Method and apparatus for sidelink communication
The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Embodiments of the present disclosure provide a sidelink communication method and a user equipment (UE). The method comprises: receiving, by a second UE, an SL-CSI-RS scheduled by an SCI transmitted by a first UE; performing measurement based on the SL-CSI-RS; and, upon receiving a signaling for triggering measurement reporting transmitted by the first UE, reporting a measurement result based on the SL-CSI-RS to the first UE, wherein the SL-CSI-RS transmission is standalone. Thus, the measurement and reporting of sidelink communication are realized, thereby facilitating beam management of sidelink communication in an FR2 frequency band.
1 . A method executed by a second user equipment (UE) in a communication system, comprising:
receiving, from a first UE, a sidelink channel state information reference signal (SL-CSI-RS) scheduled by sidelink control information (SCI);
performing a measurement based on the SL-CSI-RS; and
upon receiving a signaling for triggering measurement reporting transmitted by the first UE, reporting, to the first UE, a measurement result based on the SL-CSI-RS,
wherein the SL-CSI-RS is a standalone transmission.
2 . The method according to claim 1 , wherein the SL-CSI-RS and 1st-stage SCI are time-multiplexed, or the SL-CSI-RS and 2nd-stage SCI are time-multiplexed.
3 . The method according to claim 1 , wherein the SL-CSI-RS comprises at least one SL-CSI-RS resource, wherein one SL-CSI-RS resource is mapped to at least two consecutive time units.
4 . The method according to claim 3 , wherein the one SL-CSI-RS resource is mapped to the at least two consecutive time units in at least one of the following ways:
the one SL-CSI-RS resource is mapped to the at least two consecutive time units by repeating the one SL-CSI-RS resource on the at least two consecutive time units;
the one SL-CSI-RS resource is mapped to the at least two consecutive time units by cyclic shifting; and
the one SL-CSI-RS resource is mapped to the at least two consecutive time units by generating a longer SL-CSI-RS signal sequence.
5 . The method according to claim 1 , wherein the SL-CSI-RS is mapped to all of allocated resource elements (REs) in at least one time unit; or,
the SL-CSI-RS is mapped to part of the allocated REs in the at least one time unit, and a transmitting power on other allocated REs in the at least one time unit is boosted to the part of the allocated REs.
6 . The method according to claim 5 , wherein the SL-CSI-RS is mapped to all of the allocated REs in the at least one time unit in at least one of the following ways:
the SL-CSI-RS is mapped to all of the allocated REs in the at least one time unit by repeating the SL-CSI-RS on all of the allocated REs; and
the SL-CSI-RS is mapped to all of the allocated REs in the at least one time unit by generating a longer SL-CSI-RS signal sequence.
7 . The method according to claim 1 , wherein the SL-CSI-RS comprises at least one SL-CSI-RS resource, and an index of the at least one SL-CSI-RS resource is determined in at least one of the following ways:
an index of a first SL-CSI-RS resource in the at least one SL-CSI-RS resource is indicated by the SCI, and indexes of remaining SL-CSI-RS resources are cyclically increased sequentially;
an index of an SL-CSI-RS resource set where the at least one SL-CSI-RS resource is located is indicated by the SCI, and an index of each SL-CSI-RS resource included in the SL-CSI-RS resource set is configured by a PC5 radio resource control (RRC) signaling; and
the index of each SL-CSI-RS resource in the at least one SL-CSI-RS resource is separately indicated by the SCI.
8 . The method according to claim 1 , wherein the SL-CSI-RS comprises at least one SL-CSI-RS resource, and a starting RE position of the at least one SL-CSI-RS resource is determined in at least one of the following ways:
a starting RE position of a first SL-CSI-RS resource in the at least one SL-CSI-RS resource is indicated by the SCI, and starting RE positions of other SL-CSI-RS resources are cyclically shifted sequentially;
the starting RE position of each SL-CSI-RS resource in the at least one SL-CSI-RS resource is separately indicated by the SCI;
the starting RE position of the first SL-CSI-RS resource in the at least one SL-CSI-RS resource is determined based on at least one of a first UE identity (ID), a second UE ID, an index of a time unit where the SL-CSI-RS resource is located, the index of the SL-CSI-RS resource and a decimal value of cyclic redundancy check (CRC) of the SCI, and the starting RE positions of other SL-CSI-RS resources are cyclically shifted sequentially; and
the starting RE position of each SL-CSI-RS resource in the at least one SL-CSI-RS resource is determined based on at least one of the first UE ID, the second UE ID, the index of the time unit where the SL-CSI-RS resource is located, the index of the SL-CSI-RS resource and the decimal value of CRC of the SCI.
9 . The method according to claim 1 , wherein a priority of the SL-CSI-RS is determined by at least one of the following:
a predefined priority value;
a priority value configured for each resource pool; and
a priority of data transmitted to the second UE by the first UE.
10 . The method according to claim 1 , wherein a 1st-stage SCI or a 2nd-stage SCI associated with the SL-CSI-RS indicates at least one of the following information related to the SL-CSI-RS:
an index of a SL-CSI-RS resource set;
an index of an SL-CSI-RS resource;
an index of a first SL-CSI-RS resource among a plurality of SL-CSI-RS resources;
a transmission configuration indicator (TCI) of the SL-CSI-RS resource;
a TCI of the first SL-CSI-RS resource among a plurality of SL-CSI-RS resources;
a beam ID of the SL-CSI-RS resource;
a beam ID of the first SL-CSI-RS resource among the plurality of SL-CSI-RS resources;
a starting RE position of the SL-CSI-RS resource;
a starting RE position of the first SL-CSI-RS resource among the plurality of SL-CSI-RS resources;
whether the plurality of SL-CSI-RS resources are transmitted by using a same transmitter (TX) spatial filter;
a number of time units occupied by one SL-CSI-RS resource;
a number of SL-CSI-RS resources included in the scheduled SL-CSI-RS;
a frequency domain density of the SL-CSI-RS resources;
whether the SL-CSI-RS resources are repeated on REs;
whether the SL-CSI-RS resources are repeated on time units;
a number of repetitions of the SL-CSI-RS on time units;
a triggering of measurement reporting based on the SL-CSI-RS;
a triggering of reporting of at least one of a plurality of measurement quantities based on the SL-CSI-RS;
an ID of at least one second UE that performs measurement reporting; and
a priority of the SL-CSI-RS.
11 . The method according to claim 1 , wherein the reporting a measurement result based on the SL-CSI-RS to the first UE comprises:
reporting the measurement result based on the SL-CSI-RS to the first UE by a medium access control control element (MAC CE) or a physical sidelink feedback channel (PSFCH).
12 . The method according to claim 11 , wherein the measurement result reported by the MAC CE comprises at least one of the following information:
a measurement quantity of a specific SL-CSI-RS resource;
a largest value among measurement quantities of a plurality of SL-CSI-RS resources, and an index of the largest value among the measurement quantities of the plurality of SL-CSI-RS resources' corresponding SL-CSI-RS resource;
at least two largest values among the measurement quantities of the plurality of SL-CSI-RS resources, and indexes of the two largest value's corresponding SL-CSI-RS resources;
values greater than a first threshold among the measurement quantities of the plurality of SL-CSI-RS resources, and indexes of the values greater than the first threshold's corresponding SL-CSI-RS resources; and
a largest value among measurement quantities of a plurality of SL-CSI-RS resource sets, an index of a corresponding SL-CSI-RS resource set, and an index of the largest value among the measurement quantities of the plurality of SL-CSI-RS resource sets' corresponding SL-CSI-RS resource.
13 . The method according to claim 11 , wherein the reporting a measurement result based on the SL-CSI-RS to the first UE by a PSFCH comprises at least one of the following:
feeding back first state information by the PSFCH if a measurement quantity is greater than or equal to a second threshold, feeding back second state information by the PSFCH if the measurement quantity is less than the second threshold and greater than or equal to a third threshold, or giving no feedback if the measurement quantity is less than the third threshold;
feeding back first state information by the PSFCH if the measurement quantity is greater than or equal to a fourth threshold, or feeding back second state information by the PSFCH if the measurement quantity is less than the fourth threshold; and
feeding back first state information by the PSFCH if the measurement quantity is greater than or equal to a fifth threshold, or giving no feedback if the measurement quantity is less than the fifth threshold.
14 . The method according to claim 11 , wherein the PSFCH for reporting is determined based on at least one of an index of a time unit where the SL-CSI-RS is located, an index of a starting sub-channel of the SL-CSI-RS and a number of sub-channels occupied by the SL-CSI-RS.
15 . The method according to claim 14 , further comprising:
determining a group of PSFCH resources based on at least one of the index of the time unit where the SL-CSI-RS is located, the index of the starting sub-channel of the SL-CSI-RS and the number of sub-channels occupied by the SL-CSI-RS; and
determining a PSFCH resource for reporting in the group of PSFCH resources based on at least one of a first UE ID, a second UE ID and an index of an SL-CSI-RS resource corresponding to the measurement result to be reported.
16 . The method according to claim 13 , wherein the reporting a measurement result based on the SL-CSI-RS to the first UE by a PSFCH comprises:
the SL-CSI-RS comprising a plurality of SL-CSI-RS resources, and feeding back first state information or second state information on a PSFCH resource corresponding to the largest value among measurement quantities of the plurality of SL-CSI-RS resources.
17 . The method according to claim 1 , wherein the signaling for triggering measurement reporting is an SCI or an MAC CE.
18 . The method according to claim 17 , wherein the signaling for triggering measurement reporting is an SCI, and the SL-CSI-RS for performing measurement by the second UE is an SL-CSI-RS scheduled by the SCI.
19 . The method according to claim 18 , wherein the signaling for triggering measurement reporting is a MAC CE, and the SL-CSI-RS for performing measurement by the second UE is at least one of the following:
an SL-CSI-RS transmitted most recently before the MAC CE;
an SL-CSI-RS transmitted in a first preset time window before the MAC CE;
an SL-CSI-RS transmitted most recently after the MAC CE; and
an SL-CSI-RS transmitted in a second preset time window after the MAC CE.
20 . A user equipment, comprising:
a transceiver; and
a processor, which is coupled to the transceiver and configured to:
receive, from a first UE, a sidelink channel state information reference signal (SL-CSI-RS) scheduled by sidelink control information (SCI);
perform a measurement based on the SL-CSI-RS; and
upon receiving a signaling for triggering measurement reporting transmitted by the first UE, report, to the first UE, a measurement result based on the SL-CSI-RS,
wherein the SL-CSI-RS is a standalone transmission.