反馈过程确保通信范围内的PRR性能。
应该指明的，当用户(UE)在发送数据包时候，UE被定义为Tx UE，而在接受数据包时候，被定义为Rx UE。因此同样的用户在某时隙(Time slot)是Tx UE，而在某时隙是Rx UE。
中继功能可以通过中继节点或基站，或者放置在地面上的路侧单元(Road Side Unit，RSU)，或移动集群簇头(Mobile Cluster Header)，或更一般地车辆UE来实现。由于中继 节点拥有高天线增益和大传输功率，其覆盖范围可以大很多。然而，在覆盖范围之外，仅移动集群簇头或车辆UE能够负责实现中继功能。为了增强中继覆盖，简单的方法是多次重复传输，但是这种方法会增加信道资源代价。
在一种侧链路通信的场景中，Tx UE将数据包发送给其他Rx UE，其中一些Rx UE成功检测到数据包，而一些Rx UE未能检测到数据包。有两个原因导致Rx UE接收失败：一种是由于Rx UE接受信号微弱或经历强干扰导而致检测失败，另一种是由于Rx UE仅安装半双工系统。半双工系统意味着，一旦UE处于传送模式，则不能够接收，反之亦然。从而降低了数据包的接收速率。
如何在提高信道效率的同时，有效地实现车辆UE的协作中继功能，从而提高车联网通信的高可靠性，是本领域技术人员需要解决的问题。
发明内容
本发明的目的在于提供一种侧链路重传方法，以解决上述技术背景中提出的问题。
本申请中的资源可以是物理侧链路控制信道PSSCH,物理侧链路共享信道PSCCH，也可以是物理层侧链反馈信道PSFCH(Physical Sidelink Feedback Channel)。
为实现上述目的，本发明采用以下技术方案：
本发明所提供的侧链路重传方法，优选地，应用于处于车联网架构中实现中继功能的多个用户设备UE，即多UE协作中继(Multi-UE Cooperative Relay)重传方法。
在组播侧链路通信中，Tx UE将数据包发送给组内其他Rx UE；其中一些Rx UE成功检测到数据包，而一些Rx UE未能检测到数据包；多UE协作中继主要是由成功检测到数据包的Rx UE作为R-UE(Relay UE)来完成重传，也就是说，这些R-UE复制并发送同样的数据包给未能检测到数据包的Rx UE。
在一种优选实施例中，本发明所提供侧链路重传方法，包括：
在组播中至少有一个发送设备Tx UE，每个Tx UE向接收设备Rx UE发送第一数据包；当一些Rx UE接收到链路上的第一数据包失败时，其它Rx UE成功检测到第一数据包，并对第一数据包进行再编码，生成第二数据包(一般第一数据包和第二数据包是完全相同的，除非在第一数据包的信令中具体隐式或明式地指示)，然后将第二数据包在与Tx UE初始使用的相同资源中(或不同资源)同时转发/重传给第一数据包检测失败、和/或在半双工状态下工作的其它UE。
如果使用相同资源，就不需要在第一数据包中使用信令来指示使用的资源；但是，如果使用不同的单个资源或有限的多个资源，就必须通过第一数据包中的信令来具体指示。
优选地，发送设备Tx UE与接收设备Rx UE建立组播通信，所述多UE协作中继重传方法包括：
——至少一个发送设备Tx UE在第一时隙发送第一数据包，至少一个接收设备Rx UE成功检测由数据信道(例如，PSCCH和PSSCH)发送的第一数据包，至少一个接收设备Rx UE未能检测到所述第一数据包；
——未能检测到所述第一数据包的接收设备Rx UE在物理层侧链反馈信道PSFCH上发送侧链反馈控制信息SFCI(Sidelink Feedback Control Information)(例如：依赖于选项-1 (Option-1)或选项-2(Option-2)的HARQ反馈机制)，组播通信中的其它UE对其进行接收；其中，所述侧链反馈控制信息用于指示是否检测到所述第一数据包；
——成功检测所述第一数据包的接收设备Rx UE作为R-UE，根据被解码的SCI信息，单独对所述第一数据包进行再编码，生成第二数据包，然后将第二数据包在第二时隙转发给其它UE；初始发送第一数据包的发送设备Tx UE(如果由两个以上的Tx UE在同时发送第一数据包)检测到所述第二数据包，解决了半双工问题，同时，未能检测到所述第一数据包的接收设备Rx UE接收到所述第二数据包，将所述第二数据包与先前软储存的第一数据包进行HARQ软合并，然后对其进行解码，从而实现了由多UE协作中继的重传过程；
其中，所述第二时隙为第一时隙之后的一个时隙。
更优选地，所述发送设备Tx UE通过物理侧链路控制信道PSCCH发送SCI，Tx UE用显式机制(Explicit)或隐式机制(Implicit)通知用于HARQ反馈的PSFCH资源索引和用于重传的PSCCH+PSSCH资源索引给Rx UE；其中，显式机制是使用SCI来通知相关资源，而隐式机制是将初始传输的PSSCH资源索引，与用于HARQ反馈的资源索引和重传资源索引相耦合。
进一步地，资源的耦合可以在时域或频域中执行；如果耦合在时域中执行，则频域中的资源必须由SCI指示；如果耦合在频域中执行，则时域中的资源必须由SCI指示；资源的耦合也可以在时域和频域中同时进行。
进一步地，如果未能检测到所述第一数据包的接收设备Rx UE反馈HARQ NAK，并且被组播通信中的其它UE接收到，这就意味着由SCI指示的PSCCH+PSSCH的资源将被多UE协作中继使用；如果未能检测到所述第一数据包的接收设备Rx UE没有反馈HARQ NAK，则在第一数据包中由SCI指示的PSCCH+PSSCH的资源索引可以被其它Tx UE使用，即被SCI预留的资源将自动释放。
更进一步地，成功检测所述第一数据包的接收设备Rx UE收到HARQ NAK和/或知道发生Tx UE半双工时，作为R-UE进行基于协作中继的重传。
应该指明的，当用户设备UE在发送数据包时候，UE被定义为Tx UE，而在接受数据包时候，被定义为Rx UE。因此，同样的用户设备UE在某时隙(Time slot)是Tx UE，而在某时隙是Rx UE。
优选地，所述第一数据包传输失败的原因，包括：Rx UE接受信号微弱或经历强干扰导而致检测失败；或者，Rx UE仅安装半双工系统。
优选地，多UE协作中继通过Layer-1中继(Layer-1Relay)或Layer-2中继(Layer-2Relay)来实现；
所述Layer-1中继，在中继过程中仅涉及物理层；其中，仅在成功解码第一数据包时，多个(至少两个)Rx UE(R-UE)和Tx UE一样，对接收的第一数据包进行再编码，在预定时隙或由Tx UE初始发送的SCI指示时隙中，R-UE在与Tx UE初始使用的相同资源上转发重新编码后的第二数据包；也就是说，R-UE必须使用相同的物理侧链路控制信道PSCCH和与其相关的物理侧链路共享信道PSSCH，在这种情况下，R-UE将不涉及到MAC的调度和HARQ过程，但是可以实施PSCCH和PSSCH上的软合并(Soft-Combining，例如，Chase Combining)；
所述Layer-2中继，在中继过程涉及物理层和MAC层；在物理层中，仅在成功解码第一数据包时，R-UE和Tx UE一样，对接收的数据包进行再编码；在MAC层中，R-UE接收至少一个HARQ否定确认(Negative-acknowledgement，NAK)，R-UE在与Tx UE初始使用的相同资源上转发重新编码的第二数据包；在这种情况下，R-UE仅仅涉及简单调度(不重新调度资源)，一般不用需要考虑信道条件、数据缓冲状态、优先级控制，调度器只需要简单判断是否应该进行合作重传。
更优选地，所述多UE协作中继主要通过Layer-2中继来实现。
优选地，所述UE包括主R-UE(Primary R-UE)和/或辅R-UE(Secondary R-UE)，其中，
所述主R-UE，由网络或组成员指定，主R-UE可以是单个R-UE或多个R-UE，其必须参与多UE协作中继，除非它没有正确地接收到Tx UE发送的第一数据包；
所述辅R-UE，自愿参与多UE协作中继，在大多数情况下，辅R-UE能够从邻近的Tx UE接收数据包，然后转发给邻近的Rx UE。
更优选地，所述UE采用辅R-UE。
优选地，所述资源包括主中继资源(Primary Relay Resources)和辅中继资源(Secondary Relay Resources)，其中，
所述主中继资源，由SCI在第一数据包的物理侧链路控制信道PSCCH上指示，并与第一数据包相耦合；在多数情况下，它与Tx UE传输第一数据包的资源相同；所有的R-UE使用相同的主中继资源完成多UE协作中继。
所述辅中继资源，由SCI在第二数据包的物理侧链路控制信道PSCCH上指示；即，R-UE可以自主地选择用于转发第二数据包的资源，并且不同的R-UE可以使用不同的资源。
更优选地，所述资源采用主中继资源。
优选地，成功检测到两个以上的第一数据包的Rx UE可以对两个以上的第一数据包进行XoR(eXclusive OR)编码，从而提高侧链路传输效率。
在一种优选实施例中，本发明所提供的侧链路重传方法，优选地，应用于处于车联网架构中基于位置区域实现中继功能的多个用户设备UE，即位置区域辅助中继重传方法。尤其是优选为RCR(无线电通信范围)不超过QCR(QoS通信范围)情况下的位置区域辅助中继重传方法。
本发明所提供的侧链路重传方法，其中，划分出N个区域，N为自然数；第n区域内的区域ID为Zone-ID-n，n为选自0至N-1的自然数；Zone-ID-n区域被I n个UE占用(I n是Zone-ID-n区域内UE数量)；UE之间的无线电通信范围RCR(Radio Communication Range)是无线电通信能达到的范围，至少从一个区域的边缘到其相邻区域的边缘的距离，而UE之间的服务质量通讯范围QCR(QoS Communication Range)是传输的数据包需要到达的范围，可以从一个区域的边缘到其下一个邻居区域边缘的距离；
Zone-ID-(n-1)、Zone-ID-n和Zone-ID-(n+1)为依次相邻设置的区域，RCR是包括Zone-ID-(n-1)和Zone-ID-n的区域，或者是包括Zone-ID-n和Zone-ID-(n+1)的区域，QCR是跨越越Zone-ID-(n-1)，Zone-ID-n和Zone-ID-(n+1)的区域，当然可以更远；这样每个区域的大小可以根据RCR范围来决定，从而保证相同区域内的UE可以相互成功通信；区域 的距离可以说实际距离，也可以是RSRP的无线电距离；
所述方法包括：
与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的发送设备Tx UE发送初始数据包，以及与Zone-ID-(n-1)，Zone-ID-n，Zone-ID-(n+1)相关联的接收设备Rx UE接收初始数据包；
在Tx UE相同区域的全部Rx UE可以成功检测到初始数据包；与Zone-ID-(n-1)和Zone-ID-(n+1)同时相邻的Zone-ID-n相关联的区域中的部分或全部Rx UE可以成功检测到初始数据包；与Zone-ID-(n-1)间隔相邻的Zone-ID-(n+1)相关联的区域中的Rx UE，或者与Zone-ID-(n+1)间隔相邻的Zone-ID-(n-1)相关联的区域中的Rx UE，至少有部分未能检测到初始数据包；
Zone-ID-n中成功检测到初始数据包的Rx UE按照对初始数据包进行XoR编码，然后将重新编码的XoR编码数据包在与Tx UE初始使用的相同资源中(单个资源或有限的多个资源)同时转发/重传给初始数据包检测失败、和/或在半双工状态下工作的其它UE。
优选地，初始数据包传输可以在时隙t中由位于拥有以下Zone-ID(类型-1区域)中的Tx UE执行，
Zone-ID＝y 1N x+x 1,如果(x 1mod2)＝(y 1mod2)；
并且可以通过位于拥有以下Zone-ID(类型-2区域)中的Rx UE在时隙t+Δ中执行基于中继的重传
Zone-ID＝y 1N x+x 1,如果(x 1mod2)≠(y 1mod2)；
其中，Δ是以时隙为单位的HARQ处理时间(Δ≥1)；N x为Zone-ID的经度，N y为Zone-ID纬度值，x和y分别为UE当前位置经度、纬度与参考坐标(0,0)之间的距离，x 1＝0,1,…,N x-1；y 1＝0,1,…,N y-1。
优选地，与Zone-ID-(n-1)相关联的Tx UE-i n-1发送第一初始数据包
Figure PCTCN2019105865-appb-000004
第一数据包将被其自己区域中的所有Rx UE成功接收，同时，该第一初始数据包也被与Zone-ID-n相关联的Rx UE成功接收，但是，该第一初始数据包无法被与Zone-ID-(n+1)相关联的Rx UE接收；
与Zone-ID-(n+1)相关联的Tx UE-i n+1发送第二初始数据包
Figure PCTCN2019105865-appb-000005
第二初始数据包将被其自己区域中的所有Rx UE成功接收，同时，该第二初始数据包也被与Zone-ID-n相关联的Rx UE成功接收，但是，该第二初始数据包无法被与Zone-ID-(n-1)相关联的Rx UE接收；
R-UE-i n将XoR编码的数据包
Figure PCTCN2019105865-appb-000006
转发给与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的两个邻居区域中的Rx UE；
其中，在检测过程中，与Zone-ID-(n-1)相关联的所有Rx UE是预先知道第一初始数据包
Figure PCTCN2019105865-appb-000007
并且通过对
Figure PCTCN2019105865-appb-000008
的XoR解码来检测到
Figure PCTCN2019105865-appb-000009
与Zone-ID-(n+1)相关联的所有Rx UE是预先知道第二初始数据包
Figure PCTCN2019105865-appb-000010
并且通过对
Figure PCTCN2019105865-appb-000011
的XoR解码来检测到
Figure PCTCN2019105865-appb-000012
优选地，Zone-ID-(n-1)和Zone-ID-(n+1)相关联的接收设备Rx UE按照预设策略在物理层侧链反馈信道PSFCH上，对组播中的其它UE发送包含HARQ-NAK或HARQ-ACK的 侧链反馈控制信息SFCI(Sidelink Feedback Control Information)，HARQ-NAK触发Zone-ID-n中成功检测到初始数据包的Rx UE进行逐个重传；其中，所述预设策略包括以下任意一种方式：
方案-1：如果初始数据包解码失败，则未能检测到初始数据包的接收设备Rx UE反馈HARQ-NAK，PSFCH资源仅与初始数据包耦合；
方案-2：如果初始数据包解码失败，则未能检测到初始数据包的接收设备Rx UE反馈HARQ-NAK，PSFCH资源与初始数据包和反馈HARQ-NAK的接收设备Rx UE的Zone-ID耦合；
方案-3：接收设备Rx UE反馈HARQ-NAK或HARQ-ACK，PSFCH资源与初始数据包和反馈HARQ-NAK或HARQ-ACK的接收设备Rx UE的Zone-ID耦合。
优选地，所述资源包括：用于初始数据包传输的数据包资源(Data Packet Resource，DPR)和用于协作中继传输的协作中继资源(Cooperative Relay Resource，CRR)。
在一种优选实施例中，DPR和CRR被时分多路处理(Time Division Multiplexing，TDM)，以避免半双工问题；
DPR和CRR都与Zone-ID相关联，在频域中使用相同数量的资源，用L ZONE个子信道表示(Sub-channel，SCH，每个包含L ZONE Resource Blocks,RBs)，在时域中拥有相同或不同的资源长度，即DPR可以跨越L DPR时隙，CRR可以跨越L CRR时隙；L ZONE个SCH和L DPR时隙形成DPR的SCB块(SCH Block，SCB)，而L ZONE个SCH和L CRR时隙形成CRR的SCB块；在DPR中，作为SCH的最小传输单元的资源表示为DPR n,t(p)，在CRR中，最小传输单元的资源表示为CRR n,t(p)；其中，n是Zone-ID，t是时域中的时隙索引，p是频域中SCH的索引，L ZONE、L SCH、L DPR和L CRR参数是由RRC(Radio Resource Control，无线资源控制)配置或在系统中被预先配置。
更优选地，在DPR和CRR之间预留HARQ反馈过程使用的频域和/或时隙资源。
更优选地，所述资源按照预设规则进行选择，将用于DPR的资源和用于CRR的资源相耦合，使得协作中继中涉及的所有接收设备Tx UE可以隐式地选择相同的资源而无需任何附加的控制信息；所述预设规则包括以下方式：
规则-1(SCB关系)：在频域中，与协作中继中涉及的Zone-ID-n相关联的CRR的SCB中的重传资源应该对应于与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的DPR的SCB中的初始传输资源；在时域中，DPR的SCB和CRR的SCB彼此相邻；
规则-2(XoR编码数据包顺序)：每个Zone-ID-n中成功检测到初始数据包的Rx UE按照预设规则对XoR编码数据包进行顺序编号，根据编号的顺序依次将XoR编码数据包进行发送；
规则-3(CRR资源顺序)：在每个SCB资源池的配置或预配置中，按照预设规则对CRR资源进行顺序编号，例如，资源顺序先从时隙索引的方向预先确定，然后从SCH索引方向确定，这样可以形成二维SCB资源；
规则-4(资源选择)：每个Zone-ID-n中成功检测到初始数据包的Rx UE选择在其自己的SCB中配置或予配置的CRR资源，XoR编码数据包的顺序和CRR资源的顺序一对一映射。
优选地，Tx UE通过PSCCH发送SCI及相关联的PSSCH，而Rx UE接收SCI，并且获取QCR信息；仅在QCR范围内，Tx UE根据PSSCH解码状态然后判断是否反馈ACK或NAK。
更优选地，QCR信息可以依赖于显式方式或隐式方式由SCI指示；其中，
显式方式是，SCI携带特定专用比特(比如，3比特)，直接向Rx UE指示QCR；
隐式方式是，SCI不携带任何附加比特，而是重用现有的初始数据包优先级信息(例如，Priority Information，3比特)来间接指示QCR。
优选地，协作中继中涉及的UE数量可以根据SCI指示的QCR信息，和/或初始数据包优先级信息，和/或收发端Zone-ID关系，由候选R-UE判断自己是否应该参与协作中继，即R-UE数量并不是系统统一决定，可以自适应地依赖于每个初始数据包的QoS等要求。
优选地，初始数据包的优先级或QCR的大小，与参与协作中继的R-UE的数量成正比。
优选地，所述XoR编码(XoR-coding，包括编码和解码)包括：类型-1XoR编码(Type-1XoR-coding)或类型-2XoR编码(Type-2XoR-coding)；其中，
在类型-1XoR编码中，MAC层向物理层提供两个以上的传输块TB(Transport Block)，由Tx UE通过无线传输链路发送给Rx UE，同时，MAC层中的调度器会通知物理层，在信道编码之后，哪些TB应该彼此进行XoR编码；Tx UE将XoR编码后的TB发送到Rx UE，并且Rx UE在信道解码之前对接收的TB执行XoR解码；
在类型-2XoR编码中，MAC层准备并生成XoR编码的TB，然后被提供给物理层，即物理层不需要知道XoR编码的信息，不需要改变物理层结构。
优选地，UE之间的侧链路上包括两种链路控制信息：一种是通过物理侧链路控制信道(Physical Sidelink Control Channel，PSCCH)传送的侧链路控制信息(Sidelink Control Information，SCI)，另一种是通过物理侧链路反馈信道(Physical Sidelink Feedback Channel，PSFCH)传送的侧链路反馈控制信息(Sidelink Feedback Control Information，SFCI)。
更优选地，用于PSFCH的资源池可以是：
与公共资源池相关，与UE在地理位置无关，任何UE都可以使用该公共资源池；或者，
与基于Zone-ID的资源池相关，该资源池只能被位于同一区域中的UE使用。
在一种优选实施例中，公共PSFCH资源池是(预)配置的，其中任何UE都能够选择PSFCH资源用于HARQ反馈；作为PSFCH的资源可以与PSCCH/PSSCH的资源相耦合，而耦合的信息可以由PSCCH发送的SCI来指示，或者由(预)配置来相互映射。
在一种优选实施例中，一旦需要通过PSSCH来传输数据包，就必须用PSCCH来传送相关的SCI，并同时指示PSFCH的资源；其中，PSCCH与其相关的PSFCH之间存在一时间间隔。
在一种优选实施例中，Tx UE通过PSCCH传输SCI信息，通过PSSCH传输相关传输块(Transport Block，TB)，而SCI包含公共PSFCH资源索引信息；Rx UE接收SCI及其相关数据包，并检测是否有错误；仅在Rx UE检测到所接收的数据包有错误时，侧链路HARQ反馈被触发；依赖于HARQ选项-1的情况下，所有Rx UE使用相同的PSFCH资源来反馈HARQ的NAK。
在一种优选实施例中，基于区域的PSFCH资源池的(预)配置和针对PSFCH资源的SCI的指示可以是：
――(预)配置：每个与Zone-ID-n相关联的PSFCH资源池中的M资源可以用索引m来指示；
――SCI中的指示比特：
Figure PCTCN2019105865-appb-000013
比特表示所选的索引m。
在一种优选实施例中，每个与Zone-ID-n相关联的PSFCH资源池中的M资源公式为
Figure PCTCN2019105865-appb-000014
其中，m＝1,2,…,M，n＝0,1,…,N-1，N是ZB中的区域数。
在一种优选实施例中，第一个PSFCH资源被分配到Tx UE所在的中心区域，第二个PSFCH资源被分配到Tx UE为中心的第一层区域，以此类推，第k个PSFCH资源被分配到Tx UE为中心的第(k-1)层区域，直到QCR内的最后一个区域层为止，k为1至总层数之间的自然数。
优选地，每个区域层中的PSFCH资源数量应该被单独(预)配置，其规则为M 0≤M 1≤…≤M K-1，其中K是QCR内的区域层数，也是(预)配置的。
优选地，PSFCH资源可以由索引m统一指示，其中，m k＝m mod M k，m＝1,2,…,M K-1；m k＝1,2,…,M k。
在一种优选实施例中，每个Rx UE从其中一个中心Tx UE检测到PSCCH上的SCI，然后基于该中心Tx UE的Zone-ID和Rx UE的Zone-ID确定Rx UE位于其中的哪个区域层。更优选地，根据HARQ反馈机制，其中部分Rx UE(反馈Rx UE)将分别独立地通过与其他区域层相关联的PSFCH各自发送相应的SFCI(NAK)给该中心Tx UE，与此同时，SFCI也被其他UE接收，其他UE从反馈Rx UE检测到SFCI，并协同参与针对反馈Rx UE的重传。
在一种优选实施例中，通过位置坐标由Rx UE获取Tx UE的区域位置，因此Rx UE能够计算出Tx UE和Rx UE之间的距离，从而推导出Rx UE属于哪个区域层。更优选地，Zone-ID不需要被配置。其中Tx UE需要对其位置坐标进行组播，而Rx UE只需要知道自身坐标。对于用于HARQ反馈的PSFCH资源分配，可以保持相同的基于区域层的(预)配置方法。
在一种优选实施例中，每个Tx UE通过RRC参数在数据信道(如，PSSCH信道)上发送位置信息，并且每个Rx UE通过该RRC参数更新位置表中的位置信息。因此，位置表(RRC参数)应该包括Tx UE位置信息和该Tx UE的相关ID；UE可以通过接收由SCI指示的Tx UE ID，然后在RRC位置表中查找Tx UE ID，然后隐式地获取相应的Tx UE的位置；因此，Tx UE仅需要通过SCI发送其UE ID，而不需要SCI直接传送位置信息。
在一种优选实施例中，通过基于Zone-ID的与PSCCH相关联的PSFCH资源池信息，或者由PSCCH激活的PSFCH资源信息，Tx UE可以隐式地获取与HARQ反馈UE相关联的位置区域，从而推导出相关的Tx UE的AoD(发射角(Angle of Departure，AoD)。
更优选地，位于Zone-ID-n的Tx UE通过PSCCH及其关联的PSSCH执行初始数据包传输，而位于其他区域的Rx UE进行相应的接收；解码错误的Rx UE通过被激活的PSFCH发送相应的SFCI(NAK)给Tx UE；Tx UE通过检测PSFCH上的SFCI获取解码错误的Rx UE的位置Zone-ID，并推导出AoD；Tx UE根据推导出的AoD将数据包用波束 成形(Beamforming)重新发送到解码错误的Rx UE。
更优选地，Tx UE发送的SCI其中包含PSFCH资源模型索引以及PSFCH的传输时机信息。Rx UE使用PSFCH资源模型反馈SFCI给Tx UE，Tx UE对其SFCI信号检测从而识别反馈UE的HARQ信息和其Zone-ID。
更优选地，SCI包含的信息有，PSCCH和PSFCH之间发送时间差，PSFCH时机间隔，PSFCH资源模型索引。
更优选地，Tx UE通过在不同传输时机接收到的不同PSFCH资源模型逐步提高其AoD分辨率。
更优选地，Tx UE后续传输时机中用波束成形进行早期重传，其中PSCCH上发送的SCI重新指示了PSCCH和PSFCH之间发送时间差，PSFCH时机间隔，PSFCH资源模型索引；一旦与Zone-ID-x相关联的Rx UE在PSCCH上检测到SCI，它就得知先前SCI指示的信息被当前SCI覆盖。
更优选地，与Zone-ID-n相关联的Tx UE隐式地获取与Zone-ID-x相关联的反馈UE的Zone-ID，x为0至N-1范围的自然数，由此Tx UE自适应地执行基于波束成形的重传。
在一种优选实施例中，根据不同情况PSFCH资源模型被任意(预)配置，但每个PSFCH资源模型分别由至少两个基资源组成，位于相同区域中的Rx UE可以共享PSFCH资源。如果Rx UE成功检测到SCI，但没有成功解码数据包的话，则Rx UE可以用不同PSFCH时机反馈HARQ NAK给Tx UE，通过不同的PSFCH时机逐渐提高AoD分辨率。
在一种优选实施例中，存在至少两个以上的PSFCH资源模型，通过检测第一PSFCH资源模型中的SFCI，Tx UE能够初步区分AoD，识别是否是单个方向上的Rx UE需要重传，从而判断是否需要使用波束成形机制的重传；通过检测第二以上的PSFCH资源模型逐渐提高AoD分辨率。
在一种优选实施例中，基资源(Base Resource)被定义为用于PSFCH的基础资源，被反馈UE使用发送其HARQ NAK。PSFCH基资源可以被定义为频域，时域或码域资源。PSFCH中的基资源的数量为n bs，其中，n bs＝2 b，b是整数，b≥1。PSFCH资源模型和资源模型集依赖于ZB大小以及基资源，并由基资源组合而成。被组合成的每个PSFCH资源模型拥有独立的索引。PSFCH资源模型由RRC配置或予配置。Tx UE发送的SCI其中包含PSFCH资源模型索引以及PSFCH的传输时机信息。Rx UE使用PSFCH资源模型反馈SFCI给Tx UE，Tx UE对其SFCI信号检测从而识别反馈UE的HARQ信息和其Zone-ID。Tx UE通过在不同时机接收到的不同PSFCH资源模型逐步提高其AoD分辨率。
更优选地，也可以基于位置坐标来实现。由于在组播中Tx UE位置是可知的，Rx UE根据他们的相对位置坐标计算出Tx UE和Rx UE之间的AoA(Angle of Arrival)，由此Rx UE选择以Tx UE为中心的PSFCH资源进行HARQ反馈。值得注意的是，AoA被有限比特量化，并且基于(预)配置方式，独立的PSFCH资源被分配给每个量化的AoA。因此，与每个组播传输相关联的PSFCH资源集仅与Tx UE和量化的AoA相关。一旦Tx UE接收到相应的PSFCH，它就可以隐式地计算出AoD(Angle of Departure)并实现基于波束成形的重传。
与现有技术相比，本发明的技术方案具有以下有益效果：
本发明提出了基于位置区域的协作中继，其中多个Tx UE使用相同信道将相同数据包协作地转发到Rx UE，以增强侧链路覆盖。为了有效地实现协作中继，PSFCH的资源池的(预)配置和物理侧链路控制信道PSCCH资源被重新设计。这种新机制也可以应用于基于波束成形的重传。
附图说明
构成本申请的一部分附图用来提供对本申请的进一步理解，本申请的示意性实施例及其说明用于解释本申请，并不构成对本申请的不当限定。在附图中：
图1是实施例一的五个UE进行基于多UE协作中继侧链路组播示意图；
图2是实施例一的多UE协作中继的过程转换图表；
图3是实施例二的五个UE使用两个独立子信道进行基于多UE协作中继的示意图；
图4是实施例三显示的区域覆盖和无线电功率强度之间的关系示意图；
图5是实施例四的基于区域的协作中继侧链路组播示意图，其中，Zone-ID-(n-1)和Zone-ID-(n+1)相关联的Tx UE发送数据包，Zone-ID-n相关联的Rx UE接收数据包；
图6是实施例四的基于区域的协作中继侧链路组播示意图，其中，Zone-ID-n相关联的R-UE作为中继发送数据包，Zone-ID-(n-1)和Zone-ID-(n+1)相关联的Rx UE接收数据包；
图7是实施例五的协作中继中数据信道资源的(预)配置示意图；
图8是实施例五的协作中继与资源选择示意图；
图9是实施例六的用于PSFCH的资源池(预)配置和基于PSCCH的PSFCH资源指示方法，其中，(a)为公共PSFCH资源池，(b)为基于Zone-ID的PSFCH资源池，且二者均限于单个ZB中；
图10是实施例六的耦合PSFCH资源的PSCCH和PSSCH传输示意图；
图11是实施例六的基于区域的多UE协作中继的示意图，其中，(a)为初始数据包发送和接收，(b)为基于区域的PSFCH资源的HARQ NAK反馈，(c)为基于位置的多UE协作中继重传；
图12是实施例七的基于区域的多UE协作中继的示意图，其中，(a)为初始数据包发送和接收，(b)为基于区域层的PSFCH资源的HARQ NAK反馈，(c)为基于位置的多UE协作中继重传；
图13是实施例七的基于区域的多UE协作中继的简化的示意图，其中，(a)为初始数据包发送和接收，(b)为简化的基于区域层的PSFCH资源HARQ NAK反馈，(c)为基于位置的多UE协作中继重传；
图14是实施例八的位置区域辅助重传，a)初始传输和HARQ反馈，b)基于波束的重传；
图15是有效PSFCH传输实例，基于：a)PSFCH资源模型，b＝1，b)PSFCH传输时机；
图16是有效HARQ过程实例，基于：a)初始传输，b＝1，b)基于波束的重传；
图17是Tx UE中心的PSFCH模型实例，对于八个AoD具有三个或两个PSFCH模型，a)具有三个PSFCH情况的类型-1；b)具有两个PSFCH时机的类型-1；
图18是Tx UE中心的PSFCH模型实例，对于16个AoD具有4个PSFCH模型和4个PSFCH时机。
具体实施方式
本发明提供一种侧链路重传方法，为使本发明的目的、技术方案及效果更加清楚、明确，以下参照附图并举实例对本发明进一步详细说明。应当理解，此处所描述的具体实施例仅用以解释本发明，并不用于限定本发明。
需要说明的是，本发明的说明书和权利要求书及上述附图中的术语“第一”、“第二”等是用于区别类似的对象，而不必用于描述特定的顺序或先后次序，应该理解这样使用的数据在适当情况下可以互换。此外，术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含，例如，包含了一系列步骤或单元的过程、方法、系统、产品或设备不必限于清楚地列出的那些步骤或单元，而是可包括没有清楚地列出的或对于这些过程、方法、产品或设备固有的其它步骤或单元。
实施例一：
中继功能可以通过中继节点或基站，或者放置在地面上的路侧单元(Road Side Unit，RSU)，或移动集群簇头(Mobile Cluster Header)，或更一般地车辆UE来实现。由于中继节点拥有高天线增益和大传输功率，其覆盖范围可以大很多。然而，在覆盖范围之外，仅移动集群簇头或车辆UE能够负责实现中继功能。为了增强中继覆盖，简单的方法是多次重复传输，但是这种方法会增加信道资源代价。
在本申请中，提高信道效率的同时，我们考虑如何有效地实现车辆UE的中继功能。我们提出了多UE协作中继(Multi-UE Cooperative Relay)，其允许多个中继UE(R-UE)通过使用相同的资源(单个资源或有限的多个资源)同时发送相同的数据包。
在侧链路通信中，Tx UE将数据包发送给其他Rx UE；其中一些Rx UE成功检测到数据包，而一些Rx UE未能检测到数据包。有两个原因导致Rx UE接收失败；一种是由于Rx UE接受信号微弱或经历强干扰导而致检测失败，另一种是由于Rx UE仅安装半双工系统。半双工系统意味着，一旦UE处于传送模式，则不能够接收，反之亦然。从而降低了数据包的接收速率。
多UE协作中继方法解决了两个问题。即，成功检测数据包后，R-UE对相同的数据进行再编码，然后将其转发/重传给初数据包检测失败或半双工问题的其他Rx UE。在该过程中，R-UE优选地考虑在相同资源中转发相同的数据包，以便提高侧链传输效率。因为，如果多R-UE传输之间的最大时间偏移(Timing Offset)小于或等于循环前缀(Cyclic Prefix，CP)长度，那么多R-UE在同一信道上发送相同的编码数据包将不会产生任何符号间的干扰。多UE协作中继可以通过Layer-1中继(Layer-1Relay)或Layer-2中继(Layer-2Relay)来实现，如下所述。
●Layer-1中继：在中继过程中仅涉及物理层；其中仅在成功解码数据包时，多R-UE和Tx UE一样，对接受的数据包进行再编码。在预定时隙或由Tx UE初始发送的SCI指示时隙中，R-UE必须在与Tx UE初始利用的相同物理资源上转发重新编码后的数据包；也就是说，R-UE必须使用相同的PSCCH(Physical Sidelink Control Channel)和与其相关的 PSSCH(Physical Sidelink shared Channel)。在这种情况下，R-UE将不涉及到MAC的调度和HARQ过程，但是可以实施PSCCH和PSSCH上的软合并(Soft-Combining，例如，Chase Combining)。
●Layer-2中继：中继过程涉及物理层和MAC层。在物理层中，仅在成功解码数据包时，R-UE和Tx UE一样，对接受的数据包进行再编码。在MAC层中，R-UE接收至少一个HARQ否定确认(Negative-acknowledgement，NAK)，R-UE必须在与Tx UE初始使用的相同物理资源上转发重新编码的数据包。在这种情况下，R-UE仅仅涉及简单调度(不重新调度资源)，一般不用需要考虑信道条件，数据缓冲状态(Buffer Status)，优先级控制(Priority Control)。调度器只需要简单判断是否应该进行合作重传。
尽管协作中继方法可以应用于Layer-1中继或单播传输中，但在下文中，我们主要考虑针对组播传输的具有Layer-2功能的多UE协作中继。针对多UE协作中继，UE可以被分类为以下两种：
●主R-UE(Primary R-UE)：这种类型的R-UE由网络或组成员指定。主R-UE可以是单个R-UE或多个R-UE，其必须参与多UE协作中继，除非它没有正确地接收到Tx UE数据包。
●辅R-UE(Secondary R-UE)：这种类型的R-UE自愿参与多UE协作中继。在大多数情况下，辅R-UE能够从邻近的Tx UE接收数据包，然后转发给邻近的Rx UE。
然而，是否要配置主R-UE和辅R-UE可以根据实施情况来定。在以下的讨论中，为简单起见，我们不考虑主R-UE，仅假设辅R-UE参与多UE协作中继，并且，中继UE简单地统一为R-UE。
另外，合作中继所涉及的资源可归类为以下两种:
●主中继资源(Primary Relay Resources):这种类型的资源由SCI在初始数据包的PSCCH上指示，并与初始发送数据包相耦合。在多数情况下，它与R-UE用于初始数据包传输的资源相同。
●辅中继资源(Secondary Relay Resources):这种类型的资源由SCI在重传数据包的PSCCH上指示。因此，R-UE可以自主地选择用于转发数据包的资源，并且不同的R-UE可以使用不同的资源。
但是，是否要配置主中继资源和辅中继资源可以根据实施情况来定。在以下的讨论中，为简单起见，我们不考虑辅中继资源，仅假设主中继资源在多UE协作中继中使用。在下文中，中继资源简单地统一为资源。
图1为五个UE进行基于多UE协作中继侧链路组播示意图。如图1所示，有五个UE进行基于多UE协作中继侧链路组播，其中两个UE需要对数据包进行组播。整个传输过程包括初始组播，HARQ反馈，和基于多UE协作中继重传。可以通过如下三个阶段来进行实施：
阶段-1：如图1(a)所示，在初始组播过程中，Tx UE1和Tx UE3在相同时隙中使用不同频率资源发送两个数据包，并由Rx UE2，Rx UE4和Rx UE5进行接收。数据包检测的结果是，Rx UE2和Rx UE4成功地检测由数据信道(例如，PSSCH)发送的数据包，而Rx UE5未能检测到相应的数据包。注意，通常情况下，控制信道(例如，PSCCH)比 数据信道更可靠，因此Rx UE总能通过对控制信道上数据解码来获取SCI信息，从而知道相应的数据包是否也被发送。
阶段-2：如图1(b)所示，在HARQ NAK反馈过程中，依赖于选项-1(Option-1)HARQ反馈机制(同样也可以依赖于选项-2)，Rx UE5在两个PSFCH上发送两个侧链反馈控制信息(Sidelink Feedback Control Information，SFCI)，而其他UE对其进行接收。注意，通常情况下，PSFCH在低信噪比(SNR，如-5～-3dB)范围工作，比数据信道有更低的误码率(BER)，因此可靠性会更高。
阶段-3：如图1(c)所示，在重传过程中，作为中继UE的Rx UE2和Rx UE4成功检测两个数据包后，根据被解码的SCI信息，单独对其进行再编码，然后转发给其他UE。Rx UE2和Rx UE4转发各数据包在独立的信道上被叠加，然后被UE1和UE3接收。UE1和UE3检测到相应的数据包，解决了半双工问题。同时，UE5接收各数据包，将其与先前的缓冲数据进行HARQ软合并，然后对其进行解码，从而实现了由多UE协作中继的重传过程。
图2描述了基于相同示例的多UE协作中继的过程转换图表。
在阶段1中，一旦Tx UE-1或Tx UE-3通过PSCCH发送SCI，Tx UE可以用显式机制(Explicit)或隐式机制(Implicit)通知用于HARQ反馈的PSFCH资源索引和用于重传的PSCCH+PSSCH资源索引给Rx UE。显式机制是使用SCI来通知相关资源；而隐式机制是将初始传输的PSSCH资源索引，与用于HARQ反馈的资源索引和重传资源索引相耦合。
资源耦合可以在时域或频域中执行，或者在两者中同时执行。如果资源耦合在时域中执行，则频域中的资源必须由SCI指示。同样，如果资源耦合在频域中执行，则时域中的资源必须由SCI指示。
在阶段2中，Rx UE-5反馈HARQ NAK，并且所有UE都能够接收到。注意，如果没有反馈NAK，则在初始数据包中由SCI指示的PSCCH+PSSCH的资源可以被其他Tx UE使用。换句话说，被SCI预留资源将自动释放。
在阶段3中，仅当接收到HARQ NAK和/或发生Tx UE半双工时，R-UE-2和R-UE-4进行基于协作中继的重传。重传通常由HARQ NAK触发，而由Tx UE半双工触发的重传可以依赖于Tx UE的区域信息。这需要仔细对MAC层中如何指定潜在R-UE的操作进行规则化。
单UE辅助中继(Single UE assisted Relay)与多UE协作中继之间存在很大差异。在单UE辅助中继中，仅指定一个R-UE参与来自Tx UE的接收，并且将接收的数据包重新编码，然后转发给初始数据包接收没有成功的Rx UE。如果R-UE错误地接收初始数据包，则中继重传将无法实现，从而导致整体性能下降。然而，在多UE协作中继中，多个R-UE涉及接收来自Tx UE的数据包，并且各自将接收的数据包重新编码，然后转发给初始数据包接收没有成功的Rx UE。这样中继成功概率会显著提高。
多UE协作中继能提供至少三个好处：
(1)只要Rx UE中的一个成功检测到来自Tx UE的数据包，作为中继UE的Rx UE就能够实现重传。这极大增加了重传成功概率，并能提供显著的发射分集增益。
(2)在大多数情况下，多UE涉及单数据包的重传将增强了总无线传输功率，从而提供SNR增益。
(3)由于UE位置不同，从不同位置转发/重传数据包在物理意义上能够显著增加覆盖范围。
实施例二：
图3显示在初始传输和重传的示例，其中五个UE能够分别使用两个独立子信道(Sub-channel)，同时需要传送三个数据包(Packet-1，Packet-2，Packet-3)。其中○表示数据包解码成功，而×表示解码失败。在阶段1，Tx UE(UE1，UE3，UE4)在时隙-1(Slot-1)和时隙2(Slot-2)中发送初始数据包。在阶段3，作为R-UE在时隙-3(Slot-3)和时隙4(Slot-4)中执行数据包的重传。时隙-1(Slot-1)中的初始传输和时隙-3(Slot-3)中的重传与图1中示例相同，由此解决了中继重传和半双工问题。在时隙2(Slot-2)和时隙4(Slot-4)中的传输比较简单，其中仅唯一的初始数据包被发送，并由UE3，UE4和UE5中继重传。
如果接收能力允许，可以应用XoR(eXclusive OR)编码机制来提高传输性能。例如，在时隙-1(Slot-1)中，如果Rx UE-5能检测到数据包-1和数据包-2中的一个，R-UE2和R-UE4就能够对数据包-1和数据包-2进行XoR编码，并发送XoR编码后的新数据包。Rx UE对XoR进行解码，然后检测自己相应的数据包，这可以将重传信道资源减少一半。
实施例三：
通信范围可以区分为QoS通信范围(QoS Communication Range，QCR)和无线电通信范围(Radio Communication Range，RCR)。前者与QoS中所需的数据包的可靠性相关联，而后者与发射的无线电波可到达的Tx UE和Rx UE之间的物理距离相关联。图4显示区域覆盖和无线电功率强度之间的关系，其中位于区域中的Tx UE的无线电功率最大，然后逐渐变小，从而影响侧链路覆盖范围。例如，无线电波从与Zone-ID-n相关联的中心区域发射，其中与相同区域相关联的Rx UE可以检测高功率，这确保数据包低错误率(Packet Error Rate，PER)从而提高可靠性。这个高功率区域被粗圈线显示。一旦无线电波到达区域的第一层，接收功率就会下降，但数据包仍然可以被正确解码。这个中等功率区域被定义为RCR，由虚圈线显示。一旦无线电波到达区域的第二层，接收功率变得更低，其中只有少数Rx UE拥有可解码数据包的条件。这个低功率区域被定义为QCR，由细圈线显示。
如果RCR大于QCR，则侧链通信不会产生问题。否则，覆盖问题就会发生，并且需要考虑中继机制来提高覆盖范围。多UE协作中继可以扩展覆盖范围，但并不意味着，协作中继中涉及的UE数量越多，中继性能就越好。因此，澄请协作中继中需要涉及的UE数和UE类型是非常重要的。在本发明中，我们考虑仅限于与一些Zone-ID相关联的UE可以作为R-UE。
从现有报告的测量结果，我们已知控制信道的覆盖范围比数据信道大得多。因此，我们假设控制信道的可靠性足够好，并且在QCR范围内的任何地方Rx UE能够成功检测到SCI。
Tx UE通过PSCCH发送SCI及相关联的PSSCH，而Rx UE接收SCI，并且获取QCR信息。仅在QCR范围内，Tx UE根据PSSCH解码状态然后判断是否反馈ACK/NAK。QCR信息可以依赖于显式方式或隐式方式由SCI指示。显式方式是，SCI携带特定专用比 特(比如，3比特)，直接向Rx UE指示QCR。隐式方式是，SCI不携带任何附加比特，而是重用现有的数据包优先级信息(例如，Priority Information，3比特)来间接指示QCR。因此，隐式方式需要制定和规范(预)配置QCR和数据包优先级之间的映射规则。
另外，协作中继中涉及的UE数量可以根据SCI指示的QCR信息，和/或数据包优先级信息，和/或收发端Zone-ID关系等，由候选R-UE判断自己是否应该参与协作中继。也就说，R-UE数量并不是系统统一决定的，而可以自适应地依赖于每个数据包的QoS等要求。比如，R-UE通过Zone-ID得到和HARQ反馈UE的距离，通过SCI指示得到QCR信息和/或数据包优先级信息，然后根据预定规则或算法，判断自己是否应该参与协作中继。一般来说，数据包优先级越高或QCR越大，参与协作中继的R-UE就应该越多。也就是说，R-UE和反馈UE就算保持比较大的距离也应该参与协作中继。反之亦然。在下述内容中，我们仅仅简单地考虑Zone-ID的信息来控制和限制参与协作中继中的UE数量。
XoR编码(XoR-coding，包括编码和解码)可以分为两种类型；类型-1XoR编码(Type-1XoR-coding)是在物理层进行的，因此需要规范物理层结构和物理层规程，而类型-2XoR编码(Type-2XoR-coding)在MAC层进行的，因此需要MAC层的规范(同时可能也需要一些物理层相应的规范)。
在类型-1XoR编码中，MAC层向物理层提供两个以上的TB，由Tx UE通过无线传输链路发送给Rx UE。同时，MAC层中的调度器会通知物理层，在信道编码之后，哪些TB应该彼此进行XoR编码。Tx UE将XoR编码后的TB发送到Rx UE，并且Rx UE在信道解码之前对接收的TB执行XoR解码。利用类型-1XoR编码的优点是通过具有软合并的HARQ来增强链路性能，同时提高信道效率。但是，缺点是增加了物理层的规范工作。
在类型-2XoR编码中，MAC层准备并生成XoR编码的TB，然后被提供给物理层。因此，物理层不需要知道XoR编码的信息，因此不需要改变物理层结构。利用类型-2XoR编码的优点是能提高信道效率，但不需要太多的物理层规范。然而，缺点是，物理层会丢失HARQ过程中的数据包软合并增益。通常，类型-2XoR编码被称为网络编码(Network Coding)。
在V2X中继中，Layer-1控制信令可以有效地辅助和实现Layer-2中继。换句话说，Layer-1和Layer-2之间的功能应该相互整合，以便有效提高系统性能。例如，在UE高速移动的情况下，HARQ反馈信令和Layer-1测量信息(RSRP)等可以用于即时确定哪些UE可以作为高可靠性和高效率的R-UE候选。
然而，在本申请的协作中继中，将不区分XoR编码的类型。我们认为两种类型的XoR编码都适用于本申请的技术方案。
实施例四：
为了简单但不失一般性，在实施例中，区域的定义仅限制在纬度，但可以简单地在经度和纬度上进行扩展。图5举例了多个区域，其中每个区域分配有不同颜色表示的专用资源池。Zone-ID-n的区域被I n个UE占用(例如，I n＝4)，所有的UE在半双工的制约下进行发送和接收。在这种情况下，UE之间的RCR是从一个区域的边缘到其相邻区域的边缘的距离，而QCR是从一个区域的边缘到其下一个邻居区域边缘的距离(跨越三个区域)。在此QCR是大于RCR，因此引发通信覆盖问题。
本申请提出基于位置区域的协作中继，并依赖于区域中多个R-UE的相互协作。在图5中QCR内，位于Zone-ID-n中的UE可以作为R-UE。数据包将需要被从Zone-ID-(n-1)中的Tx UE发送到Zone-ID-(n+1)中的Rx UE，同样，数据包也将需要被从Zone-ID-(n+1)中的Tx UE发送到Zone-ID-(n-1)中的Rx UE。在此，R-UE以两个阶段执行中继重传：
1)阶段-1：与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的Tx UE发送初始数据包，以及与Zone-ID-(n-1)，Zone-ID-n，Zone-ID-(n+1)相关联的Rx UE接收数据包。在此我们假设在Tx UE相同区域中的所有Rx UE可以成功检测数据包。由于衰落信道(Fading Channel)变化，与Zone-ID-n相关联的邻居区域中的部分Rx UE可以检测到数据包，并且具有相当高的成功率。但是，下一个邻居区域中的Rx UE可以偶然地检测数据包，但具有相当低的成功率。
2)阶段-2：协作中继将依赖于同一区域中的多个UE来执行重传。如图6所示，与Zone-ID-n相关联的四个R-UE自愿发送重新编码的数据包，而与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的Rx UE接收相应的被中继的数据包。
协作中继机制可以扩展到由N x×N y经度和纬度组成的区域，其中Zone-ID可以标记为0,1,…,N xN y。初始数据包传输可以在时隙t中由位于拥有以下Zone-ID(类型-1区域)中的Tx UE执行，
Zone-ID＝y 1N x+x 1,如果(x 1mod2)＝(y 1mod2)；
并且可以通过位于拥有以下Zone-ID(类型-2区域)中的Rx UE在时隙t+Δ中执行基于中继的重传
Zone-ID＝y 1N x+x 1,如果(x 1mod2)≠(y 1mod2)；
其中，Δ是以时隙为单位的HARQ处理时间(Δ≥1)；N x为Zone-ID的经度，N y为Zone-ID纬度值，x和y分别为UE当前位置经度、纬度与参考坐标(0,0)之间的距离，x 1＝0,1,…,N x-1；y 1＝0,1,…,N y-1。
然后，初始数据包传输和基于中继的重传可以分别在类型1(时隙t)和类型2区域(时隙t+Δ)中发送，而另一个初始数据包传输和基于中继的相应重传将相互切换，可以在类型2(时隙t+1)和类型1区域(时隙t+1+Δ)中发送。
另外，可以结合XoR编码机制来执行多UE协作中继，从而更好的提高的传输效率。例如，与Zone-ID-(n-1)相关联的Tx UE-i n-1发送数据包
Figure PCTCN2019105865-appb-000015
该数据包将被其自己区域中的所有Rx UE成功接收。同时，该数据包也被与Zone-ID-n相关联的Rx UE成功接收。但是，该数据包无法被与Zone-ID-(n+1)相关联的Rx UE接收。同样，与Zone-ID-(n+1)相关联的Tx UE-in+1发送数据包
Figure PCTCN2019105865-appb-000016
该数据包将被其自己区域中的所有Rx UE成功接收。同时，该数据包也被与Zone-ID-n相关联的Rx UE成功接收。但是，该数据包无法被与Zone-ID-(n-1)相关联的Rx UE接收。R-UE-i n将XoR编码的数据包
Figure PCTCN2019105865-appb-000017
转发给与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的两个邻居区域中的Rx UE。在检测过程中，与Zone-ID-(n-1)相关联的所有Rx UE是预先知道数据包
Figure PCTCN2019105865-appb-000018
并且通过对
Figure PCTCN2019105865-appb-000019
的XoR解码来检测到
Figure PCTCN2019105865-appb-000020
同样，与Zone-ID-(n+1)相关联的Rx UE可以执行相同的XoR解码检测。其结果，用于与Zone-ID-n相关联，并以转发 XoR编码数据包的R-UE的资源可以被减少一半。
为了实现与Zone-ID-n相关联的R-UE执行基于协作中继重传，R-UE必须确定应该重传哪些数据包，以及如何实施XoR编码的重传。
重传数据包的确定取决于HARQ反馈的类型。基于HARQ反馈机制，NR-V2X支持两种HARQ反馈选项。
●选项-1(Option-1):如果在解码相关联的PSCCH之后Rx UE未能解码相应的TB，则Rx UE在PSFCH上发送HARQ-NAK。否则它在PSFCH上不发送任何信号。
●选项-2(Option 2):如果Rx UE成功解码相应的TB，则在PSFCH上发送HARQ-ACK。如果在解码相关联的PSCCH之后Rx UE未能解码相应的TB，则Rx UE在PSFCH上发送HARQ-NAK。
根据HARQ反馈机制，通过获取的不同的反馈信息，可以考虑三种备选方案：
方案-1(Alternative-1)：如果数据包解码失败，则Rx UE反馈HARQ-NAK。PSFCH资源仅与初始发送数据包耦合。这种方案属于选项-1(Option-1)。失败的数据包必须由与Zone-ID-n相关联的多R-UE逐个重传。以图6中的示例，最大需要八个独立PSCCH/PSSCH资源来实现重传。
方案-2(Alternative-2)：如果数据包解码失败，则Rx UE反馈HARQ-NAK。PSFCH资源与初始发送数据包和由反馈Rx UE的Zone-ID耦合。这意味着，接收反馈HARQ-NAK的R-UE能够潜在地识别来自反馈UE的Zone-ID。这种方案也属于选项-1(Option-1)。通过反馈信息，与Zone-ID-n相关联的R-UE知道与Zone-ID-(n-1)和Zone-ID-(n+1)各自相关联区域的接收状态。因此，可以在数据包
Figure PCTCN2019105865-appb-000021
和
Figure PCTCN2019105865-appb-000022
之间实施XoR编码，以便减少用于R-UE的重传信道资源，从而提高传输效率。
方案-3(Alternative-3)：Rx UE基于选项-2反馈HARQ ACK/NAK。反馈信道是与发送的数据包和反馈Rx UE相耦合。这意味着，接收HARQ ACK/NAK，R-UE能够识别来自反馈的Rx UE ID。通过反馈信息，与Zone-ID-n相关联的R-UE知道三个区域内的Rx UE各自的接收状态。这将增加更多的重传数据包来参与实施XoR编码机会。方案-3中的协作中继XoR编码并不总是有效，它严重依赖于接收状态。因此，作为协作中继XoR编码应该主要依赖方案-2来执行，而一旦可以满足方案-3中的XoR编码条件，则可选择性的用方案-3来执行。因为，用于方案3的总资源一定小于方案2所需的资源。
在实际应用中，根据不同要求的QoS的数据包，通信范围也是不同的。在经度和纬度方向，QCR可以扩展到更多区域，而RCR一般保持不变。因此，通信范围内的QoS满足将变得更加困难，也就是说依赖于恒定的RCR来实现大覆盖范围的侧链路通信将变得更加挑战。为此，使用同样的协作中继方法，同时采用传统的多跳中继机制，通过结合多个区域之间的协作能够实现大覆盖范围的侧链路通信。
实施例五：
为了确保QCR内的所有Rx UE成功接收每个数据包，半双工问题是资源选择中的最大问题之一。在协作中继中，用于重传的资源与用于初始传输的资源相耦合，这样重传资源对所有Rx UE就透明了。这需要针对资源(预)配置和资源选择过程进行规范。
基于时分多路处理(Time Division Multiplexing，TDM)的资源(预)配置能够简单地解决半双工问题。这里，本申请将资源分为两种类型；一个用于初始数据包传输，称为数据包资源(Data Packet Resource，DPR)，另一个用于协作中继传输，称为协作中继资源(Cooperative Relay Resource，CRR)。DPR和CRR被时分多路处理(TDM)，以避免半双工问题。
DPR和CRR都与Zone-ID相关联，在频域中使用相同数量的资源，用L ZONE子信道表示(Sub-channel，SCH，每个包含L ZONE Resource Blocks,RBs)，在时域中拥有相同或不同的资源长度，即DPR可以跨越L DPR时隙，CRR可以跨越L CRR时隙；L ZONE个SCH和L DPR时隙形成DPR的SCB块(SCH Block，SCB)，而L ZONE个SCH和L CRR时隙形成CRR的SCB块；在DPR中，作为SCH的最小传输单元的资源表示为DPR n,t(p)，在CRR中，最小传输单元的资源表示为CRR n,t(p)；其中，n是Zone-ID，t是时域中的时隙索引，p是频域中SCH的索引，L ZONE、L SCH、L DPR和L CRR参数是由RRC(Radio Resource Control，无线资源控制)配置或在系统中被预先配置。
图7说明了Zone-ID，DPR，CRR之间的配置示例，其中，L ZONE＝3，L DPR＝3，和L CRR＝2。例如，在第2个时隙和第3个SCH中与Zone-ID-n相关联的DPR的资源可以表示为DPR n,2(3)，而在第5个时隙和第1个SCH中与Zone-ID-(n+1)相关联的CRR的资源可以表示为CRP n+1,5(1)。在实际资源(预)配置中，应该考虑在DPR和CRR之间预留HARQ反馈过程使用的频域和/或时隙资源。
资源选择规程应考虑减少控制信号开销，这需要将用于DPR的资源与用于CRR的资源相耦合，使得协作中继中涉及的所有R-UE可以隐式地选择相同的资源而无需任何附加的控制信息。为此，应考虑以下预定规则：
●SCB关系：在频域中，与协作中继中涉及的Zone-ID-n相关联的CRR的SCB中的重传资源应该对应于与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的DPR的SCB中的初始传输资源。在时域中，DPR的SCB和CRR的SCB应该彼此相邻。
●XoR编码数据包顺序：基于HARQ反馈机制，RCR内的所有UE能够获取初始数据包的接收状态。依赖于指定规则，每个R-UE能够确定哪些XoR编码的数据包需要被先后发送，例如以上升顺序对数据包进行编号。
例如，该XoR编码数据包数字排序，应该先根据包含与Zone-ID-(n-1)和时隙相关联的初始数据包，然后与Zone-ID-(n+1)和时隙相关联的初始数据包。这确保了所有XoR编码数据包的编号不会冲突。
●CRR资源顺序：在每个SCB资源池的(预)配置中，资源也是按顺序编号。例如，按升序排列。
例如，资源顺序可以从时隙索引的方向预先确定，然后从SCH索引方向确定。这样可以形成二维SCB资源。
●资源选择：协作中继中涉及的R-UE选择在其自己的SCB中(预)配置的CRR的资源。资源的选择是简单地基于XoR编码的数据包顺序和CRR资源顺序之间一对一映射方法来实现。
为了直观地描述协作中继与资源(预)配置的关系，本实施例举一个例子，如图8所 示。在示例中，参数L ZONE＝1，L DPR＝2，和L CRR＝2被(预)配置，而四个UE位于每个区域中，表示UE n,I，其中i＝1,2,3,4。
在时隙-1中，与Zone-ID-(n-1)相关联的Tx UE UE n-1,1和与Zone-ID-(n+1)相关联的Tx UE UE n+1,1分别选择DPR n-1,1和DPR n+1,1来进行初始数据包S n-1,1和S n+1,1的发送。这两个数据必须被QCR内所有的Rx UE成功接收，而该QCR是跨越Zone-ID-(n-1)，Zone-ID-n和Zone-ID-(n+1)的区域。在时隙-2中，同样，与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的Tx UE UE n-1,2和S n+1,2分别选择DPR n-1,2和DPR n+1,2来完成初始数据包S n-1,2和S n+1,2的发送和接收。在时隙-3和时隙-4中，在预留的CRR中执行协作中继，分别为相邻区域中的时隙-1和时隙-2中的初始数据包重传。利用CRR n,3，协作中继主要是协助数据包S n-1,1和S n+1,1的重传。同样，利用CRR n,4与CRR n+1,4，协作中继主要是分别协助数据包S n-1,2和S n+1,2，与S n,2和S n+2,2的重传。
在时隙-1中，数据包S n-1,1和S n+1,1由与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的Tx UE(UE n-1,1和UE n+1,1)发送，并且被与相同Zone-ID相关联的其他三个UE成功接收。然而，由于RCR外的原因，同数据包没有被下一个相邻Zone-ID相关联的Rx UE成功地接收。例如，UE n-1,i无法接收到从UE n+1,1发来的数据包，其中，i＝2,3,4。同时，由于半双工传输模式限制(即，UE n,1也在传输模式)，相同数据包无法被与Zone-ID-n相关联的UE n,1接收。
由于与Zone-ID-n相关联的UE n,i(例如，i＝2,3,4)成功接收RCR内的数据包S n-1,1和S n+1,1，然后数据包被三个R-UE各自XoR编码产生A n,i,t，并自主地以协作中继的方式在时隙-3中的CRR n,3资源上发送，即
Figure PCTCN2019105865-appb-000023
其中n是Zone-ID的索引，i是R-UE的索引(例如，i＝2,3,4)，t是发送初始数据包的时隙的索引(即，t＝1)。
在时隙-2中，与Zone-ID-n相关联的UE n,1受到半双工影响，并且与Zone-ID-n相关联的UE n,3不能正确地从与Zone-ID-(n-1)相关联的UE n-1,2接收到数据包，那么仅有两个与Zone-ID-n相关联的R-UE(UE n,2和UE n,4)能够参与协作中继。因此，XoR编码数据包A n,i,t(使用以上相同公式)在时隙-4中的CRR n,4资源上被发送，其中，i＝2,4和t＝2。
实施例六：
链路控制信息可分为两种类型；一种是与通过物理侧链路控制信道(Physical Sidelink Control Channel，PSCCH)传送的侧链路控制信息(Sidelink Control Information，SCI)，另一种是通过物理侧链路反馈信道(Physical Sidelink Feedback Channel，PSFCH)传送的侧链路反馈控制信息(Sidelink Feedback Control Information，SFCI)。我们的重点是利用Zone-ID的特征来考虑针对PSFCH的资源分配。这样方式能够更有效地实施合作中继传输。
中继功能可以通过多UE协作传输来实现。然而，这并不意味着参与协作中继的UE越多，系统性能就越好。限制协作R-UE的数量的原因至少有两个：
(1)一旦R-UE参与协作中继，它必须将数据包转发到相应的Rx UE。由于半双工限制，同时R-UE无法进行接收。这会降低整体系统性能。
(2)中继传输中涉及的R-UE越多，在频域中的重叠信道就越分散(Dispersion)。因 此，由于时间偏移，Rx UE难以识别接收的同步时间。尽管时间偏移估计可以在时域或频域中用两个相同参考信号的设计方法来解决，一旦UE的数量达到某个基准，接收器将无法估计重叠后的信道，这就是所谓的物理信道破坏。
因此，协作中继必须由有限的自愿R-UE自主执行，而且可以通过地理位置信息来自主决定是否参与协作中继，因此无需使用任何额外的反馈信息。
在LTE-V2X中，用于PSSCH和PSCCH资源池可以按Zone-ID单独(预)配置，在NR-V2X中，除了PSSCH和PSCCH之外，PSFCH资源池也应该考虑相同的(预)配置方式。在本实施例中，我们主要讨论PSFCH和协作中继的有效结合。
通常，用于PSFCH的资源池可以分为两类：一类是与公共资源池相关，与UE在地理位置无关，任何UE都可以使用该公共资源池；另一类是与基于Zone-ID的资源池相关，该资源池只能被位于同一区域中的UE使用。
公共PSFCH资源池是(预)配置的，其中任何UE都能够选择PSFCH资源用于HARQ反馈。作为PSFCH的资源可以与PSCCH/PSSCH的资源相耦合，而耦合的信息可以由PSCCH发送的SCI来指示，或者由(预)配置来相互映射。在下文中，为简单起见，我们仅描述用SCI来显式指示PSFCH资源，尽管隐式指示和(预)配置机制也适合资源分配。一旦需要通过PSSCH来传输数据包，就必须用PSCCH来传送相关的SCI，并同时指示PSFCH的资源。其中PSCCH与其相关的PSFCH之间存在一定的时间间隔。如图9(a)所示，Tx UE通过PSCCH传输SCI信息，通过PSSCH传输相关传输块(Transport Block，TB)，而SCI包含公共PSFCH资源索引信息。Rx UE接收SCI及其相关数据包，并检测是否有错误。仅在Rx UE检测到所接收的数据包由错误时，在侧链路HARQ反馈被触发。依赖于HARQ选项-1的情况下，所有Rx UE使用相同的PSFCH资源来反馈HARQ的NAK，PSFCH资源仅与初始发送的初始数据包耦合，其中反馈Rx UE相关联的Zone-ID是无法被区分的。公共PSFCH资源池的(预)配置和PSFCH资源的SCI指示可以被总结为：――(预)配置：在公共PSFCH资源池中的M资源可以用索引m来指示，其中m＝1,2,…,M。每个资源可以表示为
Figure PCTCN2019105865-appb-000024
――SCI中的指示比特：
Figure PCTCN2019105865-appb-000025
比特表示所选的索引m。
基于Zone-ID的PSFCH资源池可以被独立地(预)配置，其中仅位于相同Zone-ID的UE能够选择PSFCH资源进行HARQ反馈。一旦需要传输数据包，SCI会被用来指示基于Zone-ID的PSFCH资源，其中PSCCH和相关联的PSFCH之间具有统一的时间间隔。如图9(b)所示，Tx UE通过PSSCH和PSSCH组播SCI消息和相关TB，并且SCI信息包含不同Zone-ID统一的索引-1来指示与Zone-ID相关联的PSFCH资源。Rx UE接收SCI及其相关数据包，并检测是否有错误。仅当Rx UE检测到所接收的数据包有错误时，Rx UE会使用与所位置的相同的Zone-ID相关联的PSFCH资源来触发相应的HARQ反馈。其中反馈UE可以基于每个ZB中的Zone-ID的标识来区分，但代价是需要使用更多的PSFCH资源。实际上，如果(预)配置的PSFCH资源池是基于区域的话，那么需要为PSFCH保留N倍资源。关于PSFCH资源消减方案将在实施例7中讨论。
SCI中的PSFCH指示比特的数量是不变，这是因为尽管基于区域的资源池的配置在高层中需要使用更多参数，但这两种情况仅需要一个索引。基于区域的PSFCH资源池的(预) 配置和针对PSFCH资源的SCI的指示可以被总结为：
――(预)配置：每个与Zone-ID-n相关联的PSFCH资源池中的M资源可以用索引m来指示，用于资源表示的公式可以修改为
Figure PCTCN2019105865-appb-000026
其中，m＝1,2,…,M，n＝0,1,…,N-1，N是ZB中的区域数。
――SCI中的指示比特：
Figure PCTCN2019105865-appb-000027
比特表示所选的索引。
值得的注意是，Tx UE和R-UE可以基于与Zone-ID相关联的PSFCH资源的盲检测来隐式地获取索引n。
如图10所示，Pool-1，Pool-2和Pool-3来表示的三个资源池(每个资源池包括PSSCH，PSCCH和PSFCH的信道资源)被(预)配置在Zone-ID-0，Zone-ID-1，Zone-ID-2的三个区域中，其中，这些区域分别拥有UE-1，UE-2，UE-3。为简单起见，假设资源池仅包含频率资源。在组播中，时隙-1中的Tx UE-1通过PSCCH发送SCI信息，并通过对应于Zone-ID-0(或资源池-1)的PSSCH发送其相关联的TB。同时，SCI包含PSFCH资源的指示信息。Rx UE-2和Rx UE-3从PSCCH接收SCI之后，这两个Rx UE都得知在时隙-4中分配的PSFCH-2和PSFCH-3的资源信息，并且与Tx UE-1的PSCCH/PSSCH相耦合。其中，PSFCH和PSCCH具有两个时隙的间隔时间。Rx UE-2和Rx UE-3通过解码相关联的TB，分别确定是否需要反馈HARQ-NAK给Tx UE-1。
由于地理关系，Rx UE-2接近于Tx UE-1，而Tx UE-3远离于Tx UE-1。其结果，Rx UE-2能在PSSCH上正确地解码数据包，而Rx UE-3却无法实现。由于利用HARQ NAK反馈机制，Rx UE-3通过PSFCH-3将相应的NAK反馈给Tx UE-1，而Rx UE-2虽然已经被指示分配了PSFCH-2但不反馈任何HARQ信息。应该强调的是，Rx UE-2不在时隙-4中发送任何数据，因此，它能够从Rx UE-3接收SFCI。这就是在多UE协作中继中，依赖于选项-1的侧链路HARQ反馈的有益原因。同样由于地理关系，Rx UE-2能确保在PSFCH-3上检测到SFCI，而Tx UE-1却无法做到。
在重传方面，Rx UE-2由于能够接收到PSCCH的SCI信息和PSFCH-3的反馈信息，因此分别知道Tx UE-1以及Rx UE-3的区域位置，因此，Rx UE-2自愿地负责基于协作中继的重传。另外从地理位置的角度来看，Rx UE-2比Tx UE-1传输链路会更好，增益会更高。同样，本例可以扩展到多UE协作中继中。
为了直观地描述多UE协作中继如何正常实施，我们给出了拥有11个UE的示例，位于不同区域的UE表示为UE-i，如图11所示，其中位于Zone-ID-4中的Tx UE-5发送初始数据包，而位于其他区域的其他Rx UE进行相应的接收。位于RCR内的Rx UE(在中心和第一层，用粗线围绕)可以正确地解码数据包，而Rx UE位于RCR之外但在QCR之内(在第二层中，被细线围绕)，可能无法正确地接收数据包。在该示例中，如图11(a)所示，第二层中的Rx UE-1和Rx UE-11从Tx UE-5接收数据包失败。根据选项-1 HARQ反馈机制，如图11(b)所示，Rx UE-1和Rx UE-11将通过两个独立的PSFCH资源(用不同的深灰色显示)发送两个相应的SFCI(NAK)给Tx UE-5，与此同时，也被其他UE接收。由于地理原因，仅有一些UE能够检测SFCI，并隐式地获取它们对应的区域位置。例如，UE-2，UE-3，...，UE-6可以从Rx UE-1检测到SFCI并获取其区域位置，而UE-5，UE-6，...，UE-10可以从Rx UE-11检测到SFCI并获取其区域位置。因此，正确检测SFCI的UE可 以成为多UE协作中继的候选，并且靠近反馈UE的候选中的UE可以自愿地进行协作中继重传。其结果，如图11(c)所示，作为中继的R-UE-2和R-UE-3协同参与针对Rx UE-1的重传，而作为中继的R-UE-8，R-UE-9和R-UE-10协同参与针对Rx UE-11的重传。由于协作中继使用的是相同信道，所以Rx UE-1和Rx UE-11不需要区分哪些R-UE参与了协作中继重传。
参与多UE协作中继重传的UE数是通过UE间的相互区域位置来彼此自主决定的。这样能产生很多益处：
●可以显着改善PSFCH覆盖范围。这是因为传输初始数据包的Tx UE可能不一定能在PSFCH上检测到对应的SFCI，而接近反馈Rx UE的R-UE却能正确地检测到SFCI。
●由于多个UE协同参与基于中继的重传，从而确保了多UE分集增益，这样可以显着提高PSSCH的覆盖范围。
●基于Zone-ID(预)配置的PSFCH资源和基于PSCCH的指示，对应于反馈UE的Zone-ID可以被其他UE隐式地获取，并且只有一部分R-UE参与协作中继。因此，从半双工的角度来看，大大提高了系统效率。
实施例七：
由于使用区域(预)配置资源池，因此需要为PSFCH保留N倍资源。这是一个相当高的信令资源开销，特别是在ZB较大的情况。此外，PSFCH可靠性比PSCCH的要差，因此只有和反馈UE在其相邻的区域中，可能可以检测到PSFCH上的SFCI。这似乎是缺点，但可以利用此属性来减少配备给PSFCH的资源数量。如实施例八的图11所示，由Rx UE-1在PSFCH上发送的SFCI只能被UE-2和UE-3检测到，同样由Rx UE-11发送的SFCI只能被UE-8，UE-9，UE-10检测到。因此，如果两个反馈Rx UE使用相同的PSFCH资源，对两组UE相互接收来说都不会有影响。
因此，本实施例考虑以每个区域层(Zone-Tier)来分配PSFCH资源。另外，分配PSFCH资源是以初始传输中涉及的Tx UE为中心的。这意味着，第一个PSFCH资源被分配到Tx UE所在的中心区域，第二个PSFCH资源被分配到Tx UE为中心的第一层区域，以此类推，第k个PSFCH资源被分配到Tx UE为中心的第(k-1)层区域，直到QCR内的最后一个区域层为止。因此，PSFCH资源的数量取决于QCR内的区域层数，而不是Zone-ID数。当然，基于(预)配置或SCI指示，所有PSFCH资源与初始数据包传输使用的PSCCH/PSSCH相关联。在基于区域层的PSFCH资源方案中，Rx UE需要显式地或隐式地获取与Tx UE之间的区域层的关系。
PSFCH资源池的表示可以被修改为
Figure PCTCN2019105865-appb-000028
其中k是(预)配置的区域层的索引，并且中心区域用k＝0来表示，m k＝1,2,…,M k以及M k是第k区域层中的PSFCH资源数。
由于在每个区域层中在PSFCH上发送相应SFCI的概率是不同的；即，区域层索引越大，概率越高。因此，每个区域层中的PSFCH资源数量应该被单独(预)配置，其规则为M 0≤M 1≤…≤M K-1，其中K是QCR内的区域层数。如果针对每个区域层单独执行资源指示的话，则可能导致K倍的信令开销来指示SCI中的PSFCH资源。本实施例中，PSFCH资源可以由索引m统一指示，其中，m k＝m mod M K，m k＝1,2,…,M K-1。
图12示例了多UE协作中继，其中考虑了基于区域层的PSFCH资源分配。在该示例 中，图12(a)显示了初始数据包的发送和接收，而图12(c)显示了多UE协作中继传输(和图11中的示例相同)。在图12(b)中，唯一的区别是基于区域层PSFCH资源的HARQ NAK反馈，其中三个独立的PSFCH资源分别被分配在中心区域，第一个区域层(为淡灰色)，和第二个区域层(为深灰色)中。每个Rx UE从Tx UE-5检测到PSCCH上的SCI，然后基于中心Tx UE-5的Zone-ID和Rx UE的Zone-ID确定Rx UE位于其中的哪个区域层。同样，Rx UE-1和Rx UE-11将通过两个与第二区域层相关联的PSFCH发送两个相应的SFCI(NAK)给Tx UE-5，与此同时，也被其他UE接收。因此，UE-2和UE-3从反馈Rx UE-1检测到SFCI，而UE-8，UE-9和UE-10从反馈Rx UE-11检测到SFCI。其结果，UE-2和UE-3协同参与针对Rx UE-1的重传，而UE-8，UE-9和UE-10协同参与针对Rx UE-11的重传。
由于可以通过位置坐标由Rx UE获取Tx UE的区域位置，因此Rx UE能够计算出Tx UE和Rx UE之间的距离，从而推导出Rx UE属于哪个区域层。在这种情况下，Zone-ID不需要被配置，如图13所示，区域层可以被简化。其中Tx UE需要对其位置坐标进行组播，而Rx UE只需要知道自身坐标。对于用于HARQ反馈的PSFCH资源分配，我们保持了相同的基于区域层的(预)配置方法。类似于Rel-12中的设备到设备(Device-to-Device，D2D)通信中使用的发现信道(Discovery Channel)的配置，每个设备配置有多个资源池，其中每个资源池与参考信号接收功率(Reference Signal Received Power，RSRP)范围相关联。此外，基于每个IP数据包或每个数据无线承载(Data Radio Bearer)所需的通信范围，区域层宽度(Zone-tier Width，米为单位)和QCR内的区域层数也是必须被(预)配置的。因此，基于区域层的分配机制可以显著减少PSFCH资源。然而，与基于区域的PSFCH资源分配相比，由于区域层中的位置分辨率受限，自愿参与多UE协作中继重传的R-UE的数量可能会增加。这略微会影响中继重传的总体性能。
为了减少传输位置信息的L1信令开销，每个Tx UE通过RRC参数在数据信道(如，PSSCH信道)上发送位置信息，并且每个Rx UE通过该RRC参数更新位置表中的位置信息。位置表应该包括Tx UE位置信息和该Tx UE的相关ID。UE可以通过接收由SCI指示的Tx UE ID，然后在RRC位置表中查找Tx UE ID，然后隐式地获取相应的Tx UE的位置。因此，Tx UE仅需要通过SCI发送其UE ID，而不需要SCI直接传送位置信息。
――每个UE拥有与位置表相关联的RRC参数，其中位置表的大小和能够被存储Tx UE的最大数量相关，Nmax(如，Nmax＝64)。每个位置和Tx UE ID指向互相映射。
――在组播的HARQ选项-2中(Option-2)，每个PSFCH与其UE ID相关联。因此，只要Rx UE已经通过RRC参数将其位置发送给其他UE的话，每个Tx UE就能知道每个Rx UE的位置。
实施例八：
重传也可以依赖于发射波束成形(Transmit Beamforming)机制。在组播中，由于多个Rx UE位于组中的不同位置，接收来自Tx UE电波方向也就不同，因此依赖于发送波束成形的初始传输是不可行的。然而，在重传中，这样的物理约束明显变小，因为Rx UE接收初始包的错误概率比较低，也就是说，在组播中需要重传的UE数也相应变少。这为Tx UE提供了单方向Rx UE的波束成形发射机会。发射波束成形可以提供如下几个好处：
――将更多发射能量集中在单向上，提高传输链路的可靠性。这确保了Tx UE可以有效地使用毫米波(mm Wave)中的高频带(如，新ITS频带)。
在mm Wave中，发送和接受波束宽度比微波波束窄得多。因此，窄波束宽度导致对发送端和接收端之间的波束对准有更高要求。尤其是在V2X通信中，要求很高的波束对准灵敏度。这就需要L1控制信息(如，PSFCH)来快速指示Tx UE和Rx UE间的波束方向。――对其他Rx UE产生较少的干扰。可以为其他Tx UE重用相同的资源提供更好的机会。
为了实现发射波束成形，Tx UE需要发射角(Angle of Departure，AoD)信息。为此，在考虑UE车辆以高速行驶的情况下，Tx UE必须获得信道状态信息(Channel Status Information，CSI)的反馈。这将极大地增加了物理层的反馈信令开销。相比之下，依赖HARQ反馈机制也能够获取基于波束成形的重传的AoD信息，而且无需任何额外信令。通过基于Zone-ID的与PSCCH相关联的PSFCH资源池信息，或者由PSCCH激活的PSFCH资源信息，Tx UE可以隐式地获取与HARQ反馈UE相关联的位置区域，从而推导出相关的AoD。
图14例示了由Tx UE和Rx UE间的位置区域辅助的且基于波束成形的重传，由三个传输阶段进行：
――在阶段1中，位于Zone-ID-4的Tx UE-5通过PSCCH及其关联的PSSCH执行初始数据包传输，而位于其他区域的Rx UE进行相应的接收。多数Rx UE可以正确地解码数据包，而只有少数Rx UE错误解码。如图14(a)示例，仅Rx UE-3错误地接收了数据包。
其中，用于Rx UE的HARQ反馈的PSFCH的资源是(预)配置的。Rx UE使用PSFCH的资源或与PSCCH相关联，或由SCI在PSCCH上指示，并且与Tx UE是相耦合。
――在阶段2中，解码错误的Rx UE依靠选项-1(Option-1)的反馈机制，通过被激活的PSFCH发送相应的SFCI(NAK)。如图14(a)示例，Rx UE-3通过PSFCH将其相应的HARQ NAK反馈给Tx UE-5。
Tx UE-5通过检测PSFCH上的SFCI来隐式地获取其位置Zone-ID，并推导出AoD。
通过Tx UE的坐标与第一层中的Rx UE的相邻区域之间关系进行数学推导，所得AoD的分辨率约为45°。通常，接收失败的Rx UE可能距离Tx UE比较远，一般位于第二层的下一个邻居区域或甚至更多，但分辨率相同。
――在阶段3中，Tx UE根据推导出的AoD将数据包用波束成形发送到Rx UE。如图14(b)示例，Tx UE-5将天线波束指向Rx UE-3，并将数据包发送到Rx UE-3，这确保了重传链路的可靠性。
重传应该由Tx UE自适应地执行。因为，有些情况基于波束成形的重传可能是无法实现的，如：
――Tx UE和Rx UE位于同一区域，这将无法推导出AoD。但是，这种情况很少发生，因为在相同区域中的Tx UE和Rx UE之间的无线链路一般会足够好。也就是说，如果考虑HARQ选项-1的话，则不需要HARQ NAK反馈。
――Tx UE检测到多个NAK反馈的Rx UE，并且这些Rx UE在不同的区域中。通常，天线波束只能调向单个方向，多区域局面是无法应对的。
本申请的波束成形的机制能有利于数据包的重传，但是用于PSFCH的独立资源将增加 N x×N y倍。因此，我们新设计了具有多种模型(Pattern)的PSFCH资源，目的是尽量减小PSFCH的使用资源，但同时仍然可以通过检测PSFCH来获取反馈UE的Zone-ID。用于SFCI传输的PSFCH资源是(预)配置，或通过PSCCH上的SCI激活的。
PSFCH资源模型可以分为两类：一类与基于区域块(ZB)的PSFCH资源模型，另一类与以Tx UE为中心的PSFCH资源模型。
一般，ZB需要N x×N y个独立资源(包括Tx UE区域中的资源)来区分Zone-ID。但是ZB尺寸变大，控制通信令也就变得越大。因此，本实施例提出了新的HARQ反馈规程；主要是利用分布式PSFCH资源模型(Distributed PSFCH Resource Patterns，DFRP)，使PSFCH资源大大的减少。DFRP资源模型集(Set)由PSFCH资源模型组成，并由RRC配置或在系统中预先配置。
在DFRP设计中，基资源(Base Resource)被定义为用于PSFCH的基础资源，被反馈UE使用发送其HARQ NAK。PSFCH基资源可以被定义为频域，时域或码域资源。为简单起见，PSFCH中的基资源的数量为n bs，其中，n bs＝2 b，b是整数，b≥1。PSFCH资源模型和资源模型集依赖于ZB大小以及基资源，并由基资源组合而成。被组合成的每个PSFCH资源模型拥有独立的索引。Tx UE发送的SCI其中包含PSFCH资源模型索引以及PSFCH的传输时机信息。Rx UE使用PSFCH资源模型反馈SFCI给Tx UE，Tx UE对其SFCI信号检测从而识别反馈UE的HARQ信息和其Zone-ID。Tx UE通过在不同时机接收到的不同PSFCH资源模型逐步提高其AoD分辨率。DFRP需要N DFRP的PSFCH资源(包聒时间和频域资源)为
Figure PCTCN2019105865-appb-000029
DFRP主要被设计用于基于波束成形的重传，是针对单个Rx UE或针对位于相同区域中多个Rx UE场景，这些Rx UE错误地接收了自PSSCH的数据包。但是，通过DFRP检测，如果Tx UE获取到位于不同区域中的多个Rx UE的Zone-ID信息，那么Tx UE就会考虑使用具有全向天线的数据包重传。
图15例示了2个基资源的PSFCH传输情况(相当于b＝1)，其中，每个资源模型由2个基资源组成，而四个PSFCH资源模型组成PSFCH资源模型集，可以在四个PSFCH传输时机反馈HARQ信息(ZB由16个Zone-ID形成，N x＝4和N y＝4)。在图15(a)中，四个PSFCH资源模型分别由两个基资源组成，一个用淡灰色，另一个用灰色，位于相同区域中的Rx UE可以共享PSFCH资源。在图15(b)中，与Zone-ID-10相关联的Tx UE通过PSCCH将SCI发送到其他Rx UE，假设仅与Zone-ID-0相关联的Rx UE接收数据包失败，并且需要通过PSFCH资源模型将HARQ NAK反馈给Tx-UE。其中，SCI包含的信息有，PSCCH和PSFCH之间发送时间差，PSFCH时机间隔，PSFCH资源模型索引等。包括PSFCH资源模型索引的原因是Tx UE可以在任何PSFCH时机自适应地控制重传。这些参数根据情况可以被(预)配置的。
在四个PSFCH传输时机中，与Zone-ID-10相关联的Tx UE隐式地获取与Zone-ID-0相关联的反馈UE的Zone-ID，由此Tx UE自适应地执行基于波束成形的重传。
——在PSFCH传输时机-1(Occasion-1)中，与Zone-ID-0相关联的Rx UE基于资源模型-1(Pattern-1)在PSFCH(淡灰色资源)上发送HARQ NAK。然后，与Zone-ID-10相关联的Tx UE检测到NAK信号，并粗略地获取反馈UE的位置，可能的位置是Zone-ID-0，1，4，5其中的一个，或是Zone-ID-10，11，14，15其中的一个。
如果Tx UE从两个PSFCH接收两个SFCI，则Tx UE应立即执行具有全向天线的重传。——在PSFCH传输时机-2(Occasion-2)中，与Zone-ID-0相关联的Rx UE基于资源模型-2(Pattern-2)在PSFCH(还是淡灰色资源)上发送HARQ NAK。然后，与Zone-ID-10相关联的Tx UE检测到NAK信号，并获取反馈UE的位置，可能的位置是Zone-ID-0，1，4，5其中的一个。
如果该AoD分辨率足以用于基于波束成形的重传，则与Zone-ID-10相关联的Tx UE立即执行重传，否则等待下一个SFCI再做决定。显然，与时机-1相比，Tx UE获取的AoD分辨率得到改善。
——在PSFCH传输时机-3(Occasion-3)中，与Zone-ID-0相关联的Rx UE基于资源模型-3(Pattern-3)在PSFCH(还是淡灰色资源)上发送HARQ NAK。然后，与Zone-ID-10相关联的Tx UE检测到NAK信号，并获取反馈UE的位置，可能的位置是Zone-ID-0，1其中的一个。
如果该AoD分辨率足以用于基于波束成形的重传，则与Zone-ID-10相关联的Tx UE立即执行重传，否则等待下一个SFCI再做决定。显然，与Zone-ID-10相关联的Tx UE获取的Zone-ID的分辨率得到进一步改善。
——在PSFCH传输时机-4(Occasion-4)中，与Zone-ID-0相关联的Rx UE基于资源模型-4(Pattern-4)在PSFCH(深灰色资源)上发送HARQ NAK。然后，与Zone-ID-10相关联的Tx UE检测到NAK信号，并获取与Zone-ID-0相关联的反馈UE的位置。这是由Tx UE获取的与Zone-ID-0相关联AoD的最高分辨率。
图16显示了具有自适应重传控制的HARQ过程示例，a)具有全向天线的初始传输，b)具有定向天线的基于波束成形的重传。在时隙-1中，于Zone-ID-10相关联的Tx UE的完成初始传输，以及通过Rx UE从时机-1(时隙-2)和时机-2(时隙-4)的PSFCH资源模型中接收NAK反馈，从而获取Rx UE的粗略Zone-ID，然后判断AoD分辨率是否足够。于是，Tx UE在时隙-6中用波束成形进行早期重传，其中PSCCH上发送的SCI重新指示了PSCCH和PSFCH之间发送时间差，PSFCH时机间隔，PSFCH资源模型索引等。一旦与Zone-ID-0相关联的Rx UE在PSCCH上检测到SCI，它就得知先前SCI指示的信息被当前SCI覆盖。此外，是否进行早期重传取决于Tx UE自身判断来实现。
实施例九：
由于Rx UE知道与Tx UE相关联的位置Zone-ID，因此围绕Tx UE的Rx UE可以基于Tx UE为中心找到用于HARQ反馈的PSFCH模型资源。图17是针对在区域ZB通信范围内的PSFCH模型的示例，其中与Zone-ID-4相关联的Tx UE通过PSCCH发送SCI，而在Tx UE周围的九个区域中的Rx UE接收SCI。
如图17(a)所示类型-1(Type-1)，其中三个PSFCH资源模型分别由两个基资源组成，一个用淡灰色，另一个用灰色，位于相同区域中的Rx UE可以共享PSFCH资源。如果Rx  UE成功检测到SCI，但没有成功解码数据包的话，则Rx UE基于类型-1的PSFCH模型资源反馈HARQ NAK给Tx UE，因此有三个PSFCH时机可以发送反馈信号。这种类型通过三个PSFCH时机逐渐提高AoD分辨率，最终能够到达45°的AoD分辨率；第一个PSFCH时机得到180°分辨率，第二个PSFCH时机得到90°分辨率，第三个PSFCH时机得到45°分辨率。但是，在模型1(Pattern-1)中，如果Tx UE在两个基资源上都检测到反馈信号的话，基于波束成形的重传就无法实现，从而只能实施具有全向天线的数据包重传。会有两种可能性。第一种是，Rx UE接收到错误的数据包，并且和Tx UE在同一个Zone-ID-4中，Rx UE将同时使用两个PSFCH基资源发送反馈信号。第二种是，两个以上Rx UE接收到错误的数据包，但是和Tx UE在相对的区域中，不同的Rx UE将使用两个PSFCH基资源发送反馈信号。
另外，如图17(b)所示类型-2(Type-2)，通过使用两个PSFCH资源模型，可以更有效地执行HARQ反馈。类型-2中的PSFCH资源模型-1和类型-1中的PSFCH资源模型-1是相同，用于粗略区分AoD。通过检测SFCI，Tx UE能够识别是否是单个方向上的Rx UE，从而判断是否需要使用波束成形机制的重传。
在模型-2中，模型设计是采用了两个PFSCH基资源的组合，并产生四个索引以隐式指示四个Zone-ID，即：
——第一个PFSCH基资源(浅灰色)与Zone-ID-3和Zone-ID-5相关联。意味着，如果Rx UE位于任一区域中，则它仅在该基资源上发送SFCI。
——同样，第二个PFSCH基资源(深灰色)与Zone-ID-1和Zone-ID-7相关联。
——两个PFSCH基资源(浅深混合颜色)与Zone-ID-2和Zone-ID-6相关联。意味着，如果Rx UE位于任一区域中，则它在两个基资源上发送SFCI。
——Zone-ID-0和Zone-ID-8没有相关联的资源。意味着，如果Rx UE位于任一区域中，则它不发送任何信号。
一旦Rx UE有超过两个数据包解码失败，就会在模型-2中产生一种模糊性。在这种情况下，Rx UE可以通过两个PSFCH基资源发送SFCI。因此，在不改善AoD的准确度的基础上，Tx UE仅依赖于模型-1中得到的AoD来执行基于波束成形的重传。
图18是针对在区域ZB(5×5区域)通信范围内的PSFCH模型的示例，其中与Zone-ID-12相关联的Tx UE通过PSCCH发送SCI，而在Tx UE周围的25个区域中的Rx UE接收SCI。在这种情况下，依赖于四个PSFCH资源模型，Rx UE可以有四个PSFCH时机以触发HARQ反馈，其中仅模型-4采用两个PFSCH基资源的组合，产生三个索引以隐含地指示三个Zone-ID。值得注意的是，Zone-ID-0和Zone-ID-6只需要具有相同索引来指示AoD，Zone-ID-16和Zone-ID-20也同样如此。这样可以逐步提高AoD的分辨率，分别为180°，90°，45°和22.5°。
同样，如果SCI包含PSFCH资源模型索引信息，则Tx UE能够控制AoD的分辨率，并且自适应地执行基于早期波束成形的重传，类似图16中示例。
另外，侧链重传可以基于波束成形机制实现，特别是当涉及到毫米波(mm Wave)的情况下。为了优化性能，我们可以考虑以下因素:
——PSCCH和PSFCH等控制信道可以在较低频段(6GHz以下频段)内进行，以确保更 大的侧链路覆盖范围。
——PSSCH等数据信道可以在高频段(如毫米波)中进行，以确保更高的侧链传输容量。
这样做优势是，控制信息相对比较小，因此可以用有限的低频带来实现，而数据信息要大得很多，因此可以用高频带实现。前者可能不一定需要涉及波束成形机制，而后者必须涉及波束成形机制。
同样UE位置依赖于定位区域机制，但也可以基于位置坐标来实现。由于在组播中Tx UE位置是可知的，Rx UE根据他们的相对位置坐标计算出Tx UE和Rx UE之间的AoA(Angle of Arrival)，由此Rx UE选择以Tx UE为中心的PSFCH资源进行HARQ反馈。值得注意的是，AoA被有限比特量化，并且基于(预)配置方式，独立的PSFCH资源被分配给每个量化的AoA。因此，与每个组播传输相关联的PSFCH资源集仅与Tx UE和量化的AoA相关。一旦Tx UE接收到相应的PSFCH，它就可以隐式地计算出AoD(Angle of Departure)并实现基于波束成形的重传。
基于波束成形的重传可以由同组成员(Groupcast Member)的协作R-UE来执行，尤其是在毫米波部署的情况下。
以上具体实施例是以地理距离(Geographical Distance)和地理位置(Geographical Location)进行描述的；实施例同样可以用无线电距离(Radio Distance，如RSRP值)进行描述。在实际应用中也是如此。
以上对本发明的具体实施例进行了详细描述，但其只是作为范例，本发明并不限制于以上描述的具体实施例。对于本领域技术人员而言，任何对本发明进行的等同修改和替代也都在本发明的范畴之中。因此，在不脱离本发明的精神和范围下所作的均等变换和修改，都应涵盖在本发明的范围内。

Claims (30)

  1. 一种侧链路重传方法，其特征在于，在组播中至少有一个发送设备Tx UE，每个Tx UE向接收设备Rx UE发送第一数据包；
    当一些Rx UE接受到链路上的第一数据包失败时，其它Rx UE成功检测到第一数据包，并对第一数据包进行再编码，生成第二数据包，然后将第二数据包在与Tx UE初始使用的相同资源中同时转发/重传给第一数据包检测失败、和/或在半双工状态下工作的其它UE。
  2. 根据权利要求1所述的侧链路重传方法，其特征在于，发送设备Tx UE与接收设备Rx UE建立组播通信，所述多UE协作中继重传方法包括：
    ——至少一个发送设备Tx UE在第一时隙发送第一数据包，至少一个接收设备Rx UE成功检测由数据信道发送的第一数据包，至少一个接收设备Rx UE未能检测到所述第一数据包；
    ——未能检测到所述第一数据包的接收设备Rx UE在物理层侧链反馈信道PSFCH上发送侧链反馈控制信息SFCI，组播通信中的其它UE对其进行接收；其中，所述侧链反馈控制信息用于指示是否成功检测到所述第一数据包；
    ——成功检测所述第一数据包的接收设备Rx UE作为R-UE，根据被解码的SCI信息，单独对所述第一数据包进行再编码，生成第二数据包，然后将第二数据包在第二时隙转发给其它UE；初始发送第一数据包的发送设备Tx UE检测到所述第二数据包，解决了半双工问题，同时，未能检测到所述第一数据包的接收设备Rx UE接收到所述第二数据包，将所述第二数据包与先前的软储存的第一数据包进行HARQ软合并，然后对其进行解码，从而实现了由多UE协作中继的重传过程；
    其中，所述第二时隙为第一时隙之后的一个时隙。
  3. 根据权利要求1所述的侧链路重传方法，其特征在于，如果第一数据包和第二数据包是完全相同的，第一数据包的信令中不需要有第二数据包的相关控制信息；如果第一数据包和第二数据包是不相同的，在第一数据包的信令中必须具体隐式或明式地指示其第二数据包相关控制信息。
  4. 根据权利要求1所述的侧链路重传方法，其特征在于，如果使用相同资源，就不需要在第一数据包中使用信令来指示使用的资源；但是，如果使用不同的单个资源或有限的多个资源，就必须通过第一数据包中的信令来具体指示。
  5. 根据权利要求1所述的侧链路重传方法，其特征在于，如果未能检测到所述第一数据包的接收设备Rx UE反馈HARQ NAK，并且被组播通信中的其它UE接收到，这就意味着由SCI指示的PSCCH+PSSCH的资源将被多UE协作中继使用；如果未能检测到所述第一数据包的接收设备Rx UE没有反馈HARQ NAK，则在第一数据包中由SCI指示的PSCCH+PSSCH的资源索引可以被其它Tx UE使用，即被SCI预留的资源将自动释放。
  6. 根据权利要求5所述的侧链路重传方法，其特征在于，所述第一数据包传输失败的原因，包括：Rx UE接受信号微弱或经历强干扰导而致检测失败；或者，Rx UE仅安装半双工系统。
  7. 根据权利要求1所述的侧链路重传方法，其特征在于，多UE协作中继通过Layer-1中继或Layer-2中继来实现；
    ——所述Layer-1中继，在中继过程中仅涉及物理层；其中，仅在成功解码第一数据包时，多个Rx UE(R-UE)和Tx UE一样，对接收的第一数据包进行再编码，在预定时隙或由Tx UE初始发送的SCI指示时隙中，R-UE在与Tx UE初始使用的相同资源上转发重新编码后的第二数据包；也就是说，R-UE必须使用相同的物理侧链路控制信道PSCCH和与其相关的物理侧链路共享信道PSSCH，在这种情况下，R-UE将不涉及到MAC的调度和HARQ过程，但是可以实施PSCCH和PSSCH上的软合并；
    ——所述Layer-2中继，在中继过程涉及物理层和MAC层；在物理层中，仅在成功解码第一数据包时，R-UE和Tx UE一样，对接收的数据包进行再编码；在MAC层中，R-UE接收至少一个HARQ否定确认，R-UE在与Tx UE初始使用的相同资源上转发重新编码的第二数据包；在这种情况下，R-UE仅仅涉及简单调度，一般不用需要考虑信道条件、数据缓冲状态、优先级控制，调度器只需要简单判断是否应该进行合作重传。
  8. 根据权利要求7所述的侧链路重传方法，其特征在于，所述UE包括主R-UE和/或辅R-UE，其中，
    所述主R-UE，由网络或组成员指定，主R-UE可以是单个R-UE或多个R-UE，其必须参与多UE协作中继，除非它没有正确地接收到Tx UE发送的第一数据包；
    所述辅R-UE，自愿参与多UE协作中继，在大多数情况下，辅R-UE能够从邻近的Tx UE接收数据包，然后转发给邻近的Rx UE。
  9. 根据权利要求1所述的侧链路重传方法，其特征在于，所述资源包括主中继资源(Primary Relay Resources)和辅中继资源(Secondary Relay Resources)，其中，
    ——所述主中继资源，由SCI在第一数据包的物理侧链路控制信道PSCCH上指示，并与第一数据包相耦合；在多数情况下，它与Tx UE传输第一数据包的资源相同；所有的R-UE使用相同的主中继资源完成多UE协作中继。
    ——所述辅中继资源，由SCI在第二数据包的物理侧链路控制信道PSCCH上指示；即，R-UE可以自主地选择用于转发第二数据包的资源，并且不同的R-UE可以使用不同的资源。
  10. 根据权利要求1所述的侧链路重传方法，其特征在于，成功检测到两个以上的第一数据包的Rx UE可以对两个以上的第一数据包进行XoR(eXclusive OR)编码，从而提高侧链路传输效率。
  11. 根据权利要求1所述的侧链路重传方法，其特征在于，划分出N个区域，N为自然数；第n区域内的区域ID为Zone-ID-n，n为选自0至N-1的自然数；Zone-ID-n区域被I n个UE占用；UE之间的无线电通信范围RCR是无线电通信能达到的范围，至少从一个区域的边缘到其相邻区域的边缘的距离，而UE之间的服务质量通讯范围QCR是传输的数据包需要到达的范围，可以从一个区域的边缘到其下一个邻居区域边缘的距离；
    Zone-ID-(n-1)、Zone-ID-n和Zone-ID-(n+1)为依次相邻设置的区域，RCR是包括Zone-ID-(n-1)和Zone-ID-n的区域，或者是包括Zone-ID-n和Zone-ID-(n+1)的区域，QCR是跨越越Zone-ID-(n-1)，Zone-ID-n和Zone-ID-(n+1)的区域；
    所述方法包括：
    与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的发送设备Tx UE发送初始数据包，以及与 Zone-ID-(n-1)，Zone-ID-n，Zone-ID-(n+1)相关联的接收设备Rx UE接收初始数据包；
    在Tx UE相同区域的全部Rx UE可以成功检测到初始数据包；与Zone-ID-(n-1)和Zone-ID-(n+1)同时相邻的Zone-ID-n相关联的区域中的部分或全部Rx UE可以成功检测到初始数据包；与Zone-ID-(n-1)间隔相邻的Zone-ID-(n+1)相关联的区域中的Rx UE，或者与Zone-ID-(n+1)间隔相邻的Zone-ID-(n-1)相关联的区域中的Rx UE，至少有部分未能检测到初始数据包；
    Zone-ID-n中成功检测到初始数据包的Rx UE按照对初始数据包进行XoR编码，然后将重新编码的XoR编码数据包在与Tx UE初始使用的相同资源中同时转发/重传给初始数据包检测失败、和/或在半双工状态下工作的其它UE。
  12. 根据权利要求11所述的侧链路重传方法，其特征在于，初始数据包传输可以在时隙t中由位于拥有以下Zone-ID(类型-1区域)中的Tx UE执行，
    Zone-ID＝y 1N x+x 1,如果(x 1mod 2)＝(y 1mod 2)；
    并且可以通过位于拥有以下Zone-ID(类型-2区域)中的Rx UE在时隙t+Δ中执行基于中继的重传
    Zone-ID＝y 1N x+x 1,如果(x 1mod 2)≠(y 1mod 2)；
    其中，Δ是以时隙为单位的HARQ处理时间(Δ≥1)；N x为Zone-ID的经度，N y为Zone-ID纬度值，x和y分别为UE当前位置经度、纬度与参考坐标(0,0)之间的距离，x 1＝0,1,…,N x-1；y 1＝0,1,…,N y-1。
  13. 根据权利要求12所述的侧链路重传方法，其特征在于，与Zone-ID-(n-1)相关联的Tx UE-i n-1发送第一初始数据包
    Figure PCTCN2019105865-appb-100001
    第一数据包将被其自己区域中的所有Rx UE成功接收，同时，该第一初始数据包也被与Zone-ID-n相关联的Rx UE成功接收，但是，该第一初始数据包无法被与Zone-ID-(n+1)相关联的Rx UE接收；
    与Zone-ID-(n+1)相关联的Tx UE-i n+1发送第二初始数据包
    Figure PCTCN2019105865-appb-100002
    第二初始数据包将被其自己区域中的所有Rx UE成功接收，同时，该第二初始数据包也被与Zone-ID-n相关联的Rx UE成功接收，但是，该第二初始数据包无法被与Zone-ID-(n-1)相关联的Rx UE接收；
    R-UE-i n将XoR编码的数据包
    Figure PCTCN2019105865-appb-100003
    转发给与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的两个邻居区域中的Rx UE；
    其中，在检测过程中，与Zone-ID-(n-1)相关联的所有Rx UE是预先知道第一初始数据包
    Figure PCTCN2019105865-appb-100004
    并且通过对
    Figure PCTCN2019105865-appb-100005
    的XoR解码来检测到
    Figure PCTCN2019105865-appb-100006
    与Zone-ID-(n+1)相关联的所有Rx UE是预先知道第二初始数据包
    Figure PCTCN2019105865-appb-100007
    并且通过对
    Figure PCTCN2019105865-appb-100008
    的XoR解码来检测到
    Figure PCTCN2019105865-appb-100009
  14. 根据权利要求12所述的侧链路重传方法，其特征在于，Zone-ID-(n-1)和Zone-ID-(n+1)相关联的接收设备Rx UE按照预设策略在物理层侧链反馈信道PSFCH上，对组播中的其 它UE发送包含HARQ-NAK或HARQ-ACK的侧链反馈控制信息SFCI，HARQ-NAK触发Zone-ID-n中成功检测到初始数据包的Rx UE进行逐个重传；其中，所述预设策略包括以下任意一种方式：
    方案-1：如果初始数据包解码失败，则未能检测到初始数据包的接收设备Rx UE反馈HARQ-NAK，PSFCH资源仅与初始数据包耦合；
    方案-2：如果初始数据包解码失败，则未能检测到初始数据包的接收设备Rx UE反馈HARQ-NAK，PSFCH资源与初始数据包和反馈HARQ-NAK的接收设备Rx UE的Zone-ID耦合；
    方案-3：接收设备Rx UE反馈HARQ-NAK或HARQ-ACK，PSFCH资源与初始数据包和反馈HARQ-NAK或HARQ-ACK的接收设备Rx UE的Zone-ID耦合。
  15. 根据权利要求12所述的侧链路重传方法，其特征在于，所述资源包括：用于初始数据包传输的数据包资源DPR和用于协作中继传输的协作中继资源CRR；DPR和CRR都与Zone-ID相关联，DPR和CRR被时分多路处理(Time Division Multiplexing，TDM)，在频域中使用相同数量的资源，用L ZONE子信道表示，在时域中拥有相同或不同的资源长度，即DPR可以跨越L DPR时隙，CRR可以跨越L CRR时隙；L ZONE个SCH和L DPR时隙形成DPR的SCB块，而L ZONE个SCH和L CRR时隙形成CRR的SCB块；在DPR中，作为SCH的最小传输单元的资源表示为DPR n,t(p)，在CRR中，最小传输单元的资源表示为CRR n,t(p)；其中，n是Zone-ID，t是时域中的时隙索引，p是频域中SCH的索引，L ZONE、L SCH、L DPR和L CRR参数是由RRC配置或在系统中被预先配置。
  16. 根据权利要求15所述的侧链路重传方法，其特征在于，所述资源按照预设规则进行选择，将用于DPR的资源和用于CRR的资源相耦合，使得协作中继中涉及的所有接收设备Tx UE可以隐式地选择相同的资源而无需任何附加的控制信息；所述预设规则包括以下方式：
    规则-1：在频域中，与协作中继中涉及的Zone-ID-n相关联的CRR的SCB中的重传资源应该对应于与Zone-ID-(n-1)和Zone-ID-(n+1)相关联的DPR的SCB中的初始传输资源；在时域中，DPR的SCB和CRR的SCB彼此相邻；
    规则-2：每个Zone-ID-n中成功检测到初始数据包的Rx UE按照预设规则对XoR编码数据包进行顺序编号，根据编号的顺序依次将XoR编码数据包进行发送；
    规则-3：在每个SCB资源池的配置或预配置中，按照预设规则对CRR资源进行顺序编号，例如，资源顺序先从时隙索引的方向预先确定，然后从SCH索引方向确定，这样可以形成二维SCB资源；
    规则-4：每个Zone-ID-n中成功检测到初始数据包的Rx UE选择在其自己的SCB中配置或与配置的CRR资源，XoR编码数据包的顺序和CRR资源的顺序一对一映射。
  17. 根据权利要求1所述的侧链路重传方法，其特征在于，Tx UE通过PSCCH发送SCI及相关联的PSSCH，而Rx UE接收SCI，并且获取QCR信息；仅在QCR范围内，Tx UE根据PSSCH解码状态然后判断是否反馈ACK或NAK。
  18. 根据权利要求1所述的侧链路重传方法，其特征在于，Tx UE通过PSCCH传输SCI信息，通过PSSCH传输相关传输块，而SCI包含公共PSFCH资源索引信息；Rx UE接 收SCI及其相关数据包，并检测是否有错误；仅在Rx UE检测到所接收的数据包由错误时，在侧链路HARQ反馈被触发；依赖于HARQ选项-1或选项-2的情况下，所有Rx UE使用PSFCH资源来反馈HARQ的ACK/NAK。
  19. 根据权利要求18所述的侧链路重传方法，其特征在于，每个与Zone-ID-n相关联的PSFCH资源池中的M资源公式为
    Figure PCTCN2019105865-appb-100010
    其中，m＝1,2,…,M，n＝0,1,…,N-1，N是ZB中的区域数。
  20. 根据权利要求18所述的侧链路重传方法，其特征在于，第一个PSFCH资源被分配到Tx UE所在的中心区域，第二个PSFCH资源被分配到Tx UE为中心的第一层区域，以此类推，第k个PSFCH资源被分配到Tx UE为中心的第(k-1)层区域，直到QCR内的最后一个区域层为止，k为1至总层数之间的自然数。
  21. 根据权利要求20所述的侧链路重传方法，其特征在于，每个Rx UE从其中一个中心Tx UE检测到PSCCH上的SCI，然后基于该中心Tx UE的Zone-ID和Rx UE的Zone-ID确定Rx UE位于其中的哪个区域层。
  22. 根据权利要求21所述的侧链路重传方法，其特征在于，每个区域层中的PSFCH资源数量被单独(预)配置，其规则为M 0≤M 1≤…≤M K-1，其中K是QCR内的区域层数，也是(预)配置的；PSFCH资源可以由索引m统一指示，其中，m k＝m mod M k，m＝1,2,…,M K-1,m k＝1,2,…,M k。
  23. 根据权利要求21所述的侧链路重传方法，其特征在于，通过位置坐标由Rx UE获取Tx UE的区域位置，Rx UE能够计算出Tx UE和Rx UE之间的距离，从而推导出Rx UE属于哪个区域层。
  24. 根据权利要求19所述的侧链路重传方法，其特征在于，位于Zone-ID-n的Tx UE通过PSCCH及其关联的PSSCH执行初始数据包传输，而位于其他区域的Rx UE进行相应的接收；解码错误的Rx UE通过被激活的PSFCH发送相应的SFCI(NAK)给Tx UE；Tx UE根据推导出的AoD将数据包用波束成形(Beamforming)发送到解码错误的Rx UE。
  25. 根据权利要求24所述的侧链路重传方法，其特征在于，Tx UE发送的SCI其中包含PSFCH资源模型索引以及PSFCH的传输时机信息；Rx UE使用PSFCH资源模型反馈SFCI给Tx UE，Tx UE对其SFCI信号检测从而识别反馈UE的HARQ信息和其Zone-ID；Tx UE通过在不同传输时机接收到的不同PSFCH资源模型逐步提高其AoD分辨率。
  26. 根据权利要求25所述的侧链路重传方法，其特征在于，Tx UE后续传输时机中用波束成形进行早期重传，其中PSCCH上发送的SCI重新指示了PSCCH和PSFCH之间发送时间差，PSFCH时机间隔，PSFCH资源模型索引；一旦与Zone-ID-x相关联的Rx UE在PSCCH上检测到SCI，它就得知先前SCI指示的信息被当前SCI覆盖。
  27. 根据权利要求25所述的侧链路重传方法，其特征在于，存在至少两个以上的PSFCH资源模型，通过检测第一PSFCH资源模型中的SFCI，Tx UE能够初步区分AoD，识别是否是单个方向上的Rx UE需要重传，从而判断是否需要使用波束成形机制的重传。
  28. 根据权利要求27所述的侧链路重传方法，其特征在于，基资源(Base Resource)被定义为用于PSFCH的基础资源，被反馈UE使用发送其HARQ NAK；PSFCH基资源可以被定义为频域，时域或码域资源；PSFCH中的基资源的数量为n bs，其中，n bs＝2 b，b是整数，b≥1；PSFCH资源模型和资源模型集依赖于ZB大小以及基资源，并由基资源组合而成；被组合成的每个PSFCH资源模型拥有独立的索引；PSFCH资源模型由RRC配置或予配置。
  29. 根据权利要求24所述的侧链路重传方法，其特征在于，Rx UE根据他们的相对位置坐标计算出Tx UE和Rx UE之间的AoA(Angle of Arrival)，由此Rx UE选择以Tx UE为中心的PSFCH资源进行HARQ反馈。
  30. 根据权利要求29所述的侧链路重传方法，其特征在于，AoA被有限比特量化，其比特量化是基于(预)配置方式，独立的PSFCH资源被分配给每个量化的AoA,拥有独立的索引；与每个组播传输相关联的PSFCH资源集仅与Tx UE和量化的AoA相关；一旦Tx UE接收到相应的PSFCH，它就可以隐式地计算出AoD(Angle of Departure)并实现基于波束成形的重传。
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