HANDLING LBT FAILURE IN SIDELINK COMMUNICATION
Various aspects of the present disclosure relate to generating a hybrid automatic repeat request (HARQ) feedback based on a data transmission received from a sidelink (SL) transmitter UE (UE-t) and performing a Clear Channel Assessment (CCA). Aspects of the present disclosure may further relate to incrementing a counter based on a negative CCA result and transmitting a message to the SL UE-t based at least in part on the counter reaching a predefined value, the message comprising CCA failure information for a Resource Block (RB) set.
1 . A user equipment (UE) for wireless communication, comprising:
at least one memory; and
at least one processor coupled with the at least one memory and configured to cause the UE to:
generate a hybrid automatic repeat request (HARQ) feedback based on a data transmission received from a sidelink (SL) transmitter UE (UE-t);
perform a Clear Channel Assessment (CCA);
increment a counter based on a negative CCA result; and
transmit a message to the SL UE-t based at least in part on the counter reaching a predefined value, the message comprising CCA failure information for a Resource Block (RB) set.
2 . The UE of claim 1 , wherein the at least one processor is configured to cause the UE to:
perform a decoding procedure on the data transmission; and
transmit the HARQ feedback based on a positive CCA result, wherein the HARQ feedback indicates a result of the decoding procedure.
3 . The UE of claim 1 , wherein the RB set comprises a first RB set, and wherein the at least one processor is configured to cause the UE to:
receive the data transmission from the SL UE-t on the first RB set;
perform the CCA on the first RB set; and
transmit the message on a second RB set different than the first RB set.
4 . The UE of claim 1 , wherein the CCA failure information indicates a continuous listen-before-talk (C-LBT) failure condition of the RB set.
5 . The UE of claim 1 , wherein the at least one processor is configured to cause the UE to, and.
6 . The UE of claim 1 , wherein the at least one processor is configured to cause the UE to initiate a timer in response to the negative CCA result, and wherein transmitting the message is further based at least in part on the counter reaching the predefined value prior to expiry of the timer.
7 . The UE of claim 1 , wherein the message comprises:
an identification of the RB set;
a Resource Pool (RP) identification associated with the RB set;
a recommended RB Set identification;
a recommended RP identification;
a HARQ process identifier (HPID) for each transport block (TB) associated with a failed decoding;
a HPID for each TB associated with a successful decoding and for which an individual feedback was unable to be transmitted due to the negative CCA result;
an aggregated HARQ Feedback associated with each TB for which an individual feedback was unable to be transmitted due to the negative CCA result;
a list of sequence numbers (SNs) corresponding to each TB associated with a failed decoding;
a list of SNs corresponding to each TB associated with a successful decoding and for which an individual feedback was unable to be transmitted due to the negative CCA result;
a triggering condition flag or cause value;
or a combination thereof.
8 . The UE of claim 1 , wherein the counter is specific to the RB set, and wherein to increment the counter, the at least one processor is configured to cause the UE to increment the counter in response to a negative CCA result specific to the RB set.
9 . The UE of claim 1 , wherein the counter is specific to a source-destination pair, and wherein to increment the counter, the at least one processor is configured to cause the UE to increment the counter in response to a negative CCA result specific to the source-destination pair.
10 . A processor for wireless communication, comprising:
at least one controller coupled with at least one memory and configured to cause the processor to:
generate a hybrid automatic repeat request (HARQ) feedback based on a data transmission received from a sidelink (SL) transmitter user equipment (UE-t);
perform a Clear Channel Assessment (CCA);
increment a counter based on a negative CCA result; and
transmit a message to the SL UE-t based at least in part on the counter reaching a predefined value, the message comprising CCA failure information for a Resource Block (RB) set.
11 . A user equipment (UE) for wireless communication, comprising:
at least one memory; and
at least one processor coupled with the at least one memory and configured to cause the UE to:
transmit, to a sidelink (SL) receiver UE (UE-r), a SL data transmission on a first resource block (RB) set;
receive, from the SL UE-r, a message on a second RB set, the message comprising Clear Channel Assessment (CCA) failure information for the first RB set; and
perform a retransmission of the SL data transmission based on the CCA failure information.
12 . The UE of claim 11 , wherein to perform the retransmission, the at least one processor is configured to cause the UE to:
retransmit the SL data transmission on the first RB set, and
indicate that no hybrid automatic repeat request (HARQ) feedback is to be sent for the retransmission.
13 . The UE of claim 11 , wherein to perform the retransmission, the at least one processor is configured to cause the UE to:
perform a transmission repetition of the SL data transmission on the first RB set, and indicate that no hybrid automatic repeat request (HARQ) feedback is to be sent for the transmission repetition.
14 . The UE of claim 11 , wherein to perform the retransmission, the at least one processor is configured to cause the UE to retransmit the SL data transmission on a new RB set different than the first RB set, wherein the new RB set corresponds to the second RB set or a respective RB set selected using a resource selection procedure.
15 . The UE of claim 11 , wherein to perform the retransmission, the at least one processor is configured to cause the UE to perform a transmission repetition of the SL data transmission on a new RB set different than the first RB set, wherein the new RB set corresponds to the second RB set or a respective RB set selected using a resource selection procedure.
16 . The UE of claim 11 , wherein the at least one processor is configured to cause the UE to perform one or more new transmissions on a new RB set different than the first RB set, wherein the new RB set corresponds to the second RB set or a respective RB set selected using a resource selection procedure.
17 . The UE of claim 11 , wherein the at least one processor is further configured to cause the UE to transmit SL Control Information (SCI) with the SL data transmission, wherein the SCI indicates a sequence number (SN) corresponding to each transport block (TB) associated with the SL data transmission.
18 . The UE of claim 11 , wherein the at least one processor is further configured to cause the UE to:
receive, from the SL UE-r, an update indicating that the first RB set is available for use; and
perform one or more new transmissions on the first RB set based on the update.
19 . The UE of claim 11 , wherein the at least one processor is configured to cause the UE to:
initiate a timer in response to receiving the message on the second RB set; and
perform one or more new transmissions on the first RB set in response to expiry of the timer.
20 . A processor for wireless communication, comprising:
at least one controller coupled with at least one memory and configured to cause the processor to:
transmit, to a sidelink (SL) receiver UE (UE-r), a SL data transmission on a first resource block (RB) set;
receive, from the SL UE-r, a message on a second RB set, the message comprising Clear Channel Assessment (CCA) failure information for the first RB set; and
perform a retransmission of the SL data transmission based on the CCA failure information.