Method for sidelink communication based on beamforming in communication system

1. An operation method of a first user equipment (UE) in a communication system, comprising:

transmitting, by a processor, to a second UE a sidelink synchronization signal block (SL-SSB) in an omni-directional scheme;

transmitting, by the processor, the SL-SSB in a beamforming scheme when a response message for the SL-SSB transmitted in the omni-directional scheme is not received from the second UE; and

performing, by the processor, sidelink (SL) communication with the second UE according to the beamforming scheme when a response message for the SL-SSB transmitted in the beamforming scheme is received from the second UE.

2. The operation method according to claim 1 , wherein the SL-SSB includes at least one of the group consisting of: a sidelink primary synchronization signal (SPSS), a sidelink secondary synchronization signal (SSSS), an index of a beam through which the SL-SSB is transmitted, a threshold for a received signal quality of the SL-SSB, and information indicating a resource used for transmission of the response message.

3. The operation method according to claim 1 , wherein the transmitting the SL-SSB in a beamforming scheme includes:

transmitting, by the processor, the SL-SSB to the second UE using n beams each of which covers a specific direction; and

transmitting, by the processor, the SL-SSB to the second UE using m beams each of which covers a specific direction when a response message for the SL-SSB transmitted using the n beams is not received from the second UE,

wherein each of n and m is a natural number, m is greater than n, a width of each of the n beams is wider than a width of each of the m beams, and a coverage of each of the n beams is shorter than a coverage of each of the m beams.

4. The operation method according to claim 1 , wherein the response message includes at least one of an index of a beam through which the SL-SSB is received with a received signal strength equal to or greater than a threshold and information indicating a received signal quality of the SL-SSB.

5. The operation method according to claim 1 , wherein, when the response message includes an index of a beam through which the SL-SSB is received with a received signal strength equal to or greater than a threshold, the SL communication is performed using a beam corresponding to the index of the beam.

6. The operation method according to claim 1 , wherein, when the response message includes indices of a plurality of beams through which the SL-SSB is received with a received signal strength equal to or greater than a threshold, the SL communication is performed using a first beam through which the SL-SSB is received with a largest received signal strength among the plurality of beams, and beams other than the first beam among the plurality of beams are configured as candidate beams.

7. The operation method according to claim 1 , wherein the SL communication is performed in an analog beamforming scheme or a hybrid beamforming scheme.

8. An operation method of a first user equipment (UE) in a communication system, comprising:

receiving, by a processor, a sidelink synchronization signal block (SL-SSB) #L from a second UE using m beams, L being a natural number and m being a natural number greater than or equal to 2;

comparing, by the processor, a received signal strength of the SL-SSB #L with a threshold; and

transmitting, by the processor, a response message for the SL-SSB #L to the second UE in a direction that corresponds to a first beam of the m beams, when the received signal strength of the SL-SSB #L is equal to or greater than the threshold, remaining beams other than the first beam among the m beams being configured as candidates beams.

9. The operation method according to claim 8 , wherein the SL-SSB #L includes at least one of the group consisting of: a sidelink primary synchronization signal (SPSS), a sidelink secondary synchronization signal (SSSS), an index of a beam through which the SL-SSB #L is transmitted, a threshold for a received signal quality of the SL-SSB #L, and information indicating a resource used for transmission of the response message.

10. The operation method according to claim 8 , wherein the response message includes at least one of the group consisting of: an index of a beam through which the SL-SSB #L is received with a received signal strength equal to or greater than the threshold and information indicating a received signal quality of the SL-SSB #L.

11. The operation method according to claim 8 , further comprising, before receiving of the SL-SSB #L,

receiving, by the processor, an SL-SSB #(L−1) from the second UE; and

comparing, by the processor, a received signal strength of the SL-SSB #(L−1) with the threshold,

wherein a response message for the SL-SSB #(L−1) is not transmitted to the second UE when the received signal strength of the SL-SSB #(L−1) is less than the threshold, the SL-SSB #(L−1) is transmitted using n beams by the second UE, and

wherein n is a natural number, m is greater than n, a width of each of then beams is wider than a width of each of the m beams, and a coverage of each of the n beams is shorter than a coverage of each of the m beams.

12. A first user equipment (UE) in a communication system, the first UE including a processor, a transceiver operated by the processor, and a memory configured to store at least one instruction executable by the processor, wherein when executed by the processor, the at least one instruction is configured to:

transmit to a second UE a sidelink synchronization signal block (SL-SSB) in an omni-directional scheme;

transmit the SL-SSB in a beamforming scheme when a response message for the SL-SSB transmitted in the omni-directional scheme is not received from the second UE; and

perform sidelink (SL) communication with the second UE according to the beamforming scheme when a response message for the SL-SSB transmitted in the beamforming scheme is received from the second UE.

13. The first UE according to claim 12 , wherein, when the SL-SSB is transmitted in the beamforming scheme, the at least one instruction is configured to:

transmit the SL-SSB to the second UE using n beams each of which covers a specific direction; and

transmit the SL-SSB to the second UE using m beams each of which covers a specific direction when a response message for the SL-SSB transmitted using the n beams is not received from the second UE,

wherein each of n and m is a natural number, m is greater than n, a width of each of the n beams is wider than a width of each of the m beams, and a coverage of each of the n beams is shorter than a coverage of each of the m beams.

14. The first UE according to claim 12 , wherein the response message includes at least one of the group consisting of: an index of a beam through which the SL-SSB is received with a received signal strength equal to or greater than a threshold and information indicating a received signal quality of the SL-SSB.

15. The first UE according to claim 12 , wherein, when the response message includes indices of a plurality of beams through which the SL-SSB is received with a received signal strength equal to or greater than a threshold, the SL communication is performed using a first beam through which the SL-SSB is received with a largest received signal strength among the plurality of beams, and beams other than the first beam among the plurality of beams are configured as candidate beams.

16. A first user equipment (UE) in a communication system, the first UE including a processor, a transceiver operated by the processor, and a memory configured to store at least one instruction executable by the processor, wherein when executed by the processor, the at least one instruction is configured to:

receive a sidelink synchronization signal block (SL-SSB) #L from a second UE using m beams, L being a natural number and m being a natural number greater than or equal or 2;

compare a received signal strength of the SL-SSB #L with a threshold; and

transmit a response message for the SL-SSB #L to the second UE in a direction that corresponds to a first beam of the m beams when the received signal strength of the SL-SSB #L is equal to or greater than the threshold,

remaining beams other than the first beam among the m beams being configured as candidate beams.

17. The first UE according to claim 16 , wherein the response message includes at least one of the group consisting of: an index of a beam through which the SL-SSB #L is received with a received signal strength equal to or greater than the threshold and information indicating a received signal quality of the SL-SSB #L.

18. The first UE according to claim 16 , wherein the at least one instruction is further configured to:

receive an SL-SSB #(L−1) from the second UE; and

compare a received signal strength of the SL-SSB #(L−1) with the threshold,

wherein a response message for the SL-SSB #(L−1) is not transmitted to the second UE when the received signal strength of the SL-SSB #(L−1) is less than the threshold, the SL-SSB #(L−1) is transmitted using n beams by the second UE, n is a natural number, m is greater than n, a width of each of then beams is wider than a width of each of the m beams, and a coverage of each of the n beams is shorter than a coverage of each of the m beams.