Disclosed are a method and an apparatus for sidelink resource allocation in a wireless communication system. The method and apparatus for sidelink resource allocation in a wireless communication system, a method of a first terminal, may include: receiving, from a base station, resource pool configuration information including information on a resource sensing type; in response to that the information on the resource sensing type indicates a sensing operation, sensing transmission resource(s) within a sensing period according to the resource sensing type based on the scheduling information; selecting a first resource based on a result of the sensing on the transmission resource(s); and performing sidelink communication using the selected first resource.

A first wireless device transmits a first sidelink transmission via a first resource, where the first sidelink transmission includes a field indicating resource reservation of a second resource for a second sidelink transmission by the first wireless device. Based on an absence of an acknowledgement (ACK) corresponding to the first sidelink transmission, the first wireless device determines to use the second resource to receive inter user equipment (inter-UE) coordination information from a second wireless device. The first wireless device receives, from the second wireless device and based on the determining, the inter-UE coordination information indicating a set of third resources for one or more third sidelink transmissions by the first wireless device.

Certain aspects of the present disclosure provide techniques for sidelink communications in an unlicensed spectrum. A method that may be performed by a user equipment (UE) and a base station (BS) includes sensing, prior to a start of a time window, a frequency band to determine whether the frequency band is idle, the time window divided in time into a plurality of time periods, the frequency band divided in time across multiple of the plurality of time periods into a corresponding plurality of resources comprising one or more unassigned resources and one or more assigned resources assigned to one or more other wireless communication devices for wireless communication.

Certain aspects of the present disclosure provide techniques for sidelink communications in an unlicensed spectrum. A method that may be performed by a user equipment (UE) and a base station (BS) includes sensing, prior to a start of a time window, a frequency band to determine whether the frequency band is idle, the time window divided in time into a plurality of time periods, the frequency band divided in time across multiple of the plurality of time periods into a corresponding plurality of resources comprising one or more unassigned resources and one or more assigned resources assigned to one or more other wireless communication devices for wireless communication.

According to a first method, a first user equipment (UE) may receive sidelink control information (SCI) over a sidelink communication link between the first UE and a second UE. The SCI may indicate a precoding resource block group (PRG) size associated with sidelink communications with the second UE. The first UE may determine the PRG size for communications over the sidelink communication link based at least in part on the SCI. The first UE may then receive a sidelink message from the second UE via the sidelink communication link based on the determined PRG size, and may transmit a sidelink message to the second UE based on the determined PRG size. According to a second method, a first user equipment may identify a sidelink configuration for a sidelink communication link between the first UE and a second UE, determine a PRG size for communications over the sidelink communication link based at least in part on the sidelink configuration, and receive, from the second UE, a sidelink message based at least in part on the PRG size.

According to a first method, a first user equipment (UE) may receive sidelink control information (SCI) over a sidelink communication link between the first UE and a second UE. The SCI may indicate a precoding resource block group (PRG) size associated with sidelink communications with the second UE. The first UE may determine the PRG size for communications over the sidelink communication link based at least in part on the SCI. The first UE may then receive a sidelink message from the second UE via the sidelink communication link based on the determined PRG size, and may transmit a sidelink message to the second UE based on the determined PRG size. According to a second method, a first user equipment may identify a sidelink configuration for a sidelink communication link between the first UE and a second UE, determine a PRG size for communications over the sidelink communication link based at least in part on the sidelink configuration, and receive, from the second UE, a sidelink message based at least in part on the PRG size.

Methods, systems, and devices for wireless communications are described. A base station (e.g., a central unit (CU) function of the base station) may select, from a set of distributed units (DUs) associated with the CU, a DU of an integrated access and backhaul (IAB) node to control sidelink communications for a user equipment (UE). The base station may determine a configuration of sidelink parameters for the sidelink communications with the UE, the sidelink parameters comprising an identification of the selected DU. The base station may transmit, to the TAB node performing sidelink communications with the UE, an indication of the configuration of sidelink parameters for the sidelink communications.

Embodiments of the present disclosure provide for sidelink communications. In a method for communications, a first terminal device receives information about an identity related to a relay feature of at least one second terminal device via a sidelink channel. The first terminal device determines a relay terminal device of the first terminal device based on the information about the identity. Embodiments of the present disclosure provides a more flexible and feasible communication mechanism for relay discovery and selection without requirements for a specific resource pool for sidelink discovery or performing cyclic redundancy check on resources of the sidelink channel. The identity dedicated to the relay feature can not only be used to distinguish different terminal devices but also enable the terminal device to determine whether they are to be discovered as a candidate relay terminal device by the remote terminal device, and thereby enhancing the relay discovery and selection procedure.

Embodiments of the present disclosure provide for sidelink communications. In a method for communications, a first terminal device receives information about an identity related to a relay feature of at least one second terminal device via a sidelink channel. The first terminal device determines a relay terminal device of the first terminal device based on the information about the identity. Embodiments of the present disclosure provides a more flexible and feasible communication mechanism for relay discovery and selection without requirements for a specific resource pool for sidelink discovery or performing cyclic redundancy check on resources of the sidelink channel. The identity dedicated to the relay feature can not only be used to distinguish different terminal devices but also enable the terminal device to determine whether they are to be discovered as a candidate relay terminal device by the remote terminal device, and thereby enhancing the relay discovery and selection procedure.

A method by which a first apparatus performs wireless communication is proposed. The method may comprise the steps of: selecting a first synchronization source, on the basis of a sidelink synchronization priority; obtaining a first synchronization, on the basis of the first synchronization source; receiving a plurality of synchronization signals from a plurality of synchronization sources; obtaining a plurality of synchronizations, on the basis of the plurality of synchronization signals; selecting a second synchronization source from among the plurality of synchronization sources, on the basis of a gap between a time related to the first synchronization and a time related to a second synchronization being greater than or equal to a threshold value, wherein the second synchronization is obtained on the basis of the second synchronization source; and transmitting, to a second apparatus, a sidelink-synchronization signal block (S-SSB), on the basis of the first synchronization or the second synchronization. For example, the first synchronization source and the second synchronization source may comprise at least one of a global navigation satellite system (GNSS), a base station, or user equipment. For example, the S-SSB may comprise a sidelink primary synchronization signal (S-PSS), a sidelink secondary synchronization signal (S-SSS), and a physical sidelink broadcast channel (PSBCH).