WO2025038237A1

WO2025038237A1 - Standalone sidelink channel state information reference signal

Info

Publication number: WO2025038237A1
Application number: PCT/US2024/038447
Authority: WO
Inventors: Chunxuan Ye; Dawei Zhang; Wei Zeng; Huaning Niu; Hong He; Jie Cui; Haitong Sun
Original assignee: Apple Inc
Current assignee: Apple Inc
Priority date: 2023-08-11
Filing date: 2024-07-18
Publication date: 2025-02-20
Anticipated expiration: 2026-02-11

Abstract

Systems, methods, and processors are provided for processing standalone sidelink channel state information reference signals (SL-CSI-RS). In one example, a user equipment (UE) includes a memory and a baseband processor. The baseband processor configured to, when executing instructions stored in the memory, cause the UE to transmit, to a receiving UE, one or more standalone sidelink channel state information reference signals (SL-CSI-RS) in a slot that does not carry SL data.

Description

STANDALONE SIDELINK CHANNEL STATE INFORMATION REFERENCE

SIGNAL

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority from U.S. Provisional Patent Application 63/518,900 filed on August 11, 2023, entitled “STANDALONE SIDELINK CHANNEL STATE INFORMATION REFERENCE SIGNAL” the contents of which are incorporated by reference in their entirety.

BACKGROUND

[0002] The present disclosure relates generally to wireless communication and more specifically to techniques for performing sidelink or device-to- device communication in a radio network.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Some examples of circuits, apparatuses and/or methods will be described in the following by way of example only. In this context, reference will be made to the accompanying figures.

[0004] FIG. 1 is a diagram of an example of a sidelink beam pairing process between two user equipments (UEs), in accordance with various aspects described.

[0005] FIG. 2 is a flow diagram outlining an example sidelink beam pairing process that may be performed prior to establishment of a unicast link, in accordance with various aspects described.

[0006] FIG. 3 illustrates an example slot configuration for carrying standalone sidelink channel state information reference signals (SL-CSI-RS), in accordance with various aspects described. [0007] FIG. 4 illustrates another example slot configuration for carrying standalone sidelink channel state information reference signals (SL-CSI-RS), in accordance with various aspects described.

[0008] FIG. 5 is a flow diagram outlining an example method that may be performed by a transmitting (TX) UE for sidelink beam pairing, in accordance with various aspects described.

[0009] FIG. 6 is a flow diagram outlining an example method that may be performed by a receiving (RX) UE for sidelink beam pairing, in accordance with various aspects described.

[0010] FIG. 7 is a functional block diagram of a wireless communication network, in accordance with various aspects described.

[0011] FIG. 8 illustrates a simplified block diagram of a user equipment device, in accordance with various aspects described.

DETAILED DESCRIPTION

[0012] The present disclosure is described with reference to the attached figures. The figures are not drawn to scale and they are provided merely to illustrate the disclosure. Several aspects of the disclosure are described below with reference to example applications for illustration. Numerous specific details, relationships, and methods are set forth to provide an understanding of the disclosure. The present disclosure is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the selected present disclosure.

[0013] Beamforming is an important aspect of new radio (NR) communication in high frequency bands (e.g., frequency range 2 (FR2). FIG. 1 illustrates an example three phase sidelink beam pairing process that may be performed to select sidelink beams. The selection of sidclink beams may be referred to herein interchangeably with “beam pairing”. In the first two phases of beam pairing, a TX UE transmits reference signals (e.g., sidelink synchronization signal block (S-SSB) or SL-CSI-RS) using different beams and an RX UE identifies a received reference signal that meets some predetermined selection criteria. The RX UE may compare reference signal received power (RSRP) measurements made on the received reference signals associated with the different beams and select a reference signal having the highest RSRP that also exceeds an RSRP threshold. The beam associated with the selected reference signal is determined to have been optimally received and the UE RX reports this “optimal” or “best” beam (as identified by an associated S-SSB resource indicator (SSBRI) or SL-CSI-RS resource indicator (S-CR1) to the TX UE.

[0014] During the first phase, TX wide beam selection, a TX UE 110 transmits S-SSBs on wide TX beams. An RX UE 120 uses a wide RX beam to receive the S-SSBs and determines which S-SSB is optimally received. In the illustrated example, the RX UE 120 selects the wide beam associated with S-SSB2 as the optimal wide beam. The RX UE 120 reports the optimal beam. During the second phase, TX narrow beam selection, the TX UE 110 transmits SL-CSI- RS on narrow beams that overlap spatially with the selected wide beam. The RX UE reports the optimal narrow beam. In the illustrated example, the RX UE 120 selects SL-CSI-RS0. During an optional RX beam refinement process, the TX UE 110 transmits repeated SL-CSI-RS on the selected narrow beam for use by the RX UE 120 in selecting its optimal RX beam. In the illustrated example, the RX UE 120 selects RX beam 2 for receiving sidelink messages from the TX UE 110 that are transmitted on TX beam SL-CSI-RS0.

[0015] In Uu link communication, a UE selects and maintains beams with a limited number of base stations or access points. However, in sidelink communication, a UE may have many more potential communication partners, meaning that signaling involved with beam pairing may become burdensome. To reduce signaling overhead, the beam pairing process of FIG. 1 may not be initiated by a TX UE with respect to a given RX UE until the TX UE determines that a unicast link with the RX UE is to be established. In this approach, a TX/RX beam pair may be selected just prior to the exchange of unicast link establishment messages, which will be transmitted/received using the selected beam pair. This avoids unnecessary beam pairing and the associated signaling with RX UEs with which a unicast link is not going to be established in the near term.

[0016] One issue that arises when the narrow TX beam selection phase and the optional RX beam refinement phase of FIG. 1 arc performed prior to establishment of a unicast link with the RX UE is that the TX UE does not yet intend to transmit data to the RX UE. This means that slots that carry the SL-CSI-RS should not be structured to also carry sidelink data (e.g., media access control service data units (MAC SDU)). Thus, standalone SL-CSI-RS, which is SL-CSI- RS transmitted in a slot that does not also include sidelink data, should be configured for use in beam pairing that is performed prior to unicast link establishment. Described herein are various aspects of a standalone SL-CSI-RS that may be used in sidelink beam pairing performed prior to establishment of a unicast link.

[0017] Certain parameters associated with sidelink communication may be disclosed herein as being “pre-configured or configured”. In NR, it is possible that a UE performing sidelink communication is not in the coverage of a network. In these circumstances, there may be no network configuration of sidclink communication parameters. When no network configuration has been made, both UEs may apply “pre-configured” parameter values. The pre-configured parameter values are “built-in” or programmed into a UE when it is manufactured. This preconfigured set of parameter values will remain the same for a UE and are used by the UE when there is no network coverage (or there is no configured parameter value from the network). Thus, when a parameter value or other quantity associated with sidelink communication is described as being “pre-configured or configured”, it means that the parameter value may be at some times a “pre-configured” value and at other times a network “configured” value.

[0018] FIG. 2 is a message flow diagram outlining an example exchange of messages between a TX UE 210 and an RX UE 220 as part of a beam pairing process that is performed prior to establishment of a unicast link between the TX UE 210 and the RX UE 220. At 215 the TX UE 210 determines that a unicast link with RX UE 220 is to be established. The TX UE 210 obtains a source identifier (ID) for use in communicating with the RX UE 220 and a destination ID for the RX UE 220. The source and destination ID information will be used to uniquely identify unicast messages exchanged during unicast communication between the TX UE 210 and the RX UE 220.

[0019] To initiate the sidelink beam pairing process with RX UE 220, the TX UE 210 transmits one or more standalone SL-CSI-RS 225 on one or more TX beams. In the illustrated example, three TX beams are used to transmit standalone SL-CSI-RS. When the RX UE 220 receives any of the standalone SL-CSI-RS 225, at 230 the RX UE checks a destination ID and a source ID associated with the standalone SL-CSI-RS. The destination ID and source ID associated with the standalone SL-CSI-RS may be indicated, for example, in a physical sidelink control channel (PSCCH) message, such as single-stage or two stage sidelink control information (SCI), included in a slot that carries the standalone SL-CSI-RS. The SCI may also indicate a periodicity of the standalone SL-CSI-RS, the time and frequency resources of the standalone SL- CSI-RS, or activate configured or pre-configured semi-persistent standalone SL-CSI-RS. Alternatively, the destination ID and/or the source ID may be encoded in the standalone SL-CSI- RS itself (e.g., via an initialization value used to generate the standalone SL-CSI-RS). In other examples, the source ID and/or destination ID are indicated in S-SSB.

[0020] The RX UE 220 checks the destination ID associated with the standalone SL-CSI-RS to determine if the destination ID identifies the RX UE 220. If so, the RX UE 220 checks a source ID associated with the standalone SL-CSI-RS to determine if the RX UE is configured for sidelink communication with the TX UE 210. For example, the RX UE 220 may be configured with a white list of configured sidelink partner UEs with which it is expected to communicate. If the RX UE 220 is configured to communicate with the TX UE 210, the RX UE may proceed to measure the standalone SL-CSI-RS at 240. In this manner, the RX UE conserves resources by only measuring standalone SL-CSI-RS when the standalone SL-CSI-RS are meant for the RX UE and are received from an approved TX UE.

[0021] The RX UE 220 may perform a RSRP measurement on the received standalone SL- CSI-RS(s) and select an optimal TX beam from amongst the TX beams used to transmit the standalone SL-CSI-RS. For example, the RX UE 220 may determine which, if any, of the received standalone SL-CSI-RS are above a given threshold and select one of those TX beams or select a TX beam associated with the standalone SL-CSI-RS that has a largest RSRP, independent of a minimum RSRP threshold. The RX UE 220 transmits a beam report message 250 to the TX UE 210. The beam report message indicates the selected optimal TX beam by, for example, indicating the corresponding standalone SL-CSI-RS or an associated S-SSB. The beam reporting message 250 may also indicate a source ID of the RX UE 220 or a destination ID of the TX UE 210. [0022] The TX UE 210 uses the TX beam indicated in the beam report message 250 to exchange unicast establishment messages 260 with the RX UE 220. One example of a unicast establishment message is a direct communication request (DCR) message. When the RX UE is capable of receiving using narrow RX beams, the TX UE 210 may transmit repeated standalone SL-CSI-RS 270 on the TX beam indicated in the beam report message 250. The RX UE 220 switches RX beams to determine which RX beam best receives the repeated standalone SL-CSI- RS. In other examples, the RX UE 220 may select a narrow RX beam that corresponds to the selected TX beam or a wide RX beam that corresponds to an S-SSB that spatially overlaps the selected TX beam. At 280, the RX UE 220 selects and tunes to the selected RX beam for receiving unicast messages from the TX UE 210.

Slot Structure for Standalone SL-CSI-RS

[0023] FIG. 3 illustrates an example dedicated slot structure for transmitting standalone SL- CSI-RS. The dedicated slots may be pre-configured or configured based on a resource pool or as part of a sidelink bandwidth part (SL-BWP) configuration. The dedicated slots may be preconfigured or configured to occur periodically.

[0024] Two dedicated slots 310, 320 are illustrated in FIG. 3 and each slot includes three sub-channels that carry standalone SL-CSI-RS. It can be seen that the slot structure within the sub-channels does not include physical sidelink shared channel (PSSCH) allocations. The bandwidth of the sub-channels may be separately configurable and may be either the same or different from a bandwidth of any sub-channel that carries SL data outside the dedicated slot. The bandwidth of the sub-channels may be pre-configured or configured by separate resource pools or SL-BWP configuration. In some examples, each sub-channel is used to carry standalone SL-CSI-RS between different TX UE/RX UE pairs. The dedicated slots may not include physical sidelink feedback channel (PSFCH) resources.

[0025] The example slot structure of FIG. 3 arranges the transmission of standalone SL-CSI- RS into sessions. During the second phase of beam pairing, narrow TX beam selection, the symbols in each session in a slot may be transmitted using a different transmit beam. During the third phase of beam pairing, narrow RX beam selection, the symbols in each session in a slot may be transmitted using the same transmit beam. [0026] In slot 310, in sub-channel (1) TX UE 1 transmits a first standalone SL-CSI-RS session 312 on TX Beam (1) of TX UE 1 and a second standalone SL-CSI-RS session 314 on TX Beam (2) of TX UE 1. In sub-channel (3), TX UE 3 transmits a first standalone SL-CSI-RS session 316 on TX Beam (1) of TX UE 3 and a second standalone SL-CSI-RS session 318 on TX Beam (2) of TX UE 3. In slot 320, in sub-channel (1) TX UE 1 transmits a first standalone SL- CSI-RS session 322 on TX Beam (1) of TX UE 1 and a second standalone SL-CSI-RS session 324 on TX Beam (2) of TX UE 1. In sub-channel (2), TX UE 2 transmits a first standalone SL- CSI-RS session 326 on TX Beam (1) of TX UE 2

[0027] The same TX beam is used to transmit all symbols in a standalone SL-CSI-RS session. Each session includes an automatic gain control (AGC) symbol followed by one or more PSCCH symbols. The number of PSCCH symbols in a session may be pre-configured or configured (e.g., either 1, 2, or 3). The PSCCH may carry single-stage SCI that indicates, for the particular session, a source ID for the TX UE, a destination ID for the RX UE, a priority of the standalone SL-CSI-RS, time and frequency resource for the standalone SL-CSI-RS, a beam ID associated with the standalone SL-CSI-RS (e.g., a SL-CRI or transmission configuration indicator (TCI) state), and a periodicity of the standalone SL-CSI-RS. The periodicity of the standalone SL-CSI-RS may be indicated as a function of the periodicity of the dedicated slots. For example, the standalone SL-CSI-RS of the TX beam (1) and TX beam (2) sessions in subchannel 1 may be indicated as having a periodicity of 1 or occurring every dedicated slot. The periodicity of the standalone SL-CSI-RS of the TX beam (1) and TX beam (2) sessions in subchannel 3 and the TX beam (1) session in sub-channel 2 may be indicated as having a periodicity of X and Y, respectively, or occurring every Xth or Yth dedicated slot. As can be seen in dedicated slot 320 on sub-channel 2, not all sub-channels must include standalone SL-CSI-RS in all possible sessions (on all possible TX beams), for example, when certain TX beams are known to not be receivable by a given RX UE.

[0028] One or more standalone SL-CSI-RS symbols follow the AGC symbol and PSCCH symbols in each standalone SL-CSI-RS session. The number of standalone SL-CSI-RS symbols in a session may be pre-configured or configured (e.g., between 1-11). A gap symbol follows the standalone SL-CSI-RS symbols to allow the TX UE to tune to a different beam. In some examples, the gap symbol is not used. It is noted that when multiple sessions occur in a same slot, the slot will include additional AGC and/or gap symbols in symbols other than a first or last symbol

[0029] FIG. 4 illustrates an alternative dedicated slot structure 410 for carrying standalone SL-CSI-RS. The slot 410 includes one or more gap symbols between the PSCCH symbols and the standalone SL-CSI-RS symbols to allow an RX UE to process the SCI carried by the PSCCH symbols and use the information to receive the standalone SL-CSI-RS.

Additional Design Considerations for Standalone SL-CSI-RS

[0030] Some additional design considerations for standalone SL-CSI-RS arise due to the fact that the standalone SL-CSI-RS is not transmitted with PSSCH. These considerations include the generation of a scrambling sequence for the standalone SL-CSI-RS, frequency resource selection for the standalone SL-CSI-RS, and power control for the standalone SL-CSI-RS.

[0031] Non-standalone SL-CSI-RS is scrambled using a sequence that is generated based on an initialization value. The initialization value is based on N^X _D, which corresponds to X bits of a decimal representation of a cyclic redundancy code (CRC) for the SCI mapped to a PSCCH associated with the SL-CSI-RS. This non-standalone SL-CSI-RS initialization value calculation may serve as a basis for calculating a an initialization value for standalone SL-CSI-RS. For example, N^X _D for a standalone SL-CSI-RS sequence may correspond to X least significant bits of a CRC for the SCI in the session, X least significant bits of a source ID for the standalone SL- CSI-RS, X least significant bits for destination ID of the standalone SL-CSI-RS, X bits selected from the source ID and the destination ID, and so on. In some examples, X is 10.

[0032] Time and frequency resources for standalone SL-CSI-RS for a given RX UE may be selected by the TX UE. The TX UE first identifies some candidate resources for standalone SL- CSI-RS at the physical layer, based on sensing and a resource selection procedure. Within a resource selection window, the total number of initial candidates can be calculated based on a number of dedicated slots for standalone SL-CSI-RS in the resource selection window and the number of sub-channels of the resource pool. Only a certain percentage or ratio of the total number of initial candidate resources is selected at the physical layer and reported to the higher layer. This percentage or ratio may be a same ratio as is pre-configured or configured for sidelink data transmission resources or the percentage or ratio may be separately configured from a ratio used for sidelink data transmission resources. A sub-channel that corresponds to a maximum RSRP measurement among all PSCCH demodulation reference signal (DMRS) sessions may be selected for each RX UE. In some examples, a sensing window used for resource selection is pre-configured or configured and may be selected to be no shorter than a largest resource selection interval of non-standalone SL-CSI-RS.

[0033] In some examples, a SL-CSI-RS resource is excluded from the set of candidate resources if it has been reserved by other UEs and the RSRP measurement of the resource exceeds an RSRP threshold to be considered for transmission of standalone SL-CSI-RS. In this case, a sub-channel that has a maximum RSRP from amongst sub-channels having RSRP above the RSRP threshold is selected for transmission of standalone SL-CSI-RS. The RSRP threshold may be determined based on an initial RSRP threshold selected from a pre-configured or configured initial RSRP threshold list. The pre-configured or configured initial RSRP threshold list may be the same list as used for sidelink data transmission or the initial RSRP threshold list may be pre-configured or configured separately from an initial RSRP threshold list used for sidelink data transmission. The initial RSRP threshold may be incremented up by a preconfigured or configured increment step when more than one sub-channel exceed the threshold or incremented down when no sub-channels exceed the threshold. The increment step may be pre-configured, configured, or fixed (in hardware or by specification) at 3 dB. Resource re- evaluation and pre-emption checking may also be applied during selection of frequency resources for standalone SL-CSI-RS.

[0034] The transmission power level for non-standalone SL-CSI RS is determined based on the power of associated PSSCH. Lor standalone SL-CSI-RS, the power may also be determined based on the power of the associated PSCCH as follows:

If si — P0 — PSSCH — PSCCH is provided, PPSCCH,SL ( )

Else, PPSCCH,SL (P) ^{= m}i-ⁿ(.PcMAX’ PPSCCH,D ) where Mfg^CCH (i) is the number of resource blocks (RBs) allocated for PSCCH transmission. It is noted that the path loss PL_D( ) and PL_SL (L) may depend on TX beam direction.

[0035] FIG. 5 is a flow diagram outlining an example method 500 that may be performed by a TX UE (e.g., TX UE 110 of FIG. 1 or 210 of FIG. 2) to determine a TX beam for use in unicast communication with an RX UE (e.g., RX UE 120 of FIG. 1 or 220 of FIG. 2) with which a unicast link has not yet been established. Messages that may be exchanged with the RX UE during performance of the method 500 are illustrated in FIG. 2.

[0036] The method includes, at 510, determining to initiate a unicast link with an RX UE. For example, the TX UE may receive a broadcast request from an out of coverage RX UE to serve as a relay UE for the RX UE or receive an instruction from the network to communicate with the RX UE for platooning purposes.

[0037] At 520, the TX UE transmits standalone SL-CSI-RS on one or more TX beams in a slot. Standalone SL-CSI-RS are SL-CSI-RS carried in a slot that does not also carry sidelink data. Example slot configurations are illustrated in FIGs. 3 and 4. The slot may be a dedicated slot that is pre-configured or configured in a resource pool or in an SL BWP. A sub-channel size of the frequency resources is pre-configured or configured in the resource pool or the SL-BWP and a set of frequency resources of the slot may be divided into sub-channels, with each subchannel associated with a different transmitting UE or receiving UE. In some examples, the slot does not include resources for PSFCH transmissions.

[0038] The slot may include one or more standalone SL-CSI-RS sessions in the slot, with each symbol in a given standalone SL-CSI-RS session being transmitted using the same TX beam. Each standalone SL-CSI-RS session in a slot may be transmitted using a same or different TX beams. For example different TX beams are used to transmit different standalone SL-CIS- RS sessions during the TX narrow beam selection of FIG. 1, while each standalone SL-CSI-RS session in a slot is transmitted using the same TX beam in RX beam refinement of FIG. 1. Each standalone SL-CSI-RS session may include one or more PSCCH symbols corresponding to SCI and one or more standalone SL-CSI-RS symbols after the one or more PSCCH symbols. The SCI may indicate one or more of a source ID, a destination ID, a periodicity of standalone SL- CSI-RS in the session, time and frequency resources of standalone SL-CSI-RS in the session, a priority of standalone SL-CSI-RS in the session, or an indication of a TX beam used to transmit standalone SL-CSI-RS in the session. As illustrated in FIG. 4, at least one standalone SL-CSI- RS session in the slot may include a gap between the one or more PSCCH symbols and the one or more standalone SL-CSI-RS symbols. Each standalone SL-CSI-RS session may include an automatic gain control (AGC) symbol at a beginning of the session or a gap symbol at an end of the session.

[0039] A standalone SL-CSI-RS sequence may be based on a non- standalone SL-CSI-RS sequence in which an initialization value is based on ten least significant bits (LSBs) of a cyclic redundancy code (CRC) of SCI for the standalone SL-CSI-RS; ten LSBs of a source ID of the standalone SL-CSI-RS, 10 LSBs of a destination ID for the standalone SL-CSI-RS, or a combination of bits of the source ID and the destination ID.

[0040] The method may include selecting time and frequency resources of the standalone SL-CSLRS based on a maximum reference signal received power (RSRP) measurement from among physical sidelink control channel (PSCCH) demodulation reference signals (DMRS) transmitted by the UE. A sensing window for resource selection may be pre-configured, configured, or selected to be at least as long as a largest resource reservation interval of non- standalone SL-CSI-RS. An RSRP threshold used in resource selection may be based on an initial RSRP threshold list. The initial RSRP threshold list is the same as an initial RSRP threshold list that is pre-configured or configured for sideline data transmission or is different from the initial RSRP threshold list that is pre-configured or configured for sideline data transmission. The RSRP threshold may be based on an RSRP threshold increment step, that is fixed by hardware to be 3 dB, pre-configured, or configured. A ratio of candidate resources for the time resources and frequency resources for standalone SL-CSI-RS may be pre-configured or configured as a same ratio as for sidelink data transmissions or may be pre-configured or configured separately from a ratio for sidelink data transmissions. The method may include reevaluating time and frequency resources used for the standalone SL-CSI-RS or, prior to selecting the time and frequency resources, checking candidate time and frequency resources for standalone SL-CSI-RS for pre-emption by higher priority signals. The method may include transmitting the standalone SL-CSI-RS using a same power as used for PSCCH transmission.

[0041] At 530, the method includes receiving, from the RX UE, a beam report message indicating one of the TX beams used to transmit the standalone SL-CSI-RS. At 540, the indicated TX beam is used to transmit beam establishment messages (e.g., DCR message) with the RX UE.

[0042] FIG. 6 is a flow diagram outlining an example method 600 that may be performed by an RX UE (e.g., RX UE 120 of FIG. 1 or 220 of FIG. 2) to determine a TX beam for use by a TX UE (e.g., TX UE 110 of FIG. 1 or 210 of FIG. 2) in unicast communication when a unicast link between the RX UE and the TX UE has not yet been established. Messages that may be exchanged with the RX UE during performance of the method 600 are illustrated in FIG. 2.

[0043] The method includes, at 610, receiving standalone SL-CSI-RS on one or more TX beams in a slot. Standalone SL-CSI-RS are SL-CSI-RS carried in a slot that does not also carry sidelink data. Example slot configurations are illustrated in FIGs. 3 and 4. The slot may be a dedicated slot that is pre-configured or configured in a resource pool or in an SL bandwidth part (BWP). A sub-channel size of the frequency resources is pre-configured or configured in the resource pool or the SL-BWP and a set of frequency resources of the slot may be divided into sub-channels, with each sub-channel associated with a different transmitting UE or receiving UE. In some examples, the slot does not include resources for physical sidelink feedback channel (PSFCH) transmissions.

[0044] The slot may include one or more standalone SL-CSI-RS sessions in the slot, with each symbol in a given standalone SL-CSI-RS session being transmitted using the same TX beam. Each standalone SL-CSI-RS session in a slot may be transmitted using a same or different TX beams. For example different TX beams are used to transmit different standalone SL-CIS- RS sessions during the TX narrow beam selection of FIG. 1, while each standalone SL-CSI-RS session in a slot is transmitted using the same TX beam in RX beam refinement of FIG. 1. Each standalone SL-CSI-RS session may include one or more PSCCH symbols corresponding to sidelink control information (SCI) and one or more standalone SL-CSI-RS symbols after the one or more PSCCH symbols. The SCI may indicate one or more of a source identifier (ID), a destination UE ID, a periodicity of standalone SL-CSI-RS in the session, time and frequency resources of standalone SL-CSI-RS in the session, a priority of standalone SL-CSI-RS in the session, or an indication of a TX beam used to transmit standalone SL-CSI-RS in the session. As shown in FIG. 4, at least one standalone SL-CSI-RS session in the slot may include a gap between the one or more PSCCH symbols and the one or more standalone SL-CSI-RS symbols. Each standalone SL-CSI-RS session may include an automatic gain control (AGC) symbol at a beginning of the session or a gap symbol at an end of the session.

[0045] A standalone SL-CSI-RS sequence may be based on a non- standalone SL-CSI-RS sequence in which an initialization value is based on ten least significant bits (LSBs) of a cyclic redundancy code (CRC) of SCI for the standalone SL-CSI-RS; ten LSBs of a source ID of the standalone SL-CSI-RS, 10 LSBs of a destination ID for the standalone SL-CSI-RS, or a combination of bits of the source ID and the destination ID.

[0046] At 620, the RX UE checks a source ID and a destination ID associated with the standalone SL-CSI-RS to determine whether the standalone SL-CSI-RS is meant for the RX UE and whether the TX UE is a configured/approved sidelink partner for the RX UE. For example, the RX UE may be preconfigured or configured with a whitelist of TX UEs that is checked against the source ID. If these conditions are met, at 630, the RX UE measures the one or more received standalone SL-CSI-RS and selects a TX beam based on the measurements. The RX UE may select a TX beam associated with a standalone SL-CSI-RS that has a highest RSRP.

[0047] At 640, the method includes transmitting, to the TX UE, a beam report message indicating one of the TX beams used to transmit the standalone SL-CSI-RS. At 650, the RX UE receives beam establishment messages from the TX UE. The beam establishment messages may be received using an RX beam corresponding to or otherwise based on the selected TX beam.

[0048] Above are several flow diagrams outlining example methods and exchanges of messages. In this description and the appended claims, use of the term “determine” with reference to some entity (e.g., parameter, variable, and so on) in describing a method step or function is to be construed broadly. For example, “determine” is to be construed to encompass, for example, receiving and parsing a communication that encodes the entity or a value of an entity. “Determine” should be construed to encompass accessing and reading memory (e.g., lookup table, register, device memory, remote memory, and so on) that stores the entity or value for the entity. “Determine” should be construed to encompass computing or deriving the entity or value of the entity based on other quantities or entities. “Determine” should be construed to encompass any manner of deducing or identifying an entity or value of the entity.

[0049] As used herein, the term identify when used with reference to some entity or value of an entity is to be construed broadly as encompassing any manner of determining the entity or value of the entity. For example, the term identify is to be construed to encompass, for example, receiving and parsing a communication that encodes the entity or a value of the entity. The term identify should be construed to encompass accessing and reading memory (e.g., device queue, lookup table, register, device memory, remote memory, and so on) that stores the entity or value for the entity.

[0050] As used herein, the term encode when used with reference to some entity or value of an entity is to be construed broadly as encompassing any manner or technique for generating a data sequence or signal that communicates the entity to another component.

[0051] As used herein, the term select when used with reference to some entity or value of an entity is to be construed broadly as encompassing any manner of determining the entity or value of the entity from amongst a plurality or range of possible choices. For example, the term select is to be construed to encompass accessing and reading memory (e.g., lookup table, register, device memory, remote memory, and so on) that stores the entities or values for the entity and returning one entity or entity value from amongst those stored. The term select is to be construed as applying one or more constraints or rules to an input set of parameters to determine an appropriate entity or entity value. The term select is to be construed as broadly encompassing any manner of choosing an entity based on one or more parameters or conditions.

[0052] As used herein, the term derive when used with reference to some entity or value of an entity is to be construed broadly. “Derive” should be construed to encompass accessing and reading memory (e.g., lookup table, register, device memory, remote memory, and so on) that stores some initial value or foundational values and performing processing and/or logical/mathematical operations on the value or values to generate the derived entity or value for the entity. The term derive should be construed to encompass computing or calculating the entity or value of the entity based on other quantities or entities. The term derive should be construed to encompass any manner of deducing or identifying an entity or value of the entity.

[0053] As used herein, the term indicate when used with reference to some entity (e.g., parameter or setting) or value of an entity is to be construed broadly as encompassing any manner of communicating the entity or value of the entity either explicitly or implicitly. For example, bits within a transmitted message may be used to explicitly encode an indicated value or may encode an index or other indicator that is mapped to the indicated value by prior configuration. The absence of a field within a message may implicitly indicate a value of an entity based on prior configuration.

[0054] FIG. 7 is an example network 700 according to one or more implementations described herein. Example network 700 may include UEs 710-1, 710-2, etc. (referred to collectively as “UEs 710” and individually as “UE 710”), a radio access network (RAN) 720, a core network (CN) 730, application servers 740, and external networks 750.

[0055] The systems and devices of example network 700 may operate in accordance with one or more communication standards, such as 2nd generation (2G), 3rd generation (3G), 4th generation (4G) (e.g., long-term evolution (LTE)), and/or 5th generation (5G) (e.g., new radio (NR)) communication standards of the 3rd generation partnership project (3GPP). Additionally, or alternatively, one or more of the systems and devices of example network 700 may operate in accordance with other communication standards and protocols discussed herein, including future versions or generations of 3GPP standards (e.g., sixth generation (6G) standards, seventh generation (7G) standards, etc.), institute of electrical and electronics engineers (IEEE) standards (e.g., wireless metropolitan area network (WMAN), worldwide interoperability for microwave access (WiMAX), etc.), and more.

[0056] As shown, UEs 710 may include smartphones (e.g., handheld touchscreen mobile computing devices connectable to one or more wireless communication networks). Additionally, or alternatively, UEs 710 may include other types of mobile or non-mobile computing devices capable of wireless communications, such as personal data assistants (PDAs), pagers, laptop computers, desktop computers, wireless handsets, watches etc. In some implementations, UEs 710 may include internet of things (loT) devices (or loT UEs) that may comprise a network access layer designed for low-power loT applications utilizing short-lived UE connections. Additionally, or alternatively, an loT UE may utilize one or more types of technologies, such as machine-to-machine (M2M) communications or machine-type communications (MTC) (e.g., to exchanging data with an MTC server or other device via a public land mobile network (PLMN)), proximity-based service (ProSe) or device-to-device (D2D) communications, sensor networks, loT networks, and more. Depending on the scenario, an M2M or MTC exchange of data may be a machine-initiated exchange, and an loT network may include interconnecting loT UEs (which may include uniquely identifiable embedded computing devices within an Internet infrastructure) with short-lived connections. In some scenarios, loT UEs may execute background applications (e.g., keep-alive messages, status updates, etc.) to facilitate the connections of the loT network.

[0057] UEs 710 may use stored standalone SL-CSI-RS instructions and information for performing one or more of the solutions disclosed with reference to FIGs. 1-6 to utilize standalone SL-CSI-RS in establishing a beamformed connection with one or more other UEs 710 via one or more wireless channels 712, each of which may comprise a physical communications interface I layer. The connection may include an M2M connection, MTC connection, D2D connection, SL connection, etc. The connection may involve a PC5 interface. In some implementations, UEs 710 may be configured to discover one another, negotiate wireless resources between one another, and establish connections between one another, without intervention or communications involving RAN node 722 or another type of network node. In some implementations, discovery, authentication, resource negotiation, registration, etc., may involve communications with RAN node 722 or another type of network node.

[0058] UEs 710 may use one or more wireless channels 712 to communicate with one another. As described herein, UE 710-1 may transmit standalone SL-CSI-RS to UE 710-2 for use in selecting a TX beam for transmitting unicast establishment messages.

[0059] UEs 710 may communicate and establish a connection with (e.g., be communicatively coupled) with RAN 720, which may involve one or more wireless channels 714-1 and 714-2, each of which may comprise a physical communications interface / layer. [0060] As shown, UE 710 may also, or alternatively, connect to access point (AP) 716 via connection interface 718, which may include an air interface enabling UE 710 to communicatively couple with AP 716. AP 716 may comprise a wireless local area network (WLAN), WLAN node, WLAN termination point, etc. The connection 718 may comprise a local wireless connection, such as a connection consistent with any IEEE 702.11 protocol, and AP 716 may comprise a wireless fidelity (Wi-Fi®) router or other AP. While not explicitly depicted in FIG. 7, AP 716 may be connected to another network (e.g., the Internet) without connecting to RAN 720 or CN 730.

[0061] RAN 720 may include one or more RAN nodes 722-1 and 722-2 (referred to collectively as RAN nodes 722, and individually as RAN node 722) that enable channels 714-1 and 714-2 to be established between UEs 710 and RAN 720. RAN nodes 722 may include network access points configured to provide radio baseband functions for data and/or voice connectivity between users and the network based on one or more of the communication technologies described herein (e.g., 2G, 3G, 4G, 5G, WiFi, etc.). As examples therefore, a RAN node may be an E-UTRAN Node B (e.g., an enhanced Node B, eNodeB, eNB, 4G base station, etc.), a next generation base station (e.g., a 5G base station, NR base station, next generation eNBs (gNB), etc.). RAN nodes 722 may include a roadside unit (RSU), a transmission reception point (TRxP or TRP), and one or more other types of ground stations (e.g., terrestrial access points). In some scenarios, RAN node 722 may be a dedicated physical device, such as a macrocell base station, and/or a low power (LP) base station for providing femtocells, picocells or the like having smaller coverage areas, smaller user capacity, or higher bandwidth compared to macrocells.

[0062] The RAN nodes 722 may be configured to communicate with one another via interface 723. In implementations where the system is an LTE system, interface 723 may be an X2 interface. In NR systems, interface 723 may be an Xn interface. The X2 interface may be defined between two or more RAN nodes 722 (e.g., two or more eNBs I gNBs or a combination thereof) that connect to evolved packet core (EPC) or CN 730, or between two eNBs connecting to an EPC. [0063] As shown, RAN 720 may be connected (e.g., communicatively coupled) to CN 730. CN 730 may comprise a plurality of network elements 732, which are configured to offer various data and telecommunications services to customers/subscribers (e.g., users of UEs 710) who are connected to the CN 730 via the RAN 720. In some implementations, CN 730 may include an evolved packet core (EPC), a 5G CN, and/or one or more additional or alternative types of CNs. The components of the CN 730 may be implemented in one physical node or separate physical nodes including components to read and execute instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium

[0064] As shown, CN 730, application servers 740, and external networks 750 may be connected to one another via interfaces 734, 736, and 738, which may include IP network interfaces.

[0065] FIG. 8 is a diagram of an example of components of a network device (e.g., UE 110, 120, 210, 220, 710-, 710-2 of FIGs. 1, 2, and 7) according to one or more implementations described herein. In some implementations, the device 800 can include application circuitry 802, baseband circuitry 804, RF circuitry 806, front-end module (FEM) circuitry 808, one or more antennas 810, and power management circuitry (PMC) 812 coupled together at least as shown. In some implementations, the device 800 can include additional elements such as, for example, memory/storage, display, camera, sensor (including one or more temperature sensors, such as a single temperature sensor, a plurality of temperature sensors at different locations in device 800, etc.), or input/output (RO) interface.

[0066] The application circuitry 802 can include one or more application processors. For example, the application circuitry 802 can include circuitry such as, but not limited to, one or more single-core or multi-core processors. The processor(s) can include any combination of general-purpose processors and dedicated processors (e.g., graphics processors, application processors, etc.). The processors can be coupled with or can include memory/storage and can be configured to execute instructions stored in the memory/storage to enable various applications or operating systems to run on the device 800. In some implementations, processors of application circuitry 802 can process IP data packets received from an EPC. [0067] The baseband circuitry 804 can include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 804 can include one or more baseband processors or control logic to process baseband signals received from a receive signal path of the RF circuitry 806 and to generate baseband signals for a transmit signal path of the RF circuitry 806. Baseband circuity 804 can interface with the application circuitry 802 for generation and processing of the baseband signals and for controlling operations of the RF circuitry 806. For example, in some implementations, the baseband circuitry 804 can include a 3G baseband processor 804A, a 4G baseband processor 804B, a 5G baseband processor 804C, or other baseband processor(s) 804D for other existing generations, generations in development or to be developed in the future (e.g., 5G, 6G, etc.).

[0068] The baseband circuitry 804 (e.g., one or more of baseband processors 804A-D) can handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 806. In other implementations, some or all of the functionality of baseband processors 804A-D can be included in modules stored in the memory 804G and executed via a Central Processing Unit (CPU) 804E. In some implementations, the baseband circuitry 804 can include one or more audio digital signal processor(s) (DSP) 804F.

[0069] In some implementations, memory 804G may receive and/or store sidelink beamforming instructions and information that cause the device 800 to generate/transmit/receive/process standalone SL-CSI-RS as a TX UE and/or RX UE as disclosed with reference to FIGs 1-6.

[0070] RF circuitry 806 can enable communication with wireless networks using modulated electromagnetic radiation through a non- solid medium. In various implementations, the RF circuitry 806 can include switches, filters, amplifiers, etc. to facilitate the communication with the wireless network. RF circuitry 806 can include a receive signal path which can include circuitry to down-convert RF signals received from the FEM circuitry 808 and provide baseband signals to the baseband circuitry 804. RF circuitry 806 can also include a transmit signal path which can include circuitry to up-convert baseband signals provided by the baseband circuitry 804 and provide RF output signals to the FEM circuitry 808 for transmission. [0071] In some implementations, the receive signal path of the RF circuitry 806 can include mixer circuitry 806A, amplifier circuitry 806B and filter circuitry 806C. In some implementations, the transmit signal path of the RF circuitry 806 can include filter circuitry 806C and mixer circuitry 806A. RF circuitry 806 can also include synthesizer circuitry 806D for synthesizing a frequency for use by the mixer circuitry 806A of the receive signal path and the transmit signal path.

[0072] Examples herein can include subject matter such as a method, means for performing acts or blocks of the method, at least one non-volatile computer-readable medium including executable instructions that, when performed by a machine or circuitry (e.g., a baseband processor (e.g., processor , etc.) with memory, an application- specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like) cause the machine to perform acts of the method or of an apparatus or system for concurrent communication using multiple communication technologies according to implementations and examples described.

Examples

[0073] Example 1 is a user equipment (UE), including a memory; and a baseband processor configured to, when executing instructions stored in the memory, cause the UE to transmit to a receiving UE, one or more standalone sidelink channel state information reference signals (SL- CSI-RS) in a slot that does not carry SL data

[0074] Example 2 includes the subject matter of example 1, including or omitting optional elements, wherein the slot is a dedicated slot that is pre-configured or configured in a resource pool or in an SL bandwidth part (BWP).

[0075] Example 3 includes the subject matter of any of examples 1-2, including or omitting optional elements, wherein a sub-channel size of frequency resources used to transmit the one or more standalone SL-CSLRS is pre-configured or configured in the resource pool or the SL BWP.

[0076] Example 4 includes the subject matter of any of examples 1-3, including or omitting optional elements, wherein a set of frequency resources of the slot are divided into sub-channels, with each sub-channel associated with a different transmitting UE. [0077] Example 5 includes the subject matter of any of examples 1-4, including or omitting optional elements, wherein the slot does not include resources for physical sidelink feedback channel (PSFCH) transmissions.

[0078] Example 6 includes the subject matter of any of examples 1-5, including or omitting optional elements, wherein the baseband processor is configured to cause the UE to transmit one or more standalone SL-CSI-RS sessions in the slot, wherein all symbols in a standalone SL-CSI- RS session are transmitted using a same TX beam.

[0079] Example 7 includes the subject matter of example 6, including or omitting optional elements, wherein the baseband processor is configured to transmit multiple standalone SL-CSI- RS sessions in the slot using different TX beams.

[0080] Example 8 includes the subject matter of example 6, including or omitting optional elements, wherein the baseband processor is configured to multiple standalone SL-CSI-RS sessions in the slot using a same TX beam.

[0081] Example 9 includes the subject matter of example 6, including or omitting optional elements, wherein each standalone SL-CSI-RS session includes one or more PSCCH symbols corresponding to sidelink control information (SCI) indicating, for the standalone SL-CSLRS session, one or more of a source UE (ID), a destination ID, a periodicity of standalone SL-CSI- RS, time and frequency resources of the standalone SL-CSI-RS, a priority of standalone SL-CSI- RS, or an indication of a TX beam used to transmit standalone SL-CSI-RS; and one or more standalone SL-CSI-RS symbols after the one or more PSCCH symbols.

[0082] Example 10 includes the subject matter of example 9, including or omitting optional elements, wherein each standalone SL-CSI-RS session includes one or more gap symbols between the one or more PSCCH symbols and the one or more standalone SL-CSI-RS symbols.

[0083] Example 11 includes the subject matter of example 6, including or omitting optional elements, wherein the slot includes two or more standalone SL-CSI-RS sessions and wherein each standalone SL-CSI-RS session includes an automatic gain control (AGC) symbol at a beginning of the standalone SL-CSI-RS session or a gap symbol at an end of the standalone SL- CSI-RS session. [0084] Example 12 includes the subject matter of any of examples 1-11, including or omitting optional elements, wherein the baseband processor generates a standalone SL-CSI-RS sequence based on a non- standalone SL-CSI-RS sequence in which an initialization value is based on ten least significant bits (LSBs) of a cyclic redundancy code (CRC) of SCI for the one or more standalone SL-CSI-RS, ten LSBs of a source ID of the one or more standalone SL-CSI- RS, 10 LSBs of a destination ID for the one or more standalone SL-CSI-RS, or a combination of bits of the source ID and the destination ID.

[0085] Example 13 includes the subject matter of any of examples 1-12, including or omitting optional elements, wherein the baseband processor is configured to select resources of the one or more standalone SL-CSI-RS based on a maximum reference signal received power (RSRP) measurement among physical sidclink control channel (PSCCH) demodulation reference signals (DMRS) transmitted by the UE.

[0086] Example 14 includes the subject matter of example 13, including or omitting optional elements, wherein a sensing window for resource selection is pre-configured, configured, or at least as long as a largest resource reservation interval of standalone SL-CSI-RS.

[0087] Example 15 includes the subject matter of example 13, including or omitting optional elements, wherein an RSRP threshold used for resource selection is based on an initial RSRP threshold list, wherein the initial RSRP threshold list is the same as an initial RSRP threshold list that is pre-configured or configured for sidelink data transmission or is different from the initial RSRP threshold list that is pre-configured or configured for sideline data transmission.

[0088] Example 16 includes the subject matter of example 15, including or omitting optional elements, wherein the RSRP threshold is based on an RSRP threshold increment step, wherein the RSRP threshold increment step is set at 3 dB, pre-configured, or configured.

[0089] Example 17 includes the subject matter of example 13, including or omitting optional elements, wherein a ratio of candidate resources for the one or more standalone SL-CSLRS is pre-configured or configured as a same ratio as for sidelink data transmissions or is preconfigured or configured separately from a ratio for sidelink data transmissions.

[0090] Example 18 includes the subject matter of example 13, including or omitting optional elements, wherein the baseband processor is configured to re-evaluate time and frequency resources used for the one or more standalone SL-CSI-RS or, prior to selecting the time and frequency resources, check the time and frequency resources for standalone SL-CSI-RS for preemption by other signals.

[0091] Example 19 includes the subject matter of any of examples 1-18, including or omitting optional elements, wherein the baseband processor is configured to transmit the one or more standalone SL-CSI-RS using a same power as used for PSCCH transmission.

[0092] Example 20 includes the subject matter of any of examples 1-19, including or omitting optional elements, wherein the baseband processor is configured to cause the UE to transmit the one or more standalone SL-CSI-RS in response to determining to initiate a unicast link.

[0093] Example 22 includes the subject matter of any of examples 1-20, including or omitting optional elements, wherein the baseband processor is configured to cause the UE to receive, from a second UE, a beam identification message indicating a TX beam used to transmit at least one of the one or more standalone SL-CSI-RS; and transmit a unicast establishment message to the second UE using the indicated TX beam.

[0094] Example 22 is a user equipment (UE), including a memory and a baseband processor configured to, when executing instructions stored in the memory, cause the UE to receive, from a transmit (TX) UE, one or more standalone sidelink channel state information reference signals (SL-CSI-RS) in a slot that does not carry SL data, wherein the one or more standalone SL-CSI- RS are associated with one or more transmit (TX) beams; measure at least one of the one or more standalone SL-CSI-RS; and based on the measurement, transmit a beam identification message to the TX UE indicating one of the TX beams.

[0095] Example 23 includes the subject matter of example 22, including or omitting optional elements, wherein the baseband processor is configured to measure a received standalone SL- CSLRS in response to determining that a destination ID indicated by the one or more standalone SL-CSI-RS identifies the UE and a source ID indicated by the one or more standalone SL-CSI- RS is a member of a list of UEs with which the UE is configured to communicate. [0096] Example 24 includes the subject matter of example 23, including or omitting optional elements, wherein the baseband processor is configured to determine the source ID and the destination ID based on PSCCH associated with the standalone SL-CSI-RS .

[0097] Example 25 includes the subject matter of any of examples 22-24, including or omitting optional elements, wherein the slot is a dedicated slot that is pre-configured or configured in a resource pool or in an SL bandwidth pail (BWP).

[0098] Example 26 includes the subject matter of any of examples 22-25, including or omitting optional elements, wherein the slot does not include resources for physical sidelink feedback channel (PSFCH) transmissions.

[0099] Example 27 includes the subject matter of any of examples 22-26, including or omitting optional elements, wherein the baseband processor is configured to cause the UE to receive one or more standalone SL-CSI-RS sessions in the slot.

[00100] Example 28 includes the subject matter of example 27, including or omitting optional elements, wherein each standalone SL-CSI-RS session includes one or more PSCCH symbols corresponding to sidelink control information (SCI) indicating, for the standalone SL-CSI-RS session, one or more of a source identifier (ID), a destination UE ID, a periodicity of standalone SL-CSI-RS, time and frequency resources of the standalone SL-CSI-RS, a priority of standalone SL-CSI-RS, or an indication of a TX beam used to transmit standalone SL-CSI-RS; and one or more standalone SL-CSI-RS symbols after the one or more PSCCH symbols.

[00101 ] Example 29 includes the subject matter of example 28, including or omitting optional elements, wherein each standalone SL-CSI-RS session includes one or more gap symbols between the one or more PSCCH symbols and the one or more standalone SL-CSI-RS symbols.

[00102] Example 30 includes the subject matter of example 27, including or omitting optional elements, wherein the slot includes two or more standalone SL-CSI-RS sessions and wherein each standalone SL-CSI-RS session includes an automatic gain control (AGC) symbol at a beginning of the standalone SL-CSI-RS session or a gap symbol at an end of the standalone SL- CSI-RS session. [00103] Example 33 includes the subject matter of example 32, including or omitting optional elements, wherein the baseband processor generates a standalone SL-CSI-RS sequence based on a non- standalone SL-CSI-RS sequence in which an initialization value is based on ten least significant bits (LSBs) of a cyclic redundancy code (CRC) of SCI for the one or more standalone SL-CSI-RS, ten LSBs of a source ID of the standalone SL-CSI-RS, 10 LSBs of a destination ID for the standalone SL-CSI-RS, or a combination of bits of the source ID and the destination ID.

[00104] Example 32 is a baseband processor of any of examples 1-31.

[00105] Example 33 is a method, including actions performed by the baseband processor of any of examples 1-31.

[00106] Example 34 is an apparatus for a UE, including the memory and baseband processor of any of examples 1-31.

[00107] Example 35 is a computer-readable medium having computer-executable instructions stored thereon that, when executed by a baseband processor, cause the baseband processor to perform actions performed by the baseband processor of any of examples 1-31.

[00108] Example 36 is a UE configured to perform any action or combination of actions as substantially described herein in the Detailed Description as being performed by a UE.

[00109] Example 37 is a method that includes any action or combination of actions as substantially described herein in the Detailed Description.

[00110] Example 38 is a method as substantially described herein with reference to each or any combination of the Figures included herein or with reference to each or any combination of paragraphs in the Detailed Description.

[00111] The above description of illustrated examples, implementations, aspects, etc., of the subject disclosure, including what is described in the Abstract, is not intended to be exhaustive or to limit the disclosed aspects to the precise forms disclosed. While specific examples, implementations, aspects, etc., arc described herein for illustrative purposes, various modifications are possible that are considered within the scope of such examples, implementations, aspects, etc., as those skilled in the relevant art can recognize. [00112] While the methods are illustrated and described above as a series of acts or events, it will be appreciated that the illustrated ordering of such acts or events are not to be interpreted in a limiting sense. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein. In addition, not all illustrated acts may be required to implement one or more aspects or embodiments of the disclosure herein. Also, one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases. In some embodiments, the methods illustrated above may be implemented in a computer readable medium using instructions stored in a memory. Many other embodiments and variations are possible within the scope of the claimed disclosure.

[00113] The term “couple” is used throughout the specification. The term may cover connections, communications, or signal paths that enable a functional relationship consistent with the description of the present disclosure. For example, if device A generates a signal to control device B to perform an action, in a first example device A is coupled to device B, or in a second example device A is coupled to device B through intervening component C if intervening component C does not substantially alter the functional relationship between device A and device B such that device B is controlled by device A via the control signal generated by device A.

[00114] It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users.

Claims

CLAIMS What is claimed is:

1. A user equipment (UE), comprising: a memory; and a baseband processor configured to, when executing instructions stored in the memory, cause the UE to transmit to a receiving UE, one or more standalone sidelink channel state information reference signals (SL-CSI-RS) in a slot that does not carry SL data.

2. The UE of claim 1, wherein the slot is a dedicated slot that is pre-configured or configured in a resource pool or in an SL bandwidth part (BWP).

3. The UE of claim 2, wherein a sub-channel size of frequency resources used to transmit the one or more standalone SL-CSI-RS is pre-configured or configured in the resource pool or the SL BWP.

4. The UE of claim 1, wherein a set of frequency resources of the slot are divided into subchannels, with each sub-channel associated with a different transmitting UE.

5. The UE of claim 1, wherein the slot does not include resources for physical sidelink feedback channel (PSFCH) transmissions.

6. The UE of claim 1, wherein the baseband processor generates a standalone SL-CSLRS sequence based on a non- standalone SL-CSI-RS sequence in which an initialization value is based on ten least significant bits (LSBs) of a cyclic redundancy code (CRC) of SCI for the one or more standalone SL-CSI-RS, ten LSBs of a source ID of the one or more standalone SL-CSI- RS, 10 LSBs of a destination ID for the one or more standalone SL-CSI-RS, or a combination of bits of the source ID and the destination ID.

7. The UE of claim 1, wherein the baseband processor is configured to select resources of the one or more standalone SL-CSI-RS based on a maximum reference signal received power (RSRP) measurement among physical sidelink control channel (PSCCH) demodulation reference signals (DMRS) transmitted by the UE.

8. The UE of claim 7, wherein a sensing window for resource selection is pre-configured, configured, or at least as long as a largest resource reservation interval of standalone SL-CSI-RS .

9. The UE of claim 7, wherein an RSRP threshold used for resource selection is based on an initial RSRP threshold list, the initial RSRP threshold list is the same as an initial RSRP threshold list that is preconfigured or configured for sidelink data transmission or is different from the initial RSRP threshold list that is pre-configured or configured for sideline data transmission, and the RSRP threshold is based on an RSRP threshold increment step, wherein the RSRP threshold increment step is set at 3 dB, pre-configured, or configured.

10. The UE of claim 7, wherein a ratio of candidate resources for the one or more standalone SL-CSI-RS is pre-configured or configured as a same ratio as for sidelink data transmissions or is pre-configured or configured separately from a ratio for sidelink data transmissions.

11. The UE of claim 7, wherein the baseband processor is configured to re-evaluate time and frequency resources used for the one or more standalone SL-CSI-RS or, prior to selecting the time and frequency resources, check the time and frequency resources for standalone SL-CSI-RS for pre-emption by other signals.

12. The UE of claim 1, wherein the baseband processor is configured to transmit the one or more standalone SL-CSI-RS using a same power as used for PSCCH transmission.

13. A baseband processor configured to perform operations comprising transmitting, to a receiving UE, one or more standalone sidelink channel state information reference signals (SL-CSI-RS) sessions in a slot that does not carry SL data, wherein all symbols in a standalone SL-CSI-RS session are transmitted using a same TX beam.

14. The baseband processor of claim 13, wherein the operations comprise transmitting multiple standalone SL-CSI-RS sessions in the slot using different TX beams.

15. The baseband processor of claim 13, wherein the operations comprise transmitting multiple standalone SL-CSI-RS sessions in the slot using a same TX beam.

16. The baseband processor of claim 13, wherein each standalone SL-CSI-RS session includes one or more PSCCH symbols corresponding to sidelink control information (SCI) indicating, for the standalone SL-CSI-RS session, one or more of a source UE (ID), a destination ID, a periodicity of standalone SL-CSI-RS, time and frequency resources of the standalone SL- CSI-RS, a priority of standalone SL-CSLRS, or an indication of a TX beam used to transmit standalone SL-CSI-RS; and one or more standalone SL-CSI-RS symbols after the one or more PSCCH symbols.

17. The baseband processor of claim 16, wherein each standalone SL-CSI-RS session includes one or more gap symbols between the one or more PSCCH symbols and the one or more standalone SL-CSI-RS symbols.

18. The baseband processor of claim 13, wherein the slot includes two or more standalone SL-CSLRS sessions and wherein each standalone SL-CSLRS session includes an automatic gain control (AGC) symbol at a beginning of the standalone SL-CSI-RS session or a gap symbol at an end of the standalone SL-CSI-RS session.

19. A user equipment (UE), comprising: a memory; and a baseband processor configured to, when executing instructions stored in the memory, cause the UE to receive, from a transmit (TX) UE, one or more standalone sidelink channel state information reference signals (SL-CSI-RS) in a slot that does not carry SL data, wherein the one or more standalone SL-CSI-RS are associated with one or more transmit (TX) beams; measure at least one of the one or more standalone SL-CSI-RS; and based on the measurement, transmit a beam identification message to the TX UE indicating one of the TX beams.

20. The UE of claim 19, wherein the baseband processor is configured to measure a received standalone SL-CSI-RS in response to determining that a destination ID indicated by the one or more standalone SL-CSI-RS identifies the UE and a source ID indicated by the one or more standalone SL-CSI-RS is a member of a list of UEs with which the UE is configured to communicate.

21. The UE of claim 20, wherein the baseband processor is configured to determine the source ID and the destination ID based on PSCCH associated with the standalone SL-CSI-RS .