Systems and methods for performing HARQ feedback for unlicensed sidelink communications
According to an embodiment of the present disclosure, a system and a method may include receiving, by a first user equipment (UE), configuration information for physical sidelink feedback channel (PSFCH) resources; performing, by the first UE in response to the receiving, a first listen-before-talk (LBT) sensing for a first PSFCH resource of the PSFCH resources; and determining that the first LBT sensing failed and in response, transmitting a signal over a second PSFCH resource of the PSFCH resources.
1 . A method, comprising:
receiving, by a first user equipment (UE), configuration information for physical sidelink feedback channel (PSFCH) resources comprising a first PSFCH resource and a second PSFCH resource;
performing, by the first UE in response to the receiving, a check to identify if a first channel occupancy time (COT) has been shared by a second UE that covers the first PSFCH resource and to identify if a first listen-before-talk (LBT) sensing has been successful for the first PSFCH resource of the PSFCH resources;
determining that the first LBT sensing failed and a first COT was not shared, and performing a check to identify whether a second COT has been shared by the second UE that covers the second PSFCH resource and to identify if a second LBT sensing has been successful for the second PSFCH resource of the PSFCH resources; and
selecting the second PSFCH resource of the PSFCH resources and transmitting a signal over the second PSFCH resource, in response to determining that the second COT was shared or the second LBT sensing was successful.
2 . The method of claim 1 , further comprising determining, by the first UE, that the second UE is to receive the signal from the first UE.
3 . The method of claim 2 , wherein the signal is a hybrid automatic repeat request (HARQ) feedback signal.
4 . The method of claim 2 , wherein the first PSFCH resource and the second PSFCH resource are mapped to a single physical sidelink shared data channel (PSSCH).
5 . The method of claim 4 , further comprising determining that one or more short control exemptions are available, and
wherein the transmitting the signal over the second PSFCH resource is performed in response to the determining that one or more short control exemptions are available, without performing a second LBT sensing on the second PSFCH resource.
6 . The method of claim 2 , further comprising, in response to the determining that the LBT sensing for the first PSFCH resource failed, performing, by the first UE, a second LBT sensing for the second PSFCH resource.
7 . The method of claim 6 , wherein the second LBT sensing is performed before transmitting the signal over the second PSFCH resource.
8 . The method of claim 6 , wherein the transmitting the signal over the second PSFCH resource is performed in response to the determining that the LBT sensing for the second PSFCH resource succeeded.
9 . The method of claim 1 , wherein the transmitting the signal is performed during a sidelink communication over unlicensed frequency bands.
10 . The method of claim 2 , wherein the second PSFCH resource is within the second COT shared by the first UE and the second UE, the method further comprising transmitting, by the first UE, the signal on the shared second COT.
11 . The method of claim 10 , wherein the transmitting the signal over the second PSFCH resource is performed without performing the second LBT sensing successively on the second PSFCH resource.
12 . The method of claim 1 , further comprising, in response to the determining that the first LBT sensing failed, transmitting the signal with-sidelink control information (SCI).
13 . A system comprising:
a first user equipment (UE), the UE comprising:
a radio; and
a processing circuit, wherein the processing circuit is configured to:
receive configuration information for physical sidelink feedback channel (PSFCH) resources comprising a first PSFCH resource and a second PSFCH resource;
perform, in response to receiving the configuration information, a check to identify if a first channel occupancy time (COT) has been shared by a second UE that covers the first PSFCH resource and to identify if a first listen-before-talk (LBT) sensing has been successful for the first PSFCH resource of the PSFCH resources;
determine that the first LBT sensing failed and a first COT was not shared, and perform a check to identify whether a second COT has been shared by the second UE that covers the second PSFCH resource and to identify if a second LBT sensing has been successful for the second PSFCH resource of the PSFCH resources; and
select the second PSFCH resource of the PSFCH resources and transmit a signal over the second PSFCH resource, in response to determining that the second COT was shared or the second LBT sensing was successful.
14 . The system of claim 13 , wherein the processing circuit is further configured to determine that the second UE is to receive the signal from the first UE.
15 . The system of claim 13 , wherein the signal is a hybrid automatic repeat request (HARQ) feedback signal.
16 . The system of claim 13 , wherein the first PSFCH resource and the second PSFCH resource are mapped to a single physical sidelink shared data channel (PSSCH).
17 . The system of claim 16 , wherein the processing circuit is further configured to determine that one or more short control exemptions are available, and
wherein the transmitting the signal over the second PSFCH resource is performed in response to the determining that one or more short control exemptions are available, without performing a second LBT sensing on the second PSFCH resource.
18 . The system of claim 13 , wherein in response to the determination that the LBT sensing for the first PSFCH resource failed, the processing circuit is further configured to perform a second LBT sensing for the second PSFCH resource.
19 . The system of claim 18 , wherein processing circuit is further configured to perform the second LBT sensing before transmitting the signal over the second PSFCH resource.
20 . The system of claim 18 , wherein in response to the determination that the LBT sensing for the second PSFCH resource succeeded, the processing circuit is further configured to transmit the signal over the second PSFCH resource.
21 . The system of claim 13 , wherein the transmitting the signal is performed during a sidelink communication over unlicensed frequency bands.
22 . The system of claim 14 , wherein the second PSFCH resource is within the second COT shared by the first UE and the second UE, and the processing circuit is further configured to transmit the signal on the shared second COT.
23 . The system of claim 17 , wherein the transmitting of the signal over the second PSFCH resource is performed without performing the second LBT sensing successively on the second PSFCH resource.
24 . The system of claim 13 , wherein in response to the determination that the first LBT sensing failed, the processing circuit is further configured to transmit the signal with sidelink control information (SCI).