Patent Description:
In some examples, a wireless multiple-access communication system may include a number of base stations (BSs), which are each capable of simultaneously supporting communication for multiple communication devices, otherwise known as user equipment (UEs). In other examples (e.g., in a next generation, a new radio (NR), or <NUM> network), a wireless multiple access communication system may include a number of distributed units (DUs) (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmission reception points (TRPs), etc.) in communication with a number of central units (CUs) (e.g., central nodes (CNs), access node controllers (ANCs), etc.), where a set of one or more DUs, in communication with a CU, may define an access node (e.g., which may be referred to as a BS, next generation NodeB (gNB or gNodeB), TRP, etc.). A BS or DU may communicate with a set of UEs on downlink channels (e.g., for transmissions from a BS or DU to a UE) and uplink channels (e.g., for transmissions from a UE to a BS or DU).

The document <CIT>discloses a method that includes determining configuration information of one or more numerologies for sidelink communication; and controlling a base station to transmit the configuration information to user equipment for the user equipment to perform the sidelink communication based on the one or more numerologies.

The document "<NPL>" discusses Sidelink synchronization mechanism.

The document "3GPP - Technical specification group Radio Access Network, NR, Study on NR vehicle-to-everything (V2X), Release <NUM>" discusses vehicle-to-everything (V2X).

The document "3GPP - Technical specification group Radio Access Network, NR, Radio Resource Control (RRC) protocol specification Release <NUM>", discusses UE states and stste tranitions including inter RAT.

A method, an apparatus and a computer program for wireless communication are disclosed by the present disclosure as claimed in the appended claims. Preferred embodiments are subject of the dependent claims. In particular, the present invention is based on the embodiment disclosed below with reference to <FIG>. The remaining embodiments / examples disclosed below are intended for illustrative purposes.

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for determining sidelink synchronization signal numerology by a user equipment (UE).

<NUM> new radio (NR) supports a wide range of communication scenarios over multiple frequency ranges. For example, frequency range <NUM> (FR1) includes <NUM>-<NUM> frequency bands, and FR2 includes <NUM>-<NUM>. Bands in FR2 include millimeter wave (mmW) frequencies and have shorter range but higher available bandwidth than bands in the FR1. To support these communication scenarios, the fixed numerology of LTE has been replaced with a scalable numerology with a range of subcarrier spacing. However, this can create problems for a first UE trying to initiate a sidelink communication with another UE. For example, the first UE may not be aware of the numerology for sidelink synchronization signals in the other UE, preventing the first UE from initiating the sidelink.

The following description provides embodiments and examples.

The techniques described herein may be used for various wireless communication technologies, such as 3GPP Long Term Evolution (LTE), LTE-Advanced (LTE-A), code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), single-carrier frequency division multiple access (SC-FDMA), time division synchronous code division multiple access (TD-SCDMA), and other networks.

CDMA2000 covers IS-<NUM>, IS-<NUM> and IS-<NUM> standards.

NR access (e.g., <NUM> NR) may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., <NUM> or beyond), millimeter wave (mmW) targeting high carrier frequency (e.g., <NUM> or beyond), massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications (URLLC).

For example, the wireless communication network <NUM> may be a NR system (e.g., a <NUM> NR network). In the example shown in <FIG>, a first UE 124a and a second UE 124c include a numerology determination module <NUM> that may be configured for determining numerology for sidelink synchronization signals, according to aspects described herein. As shown, the first UE 124a and the second UE 124c may be in various modes of communication with a base station (BS) <NUM> (e.g., network signaling). In this example, the numerology determination module <NUM> may enable the UE 124a to initiate a sidelink communication with one or more of UE 124b, the second UE 124c, or another UE 124d, based on the mode of communication. It should be noted that any of UEs 124a-124d or UE <NUM> may include the numerology determination module <NUM>.

As illustrated in <FIG>, the wireless communication network <NUM> may include a number of base stations (BSs) <NUM> and other network entities. A BS may be a station that communicates with UEs. Each BS <NUM> may provide communication coverage for a particular geographic area. In some examples, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in wireless communication network <NUM> through various types of backhaul interfaces, such as a direct physical connection, a wireless connection, a virtual network, or the like using any suitable transport network.

In some examples, a UE may function as a scheduling entity in a peerto-peer (P2P) network, and/or in a mesh network.

Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, vehicle to everything (V2X) communications, Internet of Everything (IoE) communications, IoT communications, mission-critical mesh, and/or various other suitable applications. Generally, a sidelink signal may refer to a signal communicated from one subordinate entity (e.g., UE1) to another subordinate entity (e.g., UE2) without relaying that communication through the scheduling entity (e.g., UE or base station), even though the scheduling entity may be utilized for scheduling and/or control purposes.

In some examples of the wireless communication network <NUM>, sidelink communication may be established between UEs without necessarily relying on UE ID or control information from a base station. For example, UE 124c may initiate a sidelink communication with UE 124a without relying on a direct connection with a base station (e.g., base station 110a) if the UE 124c is outside of call 102a range. Any of the UEs (124a-124c) may function as a scheduling entity or a primary sidelink device, while the other UE may function as a subordinate entity or a non-primary (e.g., secondary) sidelink device. Further, the UEs (124a-124c) may be configured to perform beam management procedures for a sidelink as described throughout the disclosure. Accordingly, one or more of the UEs may function as a scheduling entity in a device-to-device (D2D), peerto-peer (P2P), or vehicle-to-vehicle (V2V) network, and/or in a mesh network to initiate and/or schedule certain beam management procedures.

A finely dashed line with double arrows indicates potentially interfering transmissions between a UE and a BS.

<FIG> illustrates example components <NUM> of BS <NUM> and UE <NUM> (e.g., in the wireless communication network <NUM> of <FIG>), which may be used to implement aspects of the present disclosure. For example, antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the UE <NUM> and/or antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the BS <NUM> may be used to perform the various techniques and methods described herein. In the example shown in <FIG>, a UE <NUM> includes a numerology determination circuit <NUM> that may be configured for determining numerology for sidelink synchronization signals, according to aspects described herein. The numerology determination circuit <NUM> may enable the UE <NUM> to initiate a sidelink communication with another UE based on the mode of network signaling between the UE <NUM> and the BS <NUM>.

The transmit processor <NUM> may also generate reference symbols, such as for the primary synchronization signal (PSS), secondary synchronization signal (SSS), and cell-specific reference signal (CRS). A transmit (TX) multiple-input multiple-output (MIMO) processor <NUM> may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 232a-232t. Downlink signals from modulators 232a-232t may be transmitted via the antennas 234a-234t, respectively.

At the UE <NUM>, the antennas 252a-252r may receive the downlink signals from the BS <NUM> and may provide received signals to the demodulators (DEMODs) in transceivers 254a-254r, respectively. A MIMO detector <NUM> may obtain received symbols from all the demodulators 254a-254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols.

The symbols from the transmit processor <NUM> may be precoded by a TX MIMO processor <NUM> if applicable, further processed by the demodulators in transceivers 254a-254r (e.g., for SC-FDM, etc.), and transmitted to the base station <NUM>.

The controllers/processors <NUM> and <NUM> may direct the operation at the BS <NUM> and the UE <NUM>, respectively. The controller/processor <NUM> and/or other processors and modules at the BS <NUM> may perform or direct the execution of processes for the techniques described herein.

<FIG> is a diagram conceptually illustrating a sidelink communication between a first UE 302a and one or more second UEs 302b (collectively, "second UE 302b"). In various examples, any one of the first UE 302a and the second UE 302b may correspond to a UE or other suitable node in the wireless communication network <NUM>. For example, any one of the first UE 302a and the second UE 302b may correspond to UE <NUM>, or UE 124a-124d.

In some examples, the first UE 302a and the second UE 302b may utilize sidelink signals for direct D2D communication. The D2D communication may use the downlink/uplink WWAN spectrum. The D2D communication may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH).

Sidelink signals may include sidelink data <NUM> (i.e., sidelink traffic) and sidelink control information <NUM>. Broadly, the first UE 302a and one or more a second UEs 302b may communicate sidelink data <NUM> and sidelink control information <NUM> using one or more data channels and control channels. In some aspects, data channels include a physical sidelink shared channel (PSSCH) and/or sidelink shared channel (SL-SCH). In some aspects, control channels include a physical sidelink control channel (PSCCH) and/or physical sidelink feedback channel (PSFCH).

Sidelink control information <NUM> may include a source transmit signal (STS), a direction selection signal (DSS), and a destination receive signal (DRS). The DSS/STS may provide for a UE <NUM> (e.g., 302a, 302b) to request a duration of time to keep a sidelink channel available for a sidelink signal; and the DRS may provide for the UE <NUM> to indicate the availability of the sidelink channel, e.g., for a requested duration of time. Accordingly, the first UE 302a and the second UE 302b may negotiate the availability and use of sidelink channel resources prior to communication of sidelink data <NUM> information.

In some configurations, any one or more of the first UE 302a or the second UE 302b may be responsible for initiating and/or scheduling traffic in a D2D communication, including the communication of sidelink data <NUM> and sidelink control information <NUM>, and maintenance of the sidelink communication channel(s). For example, the first UE 302a may be responsible for scheduling and/or initiating beam management procedures (e.g., initial beam selection procedures, beam sweeping procedures, beam refinement procedures, etc.) between the first UE 302a and the second UE 302b, as disclosed herein. In this example, the second UE 302b receives scheduling control information, including but not limited to beam management scheduling information, synchronization or timing information, or other control information.

The channels or carriers illustrated in <FIG> are not necessarily all of the channels or carriers that may be utilized between a first UE 302a and a second UE 302b in a sidelink communication, and those of ordinary skill in the art will recognize that other channels or carriers may be utilized in addition to those illustrated, such as other data, control, and feedback channels.

<FIG> is a diagram showing an example of a frame format <NUM>. The transmission timeline for each data transmission and reception may be partitioned into units of radio frames <NUM>. In NR, the basic transmission time interval (TTI) may be referred to as a slot. In NR, a subframe may contain a variable number of slots (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,. , N slots) depending on the subcarrier spacing (SCS). NR may support a base SCS of <NUM> and other SCS may be defined with respect to the base SCS (e.g., <NUM>, <NUM>, <NUM>, <NUM>, etc.). In the example shown in <FIG>, the SCS is <NUM>. As shown in <FIG>, the subframe <NUM> (subframe <NUM>) contains <NUM> slots (slots <NUM>, <NUM>,. , <NUM>) with a <NUM> duration. The symbol and slot lengths scale with the subcarrier spacing. Each slot may include a variable number of symbol (e.g., OFDM symbols) periods (e.g., <NUM> or <NUM> symbols) depending on the SCS. For the <NUM> SCS shown in <FIG>, each of the slot <NUM> (slot <NUM>) and slot <NUM> (slot <NUM>) includes <NUM> symbol periods (slots with indices <NUM>, <NUM>,. , <NUM>) with a <NUM> duration.

In sidelink, a sidelink synchronization signal block (S-SSB), referred to as the SS block or SSB, is transmitted. The SSB may include a primary SS (PSS), a secondary SS (SSS), and/or a two symbol physical sidelink broadcast channel (PSBCH). In some examples, the SSB can be transmitted up to sixty-four times with up to sixty-four different beam directions. The up to sixty-four transmissions of the SSB are referred to as the SS burst set. SSBs in an SS burst set may be transmitted in the same frequency region, while SSBs in different SS bursts sets can be transmitted in different frequency regions.

In the example shown in <FIG>, in the subframe <NUM>, SSB is transmitted in each of the slots (slots <NUM>, <NUM>,. In the example shown in <FIG>, in the slot <NUM> (slot <NUM>), an SSB <NUM> is transmitted in the symbols <NUM>, <NUM>, <NUM>, <NUM> and an SSB <NUM> is transmitted in the symbols <NUM>, <NUM>, <NUM>, <NUM>, and in the slot <NUM> (slot <NUM>), an SSB <NUM> is transmitted in the symbols <NUM>, <NUM>, <NUM>, <NUM> and an SSB <NUM> is transmitted in the symbols <NUM>, <NUM>, <NUM>, <NUM>, and so on. The SSB may include a primary SS (PSS), a secondary (SSS), and a two symbol physical sidelink broadcast channel (PSBCH). The PSS and SSS may be used by UEs to establish sidelink communication (e.g., transmission and/or reception of data and/or control channels). The PSS may provide half-frame timing, the SS may provide cyclic prefix (CP) length and frame timing. The PBSCH carries some basic system information, such as system bandwidth, timing information within radio frame, SS burst set periodicity, system frame number, etc. The SSBs may be organized into SS bursts to support beam sweeping. Further system information such as, remaining minimum system information (RMSI), system information blocks (SIBs), and other system information (OSI) can be transmitted on a physical sidelink shared channel (PSSCH) in certain subframes.

In NR, the basic subcarrier spacing is fixed in frequency range <NUM> (FR1) and FR2. For example, synchronization signal blocks (SSBs) can have subcarrier spacing (SCS) of <NUM> or <NUM> in FR1, and <NUM> or <NUM> in FR2. Thus, in order for a first UE to synchronize with second UE or a BS, that first UE must search one or both SCSs in each frequency range for the synchronization signal of the second UE or the BS. In the case of sidelink, the first UE has the option of requesting the sidelink synchronization signal block (S-SSB) numerology of the second UE from the BS.

However, the first UE generally does not have this option. For example, the first UE and the second UE may have different service cells, different service cell operators (e.g., AT&T, Verizon), and/or the first and second UEs may have varying levels of connection with their respective serving cells, including no connection at all (e.g., out of range). Moreover, <NUM> new radio (NR) supports a wide range of communication scenarios over multiple frequency ranges (e.g., FR1, FR2, and proposed or adopted FR3 and FR4), including millimeter wave (mmW) frequencies. To support these communication scenarios, the fixed numerology of LTE has been replaced with a scalable numerology with a relatively broader range of subcarrier spacing. Accordingly, the first UE may not be aware of the S-SSB numerology of the second UE, preventing the first UE from initiating sidelink communication. The solutions provided herein are directed to synchronization signals (e.g., S-SSB); however, it should be noted that the solutions can be applied to any suitable sidelink signaling between UEs.

A first UE (e.g., UE 124a), having cell coverage by a BS 110a (e.g., gNB 110a), may determine an S-SSB numerology of a second UE (e.g., UE 124b or UE 124c) by one or more of: (i) an indication (explicit or implicit) of the S-SSB numerology provided by the BS 110a, (ii) a BS 110a SSB numerology, or (iii) a raster location of an access link SSB. In some examples, the S-SSB numerology is a function of one or more of explicit BS 110a indications (via SIB, SIB1, RRC, etc., depending on a mode of network signaling that the first UE 124a is in) and implicit indications (e.g., by derivation of a numerology from signaling received from the BS 110a or other UEs (e.g., UE 124b, 124c, or 124d of <FIG>)) of numerologies of signals used on the access link or sidelink.

In some configurations, the first UE 124a may be within cell coverage of the BS <NUM>10a, and operating in one of an idle mode, a connected mode, or a partial in-coverage mode. For example, a UE operating in idle mode may be within range of a BS (i.e., the UE can receive broadcast messages transmitted by the BS) but does not have an established wireless communication link enabling bi-directional communication (e.g., access link) with the BS. In one example, referring to <FIG>, the first UE 124a can receive broadcast messages over, for example, a physical broadcast channel (PBCH) including messages (e.g., master information block (MIB), system information blocks (SIB), paging signals, etc.) that contain reference signals (e.g., demodulation reference signals (DMRS), phase tracking reference signals (PTRS), sounding reference signals (SRS), channel state information reference signals (CSI-RS), etc.), and data (e.g., synchronization signals, SSB time index, etc.) from the BS 110a.

However, if the first UE 124a is in idle mode, the first UE does not have the access link established with the BS 110a. While in idle mode, the first UE 124a may utilize one or more of the reference signals and/or data it receives from the BS 110a broadcast to determine S-SSB numerology. These reference signals and/or data may be indicative of a network numerology for an access link between the UE 124a and the BS 110a (e.g., parameters required to decode SIB type <NUM> (SIB <NUM>) including one or more of an SSB offset, an SSB location, subcarrier spacing, and/or an explicit indicator). In some examples, the broadcast messages may include information and signaling configured to synchronize the first UE 124a with the BS 110a.

In one example, the SSB offset, SSB location, and/or subcarrier spacing for the access link are the same for sidelink. In this example, sidelink operations use the same numerology as the access link. In other examples, the sidelink operations use the same numerology as certain aspects of the access link. For instance, sidelink operations may use the same numerology as the BS 110a initial uplink bandwidth path. In this case, the UE 124a may receive the numerology from a SIB1. The first UE 124a may then determine a numerology provided by the BS 110a broadcast, and attempt to receive an S-SSB from the second UE using the determined numerology.

In another example, the explicit indicator provides an integer or a formula configured to allow the UE 124a to derive the S-SSB numerology as a function of the network numerology for the access link. In one example, the explicit indicator may include an integer that allows the UE 124a to determine S-SSB numerology by multiplying the access link SSB numerology by the integer. In some examples, the integer may vary based on one or more of service cell operators (e.g., AT&T, Verizon) or cell location, or may be a fixed value.

In another example, if the first UE 124a determines that it is in an idle mode of network signaling, the first UE may determine the SSB numerology based on the broadcast signaling (e.g., SIB) received from the BS. In this example, the broadcast signaling may include an explicit indicator of the SSB numerology, or a network numerology that the SSB numerology can be derived from.

In some configurations, the first UE 124a may be within cell coverage of the BS 110a, and operating in connected mode. A UE operating in connected mode is within range of a BS (i.e., the UE can receive broadcast messages (e.g., SIB), dedicated messages (e.g., SIB-<NUM> and radio resource control (RRC)) transmitted by the BS) and has an established wireless, bi-directional communication link (e.g., access link) between the UE and the BS. For example, referring to <FIG>, the first UE 124a is operating in connected mode with BS 110a.

In another example where the first UE 124a is operating in a connected mode, the first UE 124a may receive a dedicated message from the BS 110a containing one or more indications of an S-SSB numerology or a network numerology. The UE 124a may then determine the S-SSB numerology based on the one or more indications of the sidelink signaling numerology or the network numerology. The first UE 124a may determine the network numerology for an access link based on a broadcast message received from the BS 110a, and derive a first S-SSB numerology from the network numerology based on an explicit indicator. However, if the first UE 124a then receives the dedicated signaling containing a second S-SSB numerology, the first UE 124a may determine to use the second S-SSB numerology instead of the first S-SSB numerology.

In some examples, the first UE 124a may request S-SSB numerology of a second UE (e.g., 124b or UE 124c) from the BS 110a. In this example, the BS 110a may respond to the request with a radio resource control (RRC) message that explicitly indicates the S-SSB numerology of the second UE. In some cases, the UE 124a may receive, from the BS 110a, a dedicated message (e.g., an RRC message) that contains multiple indications of S-SSB numerology for the second UE. In this case, the first UE 124a may determine an S-SSB numerology by selecting one or more of the multiple indications of S-SSB numerology, or by simply using the S-SSB numerology provided if only one is provided in the dedicated message.

In some configurations, the first UE 124a may determine the S-SSB numerology based on one or more raster locations for SSBs in the access link between the first UE 124a and BS 110a. In general, a "raster" is a step size applied to the possible location of any signal or channel. For systems such as GSM, UMTS and LTE, a channel raster means a set of locations in the frequency domain, typically equally spaced, where the carrier center frequency can be located. A sidelink search and synchronization procedure thus involves a UE scanning a frequency range to detect carrier frequencies at which synchronization signals are transmitted by another UE. Thus, the distance between two consecutive places in a channel raster can be assumed as a step size when a terminal tries to search for the carrier frequency.

In <NUM>, however, it is not necessarily the case that the synchronization signals are located at the center frequency of the carrier. More generally, the raster location can be defined as a set of places in the frequency domain and within a frequency span at which a carrier can be found by a terminal, but such a place may or may not be the carrier center frequency. In some examples, the raster location indicates a step size from one possible location for an SSB to another possible location for an SSB.

Generally, raster locations are defined for UEs and BSs regardless of whether the UE or BS has an access link communication. In some examples, raster locations for SSBs in the access link may be the same locations for S-SSBs. However, in other examples, the first UE 124a may have to determine a unique S-SSB numerology based on the access link SSB raster locations.

In one example, the UE 124a offsets the access link raster location using one or more of a time domain and/or frequency domain offset. For example, if the access link raster location has <NUM> sub-carrier spacing (SCS), the UE 124a may determine that the S-SSB also has <NUM> SCS with an offset in one or more of a time domain and/or frequency domain relative to the access link timing and frequency respectively. Accordingly, sidelink raster locations may be expressed as a function of access link raster locations, where the function relates to an offset that is informed to the UE 124a by one or more of a pre-configuration of the UE 124a (e.g., by technical specification or standard), or a notification of the offset provided to the UE 124a by the BS 110a (e.g., via an RRC message or SIB <NUM>) or by a core network entity (e.g., via RRC message). Similarly, if sidelink raster locations are expressed as function of access link raster locations (e.g., via the offset in frequency), then S-SSB numerologies may also be expressed as a function of the numerologies used by the access link.

It should be noted that in <NUM>, some frequency ranges (e.g., FR1, FR2, FR3, FR4) may include multiple numerologies. For example, numerologies for access link over FR1 are <NUM> and <NUM>. In another example, numerologies for access link on another frequency range (e.g., FR3/FR4) may include <NUM>, <NUM>, and <NUM>. In some configurations, sidelink communications may use the same numerologies based on access link raster locations. Thus, in some examples, the second UE (e.g., UE 124b or UE 124c) that is transmitting an S-SSB may determine one or more numerologies used by the access link for communicating S-SSB for sidelink. The second UE selects one or more of the numerologies at random, or based on the capabilities of one or more of the second UE or the first UE 124a. For example, one or more of the first UE 124a and the second UE may only support communication over certain numerologies. In such an example, if the second UE only transmits the S-SSB over supported numerologies, the frequency hypothesis the first UE 124a needs to search for the S-SSB may be reduced.

<FIG> is a diagram illustrating an exemplary in-coverage scenario for determining S-SSB numerology. For example, a first UE <NUM> and a second UE may be inside cell coverage <NUM>. The first UE <NUM> may need to communicate with the second UE <NUM> using sidelink. If the first UE <NUM> is in a connected mode with the BS <NUM>, then the BS may provide a signal indicating synchronization <NUM> that explicitly indicates the numerology for sidelink with the second UE <NUM>. The signal indicating synchronization <NUM> may be communicated via an RRC message with one or more S-SSB numerologies that the first UE <NUM> may use for sidelink communication. The first UE <NUM> then determines an S-SSB numerology based on the signal indicating synchronization <NUM>, and listens to the associated frequency. The first UE <NUM> may then receive the S-SSB signal <NUM> from the second UE <NUM> over the frequency associated with the determined S-SSB numerology. It should be noted that complementary techniques are also within the scope of this disclosure. For example, the first UE <NUM> may determine either a transmit S-SSB numerology or a receive S-SSB numerology. That is, the UE <NUM> may also transmit an S-SSB according to the transmit numerology for the second UE <NUM> to listen for.

If in an idle mode, the first UE <NUM> will receive a signal indicating synchronization <NUM> from the BS <NUM> in the form of a broadcast message (e.g., SIB, SIB1, MIB, etc.). The first UE <NUM> will then determine an SSB numerology <NUM> for initiating an access link between the first UE <NUM> and the BS <NUM> based on the signal indicating synchronization <NUM>. In some configurations, the first UE <NUM> may determine the BS's <NUM> uplink bandwidth path numerology based on the signal indicating synchronization <NUM>. The first UE <NUM> can then determine one or more S-SSB numerologies based on the SSB numerology and/or the uplink bandwidth path numerology. For example, the S-SSB numerology may be the same as the SSB numerology or the uplink bandwidth path numerology. In another example, the first UE <NUM> may multiply one or more of the SSB numerology or the uplink bandwidth path numerology by an integer to determine the S-SSB numerology. The first UE <NUM> then selects an S-SSB numerology based on the signal indicating synchronization <NUM>, and listens to the associated frequency. The first UE <NUM> then receives the S-SSB signal <NUM> from the second UE <NUM> over the frequency associated with the selected S-SSB numerology.

A third UE 124c, having no cell coverage (e.g., out of cell coverage of a BS 110a and BS 110b) may determine an S-SSB timing and/or numerology of another UE by one or more of: (i) a SynchRef UE, (ii) a preconfigured timing, and/or (iii) a raster location of a sidelink SSB.

In some configurations, the third UE 124c may be outside of cell coverage and unable to receive any signals indicating synchronization from the BS 110a. However, if the third UE 124c is within range of a SynchRef UE, then the third UE 124c may receive periodic signals indicating synchronization broadcast from the SynchRef UE. In this example, and referring to <FIG>, any of the first UE 124a and a fourth UE 124d may be a SynchRef UE. According to some configurations, sidelink synchronization signals may include primary and secondary synchronization signals. In some examples, the synchronization signals may be based on NarrowBand IoT (NB-IoT) technology, such as may be considered or adopted by 3GPP. In other examples, the synchronization signals may be referred to variously as sidelink narrowband primary synchronization signals (SL-NPSS) or direct narrowband primary synchronization signals (DNPSS), sidelink narrowband secondary synchronization signals (SL-NSSS), direct narrowband secondary synchronization signal (DNSSS), primary/secondary sidelink synchronization signals (P-SLSS/S-SLSS), or in any other suitable manners.

In one example, the first UE 124a derives its sidelink synchronization signal timing from one or more of the BS 110a or another UE (e.g., UE 124b). The third UE 124c may receive sidelink signal broadcasts from the first UE 124a via a physical sidelink broadcast channel (PSBCH). In some cases, the sidelink signal broadcasts from the first UE 124a may indicate to the third UE 124c whether the first UE 124a is in or out of cell coverage. If the first UE 124a indicates that it is in cell coverage, then the third UE 124c will use the sidelink synchronization signal timing of the first UE 124a to search for an S-SSB of the first UE 124a and/or a fourth UE 124d that the third UE 124c desires to establish a sidelink communication with. It should be noted that the term "SyncRef' is relative to a UE. For example, the first UE 124a is a SyncRef UE for the third UE 124c if the third UE 124c derives its sidelink timing based on the first UE 124a. In this example, the UE 124a serves as SyncRef UE for UE 124c.

In another example, the fourth UE 124d is a SynchRef UE for UE 124c, but it is out of cell coverage and cannot derive its synchronization signal timing from a BS. In this example, the third UE 124c may use the synchronization signal timing of the fourth UE 124d to search for an S-SSB of the first UE 124a and/or the fourth UE 124d that the third UE 124c desires to establish a sidelink communication with. It should be noted however, that the synchronization signal of a UE in cell coverage is preferable in some cases.

In another example, the third UE 124c may not detect or may be out of range of a sidelink broadcast message from all UEs. In this example, the third UE 124c may determine its own sidelink synchronization signal timing. In some configurations, the third UE 124c may be pre-configured to utilize one or more particular synchronization signal timings adopted by 3GPP. In some configurations, the third UE 124c may be preconfigured by a service provider to utilize one or more particular synchronization signal timings (e.g., one or more particular synchronization signal timings for sidelink are programmed into a subscriber identification module (SIM) card). In some configurations, the third UE 124c may store one or more of a synchronization signal used by a BS while the third UE 124c was within cell coverage or a sidelink synchronization signal used by another UE when the third UE 124c was able to receive a sidelink broadcast signal. The third UE 124c will use the preconfigured or stored synchronization signal timing to search for an S-SSB of the first UE 124a and/or a fourth UE 124d that the third UE 124c desires to establish a sidelink communication with.

In some examples, the third UE 124c may determine a numerology for S-SSB base on raster locations. As noted previously, raster locations are defined for UEs and BSs regardless of whether the UE or BS has an access link communication. Thus, the third UE 124c includes knowledge of access link raster locations despite being out of cell coverage.

Similar to the example given above, the third UE 124c may offset an access link raster location using one or more of a time domain and/or frequency domain offset. Accordingly, sidelink raster locations may be expressed as a function of access link raster locations, where the function relates to an offset that is informed to the third UE 124c by one or more of a pre-configuration of the third UE 124c (e.g., by technical specification or standard), or a previous notification of the offset provided to the third UE 124c by a BS or by a core network entity.

It should be noted that in some cases, a UE may be partially within cell coverage. For example, the UE may be within range of a BS, but have poor measurement on reference signals from the BS. For example, the first UE 124a may determine that it is in a partially in-coverage mode if it determines that the reference signal received power (RSRP) or the reference signal received quality (RSRQ) from the BS is below a particular threshold. In one example, the third UE 124c may be partially within cell coverage, but may have poor measurement on reference signals from the BS 110a. In this example, the third UE 124c may use the numerology selection techniques described relating to either in-coverage UEs or out-of-coverage UEs.

In some examples, whether the first UE 124a is in an out-of-coverage mode (e.g., disconnected or out of range of a cell signal) or an in-coverage mode (e.g., connected, idle, partially connected) of network signaling, the first UE 124a may select one or more raster locations from a synchronization raster, each of the one or more raster locations comprising one or more indications of frequency locations of SSBs configured to synchronize the first UE to the BS for network communication. The first UE 124a may then determine an S-SSB numerology by offsetting the one or more raster locations by a frequency offset to generate one or more locations of S-SSBs configured to synchronize the first UE 124a to another UE (e.g., the third UE 124c) for sidelink communication. Here, the first UE 124a determines where in frequency the S-SSB should be sent. For example, the first UE 124a derives allowed frequency locations that the S-SSB can be communicated over by applying an offset to the access network SSB frequency locations.

<FIG> is a diagram illustrating an exemplary out-of-coverage scenario for determining S-SSB numerology. In one example, a first UE <NUM> may need to communicate with a second UE <NUM> using sidelink. However, both the first UE <NUM> and the second UE <NUM> are outside of cell coverage <NUM>. In this example, the second UE <NUM> is a SynchRef UE and is transmitting over a sidelink communication <NUM> with a third UE <NUM>. Accordingly, the second UE <NUM> is broadcasting sidelink signals indicating whether the second UE <NUM> is in coverage or out of coverage. It should be noted that communication of sidelink signals may be facilitated using one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). In this example, the second UE <NUM> will indicate that is it outside of cell coverage <NUM>. However, if the first UE <NUM> is unable to find another UE that is within cell coverage <NUM>, the first UE <NUM> will utilize the second UE <NUM> to derive sidelink synchronization timing. In this example, the first UE receives SyncRef signals <NUM> being broadcast from the second UE <NUM> and derives S-SSB timing based on the SynchRef signals <NUM>. In some cases, the SyncRef signals <NUM> may be related to the timing of a BS <NUM> signal indicating synchronization <NUM>.

In another scenario, the second UE <NUM> is within cell coverage, and is a SynchRef UE. In this scenario, the first UE <NUM> receives an indication form the second UE <NUM> that the second UE <NUM> is within cell coverage <NUM>. Thus, the timing of the SynchRef signals <NUM> could be related to the timing of signals indicating synchronization <NUM> of the BS <NUM>. In this scenario, the first UE <NUM> will prefer the timing of the SynchRef signals <NUM> over signals of another UE that is out of cell overage <NUM>.

In another scenario, both the first UE <NUM> and the second UE <NUM> are outside of cell coverage <NUM>, and neither the first UE <NUM> nor the second UE <NUM> have an active sidelink communication. In this scenario, the first UE <NUM> picks its own timing based on a previous sidelink communication or a previous access link communication. In some configurations, the timing may be preconfigured according to a wireless standard such as 3GPP or a wireless service provider, and may be stored in the first UE <NUM>. In this configuration, the first UE <NUM> determines an S-SSB numerology <NUM> based on the previous timing or the preconfigured timing, and proceeds to transmit an S-SSB signal <NUM> according to the timing, or listens for an S-SSB signal <NUM> from the second UE <NUM> according to the timing.

In another scenario, the first UE <NUM> determines S-SSB numerology <NUM> based on one or more known raster locations. An S-SSB numerology may be determined as a function of access link raster locations, where the function relates to an offset that is informed to the first UE <NUM> by one or more of a pre-configuration (e.g., by technical specification, standard, or service provider), or a previous notification of the offset provided by a BS or by a core network entity.

<FIG> is a flow diagram illustrating example operations <NUM> for wireless communication, in accordance with certain aspects of the present disclosure. The operations <NUM> may be performed, for example, using any of the UEs as described in relation to <FIG>, <FIG>, and <FIG>. Operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor <NUM> of <FIG>). Further, the transmission and reception of signals by the UE in operations <NUM> may be enabled, for example, by one or more antennas (e.g., antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., controller/processor <NUM>) obtaining and/or outputting signals.

The operations <NUM> may begin, at block <NUM>, by determining a mode of network signaling between the first UE and a base station (BS). In some examples, the mode of network signaling may include an idle mode, a connected mode, and in-coverage, out-of coverage, or a partially in-coverage mode of the first UE. In the idle mode, the first UE may be limited to receiving broadcast messages from the BS. In the connected mode, the UE may communicate over an access link with the BS. Partially in-coverage mode may correspond to a limited number of visible BS beams and/or a relatively weak reference signal received power (RSRP). For example, determining the mode of network signaling may be based on one or more of the RSRP corresponding to the network signaling between the UE and the B S, or whether a limited number B S beams are visible to the first UE. A UE in such a partially in-coverage mode may follow the rules described herein for either the in-coverage UEs or the out-of-coverage UEs.

In some examples, the determined mode of network signaling is a disconnected mode wherein the BS is out of range (e.g., an out-of-coverage mode). In such an example, selecting the first numerology includes deriving a subcarrier spacing from a broadcast signal received from a second UE over a physical sidelink broadcast channel (PSBCH). However, in some configurations, selecting the first numerology includes retrieving one or more indications of sidelink numerology from a memory device, wherein the one or more indications of sidelink numerology are configured to synchronize the first UE to the second UE for sidelink communication.

At block <NUM>, the operations <NUM> proceed by determining a first numerology based on the mode. For example, if the determined mode is partially connected, then determine the first numerology may be based on one or more of preconfigured synchronization signal timing or a raster location. In another example, if the determined mode is an idle mode, the operation may determine the first numerology from one or more indications of network numerology that are received from a BS in a broadcast message that are configured to synchronize the first UE to the BS. In some examples, the broadcast message may include a system information block (SIB).

In another example, if the determined mode is connected mode, then determining the first numerology may be based on one or more indications of sidelink signaling numerology received from the BS in a dedicated message over an access link. In this example, the indications of sidelink signaling numerology are configured to synchronize the first UE to the second UE. In some examples, the dedicated message includes an RRC message.

In some examples, the first numerology may be determined based on a synchronization raster that includes one or more indications of a network numerology configured to synchronize the first UE to the BS for network communication (e.g., access link). However, in some examples, the synchronization raster may include indications of S-SSBs configured to synchronize the first UE to another UE for sidelink communication.

In some examples, the first numerology may be determined from one or more raster locations from the synchronization raster which includes one or more indications of frequency locations of SSBs configured to synchronize the first UE to the BS for network communication. In this example, the operation <NUM> may offset the one or more raster locations by a frequency offset to generate one or more locations of S-SSBs configured to synchronize the first UE to another UE for sidelink communication. The operation <NUM> may then determine the first numerology based on a numerology associated with the one or more locations of S-SSBs.

At block <NUM>, the operation <NUM> proceeds to receiving, from a second UE, a sidelink signal having a subcarrier spacing corresponding to the first numerology. In some examples, the received sidelink signal includes an S-SSB. In some examples, the sidelink signal includes one or more of a primary sidelink synchronization signal (P-SLSS), a secondary sidelink synchronization signal (S-SLSS), or a physical sidelink broadcast channel (PSBCH) signal, wherein the P-SLSS, the S-SLSS, and the PSBCH signals are configured to synchronize the first UE to the second UE.

In certain aspects, the sidelink signal comprises sidelink synchronization signaling block (S-SSB).

In certain aspects, the sidelink signal includes one or more of a primary sidelink synchronization signal (P-SLSS), a secondary sidelink synchronization signal (S-SLSS), or a physical sidelink broadcast channel (PSBCH) signal, wherein the P-SLSS, the S-SLSS, and the PSBCH signals are configured to synchronize the first UE to the second UE.

In certain aspects, determining the mode of network signaling between the first UE and the BS further comprises determining the first UE is in a partially in-coverage mode of network signaling, wherein the determining the first UE is in the partially in-coverage mode is based on one or more of: (i) a reference signal received power (RSRP) corresponding to the network signaling between the first UE and the BS, or (ii) a limited number BS beams visible to the first UE.

In certain aspects, determining the mode of network signaling between the first UE and the BS further comprises determining the first UE is in an idle mode of network signaling, the method further comprising receiving, from the BS, a broadcast message comprising an explicit indicator of the first numerology.

In certain aspects, wherein the broadcast message is a system information block (SIB).

In certain aspects, determining the mode of network signaling between the first UE and the BS further comprises determining the first UE is in a connected mode of network signaling, the method further comprising: receiving, from the BS, a dedicated message comprising one or more indications of a sidelink signaling numerology or a network numerology; and wherein determining the first numerology comprises selecting the first numerology from the one or more indications of the sidelink signaling numerology or the network numerology.

In certain aspects, the dedicated message comprising the one or more indications of the sidelink signaling numerology is a radio resource control (RRC) message; and the dedicated message comprising the one or more indications of the network numerology is a system information block-<NUM> (SIB-<NUM>).

In certain aspects, the dedicated message consists of the sidelink signaling numerology, the method further comprising: determining the network numerology for an access link based on a broadcast message received from the BS, the network numerology configured to synchronize the first UE to the BS; deriving another sidelink signaling numerology from the network numerology based on an explicit indicator; and wherein determining the first numerology comprises selecting the sidelink signaling numerology instead of the other sidelink signaling numerology.

In certain aspects, the indications of sidelink signaling numerology are configured to synchronize the first UE to the second UE; and the indications of the network numerology are configured to synchronize the first UE to the BS for network communication and synchronize the first UE to the second UE for sidelink communication.

In certain aspects, the operation <NUM> may also include selecting one or more raster locations from a synchronization raster, each of the one or more raster locations comprising one or more indications of frequency locations of synchronization signal blocks (SSBs) configured to synchronize the first UE to the BS for network communication; and offsetting the one or more raster locations by a frequency offset to generate one or more locations of sidelink synchronization signal blocks (S-SSBs) configured to synchronize the first UE to the second UE for sidelink communication.

The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium/memory <NUM> via a bus <NUM>. In certain aspects, the computer-readable medium/memory <NUM> is configured to store instructions (e.g., computer-executable code) that when executed by the processor <NUM>, cause the processor <NUM> to perform the operations illustrated in <FIG>, or other operations for performing the various techniques discussed herein. In certain aspects, computer-readable medium/memory <NUM> stores code for determining a mode of network signaling <NUM>. The computer-readable medium/memory <NUM> may also store code for determining numerology <NUM>. The computer-readable medium/memory <NUM> may also store code for wireless communication <NUM>.

In certain aspects, the processor <NUM> has circuitry configured to implement the code stored in the computer-readable medium/memory <NUM>. The processor <NUM> includes circuitry for determining a mode of network signaling <NUM>. The circuitry for determining a mode of network signaling <NUM> may operate in coordination with the code for determining a mode of network signaling <NUM>. The processor <NUM> includes circuitry for determining numerology <NUM>. The circuitry for determining numerology <NUM> may operate in coordination with the code for determining numerology <NUM>.

The processor includes circuitry for wireless communication <NUM>. The circuitry for wireless communication <NUM> may include one or more hardware components that provide the physical structure that performs various processes related to wireless communication (e.g., signal reception and/or signal transmission) as described herein. The circuitry for wireless communication <NUM> may operate in coordination with the code for wireless communication <NUM>.

The method steps and/or actions may be interchanged with one another. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified.

For example, determining a numerology may include a UE determining a numerology using signaling that the UE can receive based on its mode of network signaling. For example, if the UE is out-of-coverage (e.g., no cell coverage), then one option the UE may have for determining an S-SSB numerology is to listen for a PBSCH from another UE nearby, and determine the S-SSB numerology based on a received PBSCH signal. In other words, the network signaling mode of the UE may dictate the types of signaling that the UE can use to determine S-SSB numerology.

Unless specifically stated otherwise, the term "some" refers to one or more.

Claim 1:
A method (<NUM>) of sidelink communication at a first user equipment, UE, comprising:
determining (<NUM>), the first UE is in a partially in-coverage mode of network signaling between the first UE and a base station, wherein the determining the first UE is in the partially in-coverage mode is based on one or more of: (i) a reference signal received power, RSRP, corresponding to the network signaling between the first UE and the BS, or (ii) a limited number BS beams visible to the first UE;
on determining the first UE is in the partially in-coverage mode of network signaling, determining (<NUM>) a first numerology based on at least one of a preconfigured synchronization signal timing or a raster location; and
receiving (<NUM>) , from a second UE, a sidelink signal having a subcarrier spacing corresponding to the first numerology.