UE-assisted transitions to secondary cells via beam failure recovery

Abstract

This disclosure provides systems, methods, and apparatus, including computer programs encoded on a computer storage medium, for handover of a secondary cell to a primary cell. A user equipment (UE) monitors a first radio condition of the UE for a beam of a primary cell and a second radio condition for beams of one or more secondary cells configured for the UE in carrier aggregation. In response to the first radio condition not satisfying a first threshold and a second radio condition for at least one candidate secondary cell satisfying a second threshold, the UE sends a request to configure the at least one candidate secondary cell as a candidate beam of a new primary cell. The base station determines to reconfigure the at least one secondary cell as the new primary cell. The base station and the UE perform a transition of the UE to the new primary cell.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. non-provisional patent application No. 17 / 934,838, filed on September 23, 2022, entitled “UE ASSISTED HANDOVER TO SECONDARY CELL VIA BEAM FAILURE RECOVERY,” which is expressly incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to wireless communications including user equipment (UE) assisted transition to a secondary cell (SCell) via a beam failure recovery (BFR) mechanism. Background Art

[0004] Wireless communication systems are widely deployed to provide a variety of telecommunication services, such as telephony, video, data, messaging, and broadcast. Typical wireless communication systems may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

[0005] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at a city, country, region, and even global level. An example telecommunication standard is 5G New Radio (NR). 5G NR is part of the continuous mobile broadband evolution promulgated by the Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability, such as with the Internet of Things (IoT), and other requirements. 5G NR includes services associated with enhanced mobile broadband (eMBB), massive machine type communications (mMTC), and ultra-reliable low latency communications (URLLC). Certain aspects of 5G NR may be based on the 4G Long Term Evolution (LTE) standard. Summary of the invention

[0006] The systems, methods and devices of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.

[0007] In some aspects, the technology described herein relates to a method for wireless communication of a user equipment (UE), the method comprising monitoring a first radio condition of the UE for a beam of a primary cell and a second radio condition for a beam of one or more secondary cells configured for the UE in carrier aggregation. The method comprises, in response to the first radio condition not satisfying a first threshold and the second radio condition for at least one candidate secondary cell of the one or more secondary cells satisfying a second threshold, sending a request to configure the at least one candidate secondary cell as a candidate beam of a new primary cell. The method comprises performing a transition to the new primary cell.

[0008] The present disclosure also provides a device (e.g., UE) comprising a memory storing computer-executable instructions and at least one processor configured to execute these computer-executable instructions to perform the above method, a device comprising components for executing the above method, and a non-transitory computer-readable medium storing computer-executable instructions for executing the above method.

[0009] An innovative aspect of the subject matter described in the present disclosure may be implemented in a method for wireless communication of a base station (BS), the method comprising configuring a primary cell and one or more secondary cells for a user equipment (UE) in carrier aggregation. The method comprises receiving a request to configure at least one candidate secondary cell of the one or more secondary cells as a candidate beam of a new primary cell, wherein the request indicates that a first radio condition of the UE for a beam of the primary cell does not satisfy a first threshold and a second radio condition of a candidate beam of the at least one candidate secondary cell satisfies a second threshold. The method comprises switching the UE to the new primary cell.

[0010] The present disclosure also provides a device (e.g., a BS) comprising a memory storing computer-executable instructions and at least one processor configured to execute these computer-executable instructions to perform the above method, a device comprising components for executing the above method, and a non-transitory computer-readable medium storing computer-executable instructions for executing the above method.

[0011] Details of one or more specific implementations of the subject matter described in the present disclosure are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will become apparent from the specification, drawings, and claims. Note that the relative sizes of the following drawings may not be drawn to scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a diagram illustrating an example of a wireless communication system and an access network.

[0013] Figure 2A is a diagram illustrating an example of the first frame.

[0014] Figure 2B is a diagram illustrating an example of a DL channel within a subframe.

[0015] Figure 2C is a diagram illustrating an example of the second frame.

[0016] Figure 2D is a diagram illustrating an example of a subframe.

[0017] Figure 3 is a diagram illustrating an example of a base station (BS) and a user equipment (UE) in an access network.

[0018] Figure 4 A diagram illustrating an example decomposed base station architecture is shown.

[0019] Figure 5 is a diagram illustrating an example of a beam failure detection process.

[0020] Figure 6 is a diagram illustrating an example process for fast recovery in a dual connectivity scenario.

[0021] Figure 7 is a diagram illustrating an example procedure for switching a secondary cell (SCell) to a new primary cell (PCell).

[0022] Figure 8 is a logic flow diagram of an example process for switching to an SCell in response to beam failure of a PCell.

[0023] Fig. 9 is a logic flow diagram of an example process for an SCell switching process.

[0024] Fig.10 is a diagram of an example medium access control (MAC) control element (CE) for indicating suitable SCell candidates for SCell switching.

[0025] Fig.11 is a message diagram illustrating example messages between a base station and a UE.

[0026] Fig.12 is a conceptual data flow diagram illustrating the flow of data between different elements / components in an example base station.

[0027] Fig.13 is a conceptual data flow diagram illustrating the data flow between different parts / components in an example UE.

[0028] Fig.14 is a flow chart of an example method for a UE to perform beam failure detection using beam failure prediction.

[0029] Fig.15is a flow chart of an example method for a base station to control beam failure prediction at a UE.

[0030] The same reference numbers and designations in different drawings represent the same elements. DETAILED DESCRIPTION

[0031] For the purpose of describing the innovative aspects of the present disclosure, the following description refers to certain specific implementations. However, one of ordinary skill in the art will readily recognize that the teachings herein can be applied in a variety of different ways. Some examples in the present disclosure are based on wireless and wired local area network (LAN) communications in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.11 wireless standards, the IEEE 802.3 Ethernet standards, and the IEEE 1901 Power Line Communication (PLC) standards. However, the specific implementations described can be implemented in any device, system, or network capable of sending and receiving RF signals in accordance with any of the following wireless communication standards: including any of the IEEE 802.11 standards, Standard, Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Global System for Mobile Communications (GSM), GSM / General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband CDMA (W-CDMA), Evolution-Data Optimized (EV-DO), 1xEV-DO, EV-DO Revision A, EV-DO Revision B, High Speed ​​Packet Access (HSPA), High Speed ​​Downlink Packet Access (HSDPA), High Speed ​​Uplink Packet Access (HSUPA), Evolved High Speed ​​Packet Access (HSPA+), Long Term Evolution (LTE), AMPS or other known signals for communication within a wireless network, cellular network or Internet of Things (IoT) network, such as a system utilizing 3G, 4G or 5G or further implementations thereof.

[0032] In wireless communications, beamforming can be used to compensate for power loss in communications between a transmitter and a receiver. For example, in millimeter wave (mmW or mmWave) communications, the frequency may be relatively high and the signal attenuation may be relatively large compared to conventional communication channels. However, due to the uncertainty of the wireless environment and unexpected blockages, the beam may be prone to beam failure. The 5G system may implement a beam failure detection (BFD) process to assist in maintaining a strong channel connection between the user equipment (UE) and the base station. In the BFD process, the UE may be configured with rules for determining whether a beam failure has occurred based on physical layer measurements of a beam failure detection reference signal (BFD-RS). For example, the UE may count the number of beam failure instances during a measurement window. If the number of beam failure instances during the measurement window meets a threshold, the UE may declare a beam failure.

[0033] In the case of beam failure, a beam failure recovery (BFR) procedure may be used in some cases. For example, the UE may measure the candidate beams of the primary cell (PCell) to determine whether one of the candidate beams will be suitable to maintain a link with the PCell. If the UE reports a suitable beam, the network may update the beam of the PCell.

[0034] An alternative to the BFR process is a transition to a neighboring cell. The UE may be configured with measurement objects for neighboring cells. The UE may measure the quality of neighboring cells and may provide a report to the network. In some cases, the report may be triggered by a condition based on the quality of the neighboring cell and / or PCell. For example, if the quality of the PCell decreases or the quality of the neighboring cell becomes better than the PCell, the UE may report the relevant quality and the network may initiate a transition of the UE to a neighboring cell.

[0035] In another alternative, for a dual connectivity scenario where the UE is connected to a primary cell group (MCG) including a PCell and a second cell group (SCG) including a primary SCG cell (PSCell), the UE may use a fast recovery procedure to forward MCG failure information to the base station via SCG RRC signaling. The MCG may utilize SCG RRC signaling to deliver a radio resource control (RRC) reconfiguration message to the UE. SCG RRC signaling may be used to transition the UE to the SCG.

[0036] For UEs operating with carrier aggregation (CA) but without SCG, the UE may be connected to one or more secondary cells. However, in the event of a beam failure on the PCell, the above techniques may not allow the UE to switch to one of the secondary cells. For example, although the BFD process may also be applied to secondary cells, such a process may result in a change in the beam used for the secondary cell, but the secondary cell does not become the primary cell. Similarly, the secondary cell may not be considered an adjacent cell and may not be configured with a corresponding measurement object. Therefore, in the event of a beam failure on the PCell, the UE may not provide measurements of the SCell, and the SCell will not be selected for switching. Finally, in the absence of SCG, the MCG fast recovery process is not applicable. In view of the foregoing, when a beam failure occurs on the primary cell, a UE operating without SCG may experience a radio link failure (RLF). The RLF recovery process includes suspending ongoing communications until the UE resynchronizes with the network.

[0037] In one aspect, the present disclosure provides a technique for assisting a UE in transitioning from a PCell to an SCell in the event of a beam failure on a PCell. For example, when there is no suitable alternative beam for the PCell and there is no suitable neighboring cell, the UE may request a transition to a suitable SCell that can be reconfigured as a new PCell. For example, the UE may send a request for SCell switching as a medium access control (MAC) control element (CE) or an RRC message. The request may identify one or more candidate SCell beams suitable for the PCell. The base station may determine to reconfigure one of the candidate SCells as a new PCell. The base station may use an RRC reconfiguration message to initiate a UE transition to the PCell. Therefore, in the event of a beam failure, the UE may transition to the SCell.

[0038] Certain implementations of the subject matter described in this disclosure may be implemented to achieve one or more of the following potential advantages. UE-assisted transition to a secondary cell may prevent RLF and allow the UE to continue ongoing communications. In some implementations, signaling a request via MAC-CE may be faster than an RRC procedure.

[0039] Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as "elements"). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0040] As an example, an element, or any part of an element, or any combination of elements can be implemented as a "processing system", which includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on chip (SoCs), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gating logic, discrete hardware circuits, and other suitable hardware configured to perform various functionalities described throughout the present disclosure. The processor may include an interface or be coupled to an interface that can obtain or output a signal. The processor may obtain a signal via an interface and output a signal via an interface. In some specific implementations, the interface may be a printed circuit board (PCB) transmission line. In some other specific implementations, the interface may include a wireless transmitter, a wireless transceiver, or a combination thereof. For example, the interface may include a radio frequency (RF) transceiver, which may be implemented to receive or transmit a signal, or both. One or more processors in a processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subroutines, software components, 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.

[0041] Therefore, in one or more example implementations, the functions described herein may be implemented with hardware, software, or any combination thereof. If implemented in software, the functions may be stored or encoded on a computer-readable medium as one or more instructions or codes. Computer-readable media include computer storage media, which may be referred to as non-transitory computer-readable media. Non-transitory computer-readable media may not include transient signals. The storage medium may be any available medium that can be accessed by a computer. By way of example and not limitation, such computer-readable media may include random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, a combination of the aforementioned types of computer-readable media, or any other medium that can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer.

[0042] Figure 11 is a diagram illustrating an example of a wireless communication system and an access network 100. The wireless communication system (also referred to as a wireless wide area network (WWAN)) includes a base station 102, a UE 104, a relay device 105, an evolved packet core (EPC) 160, and another core network 190 (such as a 5G core (5GC)). The base station 102 may include a macro cell (a high-power cellular base station) or a small cell (a low-power cellular base station). The macro cell includes a base station. The small cell includes a femto cell, a pico cell, and a micro cell. The small cell includes a femto cell, a pico cell, and a micro cell. The base station 102 may be configured as a decomposed RAN (D-RAN) or an open RAN (O-RAN) architecture, in which functionality is split between multiple units (such as a central unit (CU), one or more distributed units (DUs), or radio units (RUs)). Such an architecture may be configured to utilize a protocol stack that is logically split between one or more units (such as one or more CUs and one or more DUs). In some aspects, a CU may be implemented within an edge RAN node, and in some aspects, one or more DUs may be co-located with a CU, or may be geographically distributed in one or more RAN nodes. A DU may be implemented to communicate with one or more RUs. Each of the CU, DU, and RU may also be implemented as a virtual unit, namely a virtual central unit (VCU), a virtual distributed unit (VDU), or a virtual radio unit (VRU).

[0043] Base station type operations or network designs may take into account the aggregated nature of base station functionality. For example, a disaggregated base station may be used in an integrated access backhaul (IAB) network, an open radio access network (O-RAN (network configurations such as those initiated by the O-RAN Alliance)), or a virtualized radio access network (vRAN, also known as a cloud radio access network (C-RAN)). Decomposition may include distributing functionality across two or more units at various physical locations, as well as virtually distributing functionality of at least one unit, which may enable flexibility in network design. Various units of a disaggregated base station or disaggregated RAN architecture may be configured for wired or wireless communication with at least one other unit.

[0044] In some implementations, one or more of the receiving devices, such as the UE 104, may include an SCell switching component 140 configured to perform an SCell switching process. The SCell switching component 140 may include a monitoring component 142 configured to monitor a first radio condition of the UE for a beam of a primary cell and a second radio condition for a beam of one or more secondary cells configured for the UE in carrier aggregation. The SCell switching component 140 may include a switching request component 144 configured to send a request to configure the at least one candidate secondary cell as a candidate beam of a new primary cell in response to the first radio condition not satisfying a first threshold and the second radio condition for at least one candidate secondary cell of the one or more secondary cells satisfying a second threshold. The SCell switching component 140 may include a transition component 146 configured to perform a transition to a new primary cell.

[0045] In some specific implementations, one or more of the base stations 102 may include an SCell control component 120, which is configured to control SCell switching for the UE. The SCell control component 120 may include a configuration component 122, which is configured to configure a primary cell and one or more secondary cells for the UE in carrier aggregation. The SCell control component 120 may include a switching component 124, which is configured to receive a request to configure at least one candidate secondary cell of the one or more secondary cells as a candidate beam of a new primary cell. For example, the request may indicate that a first radio condition of the UE for a beam of the primary cell does not meet a first threshold and a second radio condition of a candidate beam of the at least one candidate secondary cell meets a second threshold. The SCell control component 120 may include a reconfiguration component 126, which is configured to switch the UE to a new primary cell.

[0046] The base station 102 configured for 4G LTE (collectively referred to as the Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) can interface with the EPC 160 via a first backhaul link 132 (such as an S1 interface), which can be wired or wireless. The base station 102 configured for 5G NR (collectively referred to as the Next Generation RAN (NG-RAN)) can interact with the core network 190 via a second backhaul link 184, which can be wired or wireless. The base station 102 may perform, among other functions, one or more of the following functions: transmission of user data, radio channel encryption and decryption, integrity protection, header compression, mobility control functions (such as switching, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution of non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment tracking, RAN information management (RIM), paging, positioning, and delivery of warning messages. The base stations 102 may communicate with each other directly or indirectly (such as through the EPC 160 or the core network 190) on a third backhaul link 134 (such as an X2 interface). The third backhaul link 134 may be wired or wireless.

[0047] Base station 102 can communicate wirelessly with UE 104. Each of base stations 102 can provide communication coverage for a corresponding geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, a small cell 102' may have a coverage area 110' that overlaps with the coverage area 110 of one or more macro base stations 102. A network including both small cells and macro cells may be referred to as a heterogeneous network. A heterogeneous network may also include a home evolved B node (eNB) (HeNB), which may provide services to a restricted group called a closed subscriber group (CSG). A communication link 112 between base station 102 and UE 104 may include UL (also referred to as a reverse link) transmission from UE 104 to base station 102 or DL ​​(also referred to as a forward link) transmission from base station 102 to UE 104. The communication link 112 may use multiple input multiple output (MIMO) antenna technology, including spatial multiplexing, beamforming, or transmit diversity. The communication link may be through one or more carriers. For each carrier allocated in a carrier aggregation of up to Yx MHz (x component carriers) for transmission in each direction, the base station 102 / UE 104 may use a spectrum of up to Y MHz (such as 5 MHz, 10 MHz, 15 MHz, 20 MHz, 100 MHz, 400 MHz, etc.) bandwidth. These carriers may or may not be adjacent to each other. The allocation of carriers may be asymmetric with respect to DL and UL (such as, more or fewer carriers may be allocated for DL ​​compared to UL). The component carrier may include a primary component carrier and one or more secondary component carriers. The primary component carrier may be referred to as a primary cell (PCell) and the secondary component carrier may be referred to as a secondary cell (SCell).

[0048] Some UEs 104 may communicate with each other using a device-to-device (D2D) communication link 158. The D2D communication link 158 may use DL / UL WWAN spectrum. The D2D communication link 158 may use one or more sidelink channels, such as a physical sidelink broadcast channel (PSBCH), a physical sidelink discovery channel (PSDCH), a physical sidelink shared channel (PSSCH), and a physical sidelink control channel (PSCCH). The D2D communication may be through various wireless D2D communication systems, such as, for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on IEEE 802.11 standards, LTE, or NR.

[0049] The wireless communication system may also include a Wi-Fi access point (AP) 150 that communicates with a Wi-Fi station (STA) 152 via a communication link 154 in the 5 GHz unlicensed spectrum. When communicating in the unlicensed spectrum, the STA 152 / AP 150 may perform a clear channel assessment (CCA) to determine whether the channel is available prior to communication.

[0050] The small cell 102' may operate in a licensed or unlicensed spectrum. When operating in an unlicensed spectrum, the small cell 102' may employ NR and use the same 5 GHz unlicensed spectrum as the 5 GHz unlicensed spectrum used by the Wi-Fi AP 150. The small cell 102' employing NR in the unlicensed spectrum may boost coverage of the access network or increase capacity of the access network.

[0051] Whether a small cell 102' or a large cell (such as a macro base station), the base station 102 may include an eNB, a gNodeB (gNB), or other types of base stations. Some base stations (such as gNB 180) may operate in one or more frequency bands within the electromagnetic spectrum.

[0052] The electromagnetic spectrum is typically subdivided into various categories, bands, channels, etc. based on frequency / wavelength. In 5GNR, two initial operating bands have been identified as frequency range designations FR1 (410MHz–7.125GHz) and FR2 (24.25GHz–52.6GHz). Frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Although a portion of FR1 is greater than 6GHz, FR1 is often (interchangeably) referred to as the “below 6GHz” band in various documents and articles. FR2 sometimes presents a similar naming issue, although it is different from the extremely high frequency (EHF) band (30GHz to 300GHz) identified as the “millimeter wave” (mmW) band by the International Telecommunication Union (ITU), but it is often (interchangeably) referred to as the “millimeter wave” band in various documents and articles.

[0053] In view of the above aspects, unless otherwise specifically stated, it should be understood that if used in this document, the term "below 6 GHz" or the like can broadly represent frequencies that can be less than 6 GHz, can be within FR1, or can include mid-band frequencies. In addition, unless otherwise specifically stated, it should be understood that if the term "millimeter wave" or the like is used in this document, it can broadly represent frequencies that can include mid-band frequencies, can be within FR2, or can be within the EHF band. Communications using mmW radio frequency bands have extremely high path loss and short range. The mmW base station 180 can utilize beamforming 182 with the UE 104 to compensate for this path loss and short range.

[0054] The EPC 160 may include a mobility management entity (MME) 162, other MMEs 164, a serving gateway 166, a multimedia broadcast multicast service (MBMS) gateway 168, a broadcast multicast service center (BM-SC) 170, and a packet data network (PDN) gateway 172. The MME 162 may communicate with a home subscriber server (HSS) 174. The MME 162 is a control node that handles signaling between the UE 104 and the EPC 160. Generally speaking, the MME 162 provides bearer and connection management. All user Internet Protocol (IP) packets are passed through the serving gateway 166, which itself is connected to the PDN gateway 172. The PDN gateway 172 provides UE IP address allocation and other functions. The PDN gateway 172 and the BM-SC 170 are connected to IP services 176. The IP services 176 may include the Internet, an intranet, an IP multimedia subsystem (IMS), a PS streaming service, or other IP services. The BM-SC 170 may provide functions for MBMS user service configuration and delivery. BM-SC 170 may serve as an entry point for content provider MBMS delivery, may be used to authorize and initiate MBMS bearer services in a public land mobile network (PLMN), and may be used to schedule MBMS delivery. MBMS gateway 168 may be used to distribute MBMS services to base stations 102 belonging to a multicast broadcast single frequency network (MBSFN) area of ​​a broadcast specific service, and may be responsible for session management (start / stop) and for collecting eMBMS related billing information.

[0055] The core network 190 may include an access and mobility management function (AMF) 192, other AMFs 193, a session management function (SMF) 194, and a user plane function (UPF) 195. The AMF 192 may communicate with a unified data management (UDM) 196. The AMF 192 is a control node that handles signaling between the UE 104 and the core network 190. Generally speaking, the AMF 192 provides QoS flow and session management. All user Internet Protocol (IP) packets are passed through the UPF 195. The UPF 195 provides UE IP address allocation and other functions. The UPF 195 is connected to an IP service 197. The IP service 197 may include the Internet, an intranet, an IP multimedia subsystem (IMS), a PS streaming service, or other IP services.

[0056] A base station may include or be referred to as a gNB, a Node B, an eNB, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), a transmit receive point (TRP), or some other appropriate term. A base station 102 provides an access point to an EPC 160 or a core network 190 for a UE 104. Examples of a UE 104 include a cellular phone, a smart phone, a Session Initiation Protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (such as an MP3 player), a camera, a game console, a tablet computer, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small kitchen appliance, a healthcare device, an implant, a sensor / actuator, a display, or any other similarly functional device. Some UEs 104 may be referred to as IoT devices (such as parking meters, gas pumps, ovens, vehicles, heart monitors, etc.). UE 104 may also be referred to as a station, a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

[0057] Although the following description may focus on 5G NR, the concepts described herein may be applicable to other similar areas such as LTE, LTE-A, CDMA, GSM and other wireless technologies, including future 6G technologies.

[0058] Figure 2A is a diagram 200 illustrating an example of a first frame. Figure 2B is a diagram 230 illustrating an example of a DL channel within a subframe. Figure 2C is a diagram 250 illustrating an example of a second frame. Figure 2D 280 is a diagram illustrating an example of a subframe. The 5G NR frame structure may be FDD, where for a particular set of subcarriers (carrier system bandwidth), subframes within that subcarrier set are dedicated to either DL or UL, or may be TDD, where for a particular set of subcarriers (carrier system bandwidth), subframes within that subcarrier set are dedicated to both DL and UL. A subset of the total cell bandwidth of a cell is referred to as a bandwidth part (BWP), and bandwidth adaptation is achieved by configuring the UE with a BWP and informing the UE which of the configured BWPs is currently the active BWP.

[0059] exist Figure 2A , Figure 2CIn the example provided, the 5G NR frame structure is assumed to be TDD, where subframe 4 is configured with slot format 28 (most of which are DL), where D is DL, U is UL, and X can be used flexibly between DL / UL, and subframe 3 is configured with slot format 34 (most of which are UL). Although subframes 3 and 4 are shown as having slot formats 34 and 28, respectively, any particular subframe can be configured with any of the various available slot formats 0-61. Slot formats 0 and 1 are full DL and full UL, respectively. Other slot formats 2-61 include a mix of DL, UL and flexible symbols. The UE is configured with the slot format through the received slot format indicator (SFI) (dynamically configured through DL control information (DCI) or semi-statically / statically configured through radio resource control (RRC) signaling). Note that the following description also applies to the 5G NR frame structure as TDD.

[0060] Other wireless communication technologies may have different frame structures or different channels. A frame (10 milliseconds (ms)) may be divided into 10 equally sized subframes (1ms). Each subframe may include one or more time slots. A subframe may also include mini-time slots, which may include 7, 4, or 2 symbols. Each time slot may include 7 or 14 symbols, depending on the time slot configuration. For time slot configuration 0, each time slot may include 14 symbols, and for time slot configuration 1, each time slot may include 7 symbols. The symbols on the DL may be cyclic prefix (CP) OFDM (CP-OFDM) symbols. The symbols on the UL may be CP-OFDM symbols (for high throughput scenarios) or discrete Fourier transform (DFT) spread OFDM (DFT-s-OFDM) symbols (also known as single carrier frequency division multiple access (SC-FDMA) symbols) (for power-limited scenarios; limited to single stream transmission). The number of time slots in a subframe is based on the time slot configuration and parameter set (numerology). For slot configuration 0, different parameter sets μ0 to 5 allow 1, 2, 4, 8, 16, and 32 slots per subframe, respectively. For slot configuration 1, different parameter sets 0 to 2 allow 2, 4, and 8 slots per subframe, respectively. Accordingly, for slot configuration 0 and parameter set μ, there are 14 symbols per slot and 2 per subframe. μ time slots. The subcarrier spacing and symbol length / duration are functions of the parameter set. The subcarrier spacing can be equal to 2 μ *15kHz, where μ is parameter set 0 to 5. Therefore, the subcarrier spacing for parameter set μ=0 is 15kHz, and the subcarrier spacing for parameter set μ=5 is 480kHz. The symbol length / duration is inversely related to the subcarrier spacing. FIG. 2A to FIG. 2DAn example is provided for slot configuration 0 with 14 symbols per slot and parameter set μ=2 with 4 slots per subframe. The slot duration is 0.25 ms, the subcarrier spacing is 60 kHz, and the symbol duration is approximately 16.67 microseconds (μs).

[0061] A resource grid may be used to represent the frame structure. Each slot includes a resource block (RB) (also referred to as a physical RB (PRB)) extending over 12 consecutive subcarriers. The resource grid is divided into a plurality of resource elements (REs). The number of bits carried by each RE depends on the modulation scheme.

[0062] like Figure 2A As illustrated, some of the REs carry reference (pilot) signals (RS) for the UE. The RS may include a demodulation RS (DM-RS) for channel estimation at the UE (indicated as R for a particular configuration). x , where 100x is the port number, but other DM-RS configurations are possible) and a channel state information reference signal (CSI-RS). RS may also include a beam measurement RS (BRS), a beam refinement RS (BRRS), and a phase tracking RS (PT-RS).

[0063] Figure 2B Examples of various DL channels within a subframe of a frame are illustrated. The physical downlink control channel (PDCCH) carries DCI within one or more control channel elements (CCEs), each CCE including nine RE groups (REGs), each REG including four consecutive REs in an OFDM symbol. The primary synchronization signal (PSS) may be within symbol 2 of a specific subframe of the frame. The PSS is used by UE 104 to determine subframe / symbol timing and physical layer identification. The secondary synchronization signal (SSS) may be within symbol 4 of a specific subframe of the frame. The SSS is used by the UE to determine the physical layer cell identification group number and radio frame timing. Based on the physical layer identification and the physical layer cell identification group number, the UE may determine the physical cell identifier (PCI). Based on the PCI, the UE may determine the location of the aforementioned DM-RS. The physical broadcast channel (PBCH) carrying the master information block (MIB) may be logically grouped with the PSS and SSS to form a synchronization signal (SS) / PBCH block (SSB). The MIB provides the system frame number (SFN) and the number of RBs in the system bandwidth. The Physical Downlink Shared Channel (PDSCH) carries user data, broadcast system information not sent through the PBCH (such as System Information Blocks (SIBs)), and paging messages.

[0064] like Figure 2CAs illustrated, some of the REs carry DM-RS for channel estimation at the base station (which is indicated as R for one specific configuration, but other DM-RS configurations are possible). The UE may send DM-RS for a physical uplink control channel (PUCCH) and DM-RS for a physical uplink shared channel (PUSCH). The PUSCH DM-RS may be sent in the first one or the first two symbols of the PUSCH. The PUCCH DM-RS may be sent in different configurations depending on whether a short or long PUCCH is sent and depending on the specific PUCCH format used.

[0065] The UE may send a sounding reference signal (SRS). The SRS resource set configuration may define the resources used for SRS transmission. For example, as illustrated in the figure, the SRS configuration may specify that the SRS may be sent in the last symbol of a subframe. The SRS may have a comb structure, and the UE may send the SRS on one comb for each SRS port. The SRS may be used by the base station for channel quality estimation to achieve frequency-dependent scheduling for UL. The SRS may also be used for channel estimation to select a pre-decoder for downlink MIMO.

[0066] Figure 2D Examples of various UL channels within a subframe of a frame are illustrated. The PUCCH may be located at a position as indicated in one configuration. The PUCCH carries uplink control information (UCI), such as scheduling requests, channel quality indicator (CQI), precoding matrix indicator (PMI), rank indicator (RI), and HARQ ACK / NACK feedback. The PUSCH carries data, and may additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), or UCI.

[0067] Figure 31 is a diagram of an example of a base station 102 and a UE 104 in an access network. UE 104 may be an example of a receiving device. In the DL, IP packets from EPC 160 may be provided to controller / processor 375. Controller / processor 375 implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a service data adaptation protocol (SDAP) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller / processor 375 provides RRC layer functionality associated with broadcasting of system information (such as MIB, SIB), RRC connection control (such as RRC connection paging, RRC connection establishment, RRC connection modification and RRC connection release), inter-radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functionality associated with header compression / decompression, security (encryption, decryption, integrity protection, integrity verification) and conversion support functions; RLC layer functionality associated with transfer of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling and logical channel prioritization.

[0068] The transmit (Tx) processor 316 and receive (Rx) processor 370 implement layer 1 functionality associated with various signal processing functions. Layer 1 (which includes the physical (PHY) layer) may include error detection on the transmission channel, forward error correction (FEC) decoding / decoding of the transmission channel, interleaving, rate matching, mapping to the physical channel, modulation / demodulation of the physical channel, and MIMO antenna processing. The Tx processor 316 handles the mapping to the signal constellation based on various modulation schemes (such as binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-phase shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated codewords can be split into parallel streams. Each stream can be mapped to an OFDM subcarrier, multiplexed with a reference signal (such as a pilot) in the time domain or frequency domain, and combined together using an inverse fast Fourier transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially pre-coded to produce multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine coding and modulation schemes, as well as for spatial processing. The channel estimate may be derived from a reference signal or channel condition feedback sent by the UE 104. Each spatial stream may be provided to a different antenna 320 via a separate transmitter 318Tx. Each transmitter 318Tx may modulate an RF carrier with a corresponding spatial stream for transmission.

[0069] At the UE 104, each receiver 354Rx receives a signal through its corresponding antenna 352. Each receiver 354Rx recovers the information modulated onto the RF carrier and provides the information to a receive (Rx) processor 356. The Tx processor 368 and the Rx processor 356 implement layer 1 functionality associated with various signal processing functions. The Rx processor 356 can perform spatial processing on the information to recover any spatial stream destined for the UE 104. If multiple spatial streams are destined for the UE 104, they can be combined into a single OFDM symbol stream by the Rx processor 356. The Rx processor 356 transforms the OFDM symbol stream from the time domain to the frequency domain using a fast Fourier transform (FFT). The frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier and the reference signal are recovered and demodulated by determining the most likely signal constellation point sent by the base station 102. These soft decisions can be based on channel estimates calculated by the channel estimator 358. These soft decisions are decoded and deinterleaved to recover the data and control signals originally sent on the physical channel by the base station 102. These data and control signals are provided to the controller / processor 359 which implements layer 3 and layer 2 functionality.

[0070] The controller / processor 359 may be associated with a memory 360 that stores program codes and data. The memory 360 may be referred to as a computer readable medium. In the UL, the controller / processor 359 provides demultiplexing between transport channels and logical channels, packet reassembly, decryption, header decompression, and control signal processing to recover IP packets from the EPC 160. The controller / processor 359 is also responsible for error detection using an ACK or NACK protocol to support HARQ operations.

[0071] Similar to the functionality described in conjunction with DL transmissions performed by the base station 102, the controller / processor 359 provides RRC layer functionality associated with system information (such as MIB, SIB) acquisition, RRC connection and measurement reporting; PDCP layer functionality associated with header compression / decompression and security (encryption, decryption, integrity protection, integrity verification); RLC layer functionality associated with delivery of upper layer PDUs, error correction through ARQ, concatenation, segmentation and reassembly of RLC SDUs, resegmentation of RLC data PDUs and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling and logical channel prioritization.

[0072] Channel estimates derived by the channel estimator 358 from a reference signal or feedback sent by the base station 102 may be used by the Tx processor 368 to select appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the Tx processor 368 may be provided to different antennas 352 via separate transmitters 354Tx. Each transmitter 354Tx may modulate an RF carrier with a corresponding spatial stream for transmission.

[0073] UL transmissions are processed at the base station 102 in a manner similar to that described in conjunction with the receiver functionality at the UE 104. Each receiver 318Rx receives a signal through its corresponding antenna 320. Each receiver 318Rx recovers information modulated onto an RF carrier and provides the information to an Rx processor 370.

[0074] The controller / processor 375 may be associated with a memory 376 that stores program codes and data. The memory 376 may be referred to as a computer readable medium. In the UL, the controller / processor 375 provides demultiplexing between transport channels and logical channels, packet reassembly, decryption, header decompression, control signal processing to recover IP packets from the UE 104. The IP packets from the controller / processor 375 may be provided to the EPC 160. The controller / processor 375 is also responsible for error detection using an ACK or NACK protocol to support HARQ operations.

[0075] At least one of the Tx processor 368, the Rx processor 356, and the controller / processor 359 may be configured to perform a combined Figure 1 For example, the memory 360 may include executable instructions defining the SCell switching component 140. The Tx processor 368, the Rx processor 356, and / or the controller / processor 359 may be configured to execute the SCell switching component 140.

[0076] At least one of the Tx processor 316, the Rx processor 370, and the controller / processor 375 may be configured to perform a combined Figure 1 For example, the memory 376 may include executable instructions that define the predictive control component 120. The Tx processor 316, the Rx processor 370, and / or the controller / processor 375 may be configured to execute the predictive control component 120.

[0077] Figure 4 A diagram illustrating an example decomposed base station 400 architecture is shown. The decomposed base station 400 architecture may include one or more central units (CUs) 410 that may communicate directly with a core network 420 via a backhaul link, or indirectly with the core network 420 through one or more decomposed base station units, such as a near real-time (near-RT) RAN intelligent controller (RIC) 425 via an E2 link, or a non-real-time (non-RT) RIC 415 associated with a service management and orchestration (SMO) framework 405, or both. The CU 410 may communicate with one or more distributed units (DUs) 430 via respective midhaul links, such as an F1 interface. The DU 430 may communicate with one or more radio units (RUs) 440 via respective fronthaul links. The RU 440 may communicate with respective UEs 104 via one or more radio frequency (RF) access links. In some implementations, a UE 104 may be served simultaneously by multiple RUs 440.

[0078] Each of the units (i.e., CU 410, DU 430, RU 440, and near-RT RIC 425, non-RT RIC 415, and SMO framework 405) may include or be coupled to one or more interfaces configured to receive or send signals, data, or information (collectively referred to as signals) via a wired or wireless transmission medium. Each of the units or an associated processor or controller that provides instructions to the communication interface of these units may be configured to communicate with one or more of the other units via a transmission medium. For example, these units may include a wired interface configured to receive or send signals to one or more of the other units via a wired transmission medium. In addition, the unit may include a wireless interface, which may include a receiver, a transmitter, or a transceiver (such as a radio frequency (RF) transceiver) configured to receive or send signals, or both, to one or more of the other units via a wireless transmission medium.

[0079] In some aspects, CU 410 may host one or more higher layer control functions. Such control functions may include radio resource control (RRC), packet data convergence protocol (PDCP), service data adaptation protocol (SDAP), etc. Each control function may be implemented using an interface that is configured to communicate signals with other control functions hosted by CU 410. CU 410 may be configured to handle user plane functionality (i.e., central unit-user plane (CU-UP)), control plane functionality (i.e., central unit-control plane (CU-CP)), or a combination thereof. In some specific implementations, CU 410 may be logically split into one or more CU-UP units and one or more CU-CP units. When implemented in an O-RAN configuration, the CU-UP unit may communicate bidirectionally with the CU-CP unit via an interface (such as an E1 interface). As needed, CU 410 may be implemented to communicate with DU 430 for network control and signaling.

[0080] DU 430 may correspond to a logical unit that includes one or more base station functions for controlling the operation of one or more RUs 440. In some aspects, DU 430 may host one or more of a radio link control (RLC) layer, a medium access control (MAC) layer, and one or more high physical (PHY) layers (such as modules for forward error correction (FEC) encoding and decoding, scrambling, modulation and demodulation, etc.) at least in part according to a functional split such as those defined by the 3rd Generation Partnership Project (3GPP). In some aspects, DU 430 may also host one or more low PHY layers. Each layer (or module) may be implemented using an interface that is configured to communicate signals with other layers (and modules) hosted by DU 430 or with control functions hosted by CU 410.

[0081] The lower layer functionality may be implemented by one or more RUs 440. In some deployments, a RU 440 controlled by a DU 430 may correspond to a logical node that hosts RF processing functions or low PHY layer functions (such as performing Fast Fourier Transform (FFT), Inverse FFT (iFFT), digital beamforming, physical random access channel (PRACH) extraction and filtering, etc.), or both, based at least in part on a functional split (such as a lower layer functional split). In such an architecture, the RU 440 may be implemented to handle over-the-air (OTA) communications with one or more UEs 104. In some implementations, real-time and non-real-time aspects of control plane and user plane communications with the RU 440 may be controlled by the corresponding DU 430. In some scenarios, this configuration may enable the implementation of the DU 430 and the CU 410 in a cloud-based RAN architecture (such as a vRAN architecture).

[0082] The SMO framework 405 may be configured to support RAN deployment and provisioning of non-virtualized network elements and virtualized network elements. For non-virtualized network elements, the SMO framework 405 may be configured to support the deployment of dedicated physical resources for RAN coverage requirements, which may be managed via an operation and maintenance interface (such as an O1 interface). For virtualized network elements, the SMO framework 405 may be configured to interact with a cloud computing platform (such as an open cloud (O-Cloud) 490) to perform network element lifecycle management (such as to instantiate virtualized network elements) via a cloud computing platform interface (such as an O2 interface). Such virtualized network elements may include, but are not limited to, CU 410, DU 430, RU 440, and near-RT RIC 425. In some specific implementations, the SMO framework 405 may communicate with hardware aspects of the 4G RAN (such as an open eNB (O-eNB) 411) via the O1 interface. In addition, in some specific implementations, the SMO framework 405 may communicate directly with one or more RUs 440 via the O1 interface. The SMO framework 405 may also include a non-RT RIC 415 configured to support the functionality of the SMO framework 405 .

[0083] The non-RT RIC 415 may be configured to include logic functions that enable non-real-time control and optimization of RAN elements and resources, artificial intelligence / machine learning (AI / ML) workflows including model training and updating, or policy-based guidance of applications / features in the near-RT RIC 425. The non-RT RIC 415 may be coupled to or in communication with the near-RT RIC 425 (such as via an A1 interface). The near-RT RIC 425 may be configured to include logic functions that enable near-real-time control and optimization of RAN elements and resources via data collection and actions through an interface (such as via an E2 interface) that connects one or more CUs 410, one or more DUs 430, or both, and the O-eNB with the near-RT RIC 425.

[0084] In some implementations, in order to generate an AI / ML model to be deployed in the near-RT RIC 425, the non-RT RIC 415 may receive parameters or external enrichment information from an external server. Such information may be utilized by the near-RT RIC 425 and may be received from a non-network data source or from a network function at the SMO framework 405 or the non-RT RIC 415. In some examples, the non-RT RIC 415 or the near-RT RIC 425 may be configured to tune RAN behavior or performance. For example, the non-RT RIC 415 may monitor long-term trends and patterns of performance and employ AI / ML models to perform corrective actions through the SMO framework 405 (such as via reconfiguration of O1) or via creation of RAN management policies (such as A1 policies).

[0085] Figure 5 5 is a diagram illustrating an example of a beam failure detection process. UE 104 may be configured with a periodic BFD-RS 510. For example, BFD-RS 510 may be a synchronization signal block (SSB) or a channel state information reference signal (CSI-RS) transmitted on an active beam for the UE. BFD-RS 510 may have a periodicity that defines a period 512. UE 104 may measure the BFD-RS at the PHY layer. For example, UE 104 may measure a signal to interference plus noise ratio (SINR) or a reference signal received power (RSRP) of BFD-RS 510. When the PHY measurement does not meet a threshold (e.g., a BFD threshold, which may be referred to as a Q out _LR or rsrp-ThresholdSSB), the UE 104 can detect a beam failure instance at the PHY layer. The PHY layer can report the beam failure instance (BFI) to the MAC layer 530.

[0086] The MAC layer 530 may be configured with a BFD timer 520 and a BFI threshold 522. The BFD timer 520 may define a time period for counting BFIs from the PHY layer. The BFI threshold 522 may define the number of BFIs when a beam failure is declared. The MAC layer 530 may maintain a BFI count 524 of BFIs received from the PHY layer during the BFD timer 520. If the MAC layer 530 receives a BFI from the PHY layer, the MAC layer 530 may increment the BFI count 524. When the MAC layer 530 increments the BFI count from 0 to 1, the MAC layer 530 may measure the BFD timer 520. If a BFD-RS is received when the PHY layer measurement meets the threshold, the PHY layer may not report the BFI and the BFI count 524 may remain unchanged. If the BFI count 524 meets the BFI threshold 522 during the BFD timer 520, the UE 104 may initiate a beam failure recovery (BFR) procedure 540. For example, as illustrated, the BFI threshold 522 may be set to 4, and when the BFI count 524 reaches a value of 4, the UE 104 may initiate a BFR process 540 .

[0087] Figure 6 600 is a diagram illustrating a process for fast recovery in a dual connectivity scenario. A UE 104 may communicate with a master cell group (MCG) 610, which may be referred to as a master network (MN), and a secondary cell group (SCG) 620, which may be referred to as a secondary network (SN). The MCG 610 includes a PCell 612 and the SCG 620 includes a PSCell 622. A link 614 between the PCell 612 and the UE 104 may experience a failure such as a radio link failure. Instead of declaring RLF and suspending communication, the UE 104 may send MCG failure information 630 to the PSCell 622 via SCG RRC signaling. The PSCell 622 may forward the MCG failure information 630 as information 632 via a backhaul connection. The MCG may then transition the UE 104 to the PSCell 622 by transmitting transition information 634 to the PSCell 622 via the backhaul connection. The SCG may forward the transition information 634 as a transition command 636 via SCG RRC signaling. Thus, the UE 104 may continue to communicate via the PSCell 622 when the link 614 fails.

[0088] Figure 77 is a diagram illustrating a process for switching a secondary cell to a new primary cell. In the illustrated example, the UE 104 is configured with a first cell 710 as a PCell of a primary component carrier (PCC), a second cell 720 as an SCell of a secondary component carrier (SCC1), and a third cell 730 as an SCell of SCC2. Each configured cell may communicate with the UE 104 via a selected beam 712, 722, 732 of a plurality of beams 714, 724, 734. The UE 104 may also be configured with zero or more neighboring cells 740 for monitoring. For example, the UE 104 may be configured with a measurement object corresponding to a reference signal 742 of each neighboring cell 740.

[0089] In an example beam failure scenario, the quality of the selected beam 712 of the PCell (e.g., the first cell 710) may be degraded such that the selected beam 712 does not meet the threshold. The UE 104 may generate a BFI at the PHY layer, and the MAC layer may determine to initiate a BFR process 540. In one aspect, when other beams of the plurality of beams 714 of the PCell (e.g., the first cell 710) are not suitable and there are no suitable neighboring cells 740, the UE 104 may transition to an SCell (e.g., the third cell 730) instead of declaring an RLF. For example, the third cell 730 may be configured as a new PCell for the UE 104. The second cell 720 may remain as an SCell. In some implementations, if the beam of the first cell 710 is suitable as an SCell, the first cell 710 may be configured as a new SCell for the UE 104. For example, the beam 716 may be used for a secondary component carrier from the first cell 710.

[0090] Figure 8 8 is a logic flow diagram of an example process 800 for switching to an SCell in response to a beam failure of a PCell. Process 800 may be performed by a UE (e.g., UE 104) communicating with one or more base stations providing cells (e.g., cells 710, 720, 730). Initially, at block 805, UE 104 may be configured with carrier aggregation, e.g., Figure 7 exemplified.

[0091] At block 810, the UE may, for example, use Figure 5 The illustrated beam failure detection process periodically monitors the quality of the beam. When the PCell link quality remains above the BFD threshold, the UE 104 can communicate according to the carrier aggregation configuration. If the PCell link quality is less than the BFD threshold, the UE 104 can detect a beam failure.

[0092] At block 815, the UE 104 may start a beam failure recovery procedure, which may include measuring additional beams of the PCell (e.g., the first cell 710). In one aspect, the beam failure recovery procedure may include concurrently measuring beams 724, 734 of secondary cells (e.g., the second cell 720 and the third cell 730). For example, the UE 104 may measure the SINR or RSRP of each beam based on the BFD-RS. In some implementations, the UE 104 may also measure neighboring cells. For example, the neighboring cell measurements may include layer 3 measurements of RSRP. The beam recovery failure procedure may be performed during a beam failure recovery (BFR) timer (which may be referred to as a beamFailureRecoveryTimer) and may be initiated in response to the beam failure detection in block 810.

[0093] At block 820, the UE 104 may determine whether any of the beams 714 of the primary cell (e.g., the first cell 710) is suitable for beam failure recovery. For example, the UE 104 may determine whether any of the beams 714 has an SINR greater than a first threshold, which may be referred to as a BFR threshold, Q in If yes, then at block 825, the UE 104 may report a suitable candidate beam, and the beam failure recovery process may proceed to change the selected beam 712 of the PCell (eg, the first cell 710).

[0094] At block 830, the UE 104 may determine whether any of the neighboring cells 740 are suitable for transition. For example, the UE 104 may be configured with measurement objects for the neighboring cells 740 and measurement objects for transmitting measurement reports to the PCell. If the measurements of one or more neighboring cells meet the criteria, the UE 104 may send a measurement report in block 835, which may cause the PCell to transition the UE 104 to the neighboring cell 740. In one aspect, blocks 820 and 830 may be performed concurrently during a beam failure recovery timer (which may be referred to as a beamFailureRecoveryTimer).

[0095] At block 840, UE 104 may perform a secondary cell switching procedure in accordance with aspects of the present disclosure. The secondary cell switching procedure may include monitoring radio conditions for beams of one or more secondary cells configured for the UE in carrier aggregation to determine whether any of the secondary cells is suitable as a primary cell for the UE. This monitoring may occur concurrently with monitoring the beams of the primary cell during the beam failure recovery procedure. Figures 9 to 11 Further details of the secondary cell switching process are discussed.

[0096] At block 850, the UE 104 may determine whether the beam failure recovery timer has expired. If the beam failure recovery timer has not expired, the beam failure recovery process including the secondary cell switching process may continue from block 815. If the beam failure recovery timer has expired, the UE 104 may proceed to block 860.

[0097] In block 860, the UE 104 may declare a radio link failure. The radio link failure may include suspending communications on the radio link until the radio link can be reestablished. For example, at block 865, the UE may use a RACH procedure to trigger RRC reestablishment.

[0098] Fig. 9 900 is a logic flow diagram of an example process 900 for a secondary cell handover process. Process 900 may be performed by a UE (e.g., UE 104) communicating with one or more base stations providing cells (e.g., cells 710, 720, 730). Process 900 may begin as described above with respect to Figure 8 Block 840 of the discussed process 800. For example, process 900 may occur during a beam failure recovery process when there are no suitable beam failure recovery candidate beams on the primary cell (e.g., block 820) and / or there are no suitable neighboring cells for transition (e.g., block 830).

[0099] At block 910, the UE 104 may determine whether there are any suitable SCell candidates. In some implementations, a suitable SCell candidate may be a beam from an SCell that has met a threshold. For example, the UE 104 may be configured with a primary-secondary switching threshold. The radio condition (e.g., RSRP) of each beam of the measured secondary cell may be compared with the primary-secondary switching threshold to determine whether the beam is a suitable SCell candidate. In some implementations, the beam of the secondary cell may be compared with the best beam of the primary cell. For example, the UE 104 may be configured with a primary-secondary switching offset. If the measured radio condition of the secondary cell beam is better than the measured radio condition of the best primary cell beam by at least the primary-secondary switching offset, the secondary cell beam may be considered a suitable SCell candidate. If the UE 104 determines a suitable SCell candidate, the process 900 may proceed to block 920. If there is no suitable SCell candidate, the process 900 may proceed to block 850.

[0100] At block 920, UE 104 may transmit a MAC-CE with one or more suitable SCell candidates. Fig.10As discussed, the MAC-CE may be a BFR MAC-CE or similar MAC-CE dedicated to SCell switching request. The MAC-CE may indicate the candidate SCell index to be reconfigured as PCell. The MAC-CE may also indicate the reference signal ID for the SCell to identify the candidate beam.

[0101] At block 930, the UE 104 may receive a reconfiguration of the SCell as a new PCell. For example, the UE 104 may receive an RRC reconfiguration message. If the UE 104 receives the reconfiguration, then in block 940, the UE 104 may perform a transition to the new PCell. If the UE 104 does not receive the SCell reconfiguration, the process 900 may proceed to block 850 of the process 800 to determine whether the beam failure recovery timer has expired. In some implementations, if the beam failure recovery timer has not expired, the process 900 may return to block 910 to determine whether any other SCell candidates are suitable. If the beam failure recovery timer has expired, the process 900 may proceed to block 860, where the UE 104 declares RLF.

[0102] Fig.10 is a diagram of an example MAC-CE 1000 for indicating suitable SCell candidates for SCell switching. The MAC-CE 1000 may be structured as a series of octets and may be transmitted on the PUSCH.

[0103] Cell index field 1010 (C i ) is included in the first octet of the MAC-CE 1000 and may indicate a MAC address having an index C i Whether the beam of the SCell is included in the MAC-CE 1000. In some specific implementations, C i The field may be extended to four octets to include up to 24 cell indexes.The SP bit 1012 indicating beam failure detection may follow the cell index field 1010 in the first octet or the fourth octet.

[0104] The additional octet 1020 of the MAC-CE 1000 may use a reference signal ID 1026 to identify a single beam. For example, the reference signal ID 1026 may be set to the index of the SSB corresponding to the appropriate beam of the SCell. Each additional octet 1020 may also include an AC bit 1022 indicating the presence of a candidate reference signal ID in the octet. In some implementations, a reserved (R) bit that is not used for a conventional beam failure reporting MAC-CE may be used to indicate an SCell switching candidate. For example, the R bit 1024 may be used to indicate that the candidate RS is an SCell switching candidate rather than a beam change candidate for the SCell.

[0105] Fig.11 1 is a message diagram 1100 illustrating example messages between a base station 102 and a UE 104. The UE 104 can be an example of a UE 104 that includes an SCell switching component 140. The base station 102 can include an SCell control component 120. In some implementations, the base station 102 can provide both a PCell 1106 and one or more SCells 1108. In other implementations, the PCell 1106 and the SCell 1108 can be provided by different base stations.

[0106] In some implementations, the UE 104 may also optionally send a capability message 1110 to the base station 102. For example, the capability message 1110 may be an RRC message. The capability message 1110 may indicate, for example, that the UE 104 is capable of switching the SCell to the PCell. For example, this capability may be referred to as a P-SCellSwitch capability.

[0107] In some implementations, the base station 102 may optionally send a configuration 1120. The configuration 1120 may be an RRC message. For example, the configuration 1120 may include a configuration of a SCell switching process. For example, the configuration 1120 may include a flag indicating whether the SCell switching process is active or allowed (e.g., a P-SCell switching indication 1122). The configuration 1120 may include a switching threshold 1124 (e.g., rsrp-ThresholdP-SCellSwitch) that defines a threshold of a radio condition (e.g., RSRP) of a suitable candidate SCell beam. The configuration 1120 may include a switching offset 1126 (e.g., rsrp-ThresholdOffsetP-SCellSwitch) that defines a threshold difference between the radio condition of the best beam of the PCell and the radio condition of the suitable candidate SCell beam.

[0108] UE 104 may perform beam failure monitoring 1130. For example, UE 104 may receive a beam failure detection reference signal (BFD-RS) 1132 from PCell 1106. For example, BFD-RS 1132 may be an SSB or a CSI-RS. UE 104 may detect beam failures (e.g., Figure 5 ). The UE 104 may start a PCell beam failure recovery procedure 1136 for the PCell. In one aspect, concurrently with the PCell beam failure recovery procedure 1136, the UE 104 may monitor the SCell beam in block 1138. For example, the UE 104 may receive a BFD-RS 1134 from the SCell 1108 and may measure radio conditions (e.g., RSRP or SINR).

[0109] If the UE 104 determines during the beam failure recovery procedure that the SCell beam is a suitable candidate beam, the UE 104 may send an SCell switching request 1140. For example, the SCell switching request 1140 may be a MAC-CE 1010. The SCell switching request 1140 may be sent on any available uplink resource. For example, the UE 104 may send the SCell switching request 1140 on an uplink grant of the PCell 1106 or one of the one or more SCells 1108. In some implementations, sending the SCell switching request 1140 on the SCell 1108 may be more reliable in the event of a beam failure on the PCell 1106.

[0110] The SCell switch request 1140 may identify a suitable SCell candidate, but the network may control whether the UE 104 switches to the SCell 1108. For example, if the identified SCell 1108 is suitable as a new PCell, the network may control the transition of the UE 104 to the SCell 1108 as the new PCell. For example, the PCell 1106 may send an RRC reconfiguration message 1150 to reconfigure the SCell 1108 as a new PCell. For example, the RRC reconfiguration message 1150 may configure a new bandwidth portion or search space for the SCell 1108. The RRC reconfiguration message 1150 may also specify that the SCell 1108 is a new PCell. In some specific implementations, the RRC reconfiguration message 1150 may reconfigure the PCell 1106 as a new SCell. The UE 104 may send an RRC reconfiguration complete message 1160 to complete the transition to the new PCell (formerly the SCell 1108).

[0111] Fig.12 1 is a conceptual data flow diagram 1200 illustrating data flow between different parts / components in an example base station 102, which may be an example of a base station 102 including an SCell control component 120. The SCell control component 120 may be composed of Figure 3 The memory 376 and the Tx processor 316, the Rx processor 370 and / or the controller / processor 375 of the predictive control component 120 can be implemented. For example, the memory 376 can store executable instructions defining the predictive control component 120, and the Tx processor 316, the Rx processor 370 and / or the controller / processor 375 can execute these instructions.

[0112] Base station 102 may include a receiver component 1250, which may include, for example, a radio frequency (RF) receiver for receiving the signals described herein. Base station 102 may include a transmitter component 1252, which may include, for example, an RF transmitter for transmitting the signals described herein. In one aspect, receiver component 1250 and transmitter component 1252 may be co-located in a transceiver such as Figure 3 (illustrated in Tx / Rx 318).

[0113] As compared to Figure 1 As discussed, SCell control component 120 can include configuration component 122, switching component 124, and reconfiguration component 126. In some implementations, SCell control component 120 can optionally include capability component 1210.

[0114] Receiver component 1250 can receive an UL signal from UE 104 including capability message 1110, SCell switching request 1140, or RRC reconfiguration complete message 1160. Receiver component 1250 can provide capability message 1110 to configuration component 122. Receiver component 1250 can provide SCell switching request 1140 to switching component 124. Receiver component 1250 can provide RRC reconfiguration complete message 1160 to reconfiguration component 126.

[0115] The capability component 1210 may be configured to receive an indication of the capability of the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as a new primary cell. For example, the capability component 1210 may receive an RRC capability message including an information element for SCell switching (e.g., P-SCellSwitch). The capability component 1210 may determine that the UE is capable of SCell switching based on receiving the capability message. The capability component 1210 may indicate to the configuration component 122 that the UE is capable of SCell switching.

[0116] The configuration component 122 may be configured to configure a primary cell and one or more secondary cells for the UE in carrier aggregation. For example, the configuration component 122 may generate an RRC configuration 1120 having multiple serving cells and carrier aggregation parameters for the UE. In some implementations, the configuration component 122 may configure SCell switching parameters for the UE, such as a P-SCell switching indication 1122, a switching threshold 1124, and a switching offset 1126. The configuration component 122 may send the configuration 1120 via the transmitter component 1252. The configuration component 122 may provide the SCell switching parameters to the switching component 124.

[0117] The switching component 124 may be configured to receive a request to configure at least one candidate secondary cell of the one or more secondary cells as a candidate beam of the new primary cell. For example, the switching component 124 may receive the SCell switching request 1140 via the receiver component 1250. For example, the switching request 1140 may be a MAC-CE 1010 or another message such as an RRC message including a reference signal identifier of a candidate beam of the secondary cell. The received switching request 1140 indicates that a first radio condition of the UE for the beam of the primary cell does not satisfy a first threshold (e.g., a BFR threshold) and a second radio condition for the candidate beam of the at least one candidate secondary cell satisfies a second threshold (e.g., a switching threshold 1124).

[0118] The switching component 124 may determine whether to switch the candidate beam of the candidate secondary cell to the primary cell. For example, the switching component 124 may determine whether the candidate secondary cell can serve as the primary cell. The switching component 124 may determine whether the candidate secondary cell has available resources for the UE. If the switching component 124 determines to switch the candidate beam of the candidate secondary cell to the primary cell, the switching component 124 may indicate the candidate beam and the candidate secondary cell to the reconfiguration component 126.

[0119] The reconfiguration component 126 may be configured to switch the UE to the new primary cell. The reconfiguration component 126 may reconfigure the candidate secondary cell (e.g., SCell 1108) as the new primary cell. For example, the reconfiguration component 126 may send an RRC reconfiguration message 1150 to the UE 104 via the transmitter component 1252. The reconfiguration message 1150 may be a switching command that causes the UE to perform a switching process to the new primary cell. In some specific implementations, the reconfiguration message 1150 may reconfigure the PCell 1106 as the new secondary cell.

[0120] Fig.13 is a conceptual data flow diagram 1300 illustrating data flow between different parts / components in an example UE 104, which may include a SCell switching component 140. The SCell switching component 140 may be implemented by a memory 360 and a Tx processor 368, an Rx processor 356, and / or a controller / processor 359. For example, the memory 360 may store executable instructions defining the SCell switching component 140, and the Tx processor 368, the Rx processor 356, and / or the controller / processor 359 may execute these instructions.

[0121] UE 104 may include a receiver component 1370, which may include, for example, an RF receiver for receiving the signals described herein. UE 104 may include a transmitter component 1372, which may include, for example, an RF transmitter for transmitting the signals described herein. In one aspect, receiver component 1370 and transmitter component 1372 may be co-located in a transceiver, such as Figure 3 Tx / Rx352 in.

[0122] As compared to Figure 1 As discussed, the SCell switching component 140 can include a monitoring component 142, a switching request component 144, and a switching component 146. In some implementations, the SCell switching component 140 can optionally include a capability component 1310 or a configuration component 1320.

[0123] Receiver component 1370 can receive DL signals described herein, such as configuration 1120, BFD-RS 1132 and 1134, and RRC reconfiguration message 1150. Receiver component 1370 can provide configuration 1120 to configuration component 1320. Receiver component 1370 can provide BFD-RS 1132 and 1134 (or measurements thereof) to monitoring component 142. Receiver component 1370 can provide RRC reconfiguration message 1150 to conversion component 146.

[0124] In some implementations, the capability component 1310 may be configured to send an indication of the capability of the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as a new primary cell. For example, the capability component 1310 may send the RRC capability message 1110 via the transmitter component 1372.

[0125] In some implementations, the configuration component 1320 can be configured to receive a configuration of the SCell switching parameters. For example, the configuration component 1320 can receive a first threshold (e.g., a BFD threshold 1322), a second threshold (e.g., a switching threshold 1124), a third threshold (e.g., a switching offset 1126), and / or a fourth threshold (e.g., a neighboring threshold 1326). The configuration component 1320 can configure the monitoring component 142 with the SCell switching parameters.

[0126] The monitoring component 142 may be configured to monitor the UE for a first radio condition of a beam of a primary cell and a second radio condition of a beam of one or more secondary cells configured for the UE in carrier aggregation. For example, the monitoring component 142 may monitor the RSRP or SINR of the BFD-RS 1132 to determine a first radio condition for a beam of the PCell 1106. The monitoring component 142 may monitor the RSRP or SINR of the BFD-RS 1134 to determine a second radio condition for a beam of the SCell 1108. In some specific implementations, the monitoring component 142 may also monitor radio conditions of neighboring cells (e.g., neighboring cells 740). When the monitoring component 142 declares a beam failure of the primary cell, the monitoring component may concurrently monitor the candidate beams of the primary cell for a beam failure recovery process and monitor the candidate beams on the secondary cell for a secondary cell switching process. As discussed above with respect to blocks 820, 830, and / or 910, the monitoring component 142 may compare the measured radio conditions with corresponding configured thresholds to determine a suitable candidate beam. Monitoring component 142 can provide the secondary cell candidate beams to handover request component 144 .

[0127] The handover request component 144 may be configured to send a request to configure at least one candidate secondary cell of the one or more secondary cells as a candidate beam of the new primary cell. For example, the handover request component 144 may send the request in response to the monitoring component 142 determining that the first radio condition does not meet the first threshold and the second radio condition for the at least one candidate secondary cell meets the second threshold. For example, the handover request component 144 may send the SCell handover request 1140 via the transmitter component 1372. In some specific implementations, the handover request component 144 may be a MAC-CE 1010. The handover request component 144 may, for example, send the SCell handover request 1140 to the PCell 1106 or SCell 1108 based on the available uplink grant. The handover request component 144 may use the scheduling request on the PUCCH to obtain the uplink grant. The MAC-CE 1010 may identify the cell index and candidate reference signal for at least one candidate beam. For example, the MAC-CE 1010 may include information for the best candidate SCell beam. In some implementations, the MAC-CE 1010 can include information for all suitable candidate SCell beams. In some implementations, the handover request component 144 can be an RRC message including similar information as the MAC-CE 1010. The RRC reconfiguration can be sent to the PCell 1106.

[0128] The switching component 146 can be configured to perform a switch to the new primary cell. For example, the switching component 146 can receive the switch command as an RRC reconfiguration message 1150 via the receiver component 1370. The switching component 146 can reconfigure the SCell 1108 as the new primary cell. The SCell 1108 can receive the configuration parameters of the UE 104 from the PCell 1106 via the backhaul. Therefore, once the UE 104 reconfigures the SCell 1108, the UE 104 can use the RRC connection with the new PCell to complete the switch. The UE 104 can send an RRC reconfiguration completion message 1160 to the new primary cell.

[0129] Fig.14 1 is a flow chart of an example method 1400 for UE 104 to perform switching to an SCell using a beam failure procedure. Method 1400 may be performed by UE 104 (such as UE 104, which may include memory 360, and may be the entire UE 104 or a component of UE 104, such as SCell switching component 140, Tx processor 368, Rx processor 356, or controller / processor 359). Method 1400 may be performed by SCell switching component 140 in communication with prediction control component 120 of base station 102. Optional blocks are shown with dashed lines.

[0130] At block 1410, the method 1400 may optionally include sending an indication of the capability of the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as a new primary cell. In some specific implementations, for example, the UE 104, the Tx processor 368, or the controller / processor 359 may execute the SCell switching component 140 or the capability component 1310 to send an indication of the capability of the UE 104 to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as a new primary cell (e.g., a capability message 1110). Therefore, the UE 104, the Tx processor 368, or the controller / processor 359 executing the SCell switching component 140 or the capability component 1310 may provide a component for sending a request for activation or deactivation of beam failure prediction.

[0131] At block 1415, the method 1400 may optionally include receiving a configuration that allows the UE to switch from the primary cell to the one or more secondary cells configured for the UE in the carrier aggregation as a new primary cell. In some specific implementations, for example, the UE 104, the Rx processor 356, or the controller / processor 359 may execute the SCell switching component 140 or the configuration component 1320 to receive a configuration (e.g., P-SCell switching indication 1122) that allows the UE 104 to switch from the primary cell to the one or more secondary cells configured for the UE in the carrier aggregation as a new primary cell. Therefore, the UE 104, the Rx processor 356, or the controller / processor 359 that executes the SCell switching component 140 or the configuration component 1320 may provide a component for receiving a configuration that allows the UE to switch from the primary cell to the one or more secondary cells configured for the UE in the carrier aggregation as a new primary cell.

[0132] At block 1420, the method 1400 may optionally include receiving a configuration of a first threshold and a second threshold. In some implementations, for example, the UE 104, the Rx processor 356, or the controller / processor 359 may execute the SCell switching component 140 or the configuration component 1320 to receive a configuration 1120 of a first threshold (e.g., a BFR threshold 1324) and a second threshold (e.g., a switching threshold 1124). In some implementations, the configuration component 1320 may receive configurations of additional thresholds, such as a BFD threshold 1322 for declaring a beam failure, a third threshold for comparing the first radio condition and the second radio condition (e.g., a switching offset 1126), or a fourth threshold for evaluating a neighboring cell 740 (e.g., a neighboring threshold 1326). Thus, the UE 104, the Rx processor 356, or the controller / processor 359 executing the SCell switching component 140 or the configuration component 1320 may provide a means for receiving a configuration of the first threshold and the second threshold.

[0133] At block 1430, method 1400 includes monitoring a first radio condition of the UE for a beam of a primary cell and a second radio condition for a beam of one or more secondary cells configured for the UE in carrier aggregation. In some implementations, for example, the UE 104, the Rx processor 356, or the controller / processor 359 may execute the SCell switching component 140 or the monitoring component 142 to monitor the first radio condition of the UE for a beam of the PCell 1106 and a second radio condition for a beam of one or more SCells 1108 configured for the UE 104 in carrier aggregation. In some implementations, at subblock 1432, block 1430 may optionally include performing a beam failure recovery procedure for the primary cell. For example, the monitoring component 142 may be based on, for example, the information relative to the primary cell. Figure 5The monitoring component 142 may detect a beam failure by using the BFD threshold described. In response to declaring a beam failure, the monitoring component 142 may search for a suitable PCell candidate beam for a BFR process. At sub-block 1434, block 1430 may optionally include concurrently monitoring a first radio condition and a second radio condition during a beam failure recovery process. For example, the monitoring component 142 may monitor the BFD-RS 1134 of the secondary cell during a BFR timer. Thus, the UE 104, the Rx processor 356, or the controller / processor 359 that performs the SCell switching component 140 or the monitoring component 142 may provide a component for monitoring a first radio condition of the UE for a beam of a primary cell and a second radio condition for a beam of one or more secondary cells configured for the UE in carrier aggregation.

[0134] At block 1440, the method 1400 includes, in response to the first radio condition not satisfying the first threshold and the second radio condition for at least one of the one or more secondary cells satisfying the second threshold, sending a request to configure the at least one candidate secondary cell as a candidate beam of the new primary cell. In some implementations, for example, the UE 104, the Tx processor 368, or the controller / processor 359 may execute the SCell switching component 140 or the switching request component 144 to, in response to the first radio condition not satisfying the first threshold (e.g., the BFR threshold 1324) and the second radio condition for at least one of the one or more secondary cells 730 satisfying the second threshold (e.g., the switching threshold 1124), send a request (e.g., the SCell switching request 1140) to configure the at least one candidate secondary cell as a candidate beam (e.g., beam 732) of the new primary cell. In some implementations, sending the request is also in response to the second radio condition of the candidate beam of the at least one candidate secondary cell being greater than the first radio condition of the best beam of the primary cell by at least a third threshold (e.g., the switching offset 1126). In some implementations, sending the request is also in response to a value of a configured measurement object corresponding to a neighboring cell not satisfying a fourth threshold (eg, neighboring threshold 1326) for transitioning to a neighboring cell.

[0135] In some implementations, at sub-block 1442, block 1440 may include sending a MAC-CE 1010 including a reference signal identifier 1026 corresponding to the candidate beam 732 of the at least one candidate secondary cell 730 having a second radio condition satisfying a second threshold. For example, the handover request component 144 may include sending the MAC-CE 1010 on an uplink grant for the primary cell or for one of the one or more secondary cells. In some implementations, at sub-block 1444, block 1440 may optionally include sending an RRC message including a reference signal identifier corresponding to the candidate beam of the at least one candidate secondary cell having a second radio condition satisfying the second threshold. Therefore, the UE 104, Tx processor 368 or controller / processor 359 that executes the SCell switching component 140 or capability component 1310 may provide a component for sending a request to configure the at least one candidate secondary cell as a candidate beam of a new primary cell in response to a first radio condition not satisfying a first threshold and a second radio condition for at least one of the one or more secondary cells satisfying a second threshold.

[0136] At block 1450, the method 1400 includes performing a transition to a new primary cell. In some implementations, for example, the UE 104, the Rx processor 356, or the controller / processor 359 may execute the SCell switching component 140 or the transition component 146 to perform the transition to the new primary cell. In some implementations, at sub-block 1452, block 1450 may optionally include receiving a reconfiguration of a candidate secondary cell as a new primary cell (e.g., an RRC reconfiguration message 1150). Block 1450 may also optionally include sending an RRC reconfiguration complete message 1160. Thus, the UE 104, the Rx processor 356, or the controller / processor 359 that executes the SCell switching component 140 or the transition component 146 may provide a component for performing a transition to a new primary cell.

[0137] Fig.15 1 is a flow chart of an example method 1500 for a base station to switch a UE to a secondary cell. The method 1500 may be performed by a base station, such as the base station 102, which may include the memory 376 and which may be the entire base station 102 or a component of the base station 102, such as the SCell control component 120, the Tx processor 316, the Rx processor 370, or the controller / processor 375. The method 1500 may be performed by the SCell control component 120 in communication with the SCell switching component 140 of the UE 104.

[0138] At block 1510, the method 1500 may optionally include receiving an indication of the capability of the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as a new primary cell. In some specific implementations, for example, the base station 102, the Rx processor 370, or the controller / processor 375 may execute the SCell control component 120 or the capability component 1210 to receive an indication of the capability of the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as a new primary cell. Therefore, the base station 102, the Rx processor 370, or the controller / processor 375 executing the SCell control component 120 or the capability component 1210 may provide a component for receiving an indication of the capability of the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as a new primary cell.

[0139] At block 1520, the method 1500 includes configuring a primary cell and one or more secondary cells for the UE in carrier aggregation. In some implementations, for example, the base station 102, the Tx processor 316, or the controller / processor 375 may execute the SCell control component 120 or the configuration component 122 to configure the primary cell 710 and one or more secondary cells 720, 730 for the UE 104 in carrier aggregation. Thus, the base station 102, the Tx processor 316, or the controller / processor 375 executing the SCell control component 120 or the configuration component 122 may provide a means for configuring the primary cell and one or more secondary cells for the UE in carrier aggregation.

[0140] At block 1525, the method 1500 may optionally include configuring an indication that the UE is allowed to switch from the primary cell to the one or more secondary cells configured for the UE in the carrier aggregation as a new primary cell. In some specific implementations, for example, the base station 102, the Tx processor 316, or the controller / processor 375 may execute the SCell control component 120 or the configuration component 122 to configure an indication 1122 that the UE is allowed to switch from the primary cell to the one or more secondary cells configured for the UE in the carrier aggregation as a new primary cell. Therefore, the base station 102, the Tx processor 316, or the controller / processor 375 executing the SCell control component 120 or the configuration component 122 may provide a component for configuring an indication that the UE is allowed to switch from the primary cell to the one or more secondary cells configured for the UE in the carrier aggregation as a new primary cell.

[0141] At block 1530, the method 1500 may optionally include sending a configuration of the first threshold and the second threshold. In some implementations, for example, the base station 102, the Tx processor 316, or the controller / processor 375 may execute the SCell control component 120 or the configuration component 122 to send a configuration of the first threshold (e.g., the BFR threshold 1324) and the second threshold (e.g., the handover threshold 1124). Block 1530 may also include sending a configuration of the third threshold (e.g., the handover offset 1126) and / or the fourth threshold (e.g., the adjacent threshold 1326). Thus, the base station 102, the Tx processor 316, or the controller / processor 375 executing the SCell control component 120 or the configuration component 122 may provide a component for sending a configuration of the first threshold and the second threshold.

[0142] At block 1540, the method 1500 includes receiving a request to configure at least one candidate secondary cell of the one or more secondary cells as a candidate beam of a new primary cell. In some implementations, for example, the base station 102, the Rx processor 370, or the controller / processor 375 may execute the SCell control component 120 or the switching component 124 to receive a request to configure at least one candidate secondary cell of the one or more secondary cells as a candidate beam of a new primary cell. In some implementations, the receiving request indicates that the second radio condition of the candidate beam of the at least one candidate secondary cell is greater than the first radio condition of the best beam of the primary cell by at least a third threshold (e.g., the switching offset 1126). In some implementations, the receiving request indicates that the value of the configured measurement object corresponding to the neighboring cell 740 for the UE does not meet the fourth threshold (e.g., the neighboring offset 1326) for switching to the neighboring cell. In some implementations, at sub-block 1542, block 1540 may optionally include receiving a MAC-CE including a reference signal identifier corresponding to the candidate beam of the at least one candidate secondary cell having a second radio condition that meets the second threshold. For example, the switching component 124 may receive a MAC-CE 1010 on an uplink grant for the primary cell or for one of the one or more secondary cells. In some implementations, the MAC-CE includes a bit 1024 indicating a request to switch to a candidate beam of the at least one candidate secondary cell instead of a failure of the candidate beam. In some implementations, at sub-box 1544, box 1540 may optionally include receiving an RRC message including a reference signal identifier corresponding to a candidate beam of the at least one candidate secondary cell having a second radio condition satisfying a second threshold. Thus, the base station 102, the Rx processor 370, or the controller / processor 375 executing the SCell control component 120 or the switching component 124 may provide a component for receiving a request to configure at least one of the one or more secondary cells as a candidate beam of a new primary cell.

[0143] At block 1550, the method 1500 may optionally include transitioning the UE to the new primary cell. In some implementations, for example, the base station 102, the Tx processor 316, or the controller / processor 375 may execute the SCell control component 120 or the reconfiguration component 126 to transition the UE 104 to the new primary cell (e.g., cell 730). In some implementations, at block 1552, the block 1550 may optionally include sending a reconfiguration (e.g., RRC reconfiguration message 1150) of a candidate secondary cell as the new primary cell. Thus, the base station 102, the Tx processor 316, or the controller / processor 375 executing the SCell control component 120 or the reconfiguration component 126 may provide a component for transitioning the UE to the new primary cell.

[0144] The various illustrative logics, logic blocks, modules, circuits, and algorithmic processes described in conjunction with the specific implementations disclosed herein may be implemented as electronic hardware, computer software, or a combination of both. The interchangeability of hardware and software has been generally described in terms of functionality and exemplified in the various illustrative components, blocks, modules, circuits, and processes described above. Whether such functionality is implemented in hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0145] The hardware and data processing apparatus for implementing the various illustrative logics, logic blocks, modules and circuits described in conjunction with the various aspects disclosed herein may be implemented or executed using a general purpose single-chip or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic component, a discrete hardware component or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or any conventional processor, controller, microcontroller or state machine. A processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration. In some implementations, specific processes and methods may be performed by circuits specific to a given function.

[0146] In one or more aspects, the functions described may be implemented in hardware, digital electronic circuitry, computer software, firmware, including the structures disclosed in this specification and their structural equivalents, or any combination thereof. Specific implementations of the subject matter described in this specification may also be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, which are encoded on computer storage media for execution by data processing apparatus or to control the operation of data processing apparatus.

[0147] If implemented in software, the function may be stored as one or more instructions or codes on a computer-readable medium or sent via a computer-readable medium. The process of the method or algorithm disclosed herein may be implemented in a processor executable software module that may reside on a computer-readable medium. Computer-readable media include both computer storage media and communication media, and communication media include any medium that can realize the transfer of a computer program from one place to another. The storage medium may be any available medium that a computer can access. By way of example and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, disk storage devices or other magnetic storage devices, or any other medium that can be used to store the desired program code in the form of an instruction or data structure and can be accessed by a computer. In addition, any connection may be appropriately referred to as a computer-readable medium. Disks and optical disks as used herein include compact disks (CDs), laser disks, optical disks, digital versatile disks (DVDs), floppy disks, and blue-ray disks, wherein disks generally reproduce data magnetically, and optical disks reproduce data optically with lasers. The above combination should also be included in the scope of computer-readable media. Additionally, the operations of a method or algorithm may reside as a code and instruction set, or any combination of code and instruction sets, on a machine-readable medium or computer-readable medium, which may be incorporated into a computer program product.

[0148] Various modifications to the specific implementations described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other specific implementations without departing from the spirit or scope of the disclosure. Therefore, the claims are not intended to be limited to the specific implementations shown herein, but are to be consistent with the broadest scope consistent with the disclosure, the principles and novel features disclosed herein.

[0149] Additionally, one of ordinary skill in the art will readily recognize that the terms "upper" and "lower" are sometimes used for ease of describing the drawings and indicate relative positions corresponding to the orientation of the drawings on a correctly oriented page, and may not reflect the correct orientation of any device as implemented.

[0150] Certain features described in this specification in the context of a single implementation may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations individually or in any suitable subcombination. Furthermore, while some features are described above as working in a particular combination and even initially claimed as such, in some cases one or more features from a claimed combination may be cut out of the combination, and a claimed combination may involve a subcombination or a variation of a subcombination.

[0151] Similarly, although the operations are depicted in a specific order in the figure, this should not be understood as requiring such operations to be performed in the specific order shown or in a sequential order, or to perform all the illustrated operations to achieve the desired result. In addition, the accompanying drawings can schematically depict one or more example processes in the form of a flow chart. However, other operations not depicted can be incorporated into the schematically illustrated example process. For example, one or more additional operations can be performed before, after, at the same time, or between any operations in the illustrated operation. In some environments, multitasking and parallel processing are advantageous. In addition, the separation of various system components in the specific implementation described above should not be understood as requiring such separation in all specific implementations, but it should be understood that the described program components and systems can usually be integrated together in a single software product, or be packaged in multiple software products. In addition, other specific implementations are within the scope of the following claims. In some cases, the actions recorded in the claims can be performed in different orders and still achieve the desired result.

[0152] The following numbered clauses provide an overview of various aspects of the disclosure:

[0153] Clause 1. A method for performing wireless communications at a user equipment (UE), the method comprising: monitoring a first radio condition of the UE for a beam of a primary cell and a second radio condition for a beam of one or more secondary cells configured for the UE in carrier aggregation; in response to the first radio condition not satisfying a first threshold and the second radio condition for at least one candidate secondary cell among the one or more secondary cells satisfying a second threshold, sending a request to configure the at least one candidate secondary cell as a candidate beam of a new primary cell; and performing a transition to the new primary cell.

[0154] Clause 2. A method according to clause 1, wherein the monitoring includes performing a beam failure recovery procedure for the primary cell, wherein the UE is configured to concurrently monitor the first radio condition and the second radio condition during the beam failure recovery procedure.

[0155] Clause 3. A method according to clause 1 or 2, wherein sending the request includes sending a medium access control (MAC) control element (CE) including a reference signal identifier corresponding to the candidate beam of the at least one candidate secondary cell having a second radio condition that satisfies the second threshold.

[0156] Clause 4. The method of clause 3, wherein sending the request comprises sending the MAC-CE on an uplink grant for the primary cell or for one of the one or more secondary cells.

[0157] Clause 5. A method according to any one of clauses 1 to 4, the method further comprising sending an indication of the capability of the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as the new primary cell.

[0158] Clause 6. The method of any one of clauses 1 to 5, further comprising receiving a configuration of the first threshold and the second threshold.

[0159] Clause 7. A method according to any one of clauses 1 to 6, wherein sending the request is also in response to the second radio condition of the candidate beam of the at least one candidate secondary cell being greater than the first radio condition of the best beam of the primary cell by at least a third threshold.

[0160] Clause 8. A method as described in any of clauses 1 to 7, wherein sending the request is also in response to a value of a configured measurement object corresponding to a neighboring cell not satisfying a fourth threshold for transitioning to a neighboring cell.

[0161] Clause 9. The method of any of clauses 1 to 8, wherein performing the transition to the new primary cell comprises receiving a reconfiguration of a candidate secondary cell as the new primary cell.

[0162] Clause 10. A method according to any one of clauses 1 or 5 to 9, wherein sending the request comprises sending a radio resource control (RRC) message, the radio resource control (RRC) message comprising a reference signal identifier corresponding to a candidate beam of the at least one candidate secondary cell having a second radio condition satisfying the second threshold.

[0163] Clause 11. An apparatus for wireless communication of a user equipment (UE), the apparatus comprising: a memory storing computer-executable instructions; and at least one processor coupled to the memory and configured to execute the computer-executable instructions so that the UE performs a method according to any one of clauses 1 to 10.

[0164] Clause 12. An apparatus for wireless communication of a user equipment (UE), the apparatus comprising means for performing a method as recited in any of clauses 1 to 10.

[0165] Clause 13. A non-transitory computer-readable medium storing computer-executable instructions configured to cause a UE to perform a method as recited in any one of clauses 1 to 10.

[0166] Clause 14. A method for performing wireless communications at a network entity, the method comprising: configuring a primary cell and one or more secondary cells for a user equipment (UE) in carrier aggregation; receiving a request to configure at least one candidate secondary cell among the one or more secondary cells as a candidate beam of a new primary cell, wherein the request indicates that a first radio condition of the UE for the beam of the primary cell does not satisfy a first threshold and a second radio condition of the candidate beam of the at least one candidate secondary cell satisfies a second threshold; and switching the UE to the new primary cell.

[0167] Clause 15. A method according to clause 14, wherein receiving the request includes receiving a medium access control (MAC) control element (CE) including a reference signal identifier corresponding to the candidate beam of the at least one candidate secondary cell having the second radio condition satisfying the second threshold.

[0168] Clause 16. The method of clause 15, wherein receiving the request comprises receiving the MAC-CE on an uplink grant for the primary cell or one of the one or more secondary cells.

[0169] Clause 17. The method of clause 15, wherein the MAC-CE includes a bit indicating the request to switch to the candidate beam of the at least one candidate secondary cell instead of a failure of the candidate beam.

[0170] Clause 18. A method as described in any of clauses 14 to 17, the method further comprising receiving an indication of the capability of the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as the new primary cell.

[0171] Clause 19. A method according to any of clauses 14 to 18, the method further comprising configuring an indication for allowing the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as the new primary cell.

[0172] Clause 20. A method according to any one of clauses 14 to 19, wherein receiving the request indicates that the second radio condition of the candidate beam of the at least one candidate secondary cell is greater than the first radio condition of the best beam of the primary cell by at least a third threshold.

[0173] Clause 21. A method as described in any of clauses 14 to 20, wherein receiving the request indicates that a value of a configured measurement object corresponding to a neighboring cell for the UE does not satisfy a fourth threshold for transitioning to a neighboring cell.

[0174] Clause 22. A method as described in any of clauses 14 to 21, wherein transitioning the UE to the new primary cell comprises sending a candidate secondary cell as a reconfiguration of the new primary cell.

[0175] Clause 23. A method according to any one of clauses 14 or 18 to 22, wherein receiving the request includes receiving a radio resource control (RRC) message, the radio resource control (RRC) message including a reference signal identifier corresponding to a candidate beam of the at least one candidate secondary cell having a second radio condition that satisfies the second threshold.

[0176] Clause 24. An apparatus for wireless communication of a base station, the apparatus comprising: a memory storing computer-executable instructions; and at least one processor coupled to the memory and configured to execute the computer-executable instructions so that the base station performs a method according to any one of clauses 14 to 23.

[0177] Clause 25. An apparatus for wireless communication of a base station, the apparatus comprising means for performing the method of any of clauses 14 to 23.

[0178] Clause 26. A non-transitory computer-readable medium storing computer-executable instructions configured to cause the base station to perform the method of any of clauses 14 to 23.

[0179] The preceding 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 apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects. Therefore, the claims are not intended to be limited to the aspects shown herein, but to conform to the full scope consistent with the language claims, wherein unless otherwise specified, the elements mentioned in the singular are not intended to represent "one and only one", but "one or more". The word "exemplary" is used herein to mean "used as an example, instance, or illustration". Any aspect described as "exemplary" herein is not necessarily interpreted as being preferred or having advantages over other aspects. Unless otherwise specified, the term "some" refers to one or more. Combinations such as "at least one of A, B, or C", "one or more of A, B, or C", "at least one of A, B, and C", "one or more of A, B, and C", and "A, B, C, or any combination thereof", including any combination of A, B, and / or C, which may include multiple A, multiple B, or multiple C. Specifically, combinations such as "at least one of A, B, or C," "one or more of A, B, or C," "at least one of A, B and C," "one or more of A, B, and C," and "A, B, C, or any combination thereof" may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, wherein any such combination may include one or more members of A, B, or C. All structural and functional equivalents of the elements of the various aspects described throughout the present disclosure that are or later will be known to one of ordinary skill in the art are expressly incorporated herein by reference and are intended to be covered by the claims. In addition, nothing disclosed herein is intended to be dedicated to the public, regardless of whether such disclosure is explicitly recited in the claims. Words such as "module," "mechanism," "element," "device," etc. cannot replace the word "component." Therefore, no claim element will be understood to be a part-plus-function unless the element is explicitly recited using the phrase "component for..."

Claims

1. A method for wireless communication at a user equipment (UE), the method comprising: monitoring a first radio condition of the UE for a beam of a primary cell and a second radio condition for a beam of one or more secondary cells configured for the UE in carrier aggregation; In response to the first radio condition not satisfying a first threshold and the second radio condition for at least one candidate secondary cell among the one or more secondary cells satisfying a second threshold, sending a request to configure the at least one candidate secondary cell as a candidate beam of a new primary cell; as well as A switch to the new primary cell is performed.

2. The method of claim 1, wherein the monitoring comprises performing a beam failure recovery procedure for the primary cell, wherein the UE is configured to concurrently monitor the first radio condition and the second radio condition during the beam failure recovery procedure.

3. The method of claim 1, wherein sending the request comprises sending a medium access control (MAC) control element (CE) including a reference signal identifier corresponding to the candidate beam of the at least one candidate secondary cell having a second radio condition satisfying the second threshold. 4 . The method of claim 3 , wherein sending the request comprises sending the MAC-CE on an uplink grant for the primary cell or for one of the one or more secondary cells.

5. The method of claim 1, further comprising sending an indication of the capability of the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as the new primary cell. The method of claim 1 , further comprising receiving configuration of the first threshold and the second threshold.

7. The method of claim 1, wherein sending the request is also in response to the second radio condition of the candidate beam of the at least one candidate secondary cell being greater than the first radio condition of the best beam of the primary cell by at least a third threshold.

8. The method of claim 1, wherein sending the request is further in response to a value of a configured measurement object corresponding to a neighboring cell not satisfying a fourth threshold for switching to a neighboring cell.

9. The method of claim 1, wherein performing the transition to the new primary cell comprises receiving a candidate secondary cell as a reconfiguration of the new primary cell.

10. The method of claim 1, wherein sending the request comprises sending a radio resource control (RRC) message comprising a reference signal identifier corresponding to a candidate beam of the at least one candidate secondary cell having a second radio condition satisfying the second threshold.

11. A method for wireless communication at a network entity, the method comprising: Configuring a primary cell and one or more secondary cells for a user equipment (UE) in carrier aggregation; receiving a request to configure at least one candidate secondary cell of the one or more secondary cells as a candidate beam of a new primary cell, wherein the request indicates that a first radio condition of the UE for a beam of the primary cell does not satisfy a first threshold and a second radio condition for the candidate beam of the at least one candidate secondary cell satisfies a second threshold; as well as The UE is switched to the new primary cell.

12. The method of claim 11, wherein receiving the request comprises receiving a medium access control (MAC) control element (CE) comprising a reference signal identifier corresponding to the candidate beam of the at least one candidate secondary cell having the second radio condition satisfying the second threshold. 13 . The method of claim 12 , wherein receiving the request comprises receiving the MAC-CE on an uplink grant for the primary cell or one of the one or more secondary cells.

14. The method of claim 12, wherein the MAC-CE includes a bit indicating the request for switching to the candidate beam of the at least one candidate secondary cell instead of a failure of the candidate beam.

15. The method of claim 11, further comprising receiving an indication of a capability of the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as the new primary cell. 16 . The method according to claim 11 , further comprising configuring an indication for allowing the UE to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as the new primary cell.

17. The method of claim 11, wherein receiving the request indicates that the second radio condition of the candidate beam of the at least one candidate secondary cell is greater than the first radio condition of the best beam of the primary cell by at least a third threshold.

18. The method of claim 11, wherein receiving the request indicates that a value of a configured measurement object corresponding to a neighboring cell for the UE does not satisfy a fourth threshold for transitioning to a neighboring cell.

19. The method of claim 11, wherein switching the UE to the new primary cell comprises sending a candidate secondary cell as a reconfiguration of the new primary cell.

20. The method of claim 11, wherein receiving the request comprises receiving a radio resource control (RRC) message comprising a reference signal identifier corresponding to a candidate beam of the at least one candidate secondary cell having a second radio condition satisfying the second threshold.

21. An apparatus for wireless communication of a user equipment (UE), the apparatus comprising: a memory storing computer executable instructions; and at least one processor coupled to the memory and configured to execute the computer-executable instructions so that the UE: monitoring a first radio condition of the UE for a beam of a primary cell and a second radio condition for a beam of one or more secondary cells configured for the UE in carrier aggregation; In response to the first radio condition not satisfying a first threshold and the second radio condition for at least one candidate secondary cell among the one or more secondary cells satisfying a second threshold, sending a request to configure the at least one candidate secondary cell as a candidate beam of a new primary cell; as well as A switch to the new primary cell is performed.

22. An apparatus according to claim 21, wherein in order to monitor the first radio condition and the second radio condition, the at least one processor is configured to perform a beam failure recovery process for the primary cell, and wherein the UE is configured to concurrently monitor the first radio condition and the second radio condition during the beam failure recovery process.

23. An apparatus according to claim 21, wherein in order to send the request, the at least one processor is configured to cause the UE to send a medium access control (MAC) control element (CE) including a reference signal identifier corresponding to the candidate beam of the at least one candidate secondary cell having a second radio condition that satisfies the second threshold.

24. The apparatus of claim 23, wherein to send the request, the at least one processor is configured to cause the UE to send the MAC-CE on an uplink grant for the primary cell or for one of the one or more secondary cells.

25. The apparatus of claim 21, wherein the at least one processor is configured to cause the UE to send an indication of the UE's ability to switch from the primary cell to the one or more secondary cells configured for the UE in carrier aggregation as the new primary cell.

26. The apparatus of claim 21, wherein the at least one processor is configured to cause the UE to receive configuration of the first threshold and the second threshold.

27. The apparatus of claim 21, wherein sending the request is also in response to the second radio condition of the candidate beam of the at least one candidate secondary cell being greater than the first radio condition of the best beam of the primary cell by at least a third threshold.

28. The apparatus of claim 21, wherein sending the request is further in response to a value of a configured measurement object corresponding to a neighboring cell not satisfying a fourth threshold for transitioning to a neighboring cell.

29. The apparatus of claim 21, wherein to perform the transition to the new primary cell, the at least one processor is configured to cause the UE to receive a candidate secondary cell as a reconfiguration of the new primary cell.

30. An apparatus for wireless communication of a base station, the apparatus comprising: a memory storing computer executable instructions; and at least one processor coupled to the memory and configured to execute the computer-executable instructions to cause the base station to: Configuring a primary cell and one or more secondary cells for a user equipment (UE) in carrier aggregation; receiving a request to configure at least one candidate secondary cell of the one or more secondary cells as a candidate beam of a new primary cell, wherein the request indicates that a first radio condition of the UE for a beam of the primary cell does not satisfy a first threshold and a second radio condition for the candidate beam of the at least one candidate secondary cell satisfies a second threshold; as well as The UE is switched to the new primary cell.

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