WO2024059966A1

WO2024059966A1 - Mechanisms for rlf detection of sidelink on unlicensed spectrum

Info

Publication number: WO2024059966A1
Application number: PCT/CN2022/119584
Authority: WO
Inventors: Junqiang CHENG; Jing-Wei Chen; Tao Chen
Original assignee: Mediatek Singapore Pte. Ltd.
Priority date: 2022-09-19
Filing date: 2022-09-19
Publication date: 2024-03-28
Also published as: CN117729579A

Abstract

This disclosure describes enhanced mechanisms for RLF detection of SL-U. Specifically, the LBT channel access failure based RLF detection is supported for SL-U. Layer 1 notifies higher layer about the channel access failure if a UE fails to access the channel (s) prior to any, and/or one, and/or multiple, and/or partial, and/or all intended/granted/scheduled/overbooked resource (s) as (pre-) configuration. The value of the maximum count/number of LBT failure instance (s), and/or the size of the LBT failure detection timer before triggering the consistent LBT channel access failures can be (pre-) configured and/or dynamically indicated based on, such as the network loading, and/or network density, and/or channel busy ratio, and/or traffic QoS, and/or the role of the UE (e.g., supervising UE or supervised UE), and/or the UE member in the group, etc. Additionally, HARQ-based RLF detection with some enhancements is supported for SL-U. Multiple (candidate) PSFCH reception occasion (s) can be (pre-) configured and/or indicated. The number of consecutive DTX should be increased by 1 if PSFCH reception (s) is (are) absent on any, and/or one, and/or multiple, and/or partial, and/or all (candidate) PSFCH reception occasion (s) associated to the PSSCH transmission as (pre-) configuration. The value of the maximum number of consecutive DTX before triggering the RLF, and/or the number of the (candidate) PSFCH reception occasion associated with one PSSCH can be (pre-) configured and/or indicated based on network loading, and/or network density, and/or channel busy ratio, and/or traffic QoS. etc.

Description

MECHANISMS FOR RLF DETECTION OF SIDELINK ON UNLICENSED SPECTRUM

FIELD

The invention discussed below relates generally to wireless communication systems, and more particularly, to mechanisms for RLF detection of SL on unlicensed spectrum.

BACKGROUND

For Rel-16/Rel-17 sidelink (SL) , the radio link failure (RLF) shall be detected with one of the following triggers: 1) the maximum number of retransmissions for a specific destination has been reached; or 2) T400 expiry for a specific destination; or 3) the maximum number of consecutive HARQ DTX for a specific destination has been reached; or 4) the integrity check failure is indicated from SL PDCP entity. For SL transmitted on unlicensed spectrum (SL-U) , the HARQ feedback (i.e., PSFCH) may be blocked due the failure of LBT channel access, which further has the potential to incorrectly trigger HARQ-based RLF detection. Besides, the results of LBT channel access can also reflect the quality of radio link, which thus is regarded as one of the RLF triggers in legacy NR-U and should be taken into account for SL-U RLF detection. Therefore, the mechanisms for RLF detection of SL-U need some enhancements with the considerations of potential LBT channel access failure to support a stable operation of SL-U.

SUMMARY

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

Various aspects of the present disclosure relate to the mechanisms for RLF detection of SL-U. Specifically, in addition to the RLF triggers for Rel-16/Rel-17 SL, the LBT channel access failure based RLF detection can be introduced for SL-U. For example, if a UE fails to access the channel (s) prior to any, and/or one, and/or multiple, and/or partial, and/or all intended/granted/scheduled/overbooked resource (s) , Layer 1 shall notify higher layers about the LBT channel access failure. Additionally, the RLF should be declared due to constant LBT channel access failures. The maximum count/number of LBT failure instance (s) , and/or the size of the LBT failure detection timer before triggering the consistent LBT channel access failures can be (pre-) configured and/or dynamically indicated based on, such as the network loading, and/or network density, and/or channel busy ratio, and/or traffic QoS, and/or the role of the UE (e.g., supervising/anchor/cluster-header UE or supervised/client/cluster-member UE) , and/or RLF detection frequency, etc.

In another aspect of the disclosure, considering that HARQ DTX caused by LBT failure may incorrectly trigger the HARQ-based RLF, some enhanced mechanisms for HARQ-based RLF detection are proposed in this disclosure. For example, multiple (consecutive) PSFCH (i.e., HARQ) reception occasions, and/or PSFCH reception occasion window associated with one PSSCH can be (pre-) configured and/or dynamically indicated (by the COT initiator) . The UE can be (pre-) configured that increment the number of consecutive DTX by 1 if PSFCH reception (s) is (are) absent on any, and/or one, and/or multiple, and/or partial, and/or all (candidate) PSFCH reception occasion (s) associated to the PSSCH transmission. Additionally, more and/or larger values of the maximum number of consecutive DTX before triggering SL-U RLF can be (pre-) configured and/or dynamically indicated based on, such as the network loading, and/or network density, and/or channel busy ratio, and/or traffic QoS, and/or RLF detection ratio, etc. The (pre-) configuration and/or indication can be signaled via SIB and/or (PC5-) RRC, and/or (PC5) -MAC CE, and/or DCI, and/or SCI.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed figures set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary diagram of the present enhanced mechanism for HARQ-based RLF detection of SL on unlicensed spectrum.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements” ) . These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

This invention is motivated by, but no limited to, a scenario where SL operated on unlicensed spectrum. In such scenario, the failure of LBT channel access may have impact on legacy RLF triggering for SL. Specifically, considering the LBT channel access results can be regarded as an indicator of the radio link quality, LBT channel access failure based RLF detection is supported for legacy NR-U. Therefore, in addition to the legacy RLF triggers for Rel-16/Rel-17 SL, LBT channel access failure based RLF detection is considered in this disclosure. Additionally, the LBT failure may also block the transmission of HAQR, which further results the absent of PSFCH reception (s) , and thus may incorrectly trigger the HARQ-based RLF detection. Therefore, some enhancements for legacy HARQ-based RLF detection need to be further considered.

In this disclosure, LBT channel access failure based RLF detection is introduced for SL-U. For example, if a UE fails to access the channel (s) prior to an, and/or multiple intended transmission (s) , Layer 1 notifies higher layers about the LBT channel access failure. Alternatively, when lower layer performs an LBT procedure before a and/or multiple transmission (s) and the transmission (s) is (are) not performed, an LBT failure indication shall be sent to the MAC entity from lower layers. For the case that additional and/or multiple resources are allocated/scheduled/overbooked for one (TB) transmission, and/or for the case that additional and/or multiple PSFCH reception occasions associated with PSSCH transmission are (pre-) configured and/or indicated, and/or for the case that additional and/or multiple candidate S-SSB occasions are (pre-) configured and/or indicated, Layer 1 can be (pre-) configured to report LBT channel access failure to higher layers if the UE fails to access the channel (s) prior to any, and/or one, and/or multiple, and/or partial, and/or all intended resource (s) /occasion (s) .

Additionally, the RLF shall be declared by the UE if consistent LBT failures occurred, and the cause of the RLF can be set as LBT failure as (pre-) configuration. Specifically, RRC can configure parameter (s) in the procedures of consistent LBT failures indication. For example, the RRC parameters to indicate the maximum count/number of LBT failure instance (e.g., lbt-FailureInstanceMaxCount) , and/or the detection timer of LBT failure (e.g., lbt-FailureDetectionTimer) can be (pre-) configured for the consistent LBT failure detection. Besides, a counter for LBT failure indication can be used for the consistent LBT failure detection procedure (e.g., LBT COUNTER) .

Additionally, the consistent LBT failure can be triggered based on the relation between LBT COUNTER and the parameters of lbt-FailureInstanceMaxCount and lbt-FailureDetectionTimer. For example, if LBT failure indication has been received from lower layers: start or restart the lbt-FailureDetectionTimer and increment LBT COUNTER by 1. Then if LBT COUNTER >= lbt-FailureInstanceMaxCount: trigger consistent LBT failure. If all triggered consistent LBT failure are cancelled; or if the lbt-FailureDetectionTimer expires; or if lbt-FailureDetectionTimer or lbt-FailureInstanceMaxCount is reconfigured by upper layer: set LBT COUNTER to 0.

Additionally, the value/size of the maximum count/number of LBT failure instance, and/or the detection timer of LBT failure can be (pre-) configured and/or dynamically indicated based on the other impact factors. For example, the factors can be (pre-) configured to include network loading, and/or network density, and/or channel busy ratio, and/or traffic QoS, and/or the role of the UE (e.g., supervising/anchor UE, or supervised/client UE) , and/or the purpose of the COT (e.g., used by the COT initiator, or shared to other UEs) , and/or the UE member in the group, and/or within or out of COT statue, and/or RLF detection frequency/ratio, etc. A bitmap, and/or a table, and/or a scaling factor can be (pre-) configured and/or indicated to reflect the relation between the value/size of the maximum count/number of LBT failure instance, and/or the LBT failure detection timer with the impact factors.

Additionally, based on the consistent LBT failure indication frequency/times/ratio, and/or the LBT based RLF detection frequency/times/ratio, some RLF recovery mechanisms (e.g., LBT based RLF parameters, and/or enhanced resource selection mechanisms) can be implemented as (pre-) configuration. For example, larger maximum count of LBT failure instance, and/or larger detection timer of LBT failure can be (pre-) configured and/or dynamically indicated if the LBT based RLF detection ratio (in a duration/period) exceeds threshold (s) as (pre-) configuration. Besides, the enhanced resource selection mechanisms can also be (pre-) configured and/or indicated based on the RLF detection ratio. For example, more overbooked resources associated with one TB, and/or more candidate PSFCH occasions associated with one PSSCH, and/or finer channel access granularity, and/or longer LBT protection margin between LBT channel access and resource selection, etc. can be (pre-) configured and/or indicated according to the relation between the RLF frequency/times/ratio and the threshold (s) (in a duration/period) as (pre-) configured.

In another aspect of the disclosure, the HARQ-based RLF detection is supported for SL-U. Specifically, if the maximum number of consecutive HARQ DTX (for a specific destination) is reached, the UE shall declare RLF and the cause of the RLF should be identified as consecutive DTX. For SL-U, the LBT failure may block the transmission of HARQ (i.e., PSFCH) and thus may incorrectly trigger the HARQ-based RLF detection. Therefore, some enhanced mechanisms for HARQ-based RLF detection of SL-U are proposed. The values of the maximum number of consecutive DTX before triggering SL-U RLF can be (pre-) configured based on the other impact factor. For example, the impact factors can be (pre-) configured to include network loading, and/or network density, and/or channel busy ratio, and/or traffic QoS, and/or the role of the UE (e.g., supervising/anchor UE, or supervised/client UE) , and/or the purpose of the COT (e.g., used by the COT initiator, or shared to other UEs) , and/or the UE member in the group, and/or within or out of COT statue, etc. A UE can be (pre-) configured and/or indicated with a scaling factor to the legacy maximum number of consecutive DTX. For example, for lower network loading, a smaller scaling factor can be multiplied with the original maximum consecutive DTX number. For higher network loading, a larger scaling factor can be multiplied with the original maximum consecutive DTX number. Additionally, A UE can be (pre-) configured and/or indicate with a new maximum number of consecutive DTX wherein more and/or larger values are included. A bitmap and/or a table and/or a scaling factor can be (pre-) configured to indicate the relation between the value of the maximum number of consecutive DTX and the impact factor.

In this disclosure, multiple candidate PSFCH reception occasion (s) associated with one PSSCH can be (pre-) configured and/or dynamically indicated. Specifically, multiple (consecutive) PSFCH reception occasion (s) and/or a PSFCH reception occasion window within one slot and/or span multiple (consecutive) slots within COT and/or out-of-COT of the associated PSSCH can be (pre-) configured and/or dynamically indicated (by the COT initiator) . The number of candidate PSFCH reception occasion (s) and/or the length of the PSFCH reception occasion window associated with one PSSCH can be determined based on the network loading, and/or network density, and/or channel busy ratio, and/or traffic QoS, and/or within or out of COT statue, and/or RLF detection ratio (within a duration) , etc.

Additionally, the transmission on the first PSFCH occasion/symbol immediately after LBT channel access is finished can be used for AGC purpose for the following PSFCH (s) and/or a CPE operation as (pre-) configuration. After a successful PSFCH transmission, the transmission (s) on the remaining PSFCH candidate occasion (s) /symbol (s) can be (pre-) configured. For example, it can be (pre-) configure to transmit the repetition of the PSFCH, and/or a (per-) configured sequence, and/or (dummy) data on the remaining candidate PSFCH occasion (s) /symbol (s) . Alternatively, the remaining candidate PSFCH occasion (s) after a successful PSFCH transmission can be shared to the other UE (s) as (pre-) configuration.

To illustrate the above enhanced mechanism for HARQ-based RLF detection, an example is provided in Figure 1. As shown in Figure 1, four consecutive candidate PSFCH reception occasions (i.e., PSFCH OC #0 to PSFHC OC #3) are (pre-) configured and/or indicated for the associated PSSCH. All consecutive PSFCH occasions can be regarded as a PSFCH occasion window as shown in Figure 1. In this example, the LBT is finished at a position within PSFCH occasion #0, then a CPE operation or a partial AGC symbol (e.g., by the way of puncturing) can be (pre-) configured and/or indicated to occupy the remaining partial symbol of PSFCH occasion #0 and align the boundary of PSFCH occasion #1. For the case that CPE operation is (pre-) configured and/or indicated to occupy partial PSFCH occasion #0, PSFCH occasion #1 can be used for AGC symbol and PSFCH occasion #2 can be used for PSFCH transmission. Then PSFCH occasion #3 can be used for the repetition of PSFCH occasion #2. For the case that (punctured) AGC symbol is (pre-) configured and/or indicated to occupy partial PSFCH occasion #0, PSFCH occasion #1 can be used for PSFCH transmission. Then the remaining part of the candidate PSFCH occasions or PSFCH occasion window (i.e., PSFCH occasion #2 and #3) can be used for the repetition of PSFCH occasion #1. In this example, one AGC symbol is (pre-) configured and/or indicated within the PSFCH occasion window and the remaining symbols within the PSFCH occasion window are used for PSFCH transmission.

In another aspect of the disclosure, the HARQ entity shall for PSFCH reception occasion (s) associated to the PSSCH transmission: if PSFCH reception (s) is (are) absent on any, and/or one, and/or multiple, and/or partial, and/or all (candidate) PSFCH reception occasion (s) : increment the number of consecutive DTX by 1. If the number of the consecutive DTX reaches the max number of consecutive DTX: indicate HARQ-based RLF detection to RRC. Else: re-initialized the number of consecutive DTX to zero. As shown in Figure 1, one example is that when the PSFCH reception is absent on any one of the PSFCH reception occasion #0 to #3, the number of consecutive DTX shall be increased by 1. Another example is that when the PSFCH receptions are absent for all PSFCH reception occasion #0 to PSFCH reception occasion #3, the number of consecutive DTX shall be increased by 1.

For the case that the candidate PSFCH reception occasion (s) and/or PSFCH reception window (s) are (pre-) configured and/or indicated at the discontinuous symbol (s) , and/or within different slots, and/or within different COT, the AGC symbol may be (pre-) configured for each PSFCH transmission. For example, two PSFCH occasion windows, each comprised of two PSFCH occasions, are (pre-) configured within two (consecutive) slots, respectively, for one PSSCH. The first and/or partial PSFCH occasion after LBT channel access is finished within each PSFCH occasion window may be used for AGC purpose. The following PSFCH occasion (s) within each PSFCH window may be used for PSFCH transmission. In this case, the LBT before each PSFCH window may be independent.

In this disclosure, the (pre-) configuration and/or dynamical indication can be signaled via SIB and/or (PC5-) RRC, and/or (PC5) -MAC CE, and/or DCI, and/or SCI.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The words “module, ” “mechanism, ” “element, ” “UE, ” and the like may not be a substitute for the word “means. ” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for. ”

While aspects of the present disclosure have been described in conjunction with the specific embodiments thereof that are proposed as examples, alternatives, modifications, and variations to the examples may be made. Accordingly, embodiments as set forth herein are intended to be illustrative and not limiting. There are changes that may be made without departing from the scope of the claims set forth below.

Claims

A method for RLF detection of sidelink on unlicensed spectrum, wherein the LBT failure based RLF detection is supported.
The method of claim 1, wherein Layer 1 notifies higher layer about the channel access failure if a UE fails to access the channel (s) prior to any, and/or one, and/or multiple, and/or partial, and/or all intended/granted/scheduled/overbooked resource (s) .
The method of claim 1, wherein the maximum count/number of LBT failure instance (s) , and/or the size of the LBT failure detection timer before triggering the consistent LBT channel access failures can be (pre-) configured and/or dynamically indicated based on, such as the network loading, and/or network density, and/or channel busy ratio, and/or traffic QoS, and/or the role of the UE (e.g., supervising UE or supervised UE) , and/or the UE member in the group, etc.
The method of claim 1, wherein the RLF should be declared if constant LBT channel access failures is indicated, and the cause of RLF should be identified as LBT failure.
The method of claim 1, wherein the HARQ-based RLF detection is supported.
The method of claim 5, wherein multiple (consecutive) PSFCH (i.e., HARQ) reception occasions, and/or a PSFCH reception occasion window associated with one PSSCH can be (pre-) configured and/or dynamically indicated.
The method of claim 5, wherein the UE can be (pre-) configured that increment the number of consecutive DTX by 1 if PSFCH reception (s) is (are) absent on any, and/or one, and/or multiple, and/or partial, and/or all (candidate) PSFCH reception occasion (s) associated to the PSSCH transmission.
The method of claim 5, wherein the value of the maximum number of consecutive DTX before triggering SL-U RLF can be (pre-) configured and/or dynamically indicated based on, such as the network loading, and/or network density, and/or channel busy ratio, and/or traffic QoS, etc.
The method of claim 5, wherein the RLF should be declared if the maximum number of consecutive DTX is reached, and the cause of RLF shall be identified as consecutive DTX.
The method of claim 1, wherein the (pre-) configuration and/or indication can be signaled via SIB and/or (PC5-) RRC, and/or (PC5) -MAC CE, and/or DCI, and/or SCI.