Techniques for initial sidelink beam forming

1 . An apparatus for wireless communication by a first user equipment (UE), comprising:

one or more processors configured to execute instructions stored on one or more memories and to cause the first UE to:

determine one or more parameters for an initial sidelink beamforming procedure involving one or more transmit beams; and

perform, using the one or more parameters, the initial sidelink beamforming procedure, wherein in order to perform the initial sidelink beamforming procedure, the one or more processors are configured to cause the first UE to:

transmit at least a first physical sidelink shared channel (PSSCH) burst, wherein:

in order to transmit at least the first PSSCH burst, the one or more processors are configured to cause the UE to transmit each PSSCH transmission of one or more PSSCH transmissions using a different respective transmit beam of the one or more transmit beams, and

each PSSCH transmission of the one or more PSSCH transmissions includes respective initial sidelink beamforming information;

monitor, based on the initial sidelink beamforming information, for at least one response message from a second UE responding to at least one of the one or more PSSCH transmissions; and

take one or more actions based on the monitoring.

2 . The apparatus of claim 1 , wherein:

the one or more parameters comprise at least one of a duration of the at least the first PSSCH burst, a periodicity associated with the at least the first PSSCH burst, or a time interval between PSSCH bursts of the at least the first PSSCH burst; and

at least one of the periodicity or the time interval is determined based on at least one of:

pre-configuration information stored in memory of the first UE;

configuration information received from a network entity;

a timing requirement associated with the initial sidelink beamforming procedure; or

a timing requirement associated with an initial request for sidelink communication indicated within the one or more PSSCH transmissions.

3 . The apparatus of claim 1 , wherein the one or more processors are further configured to cause the first UE to determine, in a media access control (MAC) layer of the first UE, that data has been obtained from a higher layer indicating a logical channel identifier (LCID) associated with an initial request for sidelink communication.

4 . The apparatus of claim 3 , wherein:

the one or more PSSCH transmissions further include the initial request for sidelink communication; and

at least one of:

the initial request for sidelink communication comprises at least one of a sidelink application identifier, a service type identifier, or an identifier for one or more UEs; or

the initial request for sidelink communication comprises one of a ProSe discovery request message, a direct communication request, or a beamforming media access control-control element (MAC-CE).

5 . The apparatus of claim 1 , wherein the one or more processors are further configured to cause the first UE to select, in a media access control (MAC) layer of the first UE, a set of time-frequency resources for transmitting at least the first PSSCH burst.

6 . The apparatus of claim 1 , wherein, for each PSSCH transmission of the one or more PSSCH transmissions, the respective initial sidelink beamforming information for that PSSCH transmission comprises:

transmit beam information associated with a transmit beam for transmitting that PSSCH transmission; and

at least one of:

a set of preferred time-frequency resources for transmitting the at least one response message; or

a set of non-preferred time-frequency resources to avoid using to transmit the at least one response message.

7 . The apparatus of claim 6 , wherein the transmit beam information associated with the transmit beam for transmitting that PSSCH transmission includes at least one of:

a transmit beam identifier (ID) of the transmit beam;

an index within at least the first PSSCH burst that identifies the transmit beam;

a transmission configuration indicator (TCI) state associated with the transmit beam; or

a spatial filter associated with the transmit beam.

8 . The apparatus of claim 6 , wherein the respective initial sidelink beamforming information is transmitted, in the one or more PSSCH transmissions, in at least one of:

one or more a medium access control-control elements (MAC-CEs); or

second stage sidelink control information (SCI).

9 . The apparatus of claim 1 , wherein:

each different respective transmit beam of the one or more transmit beams is associated with a respective receive beam of one or more receive beams; and

each respective receive beam is associated with a respective subset of time-frequency resources, of a set of time-frequency resources, to use to monitor for the at least one response message.

10 . The apparatus of claim 9 , wherein, in order to monitor for the at least one response message, wherein the one or more processors are configured to cause the first UE to monitor each respective subset of time-frequency resources using each respective receive beam for the at least one response message.

11 . The apparatus of claim 1 , wherein the one or more processors are further configured to cause the first UE to receive, from the second UE based on the monitoring, the at least one response message using a first receive beam of one or more receive beams.

12 . The apparatus of claim 11 , wherein the at least one response message comprises at least one of a discovery response, a direct communication response, an acknowledgement (ACK) message, or a negative ACK (NACK) message.

13 . The apparatus of claim 11 , wherein:

at least one response message indicates a first transmit beam of the one or more transmit beams; and

in order to take the one or more actions, wherein the one or more processors are configured to cause the first UE to communicate communicating with the second UE using the first transmit beam and the first receive beam.

14 . The apparatus of claim 1 , wherein:

in order to take the one or more actions, wherein the one or more processors are configured to cause the first UE to transmit at least a second PSSCH burst based on the monitoring; and

the one or more processors are configured to cause the first UE to transmit at least the second PSSCH burst further based on one of:

reception of the at least one response message including negative acknowledgement information (NACK) or a request to transmit at least the second PSSCH burst; or

failure to receive the at least one response message within a threshold amount of time.

15 . An apparatus for wireless communication by a second user equipment (UE), comprising:

one or more processors configured to execute instructions stored on one or more memories and to cause the second UE to:

receive, from a first UE using a first receive beam of the second UE, a first physical sidelink shared channel (PSSCH) transmission of a first PSSCH burst, wherein:

the first PSSCH transmission is associated with a respective transmit beam of one or more transmit beams of the first UE; and

the first PSSCH transmission of the one or more PSSCH transmissions includes respective initial sidelink beamforming information, comprising at least one of:

a set of preferred time-frequency resources for transmitting at least one response message; or

a set of non-preferred time-frequency resources to avoid using to transmit at least one response message; and

take one or more actions based on the first PSSCH transmission.

16 . The apparatus of claim 15 , wherein the respective initial sidelink beamforming information included in the first PSSCH transmission further comprises transmit beam information associated with the respective transmit beam of the first UE used for transmitting the first PSSCH transmission.

17 . The apparatus of claim 16 , wherein the transmit beam information associated with the respective transmit beam of the first UE used for transmitting the first PSSCH transmission includes at least one of:

a transmit beam identifier (ID) of the respective transmit beam;

an index within the first PSSCH burst that identifies the respective transmit beam;

a transmission configuration indicator (TCI) state associated with the respective transmit beam; or

a spatial filter associated with the respective transmit beam.

18 . The apparatus of claim 16 , wherein the respective initial sidelink beamforming information is received, in the first PSSCH transmission, in at least one of:

one or more a medium access control-control elements (MAC-CEs); or

second stage sidelink control information (SCI).

19 . The apparatus of claim 16 , wherein:

in order to take the one or more actions, the one or more processors are configured to cause the second UE to transmit, using a first transmit beam of the second UE, at least one response message to the first UE based on the respective initial sidelink beamforming information included in the first PSSCH transmission; and

the first transmit beam of the second UE corresponds to the first receive beam of the second UE.

20 . The apparatus of claim 19 , wherein, in order to transmit the at least one response message, the one or more processors are configured to cause the second UE to transmit the response message in a sub-set of time-frequency resources according to one of the set of preferred time-frequency resources or the set of non-preferred time-frequency resources.

21 . The apparatus of claim 19 , wherein the at least one response message indicates at least one of:

the respective transmit beam of one or more transmit beams of the first UE; or

the first receive beam of the second UE.

22 . The apparatus of claim 19 , the one or more processors are further configured to cause the second UE to communicate with the first UE using the first transmit beam of the second UE and the first receive beam of the second UE.

23 . The apparatus of claim 15 , wherein, in order to take the one or more actions based on the first PSSCH transmission, the one or more processors are configured to cause the second UE to determine whether to receive at least a second PSSCH transmission of a second PSSCH burst using a second receive beam of the UE.

24 . The apparatus of claim 23 , wherein:

the first PSSCH transmission includes an initial request for sidelink communication; and

the initial request for sidelink communication comprises one of a ProSe discovery request message, a direct communication request, or a beamforming media access control-control element (MAC-CE).

25 . The apparatus of claim 24 , wherein:

the initial request for sidelink communication includes at least one of a sidelink application identifier, a service type identifier, or an identifier for one or more UEs; and

the one or more processors are configured to cause the second UE to determine whether to receive at least the second PSSCH transmission based on the at least one of the sidelink application identifier, the service type identifier, or the identifier for one or more UEs.

26 . The apparatus of claim 23 , the one or more processors are further configured to cause the second UE to:

perform beam measurements associated with the first receive beam based on the first PSSCH transmission; and

perform beam measurements associated with the second receive beam based on the second PSSCH transmission, wherein the beam measurements associated with the first receive beam and the beam measurements associated with the second receive beam comprise beam sidelink reference signal received power (SL RSRP) measurements.

27 . The apparatus of claim 26 , the one or more processors are configured to cause the second UE to select, based on beam measurements associated with the first receive beam and the beam measurements associated with the second receive beam, one of the first receive beam or the second receive beam for sidelink communication with the first UE.

28 . The apparatus of claim 27 , wherein:

in order to take the one or more actions, the one or more processors are configured to cause the second UE to transmit at least one response message to the first UE using a first transmit beam of the second UE corresponding with the selected one of the first receive beam or the second receive beam;

the at least one response message indicates at least one of:

the respective transmit beam of one or more transmit beams of the first UE; or

the selected one of the first receive beam of the second UE or the second receive beam of the second UE; and

the one or more processors are configured to cause the second UE to transmit the at least one response message based on the respective initial sidelink beamforming information received using the selected one of the first receive beam of the second UE or the second receive beam of the second UE.

29 . A method for wireless communication by a first user equipment (UE), comprising:

determining one or more parameters for an initial sidelink beamforming procedure involving one or more transmit beams; and

performing, using the one or more parameters, the initial sidelink beamforming procedure, comprising:

transmitting at least a first physical sidelink shared channel (PSSCH) burst, comprising transmitting each PSSCH transmission of one or more PSSCH transmissions using a different respective transmit beam of the one or more transmit beams, wherein each PSSCH transmission of the one or more PSSCH transmissions includes respective initial sidelink beamforming information;

monitoring, based on the initial sidelink beamforming information, for at least one response message from a second UE responding to at least one of the one or more PSSCH transmissions; and

taking one or more actions based on the monitoring.

30 . A method for wireless communication by a second user equipment (UE), comprising:

receiving, from a first UE using a first receive beam of the second UE, a first physical sidelink shared channel (PSSCH) transmission of a first PSSCH burst, wherein:

the first PSSCH transmission is associated with a respective transmit beam of one or more transmit beams of the first UE; and

the first PSSCH transmission of the one or more PSSCH transmissions includes respective initial sidelink beamforming information, comprising at least one of:

a set of preferred time-frequency resources for transmitting at least one response message; or

a set of non-preferred time-frequency resources to avoid using to transmit at least one response message; and

taking one or more actions based on the first PSSCH transmission.