Patent Publication Number: US-2021195487-A1

Title: User equipment (ue) capability and enablement flag for l1/l2 inter-cell mobility

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit to U.S. Provisional Patent Application Ser. No. 62/952,759, entitled “User Equipment (UE) Capability and Enablement Flag for L1/L2 Inter-Cell Mobility,” filed Dec. 23, 2019, and assigned to the assignee hereof, the contents of which are hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for enabling L1/L2 inter-cell mobility. 
     BACKGROUND 
     Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. These wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (for example, bandwidth, transmit power, etc.). Examples of such multiple-access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE Advanced (LTE-A) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems, to name a few. 
     These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. New radio (for example, 5G NR) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL). To these ends, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation. 
     However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in NR and LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies. 
     A control resource set (CORESET) for systems, such as an NR and LTE systems, may comprise one or more control resource (e.g., time and frequency resources) sets, configured for conveying PDCCH, within the system bandwidth. Within each CORESET, one or more search spaces (e.g., common search space (CSS), UE-specific search space (USS), etc.) may be defined for a given UE. 
     SUMMARY 
     The systems, methods, and devices of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes. 
     One innovative aspect of the subject matter described in this disclosure can be implemented in a method for wireless communication by a user equipment (UE). The method generally includes transmitting, to a network entity, a report indicating a capability of the UE to support one or more inter-cell mobility procedures based on at least one of physical (PHY) layer or medium access control (MAC) layer signaling, receiving PHY layer or MAC layer signaling related to an inter-cell mobility procedure, and initiating at least one of the inter-cell mobility procedures based on the received PHY layer or MAC layer signaling. 
     In some aspects, the PHY layer or MAC layer signaling comprises downlink control information (DCI) indicating a cell selection for inter-cell mobility. 
     In some aspects, the PHY layer or MAC layer signaling comprises a MAC control element (CE) indicating a cell selection for inter-cell mobility. 
     In some aspects, the reporting includes a single field to indicate the UE supports multiple operation modes of inter-cell mobility procedures based on at least one of PHY layer or MAC layer signaling. 
     In some aspects, the operation modes include at least two of: a first mode of inter-cell mobility procedures including each serving cell having one physical cell ID (PCI) and one or multiple physical cell sites, each physical cell site transmitting unique cell-defining reference signal (RS), and PHY layer or MAC layer signaling indicating a selection of which physical cell site or cell-defining RS to serve the UE; a second mode of inter-cell mobility procedures including each serving cell being configured with multiple PCIs, each cell site being associated with one of the PCIs, and PHY layer or MAC layer signaling indicating a selection of one or more cell sites, corresponding one or more PCIs, or cell-defining RS to serve the UE; or a third mode of inter-cell mobility procedures including each serving cell having one PCI, and PHY layer or MAC layer signaling indicating a selection of one or more serving cells or corresponding PCIs to serve the UE. 
     In some aspects, the reporting includes an indication of whether or not the UE supports each respective operation mode of a plurality of different operation modes of inter-cell mobility procedures based on at least one of PHY layer or MAC layer signaling. 
     In some aspects, the operation modes include at least two of: a first mode of inter-cell mobility procedures including each serving cell having one physical cell ID (PCI) and one or multiple physical cell sites, each physical cell site transmitting unique cell-defining reference signal (RS), and PHY layer or MAC layer signaling indicating a selection of which physical cell site or cell-defining RS to serve the UE; a second mode of inter-cell mobility procedures including each serving cell being configured with multiple PCIs, each cell site being associated with one of the PCIs, and PHY layer or MAC layer signaling indicating a selection of one or more cell sites, corresponding one or more PCIs, or cell-defining RS to serve the UE; or a third mode of inter-cell mobility procedures including each serving cell having one PCI, and PHY layer or MAC layer signaling indicating a selection of one or more serving cells or corresponding PCIs to serve the UE. 
     In some aspects, the method further comprises receiving, from the network entity, signaling indicating enablement of inter-cell mobility procedures based on at least one of PHY layer or MAC layer signaling. 
     In some aspects, the indication is based on a configuration of a radio resource control (RRC) parameter. 
     In some aspects, the indication is based on at least one of a downlink control information (DCI) or a MAC control element (MAC CE). 
     One innovative aspect of the subject matter described in this disclosure can be implemented in a method for wireless communication by a network entity. The method generally includes receiving reporting, from a user equipment (UE), indicating a capability of the UE to support one or more inter-cell mobility procedures based on at least one of physical (PHY) layer or medium access control (MAC) layer signaling, and transmitting, to the UE, PHY layer or MAC layer signaling related to an inter-cell mobility procedure. 
     In some aspects, the PHY layer or MAC layer signaling comprises downlink control information (DCI) indicating a cell selection for inter-cell mobility. 
     In some aspects, the PHY layer or MAC layer signaling comprises a MAC control element (MAC CE) indicating a cell selection for inter-cell mobility. 
     In some aspects, the reporting includes a single field to indicate the UE supports multiple operation modes of inter-cell mobility procedures based on at least one of PHY layer or MAC layer signaling. 
     In some aspects, the operation modes include at least two of: a first mode of inter-cell mobility procedures including each serving cell having one physical cell ID (PCI) and one or multiple physical cell sites, each physical cell site transmitting unique cell-defining reference signal (RS), and PHY layer or MAC layer signaling indicating a selection of which physical cell site or cell-defining RS to serve the UE; a second mode of inter-cell mobility procedures including each serving cell being configured with multiple PCIs, each cell site being associated with one of the PCIs, and PHY layer or MAC layer signaling indicating a selection of one or more cell sites, corresponding one or more PCIs, or cell-defining RS to serve the UE; or a third mode of inter-cell mobility procedures including each serving cell having one PCI, and PHY layer or MAC layer signaling indicating a selection of one or more serving cells or corresponding PCIs to serve the UE. 
     In some aspects, the reporting includes an indication of whether or not the UE supports each respective operation mode of a plurality of different operation modes of inter-cell mobility procedures based on at least one of PHY layer or MAC layer signaling. 
     In some aspects, the operation modes include at least two of: a first mode of inter-cell mobility procedures including each serving cell having one physical cell ID (PCI) and one or multiple physical cell sites, each physical cell site transmitting unique cell-defining reference signal (RS), and PHY layer or MAC layer signaling indicating a selection of which physical cell site or cell-defining RS to serve the UE; a second mode of inter-cell mobility procedures including each serving cell being configured with multiple PCIs, each cell site being associated with one of the PCIs, and PHY layer or MAC layer signaling indicating a selection of one or more cell sites, corresponding one or more PCIs, or cell-defining RS to serve the UE; or a third mode of inter-cell mobility procedures including each serving cell having one PCI, and PHY layer or MAC layer signaling indicating a selection of one or more serving cells or corresponding PCIs to serve the UE. 
     In some aspects, the method further comprises sending, to the UE, signaling indicating enablement of inter-cell mobility procedures based on at least one of PHY layer or MAC layer signaling. 
     In some aspects, the indication is based on a configuration of a radio resource control (RRC) parameter. 
     In some aspects, the indication is based on at least one of a downlink control information (DCI) or a MAC control element (MAC CE). 
     Aspects of the present disclosure provide means for, apparatuses, processors, and computer-readable mediums for performing the methods described herein. 
     To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the appended drawings set forth in detail some illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Details of one or more implementations of the subject matter described in this disclosure are set forth in the accompanying drawings and the description below. However, the accompanying drawings illustrate only some typical aspects of this disclosure and are therefore not to be considered limiting of its scope. Other features, aspects, and advantages will become apparent from the description, the drawings and the claims. 
         FIG. 1  shows an example wireless communication network in which some aspects of the present disclosure may be performed. 
         FIG. 2  shows a block diagram illustrating an example base station (BS) and an example user equipment (UE) in accordance with some aspects of the present disclosure. 
         FIG. 3  illustrates an example of a frame format for a telecommunication system, in accordance with certain aspects of the present disclosure. 
         FIG. 4  illustrates example operations for wireless communication by a user equipment (UE), in accordance with some aspects of the present disclosure. 
         FIG. 5  illustrates an example operation for wireless communication by a network entity, in accordance with some aspects of the present disclosure. 
         FIG. 6  is a call flow diagram illustrating messages exchanged between a user equipment (UE) and network entities for enabling L1/L2 inter-cell mobility, in accordance with some aspects of the present disclosure. 
         FIG. 7  illustrates a communications device that may include various components configured to perform operations for the techniques disclosed herein in accordance with aspects of the present disclosure. 
         FIG. 8  illustrates a communications device that may include various components configured to perform operations for the techniques disclosed herein in accordance with aspects of the present disclosure. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation. 
     DETAILED DESCRIPTION 
     Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for enabling physical layer (L1) and/or medium access control layer (L2) inter-cell mobility. 
     The following description provides examples of enabling L1/L2 inter-cell mobility, and is not limiting of the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to, or other than, the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim. 
     In various aspects, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular radio access technology (RAT) and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a subcarrier, a frequency channel, a tone, a subband, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, a 5G NR RAT network may be deployed. 
       FIG. 1  illustrates an example wireless communication network  100  in which aspects of the present disclosure may be performed. For example, as shown in  FIG. 1 , UE  120   a  may include an L1/L2 mobility enablement module  122  that may be configured to perform (or cause UE  120   a  to perform) operations  400  of  FIG. 4 . Similarly, base station  110   a  may include an L1/L2 mobility enablement module  112  that may be configured to perform (or cause BS  110   a  to perform) operations  500  of  FIG. 5 . 
     NR access (for example, 5G NR) may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (for example, 80 MHz or beyond), millimeter wave (mmWave) targeting high carrier frequency (for example, 25 GHz or beyond), massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, or mission critical services targeting ultra-reliable low-latency communications (URLLC). These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTI) to meet respective quality of service (QoS) requirements. In addition, these services may co-exist in the same time-domain resource (for example, a slot or subframe) or frequency-domain resource (for example, component carrier). 
     As illustrated in  FIG. 1 , the wireless communication network  100  may include a number of base stations (BSs)  110   a - z  (each also individually referred to herein as BS  110  or collectively as BSs  110 ) and other network entities. A BS  110  may provide communication coverage for a particular geographic area, sometimes referred to as a “cell”, which may be stationary or may move according to the location of a mobile BS  110 . In some examples, the BSs  110  may be interconnected to one another or to one or more other BSs or network nodes (not shown) in wireless communication network  100  through various types of backhaul interfaces (for example, a direct physical connection, a wireless connection, a virtual network, or the like) using any suitable transport network. In the example shown in  FIG. 1 , the BSs  110   a ,  110   b  and  110   c  may be macro BSs for the macro cells  102   a ,  102   b  and  102   c , respectively. The BS  110   x  may be a pico BS for a pico cell  102   x . The BSs  110   y  and  110   z  may be femto BSs for the femto cells  102   y  and  102   z , respectively. A BS may support one or multiple cells. The BSs  110  communicate with user equipment (UEs)  120   a - y  (each also individually referred to herein as UE  120  or collectively as UEs  120 ) in the wireless communication network  100 . The UEs  120  (for example,  120   x ,  120   y , etc.) may be dispersed throughout the wireless communication network  100 , and each UE  120  may be stationary or mobile. 
     Wireless communication network  100  may also include relay stations (for example, relay station  110   r ), also referred to as relays or the like, that receive a transmission of data or other information from an upstream station (for example, a BS  110   a  or a UE  120   r ) and sends a transmission of the data or other information to a downstream station (for example, a UE  120  or a BS  110 ), or that relays transmissions between UEs  120 , to facilitate communication between devices. 
     A network controller  130  may couple to a set of BSs  110  and provide coordination and control for these BSs  110 . The network controller  130  may communicate with the BSs  110  via a backhaul. The BSs  110  may also communicate with one another (for example, directly or indirectly) via wireless or wireline backhaul. 
       FIG. 2  shows a block diagram illustrating an example base station (BS) and an example user equipment (UE) in accordance with some aspects of the present disclosure. 
     At the BS  110 , a transmit processor  220  may receive data from a data source  212  and control information from a controller/processor  240 . The control information may be for the physical broadcast channel (PBCH), physical control format indicator channel (PCFICH), physical hybrid ARQ indicator channel (PHICH), physical downlink control channel (PDCCH), group common PDCCH (GC PDCCH), etc. The data may be for the physical downlink shared channel (PDSCH), etc. The processor  220  may process (for example, encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmit processor  220  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  230  may perform spatial processing (for example, precoding) on the data symbols, the control symbols, or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs)  232   a - 232   t . Each modulator  232  may process a respective output symbol stream (for example, for OFDM, etc.) to obtain an output sample stream. Each modulator may further process (for example, convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators  232   a - 232   t  may be transmitted via the antennas  234   a - 234   t , respectively. 
     At the UE  120 , the antennas  252   a - 252   r  may receive the downlink signals from the BS  110  and may provide received signals to the demodulators (DEMODs) in transceivers  254   a - 254   r , respectively. Each demodulator  254  may condition (for example, filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator may further process the input samples (for example, for OFDM, etc.) to obtain received symbols. A MIMO detector  256  may obtain received symbols from all the demodulators  254   a - 254   r , perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor  258  may process (for example, demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE  120  to a data sink  260 , and provide decoded control information to a controller/processor  280 . 
     On the uplink, at UE  120 , a transmit processor  264  may receive and process data (for example, for the physical uplink shared channel (PUSCH)) from a data source  262  and control information (for example, for the physical uplink control channel (PUCCH) from the controller/processor  280 . The transmit processor  264  may also generate reference symbols for a reference signal (for example, for the sounding reference signal (SRS)). The symbols from the transmit processor  264  may be precoded by a TX MIMO processor  266  if applicable, further processed by the demodulators in transceivers  254   a - 254   r  (for example, for SC-FDM, etc.), and transmitted to the BS  110 . At the BS  110 , the uplink signals from the UE  120  may be received by the antennas  234 , processed by the modulators  232 , detected by a MIMO detector  236  if applicable, and further processed by a receive processor  238  to obtain decoded data and control information sent by the UE  120 . The receive processor  238  may provide the decoded data to a data sink  239  and the decoded control information to the controller/processor  240 . 
     The memories  242  and  282  may store data and program codes for BS  110  and UE  120 , respectively. A scheduler  244  may schedule UEs for data transmission on the downlink or uplink. 
     The controller/processor  280  or other processors and modules at the UE  120  may perform or direct the execution of processes for the techniques described herein. As shown in  FIG. 2 , the controller/processor  280  of the UE  120  has an L1/L2 mobility module that may be configured to perform operations  400  of  FIG. 4 , while the controller/processor  240  of the BS  110  has an L1/L2 mobility module that may be configured to perform operations  500  of  FIG. 5 , as discussed in further detail below. Although shown at the Controller/Processor, other components of the UE or BS may be used to perform the operations described herein. 
       FIG. 3  is a diagram showing an example of a frame format  300  for NR. The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 ms) and may be partitioned into 10 subframes, each of 1 ms, with indices of 0 through 9. Each subframe may include a variable number of slots depending on the subcarrier spacing. Each slot may include a variable number of symbol periods (e.g., 7 or 14 symbols) depending on the subcarrier spacing. The symbol periods in each slot may be assigned indices. A mini-slot, which may be referred to as a sub-slot structure, refers to a transmit time interval having a duration less than a slot (e.g., 2, 3, or 4 symbols). 
     Each symbol in a slot may indicate a link direction (e.g., DL, UL, or flexible) for data transmission and the link direction for each subframe may be dynamically switched. The link directions may be based on the slot format. Each slot may include DL/UL data as well as DL/UL control information. 
     In NR, a synchronization signal (SS) block is transmitted. The SS block includes a PSS, a SSS, and a two symbol PBCH. The SS block can be transmitted in a fixed slot location, such as the symbols 0-3 as shown in  FIG. 3 . The PSS and SSS may be used by UEs for cell search and acquisition. The PSS may provide half-frame timing, the SS may provide the CP length and frame timing. The PSS and SSS may provide the cell identity. The PBCH carries some basic system information, such as downlink system bandwidth, timing information within radio frame, SS burst set periodicity, system frame number, etc. The SS blocks may be organized into SS bursts to support beam sweeping. Further system information such as, remaining minimum system information (RMSI), system information blocks (SIBs), other system information (OSI) can be transmitted on a physical downlink shared channel (PDSCH) in certain subframes. The SS block can be transmitted up to sixty-four times, for example, with up to sixty-four different beam directions for mmW. The up to sixty-four transmissions of the SS block are referred to as the SS burst set. SS blocks in an SS burst set are transmitted in the same frequency region, while SS blocks in different SS bursts sets can be transmitted at different frequency locations. 
     A control resource set (CORESET) for systems, such as an NR and LTE systems, may comprise one or more control resource (e.g., time and frequency resources) sets, configured for conveying PDCCH, within the system bandwidth. Within each CORESET, one or more search spaces (e.g., common search space (CSS), UE-specific search space (USS), etc.) may be defined for a given UE. According to aspects of the present disclosure, a CORESET is a set of time and frequency domain resources, defined in units of resource element groups (REGs). Each REG may comprise a fixed number (e.g., twelve) tones in one symbol period (e.g., a symbol period of a slot), where one tone in one symbol period is referred to as a resource element (RE). A fixed number of REGs may be included in a control channel element (CCE). Sets of CCEs may be used to transmit new radio PDCCHs (NR-PDCCHs), with different numbers of CCEs in the sets used to transmit NR-PDCCHs using differing aggregation levels. Multiple sets of CCEs may be defined as search spaces for UEs, and thus a NodeB or other base station may transmit an NR-PDCCH to a UE by transmitting the NR-PDCCH in a set of CCEs that is defined as a decoding candidate within a search space for the UE, and the UE may receive the NR-PDCCH by searching in search spaces for the UE and decoding the NR-PDCCH transmitted by the NodeB. 
     Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for enabling layer 1 (L1, e.g., physical layer) and/or layer 2 (L2, e.g., medium access control (MAC) layer) inter-cell mobility. 
     The techniques presented herein may be applied in various bands utilized for NR. For example, for the higher band referred to as FR4 (e.g., 52.6 GHz-114.25 GHz), an OFDM waveform with very large subcarrier spacing (960 kHz-3.84 MHz) may be used to reduce severe phase noise. Due to the large subcarrier spacing, the slot length tends to be very short. In a lower band referred to as FR2 (24.25 GHz to 52.6 GHz) with 120 kHz SCS, the slot length is 125 μSec, while in FR4 with 960 kHz, the slot length is 15.6 μSec. 
     In multi-beam operation (e.g., involving FR1 and FR2 bands), more efficient uplink/downlink beam management may allow for increased intra-cell and inter-cell mobility (e.g., L1 and/or L2-centric mobility) and/or a larger number of transmission configuration indicator (TCI) states. For example, the TCI states may include the use of a common beam for transmitting and/or receiving data and/or control signaling, a unified TCI framework for UL and DL beam indication, and signaling mechanisms that improve latency and efficiency (e.g., dynamic usage of control signaling). 
     Some features may facilitate UL beam selection for UEs equipped with multiple panels. For example, UL beam selection may be facilitated through UL beam indication based on a unified TCI framework, enabling simultaneous transmission across multiple panels, and enabling fast panel selection. Further, UE-initiated or L1-event-driven beam management may also reduce latency and the probability that beam failure events occur. In UE-initiated beam management, a UE may select and indicate to a network entity beams to use for subsequent for subsequent communications using physical layer signaling or other higher level signaling, which imposes a lower processing overhead than radio resource control (RRC) signaling or other higher level signaling that may be used for signaling beam management, initiating mobility operations, and the like. Beam selection and management may be performed by the UE independently of instructions to do so from a network entity to reduce a likelihood that beam failure events, and corresponding instability of a connection or loss of connectivity between the UE and a network entity, will occur. 
     Additional techniques for multi-TRP deployment may target both FR1 and FR2 bands. These enhancements may improve reliability and robustness for channels other than the PDSCH (e.g., PDCCH, PUSCH, and PUCCH) using multi-TRP and/or multi-panel operations. These techniques may, in some cases, be related to quasi co-location (QCI) and TCI that may enable inter-cell multi-TRP operations and may allow for simultaneous multi-TRP transmission with multi-panel reception, assuming multi-DCI-based multi-PDSCH reception. 
     Still further techniques may support single frequency networks (SFNs) in high speed environments (e.g., in the High Speed Train (HST) scenario). These may include QCL assumptions for demodulation reference signals (DMRS), such as multiple QCL assumptions for the same DMRS ports and/or targeting downlink-only transmission. In some cases, the enhancements may specify a QCL or QCL-like relation, including applicable QCL types and associated requirements, between downlink and uplink signals by using a unified TCI framework. 
     In some operating environments, each serving cell may have an RRC-configured serving cell ID and an RRC-configured physical cell indicator (PCI). A UE may also acquire the physical cell identifier from the synchronization signal block (SSB) of the serving cell. 
     To enable L1 (e.g., physical layer)/L2 (e.g., medium access control (MAC) layer) based inter-cell mobility, a gNB may need to know whether a UE supports L1/L2 based inter-cell mobility. L1/L2 based inter-cell mobility may include various operating modes, the properties of each of which may be defined a priori and support for each of which may be signaled to a gNB as discussed in further detail below. In a first operating mode, each serving cell can have a PCI and multiple physical cell sites (e.g., remote radio headers (RRHs)). Each RRH may transmit a different set of SSB IDs using the same PCI. A DCI or MAC-CE may select which RRH or corresponding SSB to serve the UE based on signal strength metrics (e.g., reference signal received power (RSRP) per reported SSB ID. 
     In another operating mode, each serving cell may be configured with multiple PCIs. Each RRH of the serving cell can use one of the multiple PCIs configured for the serving cell and can transmit the full set of SSB IDs configured for the cell. A DCI or MAC-CE can select which RRH(s) or corresponding PCI(s) and/or SSB(s) to serve the UE based on signal strength metrics (e.g., RSRP) for each reported SSB ID and for each reported PCI. 
     In still another operating mode, each serving cell may be configured with a single PCI. A DCI or MAC-CE can identify serving cell(s) or corresponding serving cell ID(s) to serve the UE based on signal strength metrics (e.g., RSRP) for each reported SSB ID and for each reported PCI. 
     While the above refers to selection or use of SSBs, it should be understood that other cell-identifying reference signals may be used to identify a serving cell to serve a UE. For example, channel state information (CSI) reference signals (CSI-RS) or positioning reference signals (PRSs) can be used to identify the serving cell(s) to serve the UE. 
       FIG. 4  illustrates example operations  400  that may be performed by a UE to signal a capability to perform L1/L2 mobility, in accordance with certain aspects of the present disclosure. Operations  400  may be performed, for example, by a UE  120  illustrated in  FIGS. 1 and 2 . 
     As illustrated, operations  400  begin, at  402 , where the UE transmit, to a network entity, a report including information about a capability of the UE to support one or more inter-cell mobility procedures based on at least one of physical (PHY) layer or medium access control (MAC) layer signaling. The report may include an indication in one or more bits of a field in the report indicating whether the UE supports inter-cell mobility procedures based on PHY or MAC layer signaling. A first value in the field may indicate that the UE supports inter-cell mobility procedures based on PHY or MAC layer signaling, while a second value in the field may indicate that the UE does not support inter-cell mobility procedures based on PHY or MAC layer signaling. The reported capability may be reported on a generalized basis (e.g., a capability applicable across a plurality of operating modes) or reported on a per-operating-mode basis. 
     At  404 , the UE receives physical (PHY) layer or MAC layer signaling related to an inter-cell mobility procedure. The PHY or MAC layer signaling may include information that may aid a UE in handing over from a source cell or a target cell using higher layer signaling. For example, the PHY or MAC layer signaling may include an identifier of a target cell to which the UE is to hand over and communicate in response to receiving the PHY or MAC layer signaling, a cell selection command including a plurality of candidate target cells from which the UE can choose for handover, or the like. 
     At  406 , the UE initiates at least one of the inter-cell mobility procedures based on the PHY layer or MAC layer signaling related to the inter-cell mobility procedure. For example, the UE may perform a handover from a current serving cell to a target cell identified in the PHY or MAC layer signaling, and after handing over to the target cell, continue communications in a wireless network through the target cell. 
       FIG. 5  illustrates example operations that may be performed by a network entity to enable L1/L2 mobility, in accordance with certain aspects of the present disclosure. Operations  500  may be performed, for example, by a base station  110  illustrated in  FIGS. 1 and 2 . 
     As illustrated, operations  500  begin, at  502 , where the network entity receives a report, from a user equipment (UE), indicating a capability of the UE to support one or more inter-cell mobility procedures based on at least one of physical layer or medium access control (MAC) layer signaling. As discussed, the report may include an indication in one or more bits of a field in the report indicating whether the UE supports inter-cell mobility procedures based on PHY or MAC layer signaling. A first value in the field may indicate that the UE supports inter-cell mobility procedures based on PHY or MAC layer signaling, while a second value in the field may indicate that the UE does not support inter-cell mobility procedures based on PHY or MAC layer signaling. The reported capability may be reported on a generalized basis (e.g., a capability applicable across a plurality of operating modes) or reported on a per-operating-mode basis. 
     At  504 , the network entity sends the UE physical (PHY) layer or MAC layer signaling related to an inter-cell mobility procedure. The PHY layer or MAC layer signaling may include information indicating that inter-cell mobility procedures based on PHY or MAC layer signaling is activated and may include PHY layer or MAC layer signaling for cell selection. The cell selection signaling may include information identifying a target cell (e.g., a PCI) or information identifying a candidate set of cells from which the UE can choose for cell reselection. 
     In some examples, the UE may report one capability for L1/L2-based inter-cell mobility. The reported capability may be a capability applicable to each of the operating modes discussed above (e.g., applicable to a mode in which each serving cell has a PCI and multiple physical cell sites, a mode in which the serving cell is configured with multiple PCIs, and a mode in which each serving cell is configured with a single PCI and a DCI or MAC-CE identifies serving cells or serving cell IDs for the UE). In a mode in which each serving cell has a PCI and multiple physical cell sites, a UE may hand over to any of the multiple physical cell sites associated with the serving cell having the PCI using L1/L2 signaling. In such a case, the UE may report a capability to hand over to any of the multiple cell sites belonging to a serving cell with a particular PCI. In a mode in which each serving cell is configured with multiple PCIs, a UE may hand over to any cell configured with a specified PCI using L1/L2 signaling. The cell to which the UE hands over may be, for example, the cell having a highest signal strength of a plurality of detected cells, and the UE may report its ability to measure and hand over to a serving cell having multiple PCIs. Finally, in a mode in which each serving cell is configured with a single PCI, and a DCI or MAC-CE identifies a serving cell or serving cell IDs for the UE, the UE may hand over to the serving cell identified in the DCI or MAC-CE (e.g., the serving cell associated with the PCI included in the DCI or MAC-CE). 
     In some examples, the UE may report capabilities on a per-operating-mode basis (e.g., report capabilities associated with each operating mode for L1/L2-based mobility individually). That is, the UE may report a first capability for an operating mode in which each serving cell has a PCI and multiple physical cell sites, a second capability for an operating mode in which the serving cell is configured with multiple PCIs, and a third capability for an operating mode in which serving cell is configured with a single PCI and a DCI or MAC-CE identifies serving cells or serving cell IDs for the UE. When the UE reports capabilities on a per-operating-mode basis, the UE may hand over from one cell to another cell based on the configuration of cells in the network and the corresponding operating mode configuration reported to the network. 
     A network entity (e.g., a base station or gNodeB) may indicate, to the UE, the enablement of a corresponding L1/L2-based inter-cell mobility operation via various signaling mechanisms. The indication may be included, for example, in radio resource control (RRC) signaling, a MAC-CE, or a downlink control information (DCI). In some examples, the indication may be based on the configuration of an RRC parameter. For example, a first value or configuration for the RRC parameter may indicate enablement of a corresponding L1/L2-based inter-cell mobility operation, while a second value or configuration for the RRC parameter may indicate disablement of a corresponding L1/L2-based inter-cell mobility operation. After receiving the enablement indication from the network entity, the UE may be ready to perform L1/L2 cell selection based on a received DCI or MAC-CE. 
       FIG. 6  is a call flow diagram illustrating an example of messages exchanged between a UE and base stations for enabling L1/L2 based mobility and handing over to a new base station. As illustrated, a UE  602  signals, to a first base station  604  (e.g., a serving gNodeB), a UE capability to support L1/L2 mobility  610 . As discussed, the signaling of the UE capability to support L1/L2 mobility may include information about capabilities to support L1/L2 mobility generally or on a per-operating-mode basis. 
     Based on the indication that the UE  602  supports L1/L2 mobility, the first base station  604  sends an L1/L2 cell selection command  612  to the UE  602 . The L1/L2 cell selection command may include an indication of a target cell for the UE  602  to communicate with. The indication of the target cell with which the UE is to communicate may be, for example, a cell identifier (e.g., a PCI), a set of SSB IDs associated with the target cell with which the UE is to communicate, or other information that identifies the target cell. Upon receipt of L1/L2 cell selection command  612 , at block  614 , the UE discontinues communications with the first base station  604  and initiates communications with the second base station  606  (e.g., the cell indicated in the L1/L2 cell selection command). Subsequently, the UE communicates  616  with (i.e., transmits data and control signaling to, and receives data and control signaling from) the second base station  606 . 
       FIG. 7  illustrates a communications device  700  that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in  FIG. 4 . The communications device  700  includes a processing system  702  coupled to a transceiver  708  (e.g., a transmitter and/or a receiver). The transceiver  708  is configured to transmit and receive signals for the communications device  700  via an antenna  710 , such as the various signals as described herein. The processing system  702  may be configured to perform processing functions for the communications device  700 , including processing signals received and/or to be transmitted by the communications device  700 . 
     The processing system  702  includes a processor  704  coupled to a computer-readable medium/memory  712  via a bus  706 . In certain aspects, the computer-readable medium/memory  712  is configured to store instructions (e.g., computer-executable code) that when executed by the processor  704 , cause the processor  704  to perform the operations illustrated in  FIG. 4 , or other operations for performing the various techniques discussed herein for a beam switching gap. In certain aspects, computer-readable medium/memory  712  stores code  714  for transmitting, to a network entity, a report indicating a capability of the UE to support one or more inter-cell mobility procedures based on at least one of physical (PHY) layer or medium access control (MAC) layer signaling; code  716  for receiving PHY layer or MAC layer signaling related to an inter-cell mobility procedure; and code  718  for initiating at least one of the inter-cell mobility procedures based on the received PHY layer or MAC layer signaling, in accordance with aspects of the present disclosure. In certain aspects, the processor  704  has circuitry configured to implement the code stored in the computer-readable medium/memory  712 . The processor  704  includes circuitry  720  for transmitting, to a network entity, a report indicating a capability of the UE to support one or more inter-cell mobility procedures based on at least one of physical (PHY) layer or medium access control (MAC) layer signaling; circuitry  722  for receiving PHY layer or MAC layer signaling related to an inter-cell mobility procedure; and circuitry  724  for initiating at least one of the inter-cell mobility procedures based on the received PHY layer or MAC layer signaling, in accordance with aspects of the present disclosure. 
       FIG. 8  illustrates a communications device  800  that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in  FIG. 5 . The communications device  800  includes a processing system  802  coupled to a transceiver  808  (e.g., a transmitter and/or a receiver). The transceiver  808  is configured to transmit and receive signals for the communications device  800  via an antenna  810 , such as the various signals as described herein. The processing system  802  may be configured to perform processing functions for the communications device  800 , including processing signals received and/or to be transmitted by the communications device  800 . 
     The processing system  802  includes a processor  804  coupled to a computer-readable medium/memory  812  via a bus  806 . In certain aspects, the computer-readable medium/memory  812  is configured to store instructions (e.g., computer-executable code) that when executed by the processor  804 , cause the processor  804  to perform the operations illustrated in  FIG. 5 , or other operations for performing the various techniques discussed herein for a beam switching gap. In certain aspects, computer-readable medium/memory  812  stores code  814  for receiving reporting, from a user equipment (UE), indicating a capability of the UE to support one or more inter-cell mobility procedures based on at least one of physical layer or medium access control (MAC) layer signaling; and code  816  for sending the UE physical layer or MAC layer signaling related to an inter-cell mobility procedure, in accordance with aspects of the present disclosure. In certain aspects, the processor  804  has circuitry configured to implement the code stored in the computer-readable medium/memory  812 . The processor  804  includes circuitry  818  for receiving reporting, from a user equipment (UE), indicating a capability of the UE to support one or more inter-cell mobility procedures based on at least one of physical layer or medium access control (MAC) layer signaling; and circuitry  820  for sending the UE physical layer or MAC layer signaling related to an inter-cell mobility procedure, in accordance with aspects of the present disclosure. 
     The techniques described herein may be used for various wireless communication technologies, such as NR (for example, 5G NR), 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. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement a radio technology such as NR (e.g. 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). LTE and LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). NR is an emerging wireless communications technology under development. 
     The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, while aspects may be described herein using terminology commonly associated with 3G, 4G, or 5G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems. 
     In 3GPP, the term “cell” can refer to a coverage area of a Node B (NB) or a NB subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term “cell” and BS, next generation NodeB (gNB or gNodeB), access point (AP), distributed unit (DU), carrier, or transmission reception point (TRP) may be used interchangeably. A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, or other types of cells. A macro cell may cover a relatively large geographic area (for example, several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (for example, a home) and may allow restricted access by UEs having an association with the femto cell (for example, UEs in a Closed Subscriber Group (CSG), UEs for users in the home, etc.). A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. ABS for a femto cell may be referred to as a femto BS or a home BS. 
     A UE may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a Customer Premises Equipment (CPE), a cellular phone, a smart phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (for example, a smart ring, a smart bracelet, etc.), an entertainment device (for example, a music device, a video device, a satellite radio, etc.), a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. Some UEs may be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that may communicate with a BS, another device (for example, remote device), or some other entity. A wireless node may provide, for example, connectivity for or to a network (for example, a wide area network such as Internet or a cellular network) via a wired or wireless communication link. Some UEs may be considered Internet-of-Things (IoT) devices, which may be narrowband IoT (NB-IoT) devices. 
     Some wireless networks (for example, LTE) utilize orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, etc. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth. For example, the spacing of the subcarriers may be 15 kHz and the minimum resource allocation (called a “resource block” (RB)) may be 12 subcarriers (or 180 kHz). Consequently, the nominal Fast Fourier Transfer (FFT) size may be equal to 128, 256, 512, 1024 or 2048 for system bandwidth of 1.25, 2.5, 5, 10, or 20 megahertz (MHz), respectively. The system bandwidth may also be partitioned into subbands. For example, a subband may cover 1.08 MHz (for example, 6 RBs), and there may be 1, 2, 4, 8, or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively. In LTE, the basic transmission time interval (TTI) or packet duration is the 1 ms subframe. 
     NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using TDD. In NR, a subframe is still 1 ms, but the basic TTI is referred to as a slot. A subframe contains a variable number of slots (for example, 1, 2, 4, 8, 16, . . . slots) depending on the subcarrier spacing. The NR RB is 12 consecutive frequency subcarriers. NR may support a base subcarrier spacing of 15 KHz and other subcarrier spacing may be defined with respect to the base subcarrier spacing, for example, 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc. The symbol and slot lengths scale with the subcarrier spacing. The CP length also depends on the subcarrier spacing. Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. In some examples, MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. In some examples, multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells. 
     In some examples, access to the air interface may be scheduled. A scheduling entity (for example, a BS) allocates resources for communication among some or all devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. Base stations are not the only entities that may function as a scheduling entity. In some examples, a UE may function as a scheduling entity and may schedule resources for one or more subordinate entities (for example, one or more other UEs), and the other UEs may utilize the resources scheduled by the UE for wireless communication. In some examples, a UE may function as a scheduling entity in a peer-to-peer (P2P) network, or in a mesh network. In a mesh network example, UEs may communicate directly with one another in addition to communicating with a scheduling entity. 
     As used herein, the term “determining” may encompass one or more of a wide variety of actions. For example, “determining” may include calculating, computing, processing, deriving, investigating, looking up (for example, looking up in a table, a database or another data structure), assuming and the like. Also, “determining” may include receiving (for example, receiving information), accessing (for example, accessing data in a memory) and the like. Also, “determining” may include resolving, selecting, choosing, establishing and the like. 
     As used herein, “or” is used intended to be interpreted in the inclusive sense, unless otherwise explicitly indicated. For example, “a or b” may include a only, b only, or a combination of a and b. As used herein, a phrase referring to “at least one of” or “one or more of” a list of items refers to any combination of those items, including single members. For example, “at least one of: a, b, or c” is intended to cover the possibilities of: a only, b only, c only, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a and b and c. 
     The various illustrative components, logic, logical blocks, modules, circuits, operations and algorithm processes described in connection with the implementations disclosed herein may be implemented as electronic hardware, firmware, software, or combinations of hardware, firmware or software, including the structures disclosed in this specification and the structural equivalents thereof. The interchangeability of hardware, firmware and software has been described generally, in terms of functionality, and illustrated in the various illustrative components, blocks, modules, circuits and processes described above. Whether such functionality is implemented in hardware, firmware or software depends upon the particular application and design constraints imposed on the overall system. 
     Various modifications to the implementations described in this disclosure may be readily apparent to persons having ordinary skill in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the claims are not intended to be limited to the implementations shown herein, but are to be accorded the widest scope consistent with this disclosure, the principles and the novel features disclosed herein. 
     Additionally, various features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. As such, although features may be described above as acting in particular combinations, and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one or more example processes in the form of a flowchart or flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In some circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.