Harq in sidelink in coverage and out-of-coverage scenarios

Abstract

A wireless communication system includes a plurality of transceivers. The plurality of transceivers include at least a first transceiver and a second transceiver. The first transceiver and the second transceiver are configured for a sidelink communication with each other. The wireless communication system supports a retransmission protocol for the sidelink. The retransmission protocol enables the first transceiver to perform a retransmission for a data packet, responsive to an explicit or an implicit feedback from the second transceiver, which receives one or more data packets from the first transceiver, in case of a non-successful transmission of the data packet over the sidelink.

1 . A wireless communication system, comprising:
 a plurality of transceivers, the plurality of transceivers including at least a first transceiver and a second transceiver, the first transceiver and the second transceiver configured for a sidelink communication with each other,   wherein the wireless communication system is configured to support a retransmission protocol for the sidelink, the retransmission protocol enabling the first transceiver to perform a retransmission for a data packet, responsive to an explicit or an implicit feedback from the second transceiver, which receives one or more data packets from the first transceiver, in case of a non-successful transmission of the data packet over the sidelink.   
     
     
         2 . The wireless communication system of  claim 1 , wherein
 the plurality of transceivers includes at least a third transceiver, and   the first transceiver is configured for a unicast transmission to the second transceiver over the sidelink, or for a multicast transmission to the second and third transceivers over the sidelinks.   
     
     
         3 . The wireless communication system of  claim 1 , comprising
 at least one base station, gNB,   wherein the transceivers comprise a plurality of user equipments, UEs, the plurality of UEs including at least a first UE and a second UE, the first and second UEs configured for a sidelink communication with each other, and   wherein the gNB is configured to control the sidelink communication between the first and second UEs.   
     
     
         4 . The wireless communication system of  claim 3 , wherein the DCI indicates on or more of the following:
 in case of a unicast transmission to the second UE over the sidelink, an identifier, ID, of the second UE, like a Radio Network Temporary Identifier, RNTI, explicitly or implicitly by CRC scrambling   in case of a multicast transmission to a group of UEs over the sidelinks, a group destination ID, explicitly or implicitly by CRC scrambling   the HARQ process ID to be used together with a sidelink resource allocation.   
     
     
         5 . The wireless communication system of  claim 1 , wherein
 the transceivers comprise a plurality of user equipments, UEs, the plurality of user UEs including at least a first UE and a second UE, the first and second UEs configured for a sidelink communication with each other and to schedule resources for the sidelink communication autonomously.   
     
     
         6 . The wireless communication system of  claim 5 , wherein
 the first UE is configured to schedule an initial transmission over the sidelink to the second UE, the second UE is configured to transmit to the first UE a non-acknowledgement message, NACK, in case of a non-successful transmission of the data packet over the sidelink, and following the initial transmission, the first UE is configured to continue with the retransmissions until an acknowledgement message, ACK, is received from the first UE or a maximum number of retransmissions is reached.   
     
     
         7 . The wireless communication system of  claim 5 , wherein the second UE is configured to transmit to the first UE the NACK explicitly or implicitly, the implicit NACK comprises not sending the ACK within a defined time period or at a certain time following the transmission or retransmission. 
     
     
         8 . The wireless communication system of  claim 1 , wherein
 a frequency resource and timing of the initial transmission uniquely maps to a PSCCH or physical sidelink shared channel (PSSCH) region for providing the feedback, and/or   the feedback is provided with a SCI format including the HARQ feedback and the first UE ID, to allow the first UE to uniquely identify the feedback based on the first UE's ID and the feedback transmission timing.   
     
     
         9 . The wireless communication system of  claim 1 , wherein the first UE is configured to automatically retransmit a transport block, TB, according to a preconfigured or default RV order on the same frequency resources or a fixed or preconfigured hopping pattern according to a sidelink HARQ timeline, the sidelink HARQ timeline indicating a time of sending the feedback, and a time of sending the retransmission. 
     
     
         10 . The wireless communication system of  claim 9 , wherein the sidelink HARQ interval is different from a HARQ timeline, RTT, used of UL and DL communications, the sidelink HARQ interval being either fixed or semi-statically preconfigured, e.g., by an explicit RRC signaling for the sidelink. 
     
     
         11 . The wireless communication system of  claim 9 , wherein different sidelink HARQ timelines are signaled for specific transmissions, e.g. URLLC. 
     
     
         12 . The wireless communication system of  claim 9 , wherein a default sidelink HARQ timeline is configured or fixed for out-of-coverage and/or default operations. 
     
     
         13 . The wireless communication system of  claim 1 , wherein, in case of autonomous UEs which are configured to perform sensing to determine an available transmission location, the first UE is configured to extrapolate, using HARQ RTT, the HARQ RTT selected from a plurality of pre-configured HARQ RTTs, wherein the HARQ retransmission process may assume that the maximum number of retransmissions is used. 
     
     
         14 . A wireless communication system, comprising:
 a plurality of transceivers, the plurality of transceivers including at least a first transceiver and a second transceiver, the first transceiver and the second transceiver configured for a sidelink communication with each other,   wherein the wireless communication system is configured to support channel quality indicator, CQI, reporting based on past SL transmissions and/or channel state information reference symbols, like CSI-RS.   
     
     
         15 . The wireless communication system of  claim 14 , wherein
 the gNB is configured to indicate, via a control channel together with a SL grant, to the first UE to transmit a CSI-RS on the whole or on a subset of the sidelink resources in a part of the duration of an assigned timeslot, and   the first UE is configured to transmit the data and a CSI-RS, and to indicate the CSI-RS transmission in the corresponding SCI.   
     
     
         16 . The wireless communication system of  claim 1 , wherein the second UE is configured to include a CQI report in the HARQ feedback reporting to the gNB based on reference signals included in the associated transmission, the CQI report being transmitted on the PUCCH together with information of the first and second UEs. 
     
     
         17 . The wireless communication system of  claim 16 , wherein the CQI report is activated, e.g., by RRC signaling and/or by the CSI-RS transmission indicated in the corresponding SCI. 
     
     
         18 . The wireless communication system of  claim 16 , wherein the first UE is configured to use a dedicated timeslot or resource to transmit a CSI-RS on the sidelink, the dedicated timeslot or resource being granted by the gNB or being sensed autonomously. 
     
     
         19 . The wireless communication system of  claim 1 , wherein the wireless communication system provides buffer status report, BSR, indicating an amount of data in a buffer per destination per logical channel group. 
     
     
         20 . A transceiver, wherein
 the transceiver is configured to communicate in a wireless communication system with one or more further transceivers using a sidelink,   receive one or more data packets from the further transceiver over the sidelink, and support a retransmission protocol for the sidelink, the retransmission protocol enabling the further transceiver to perform a retransmission for a data packet, responsive to an explicit or an implicit feedback from the transceiver, in case of a non-successful transmission of the data packet over the sidelink.