SIDELINK SYNCHRONIZATION RULES BASED ON NETWORK ENERGY SAVING MODE

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization. The UE may receive a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes. The UE may perform sidelink synchronization in accordance with a priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the scheduling for the one or more network energy saving modes and the mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization. Numerous other aspects are described.

FIELD OF THE DISCLOSURE

Aspects of the present disclosure generally relate to wireless communication and to techniques and apparatuses for sidelink synchronization based on a network energy saving mode.

BACKGROUND

SUMMARY

Some aspects described herein relate to a user equipment (UE) for wireless communication. The UE may include a memory and one or more processors coupled to the memory. The one or more processors may be configured to receive a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization. The one or more processors may be configured to receive a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes. The one or more processors may be configured to perform sidelink synchronization in accordance with a priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the scheduling for the one or more network energy saving modes and the mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

Some aspects described herein relate to a network node for wireless communication. The network node may include a memory and one or more processors coupled to the memory. The one or more processors may be configured to transmit a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization by a UE. The one or more processors may be configured to transmit a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes.

Some aspects described herein relate to a method of wireless communication performed by a UE. The method may include receiving a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization. The method may include receiving a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes. The method may include performing sidelink synchronization in accordance with a priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the scheduling for the one or more network energy saving modes and the mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

Some aspects described herein relate to a method of wireless communication performed by a network node. The method may include transmitting a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization by a UE. The method may include transmitting a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes.

Some aspects described herein relate to a non-transitory computer-readable medium that stores a set of instructions for wireless communication by a UE. The set of instructions, when executed by one or more processors of the UE, may cause the UE to receive a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization. The set of instructions, when executed by one or more processors of the UE, may cause the UE to receive a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes. The set of instructions, when executed by one or more processors of the UE, may cause the UE to perform sidelink synchronization in accordance with a priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the scheduling for the one or more network energy saving modes and the mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

Some aspects described herein relate to a non-transitory computer-readable medium that stores a set of instructions for wireless communication by a network node. The set of instructions, when executed by one or more processors of the network node, may cause the network node to transmit a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization by a UE. The set of instructions, when executed by one or more processors of the network node, may cause the network node to transmit a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes.

Some aspects described herein relate to an apparatus for wireless communication. The apparatus may include means for receiving a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization. The apparatus may include means for receiving a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes. The apparatus may include means for performing sidelink synchronization in accordance with a priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the scheduling for the one or more network energy saving modes and the mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

Some aspects described herein relate to an apparatus for wireless communication. The apparatus may include means for transmitting a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization by a UE. The apparatus may include means for transmitting a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes.

DETAILED DESCRIPTION

In some aspects, the UE120may include a communication manager140. As described in more detail elsewhere herein, the communication manager140may receive a mapping indication that indicates a mapping between a plurality of network energy saving (NES) modes and a plurality of priority rules for sidelink synchronization; receive an NES mode indication that indicates scheduling for one or more NES modes of the plurality of NES modes; and perform sidelink synchronization in accordance with a priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the scheduling for the one or more NES modes and the mapping between the plurality of NES modes and the plurality of priority rules for sidelink synchronization. Additionally, or alternatively, the communication manager140may perform one or more other operations described herein.

In some aspects, the network node110may include a communication manager150. As described in more detail elsewhere herein, the communication manager150may transmit a mapping indication that indicates a mapping between a plurality of NES modes and a plurality of priority rules for sidelink synchronization by a UE; and transmit an NES mode indication that indicates scheduling for one or more NES modes of the plurality of NES modes. Additionally, or alternatively, the communication manager150may perform one or more other operations described herein.

In some aspects, a UE (e.g., the UE120) includes means for receiving a mapping indication that indicates a mapping between a plurality of NES modes and a plurality of priority rules for sidelink synchronization; means for receiving an NES mode indication that indicates scheduling for one or more NES modes of the plurality of NES modes; and/or means for performing sidelink synchronization in accordance with a priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the scheduling for the one or more NES modes and the mapping between the plurality of NES modes and the plurality of priority rules for sidelink synchronization. The means for the UE to perform operations described herein may include, for example, one or more of communication manager140, antenna252, modem254, MIMO detector256, receive processor258, transmit processor264, TX MIMO processor266, controller/processor280, or memory282.

In some aspects, a network node (e.g., the network node110) includes means for transmitting a mapping indication that indicates a mapping between a plurality of NES modes and a plurality of priority rules for sidelink synchronization by a UE; and/or means for transmitting an NES mode indication that indicates scheduling for one or more NES modes of the plurality of NES modes. The means for the network node to perform operations described herein may include, for example, one or more of communication manager150, transmit processor220, TX MIMO processor230, modem232, antenna234, MIMO detector236, receive processor238, controller/processor240, memory242, or scheduler246.

FIG.3is a diagram illustrating an example300of sidelink communications, in accordance with the present disclosure.

As shown inFIG.3, a first UE305-1may communicate with a second UE305-2(and one or more other UEs305) via one or more sidelink channels310. The UEs305-1and305-2may communicate using the one or more sidelink channels310for P2P communications, D2D communications, V2X communications (e.g., which may include V2V communications, V2I communications, and/or V2P communications) and/or mesh networking. In some aspects, the UEs305(e.g., UE305-1and/or UE305-2) may correspond to one or more other UEs described elsewhere herein, such as UE120. In some aspects, the one or more sidelink channels310may use a PC5 interface and/or may operate in a high frequency band (e.g., the 5.9 GHz band). Additionally, or alternatively, the UEs305may synchronize timing of transmission time intervals (TTIs) (e.g., frames, subframes, slots, or symbols) using global navigation satellite system (GNSS) timing.

As further shown inFIG.3, the one or more sidelink channels310may include a physical sidelink control channel (PSCCH)315, a physical sidelink shared channel (PSSCH)320, and/or a physical sidelink feedback channel (PSFCH)325. The PSCCH315may be used to communicate control information, similar to a physical downlink control channel (PDCCH) and/or a physical uplink control channel (PUCCH) used for cellular communications with a network node110via an access link or an access channel. The PSSCH320may be used to communicate data, similar to a physical downlink shared channel (PDSCH) and/or a physical uplink shared channel (PUSCH) used for cellular communications with a network node110via an access link or an access channel. For example, the PSCCH315may carry sidelink control information (SCI)330, which may indicate various control information used for sidelink communications, such as one or more resources (e.g., time resources, frequency resources, and/or spatial resources) where a transport block (TB)335may be carried on the PSSCH320. The TB335may include data. The PSFCH325may be used to communicate sidelink feedback340, such as hybrid automatic repeat request (HARQ) feedback (e.g., acknowledgement or negative acknowledgement (ACK/NACK) information), transmit power control (TPC), and/or a scheduling request (SR).

Although shown on the PSCCH315, in some aspects, the SCI330may include multiple communications in different stages, such as a first stage SCI (SCI-1) and a second stage SCI (SCI-2). The SCI-1may be transmitted on the PSCCH315. The SCI-2may be transmitted on the PSSCH320. The SCI-1may include, for example, an indication of one or more resources (e.g., time resources, frequency resources, and/or spatial resources) on the PSSCH320, information for decoding sidelink communications on the PSSCH, a quality of service (QOS) priority value, a resource reservation period, a PSSCH DMRS pattern, an SCI format for the SCI-2, a beta offset for the SCI-2, a quantity of PSSCH DMRS ports, and/or an MCS. The SCI-2may include information associated with data transmissions on the PSSCH320, such as a HARQ process ID, a new data indicator (NDI), a source identifier, a destination identifier, and/or a channel state information (CSI) report trigger.

In some aspects, a UE305may operate using a sidelink resource allocation mode (e.g., Mode1) where resource selection and/or scheduling is performed by a network node110(e.g., a base station, a CU, or a DU). For example, the UE305may receive a grant (e.g., in downlink control information (DCI) or in a radio resource control (RRC) message, such as for configured grants) from the network node110(e.g., directly or via one or more network nodes) for sidelink channel access and/or scheduling. In some aspects, a UE305may operate using a resource allocation mode (e.g., Mode2) where resource selection and/or scheduling is performed by the UE305(e.g., rather than a network node110). In some aspects, the UE305may perform resource selection and/or scheduling by sensing channel availability for transmissions. For example, the UE305may measure an RSSI parameter (e.g., a sidelink-RSSI (S-RSSI) parameter) associated with various sidelink channels, may measure an RSRP parameter (e.g., a PSSCH-RSRP parameter) associated with various sidelink channels, and/or may measure an RSRQ parameter (e.g., a PSSCH-RSRQ parameter) associated with various sidelink channels, and may select a channel for transmission of a sidelink communication based at least in part on the measurement(s).

Additionally, or alternatively, the UE305may perform resource selection and/or scheduling using SCI330received in the PSCCH315, which may indicate occupied resources and/or channel parameters. Additionally, or alternatively, the UE305may perform resource selection and/or scheduling by determining a channel busy ratio (CBR) associated with various sidelink channels, which may be used for rate control (e.g., by indicating a maximum number of resource blocks that the UE305can use for a particular set of subframes).

In the resource allocation mode where resource selection and/or scheduling is performed by a UE305(e.g., Mode2), the UE305may generate sidelink grants, and may transmit the grants in SCI330. A sidelink grant may indicate, for example, one or more parameters (e.g., transmission parameters) to be used for an upcoming sidelink transmission, such as one or more resource blocks to be used for the upcoming sidelink transmission on the PSSCH320(e.g., for TBs335), one or more subframes to be used for the upcoming sidelink transmission, and/or an MCS to be used for the upcoming sidelink transmission. In some aspects, a UE305may generate a sidelink grant that indicates one or more parameters for semi-persistent scheduling (SPS), such as a periodicity of a sidelink transmission. Additionally, or alternatively, the UE305may generate a sidelink grant for event-driven scheduling, such as for an on-demand sidelink message.

FIG.4is a diagram illustrating an example400of sidelink communications and access link communications, in accordance with the present disclosure.

As shown inFIG.4, a transmitter (Tx)/receiver (Rx) UE405and an Rx/Tx UE410may communicate with one another via a sidelink, as described above in connection withFIG.3. As further shown, in some sidelink modes, a network node110may communicate with the Tx/Rx UE405(e.g., directly or via one or more network nodes), such as via a first access link. Additionally, or alternatively, in some sidelink modes, the network node110may communicate with the Rx/Tx UE410(e.g., directly or via one or more network nodes), such as via a first access link. The Tx/Rx UE405and/or the Rx/Tx UE410may correspond to one or more UEs described elsewhere herein, such as the UE120ofFIG.1. Thus, a direct link between UEs120(e.g., via a PC5 interface) may be referred to as a sidelink, and a direct link between a network110and a UE120(e.g., via a Uu interface) may be referred to as an access link. Sidelink communications may be transmitted via the sidelink, and access link communications may be transmitted via the access link. An access link communication may be either a downlink communication (from a network node110to a UE120) or an uplink communication (from a UE120to a network node110).

FIG.5is a diagram illustrating an example500of sidelink synchronization, in accordance with the present disclosure.

In a typical cellular network, a UE may achieve time and frequency synchronization on an access link using periodic broadcasts (e.g., periodic synchronization signal block (SSB) transmissions) from a network node. In sidelink operation, one or more synchronization sources may transmit sidelink synchronization information to establish a reference time, indicate symbol timing, indicate frame timing, and/or otherwise transmit information to ensure that nearby UEs engaged in sidelink communication have the same timing reference. Sidelink synchronization procedures and sidelink communication procedures may be decoupled, which differs from access link communication. For example, in some cases, a UE may transmit sidelink synchronization signals, even though the UE is not a Tx UE involved in sidelink transmissions to an Rx UE. In some cases, a UE may not transmit sidelink synchronization signals, even though the UE is a Tx UE involved in sidelink transmission to an Rx UE. In some cases, an Rx UE communicating with a Tx UE via sidelink communications may perform sidelink synchronization (e.g., time and/or frequency synchronization) based on a sidelink synchronization signal transmitted by a sidelink synchronization source other than the Tx UE.

In some examples, the synchronization sources available to a UE for sidelink synchronization may include a GNSS, a network node (e.g., a gNB or an eNB), synchronization reference UEs (SyncRef UEs), and an internal clock of the UE. As shown inFIG.5, a Tx UE502may transmit sidelink communications to a first Rx UE504and a second Rx UE506. A GNSS may be the sidelink synchronization source for the Tx UE502. For example, the Tx UE502may perform sidelink synchronization based at least in part on a GNSS signal transmitted by the GNSS. In this case, the Tx UE502may synchronize to GNSS timing based at least in part on the GNSS signal. A network node (e.g., a gNB or an eNB) may be the sidelink synchronization source for the first Rx UE504. For example, the first Rx UE504may perform sidelink synchronization based at least in part on an SSB transmitted by the network node. A SyncRef UE may be the sidelink synchronization source for the second Rx UE506. For example, the second Rx UE506may perform sidelink synchronization based at least in part on a sidelink SSB (S-SSB) transmitted by the SyncRef UE. A SyncRef UE may be any UE (e.g., UE120) that transmits sidelink synchronization signals (e.g., in S-SSBs).

In some examples, an S-SSB may occupy one slot and use the same numerology as configured in a sidelink bandwidth part (BWP) (e.g., the same numerology as a PSCCH and/or PSSCH). For example, an S-SSB generally may include 11 RBs over 13 symbols in a slot, where a physical sidelink broadcast channel (PSBCH) is transmitted in the first symbol and the sixth through thirteenth symbols, a sidelink PSS (S-PSS) is transmitted in the second and third symbols, and a sidelink SSS (S-SSS) is transmitted in the fourth and fifth symbols. In this case, the S-PSS and S-SSS may occupy127subcarriers and use the same sequences as a PSS and SSS used for an access link SSB, and the PSBCH/DMRS may occupy132subcarriers. In a sidelink SSB configuration, the last (fourteenth) symbol may be reserved as a gap symbol or a guard symbol for transmission/reception retuning due to the sidelink being configured as a time division duplexing (TDD) band. The S-PSS and S-SSS may be jointly referred to as a sidelink synchronization signal (SLSS), which may be used for time and frequency synchronization among nearby UEs. For example, nearby UEs may include UEs that are in sidelink communication with each other, UEs that are within a threshold proximity of each other, and/or UEs that are within a communication range of each other, among other examples.

FIG.6is a diagram illustrating an example600of priority rules for sidelink synchronization, in accordance with the present disclosure.

A UE may select a sidelink synchronization source for sidelink synchronization based on a predefined priority rule that specifies a set of priorities for sidelink synchronization sources. For example, the predefined priority rule may be configured (e.g., via a configuration received from a network node) or pre-configured for a UE.FIG.6shows three example priority rules, including a first GNSS-based synchronization priority rule (GNSS-based sync case1), a second GNSS-based synchronization priority rule (GNSS-based sync case2), and a network-node-based synchronization priority rule (gNB/eNB-based sync).

As shown by reference number605, the first GNSS-based synchronization priority rule (GNSS-based sync case1) defines a synchronization hierarchy in which a GNSS signal has a highest priority (e.g., priority P0), whereby a UE synchronizes to GNSS timing whenever the GNSS signal is available. In cases in which the GNSS signal is unavailable, the UE searches for and synchronizes to S-SSBs from synchronization sources based on a descending priority, where a UE directly synchronized to a GNSS signal has a second highest priority (e.g., priority P1), a UE indirectly synchronized to a GNSS signal has a next highest priority (e.g., priority P2), and remaining UEs have a lowest priority (e.g., priority P6).

As shown by reference number610, the second GNSS-based synchronization priority rule (GNSS-based sync case2) defines a synchronization hierarchy in which a GNSS signal has a highest priority (e.g., priority P0), whereby a UE synchronizes to GNSS timing whenever the GNSS signal is available. In cases in which the GNSS signal is unavailable, the UE searches for and synchronizes to synchronization signals (e.g., S-SSBs or SSBs) from synchronization sources based on a descending priority, where a UE directly synchronized to a GNSS signal has a second highest priority (e.g., priority P1), a UE indirectly synchronized to a GNSS signal has a next highest priority (e.g., priority P2), a network node (e.g., a gNB or an eNB) has a next highest priority (e.g., priority P3), a UE directly synchronized to a network node has a next highest priority (e.g., priority P4), a UE indirectly synchronized to a network node has a next highest priority (e.g., priority P5), and remaining UEs have a lowest priority (e.g., priority P6).

As shown by reference number615, the network-node-based synchronization priority rule (gNB/eNB-based sync) defines a synchronization hierarchy in which a network node (e.g., a gNB or an eNB) has a highest priority (e.g., priority P0′), whereby a UE performs sidelink synchronization based on an SSB transmitted by a network node whenever available. In cases in which the SSB transmitted by the network node is unavailable, the UE searches for and synchronizes to synchronization signals (e.g., S-SSBs or GNSS signals) from synchronization sources based on a descending priority, where a UE directly synchronized to a network node has a second highest priority (e.g., priority P1′), a UE indirectly synchronized to a network node has a next highest priority (e.g., priority P2′), a GNSS has a next highest priority (e.g., priority P3′), a UE directly synchronized to a GNSS signal has a next highest priority (e.g., priority P4′), a UE indirectly synchronized to a GNSS signal has a next highest priority (e.g., priority P5′), and remaining UEs have a lowest priority (e.g., priority P6′).

A UE may transmit S-SSBs if the UE receives S-SSBs from another UE whose timing reference is derived from a node (e.g., a UE, a network node, or a GNSS transmitter) with a lower priority than the UE in accordance with the priority rule configured (or pre-configured) for the UE. In some examples, if a UE cannot receive any SSBs, S-SSBs, or GNSS signals, the UE may transmit S-SSBs with a local clock of the UE as the synchronization source. When S-SSBs are received by a UE, the priority of the S-SSBs may be identified by the associated synchronization signal identifiers (SSIDs) and the content of the PSBCH (e.g., an in-coverage indicator field included in the PSBCH).

FIG.7is a diagram illustrating an example700of NES modes, in accordance with the present disclosure.

In some examples, a network node may be configured to operate in different NES modes (also referred to as “NES states”) over time, where each NES mode may use one or more techniques to adapt transmission and/or reception in time, frequency, spatial, and/or power domains. For example, the NES modes may include a normal operation mode (which may also be referred to as a legacy mode or a default mode) and one or more NES modes that may be associated with a lower power consumption than the normal operation mode. As shown inFIG.7, a network node may configure a semi-static pattern for switching between different NES modes to achieve network energy savings. For example, the semi-static pattern may be configured via RRC signaling. The semi-static pattern may include a sequence of NES modes that the network node follows with a given periodicity. For example, as shown inFIG.7, in accordance with the semi-static pattern, the network node may operate in a first NES mode (NES1) for a first time period, the network node may then operate in a flexible mode for a second time period, and the network node may then operate in a second NES mode (NES2) for a third time period. The configured pattern for switching NES modes is repeated with the periodicity.

InFIG.7, NES1and NES2may be different NES modes for the network node. In some examples, one NES mode (e.g., NES1) may be the normal operation mode, and the other NES mode (e.g., NES2) may be an NES mode associated with at least one operation that reduced network energy consumption, as compared to the normal operation mode. In some examples, NES1may be a mode of operation in which the network node serves UEs with a first number (e.g., 64) of antenna ports, and NES2may be a mode of operation in which the network node serves UEs with a second number (e.g., 32) of antenna ports. In some examples, NES1may be a first sleep mode (e.g., a light sleep mode), and NES2may be a second sleep mode (e.g., a deep sleep mode). In some examples, NES1may be a downlink-only operation mode, and NES2may be a downlink and uplink operation mode. In some examples, the semi-static pattern that schedules switching between NES modes may include more than two NES modes. For example, the network node may define and configure the UE with any number of different NES modes. The flexible mode may be a mode in which the network node may operate in accordance with any suitable NES mode (for example, depending on current traffic conditions), and the NES mode that the network node selects for the flexible mode may be dynamically indicated to UEs served by the network node. For example, depending on the current traffic conditions, the network node may dynamically indicate, to the UEs, that the network node will operate in NES1, NES2, or any other configured NES mode during the time duration associated with the flexible mode. Although example700shows a semi-static pattern that includes the flexible mode, in some other examples, the semi-static pattern may not include the flexible mode. In this case, the semi-static pattern may configure switching between NES1, NES2, and/or one or more other NES modes.

The scheduling of a given NES mode (e.g., via the semi-static pattern and/or a dynamic indication for the flexible mode) may depend on expected traffic (e.g., downlink and/or uplink traffic) for the network node. For example, for a time period in which a smaller amount of traffic is expected, the network node may operate in an NES mode that uses a smaller number of antenna ports, while for a time period in which a larger amount of traffic is expected, the network node may operate in an NES mode that uses a larger number of antenna ports.

In some cases, characteristics associated with SSB transmission by a network node may change, depending on the NES mode in which the network node is operating, which may adversely affect UEs performing sidelink synchronization based on the SSBs transmitted by the network node. In some examples, the SSB transmit power may be reduced in an NES mode due to antenna adaption and/or power adaption by the network node (e.g., due to the number of antennas used for SSB transmission). In some examples, transmission of SSBs by the network node may be muted completely in an NES mode, for example to allow the network node to enter a deep sleep mode. In some examples, the network node may turn off certain antenna panels covering certain areas in an NES mode, which may prevent UEs in that area from maintaining synchronization for sidelink communications. Thus, a network node switching between NES modes may decrease the reliability of sidelink synchronization performed by UEs in a coverage area of the network node.

Some techniques and apparatuses described herein enable a UE to perform sidelink synchronization using sidelink synchronization rules that are based at least in part on an NES mode of a network node. In some aspects, the UE may receive a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization. The UE may receive an NES mode indication that indicates scheduling for one or more NES modes for a network node. The UE may perform sidelink synchronization in accordance with a priority rule of the plurality of priority rules based at least in part on the scheduling for the one or more network energy saving modes and the mapping between the plurality of network energy saving modes and the plurality of priority rules. As a result, the UE may change priority rules for sidelink synchronization based at least in part on a change to the NES mode for the network node. For example, the priority rule may prioritize GNSS-based sidelink synchronization in an NES mode in which the SSB transmission power is reduced or SSBs are not transmitted by the network node. In this way, the reliability of sidelink synchronization performed by UEs may be increased, while reducing network power consumption in one or more NES modes.

FIG.8is a diagram illustrating an example800associated with sidelink synchronization based on an NES mode, in accordance with the present disclosure. As shown inFIG.8, example800includes communication between a network node110and a UE120. In some aspects, the network node110and the UE120may be included in a wireless network, such as wireless network100. The network node110and the UE120may communicate via a wireless access link, which may include an uplink and a downlink. In some aspects, the UE120may communicate with one or more other UEs via sidelink communications.

As shown inFIG.8, and by reference number805, the UE120may receive a mapping indication that indicates a mapping between a plurality of NES modes for the network node110and a plurality of priority rules for sidelink synchronization. In some aspects, as shown inFIG.8, the network node110may transmit the mapping indication, and the UE120may receive the mapping indication from the network node110. In some aspects, the mapping indication may be included in a system information block (SIB) broadcast by network node110. For example, the mapping indication may be included in an SIB type #1 (SIB1) or an other SIB (OSIB). In this case, the UE120may receive the SIB that includes the mapping indication. In some aspects, the mapping indication may be RRC configured for the UE120. For example, the network node110may transmit, and the UE120may receive, an RRC message that includes the mapping indication.

AlthoughFIG.8shows the UE120receiving the mapping indication from the network node110, in some other aspects, the UE120may receive the mapping indication from another UE (e.g., a sidelink UE) instead of from the network node110. For example, the UE120may receive, from another UE (e.g., a sidelink UE), a sidelink communication that includes the mapping indication. For example, in a case in which the UE120is out of a coverage range of the network node110, the UE120may receive the mapping indication from a sidelink UE that is in the coverage range of the network node110. In some aspects, one or more sidelink UEs may broadcast (or share) the mapping indication via PSBCH communication, and the UE120may receive a PSBCH communication that includes the mapping indication. In some aspects, layer 1 (L1), layer 2 (L2), or layer 3 (L3) signaling between UEs may be used to transmit the mapping indication. For example, in a case in which L1 signaling is used, the mapping indication may be included in SCI (e.g., SCI-1carried on PSCCH, SCI-2carried on PSSCH, or a new SCI format), a dedicated PSSCH communication (e.g., in a dedicated PSSCH resource), or a sidelink wake-up signal (SL-WUS) transmitted from a sidelink UE to the UE120. In a case in which L2 signaling is used, the mapping indication may be included in a PC5 medium access control (MAC) control element (MAC-CE) transmitted from a sidelink UE to the UE120. In a case in which L3 signaling is used, the mapping indication may be included in a PC5 RRC message transmitted from a sidelink UE to the UE120. In some aspects, the L1, L2, or L3 signaling including the mapping indication may be transmitted to the UE120on demand in connection with a request for the mapping indication (or a request for an NES mode indication and the mapping indication) transmitted by the UE120(e.g., via L1, L2, or L3 signaling) to a sidelink UE.

In some aspects, once the UE120receives the mapping indication (e.g., from the network node110or from a sidelink UE), the UE120may transmit a sidelink communication that includes the mapping indication. For example, the UE120may transmit the mapping indication in a sidelink communication to be received by one or more other UEs. In some aspects, the UE120may broadcast the mapping indication in a PSBCH communication. In some aspects, the UE120may transmit the mapping indication to another UE via L1 signaling (e.g., in SCI, a dedicated PSSCH communication, or an SL-WUS), L2 signaling (e.g., in a PC5 MAC-CE), or L3 signaling (e.g., in a PC5 RRC message). In this case, the UE120may transmit the mapping indication to the other UE based at least in part on receiving, from the other UE (e.g., via L1, L2, or L3 signaling), a request for the mapping indication (or a request for an NES mode indication and the mapping indication).

The mapping indication may indicate a mapping between a plurality of NES modes for the network node110and a plurality of priority rules for sidelink synchronization. Each priority rule, of the plurality of priority rules, may indicate priorities for a set of sidelink synchronization sources (e.g., GNSS, network node, UEs directly and indirectly synchronized with the GNSS or network node, and/or other UEs). For example, the plurality of priority rules may include the GNSS-based sync case1priority rule described in connection withFIG.6, the GNSS-based sync case2priority rule described in connection withFIG.6, the gNB/eNB-based sync priority rule described in connection withFIG.6, and/or other priority rules for sidelink synchronization.

In some aspects, the mapping indication may indicate a mapping between a current NES mode of the network node110and a corresponding priority rule. As shown inFIG.8, and by reference number810, in an example mapping, a first NES mode (NES1) may map to the GNSS-based sync case2priority rule, a second NES mode (NES2) may map to the gNB/eNB-based sync priority rule, and all other NES modes may map to the GNSS-based sync case2priority rule. For example, in this case, NES1may be an NES mode in which SSBs are not transmitted by the network node110or the SSB transmission power is reduced as compared with NES2.

In some aspects, the mapping indication may indicate a mapping for determining the priority rule based at least in part on a current NES mode and one or more future NES modes of the network node110. That is, the UE120may determine the priority rule, in accordance with the mapping indication, as a function of the current NES mode and one or more future NES modes of the network node110. In this case, the dependence on the future NES modes may be limited to a time window. For example, the mapping indication may indicate the priority rules as a function of the current NES mode and one or more future NES modes within a time window (e.g., from a current time at which the UE120is determining the priority rule). For example, the mapping indication may indicate for the UE120to use the gNB/eNB-based sync priority rule if the current NES mode is NES1and all future NES modes during the next 1 second time window are either NES1or the normal operation mode, and to otherwise use the GNSS-based sync case2priority rule.

As further shown inFIG.8, and by reference number815, the UE120may receive an NES mode indication. The NES mode indication may indicate scheduling for one or more NES modes of the network node110. As shown inFIG.8, in some aspects, the network node110may transmit the NES mode indication, and the UE120may receive the NES mode indication transmitted by the network node110. In some aspects, the NES mode indication may indicate a configuration of a pattern (e.g., a semi-static pattern) for switching between multiple NES modes. For example, the NES mode indication may be an indication of a pattern for switching between multiple NES modes included in an RRC message transmitted from the network node110to the UE120. In some aspects, the NES mode indication may be a dynamic indication of a switch to an NES mode. In this case, the dynamic indication of the switch to the NES mode may be included in DCI or a MAC-CE transmitted from the network node110to the UE120. For example, the dynamic indication may indicate an NES mode to be used for a flexible mode in the configured pattern for switching between multiple NES modes.

AlthoughFIG.8shows the UE120receiving the NES mode indication from the network node110, in some other aspects, the UE120may receive the NES mode indication from another UE (e.g., a sidelink UE). In some aspects, a sidelink UE may broadcast the NES mode indication in a PSBCH communication. In some aspects, a sidelink UE may transmit the NES mode indication to the UE120via L1 signaling (e.g., in SCI (SCI-1, SCI-2, or a new SCI format), a dedicated PSSCH communication, or an SL-WUS), L2 signaling (e.g., in a PC5 MAC-CE), or L3 signaling (e.g., in a PC5 RRC message). In this case, the sidelink UE may transmit the NES mode indication to the UE120based at least in part on the UE120transmitting (e.g., via L1, L2, or L3 signaling) a request for the NES mode indication (or a request for the NES mode indication and the mapping indication) to the sidelink UE.

In some aspects, once the UE120receives the NES mode indication (e.g., from the network node110or a sidelink UE), the UE120may transmit the NES mode indication in a sidelink communication to be received by one or more other UEs. In some aspects, the UE120may broadcast the NES mode indication in a PSBCH communication. In some aspects, the UE120may transmit the NES mode indication to another UE via L1 signaling (e.g., in SCI, a dedicated PSSCH communication, or an SL-WUS), L2 signaling (e.g., in a PC5 MAC-CE), or L3 signaling (e.g., in a PC5 RRC message). In this case, the UE120may transmit the NES mode indication to the other UE based at least in part on receiving, from the other UE (e.g., via L1, L2, or L3 signaling), a request for the NES mode indication (or a request for an NES mode indication and the mapping indication).

As further shown inFIG.8, and by reference number820, the UE120may perform sidelink synchronization based at least in part on the mapping indication and the NES mode indication. In some aspects, the UE120may perform sidelink synchronization in accordance with a priority rule for sidelink synchronization based at least in part on the scheduling for the one or more NES modes indicated by the NES mode indication and the mapping between the plurality of NES modes and the plurality of priority rules for sidelink synchronization indicated by the mapping indication. For example, the UE120may use the mapping between the plurality of NES modes and the plurality of priority rules to determine which priority rule, of the plurality of priority rules, to apply for sidelink synchronization based at least in part on the indicated scheduling for the one or more NES modes.

In some aspects, the UE120may determine the priority rule based on a current NES mode for the network node110, as indicated by the NES mode indication. For example, the UE120may determine the current NES mode from a configured pattern (e.g., a semi-static pattern) for NES mode switching and/or a dynamic indication of an NES mode. In this case, based at least in part on the mapping between the plurality of NES modes and the plurality of priority rules, the UE120may determine the priority rule, of the plurality of priority rules, that corresponds to the current NES mode of the network node110.

In some aspects, the UE120may determine the priority rule based at least in part on the current NES mode and one or more future NES modes. For example, the UE120may determine the priority rule based at least in part on the current NES mode at a current time and one or more future NES modes scheduled in a time window (e.g., 1 second) from the current time. The UE120may determine the current NES mode and the one or more NES modes scheduled in the time window from the configured pattern (e.g., a semi-static pattern) for NES mode switching and/or a dynamic indication of an NES mode (e.g., for a configured flexible mode). In this case, based at least in part on the mapping between the plurality of NES modes and the plurality of priority rules, the UE120may determine the priority rule, of the plurality of priority rules, to be applied in connection with the current NES mode and the one or more future NES modes within the time window.

The priority rule determined by the UE120may indicate priorities for a set of sidelink synchronization sources, and the UE120may select a sidelink synchronization source in accordance with the priorities for the set of sidelink sources indicated by the priority rule. For example, the priority rule may be the GNSS-based sync case1priority rule, the GNSS-based sync case2priority rule, or the gNB/eNB-based sync priority rule, among other examples. As described above in connection withFIG.6, in a case in which the priority rule is the GNSS-based sync case1priority rule, the UE120may prioritize, as the sidelink synchronization source, a GNSS signal, then a UE directly synchronized to a GNSS signal, then a UE indirectly synchronized to a GNSS signal, and then remaining UEs. As described above in connection withFIG.6, in a case in which the priority rule is the GNSS-based sync case2priority rule, the UE120may prioritize, as the sidelink synchronization source, a GNSS signal, then a UE directly synchronized to a GNSS signal, then a UE indirectly synchronized to a GNSS signal, then a network node (e.g., the network node110), then a UE directly synchronized to a network node, then a UE indirectly synchronized to a network node, and then remaining UEs. As described above in connection withFIG.6, in a case in which the priority rule is the gNB/eNB priority rule, the UE120may prioritize, as the sidelink synchronization source, a network node (e.g., the network node110), then a UE directly synchronized to a network node, then a UE indirectly synchronized to a network node, then a GNSS signal, then a UE directly synchronized to a GNSS signal, then a UE indirectly synchronized to a GNSS signal, and then remaining UEs.

The UE120may receive a synchronization signal from the selected sidelink synchronization source, and the UE120may perform sidelink synchronization (e.g., time and/or frequency synchronization) based at least in part on the synchronization signal. For example, in a case in which the sidelink synchronization source is a GNSS, the synchronization signal may be a GNSS signal. In a case in which the sidelink synchronization source is a network node (e.g., the network node110), the synchronization signal may be (or may be included in) an SSB transmitted by the network node. In a case in which the sidelink synchronization source is another UE (e.g., a SyncRef UE), the synchronization signal may be (or may be included in) an S-SSB transmitted by the other UE.

Once the UE120performs sidelink synchronization, the UE120may perform sidelink communications with one or more other UEs. For example, the UE120may transmit one or more sidelink communications to one or more other UEs and/or receive one or more sidelink communications from one or more other UEs. In some aspects, once the UE120performs sidelink synchronization, the UE120may transmit a synchronization signal that may be used by one or more other UEs for sidelink synchronization. For example, the UE120may transmit an S-SSB based at least in part on the UE120receiving an S-SSB from another UE whose timing reference is derived from a node (e.g., a sidelink synchronization source) with a lower priority than the UE120in accordance with the priority rule determined by the UE120.

In some aspects, the UE120may update the priority rule for sidelink synchronization based at least in part on a change in the NES mode of the network node110, in accordance with the mapping between the NES modes and the priority rules. In some aspects, the UE120may be triggered to update the priority rule by an NES mode change notification. In this case, the UE120may receive (e.g., from the network node110or another UE) an NES mode change notification, and the UE120may switch from the one priority rule to another priority rule based at least in part on the NES mode change notification and the mapping between the plurality of NES modes and the plurality of priority rules. For example, the NES mode change notification may be a dynamic indication of a change from one NES mode to another NES mode. The UE120, in connection with switching the priority rule, may perform sidelink synchronization based at least in part on a different sidelink synchronization source in accordance with the updated priority rule.

In some aspects, the priority rule determined by the UE120may be associated with a time window for validity of the priority rule. For example, each priority rule, of the plurality of priority rules indicated by the mapping indication, may be associated with a respective time window for validity, or all of the plurality of priority rules may be associated with the same time window for validity. In this case, the expiration of the time window for validity of the priority rule may trigger the UE120to update the priority rule (e.g., based at least in part on the mapping between the NES modes and the priority rules and the current and/or future scheduled NES modes for the network node110). The UE120, in connection with switching the priority rule, may perform sidelink synchronization based at least in part on a different sidelink synchronization source in accordance with the updated priority rule.

In some aspects, the UE120may be triggered to update the priority rule based at least in part on an indication from another UE120via L1 signaling (e.g., in SCI (SCI-1, SCI-2, or a new SCI format), a dedicated PSSCH communication, or an SL-WUS), L2 signaling (e.g., in a PC5 MAC-CE), or L3 signaling (e.g., in a PC5 RRC message). In some aspects, the UE120may be triggered to update the priority rule based at least in part on an updated mapping indication. For example, the UE120may receive an updated mapping indication that indicates an updated mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization, and the UE120may switch from one priority rule to another priority rule based at least in part on the updated mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization. In some aspects, the UE120may receive the updated mapping indication from the network node110. In other aspects, the UE120may receive the updated mapping indication in a sidelink communication (e.g., via L1, L2, or L3 signaling) from another UE. For example, the updated mapping indication may be included in SCI (e.g., SCI-1carried on PSCCH, SCI-2carried on PSSCH, or a new SCI format), a dedicated PSSCH communication (e.g., in a dedicated PSSCH resource), an SL-WUS, a PC5 MAC-CE, or a PC5 RRC message.

FIG.9is a diagram illustrating an example process900performed, for example, by a UE, in accordance with the present disclosure. Example process900is an example where the UE (e.g., UE120) performs operations associated with sidelink synchronization based on an NES mode.

As shown inFIG.9, in some aspects, process900may include receiving a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization (block910). For example, the UE (e.g., using communication manager140and/or reception component1102, depicted inFIG.11) may receive a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization, as described above.

As further shown inFIG.9, in some aspects, process900may include receiving a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes (block920). For example, the UE (e.g., using communication manager140and/or reception component1102, depicted inFIG.11) may receive a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes, as described above.

As further shown inFIG.9, in some aspects, process900may include performing sidelink synchronization in accordance with a priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the scheduling for the one or more network energy saving modes and the mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization (block930). For example, the UE (e.g., using communication manager140and/or sidelink synchronization component1108, depicted inFIG.11) may perform sidelink synchronization in accordance with a priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the scheduling for the one or more network energy saving modes and the mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization, as described above.

In a first aspect, each priority rule, of the plurality of priority rules, indicates priorities for a set of sidelink synchronization sources, and performing sidelink synchronization in accordance with a priority rule of the plurality of priority rules includes performing sidelink synchronization based at least in part on a sidelink synchronization source, of the set of sidelink synchronization sources, in accordance with the priorities for the set of sidelink synchronization sources indicated by the priority rule.

In a second aspect, alone or in combination with the first aspect, receiving the mapping indication includes receiving, from a network node, an SIB that includes the mapping indication.

In a third aspect, alone or in combination with one or more of the first and second aspects, receiving the mapping indication includes receiving, from a network node, an RRC message that includes the mapping indication.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, receiving the mapping indication includes receiving, from another UE, a sidelink communication that includes the mapping indication.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, the mapping indication is included in SCI, a dedicated PSSCH communication, an SL-WUS, a PC5 MAC-CE, a PC5 RRC message, or a sidelink broadcast channel communication.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, the priority rule, of the plurality of priority rules, is associated with a current network energy saving mode.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, the priority rule, of the plurality of priority rules, is based at least in part on a current network energy saving mode and one or more future network energy saving modes indicated by the network energy saving mode indication.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, the one or more future network energy saving modes include one or more future network energy saving modes scheduled in a time window from a current time.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, process900includes receiving a network energy saving mode change notification, and switching from the priority rule, of the plurality of priority rules for sidelink synchronization, to another priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the network energy saving mode change notification.

In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, process900includes switching from the priority rule, of the plurality of priority rules for sidelink synchronization, to another priority rule of the plurality of priority rules for sidelink synchronization based at least in part on expiration of a time window for validity of the priority rule.

In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, process900includes receiving an updated mapping indication that indicates an updated mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization, and switching from the priority rule, of the plurality of priority rules for sidelink synchronization, to another priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the updated mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, the updated mapping indication is included in SCI, a dedicated PSSCH communication, an SL-WUS, a PC5 MAC-CE, or a PC5 RRC message.

In a thirteenth aspect, alone or in combination with one or more of the first through twelfth aspects, process900includes transmitting a sidelink communication that includes the mapping indication.

FIG.10is a diagram illustrating an example process1000performed, for example, by a network node, in accordance with the present disclosure. Example process1000is an example where the network node (e.g., network node110) performs operations associated with sidelink synchronization based on an NES mode.

As shown inFIG.10, in some aspects, process1000may include transmitting a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization by a UE (block1010). For example, the network node (e.g., using communication manager150and/or transmission component1204, depicted inFIG.12) may transmit a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization by a UE, as described above.

As further shown inFIG.10, in some aspects, process1000may include transmitting a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes (block1020). For example, the network node (e.g., using communication manager150and/or transmission component1204, depicted inFIG.12) may transmit a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes, as described above.

In a first aspect, each priority rule, of the plurality of priority rules, indicates priorities for a set of sidelink synchronization sources.

In a second aspect, alone or in combination with the first aspect, transmitting the mapping indication includes transmitting an SIB that includes the mapping indication.

In a third aspect, alone or in combination with one or more of the first and second aspects, transmitting the mapping indication includes transmitting an RRC message that includes the mapping indication.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, process1000includes transmitting a network energy saving mode change notification.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, process1000includes transmitting an updated mapping indication that indicates an updated mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

The reception component1102may receive a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization. The reception component1102may receive a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes. The sidelink synchronization component1108may perform sidelink synchronization in accordance with a priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the scheduling for the one or more network energy saving modes and the mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

The reception component1102may receive a network energy saving mode change notification.

The sidelink synchronization component1108may switch from the priority rule, of the plurality of priority rules for sidelink synchronization, to another priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the network energy saving mode change notification.

The sidelink synchronization component1108may switch from the priority rule, of the plurality of priority rules for sidelink synchronization, to another priority rule of the plurality of priority rules for sidelink synchronization based at least in part on expiration of a time window for validity of the priority rule.

The reception component1102may receive an updated mapping indication that indicates an updated mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

The sidelink synchronization component1108may switch from the priority rule, of the plurality of priority rules for sidelink synchronization, to another priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the updated mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

The transmission component1104may transmit a sidelink communication that includes the mapping indication.

FIG.12is a diagram of an example apparatus1200for wireless communication, in accordance with the present disclosure. The apparatus1200may be a network node, or a network node may include the apparatus1200. In some aspects, the apparatus1200includes a reception component1202and a transmission component1204, which may be in communication with one another (for example, via one or more buses and/or one or more other components). As shown, the apparatus1200may communicate with another apparatus1206(such as a UE, a base station, or another wireless communication device) using the reception component1202and the transmission component1204. As further shown, the apparatus1200may include the communication manager150. The communication manager150may include a determination component1208, among other examples.

The transmission component1204may transmit a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization by a UE. The transmission component1204may transmit a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes.

The determination component1208may determine the mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

The transmission component1204may transmit a network energy saving mode change notification.

The transmission component1204may transmit an updated mapping indication that indicates an updated mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

Aspect 1: A method of wireless communication performed by a user equipment (UE), comprising: receiving a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization; receiving a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes; and performing sidelink synchronization in accordance with a priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the scheduling for the one or more network energy saving modes and the mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

Aspect 2: The method of Aspect 1, wherein each priority rule, of the plurality of priority rules, indicates priorities for a set of sidelink synchronization sources, and wherein performing sidelink synchronization in accordance with a priority rule of the plurality of priority rules comprises: performing sidelink synchronization based at least in part on a sidelink synchronization source, of the set of sidelink synchronization sources, in accordance with the priorities for the set of sidelink synchronization sources indicated by the priority rule.

Aspect 3: The method of any of Aspects 1-2, wherein receiving the mapping indication comprises: receiving, from a network node, a system information block (SIB) that includes the mapping indication.

Aspect 4: The method of any of Aspects 1-2, wherein receiving the mapping indication comprises: receiving, from a network node, a radio resource control (RRC) message that includes the mapping indication.

Aspect 5: The method of any of Aspects 1-2, wherein receiving the mapping indication comprises: receiving, from another UE, a sidelink communication that includes the mapping indication.

Aspect 6: The method of Aspect 5, wherein the mapping indication is included in sidelink control information (SCI), a dedicated physical sidelink control channel (PSSCH) communication, a sidelink wake-up signal (SL-WUS), a PC5 medium access control (MAC) control element (MAC-CE), a PC5 radio resource control (RRC) message, or a sidelink broadcast channel communication.

Aspect 7: The method of any of Aspects 1-6, wherein the priority rule, of the plurality of priority rules, is associated with a current network energy saving mode.

Aspect 8: The method of any of Aspects 1-7, wherein the priority rule, of the plurality of priority rules, is based at least in part on a current network energy saving mode and one or more future network energy saving modes indicated by the network energy saving mode indication.

Aspect 9: The method of Aspect 8, wherein the one or more future network energy saving modes include one or more future network energy saving modes scheduled in a time window from a current time.

Aspect 10: The method of any of Aspects 1-9, further comprising: receiving a network energy saving mode change notification; and switching from the priority rule, of the plurality of priority rules for sidelink synchronization, to another priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the network energy saving mode change notification.

Aspect 11: The method of any of Aspects 1-10, further comprising: switching from the priority rule, of the plurality of priority rules for sidelink synchronization, to another priority rule of the plurality of priority rules for sidelink synchronization based at least in part on expiration of a time window for validity of the priority rule.

Aspect 12: The method of any of Aspects 1-11, further comprising: receiving an updated mapping indication that indicates an updated mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization; and switching from the priority rule, of the plurality of priority rules for sidelink synchronization, to another priority rule of the plurality of priority rules for sidelink synchronization based at least in part on the updated mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.

Aspect 13: The method of Aspect 12, wherein the updated mapping indication is included in sidelink control information (SCI), a dedicated physical sidelink control channel (PSSCH) communication, a sidelink wake-up signal (SL-WUS), a PC5 medium access control (MAC) control element (MAC-CE), or a PC5 radio resource control (RRC) message.

Aspect 14: The method of any of Aspects 1-13, further comprising: transmitting a sidelink communication that includes the mapping indication.

Aspect 15: A method of wireless communication performed by a network node, comprising: transmitting a mapping indication that indicates a mapping between a plurality of network energy saving modes and a plurality of priority rules for sidelink synchronization by a user equipment (UE); and transmitting a network energy saving mode indication that indicates scheduling for one or more network energy saving modes of the plurality of network energy saving modes.

Aspect 16: The method of Aspect 15, wherein each priority rule, of the plurality of priority rules, indicates priorities for a set of sidelink synchronization sources.

Aspect 17: The method of any of Aspects 15-16, wherein transmitting the mapping indication comprises: transmitting a system information block (SIB) that includes the mapping indication.

Aspect 18: The method of any of Aspects 15-16, wherein transmitting the mapping indication comprises: transmitting a radio resource control (RRC) message that includes the mapping indication.

Aspect 19: The method of any of Aspects 15-18, further comprising: transmitting a network energy saving mode change notification.

Aspect 20: The method of any of Aspects 15-19, further comprising: transmitting an updated mapping indication that indicates an updated mapping between the plurality of network energy saving modes and the plurality of priority rules for sidelink synchronization.