WO2021127582A2

WO2021127582A2 - Inter-cell mobility and signaling techniques

Info

Publication number: WO2021127582A2
Application number: PCT/US2020/066235
Authority: WO
Inventors: Hamed Pezeshki; Yan Zhou; Tao Luo
Original assignee: Qualcomm Incorporated
Priority date: 2019-12-20
Filing date: 2020-12-18
Publication date: 2021-06-24
Also published as: WO2021127582A9; WO2021127582A3

Abstract

A user equipment (UE) can connect with a network including a plurality of cells. The UE can use layer 1 (L1) and/or layer 2 (L2) signaling to perform L1/L2 centric inter-cell mobility operations among the plurality of cells. Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for selecting an initial beam or default beam in L1 (physical layer) and L2 (medium access control (MAC) layer) based inter-cell mobility. In some aspects, when the UE experiences a beam or radio link failure on a current connection with the network, the UE can fall back to an anchor cell from the plurality of cells and performs a fallback operation on the anchor cell in order to reestablish or maintain communication with the plurality of cells.

Description

INTER-CELL MOBILITY AND SIGNALING TECHNIQUES

CROSS REFERNCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of provisional patent application no. 62/952, 191 filed in the United States Patent Office on December 20, 2019, provisional patent application no. 62/952,194 filed in the United States Patent Office on December 20, 2019, provisional patent application no. 62/952,905 filed in the United States Patent Office on December 23, 2019, provisional patent application no. 62/953,086, filed in the United States Patent Office on December 23, 2019, provisional patent application no. 62/962,132 filed in the United States Patent Office on January 16, 2020, the entire content of each prior application is incorporated herein by reference as if fully set forth below in its entirety and for all applicable purposes.

TECHNICAL FIELD

[0002] The technology discussed below relates generally to wireless communication systems, and more particularly, to facilitating mobility within wireless networks. Some aspects relate to one or more of: anchor cells to facilitate Layer 1 (Ll)/Layer 2 (L2)- Centric Inter-Cell Mobility; default beams used for communications (e.g., PDSCH beam determination); initial beam selection(s) for communicating (e.g., with a new cell indicated via inter-cell mobility signaling via physical layer (PHY) or medium access control (MAC) layer signaling); and default beam to use in communicating with a cell in physical layer (PHY) or medium access control (MAC) layer signaling.

INTRODUCTION

[0003] In some wireless technologies and standards, such as the evolving 3GPP 5G New

Radio (NR) standard, high frequency transmission waveforms and protocols, and multiple transmission/reception points (multi-TRP) have been proposed. These proposals provide enhancements for multi-beam operation, particularly for high frequency transmissions as well as for multi-TRP deployments. Other proposed enhancements include improving inter-cell mobility. Exemplary aspects disclosed herein generally enable and provide techniques for improved inter-cell mobility and mobility signaling. SUMMARY

[0004] The following presents a summary of one or more aspects of the present disclosure, in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated features of the disclosure, and is intended neither to identify key or critical elements of all aspects of the disclosure nor to delineate the scope of any or all aspects of the disclosure. Its sole purpose is to present some concepts of one or more aspects of the disclosure in a simplified form as a prelude to the more detailed description that is presented later.

[0005] One 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 receiving a command to switch from a current cell to a new cell signaled via physical layer or medium access control (MAC) layer signaling, determining an initial beam to use for at least one of uplink or downlink transmissions in the new cell before the UE receives a transmission configuration indicator (TCI) activation or configuration command, and communicating in the new cell using the initial beam.

[0006] One 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 transmitting, to a UE, a command to switch from a current cell to a new cell signaled via physical layer or MAC layer signaling, determining an initial beam for the UE to use for at least one of uplink or downlink transmissions in the new cell before the UE receives a TCI activation or configuration command, and communicating with the UE in the new cell using the initial beam.

[0007] One aspect of the subject matter described in this disclosure can be implemented in a method for wireless communication by a UE. The method generally includes receiving a command, signaled via physical layer or MAC layer signaling, that indicates at least one of: at least one cell or at least one physical cell ID (PCI) to serve the UE, determining a default beam for a physical downlink shared channel (PDSCH) transmission in the indicated cell or PCI cell, and communicating in the new cell using the default beam.

[0008] One 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 transmitting, to a user equipment (UE), a command, signaled via physical layer or MAC layer signaling, that indicates at least one of: at least one cell or at least one PCI to serve the UE, determining a default beam for the UE for a PDSCH transmission in the indicated cell or PCI cell, and communicating with the UE in the new cell using the default beam.

[0009] One aspect of the disclosure provides a method of wireless communication at a scheduled entity. The scheduled entity connects with at least one of a plurality of cells using signaling including at least one of layer 1 (LI) signaling or layer 2 (L2) signaling. The scheduled entity determines a fallback condition or the existence of the fallback condition. The scheduled entity selects an anchor cell from the plurality of cells based on a predetermined rule. The predetermined rule includes at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell. Then, the scheduled entity perform, in response to the fallback condition, a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

[0010] One aspect of the disclosure provides a scheduled entity for wireless communication. The scheduled entity includes a communication interface configured for wireless communication with a scheduling entity, a memory, and a processor operatively coupled with the communication interface and the memory. The processor and the memory are configured to connect with at least one of a plurality of cells using signaling including at least one of LI signaling or L2 signaling. The processor and the memory are configured to determine a fallback condition or the existence of the fallback condition. The processor and the memory are configured to select an anchor cell from the plurality of cells based on a predetermined rule. The predetermined rule includes at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell. Then, the processor and the memory are configured to perform, in response to the fallback condition, a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

[0011] One aspect of the disclosure provides a method of wireless communication at a scheduling entity. The scheduling entity configures a scheduled entity to connect with at least one of a plurality of cells using signaling including at least one of LI signaling or L2 signaling. The scheduling entity configures the scheduled entity to determine a fallback condition or the existence of the fallback condition. The scheduling entity configures the scheduled entity to select an anchor cell from the plurality of cells based on a predetermined rule. The predetermined rule includes at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell. Then, the scheduling entity configures the scheduled entity, in response to the fallback condition, to perform a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

[0012] One aspect of the disclosure provides a scheduling entity for wireless communication. The scheduling entity includes a communication interface configured for wireless communication with a scheduled entity, a memory, and a processor operatively coupled with the communication interface and the memory. The processor and the memory are configured to configure the scheduled entity to connect with at least one of a plurality of cells using signaling including at least one of LI signaling or L2 signaling. The processor and the memory are configured to configure the scheduled entity to determine a fallback condition or the existence of the fallback condition. The processor and the memory are configured to configure the scheduled entity to select an anchor cell from the plurality of cells based on a predetermined rule. The predetermined rule includes at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell. Then, the processor and the memory are configured to configure the scheduled entity, in response to the fallback condition, to perform a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

[0013] These and other aspects of the invention will become more fully understood upon a review of the detailed description, which follows. Other aspects, features, and embodiments will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific, exemplary embodiments in conjunction with the accompanying figures. While features may be discussed relative to certain embodiments and figures below, all embodiments can include one or more of the advantageous features discussed herein. In other words, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various embodiments discussed herein. In similar fashion, while exemplary embodiments may be discussed below as device, system, or method embodiments it should be understood that such exemplary embodiments can be implemented in various devices, systems, and methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a schematic illustration of a wireless communication system according to some aspects.

[0015] FIG. 2 is an illustration of an example of a radio access network according to some aspects.

[0016] FIG. 3 is a block diagram illustrating a wireless communication system supporting multiple-input multiple-output (MIMO) communication.

[0017] FIG. 4 is a schematic illustration of an organization of wireless resources in an air interface utilizing orthogonal frequency divisional multiplexing (OFDM) according to some aspects.

[0018] FIG. 5 is a diagram illustrating an example of a multiple transmission/reception points environment according to some aspects.

[0019] FIG. 6 is a diagram illustrating communication between a base station and a user equipment (UE) using beamformed signals according to some aspects.

[0020] FIG. 7 illustrates a radio protocol architecture for wireless communication according to some aspects.

[0021] FIG. 8 illustrates exemplary operations at a UE for identifying an initial beam to use in communicating with a selected cell in Ll/L2-based mobility according to some aspects.

[0022] FIG. 9 illustrates exemplary operations at a network identity for identifying an initial beam to use in communications with a UE in Ll/L2-based mobility according to some aspects.

[0023] FIG. 10 is a call flow diagram illustrating an example of identifying an initial beam to use in communicating with a new cell in L1/L2 based mobility procedures.

[0024] FIG. 11 illustrates exemplary operations at a UE for identifying a default beam to use in communicating with a selected cell in Ll/L2-based mobility according to some aspects.

[0025] FIG. 12 illustrates exemplary operations at a network entity for identifying a default beam to use in communicating with a UE in Ll/L2-based mobility according to some aspects.

[0026] FIG. 13 is a call flow diagram illustrating an example of determining and using a default physical downlink shared channel (PDSCH) beam in Ll/L2-based mobility procedures. [0027] FIG. 14 is a flow chart illustrating a process for wireless communication using Ll/L2-centric inter-cell mobility according to some aspects.

[0028] FIG. 15 is a flow chart illustrating a first exemplary process for selecting an anchor cell for L1/L2 centric inter-cell mobility according to some aspects.

[0029] FIG. 16 is a flow chart illustrating a second exemplary process for selecting an anchor cell for L1/L2 centric inter-cell mobility according to some aspects.

[0030] FIG. 17 is a block diagram illustrating an example of a hardware implementation for a scheduling entity employing a processing system in accordance with aspects disclosed herein.

[0031] FIG. 18 is a flow chart illustrating an exemplary scheduling entity process that facilitates some aspects of the disclosure.

[0032] FIG. 19 is a block diagram illustrating an example of a hardware implementation for a scheduled entity employing a processing system in accordance with aspects disclosed herein.

[0033] FIG. 20 is a flow chart illustrating an exemplary scheduled entity process that facilitates some aspects of the disclosure.

DETAILED DESCRIPTION

[0034] The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0035] The electromagnetic spectrum is often subdivided, based on frequency/wavelength, into various classes, bands, channels, etc. In 5G NR two initial operating bands have been identified as frequency range designations FR1 (410 MHz - 7.125 GHz) and FR2 (24.25 GHz - 52.6 GHz). It should be understood that although a portion of FR1 is greater than 6 GHz, FR1 is often referred to (interchangeably) as a “Sub- 6 GHz” band in various documents and articles. A similar nomenclature issue sometimes occurs with regard to FR2, which is often referred to (interchangeably) as a “millimeter wave” band in documents and articles, despite being different from the extremely high frequency (EHF) band (30 GHz - 300 GHz) which is identified by the International Telecommunications Union (ITU) as a “millimeter wave” band.

[0036] The frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Recent 5GNR studies have identified an operating band for these mid-band frequencies as frequency range designation FR3 (7.125 GHz - 24.25 GHz). Frequency bands falling within FR3 may inherit FR1 characteristics and/or FR2 characteristics, and thus may effectively extend features of FR1 and/or FR2 into mid-band frequencies. In addition, higher frequency bands are currently being explored to extend 5G NR operation beyond 52.6 GHz. For example, three higher operating bands have been identified as frequency range designations FR4-a or FR4-1 (52.6 GHz - 71 GHz), FR4 (52.6 GHz - 114.25 GHz), and FR5 (114.25 GHz - 300 GHz). Each of these higher frequency bands falls within the EHF band.

[0037] With the above aspects in mind, unless specifically stated otherwise, it should be understood that the term “sub-6 GHz” or the like if used herein may broadly represent frequencies that may be less than 6 GHz, may be within FR1, or may include mid-band frequencies. Further, unless specifically stated otherwise, it should be understood that the term “millimeter wave” or the like if used herein may broadly represent frequencies that may include mid-band frequencies, may be within FR2, FR4, FR4-a or FR4-1, and/or FR5, or may be within the EHF band.

[0038] While aspects and embodiments are described in this application by illustration to some examples, those skilled in the art will understand that additional implementations and use cases may come about in many different arrangements and scenarios. Innovations described herein may be implemented across many differing platform types, devices, systems, shapes, sizes, and packaging arrangements. For example, embodiments and/or uses may come about via integrated chip embodiments and other non-module-component based devices (e.g., end-user devices, vehicles, communication devices, computing devices, industrial equipment, retail/purchasing devices, medical devices, Al-enabled devices, etc.). While some examples may or may not be specifically directed to use cases or applications, a wide assortment of applicability of described innovations may occur. Implementations may range a spectrum from chip-level or modular components to non- modular, non-chip-level implementations and further to aggregate, distributed, or OEM devices or systems incorporating one or more aspects of the described innovations. In some practical settings, devices incorporating described aspects and features may also necessarily include additional components and features for implementation and practice of claimed and described embodiments. For example, transmission and reception of wireless signals necessarily includes a number of components for analog and digital purposes (e.g., hardware components including antenna, RF-chains, power amplifiers, modulators, buffer, processor(s), interleaver, adders/summers, etc.). It is intended that innovations described herein may be practiced in a wide variety of devices, chip-level components, systems, distributed arrangements, end-user devices, etc. of varying sizes, shapes and constitution.

[0039] Of note, for 5G New Radio (NR) systems, inter-cell mobility may be configured to be layer 1 (i.e., the LI or PHY layer) or layer 2 (i.e., the L2 or MAC layer) centric (i.e., Ll/L2-centric). It is noted that within the 5G NR framework, various operation modes for such Ll/L2-centric inter-cell mobility may be possible for different operational scenarios as will be further described herein.

[0040] Various aspects directed towards Ll/L2-Centric Inter-Cell Mobility are disclosed.

Some aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for selecting an initial beam to use in communicating with a new cell indicated via inter-cell mobility signaling via physical layer (PHY)/L1 or medium access control (MAC) layer/L2 signaling, and for identifying a default beam to use in communicating with a cell in L1/L2 inter-cell mobility.

[0041] In one example, aspects are directed towards a scheduled entity (e.g., a user equipment (UE)). For this example, the scheduled entity may connect with at least one of a plurality of cells based on L1/L2 signaling, which includes a first portion including physical layer signaling and/or a second portion including medium access control (MAC) layer signaling. The scheduled entity may then select an anchor cell from the plurality of cells and perform a fallback operation on the anchor cell.

[0042] In another example, aspects are directed towards a scheduling entity (e.g., a gNode

B (gNB)). For instance, a scheduling entity may configure a scheduled entity to connect with at least one of a plurality of cells based on L1/L2 signaling, which includes a first portion including physical layer signaling and/or a second portion including MAC layer signaling. For this example, the scheduling entity may configure the scheduled entity to select an anchor cell from the plurality of cells and to perform a fallback operation on the anchor cell.

[0043] The following description provides examples of selecting an initial beam to use in communicating with a new cell indicated via inter-cell mobility signaling via physical layer (PHY) or medium access control (MAC) layer signaling, and is not limiting of the scope, applicability, or examples set forth in the claims.

[0044] The following description provides examples of identifying a default beam to use in communicating with a cell in L1/L2 inter-cell mobility, and is not limiting of the scope, applicability, or examples set forth in the claims.

[0045] Turning to the drawings, the various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. Referring to FIG. 1, as an illustrative example without limitation, various aspects of the present disclosure are illustrated with reference to a wireless communication system 100. The wireless communication system 100 includes three interacting domains: a core network 102, a radio access network (RAN) 104, and a user equipment (UE) 106. By virtue of the wireless communication system 100, the UE 106 may be enabled to carry out data communication with an external data network 110, such as (but not limited to) the Internet.

[0046] The RAN 104 may implement any suitable wireless communication technology or technologies to provide radio access to the UE 106. As one example, the RAN 104 may operate according to 3^rd Generation Partnership Project (3GPP) New Radio (NR) specifications, often referred to as 5G. As another example, the RAN 104 may operate under a hybrid of 5G NR and Evolved Universal Terrestrial Radio Access Network (eUTRAN) standards, often referred to as LTE. The 3GPP refers to this hybrid RAN as a next-generation RAN, or NG-RAN. Of course, many other examples may be utilized within the scope of the present disclosure.

[0047] As illustrated, the RAN 104 includes a plurality of base stations 108. Broadly, a base station is a network element in a radio access network responsible for radio transmission and reception in one or more cells to or from a UE. In different technologies, standards, or contexts, a base station may variously be referred to by those skilled in the art as a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), a Node B (NB), an eNode B (eNB), a gNode B (gNB), a transmission and reception point (TRP), or some other suitable terminology. In some examples, a base station may include two or more TRPs that may be collocated or non-collocated. Each TRP may communicate on the same or different carrier frequency within the same or different frequency band. [0048] The radio access network 104 is further illustrated supporting wireless communication for multiple mobile apparatuses. A mobile apparatus may be referred to as user equipment (UE) in 3GPP standards, but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. A UE may be an apparatus (e.g., a mobile apparatus) that provides a user with access to network services.

[0049] Within the present document, a “mobile” apparatus need not necessarily have a capability to move, and may be stationary. The term mobile apparatus or mobile device broadly refers to a diverse array of devices and technologies. UEs may include a number of hardware structural components sized, shaped, and arranged to help in communication; such components can include antennas, antenna arrays, RF chains, amplifiers, one or more processors, etc. electrically coupled to each other. For example, some non-limiting examples of a mobile apparatus include a mobile, a cellular (cell) phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal computer (PC), a notebook, a netbook, a smartbook, a tablet, a personal digital assistant (PDA), and a broad array of embedded systems, e.g., corresponding to an “Internet of things” (IoT). A mobile apparatus may additionally be an automotive or other transportation vehicle, a remote sensor or actuator, a robot or robotics device, a satellite radio, a global positioning system (GPS) device, an object tracking device, a drone, a multi-copter, a quad-copter, a remote control device, a consumer and/or wearable device, such as eyewear, a wearable camera, a virtual reality device, a smart watch, a health or fitness tracker, a digital audio player (e.g., MP3 player), a camera, a game console, etc. A mobile apparatus may additionally be a digital home or smart home device such as a home audio, video, and/or multimedia device, an appliance, a vending machine, intelligent lighting, a home security system, a smart meter, etc. A mobile apparatus may additionally be a smart energy device, a security device, a solar panel or solar array, a municipal infrastructure device controlling electric power (e.g., a smart grid), lighting, water, etc.; an industrial automation and enterprise device; a logistics controller; agricultural equipment, etc. Still further, a mobile apparatus may provide for connected medicine or telemedicine support, e.g., health care at a distance. Telehealth devices may include telehealth monitoring devices and telehealth administration devices, whose communication may be given preferential treatment or prioritized access over other types of information, e.g., in terms of prioritized access for transport of critical service data, and/or relevant QoS for transport of critical service data.

[0050] Wireless communication between a RAN 104 and a UE 106 may be described as utilizing an air interface. Transmissions over the air interface from a base station (e.g., base station 108) to one or more UEs (e.g., UE 106) may be referred to as downlink (DL) transmission. In accordance with certain aspects of the present disclosure, the term downlink may refer to a point-to-multipoint transmission originating at a scheduling entity (described further below; e.g., base station 108). Another way to describe this scheme may be to use the term broadcast channel multiplexing. Transmissions from a UE (e.g., UE 106) to a base station (e.g., base station 108) may be referred to as uplink (UL) transmissions. In accordance with further aspects of the present disclosure, the term uplink may refer to a point-to-point transmission originating at a scheduled entity (described further below; e.g., UE 106).

[0051] For example, DL transmissions may include unicast or broadcast transmissions of control information and/or traffic information (e.g., user data traffic) from a base station (e.g., base station 210) to one or more UEs (e.g., UEs 222 and 224), while UL transmissions may include transmissions of control information and/or traffic information originating at a UE (e.g., UE 222). In addition, the uplink and/or downlink control information and/or traffic information may be time-divided into frames, subframes, slots, and/or symbols. As used herein, a symbol may refer to a unit of time that, in an orthogonal frequency division multiplexed (OFDM) waveform, carries one resource element (RE) per sub-carrier. A slot may carry 7 or 14 OFDM symbols. A subframe may refer to a duration of 1 ms. Multiple subframes or slots may be grouped together to form a single frame or radio frame. Of course, these definitions are not required, and any suitable scheme for organizing waveforms may be utilized, and various time divisions of the waveform may have any suitable duration.

[0052] In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a base station 108) allocates resources for communication among some or all devices and equipment within its service area or cell. Within the present disclosure, as discussed further below, the scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more scheduled entities. That is, for scheduled communication, UEs 106, which may be scheduled entities, may utilize resources allocated by the scheduling entity 108. [0053] Base stations 108 are not the only entities that may function as scheduling entities. That is, in some examples, a UE may function as a scheduling entity, scheduling resources for one or more scheduled entities (e.g., one or more other UEs).

[0054] As illustrated in FIG. 1, a scheduling entity 108 may broadcast downlink traffic

112 to one or more scheduled entities 106. Broadly, the scheduling entity 108 is a node or device responsible for scheduling traffic in a wireless communication network, including the downlink traffic 112 and, in some examples, uplink traffic 116 from one or more scheduled entities 106 to the scheduling entity 108. On the other hand, the scheduled entity 106 is a node or device that receives downlink control information 114, including but not limited to scheduling information (e.g., a grant), synchronization or timing information, or other control information from another entity in the wireless communication network such as the scheduling entity 108.

[0055] In general, base stations 108 may include a backhaul interface for communication with a backhaul portion 120 of the wireless communication system. The backhaul 120 may provide a link between a base station 108 and the core network 102. Further, in some examples, a backhaul network may provide interconnection between the respective base stations 108. Various types of backhaul interfaces may be employed, such as a direct physical connection, a virtual network, or the like using any suitable transport network.

[0056] The core network 102 may be a part of the wireless communication system 100, and may be independent of the radio access technology used in the RAN 104. In some examples, the core network 102 may be configured according to 5G standards (e.g., 5GC). In other examples, the core network 102 may be configured according to a 4G evolved packet core (EPC), or any other suitable standard or configuration.

[0057] Referring now to FIG. 2, by way of example and without limitation, a schematic illustration of a RAN 200 is provided. In some examples, the RAN 200 may be the same as the RAN 104 described above and illustrated in FIG. 1. The geographic area covered by the RAN 200 may be divided into cellular regions (cells) that can be uniquely identified by a user equipment (UE) based on an identification (e.g., a cell ID) broadcasted from one access point or base station. FIG. 2 illustrates macrocells 202, 204, and 206, and a small cell 208, each of which may include one or more sectors (not shown). A sector is a sub-area of a cell. All sectors within one cell are served by the same base station. A radio link within a sector can be identified by a single logical identification belonging to that sector. In a cell that is divided into sectors, the multiple sectors within a cell can be formed by groups of antennas with each antenna responsible for communication with UEs in a portion of the cell.

[0058] In FIG. 2, two base stations 210 and 212 are shown in cells 202 and 204; and a third base station 214 is shown controlling a remote radio head (RRH) 216 in cell 206. That is, a base station can have an integrated antenna or can be connected to an antenna or RRH by feeder cables. In the illustrated example, the cells 202, 204, and 126 may be referred to as macrocells, as the base stations 210, 212, and 214 support cells having a large size. Further, a base station 218 is shown in the small cell 208 (e.g., a microcell, picocell, femtocell, home base station, home Node B, home eNode B, etc.) which may overlap with one or more macrocells. In this example, the cell 208 may be referred to as a small cell, as the base station 218 supports a cell having a relatively small size. Cell sizing can be done according to system design as well as component constraints. In some aspects, each cell may have one or more physical cell IDs (PCIs) and have one or more physical cell sites (e.g., RRHs). In some aspects, each RRH may be associated with a different PCI.

[0059] It is to be understood that the radio access network 200 may include any number of wireless base stations and cells. Further, a relay node may be deployed to extend the size or coverage area of a given cell. The base stations 210, 212, 214, 218 provide wireless access points to a core network for any number of mobile apparatuses. In some examples, the base stations 210, 212, 214, and/or 218 may be the same as the base station/scheduling entity 108 described above and illustrated in FIG. 1.

[0060] FIG. 2 further includes a quadcopter or drone 220, which may be configured to function as a base station. That is, in some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile base station such as the quadcopter 220.

[0061] Within the RAN 200, the cells may include UEs that may be in communication with one or more sectors of each cell. Further, each base station 210, 212, 214, 218, and 220 may be configured to provide an access point to a core network 102 (see FIG. 1) for all the UEs in the respective cells. For example, UEs 222 and 224 may be in communication with base station 210; UEs 226 and 228 may be in communication with base station 212; UEs 230 and 232 may be in communication with base station 214 by way of RRH 216; UE 234 may be in communication with base station 218; and UE 236 may be in communication with mobile base station 220. In some examples, the UEs 222, 224, 226, 228, 230, 232, 234, 236, 238, 240, and/or 242 may be the same as the UE/scheduled entity 106 described above and illustrated in FIG. 1.

[0062] In some examples, a mobile network node (e.g., quadcopter 220) may be configured to function as a UE. For example, the quadcopter 220 may operate within cell 202 by communicating with base station 210.

[0063] In a further aspect of the RAN 200, sidelink signals may be used between UEs without necessarily relying on scheduling or control information from a base station. For example, two or more UEs (e.g., UEs 238 and 242) may communicate with each other using peer-to-peer (P2P) or sidelink signals 237 without relaying that communication through a base station (e.g., base station 212). In some examples, the UEs 238, 240, and 242 may each function as a scheduling entity or a transmitting sidelink device and/or a scheduled entity or a receiving sidelink device to schedule resources and communicate sidelink signals therebetween without relying on control information from a base station (e.g., gNB). In other examples, two or more UEs (e.g., UEs 226 and 228) within the coverage area of a base station (e.g., base station 212) may also communicate sidelink signals 227 over a direct link (sidelink) without conveying that communication through the base station 212. In this example, the base station 212 may allocate resources to the UEs 226 and 228 for the sidelink communication. In either case, such sidelink signaling 227 and 237 may be implemented in a P2P network, device-to-device (D2D) network, vehicle-to-vehicle (V2V) network, vehicle to everything (V2X) network, a mesh network, or other suitable direct link network.

[0064] In the radio access network 200, the ability for a UE to communicate while moving, independent of its location, is referred to as mobility. The various physical channels between the UE and the radio access network are generally set up, maintained, and released under the control of an access and mobility management function (AMF, not illustrated, part of the core network 102 in FIG. 1), which may include a security context management function (SCMF) and a security anchor function (SEAF) that performs authentication. The SCMF can manage, in whole or in part, the security context for both the control plane and the user plane functionality.

[0065] In various aspects of the disclosure, a radio access network 200 may utilize DL- based mobility or UL-based mobility to enable mobility and handovers (i.e., the transfer of a UE’ s connection from one radio channel to another). In a network configured for DL- based mobility, during a call with a scheduling entity, or at any other time, a UE may monitor various parameters of the signal from its serving cell as well as various parameters of neighboring cells. Depending on the quality of these parameters, the UE may maintain communication with one or more of the neighboring cells. During this time, if the UE moves from one cell to another, or if signal quality from a neighboring cell exceeds that from the serving cell for a given amount of time, the UE may undertake a handoff or handover from the serving cell to the neighboring (target) cell. For example, UE 224 (illustrated as a vehicle, although any suitable form of UE may be used) may move from the geographic area corresponding to its serving cell 202 to the geographic area corresponding to a neighbor cell 206. When the signal strength or quality from the neighbor cell 206 exceeds that of its serving cell 202 for a given amount of time, the UE 224 may transmit a reporting message to its serving base station 210 indicating this condition. In response, the UE 224 may receive a handover command, and the UE may undergo a handover to the cell 206.

[0066] In a network configured for UL-based mobility, UL reference signals from each

UE may be utilized by the network to select a serving cell for each UE. In some examples, the base stations 210, 212, and 214/216 may broadcast unified synchronization signals (e.g., unified Primary Synchronization Signals (PSSs), unified Secondary Synchronization Signals (SSSs) and unified Physical Broadcast Channels (PBCH)). The UEs 222, 224, 226, 228, 230, and 232 may receive the unified synchronization signals, derive the carrier frequency and slot timing from the synchronization signals, and in response to deriving timing, transmit an uplink pilot or reference signal. The uplink pilot signal transmitted by a UE (e.g., UE 224) may be concurrently received by two or more cells (e.g., base stations 210 and 214/216) within the radio access network 200. Each of the cells may measure a strength of the pilot signal, and the radio access network (e.g., one or more of the base stations 210 and 214/216 and/or a central node within the core network) may determine a serving cell for the UE 224. As the UE 224 moves through the radio access network 200, the network may continue to monitor the uplink pilot signal transmitted by the UE 224. When the signal strength or quality of the pilot signal measured by a neighboring cell exceeds that of the signal strength or quality measured by the serving cell, the network 200 may handover the UE 224 from the serving cell to the neighboring cell, with or without informing the UE 224.

[0067] Although the synchronization signal transmitted by the base stations 210, 212, and

214/216 may be unified, the synchronization signal may not identify a particular cell, but rather may identify a zone of multiple cells operating on the same frequency and/or with the same timing. The use of zones in 5G networks or other next generation communication networks enables the uplink-based mobility framework and improves the efficiency of both the UE and the network, since the number of mobility messages that need to be exchanged between the UE and the network may be reduced.

[0068] The air interface in the radio access network 200 may utilize one or more duplexing algorithms. Duplex refers to a point-to-point communication link where both endpoints can communicate with one another in both directions. Full-duplex means both endpoints can simultaneously communicate with one another. Half-duplex means only one endpoint can send information to the other at a time. Half-duplex emulation is frequently implemented for wireless links utilizing time division duplex (TDD). In TDD, transmissions in different directions on a given channel are separated from one another using time division multiplexing. That is, at some times the channel is dedicated for transmissions in one direction, while at other times the channel is dedicated for transmissions in the other direction, where the direction may change very rapidly, e.g., several times per slot. In a wireless link, a full-duplex channel generally relies on physical isolation of a transmitter and receiver, and suitable interference cancellation technologies. Full-duplex emulation is frequently implemented for wireless links by utilizing frequency division duplex (FDD) or spatial division duplex (SDD). In FDD, transmissions in different directions may operate at different carrier frequencies (e.g., within paired spectrum). In SDD, transmissions in different directions on a given channel are separated from one another using spatial division multiplexing (SDM). In other examples, full- duplex communication may be implemented within unpaired spectrum (e.g., within a single carrier bandwidth), where transmissions in different directions occur within different sub-bands of the carrier bandwidth. This type of full-duplex communication may be referred to herein as sub-band full duplex (SBFD), also known as flexible duplex.

[0069] Further, the air interface in the radio access network 200 may utilize one or more multiplexing and multiple access algorithms to enable simultaneous communication of the various devices. For example, 5G NR specifications provide multiple access for UL transmissions from UEs 222 and 224 to base station 210, and for multiplexing for DL transmissions from base station 210 to one or more UEs 222 and 224, utilizing orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP). In addition, for UL transmissions, 5G NR specifications provide support for discrete Fourier transform- spread-OFDM (DFT-s-OFDM) with a CP (also referred to as single-carrier FDMA (SC- FDMA)). However, within the scope of the present disclosure, multiplexing and multiple access are not limited to the above schemes, and may be provided utilizing time division multiple access (TDMA), code division multiple access (CDMA), frequency division multiple access (FDMA), sparse code multiple access (SCMA), resource spread multiple access (RSMA), or other suitable multiple access schemes. Further, multiplexing DL transmissions from the base station 210 to UEs 222 and 224 may be provided utilizing time division multiplexing (TDM), code division multiplexing (CDM), frequency division multiplexing (FDM), orthogonal frequency division multiplexing (OFDM), sparse code multiplexing (SCM), or other suitable multiplexing schemes.

[0070] In some aspects of the disclosure, the scheduling entity and/or scheduled entity may be configured for beamforming and/or multiple-input multiple-output (MIMO) technology. FIG. 3 illustrates an example of a wireless communication system 300 supporting MIMO. In a MIMO system, a transmitter 302 includes multiple transmit antennas 304 (e.g., N transmit antennas) and a receiver 306 includes multiple receive antennas 308 (e.g., M receive antennas). Thus, there are N ^c M signal paths 310 from the transmit antennas 304 to the receive antennas 308. Each of the transmitter 302 and the receiver 306 may be implemented, for example, within a scheduling entity 108, a scheduled entity 106, or any other suitable wireless communication device.

[0071] The use of such multiple antenna technology enables the wireless communication system to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing may be used to transmit different streams of data, also referred to as layers, simultaneously on the same time-frequency resource. The data streams may be transmitted to a single UE to increase the data rate or to multiple UEs to increase the overall system capacity, the latter being referred to as multi-user MIMO (MU-MIMO). This is achieved by spatially precoding each data stream (i.e., multiplying the data streams with different weighting and phase shifting) and then transmitting each spatially precoded stream through multiple transmit antennas on the downlink. The spatially precoded data streams arrive at the UE(s) with different spatial signatures, which enables each of the UE(s) to recover the one or more data streams destined for that UE. On the uplink, each UE transmits a spatially precoded data stream, which enables the base station to identify the source of each spatially precoded data stream.

[0072] The number of data streams or layers corresponds to the rank of the transmission.

In general, the rank of the MIMO system 300 is limited by the number of transmit or receive antennas 304 or 308, whichever is lower. In addition, the channel conditions at the UE, as well as other considerations, such as the available resources at the base station, may also affect the transmission rank. For example, the rank (and therefore, the number of data streams) assigned to a particular UE on the downlink may be determined based on the rank indicator (RI) transmitted from the UE to the base station. The RI may be determined based on the antenna configuration (e.g., the number of transmit and receive antennas) and a measured signal-to-interference-and-noise ratio (SINR) on each of the receive antennas. The RI may indicate, for example, the number of layers that may be supported under the current channel conditions. The base station may use the RI, along with resource information (e.g., the available resources and amount of data to be scheduled for the UE), to assign a transmission rank to the UE.

[0073] In Time Division Duplex (TDD) systems, the UL and DL are reciprocal, in that each uses different time slots of the same frequency bandwidth. Therefore, in TDD systems, the base station may assign the rank for DL MIMO transmissions based on UL SINR measurements (e.g., based on a Sounding Reference Signal (SRS) transmitted from the UE or other pilot signal). Based on the assigned rank, the base station may then transmit the CSI-RS with separate C-RS sequences for each layer to provide for multi layer channel estimation. From the CSI-RS, the UE may measure the channel quality across layers and resource blocks and feed back the CQI and RI values to the base station for use in updating the rank and assigning REs for future downlink transmissions.

[0074] In one example, as shown in FIG. 3, a rank-2 spatial multiplexing transmission on a 2x2 MIMO antenna configuration will transmit one data stream from each transmit antenna 304. Each data stream reaches each receive antenna 308 along a different signal path 310. The receiver 306 may then reconstruct the data streams using the received signals from each receive antenna 308.

[0075] Beamforming is a signal processing technique that may be used at the transmitter 302 or receiver 306 to shape or steer an antenna beam (e.g., a transmit beam or receive beam) along a spatial path between the transmitter 302 and the receiver 306. Beamforming may be achieved by combining the signals communicated via antennas 304 or 308 (e.g., antenna elements of an antenna array module) such that some of the signals experience constructive interference while others experience destructive interference. To create the desired constructive/destructive interference, the transmitter 302 or receiver 306 may apply amplitude and/or phase offsets to signals transmitted or received from each of the antennas 304 or 308 associated with the transmitter 302 or receiver 306.

[0076] In 5G New Radio (NR) systems, particularly for FR2 (millimeter wave) systems, beamformed signals may be utilized for most downlink channels, including the physical downlink control channel (PDCCH) and physical downlink shared channel (PDSCH). In addition, broadcast control information, such as the synchronization signal block (SSB), slot format indicator (SFI), and paging information, may be transmitted in a beam sweeping manner to enable all scheduled entities (UEs) in the coverage area of a transmission and reception point (TRP) (e.g., a gNB) to receive the broadcast control information. In addition, for UEs configured with beamforming antenna arrays, beamformed signals may also be utilized for uplink channels, including the physical uplink control channel (PUCCH) and physical uplink shared channel (PUSCH). However, it should be understood that beamformed signals may also be utilized by enhanced mobile broadband (eMBB) gNBs for sub 6 GHz systems. In addition, beamformed signals may further be utilized in D2D systems, such as NR sidelink (SL) or V2X, utilizing FR2.

[0077] Various aspects of the present disclosure utilize an OFDM waveform, an example of which is schematically illustrated in FIG. 4. It should be understood by those of ordinary skill in the art that the various aspects of the present disclosure may be applied to a DFT-s-OFDMA waveform in substantially the same way as described herein below. That is, while some examples of the present disclosure may focus on an OFDM link for clarity, it should be understood that the same principles may be applied as well to DFT- s-OFDMA waveforms.

[0078] In some examples, a frame refers to a duration of 10 ms for wireless transmissions, with each frame consisting of 10 subframes of 1 ms each. Referring now to FIG. 4, an expanded view of an exemplary DL subframe 402 is illustrated, showing an OFDM resource grid 404. However, as those skilled in the art will readily appreciate, the PHY transmission structure for any particular application may vary from the example described here, depending on any number of factors. Here, time is in the horizontal direction with units of OFDM symbols; and frequency is in the vertical direction with units of subcarriers or tones.

[0079] The resource grid 404 may be used to schematically represent time-frequency resources for a given antenna port. That is, in a MIMO implementation with multiple antenna ports available, a corresponding multiple number of resource grids 404 may be available for communication. The resource grid 404 is divided into multiple resource elements (REs) 406. An RE, which is 1 subcarrier ^c 1 symbol, is the smallest discrete part of the time-frequency grid, and contains a single complex value representing data from a physical channel or signal. Depending on the modulation utilized in a particular implementation, each RE may represent one or more bits of information. In some examples, a block of REs may be referred to as a physical resource block (PRB) or more simply a resource block (RB) 408, which contains any suitable number of consecutive subcarriers in the frequency domain. In one example, an RB may include 12 subcarriers, a number independent of the numerology used. In some examples, depending on the numerology, an RB may include any suitable number of consecutive OFDM symbols in the time domain. Within the present disclosure, it is assumed that a single RB such as the RB 408 entirely corresponds to a single direction of communication (either transmission or reception for a given device).

[0080] Scheduling of scheduled entities (e.g., UEs) for downlink, uplink, or sidelink transmissions typically involves scheduling one or more resource elements 406 within one or more sub-bands or bandwidth parts (BWPs). Thus, a UE generally utilizes only a subset of the resource grid 404. In some examples, an RB may be the smallest unit of resources that can be allocated to a UE. Thus, the more RBs scheduled for a UE, and the higher the modulation scheme chosen for the air interface, the higher the data rate for the UE. The RBs may be scheduled by a base station (e.g., gNB, eNB, etc.) or may be self- scheduled by a UE implementing D2D sidelink communication.

[0081] In this illustration, the RB 408 is shown as occupying less than the entire bandwidth of the subframe 402, with some subcarriers illustrated above and below the RB 408. In a given implementation, the subframe 402 may have a bandwidth corresponding to any number of one or more RBs 408. Further, in this illustration, the RB 408 is shown as occupying less than the entire duration of the subframe 402, although this is merely one possible example.

[0082] Each subframe 402 (e.g., a 1ms subframe) may consist of one or multiple adjacent slots. In the example shown in FIG. 4, one subframe 402 includes four slots 410, as an illustrative example. In some examples, a slot may be defined according to a specified number of OFDM symbols with a given cyclic prefix (CP) length. For example, a slot may include 7 or 14 OFDM symbols with a nominal CP. Additional examples may include mini-slots, sometimes referred to as shortened transmission time intervals (TTIs), having a shorter duration (e.g., one to three OFDM symbols). These mini-slots or shortened TTIs may in some cases be transmitted occupying resources scheduled for ongoing slot transmissions for the same or for different UEs. Any number of resource blocks may be utilized within a subframe or slot.

[0083] An expanded view of one of the slots 410 illustrates the slot 410 including a control region 412 and a data region 414. In general, the control region 412 may carry control channels (e.g., PDCCH), and the data region 414 may carry data channels (e.g., PDSCH or PUSCH). Of course, a slot may contain all DL, all UL, or at least one DL portion and at least one UL portion. The structure illustrated in FIG. 4 is merely exemplary in nature, and different slot structures may be utilized, and may include one or more of each of the control region(s) and data region(s).

[0084] Although not illustrated in FIG. 4, the various REs 406 within an RB 408 may be scheduled to carry one or more physical channels, including control channels, shared channels, data channels, etc. Other REs 406 within the RB 408 may also carry pilots or reference signals. These pilots or reference signals may provide for a receiving device to perform channel estimation of the corresponding channel, which may enable coherent demodulation/detection of the control and/or data channels within the RB 408.

[0085] In some examples, the slot 410 may be utilized for broadcast, multicast, groupcast, or unicast communication. For example, a broadcast, multicast, or groupcast communication may refer to a point-to-multipoint transmission by one device (e.g., a base station, UE, or other similar device) to other devices. Here, a broadcast communication is delivered to all devices, whereas a multicast communication is delivered to multiple intended recipient devices and a groupcast communication is delivered to a group of intended recipient devices. A unicast communication may refer to a point-to-point transmission by a one device to a single other device.

[0086] In an example of cellular communication over a cellular carrier via a Uu interface, for a DL transmission, the scheduling entity (e.g., a base station) may allocate one or more REs 406 (e.g., within the control region 412) to carry DL control information including one or more DL control channels, such as a physical downlink control channel (PDCCH), to one or more scheduled entities (e.g., UEs). The PDCCH carries downlink control information (DCI) including but not limited to power control commands (e.g., one or more open loop power control parameters and/or one or more closed loop power control parameters), scheduling information, a grant, and/or an assignment of REs for DL and UL transmissions. The PDCCH may further carry HAR.Q feedback transmissions such as an acknowledgment (ACK) or negative acknowledgment (NACK). HAR.Q is a technique well-known to those of ordinary skill in the art, wherein the integrity of packet transmissions may be checked at the receiving side for accuracy, e.g., utilizing any suitable integrity checking mechanism, such as a checksum or a cyclic redundancy check (CRC). If the integrity of the transmission confirmed, an ACK may be transmitted, whereas if not confirmed, a NACK may be transmitted. In response to a NACK, the transmitting device may send a HARQ retransmission, which may implement chase combining, incremental redundancy, etc.

[0087] The base station may further allocate one or more REs 406 (e.g., in the control region 412 or the data region 414) to carry other DL signals, such as a demodulation reference signal (DMRS); a phase-tracking reference signal (PT-RS); a channel state information (CSI) reference signal (CSI-RS); and a synchronization signal block (SSB). SSBs may be broadcast at regular intervals based on a periodicity (e.g., 5, 10, 20, 40, 80, or 160 ms). An SSB includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a physical broadcast control channel (PBCH). A UE may utilize the PSS and SSS to achieve radio frame, subframe, slot, and symbol synchronization in the time domain, identify the center of the channel (system) bandwidth in the frequency domain, and identify the physical cell identity (PCI) of the cell.

[0088] The PBCH in the SSB may further include a master information block (MIB) that includes various system information, along with parameters for decoding a system information block (SIB). The SIB may be, for example, a SystemlnformationType 1 (SIB1) that may include various additional system information. Examples of system information transmitted in the MIB may include, but are not limited to, a subcarrier spacing, system frame number, a configuration of a PDCCH control resource set (CORESET) (e.g., PDCCH CORESETO), and a search space for SIBl. Examples of additional system information transmitted in the SIBl may include, but are not limited to, a random access search space, downlink configuration information, and uplink configuration information. The MIB and SIBl together provide the minimum system information (SI) for initial access. A CORESET may include one or more control resource (e.g., time and frequency resources) sets, configured for conveying a 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.

[0089] In an UL transmission, the scheduled entity (e.g., UE) may utilize one or more

REs 406 to carry UL control information (UCI) including one or more UL control channels, such as a physical uplink control channel (PUCCH), to the scheduling entity. UCI may include a variety of packet types and categories, including pilots, reference signals, and information configured to enable or assist in decoding uplink data transmissions. In some examples, the UCI may include a scheduling request (SR), i.e., request for the scheduling entity to schedule uplink transmissions. Here, in response to the SR transmitted on the UCI, the scheduling entity may transmit downlink control information (DCI) that may schedule resources for uplink packet transmissions. UCI may also include HARQ feedback, channel state feedback (CSF), such as a CSI report, or any other suitable UCI.

[0090] In addition to control information, one or more REs 406 (e.g., within the data region 414) may be allocated for data traffic. Such data traffic may be carried on one or more traffic channels, such as, for a DL transmission, a physical downlink shared channel (PDSCH); or for an UL transmission, a physical uplink shared channel (PUSCH). In some examples, one or more REs 406 within the data region 414 may be configured to carry other signals, such as one or more SIBs and DMRSs.

[0091] In an example of sidelink communication over a sidelink carrier via a PC5 interface, the control region 412 of the slot 410 may include a physical sidelink control channel (PSCCH) including sidelink control information (SCI) transmitted by an initiating (transmitting) sidelink device (e.g., V2X or other sidelink device) towards a set of one or more other receiving sidelink devices. The data region 414 of the slot 410 may include a physical sidelink shared channel (PSSCH) including sidelink data traffic transmitted by the initiating (transmitting) sidelink device within resources reserved over the sidelink carrier by the transmitting sidelink device via the SCI. Other information may further be transmitted over various REs 406 within slot 410. For example, HARQ feedback information may be transmitted in a physical sidelink feedback channel (PSFCH) within the slot 410 from the receiving sidelink device to the transmitting sidelink device. In addition, one or more reference signals, such as a sidelink SSB and/or a sidelink CSI-RS, may be transmitted within the slot 410.

[0092] The channels or carriers described above and illustrated in FIGs. 1 and 4 are not necessarily all the channels or carriers that may be utilized between a scheduling entity 108 and scheduled entities 106, 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 traffic, control, and feedback channels.

[0093] These physical channels described above are generally multiplexed and mapped to transport channels for handling at the medium access control (MAC) layer. Transport channels carry blocks of information called transport blocks (TB). The transport block size (TBS), which may correspond to a number of bits of information, may be a controlled parameter, based on the modulation and coding scheme (MCS) and the number of RBs in a given transmission. [0094] In some examples, spatial division multiplexing may be implemented using a coordinated multi-point (CoMP) network configuration in which transmissions (streams) from multiple transmission and reception points (TRPs) may be simultaneously directed towards a single UE. In a multi-TRP environment providing multi-stream transmission, the multiple TRPs may or may not be collocated (e.g., at the same geographical location and coupled to the same antenna tower or pole). Each of the multiple TRPs may transmit the same or different data to a UE. When transmitting different data from the multiple TRPs, a higher throughput may be achieved. When transmitting the same data (with potentially different redundancy versions) from the multiple TRPs, transmission reliability may be improved. In some examples, each TRP may utilize the same carrier frequency to communicate with a UE. In other examples, each TRP may utilize a different carrier frequency that may be in the same or different frequency bands (e.g., FR2, FR4-a or FR4-1, FR4, FR5, etc.). For example, each TRP may communicate on different carrier frequencies (referred to as component carriers) in the same frequency band or across frequency bands and carrier aggregation may be performed at the UE.

[0095] FIG. 5 is a conceptual diagram illustrating an example of a multi-TRP environment 500 according to some aspects. The multi-TRP environment 500 includes a plurality of cells 502 and 506a-506d. In some examples, one of the cells 502 may be considered a primary serving cell (PCell) 502 and the remaining cells 506a, 506b, 506c, and 506d may be considered secondary serving cells (SCells). The PCell 502 may be referred to as the anchor cell that provides a radio resource control (RRC) connection to the UE. In some examples, the PCell and the SCell may be collocated (e.g., different TRPs at the same geographical location and coupled to the same antenna tower/pole).

[0096] When carrier aggregation (CA) is configured, one or more of the SCells 506a- 506d may be activated or added to the PCell 502 to form the serving cells serving a user equipment (UE) 510. Each serving cell corresponds to a component carrier (CC). The CC of the PCell 502 may be referred to as a primary CC, and the CC of a SCell 506a-506d may be referred to as a secondary CC. The PCell 502 and one or more of the SCells 506 may be served by a respective TRP 504 and 508a-508c similar to any of those illustrated in FIGs. 1 and 2. In the example shown in FIG. 5, SCells 506a-506c are each served by a respective non-collocated TRP 508a-508c. However, SCell 506d is collocated with the PCell 502. Thus, TRP 504 may include two collocated TRPs, each supporting a different carrier. For example, TRP 504 may correspond to a base station including multiple collocated TRPs. The coverage of the PCell 502 and SCell 506d may differ since different component carriers (which may be in different frequency bands) may experience different path loss.

[0097] In some examples, the PCell 502 may add or remove one or more of the SCells

506a-506d to improve reliability of the connection to the UE 510 and/or increase the data rate. The PCell 502 may be changed upon a handover to another PCell.

[0098] In some examples, one of the cells (e.g., cell 502) may be a low band cell, and another cell (e.g., cell 506d) may be a high band cell. A low band cell uses a carrier frequency in a frequency band lower than that of the high band cells. For example, the high band cell may use a high band mmWave carrier (e.g., FR4-a or FR4-1 or above), and the low band cell may use a low band mmWave carrier (e.g., FR2). In this example, carrier aggregation may not be performed between the cells 502 and 506d, depending on whether carrier aggregation across frequency bands is supported. In addition, when using mmWave carriers (FR2 or above), beamforming may be used to transmit and receive signals.

[0099] FIG. 6 is a diagram illustrating communication between a base station 604 and a UE 602 using beamformed signals according to some aspects. The base station 604 may be any of the base stations (e.g., gNBs) or scheduling entities illustrated in FIGs. 1 and/or 2, and the UE 602 may be any of the UEs or scheduled entities illustrated in FIGs. 1, 2, and/or 5.

[0100] The base station 604 may generally be capable of communicating with the UE 602 using one or more transmit beams, and the UE 602 may further be capable of communicating with the base station 604 using one or more receive beams. As used herein, the term transmit beam refers to a beam on the base station 604 that may be utilized for downlink or uplink communication with the UE 602. In addition, the term receive beam refers to a beam on the UE 602 that may be utilized for downlink or uplink communication with the base station 604.

[0101] In the example shown in FIG. 6, the base station 604 is configured to generate a plurality of transmit beams 606a-606h. Each transmit beam may be associated with one or more different spatial directions (e.g., in some scenarios, the directions may be the same, generally the same, or different). In addition, the UE 602 is configured to generate a plurality of receive beams 608a-608e, each associated with a different spatial direction. It should be noted that while some beams are illustrated as adjacent to one another, such an arrangement may be different in different aspects. For example, transmit beams 606a- 606h transmitted during a same symbol may not be adjacent to one another. In some examples, the base station 604 and UE 602 may each transmit more or less beams distributed in all directions (e.g., 360 degrees) and in three-dimensions. In addition, the transmit beams 606a-606h may include beams of varying beam width. For example, the base station 604 may transmit certain signals (e.g., SSBs) on wider beams and other signals (e.g., CSI-RSs) on narrower beams.

[0102] The base station 604 and UE 602 may select one or more transmit beams 606a-

606h on the base station 604 and one or more receive beams 608a-608e on the UE 602 for communication of uplink and downlink signals therebetween using a beam management procedure. In one example, during initial cell acquisition, the UE 602 may perform a PI beam management procedure to scan the plurality of transmit beams 606a- 606h on the plurality of receive beams 608a-608e to select a beam pair link (e.g., one of the transmit beams 606a-606h and one of the receive beams 608a-608e) for a physical random access channel (PRACH) procedure for initial access to the cell. For example, periodic SSB beam sweeping may be implemented on the base station 604 at certain intervals (e.g., based on the SSB periodicity). Thus, the base station 604 may be configured to sweep or transmit an SSB on each of a plurality of wider transmit beams 606a-606h during the beam sweeping interval. The UE may measure the reference signal received power (RSRP) of each of the SSB transmit beams on each of the receive beams of the UE and select the transmit and receive beams based on the measured RSRP. In an example, the selected receive beam may be the receive beam on which the highest RSRP is measured and the selected transmit beam may have the highest RSRP as measured on the selected receive beam.

[0103] After completing the PRACH procedure, the base station 604 and UE 602 may perform a P2 beam management procedure for beam refinement at the base station 604. For example, the base station 604 may be configured to sweep or transmit a CSI-RS on each of a plurality of narrower transmit beams 606a-606h. Each of the narrower CSI-RS beams may be a sub-beam of the selected SSB transmit beam (e.g., within the spatial direction of the SSB transmit beam). Transmission of the CSI-RS transmit beams may occur periodically (e.g., as configured via radio resource control (RRC) signaling by the gNB), semi-persistently (e.g., as configured via RRC signaling and activated/deactivated via medium access control-control element (MAC-CE) signaling by the gNB), or aperiodically (e.g., as triggered by the gNB via downlink control information (DCI)). The UE 602 is configured to scan the plurality of CSI-RS transmit beams 606a-606h on the plurality of receive beams 608a-608e. The UE 602 then performs beam measurements (e.g., RSRP, SINR, etc.) of the received CSI-RSs on each of the receive beams 608a- 608e to determine the respective beam quality of each of the CSI-RS transmit beams 606a-606h as measured on each of the receive beams 608a-608e.

[0104] The UE 602 can then generate and transmit a Layer 1 (LI) measurement report, including the respective beam index (e.g., CSI-RS resource indicator (CRI)) and beam measurement (e.g., RSRP or SINR) of one or more of the CSI-RS transmit beams 606a- 606h on one or more of the receive beams 608a-608e to the base station 604. The base station 604 may then select one or more CSI-RS transmit beams on which to communicate downlink and/or uplink control and/or data with the UE 602. In some examples, the selected CSI-RS transmit beam(s) have the highest RSRP from the LI measurement report. Transmission of the LI measurement report may occur periodically (e.g., as configured via RRC signaling by the gNB), semi-persistently (e.g., as configured via RRC signaling and activated/deactivated via MAC-CE signaling by the gNB), or aperiodically (e.g., as triggered by the gNB via DCI).

[0105] The UE 602 may further select a corresponding receive beam on the UE 602 for each selected serving CSI-RS transmit beam to form a respective beam pair link (BPL) for each selected serving CSI-RS transmit beam. For example, the UE 602 can utilize the beam measurements obtained during the P2 procedure or perform a P3 beam management procedure to obtain new beam measurements for the selected CSI-RS transmit beams to select the corresponding receive beam for each selected transmit beam. In some examples, the selected receive beam to pair with a particular CSI-RS transmit beam may be the receive beam on which the highest RSRP for the particular CSI-RS transmit beam is measured.

[0106] In some examples, in addition to performing CSI-RS beam measurements, the base station 604 may configure the UE 602 to perform SSB beam measurements and provide an LI measurement report containing beam measurements of SSB transmit beams 606a-606h. For example, the base station 604 may configure the UE 602 to perform SSB beam measurements and/or CSI-RS beam measurements for beam failure detection (BFD), beam failure recovery (BFR), cell reselection, beam tracking (e.g., for a mobile UE 602 and/or base station 604), or other beam optimization purpose.

[0107] In addition, when the channel is reciprocal, the transmit and receive beams may be selected using an uplink beam management scheme. In an example, the UE 602 may be configured to sweep or transmit on each of a plurality of receive beams 608a-608e. For example, the UE 602 may transmit an SRS on each beam in the different beam directions. In addition, the base station 604 may be configured to receive the uplink beam reference signals on a plurality of transmit beams 606a-606h. The base station 604 then performs beam measurements (e.g., RSRP, SINR, etc.) of the beam reference signals on each of the transmit beams 606a-606h to determine the respective beam quality of each of the receive beams 608a-608e as measured on each of the transmit beams 606a-606h.

[0108] The base station 604 may then select one or more transmit beams on which to communicate downlink and/or uplink control and/or data with the UE 602. In some examples, the selected transmit beam(s) have the highest RSRP. The UE 602 may then select a corresponding receive beam for each selected serving transmit beam to form a respective beam pair link (BPL) for each selected serving transmit beam, using, for example, a P3 beam management procedure, as described above.

[0109] In one example, a single CSI-RS transmit beam (e.g., beam 606d) on the base station 604 and a single receive beam (e.g., beam 608c) on the UE may form a single BPL used for communication between the base station 604 and the UE 602. In another example, multiple CSI-RS transmit beams (e.g., beams 606c, 606d, and 606e) on the base station 604 and a single receive beam (e.g., beam 608c) on the UE 602 may form respective BPLs used for communication between the base station 604 and the UE 602. In another example, multiple CSI-RS transmit beams (e.g., beams 606c, 606d, and 606e) on the base station 604 and multiple receive beams (e.g., beams 608c and 608d) on the UE 602 may form multiple BPLs used for communication between the base station 604 and the UE 602. In this example, a first BPL may include transmit beam 606c and receive beam 608c, a second BPL may include transmit beam 608d and receive beam 608c, and a third BPL may include transmit beam 608e and receive beam 608d.

[0110] Concerning multi -beam operation of the apparatus in FIG. 6, for example, enhancements in 5G NR for multi-beam operation have targeted FR2 frequency bands, but may also be applicable to the other frequency bands. These enhancements have been provided to facilitate more efficient (i.e., lower latency and overhead) DL/UL beam management to support higher intra-cell and Ll/L2-centric inter-cell mobility and a larger number of configured transmission configuration indicator (TCI) states. These enhancements may be effected by providing a common beam for data and control transmission/reception for DL and UL, especially for intra-band carrier aggregation (CA). Also, enhancements may be engendered with a unified TCI framework for DL and UL beam indication. Further, enhancements concerning signaling mechanisms for these features can improve latency and efficiency through greater usage of dynamic control signaling as opposed to RRC signaling. Also, enhancements for multi-beam operation may be based on identifying and specifying features to facilitate UL beam selection for UEs equipped with multiple panels, taking into consideration UL coverage loss mitigation due to maximum permissible exposure (MPE) limitations, and based on UL beam indication with the unified TCI framework for UL fast panel selection.

[0111] Other enhancements may be for supporting multi-TRP deployment, including targeting both FR1 and FR2 frequency bands. In particular, enhancement may focus on identifying and specifying features to improve reliability and robustness for channels other than PDSCH (i.e., PDCCH, PUSCH, and PUCCH) using multi-TRP or multi-panel with 3 GPP Release 16 reliability features as the baseline. Additionally, enhancements may concern identifying and specifying quasi co-location (QCL)/TCI-related enhancements to enable inter-cell multi-TRP operations, assuming multi-DCI based multi-PDSCH reception. Further, beam-management-related enhancements for simultaneous multi-TRP transmission with multi-panel reception may be provided. Still further concerning multi-TRP deployments, enhancements to support high speed train- single frequency network (HST-SFN) deployment scenarios may be provided, such as identifying and specifying solution(s) on QCL assumptions for DMRS (e.g., multiple QCL assumptions for the same DMRS port(s), targeting DL-only transmissions, or specifying QCL/QCL-like relations (including applicable type(s) and the associated requirement) between DL and UL signals by reusing the unified TCI framework.

[0112] It is further noted that according to certain aspects, the methodology disclosed herein may be implemented at the layer 1 (LI) (e.g., PHY layer) and layer 2 (L2) (e.g., MAC layer) levels of a radio access network.

[0113] The radio protocol architecture for a radio access network, such as the radio access network 104 shown in FIG. 1 and/or the radio access network 200 shown in FIG. 2, may take on various forms depending on the particular application. An example of a radio protocol architecture for the user and control planes is illustrated FIG. 7.

[0114] As illustrated in FIG. 7, the radio protocol architecture for the UE and the base station includes three layers: layer 1 (LI), layer 2 (L2), and layer 3 (L3). LI is the lowest layer and implements various physical layer signal processing functions, including the remote radio head (RRH) in the case of gNBs. LI will be referred to herein as the physical (PHY) layer 706. L2 708 is above the physical layer 706 and is responsible for the link between the UE and base station over the physical layer 706. [0115] In the user plane, the L2 layer 708 includes a medium access control (MAC) layer

710, a radio link control (RLC) layer 712, a packet data convergence protocol (PDCP) 714 layer, and a service data adaptation protocol (SDAP) layer 716, which are terminated at the base station on the network side. Although not shown, the UE may have several upper layers above the L2 layer 708 including at least one network layer (e.g., IP layer and user data protocol (UDP) layer) that is terminated at the User Plane Function (UPF) on the network side and one or more application layers.

[0116] The SDAP layer 716 provides a mapping between a 5G core (5GC) quality of service (QoS) flow and a data radio bearer and performs QoS flow ID marking in both downlink and uplink packets. The PDCP layer 714 provides packet sequence numbering, in-order delivery of packets, retransmission of PDCP protocol data units (PDUs), and transfer of upper layer data packets to lower layers. PDU’s may include, for example, Internet Protocol (IP) packets, Ethernet frames and other unstructured data (i.e., Machine- Type Communication (MTC), hereinafter collectively referred to as “packets”). The PDCP layer 714 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and integrity protection of data packets. A PDCP context may indicate whether PDCP duplication is utilized for a unicast connection.

[0117] The RLC layer 712 provides segmentation and reassembly of upper layer data packets, error correction through automatic repeat request (ARQ), and sequence numbering independent of the PDCP sequence numbering. An RLC context may indicate whether an acknowledged mode (e.g., a reordering timer is used) or an unacknowledged mode is used for the RLC layer 712. The MAC layer 710 provides multiplexing between logical and transport channels. The MAC layer 710 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs and for FLAR.Q operations. A MAC context may enable, for example, a FLAR.Q feedback scheme, resource selection algorithms, carrier aggregation, beam failure recovery, or other MAC parameters for a unicast connection. The physical layer 706 is responsible for transmitting and receiving data on physical channels (e.g., within slots). A PHY context may indicate a transmission format and a radio resource configuration (e.g., bandwidth part (BWP), numerology, etc.) for a unicast connection.

[0118] In the control plane, the radio protocol architecture for the UE and base station is substantially the same for LI 706 and L2 708 with the exception that there is no SDAP layer in the control plane and there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC) layer 718 in L3 and a higher Non Access Stratum (NAS) layer 720. The RRC layer 718 is responsible for establishing and configuring signaling radio bearers (SRBs) and data radio bearers (DRBs) between the base station the UE, paging initiated by the 5GC or NG-RAN, and broadcast of system information related to Access Stratum (AS) and Non Access Stratum (NAS). The RRC layer 718 is further responsible for QoS management, mobility management (e.g., handover, cell selection, inter-RAT mobility), UE measurement and reporting, and security functions. The NAS layer 720 is terminated at the AMF in the core network and performs various functions, such as authentication, registration management, and connection management.

[0119] As mentioned above, certain enhancements in 5G NR for multi -beam or multi -

TRP operations may include Ll/L2-centric inter-cell mobility, which may be a MIMO enhancement feature. Thus, the control for effecting UE mobility between cells (e.g., handoffs) is accomplished through controls and/or signaling in the LI and/or L2 layers rather than at higher layers above the L2 layer; hence being L1/L2 “centric.” Using Ll/L2-centric inter-cell mobility can result in lower latency and overhead than using higher layer (e.g., RRC or L3) based mobility control signaling. According to aspects herein, operational modes or characteristics of this Ll/L2-centric inter-cell mobility are disclosed. Broadly, aspects of the present disclosure provide methods and apparatus for the operation of inter-cell mobility where at least one serving cell in a communication system are configured with one or more physical layer cell IDs (PCIs) according to a particular selected mode of operation through the use of either signaling or settings for the physical (PHY) layer or the medium access control (MAC) layer. Further, based on the mode of operation, a radio resource head (RRH) can serve at least one user equipment (UE) based on power information received from at least one UE (e.g., reference signal receive power (RSRP) information).

[0120] In one particular operational aspect (first operating mode), each serving cell (e.g., cells 202, 204, and 206 in FIG. 2) may be configured to have one physical layer cell identifier (PCI), but can have multiple physical cell sites, such as having multiple remote radio heads (RRHs) or remote radio units (RRUs). Each RRH may transmit a different set of SSB (synchronization signal/PBCH block) IDs or indexes but with the same, single PCI for the serving cell. According to some aspects, the selection may be accomplished through Layer 1 (LI) signaling using downlink control indicators (DCIs) in the LI PHY layer or media access control - control element (MAC-CE) signaling in the L2 MAC layer, wherein a MAC-CE is generally defined as a MAC structure used for carrying MAC layer control information between a gNB and a UE, and wherein the structure of a MAC-CE may be implemented as a special bit string in a logical channel ID (LCID) field of a MAC Header. In particular, DCI/MAC-CE is used to effect selection of which RRH(s) or corresponding SSBs will serve a UE based on the LI metrics (e.g., RSRP) per each reported SSB ID.

[0121] In another aspect (second operating mode), rather than only one PCI, each serving cell can be configured with multiple PCIs. Here, each RRH of the serving cell can use one PCI configured for the corresponding serving cell and may transmit a full set of SSB IDs. Selection of which RRH(s) or corresponding PCI(s) and/or SSB(s) serve the UE may be accomplished by DCI/MAC-CE signaling and also based on the LI metrics (e.g., an RSRP) per reported SSB ID per reported PCI.

[0122] In still another aspect (third operating mode), each serving cell may have one PCI, but the DCI/MAC-CE can select which serving cell(s) or corresponding serving cell ID(s) will serve the UE based on the LI based metrics (e.g., RSRP) per reported SSB ID per reported PCI.

[0123] It should be appreciated that the different operational options noted above are not necessarily limited to SSB IDs, but rather may be applied generally to any cell-defining reference signals (RS), such as CSI-RS or positioning reference signals (PRS), as examples.

Initial Beam Determination of Selected Cell in L1/L2 Inter-Cell Mobility

[0124] Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for selecting an initial beam to use in communicating with a new cell indicated via inter-cell mobility signaling via Ll/PHY or L2/MAC layer signaling.

[0125] The techniques presented herein may be applied in various bands utilized for NR.

For example, for the higher band such as FR2 and FR4 bands. 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., LI and/or L2-centric mobility) and/or a larger number of transmission configuration indicator (TCI) states. For example, the states may include the use of a common beam for data and control transmission and reception for UL and DL operations, a unified TCI framework for UL and DL beam indication, and enhanced signaling mechanisms to improve latency and efficiency (e.g., dynamic usage of control signaling).

[0126] 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 LI -event-driven beam management may also reduce latency and the probability that beam failure events occur.

[0127] Additional enhancements 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 enhancements may, in some cases, be related to quasi co- location (QCL) 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.

[0128] Still further enhancements 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.

[0129] In LlL2-based inter-cell mobility, a UE may switch to a new cell and may begin communicating with the new cell without receiving a TCI activation command. Generally, when the UE does not receive a TCI activation command, a UE may not be instructed to use a specific beam (or set of beams) for communications with the base station.

[0130] FIG. 8 illustrates example operations 800 that may be performed by a UE to identify an initial beam to use in communicating with a selected cell in LlL2-based mobility, in accordance with certain aspects of the present disclosure. Operations 800 may be performed, for example, by a UE or scheduled entity 106 illustrated in FIG. 1.

[0131] As illustrated, operations 800 begin, at 802, where the UE receives a command to switch from a current cell to a new cell. The command may be signaled via physical layer (LI) or medium access control (MAC) layer (L2) signaling. At 804, the UE determines an initial beam to use for at least one of uplink or downlink transmissions in the new cell before the UE receives a transmission configuration indicator (TCI) activation or configuration command. At 806, the UE communicates in the new cell using the initial beam.

[0132] FIG. 9 illustrates example operations 900 that may be performed by a network identity to identify an initial beam to use in communications with a UE in Ll/L2-based mobility, in accordance with certain aspects of the present disclosure. Operations 900 may be performed, for example, by a base station or scheduling entity 108 illustrated in FIG. 1 and may be complementary to operations 800 illustrated in FIG. 8.

[0133] As illustrated, operations 900 begin, at 902, where the network entity transmits, to a user equipment (UE), a command to switch from a current cell to a new cell. The command may be signaled via physical layer or medium access control (MAC) layer signaling. At 904, the network entity determines an initial beam for the UE to use for at least one of uplink or downlink transmissions in the new cell prior to the network entity transmitting a transmission configuration indicator (TCI) activation or configuration command. At 906, the network entity communicates with the UE in the new cell using the initial beam.

[0134] In some aspects, the initial beam may be based on a most recent LI metric report or metrics generated before the L1/L2 cell selection command is received.

[0135] In some aspects, the initial beam may be indicated explicitly or implicitly. An explicit indication of an initial beam may be, for example, an RS ID in the L1/L2 cell selection command. An implicit indication of the initial beam may be, for example, the beam associated with the best reported reference signal in the most recent LI metric report generated before the UE received the L1/L2 cell selection command.

[0136] The UE may stop using the initial beam after receiving a TCI activation and/or configuration command. The command may be received for the physical downlink control channel (PDCCH) and/or physical downlink shared channel (PDSCH) on the new cell. In some aspects, TCI activation may be implicitly signaled. An implicit signaling of TCI activation may include, for example, the transmission of certain reference signals or channels on the new cell. For example, transmission of a tracking reference signal (TRS), CSI-RS, or other reference signals for beam management or the PDCCH may implicitly indicate activation of a TCI state.

[0137] FIG. 10 is a call flow diagram illustrating an example of identifying an initial beam to use in communicating with a new cell in L1/L2 based mobility procedures. As illustrated, the UE 1002 receives an L1/L2 cell selection command 1006 from a first base station 1004. The L1/L2 cell selection command generally identifies a new base station 1008 (i.e., base station 2 illustrated in FIG. 10) that the UE is to communicate with.

[0138] At 1010, based on receiving the L1/L2 cell selection command, the UE identifies an initial beam to use for communications with the cell identified in the cell selection command. The initial beam, as discussed, may be determined based on LI metric reports generated prior to receipt of the L1/L2 cell selection command 1006, based on explicit indications in the L1/L2 cell selection command, or implicitly based on the best reported reference signal in the most recent LI metric report generated prior to receipt of the L1/L2 cell selection command. At 1012, the UE may then communicate with the cell indicated in the L1/L2 cell selection command using the initial beam.

[0139] At 1014, at some later point in time, the UE may receive, from the second base station 1008, a TCI activation command including a beam identification. At 1016, the UE may subsequently communicate with the second base station using the beam identified in the TCI activation command.

Default Beam Selection in L1/L2 -Based Mobility

[0140] Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for identifying a default beam to use in communicating between a UE and a base station in L1/L2 inter-cell mobility.

[0141] In Rel-15, the default PDSCH beam may follow the QCL assumption for the

CORESET with the lowest CORESET ID in the active downlink BWP of the current serving cell. In Ll/L2-based mobility, the default PDSCH beam may be selected based on various operating modes. The operating modes may include the second operation mode (an Ll/L2-based PCI switch) or third operation mode (an Ll/L2-based serving cell switch) described above. In the second operation mode, each serving cell may be configured with multiple PCIs. Each RRH of the serving cell can use one PCI configured for the serving cell and transmit the full set of SSB IDs, and L1/L2 signaling (e.g., a downlink control information (DCI) or MAC control element (MAC-CE)) can select which RRH(s) or corresponding PCI(s) and/or SSB(s) to serve the UE based on signal quality (e.g., RSRP) per reported SSB ID per reported PCI. In the third operation mode, each serving cell may be configured with a single PCI. L1/L2 signaling can select the serving cell(s) or corresponding serving cell ID(s) to serve the UE based on signal quality metrics per reported SSB ID per reported PCI. [0142] FIG. 11 illustrates example operations 1100 that may be performed by a UE to identify a default beam to use in communicating with a selected cell in Ll/L2-based mobility, in accordance with certain aspects of the present disclosure. Operations 1100 may be performed, for example, by a UE or scheduled entity 106 illustrated in FIG. 1.

[0143] As illustrated, operations 1100 begin, at 1102, where the UE receives a command, signaled via physical (LI) layer or medium access control (MAC) (L2) layer signaling, that indicates at least one of: at least one cell or at least one physical cell ID (PCI) to serve the UE. At 1104, the UE determines a default beam for a physical downlink shared channel (PDSCH) transmission in the indicated cell or PCI cell. At 1106, the UE communicates in the new cell using the default beam.

[0144] FIG. 12 illustrates example operations 1200 that may be performed by a network entity to identify a default beam to use in communicating with a UE in Ll/L2-based mobility, in accordance with certain aspects of the present disclosure. Operations 1200 may be performed, for example, by a base station or scheduled entity 108 illustrated in FIG. 1 and may be complementary operations to the operations 1100 illustrated in FIG. 11

[0145] As illustrated, operations 1200 begin, at 1202, where the network entity transmits, to a UE, a command, signaled via physical layer (LI) or medium access control (MAC) layer (L2) signaling, that indicates at least one of: at least one cell or at least one physical cell ID (PCI) to serve the UE. At 1204, the network entity determines a default beam for the UE for a physical downlink shared channel (PDSCH) transmission in the indicated cell or PCI cell. At 1206, the network entity communicates with the UE in the new cell using the default beam.

[0146] In the second operation mode, the default PDSCH beam may be determined as follows. In some aspects, if the UE switches across multiple PCIs one at a time, the default PDSCH beam can follow the QCL assumption for the CORESET with the lowest CORESET ID in the active downlink BWP of the currently selected PCI. In some aspects, if the UE switches across multiple PCIs one at a time, the default PDSCH beam can follow the QCL assumption for the CORESET with the lowest CORESET in a default downlink BWP of a default PCI, which may be different from the currently selected PCI. The default PCI may be determined by the gNB or UE based on RRC signaling, a MAC-CE, or DCI.

[0147] In some aspects, when the UE has multiple simultaneously selected PCIs, the default PDSCH beam can follow the QCL assumptions for the CORESET with the lowest CORESET ID in the active downlink BWP of one currently selected PCI. The currently selected PCI may be determined by the gNB or UE based on RRC signaling, a MAC-CE, or DCI, or based on an implicit rule (e.g., the lowest or highest PCI index among selected PCIs).

[0148] In some aspects, where the UE has multiple simultaneously selected PCIs, the default PDSCH beam can follow the QCL assumptions for the CORESET with the lowest CORESET ID in the active downlink BWPs of multiple currently selected PCIs. The multiple PCIs may be determined by the gNB or UE based on RRC signaling, a MAC- CE, or DCI, or based on an implicit rule (e.g., the lowest or highest PCI index among PCIs having the same lowest CORESET ID). If more than one PCI includes the same lowest CORESET ID, the PCI may be determined by the gNB or UE or may be indicated implicitly (e.g., selecting the PCI with the lowest or highest PCI index among those PCIs having the same lowest CORESET ID).

[0149] In some aspects, the default PDSCH beam may follow the QCL assumption for the CORESET with the lowest CORESET ID in a default downlink BWP of a default PCI.

[0150] In some aspects, in the third operation mode, the default PDSCH beam may be determined based on the identity of the serving cell rather than a PCI. For example, the default PDSCH beam may follow QCL assumptions for the CORESET with the lowest CORESET ID in the active downlink BWP of the currently selected serving cell or in a default downlink BWP of a default serving cell (which may be different from the current selected serving cell).

[0151] If no CORESET is configured on the corresponding downlink BWP, the default

PDSCH beam may be indicated by the QCL-TypeD reference signal of one active PDSCH TCI state on the downlink BWP. The active PDSCH TCI state may be, for example, the TCI state with the lowest or highest TCI state ID.

[0152] In some aspects, the CORESET discussed above may be the CORESET associated with the lowest CORESET ID in a latest slot with the monitored search space or CORESET.

[0153] In some aspects, the reference signal (RS) used to determine the default PDSCH beam for each PCI can also be used to determine a default uplink beam (e.g., for transmissions on the physical uplink control channel, transmissions on the physical uplink shared channel, and/or transmissions of sounding reference signals) and to measure pathloss for determining uplink transmission power for the UE to communicate with a base station (e.g., gNB) on the uplink. That is, the reference signal used for determining a default PDSCH beam may be used as a pathloss reference signal. The default uplink beam may be a default PUCCH or SRS beam when uplink beam indication is not configured or indicated by a base station (e.g., the base station does not indicate a spatial relation). The default uplink beam may be a default PUSCH beam when the PUSCH is scheduled by a particular DCI format (e.g., DCI format 0 0) but no PUCCH with a configured spatial relation is present in the active uplink BWP. For example, in Release- 15 and Release-16, the default PUSCH beam when a PUSCH is scheduled by DCI format 0 0 may follow the spatial relation of the PUCCH with a lowest resource ID in the active uplink BWP.

[0154] FIG. 13 is a call flow diagram illustrating the determination and use of a default PDSCH beam in Ll/L2-based mobility. As illustrated, a UE 1302 receives an L1/L2 cell selection command from a first cell 1304 (e.g., cell 1 illustrated in FIG. 13). The L1/L2 cell selection command can identify a new cell 1306 (e.g., cell 2 illustrated in FIG. 13) that the UE is to communicate with. At 1308, based on receiving the L1/L2 cell selection command, the UE identifies a default beam to use for PDSCH transmissions in the cell identified in the cell selection command. At 1310, some later point in time, the UE receives a PDSCH transmission from cell 2 and processes the received PDSCH transmission using the default beam.

Anchor Cell Selection in L1/L2 Inter-Cell Mobility

[0155] FIG. 14 is a flow chart illustrating a process for wireless communication using Ll/L2-centric inter-cell mobility. At block 1402, a UE can connect with one or more cells in a network (e.g., multi-TRP environment 500). It should be further appreciated that, in Ll/L2-centric inter-cell mobility, it may be desirable for a gNB/UE to clarify which cell is designated as the anchor cell for fallback operations when a UE simultaneously connects to or switches across multiple cells. The multiple cells may correspond to multiple RRHs (e.g., TRPs 508a, 508b, and 508c ) associated with different PCIs, which can be configured under the same serving cell identified by an RRC-configured serving cell ID.

[0156] At decision block 1404, the UE determines whether or not a fallback condition exists or is triggered. For example, a fallback condition exists if the UE detects a failed control beam or radio link with one or more cells. At block 1406, if the fallback condition exists, the UE can select an anchor cell or default cell of the network to perform a fallback operation. In a fallback operation, the UE switches to an anchor or default cell in order to maintain or reestablish communication with the network.

[0157] At block 1408, the UE can perform the fallback operation on the selected anchor cell. In one aspect, the fallback operation on the anchor cell may include a contention- free random access (CFRA) or contention-based random access (CBRA) operation. For example, the UE can use the CFRA/CBRA operation for sending a recovery request for a failed control beam (e.g., beam failure recovery (BFR) or radio link (e.g., radio link recovery (RLR)). In one aspect, the fallback operation on the anchor cell may include acquiring information regarding at least one of a broadcast communication or a multicast communication (e.g., reading SIB/paging info on CORESET 0). In one aspect, the fallback operation on the anchor cell may include measuring reference signals to detect the failure of a control beam or to monitor the quality of a radio link (e.g., beam failure detection (BFD) / radio link monitoring (RLM)). In one aspect, the fallback operation on the anchor cell may include transmitting a scheduling request (SR) associated with an uplink (UL) grant (e.g., for either UL traffic or beam/radio link failure requests), wherein the SR resource on the anchor cell can be either PRACH or PUCCH, for example.

[0158] Some aspects disclosed herein are thus directed towards selecting anchor cell(s)

(or PCI(s)) for fallback operations in Ll/L2-centric inter-cell mobility. FIG. 15 is a flow chart illustrating a first exemplary process for selecting an anchor cell for L1/L2 centric inter-cell mobility. At block 1505, a UE switches across multiple cells (or PCIs) (e.g., selected using L1/L2 signaling), but one at a time. For example, the cells may be the cells described in relation to FIG. 5. For this case, at block 1510, at least two options are disclosed herein. In the first option, the anchor cell is the cell currently selected via L1/L2 signaling. In the second option, the anchor cell is a default cell, which may be different from the current selected cell. In some aspects, the default cell can be determined between the gNB and UE via RRC, MAC-CE, and/or DCI signaling, and the UE can switch to the default cell to perform the fallback operations (e.g., CFRA/CBRA, BFR/RLR, broadcast/multicast reception, BFD/RLM, SR, etc.).

[0159] FIG. 16 is a flow chart illustrating a second exemplary process for selecting an anchor cell for L1/L2 centric inter-cell mobility. At block 1605, a UE has multiple simultaneously selected/serving cells (or PCIs). For example, the cells may be the cells described in relation to FIG. 5. For this case, at block 1610, at least two options are disclosed herein. In the first option, the anchor cell can be one of the cells currently selected via L1/L2 signaling. To this end, the anchor cell can be determined between the gNB and UE via RRC, MAC-CE, and/or DCI signaling, and the EE can switch to the anchor cell to perform the fallback operations. In the second option, the anchor cell can be a default cell, which may be different from the current selected cell. The default cell can be determined between the gNB and UE via RRC, MAC-CE, and/or DCI signaling, and the UE can switch to the default cell to perform the fallback operations.

[0160] FIG. 17 is a block diagram illustrating an example of a hardware implementation for a scheduling entity 1700 employing a processing system 1714. For example, the scheduling entity 1700 may be a UE as illustrated in any one or more of the FIGs. 1, 2, 3, 5, and 6 disclosed herein. In another example, the scheduling entity 1700 may be a base station (e.g., a gNB) as also illustrated in any one or more of the FIGs. 1, 2, 3, 5, and 6 disclosed herein.

[0161] The scheduling entity 1700 may be implemented with a processing system 1714 that includes one or more processors 1704. Examples of processors 1704 include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. In various examples, the scheduling entity 1700 may be configured to perform any one or more of the functions described herein. That is, the processor 1704, as utilized in a scheduling entity 1700, may be used to implement any one or more of the processes and procedures described herein, for example, illustrated in FIG. 18.

[0162] In this example, the processing system 1714 may be implemented with a bus architecture, represented generally by the bus 1702. The bus 1702 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 1714 and the overall design constraints. The bus 1702 communicatively couples together various circuits including one or more processors (represented generally by the processor 1704), a memory 1705, and computer-readable media (represented generally by the computer-readable medium 1706). The bus 1702 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. A bus interface 1708 provides an interface between the bus 1702 and a transceiver 1710. The transceiver 1710 provides a communication interface or means for communicating with various other apparatus over a transmission medium. Depending upon the nature of the apparatus, a user interface 1712 (e.g., keypad, display, speaker, microphone, joystick) may also be provided.

[0163] In some aspects of the disclosure, the processor 1704 may include a connecting circuitry 1740 configured for various functions, including, for example, to facilitate configuring a scheduled entity (e.g., a UE) to connect with at least one of a plurality of cells based on L1/L2 signaling, wherein the L1/L2 signaling includes at least one of a first portion comprising physical layer signaling or a second portion comprising MAC layer signaling. As illustrated, the processor 1704 may also include a selecting circuitry 1742 configured for various functions. For instance, the selecting circuitry 1742 may facilitate configuring the scheduled entity to select an anchor cell from the plurality of cells. The processor 1704 may further include fallback circuitry 1744 configured for various functions, including, for example, to facilitate configuring the scheduled entity to determine a fallback condition and perform a fallback operation on the anchor cell. It should also be appreciated that, the combination of the connecting circuitry 1740, the selecting circuitry 1742, and the fallback circuitry 1744 may be configured to implement one or more of the functions described herein.

[0164] Various other aspects of scheduling entity 1700 are also contemplated. In some implementations, for instance, it is contemplated that scheduling entity 1700 may configure the scheduled entity to switch between the plurality of cells one at a time. For example, in a particular implementation, scheduling entity 1700 may configure the scheduled entity to select a cell currently connected with the scheduled entity as the anchor cell. Alternatively, scheduling entity 1700 may configure the scheduled entity to identify a default cell amongst the plurality of cells and select the default cell as the anchor cell, wherein scheduling entity 1700 may configure the scheduled entity to predetermine the default cell via RRC signaling, physical layer signaling, or MAC layer signaling, for example.

[0165] In another aspect of the disclosure, it is contemplated that scheduling entity 1700 may configure the scheduled entity to connect with at least two of the plurality of cells at a time. For example, in a particular implementation, scheduling entity 1700 may configure the scheduled entity to select one of the at least two cells currently connected with the scheduled entity as the anchor cell. Within such implementation, scheduling entity 1700 may configure the scheduled entity to predetermine the anchor cell via RRC signaling, physical layer signaling, or MAC layer signaling, for example. Alternatively, scheduling entity 1700 may configure the scheduled entity to identify a default cell amongst the plurality of cells and select the default cell as the anchor cell, wherein scheduling entity 1700 may configure the scheduled entity to predetermine the default cell via RRC signaling, physical layer signaling, or MAC layer signaling, for example.

[0166] In yet another aspect of the disclosure, various exemplary fallback operations are contemplated. For instance, it is contemplated that such fallback operations may include: a contention-free random access (CFRA) operation; a contention-based random access (CBRA) operation; acquiring information regarding at least one of a broadcast communication or a multicast communication; reference signal measurements; or transmitting a scheduling request (SR) associated with an uplink (UL) grant.

[0167] Referring back to the remaining components of scheduling entity 1700, it should be appreciated that the processor 1704 is responsible for managing the bus 1702 and general processing, including the execution of software stored on the computer-readable medium 1706. The software, when executed by the processor 1704, causes the processing system 1714 to perform the various functions described below for any particular apparatus. The computer-readable medium 1706 and the memory 1705 may also be used for storing data that is manipulated by the processor 1704 when executing software.

[0168] One or more processors 1704 in the processing system may execute software.

Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium 1706. The computer-readable medium 1706 may be a non-transitory computer-readable medium. A non-transitory computer-readable medium includes, by way of example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD) or a digital versatile disc (DVD)), a smart card, a flash memory device (e.g., a card, a stick, or a key drive), a random access memory (RAM), a read only memory (ROM), a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable PROM (EEPROM), a register, a removable disk, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. The computer-readable medium may also include, by way of example, a carrier wave, a transmission line, and any other suitable medium for transmitting software and/or instructions that may be accessed and read by a computer. The computer-readable medium 1706 may reside in the processing system 1714, external to the processing system 1714, or distributed across multiple entities including the processing system 1714. The computer-readable medium 1706 may be embodied in a computer program product. By way of example, a computer program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

[0169] In one or more examples, the computer-readable storage medium 1706 may include connecting software 1752 configured for various functions, including, for example, to facilitate configuring a scheduled entity to connect with at least one of a plurality of cells based on L1/L2 signaling, wherein the L1/L2 signaling includes at least one of a first portion comprising physical layer signaling or a second portion comprising MAC layer signaling. As illustrated, the computer-readable storage medium 1706 may also include selecting software 1754 configured for various functions. For instance, the selecting software 1754 may facilitate configuring the scheduled entity to select an anchor cell from the plurality of cells. The computer-readable storage medium 1706 may further include fallback software 1756 configured for various functions, including, for example, to facilitate configuring the scheduled entity to perform a fallback operation on the anchor cell.

[0170] In a particular configuration, it is also contemplated that the scheduling entity

1700 includes means for configuring a scheduled entity (e.g., a UE) to connect with at least one of a plurality of cells based on L1/L2 signaling, wherein the L1/L2 signaling includes at least one of a first portion comprising physical layer signaling or a second portion comprising MAC layer signaling; means for configuring the scheduled entity to select an anchor cell from the plurality of cells; and means for configuring the scheduled entity to perform a fallback operation on the anchor cell. In one aspect, the aforementioned means may be the processor(s) 1704 configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a circuit or any apparatus configured to perform the functions recited by the aforementioned means.

[0171] Of course, in the above examples, the circuitry included in the processor 1704 is merely provided as an example, and other means for carrying out the described functions may be included within various aspects of the present disclosure, including but not limited to the instructions stored in the computer-readable storage medium 1706, or any other suitable apparatus or means described herein and utilizing, for example, the processes and/or algorithms described herein, for example, in relation to FIG. 18.

[0172] In FIG. 18, a flow chart is provided, which illustrates an exemplary scheduling entity process that facilitates some aspects of the disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process 1800 may be carried out by the scheduling entity 1700 illustrated in FIG. 17. In some examples, the process 1800 may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

[0173] Process 1800 begins at block 1810 with the scheduling entity 1700 (e.g., a gNB) configuring a scheduled entity (e.g., a UE) to connect with at least one of a plurality of cells using signaling including at least one of LI signaling or L2 signaling. For example, the signaling includes at least one of a first portion comprising physical layer signaling or a second portion comprising MAC layer signaling. In some aspects, the connecting circuitry 1740 can provide the means for configuring the scheduled entity to connect with at least one of a plurality of cells. In some aspects, the scheduling entity can configure the scheduled entity to switch between the plurality of cells one at a time or connect with at least two of the plurality of cells at a time.

[0174] In one aspect, the scheduling entity can configure the scheduled entity to select an anchor cell from the plurality of cells based on a predetermined rule. In one aspect, the predetermined rule may include selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell. In one aspect, the predetermined rule may include identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell. In some aspects, the scheduling entity can configure the scheduled entity to determine the anchor cell/default cell via RRC signaling, physical layer signaling, or MAC layer signaling with the scheduling entity.

[0175] Process 1800 then proceeds to block 1820 where the scheduling entity 1700 configures the scheduled entity to determine a fallback condition. In some aspects, the fallback circuitry 1744 can provide the means for configuring the scheduled entity to determine a fallback condition (e.g., BFD, BFR, RLR).

[0176] Process 1800 then proceeds to block 1830 where the scheduling entity 1700 configures the scheduled entity to select an anchor cell from the plurality of cells. In some aspects, the selecting circuitry 1742 can provide the means for configuring the scheduled entity to select the anchor cell based on a predetermined rule. In one aspect, the scheduling entity can configure the scheduled entity to select one of the plurality of cells currently connected with the scheduled entity as the anchor cell. In another aspect, the scheduling entity can configure the scheduled entity to identify a default cell amongst the plurality of cells, and select the default cell as the anchor cell.

[0177] Process 1800 then concludes at block 1840 where, in response to the fallback condition, the scheduling entity 1700 configures the scheduled entity to perform a fallback operation on the anchor cell. In some aspects, the fallback circuitry 1744 can provide the means for configuring the scheduled entity to perform the fallback operation.

[0178] In one aspect, the fallback operation may include a CFRA/CBRA operation. In one aspect, the fallback operation may include acquiring information regarding at least one of a broadcast communication or a multicast communication. In one aspect, the fallback operation may include measuring a reference signal to detect failure of a control beam or monitor a radio link. In one aspect, the fallback operation may include transmitting a scheduling request associated with an uplink grant.

[0179] FIG. 19 is a conceptual diagram illustrating an example of a hardware implementation for an exemplary scheduled entity 1900 employing a processing system 1914. In accordance with various aspects of the disclosure, an element, or any portion of an element, or any combination of elements may be implemented with a processing system 1914 that includes one or more processors 1904. For example, the scheduled entity 1900 may be a UE as illustrated in any one or more of the FIGs. 1, 2, 3, 5, and 6 disclosed herein.

[0180] The processing system 1914 may be substantially the same as the processing system 1714 illustrated in FIG. 17, including a bus interface 1908, a bus 1902, memory 1905, a processor 1904, and a computer-readable medium 1906. Furthermore, the scheduled entity 1900 may include a user interface 1912 and a transceiver 1910 substantially similar to those described above in FIG. 17. That is, the processor 1904, as utilized in a scheduled entity 1900, may be used to implement any one or more of the processes described below and illustrated in the various figures.

[0181] In some aspects of the disclosure, the processor 1904 may include a connecting circuitry 1940 configured for various functions, including, for example, to connect the scheduled entity 1900 with at least one of a plurality of cells using signaling including L1/L2 signaling. For example, the L1/L2 signaling includes at least one of a first portion comprising physical layer signaling or a second portion comprising MAC layer signaling. As illustrated, the processor 1904 may also include a selecting circuitry 1942 configured for various functions. For instance, the selecting circuitry 1942 may be configured to select an anchor cell from the plurality of cells. The processor 1904 may further include a fallback circuitry 1944 configured for various functions, including, for example, to perform a fallback operation on the anchor cell. Furthermore, it should be appreciated that, the combination of the connecting circuitry 1940, the selecting circuitry 1942, and the fallback circuitry 1944 may be configured to implement one or more of the functions described herein.

[0182] Various other aspects of scheduled entity 1900 are also contemplated. In some implementations, for instance, it is contemplated that scheduled entity 1900 may be configured to switch between the plurality of cells one at a time. For example, in a particular implementation, scheduled entity 1900 may be configured to select a cell currently connected with the scheduled entity 1900 as the anchor cell. Alternatively, scheduled entity 1900 may be configured to identify a default cell amongst the plurality of cells and select the default cell as the anchor cell, wherein scheduled entity 1900 may be configured to predetermine the default cell via RRC signaling, physical layer signaling, or MAC layer signaling, for example.

[0183] In another aspect of the disclosure, it is contemplated that scheduled entity 1900 may be configured to simultaneously connect with at least two of the plurality of cells at a time. For example, in a particular implementation, scheduled entity 1900 may be configured to select one of the at least two cells currently connected with the scheduled entity 1900 as the anchor cell. Within such implementation, scheduled entity 1900 may be configured to predetermine the anchor cell via RRC signaling, physical layer signaling, or MAC layer signaling, for example. Alternatively, scheduled entity 1900 may be configured to identify a default cell amongst the plurality of cells and select the default cell as the anchor cell, wherein scheduled entity 1900 may be configured to predetermine the default cell via RRC signaling, physical layer signaling, or MAC layer signaling, for example.

[0184] In yet another aspect of the disclosure, various exemplary fallback operations are contemplated. For instance, it is contemplated that such fallback operations may include: a CFRA operation; a CBRA operation; acquiring information regarding at least one of a broadcast communication or a multicast communication; reference signal measurements; or transmitting an SR associated with an UL grant. [0185] Referring back to the remaining components of scheduled entity 1900, similar to processor 1704, processor 1904 is responsible for managing the bus 1902 and general processing, including the execution of software stored on the computer-readable medium 1906. The software, when executed by the processor 1904, causes the processing system 1914 to perform the various functions described below for any particular apparatus. The computer-readable medium 1906 and the memory 1905 may also be used for storing data that is manipulated by the processor 1904 when executing software.

[0186] One or more processors 1904 in the processing system may execute software.

Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a computer-readable medium 1906. Similar to computer-readable medium 1706, computer-readable medium 1906 may be a non-transitory computer- readable medium comprising characteristics that are substantially similar. The computer- readable medium 1906 may reside in the processing system 1914, external to the processing system 1914, or distributed across multiple entities including the processing system 1914. It should also be appreciated that, similar to computer-readable medium 1706, computer-readable medium 1906 may be embodied in a computer program product comprising characteristics that are substantially similar.

[0187] In one or more examples, the computer-readable storage medium 1906 may include connecting software 1952 configured for various functions, including, for example, to connect the scheduled entity 1900 with at least one of a plurality of cells based on L1/L2 signaling, wherein the L1/L2 signaling includes at least one of a first portion comprising physical layer signaling or a second portion comprising MAC layer signaling. As illustrated, the computer-readable medium 1906 may also include selecting software 1954 configured for various functions. For instance, the selecting software 1954 may be configured to select an anchor cell from the plurality of cells. The computer- readable medium 1906 may further include fallback software 1956 configured for various functions, including, for example, to perform a fallback operation on the anchor cell. Furthermore, it should be appreciated that, the combination of the connecting software 1952, the selecting software 1954, and the fallback software 1956 may be configured to implement one or more of the functions described herein. [0188] In a particular configuration, it is also contemplated that the scheduled entity 1900 includes means for connecting with at least one of a plurality of cells based on L1/L2 signaling, wherein the L1/L2 signaling includes at least one of a first portion comprising physical layer signaling or a second portion comprising MAC layer signaling; means for selecting an anchor cell from the plurality of cells; and means for performing a fallback operation on the anchor cell. In one aspect, the aforementioned means may be the processor(s) 1904 configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a circuit or any apparatus configured to perform the functions recited by the aforementioned means.

[0189] Of course, in the above examples, the circuitry included in the processor 1904 is merely provided as an example, and other means for carrying out the described functions may be included within various aspects of the present disclosure, including but not limited to the instructions stored in the computer-readable storage medium 1906, or any other suitable apparatus or means described herein, and utilizing, for example, the processes and/or algorithms described herein, for example, in relation to FIG. 20.

[0190] In FIG. 20, a flow chart is provided, which illustrates an exemplary scheduled entity process for performing some aspects of the disclosure. As described below, some or all illustrated features may be omitted in a particular implementation within the scope of the present disclosure, and some illustrated features may not be required for implementation of all embodiments. In some examples, the process 2000 may be carried out by the scheduled entity 1900 illustrated in FIG. 19. In some examples, the process 2000 may be carried out by any suitable apparatus or means for carrying out the functions or algorithm described below.

[0191] Process 2000 begins at block 2010 with the scheduled entity 1900 connecting with at least one of a plurality of cells using signaling including at least one of LI signaling or L2 signaling. For example, the signaling includes at least one of a first portion comprising physical layer signaling (LI signaling) or a second portion comprising MAC layer signaling (L2 signaling). In some aspects, the connecting circuitry 1940 can provide the means for connecting with the plurality of cells. In some aspects, the scheduled entity can switch between the plurality of cells one at a time or connect with at least two of the plurality of cells at a time.

[0192] At block 2020, process 2000 continues with the scheduled entity 1900 determining a fallback condition. In some aspects, the fallback circuitry 2044 can provide the means for determining the fallback condition (e.g., BFD, BFR, RLR). [0193] At block 2030, process 2000 continues with the scheduled entity 1900 selecting an anchor cell from the plurality of cells. In one aspect, the scheduled entity select one of the plurality of cells currently connected with the scheduled entity as the anchor cell. In one aspect, the scheduled entity can identify a default cell amongst the plurality of cells, and select the default cell as the anchor cell. In some aspects, the scheduled entity can determine the anchor cell/default cell via RRC signaling, physical layer signaling, and/or MAC layer signaling with the scheduling entity. For example, the scheduling entity can transmit the rule for selecting the anchor cell/default cell to the scheduled entity using RRC signaling, physical layers signaling, or MAC layer signaling.

[0194] In some aspects, the selecting circuitry 1942 can provide the means for selecting the anchor cell. In one aspect, the scheduled entity can select one of the plurality of cells currently connected with the scheduled entity as the anchor cell. In another aspect, the scheduled entity can identify a default cell amongst the plurality of cells, and select the default cell as the anchor cell.

[0195] Process 2000 then concludes at block 2040 where the scheduled entity 1900 performs a fallback operation on the anchor cell. In some aspects, the fallback circuitry 1944 can provide the means for determining a fallback condition and performing the fallback operation. In one aspect, the fallback operation may include a CFRA/CBRA operation. In one aspect, the fallback operation may include acquiring information regarding at least one of a broadcast communication or a multicast communication from the scheduling entity. In one aspect, the fallback operation may include measuring a reference signal to detect failure of a control beam or monitor a radio link. In one aspect, the fallback operation may include transmitting a scheduling request associated with an uplink grant.

[0196] In one configuration, the apparatus 1700 and/or 1900 for wireless communication includes various means for performing the methods, procedures, steps, and processes described herein. In one aspect, the aforementioned means may be the processor(s) 1704/1904 shown in FIG. 17/19 configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a circuit or any apparatus configured to perform the functions recited by the aforementioned means.

[0197] Of course, in the above examples, the circuitry included in the processor

1704/1904 is merely provided as an example, and other means for carrying out the described functions may be included within various aspects of the present disclosure, including but not limited to the instructions stored in the computer-readable storage medium 1706/1906, or any other suitable apparatus or means described in any one of the FIGs. 1, 2, 3, 5, 10 and/or 13, and utilizing, for example, the processes and/or algorithms described herein in relation to FIGs. 8-16, 18, and/or 20.

[0198] In a first aspect, a method of wireless communication operable at a scheduled entity is disclosed. The method comprises connecting with at least one of a plurality of cells using signaling comprising at least one of LI signaling or L2 signaling; determining a fallback condition; selecting an anchor cell from the plurality of cells based on a predetermined rule comprising at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell; and performing, in response to the fallback condition, a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

[0199] In a second aspect, alone or in combination with the first aspect, wherein the connecting comprises at least one of: switching between the plurality of cells one at a time; or connecting with at least two of the plurality of cells at a time.

[0200] In a third aspect, alone or in combination with any of the first to second aspects, the method further comprises at least one of: determining the anchor cell via radio resource control (RRC) signaling; determining the anchor cell via physical layer signaling; or determining the anchor cell via medium access control (MAC) layer signaling.

[0201] In a fourth aspect, alone or in combination with any of the first to third aspects, the method further comprises at least one of: determining the default cell via radio resource control (RRC) signaling; determining the default cell via physical layer signaling; or determining the default cell via medium access control (MAC) layer signaling.

[0202] In a fifth aspect, alone or in combination with any of the first to fourth aspects, wherein the fallback operation comprises at least one of: a contention-free random access (CFRA) operation; a contention-based random access (CBRA) operation; acquiring information regarding at least one of a broadcast communication or a multicast communication; measuring a reference signal to detect failure of a control beam or monitor a radio link; or transmitting a scheduling request associated with an uplink grant.

[0203] In a sixth aspect, a scheduled entity for wireless communication comprises: a communication interface configured for wireless communication with a scheduling entity; a memory; and a processor operatively coupled with the communication interface and the memory, wherein the processor and the memory are configured to: connect with at least one of a plurality of cells using signaling comprising at least one of layer 1 (LI) signaling or layer (L2) signaling; determine a fallback condition; select an anchor cell from the plurality of cells based on a predetermined rule comprising at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell; and perform, in response to the fallback condition, a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

[0204] In a seventh aspect, alone or in combination with the sixth aspect, wherein the processor and the memory are further configured to connect with the at least one of the plurality of cells by, at least one of: switching between the plurality of cells one at a time; or connecting with at least two of the plurality of cells at a time.

[0205] In an eighth aspect, alone or in combination with any of the sixth to seventh aspects, wherein the processor and the memory are further configured to, at least one of: determine the anchor cell via radio resource control (RRC) signaling; determine the anchor cell via physical layer signaling; or determine the anchor cell via medium access control (MAC) layer signaling.

[0206] In a ninth aspect, alone or in combination with any of the sixth to eighth aspects, wherein the processor and the memory are further configured to, at least one of: determine the default cell via radio resource control (RRC) signaling; determine the default cell via physical layer signaling; or determine the default cell via MAC layer signaling.

[0207] In a tenth aspect, alone or in combination with any of the sixth to ninth aspects, wherein the fallback operation comprises at least one of: a contention-free random access (CFRA) operation; a contention-based random access (CBRA) operation; acquiring information regarding at least one of a broadcast communication or a multicast communication; measuring a reference signal to detect failure of a control beam or monitor a radio link; or transmitting a scheduling request associated with an uplink grant.

[0208] In an eleventh aspect, a method of wireless communication at a scheduling entity is disclosed. The method comprises: configuring a scheduled entity to connect with at least one of a plurality of cells using signaling comprising at least one of layer 1 (LI) signaling or layer 2 (L2) signaling; configuring the scheduled entity to determine a fallback condition; configuring the scheduled entity to select an anchor cell from the plurality of cells based on a predetermined rule comprising at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell; and configuring the scheduled entity, in response to the fallback condition, to perform a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

[0209] In a twelfth aspect, alone or in combination with the eleventh aspect, the method further comprises: configuring the scheduled entity to switch between the plurality of cells one at a time; or configuring the scheduled entity to connect with at least two of the plurality of cells at a time.

[0210] In a thirteenth aspect, alone or in combination with any of the eleventh to twelfth aspects, the method further comprises configuring the scheduled entity to, at least one of: determine the anchor cell via radio resource control (RRC) signaling; determine the anchor cell via physical layer signaling; or determine the anchor cell via medium access control (MAC) layer signaling.

[0211] In a fourteenth aspect, alone or in combination with any of the eleventh to thirteenth aspects, the method further comprises configuring the scheduled entity to, at least one of: determine the default cell via radio resource control (RRC) signaling; determine the default cell via physical layer signaling; or determine the default cell via medium access control (MAC) layer signaling.

[0212] In a fifteenth aspect, alone or in combination with any of the eleventh to fourteenth aspects, wherein the fallback operation comprises at least one of: a contention-free random access (CFRA) operation; a contention-based random access (CBRA) operation; acquiring information regarding at least one of a broadcast communication or a multicast communication; measuring a reference signal to detect failure of a control beam or monitor a radio link; or transmitting a scheduling request associated with an uplink grant.

[0213] In a sixteenth aspect, a scheduling entity for wireless communication comprises: a communication interface configured for wireless communication with a scheduled entity; a memory; and a processor operatively coupled with the communication interface and the memory. Wherein the processor and the memory are configured to: configure the scheduled entity to connect with at least one of a plurality of cells using signaling comprising at least one of layer 1 (LI) signaling or layer 2 (L2) signaling; configure the scheduled entity to determine a fallback condition; configure the scheduled entity to select an anchor cell from the plurality of cells based on a predetermined rule comprising at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell; and configure the scheduled entity, in response to the fallback condition, to perform a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

[0214] In a seventeenth aspect, alone or in combination with the sixteenth aspect, wherein the processor and the memory are further configured to: configure the scheduled entity to switch between the plurality of cells one at a time; or configure the scheduled entity to connect with at least two of the plurality of cells at a time.

[0215] In an eighteenth aspect, alone or in combination with any of the sixteenth to seventeenth aspects, wherein the processor and the memory are further configured to configure the scheduled entity to, at least one of: determine the anchor cell via radio resource control (RRC) signaling; determine the anchor cell via physical layer signaling; or determine the anchor cell via medium access control (MAC) layer signaling.

[0216] In a nineteenth aspect, alone or in combination with any of the sixteenth to eighteenth aspects, wherein the processor and the memory are further configured to configure the scheduled entity to, at least one of: determine the default cell via radio resource control (RRC) signaling; determine the default cell via physical layer signaling; or determine the default cell via medium access control (MAC) layer signaling.

[0217] In a twentieth aspect, alone or in combination with any of the sixteenth to nineteenth aspects, wherein the fallback operation comprises at least one of: a contention- free random access (CFRA) operation; a contention-based random access (CBRA) operation; acquiring information regarding at least one of a broadcast communication or a multicast communication; measuring a reference signal to detect failure of a control beam or monitor a radio link; or transmitting a scheduling request associated with an uplink grant.

[0218] In a twenty-first aspect, a method for wireless communications by a user equipment (UE) is disclosed. The method comprises: receiving a command to switch from a current cell to a new cell signaled via physical layer or medium access control (MAC) layer signaling; determining an initial beam to use for at least one of uplink or downlink transmissions in the new cell before the UE receives a transmission configuration indicator (TCI) activation or configuration command; and communicating in the new cell using the initial beam. [0219] In a twenty-second aspect, alone or in combination with the twenty-first aspect, wherein the command is signaled via a downlink control information (DCI) or medium access control (MAC) control element (MAC CE).

[0220] In a twenty-third aspect, alone or in combination with any of the twenty-first to twenty-second aspects, wherein the initial beam is determined based on a reference signal (RS) ID indicated in the command.

[0221] In a twenty-fourth aspect, alone or in combination with any of the twenty-first to twenty-second aspects, wherein the initial beam is determined based on a latest physical layer metric report generated by the UE prior to receiving the command to switch from the current cell to the new cell.

[0222] In a twenty-fifth aspect, alone or in combination with any of the twenty-first to twenty-second aspects, wherein the initial beam is determined based on an implicit indication of a best reported reference signal in a latest physical layer metric report generated by the UE prior to receiving the command to switch from the current cell to the new cell.

[0223] In a twenty-sixth aspect, alone or in combination with any of the twenty-first to twenty-fifth aspects, wherein the UE stops using the initial beam after receiving a TCI activation command.

[0224] In a twenty-seventh aspect, alone or in combination with any of the twenty-first to twenty-fifth aspects, wherein: the UE uses the initial beam for processing at least one of a physical downlink control channel (PDCCH) or a physical downlink shared channel (PDSCH); and stops using the initial beam after receiving any TCI activation or configuration command for PDCCH or PDSCH in the new cell.

[0225] In a twenty-eighth aspect, alone or in combination with any of the twenty-first to twenty-fifth aspects, wherein the UE stops using the initial beam after receiving a certain type of downlink transmission in the new cell that indicates a TCI activation.

[0226] In a twenty-ninth aspect, alone or in combination with the twenty-eighth, wherein the downlink transmission comprises at least one of a tracking reference signal (TRS), channel state information reference signal (CSI-RS), or physical downlink control channel (PDCCH).

[0227] In a thirtieth aspect, a method for wireless communications by a network entity is disclosed. The method comprises: transmitting, to a user equipment (UE), a command to switch from a current cell to a new cell signaled via physical layer or medium access control (MAC) layer signaling; determining an initial beam for the UE to use for at least one of uplink or downlink transmissions in the new cell before the UE receives a transmission configuration indicator (TCI) activation or configuration command; and communicating with the UE in the new cell using the initial beam.

[0228] In a thirty-first aspect, alone or in combination with the thirtieth aspect, wherein the command is signaled via a downlink control information (DCI) or medium access control (MAC) control element (MAC CE).

[0229] In a thirty-second aspect, alone or in combination with any of the thirtieth to thirty- first aspects, wherein the initial beam is determined based on a reference signal (RS) ID indicated in the command.

[0230] In a thirty -third aspect, alone or in combination with any of the thirtieth to thirty- first aspects, wherein the initial beam is determined based on a latest physical layer metric report generated by the UE prior to receiving the command to switch from the current cell to the new cell.

[0231] In a thirty-fourth aspect, alone or in combination with any of the thirtieth to thirty- first aspects, wherein the initial beam is determined based on an implicit indication of a best reported reference signal in a latest physical layer metric report generated by the UE prior to receiving the command to switch from the current cell to the new cell.

[0232] In a thirty-fifth aspect, alone or in combination with any of the thirtieth to thirty- fourth aspects, wherein the UE stops using the initial beam after receiving a TCI activation command.

[0233] In a thirty-sixth aspect, alone or in combination with any of the thirtieth to thirty- fourth aspects, the UE uses the initial beam for processing at least one of a physical downlink control channel (PDCCH) or a physical downlink shared channel (PDSCH); and stops using the initial beam after receiving any TCI activation or configuration command for PDCCH or PDSCH in the new cell.

[0234] In a thirty-seventh aspect, alone or in combination with any of the thirtieth to thirty-fourth aspects, wherein the UE stops using the initial beam after receiving a certain type of downlink transmission in the new cell that indicates a TCI activation.

[0235] In a thirty-eighth aspect, alone or in combination with the thirty-seventh aspect, wherein the downlink transmission comprises at least one of a tracking reference signal (TRS), channel state information reference signal (CSI-RS), or physical downlink control channel (PDCCH).

[0236] In a thirty-nineth aspect, a method for wireless communications by a user equipment (UE) is disclosed. The method comprises: receiving a command, signaled via physical layer or medium access control (MAC) layer signaling, that indicates at least one of: at least one cell or at least one physical cell ID (PCI) to serve the UE; determining a default beam for a physical downlink shared channel (PDSCH) transmission in the indicated cell or PCI cell; and communicating in the new cell using the default beam.

[0237] In a fortieth aspect, alone or in combination with the thirty-ninth aspect, wherein the UE is configured to use the default beam if the PDSCH transmission is scheduled within a threshold scheduling period by a downlink control information (DCI) that carries a corresponding transmission configuration indicator (TCI) state for the PDSCH transmission.

[0238] In a forty-first aspect, alone or in combination with the fortieth aspect, wherein the threshold scheduling period is at least one of configured or determined based on capability of the UE.

[0239] In a forty-second aspect, alone or in combination with any of the thirty-ninth to forty-first aspects, wherein the command switches the UE from a current PCI to a new PCI in a same serving cell.

[0240] In a forty-third aspect, alone or in combination with the forty-second aspect, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in an active downlink bandwidth part (BWP) of the new PCI.

[0241] In a forty-fourth aspect, alone or in combination with the forty-second aspect, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in a default downlink bandwidth part (BWP) of a default PCI.

[0242] In a forty-fifth aspect, alone or in combination with the forty-fourth aspect, the method further comprises receiving signaling indicating the default PCI.

[0243] In a forty-sixth aspect, alone or in combination with the forty -fifth aspect, wherein the received signaling comprises one of radio resource control (RRC) signaling, a medium access control (MAC) control element (CE) (MAC-CE), or a downlink control information (DCI).

[0244] In a forty-seventh aspect, alone or in combination with any of the thirty-ninth to forty-sixth aspects, wherein: the command configures the UE to be served by multiple PCIs; and the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in one or more active downlink bandwidth part (BWP) of one or more of the multiple PCIs. [0245] In a forty-eighth aspect, alone or in combination with the forty-seventh aspect, the method further comprises receiving signaling indicating the one or more PCIs.

[0246] In a forty-ninth aspect, alone or in combination with the forty-eighth aspect, wherein the received signaling comprises one of radio resource control (RRC) signaling, a medium access control (MAC) control element (CE) (MAC-CE), or a downlink control information (DCI).

[0247] In a fiftieth aspect, alone or in combination with any of the forty-seventh to forty- ninth aspects, wherein: the CORESET is selected based on a lowest or highest value of a CORESET ID; and if more than one of the PCIs have a same lowest or highest CORESET ID, the one or more PCIs are determined based on a PCI index among the PCIs having the same lowest or highest CORESET ID.

[0248] In a fifty-first aspect, alone or in combination with any of the thirty-ninth to fiftieth aspects, wherein the command configures the UE to be served by one or more serving cells.

[0249] In a fifty-second aspect, alone or in combination with the fifty-first aspect, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in an active downlink bandwidth part (BWP) of one or more of the serving cells.

[0250] In a fifty -third aspect, alone or in combination with the fifty -first aspect, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in a default downlink bandwidth part (BWP) of a default serving cell.

[0251] In a fifty-fourth aspect, alone or in combination with the fifty-third aspect, the method further comprises receiving signaling indicating the default serving cell.

[0252] In a fifty-fifth aspect, alone or in combination with any of the thirty -ninth to forty- one aspects, wherein: the command configures the UE to be served by multiple serving cells; and the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in one or more active downlink bandwidth part (BWP) of one or more of the multiple serving cells.

[0253] In a fifty-sixth aspect, alone or in combination with any of the thirty-ninth to forty- one and fifty-fifth aspects, the method further comprises receiving signaling indicating the one or more serving cells.

[0254] In a fifty-seventh aspect, alone or in combination with any of the thirty-ninth to forty-one, fifty-fifth, and fifty-sixth aspects, wherein: the CORESET is selected based on a lowest or highest value of a CORESET ID; and if more than one of the serving cells have a same lowest or highest CORESET ID, the one or more serving cells are determined based on a serving cell ID among the serving cells having the same lowest or highest CORESET ID.

[0255] In a fifty-eighth aspect, alone or in combination with any of the thirty-ninth to forty-one aspects, wherein, if no control resource set (CORESET) is configured for a downlink bandwidth part (BWP), the default beam is determined based on a spatial quasi colocation (QCL) reference signal of an active PDSCH transmission configuration indicator (TCI) state on the downlink BWP.

[0256] In a fifty-ninth aspect, alone or in combination with the fifty-eighth aspect, wherein the default beam is determined based on the spatial QCL reference signal of an active PDSCH TCI state with a lowest or highest TCI state ID.

[0257] In a sixtieth aspect, a method for wireless communications by a network entity is disclosed. The method comprises: transmitting, to a user equipment (UE), a command, signaled via physical layer or medium access control (MAC) layer signaling, that indicates at least one of: at least one cell or at least one physical cell ID (PCI) to serve the UE; determining a default beam for the UE for a physical downlink shared channel (PDSCH) transmission in the indicated cell or PCI cell; and communicating with the UE in the new cell using the default beam.

[0258] In a sixty-first aspect, alone or in combination with the sixtieth aspect, wherein the UE is configured to use the default beam if the PDSCH transmission is scheduled within a threshold scheduling period by a downlink control information (DCI) that carries a corresponding transmission configuration indicator (TCI) state for the PDSCH transmission.

[0259] In a sixty-second aspect, alone or in combination with the sixty-first aspect, wherein the threshold scheduling period is at least one of configured or determined based on capability of the UE.

[0260] In a sixty-third aspect, alone or in combination with any of the sixtieth to sixty- second aspects, wherein the command switches the UE from a current PCI to a new PCI in a same serving cell.

[0261] In a sixty-fourth aspect, alone or in combination with any of the sixtieth to sixty- third aspects, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in an active downlink bandwidth part (BWP) of the new PCI. [0262] In a sixty-fifth aspect, alone or in combination with any of the sixtieth to sixty- third aspects, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in a default downlink bandwidth part (BWP) of a default PCI.

[0263] In a sixty-sixth aspect, alone or in combination with the sixth-fifth aspect, the method further comprises receiving signaling indicating the default PCI.

[0264] In a sixty-seventh aspect, alone or in combination with the sixth-sixth aspect, wherein the received signaling comprises one of radio resource control (RRC) signaling, a medium access control (MAC) control element (CE) (MAC-CE), or a downlink control information (DCI).

[0265] In a sixty-eighth aspect, alone or in combination with any of the sixtieth to sixth- second aspects, wherein: the command configures the UE to be served by multiple PCIs; and the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in one or more active downlink bandwidth part (BWP) of one or more of the multiple PCIs.

[0266] In a sixty-ninth aspect, alone or in combination with the sixth-eighth aspect, the method further comprises receiving signaling indicating the one or more PCIs.

[0267] In a seventieth aspect, alone or in combination with the sixth-ninth aspect, wherein the received signaling comprises one of radio resource control (RRC) signaling, a medium access control (MAC) control element (CE) (MAC-CE), or a downlink control information (DCI).

[0268] In a seventy-first aspect, alone or in combination with the sixth-eighth aspect, wherein: the CORESET is selected based on a lowest or highest value of a CORESET ID; and if more than one of the PCIs have a same lowest or highest CORESET ID, the one or more PCIs are determined based on a PCI index among the PCIs having the same lowest or highest CORESET ID.

[0269] In a seventy-second aspect, alone or in combination with the sixtieth aspect, wherein the command configures the UE to be served by one or more serving cells.

[0270] In a seventy-third aspect, alone or in combination with any of the sixtieth and seventy-second aspects, wherein the default beam is determined based on a quasi colocation (QCL) assumption for a control resource set (CORESET) in an active downlink bandwidth part (BWP) of one or more of the serving cells.

[0271] In a seventy -fourth aspect, alone or in combination with any of the sixtieth and seventy-second aspects, wherein the default beam is determined based on a quasi- colocation (QCL) assumption for a control resource set (CORESET) in a default downlink bandwidth part (BWP) of a default serving cell.

[0272] In a seventy-fifth aspect, alone or in combination with the seventy-fourth aspect, the method further comprises receiving signaling indicating the default serving cell.

[0273] In a seventy-sixth aspect, alone or in combination with any of the sixtieth to sixtieth-second aspects, wherein: the command configures the UE to be served by multiple serving cells; and the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in one or more active downlink bandwidth part (BWP) of one or more of the multiple serving cells.

[0274] In a seventy-seventh aspect, alone or in combination with the seventy-sixth aspect, the method further comprises receiving signaling indicating the one or more serving cells.

[0275] In a seventy-eighth aspect, alone or in combination with any of the seventy-sixth to seventy-seventh aspects, wherein: the CORESET is selected based on a lowest or highest value of a CORESET ID; and if more than one of the serving cells have a same lowest or highest CORESET ID, the one or more serving cells are determined based on a serving cell ID among the serving cells having the same lowest or highest CORESET ID.

[0276] In a seventy -ninth aspect, alone or in combination with any of the sixtieth to sixty- second aspects, wherein, if no control resource set (CORESET) is configured for a downlink bandwidth part (BWP), the default beam is determined based on a spatial quasi colocation (QCL) reference signal of an active PDSCH transmission configuration indicator (TCI) state on the downlink BWP.

[0277] In an eightieth aspect, alone or in combination with the seventy-ninth aspect, wherein the default beam is determined based on the spatial QCL reference signal of an active PDSCH TCI state with a lowest or highest TCI state ID.

[0278] In an eighty-first aspect, alone or in combination with the forty-seventh aspect, wherein the CORESET is selected based on a lowest CORESET ID in a latest slot in a monitored search space or CORESET.

[0279] In an eighty-second aspect, alone or in combination with the fifty-fifth aspect, wherein the CORESET is selected based on a lowest CORESET ID in a latest slot in a monitored search space or CORESET.

[0280] In an eighty -third aspect, alone or in combination with the sixtieth to sixty-second aspects, the method further comprises: determining a default uplink beam based on a received reference signal used to determine a default PDSCH beam per PCI. [0281] In an eighty-fourth aspect, alone or in combination with any of the sixtieth to sixty-second and eighty-third aspects, wherein the default uplink beam comprises a default beam for a physical uplink control channel (PUCCH) or a sounding reference signal (SRS) transmission if uplink beam indication is not configured or indicated by a base station.

[0282] In an eighty -fifth aspect, alone or in combination with any of the sixtieth to sixty- second and eighty-third aspects, wherein the reference signal used to determine the default PDSCH beam is used as a pathloss reference signal to measure pathloss for determining uplink transmission power.

[0283] In an eighty-sixth aspect, alone or in combination with any of the sixtieth to sixty- second and eighty-third aspects, wherein the default uplink beam comprises a default beam for a physical uplink shared channel (PUSCH) when the PUSCH is scheduled by a particular DCI format but no PUCCH with a configured spatial relation is configured in an active uplink BWP.

[0284] In an eighty-seventh aspect, alone or in combination with the sixty-eighth aspect, wherein the CORESET is selected based on a lowest CORESET ID in a latest slot in a monitored search space or CORESET.

[0285] In an eighty-eighth aspect, alone or in combination with the seventy-sixth aspect, wherein the CORESET is selected based on a lowest CORESET ID in a latest slot in a monitored search space or CORESET.

[0286] In an eighty-ninth aspect, alone or in combination with the sixty-eight aspect, the method further comprises: determining a default uplink beam based on a received reference signal used to determine a default PDSCH beam per PCI.

[0287] In a ninetieth aspect, alone or in combination with the eighty-ninth aspect, wherein the default uplink beam comprises a default beam for a physical uplink control channel (PUCCH) or a sounding reference signal (SRS) transmission if uplink beam indication is not configured or indicated by a base station.

[0288] In a ninety-first aspect, alone or in combination with the eighty-ninth aspect, wherein the default uplink beam comprises a default beam for a physical uplink shared channel (PUSCH) when the PUSCH is scheduled by a particular DCI format and no PUCCH with a configured spatial relation is configured in an active uplink BWP.

[0289] In a ninety-second aspect, alone or in combination with the eighty-ninth aspect, wherein the reference signal used to determine the default PDSCH beam is used as a pathloss reference signal to measure pathloss for determining uplink transmission power. [0290] Several aspects of a wireless communication network have been presented with reference to an exemplary implementation. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards.

[0291] By way of example, various aspects may be implemented within other systems defined by 3GPP, such as LTE, the Evolved Packet System (EPS), the Universal Mobile Telecommunication System (UMTS), and/or the Global System for Mobile (GSM). Various aspects may also be extended to systems defined by the 3rd Generation Partnership Project 2 (3GPP2), such as CDMA2000 and/or Evolution-Data Optimized (EV-DO). Other examples may be implemented within systems employing IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system.

[0292] Within the present disclosure, the word “exemplary” is used to mean “serving as an example, instance, or illustration.” Any implementation or aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects of the disclosure. Likewise, the term “aspects” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation. The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B, and object B touches object C, then objects A and C may still be considered coupled to one another — even if they do not directly physically touch each other. For instance, a first object may be coupled to a second object even though the first object is never directly physically in contact with the second object. The terms “circuit” and “circuitry” are used broadly, and intended to include both hardware implementations of electrical devices and conductors that, when connected and configured, enable the performance of the functions described in the present disclosure, without limitation as to the type of electronic circuits, as well as software implementations of information and instructions that, when executed by a processor, enable the performance of the functions described in the present disclosure.

[0293] One or more of the components, steps, features and/or functions illustrated in

FIGs. 1-20 may be rearranged and/or combined into a single component, step, feature or function or embodied in several components, steps, or functions. Additional elements, components, steps, and/or functions may also be added without departing from novel features disclosed herein. The apparatus, devices, and/or components illustrated in FIGs. 1-20 may be configured to perform one or more of the methods, features, or steps described herein. The novel algorithms described herein may also be efficiently implemented in software and/or embedded in hardware.

[0294] It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein.

[0295] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. A phrase referring to “at least one of’ a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a; b; c; a and b; a and c; b and c; and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.

Claims

1. A method of wireless communication at a scheduled entity, comprising: connecting with at least one of a plurality of cells using signaling comprising at least one of layer 1 (LI) signaling or layer 2 (L2) signaling; determining a fallback condition; selecting an anchor cell from the plurality of cells based on a predetermined rule comprising at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell; and performing, in response to the fallback condition, a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

2. The method of claim 1, wherein the connecting comprises at least one of: switching between the plurality of cells one at a time; or connecting with at least two of the plurality of cells at a time.

3. The method of claim 1, further comprising, at least one of: determining the anchor cell via radio resource control (RRC) signaling; determining the anchor cell via physical layer signaling; or determining the anchor cell via medium access control (MAC) layer signaling.

4. The method of claim 1, further comprising, at least one of: determining the default cell via radio resource control (RRC) signaling; determining the default cell via physical layer signaling; or determining the default cell via medium access control (MAC) layer signaling.

5. The method of claim 1, wherein the fallback operation comprises at least one of: a contention-free random access (CFRA) operation; a contention-based random access (CBRA) operation; acquiring information regarding at least one of a broadcast communication or a multicast communication; measuring a reference signal to detect failure of a control beam or monitor a radio link; or transmitting a scheduling request associated with an uplink grant.

6. A scheduled entity for wireless communication comprising: a communication interface configured for wireless communication with a scheduling entity; a memory; and a processor operatively coupled with the communication interface and the memory, wherein the processor and the memory are configured to: connect with at least one of a plurality of cells using signaling comprising at least one of layer 1 (LI) signaling or layer (L2) signaling; determine a fallback condition; select an anchor cell from the plurality of cells based on a predetermined rule comprising at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell; and perform, in response to the fallback condition, a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

7. The scheduled entity of claim 6, wherein the processor and the memory are further configured to connect with the at least one of the plurality of cells by, at least one of: switching between the plurality of cells one at a time; or connecting with at least two of the plurality of cells at a time.

8. The scheduled entity of claim 6, wherein the processor and the memory are further configured to, at least one of: determine the anchor cell via radio resource control (RRC) signaling; determine the anchor cell via physical layer signaling; or determine the anchor cell via medium access control (MAC) layer signaling.

9. The scheduled entity of claim 6, wherein the processor and the memory are further configured to, at least one of: determine the default cell via radio resource control (RRC) signaling; determine the default cell via physical layer signaling; or determine the default cell via MAC layer signaling.

10. The scheduled entity of claim 6, wherein the fallback operation comprises at least one of: a contention-free random access (CFRA) operation; a contention-based random access (CBRA) operation; acquiring information regarding at least one of a broadcast communication or a multicast communication; measuring a reference signal to detect failure of a control beam or monitor a radio link; or transmitting a scheduling request associated with an uplink grant.

11. A method of wireless communication at a scheduling entity, comprising: configuring a scheduled entity to connect with at least one of a plurality of cells using signaling comprising at least one of layer 1 (LI) signaling or layer 2 (L2) signaling; configuring the scheduled entity to determine a fallback condition; configuring the scheduled entity to select an anchor cell from the plurality of cells based on a predetermined rule comprising at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell; and configuring the scheduled entity, in response to the fallback condition, to perform a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

12. The method of claim 11, further comprising: configuring the scheduled entity to switch between the plurality of cells one at a time; or configuring the scheduled entity to connect with at least two of the plurality of cells at a time.

13. The method of claim 11, further comprising configuring the scheduled entity to, at least one of: determine the anchor cell via radio resource control (RRC) signaling; determine the anchor cell via physical layer signaling; or determine the anchor cell via medium access control (MAC) layer signaling.

14. The method of claim 11, further comprising configuring the scheduled entity to, at least one of: determine the default cell via radio resource control (RRC) signaling; determine the default cell via physical layer signaling; or determine the default cell via medium access control (MAC) layer signaling.

15. The method of claim 11, wherein the fallback operation comprises at least one of: a contention-free random access (CFRA) operation; a contention-based random access (CBRA) operation; acquiring information regarding at least one of a broadcast communication or a multicast communication; measuring a reference signal to detect failure of a control beam or monitor a radio link; or transmitting a scheduling request associated with an uplink grant.

16. A scheduling entity for wireless communication comprising: a communication interface configured for wireless communication with a scheduled entity; a memory; and a processor operatively coupled with the communication interface and the memory, wherein the processor and the memory are configured to: configure the scheduled entity to connect with at least one of a plurality of cells using signaling comprising at least one of layer 1 (LI) signaling or layer 2 (L2) signaling; configure the scheduled entity to determine a fallback condition; configure the scheduled entity to select an anchor cell from the plurality of cells based on a predetermined rule comprising at least one of: selecting one of the plurality of cells currently connected with the scheduled entity as the anchor cell; or identifying a default cell amongst the plurality of cells, and selecting the default cell as the anchor cell; and configure the scheduled entity, in response to the fallback condition, to perform a fallback operation on the anchor cell to maintain communication with the at least one of the plurality of cells.

17. The scheduling entity of claim 16, wherein the processor and the memory are further configured to: configure the scheduled entity to switch between the plurality of cells one at a time; or configure the scheduled entity to connect with at least two of the plurality of cells at a time.

18. The scheduling entity of claim 16, wherein the processor and the memory are further configured to configure the scheduled entity to, at least one of: determine the anchor cell via radio resource control (RRC) signaling; determine the anchor cell via physical layer signaling; or determine the anchor cell via medium access control (MAC) layer signaling.

19. The scheduling entity of claim 16, wherein the processor and the memory are further configured to configure the scheduled entity to, at least one of: determine the default cell via radio resource control (RRC) signaling; determine the default cell via physical layer signaling; or determine the default cell via medium access control (MAC) layer signaling.

20. The scheduling entity of claim 16, wherein the fallback operation comprises at least one of: a contention-free random access (CFRA) operation; a contention-based random access (CBRA) operation; acquiring information regarding at least one of a broadcast communication or a multicast communication; measuring a reference signal to detect failure of a control beam or monitor a radio link; or transmitting a scheduling request associated with an uplink grant.

21. A method for wireless communications by a user equipment (UE), comprising: receiving a command to switch from a current cell to a new cell signaled via physical layer or medium access control (MAC) layer signaling; determining an initial beam to use for at least one of uplink or downlink transmissions in the new cell before the UE receives a transmission configuration indicator (TCI) activation or configuration command; and communicating in the new cell using the initial beam.

22. The method of claim 21, wherein the command is signaled via a downlink control information (DCI) or medium access control (MAC) control element (MAC CE).

23. The method of claim 21, wherein the initial beam is determined based on a reference signal (RS) ID indicated in the command.

24. The method of claim 21, wherein the initial beam is determined based on a latest physical layer metric report generated by the UE prior to receiving the command to switch from the current cell to the new cell.

25. The method of claim 21, wherein the initial beam is determined based on an implicit indication of a best reported reference signal in a latest physical layer metric report generated by the UE prior to receiving the command to switch from the current cell to the new cell.

26. The method of claim 21, wherein the UE stops using the initial beam after receiving a TCI activation command.

27. The method of claim 26, wherein: the UE uses the initial beam for processing at least one of a physical downlink control channel (PDCCH) or a physical downlink shared channel (PDSCH); and stops using the initial beam after receiving any TCI activation or configuration command for PDCCH or PDSCH in the new cell.

28. The method of claim 21, wherein the UE stops using the initial beam after receiving a certain type of downlink transmission in the new cell that indicates a TCI activation.

29. The method of claim 28, wherein the downlink transmission comprises at least one of a tracking reference signal (TRS), channel state information reference signal (CSI-RS), or physical downlink control channel (PDCCH).

30. A method for wireless communications by a network entity, comprising: transmitting, to a user equipment (UE), a command to switch from a current cell to a new cell signaled via physical layer or medium access control (MAC) layer signaling; determining an initial beam for the UE to use for at least one of uplink or downlink transmissions in the new cell before the UE receives a transmission configuration indicator (TCI) activation or configuration command; and communicating with the UE in the new cell using the initial beam.

31. The method of claim 30, wherein the command is signaled via a downlink control information (DCI) or medium access control (MAC) control element (MAC CE).

32. The method of claim 30, wherein the initial beam is determined based on a reference signal (RS) ID indicated in the command.

33. The method of claim 30, wherein the initial beam is determined based on a latest physical layer metric report generated by the UE prior to receiving the command to switch from the current cell to the new cell.

34. The method of claim 30, wherein the initial beam is determined based on an implicit indication of a best reported reference signal in a latest physical layer metric report generated by the UE prior to receiving the command to switch from the current cell to the new cell.

35. The method of claim 30, wherein the UE stops using the initial beam after receiving a TCI activation command.

36. The method of claim 35, wherein: the UE uses the initial beam for processing at least one of a physical downlink control channel (PDCCH) or a physical downlink shared channel (PDSCH); and stops using the initial beam after receiving any TCI activation or configuration command for PDCCH or PDSCH in the new cell.

37. The method of claim 30, wherein the UE stops using the initial beam after receiving a certain type of downlink transmission in the new cell that indicates a TCI activation.

38. The method of claim 37, wherein the downlink transmission comprises at least one of a tracking reference signal (TRS), channel state information reference signal (CSI-RS), or physical downlink control channel (PDCCH).

39. A method for wireless communications by a user equipment (UE), comprising: receiving a command, signaled via physical layer or medium access control (MAC) layer signaling, that indicates at least one of: at least one cell or at least one physical cell ID (PCI) to serve the UE; determining a default beam for a physical downlink shared channel (PDSCH) transmission in the indicated cell or PCI cell; and communicating in the new cell using the default beam.

40. The method of claim 39, wherein the UE is configured to use the default beam if the PDSCH transmission is scheduled within a threshold scheduling period by a downlink control information (DCI) that carries a corresponding transmission configuration indicator (TCI) state for the PDSCH transmission.

41. The method of claim 40, wherein the threshold scheduling period is at least one of configured or determined based on capability of the UE.

42. The method of claim 39, wherein the command switches the UE from a current PCI to a new PCI in a same serving cell.

43. The method of claim 42, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in an active downlink bandwidth part (BWP) of the new PCI.

44. The method of claim 42, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in a default downlink bandwidth part (BWP) of a default PCI.

45. The method of claim 44, further comprising receiving signaling indicating the default PCI.

46. The method of claim 45, wherein the received signaling comprises one of radio resource control (RRC) signaling, a medium access control (MAC) control element (CE) (MAC-CE), or a downlink control information (DCI).

47. The method of claim 39, wherein: the command configures the UE to be served by multiple PCIs; and the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in one or more active downlink bandwidth part (BWP) of one or more of the multiple PCIs.

48. The method of claim 47, further comprising receiving signaling indicating the one or more PCIs.

49. The method of claim 48, wherein the received signaling comprises one of radio resource control (RRC) signaling, a medium access control (MAC) control element (CE) (MAC-CE), or a downlink control information (DCI).

50. The method of claim 47, wherein: the CORESET is selected based on a lowest or highest value of a CORESET ID; and if more than one of the PCIs have a same lowest or highest CORESET ID, the one or more PCIs are determined based on a PCI index among the PCIs having the same lowest or highest CORESET ID.

51. The method of claim 39, wherein the command configures the UE to be served by one or more serving cells.

52. The method of claim 51, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in an active downlink bandwidth part (BWP) of one or more of the serving cells.

53. The method of claim 51, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in a default downlink bandwidth part (BWP) of a default serving cell.

54. The method of claim 53, further comprising receiving signaling indicating the default serving cell.

55. The method of claim 39, wherein: the command configures the UE to be served by multiple serving cells; and the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in one or more active downlink bandwidth part (BWP) of one or more of the multiple serving cells.

56. The method of claim 55, further comprising receiving signaling indicating the one or more serving cells.

57. The method of claim 55, wherein: the CORESET is selected based on a lowest or highest value of a CORESET ID; and if more than one of the serving cells have a same lowest or highest CORESET ID, the one or more serving cells are determined based on a serving cell ID among the serving cells having the same lowest or highest CORESET ID.

58. The method of claim 39, wherein, if no control resource set (CORESET) is configured for a downlink bandwidth part (BWP), the default beam is determined based on a spatial quasi colocation (QCL) reference signal of an active PDSCH transmission configuration indicator (TCI) state on the downlink BWP.

59. The method of claim 58, wherein the default beam is determined based on the spatial QCL reference signal of an active PDSCH TCI state with a lowest or highest TCI state ID.

60. A method for wireless communications by a network entity, comprising: transmitting, to a user equipment (UE), a command, signaled via physical layer or medium access control (MAC) layer signaling, that indicates at least one of: at least one cell or at least one physical cell ID (PCI) to serve the UE; determining a default beam for the UE for a physical downlink shared channel (PDSCH) transmission in the indicated cell or PCI cell; and communicating with the UE in the new cell using the default beam.

61. The method of claim 60, wherein the UE is configured to use the default beam if the PDSCH transmission is scheduled within a threshold scheduling period by a downlink control information (DCI) that carries a corresponding transmission configuration indicator (TCI) state for the PDSCH transmission.

62. The method of claim 61, wherein the threshold scheduling period is at least one of configured or determined based on capability of the UE.

63. The method of claim 60, wherein the command switches the UE from a current PCI to a new PCI in a same serving cell.

64. The method of claim 63, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in an active downlink bandwidth part (BWP) of the new PCI.

65. The method of claim 63, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in a default downlink bandwidth part (BWP) of a default PCI.

66. The method of claim 65, further comprising receiving signaling indicating the default PCI.

67. The method of claim 66, wherein the received signaling comprises one of radio resource control (RRC) signaling, a medium access control (MAC) control element (CE) (MAC-CE), or a downlink control information (DCI).

68. The method of claim 60, wherein: the command configures the UE to be served by multiple PCIs; and the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in one or more active downlink bandwidth part (BWP) of one or more of the multiple PCIs.

69. The method of claim 68, further comprising receiving signaling indicating the one or more PCIs.

70. The method of claim 69, wherein the received signaling comprises one of radio resource control (RRC) signaling, a medium access control (MAC) control element (CE) (MAC-CE), or a downlink control information (DCI).

71. The method of claim 68, wherein: the CORESET is selected based on a lowest or highest value of a CORESET ID; and if more than one of the PCIs have a same lowest or highest CORESET ID, the one or more PCIs are determined based on a PCI index among the PCIs having the same lowest or highest CORESET ID.

72. The method of claim 60, wherein the command configures the UE to be served by one or more serving cells.

73. The method of claim 72, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in an active downlink bandwidth part (BWP) of one or more of the serving cells.

74. The method of claim 72, wherein the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in a default downlink bandwidth part (BWP) of a default serving cell.

75. The method of claim 74, further comprising receiving signaling indicating the default serving cell.

76. The method of claim 60, wherein: the command configures the UE to be served by multiple serving cells; and the default beam is determined based on a quasi-colocation (QCL) assumption for a control resource set (CORESET) in one or more active downlink bandwidth part (BWP) of one or more of the multiple serving cells.

77. The method of claim 76, further comprising receiving signaling indicating the one or more serving cells.

78. The method of claim 76, wherein: the CORESET is selected based on a lowest or highest value of a CORESET ID; and if more than one of the serving cells have a same lowest or highest CORESET ID, the one or more serving cells are determined based on a serving cell ID among the serving cells having the same lowest or highest CORESET ID.

79. The method of claim 60, wherein, if no control resource set (CORESET) is configured for a downlink bandwidth part (BWP), the default beam is determined based on a spatial quasi colocation (QCL) reference signal of an active PDSCH transmission configuration indicator (TCI) state on the downlink BWP.

80. The method of claim 79, wherein the default beam is determined based on the spatial QCL reference signal of an active PDSCH TCI state with a lowest or highest TCI state ID.

81. The method of claim 47, wherein the CORESET is selected based on a lowest CORESET ID in a latest slot in a monitored search space or CORESET.

82. The method of claim 55, wherein the CORESET is selected based on a lowest CORESET ID in a latest slot in a monitored search space or CORESET.

83. The method of claim 60, further comprising: determining a default uplink beam based on a received reference signal used to determine a default PDSCH beam per PCI.

84. The method of claim 83, wherein the default uplink beam comprises a default beam for a physical uplink control channel (PUCCH) or a sounding reference signal (SRS) transmission if uplink beam indication is not configured or indicated by a base station.

85. The method of claim 83, wherein the reference signal used to determine the default PDSCH beam is used as a pathloss reference signal to measure pathloss for determining uplink transmission power.

86. The method of claim 83, wherein the default uplink beam comprises a default beam for a physical uplink shared channel (PUSCH) when the PUSCH is scheduled by a particular DCI format but no PUCCH with a configured spatial relation is configured in an active uplink BWP.

87. The method of claim 68, wherein the CORESET is selected based on a lowest CORESET ID in a latest slot in a monitored search space or CORESET.

88. The method of claim 76, wherein the CORESET is selected based on a lowest CORESET ID in a latest slot in a monitored search space or CORESET.

89. The method of claim 68, further comprising: determining a default uplink beam based on a received reference signal used to determine a default PDSCH beam per PCI.

90. The method of claim 89, wherein the default uplink beam comprises a default beam for a physical uplink control channel (PUCCH) or a sounding reference signal (SRS) transmission if uplink beam indication is not configured or indicated by a base station.

91. The method of claim 89, wherein the default uplink beam comprises a default beam for a physical uplink shared channel (PUSCH) when the PUSCH is scheduled by a particular DCI format and no PUCCH with a configured spatial relation is configured in an active uplink BWP.

92. The method of claim 89, wherein the reference signal used to determine the default PDSCH beam is used as a pathloss reference signal to measure pathloss for determining uplink transmission power.