Mechanisms for RLF detection of sidelink on unlicensed spectrum
Apparatus and methods are provided RLF detection for SL-U transceiving. In one novel aspect, HARQ-based RLF detection and/or LBT-based RLF detection is performed for SL-U RLF. HARQ based SL-U RLF procedure increases DTX for each PSSCH or PSCCH and disregards detected DTX on PSFCH or increases DTX for each PSFCH absence. In one embodiment, a DTX threshold value is modified. In one embodiment, the LBT based RLF procedure detects and reports an LBT failure for an RB set by the PHY layer; determines a consistent LBT (C-LBT) for the RB set based on a C-LBT threshold at the MAC layer and determines an RLF when all configured RB sets for the SL connection is determined to be C-LBT. In another novel aspect, multiple PSFCH occasions are configured for one PSSCH/PSCCH at a consecutive symbol level, a non-consecutive symbol level, a consecutive slot level or a non-consecutive slot level.
1 . A method for a user equipment (UE), comprising:
establishing, by the UE, sidelink (SL) connections on unlicensed frequency bands (SL-U) for an SL-U transceiving on one physical sidelink control channel (PSCCH)/physical sidelink shared channel (PSSCH) in a wireless network, wherein the SL transceiving is configured with one or more resource block (RB) sets of an SL bandwidth part (BWP);
configuring one or more candidate physical sidelink feedback channel (PSFCH) occasions to be associated with the one PSCCH/PSSCH;
determining an SL radio link failure (RLF) for the SL connections based on at least one detection procedures comprising a hybrid automatic repeat request (HARQ) based SL-U RLF detection procedure and a listen-before-talk (LBT) failure based RLF detection procedure, the HARQ based SL-U RLF detection procedure increases DTX by 1 for each PSCCH/PSSCH transmission when all associated candidate PSFCH receptions are absent on candidate PSFCH reception occasions, and wherein the LBT based RLF procedure comprising: detecting, by a PHY layer of the UE, an LBT failure for an RB set; reporting the LBT failure of the RB set to a MAC layer of the UE; determining a consistent LBT (C-LBT) for the RB set based on a C-LBT threshold; and determining an RLF for the SL connections when all configured RB sets for the SL connections are determined to be C-LBT.
2 . The method of claim 1 , wherein a DTX threshold value is modified, and wherein the DTX threshold value is a maximum number of consecutive DTX before triggering the SL RLF of a SL connection.
3 . The method of claim 2 , wherein the DTX threshold value is modified through pre-configuration or dynamic indication.
4 . The method of claim 3 , wherein the DTX threshold is modified based on one or more factors comprising network loading, network density, channel busy ratio, and traffic quality of service (QoS).
5 . The method of claim 3 , wherein the pre-configuration or dynamic indication of the DTX threshold value is signaled through one or more signaling comprising system information block (SIB), PC5 radio resource control (RRC), PC-5 MAC control element (CE), downlink control indicator (DCI), and sidelink control indicator (SCI).
6 . The method of claim 1 , wherein a cause of the determined RLF is set to be LBT failure.
7 . The method of claim 1 , wherein the C-LBT threshold is preconfigured or dynamically indicated.
8 . The method of claim 7 , wherein the C-LBT threshold is based on one or more factors comprising network loading, network density, channel busy ratio, and traffic quality of service (QoS), UE's supervising role, and UE member in a UE group.
9 . The method of claim 1 , wherein the one or more PSFCH occasions are consecutive.
10 . The method of claim 1 , wherein the one or more PSFCH occasions are non-consecutive.
11 . The method of claim 1 , wherein at least one PSFCH occasion of the one or more PSFCH occasions is configured at symbol level.
12 . The method of claim 1 , wherein at least one PSFCH occasion of the one or more PSFCH occasions is configured at slot level.
13 . The method of claim 1 , wherein the one or more PSFCH occasions are preconfigured or dynamically indicated.
14 . A user equipment (UE), comprising:
a transceiver that transmits and receives radio frequency (RF) signal in a wireless network;
a memory; and
a processor coupled to the memory, the processor configured to
establish an SL connection on unlicensed frequency bands (SL-U) for an SL-U transceiving on one physical sidelink control channel (PSCCH)/physical sidelink shared channel (PSSCH) in a wireless network, wherein the SL transceiving is configured with one or more resource block (RB) sets of an SL bandwidth part (BWP);
configure one or more candidate physical sidelink feedback channel (PSFCH) occasions to be associated with the PSCCH/PSSCH;
determine an SL radio link failure (RLF) for the SL connections based on at least one detection procedures comprising a hybrid automatic repeat request (HARQ) based SL-U RLF detection procedure and a listen-before-talk (LBT) failure based RLF detection procedure, the HARQ based SL-U RLF detection procedure increases DTX by 1 for each PSCCH/PSSCH transmission when all associated candidate PSFCH receptions are absent on candidate PSFCH reception occasions, and wherein the LBT based RLF procedure comprising: detecting, by a PHY layer of the UE, an LBT failure for an RB set; reporting the LBT failure of the RB set to a MAC layer of the UE; determining a consistent LBT (C-LBT) for the RB set based on a C-LBT threshold; and determining an RLF for the SL connections when all configured RB sets for the SL connections are determined to be C-LBT.