Method and apparatus for dynamic antenna array reconfiguration and signaling in millimeter wave band

Abstract

To provide dynamic antenna array reconfiguration and signaling in millimeter wave bands.SOLUTION: User equipment (UE) may detect an antenna array change condition. The UE may transmit a request for beam training for an antenna array configuration in response to the detecting. The request for beam training may include a requested antenna array configuration for the UE and an indication of beam weights to use with the requested antenna array configuration. A base station may determine whether to grant or deny the requested antenna array configuration for the UE. The UE may receive, from the base station, an indication of an antenna array configuration for the UE. The base station may transmit the number of reference signals as a set of contiguous channel state information reference signals (CSI-RS). The UE may train the reconfigured active antenna array configuration on the basis of the reference signals.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 62 / 930,409, entitled "METHODS AND APPARATUSES FOR DYNAMIC ANTENNA ARRAY RECONFIGURATION AND SIGNALING IN MILLIMETER WAVE BANDS," filed November 4, 2019, and U.S. Patent Application No. 17 / 087,410, entitled "METHODS AND APPARATUSES FOR DYNAMIC ANTENNA ARRAY RECONFIGURATION AND SIGNALING IN MILLIMETER WAVE BANDS," filed November 2, 2020, which are assigned to the assignee of this application and are incorporated by reference in their entireties herein.

[0002] The present disclosure relates generally to communication systems, and more particularly to dynamic antenna array reconfiguration and signaling in the mmWave band. [Background technology]

[0003] Wireless communication systems have been widely deployed to provide various telecommunication services, such as telephone, video, data, messaging, and broadcast. A typical wireless communication system may utilize 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.

[0004] These multiple access technologies are being adopted in various telecommunications standards to provide a common protocol that allows different wireless devices to communicate on a city, national, regional, or even global scale. An exemplary telecommunications standard is 5G New Radio (NR). 5G NR is part of the continuing mobile broadband evolution promulgated by the 3rd Generation Partnership Project (3GPP) to meet new requirements related to latency, reliability, security, scalability (e.g., with the Internet of Things (IoT)), and other requirements. 5G NR includes services related to enhanced mobile broadband (eMBB), massive machine type communications (mMTC), and ultra-reliable low latency communications (URLLC). Some aspects of 5G NR may be based on the 4G Long Term Evolution (LTE) standard. There is a need for further improvements in 5G NR technology. These improvements may also be applicable to other multiple access technologies and the telecommunications standards that employ these technologies. Summary of the Invention [Means for solving the problem]

[0005] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, nor is it intended to identify key or critical elements of all aspects or to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0006] In one aspect of the disclosure, a method, a computer-readable medium, and an apparatus (e.g., a user equipment (UE)) are provided. The method may include detecting an antenna array change condition at the UE. The method may include transmitting a request from the UE for beam training for the antenna array configuration in response to the detection. The method may include receiving an indication of the antenna array configuration for the UE from a base station.

[0007] In one aspect, the present disclosure provides an apparatus for wireless communication. The apparatus may include a memory and at least one processor coupled to the memory. The processor may be configured to detect an antenna array change condition at a UE. The processor may be configured to transmit a request from the UE for beam training for an antenna array configuration in response to the detection. The processor may be configured to receive an indication of an antenna array configuration for the UE from a base station.

[0008] In another aspect, the present disclosure provides an apparatus for wireless communications. The apparatus may include means for detecting an antenna array change condition at a UE. The apparatus may include means for transmitting a request from the UE for beam training for an antenna array configuration in response to the detection. The apparatus may include means for receiving an indication of the antenna array configuration for the UE from a base station.

[0009] In another aspect, the present disclosure provides a non-transitory computer-readable medium storing computer-executable code that, when executed by a processor, causes the processor to detect an antenna array change condition at a UE and, in response to the detection, to transmit a request from the UE for beam training for an antenna array configuration and receive from a base station an indication of the antenna array configuration for the UE.

[0010] The antenna array change condition may be based on the angular propagation of the dominant and subdominant clusters in the channel between the base station and the UE.

[0011] The antenna array change condition may be based on the power considerations of the UE.

[0012] The antenna array modification conditions may be based on thermal considerations of the UE.

[0013] The antenna array change condition may be based on support for additional radio frequency chains utilizing a hybrid beamforming architecture.

[0014] The request for beam training may include a request to change the UE's active antenna array configuration to the requested antenna array configuration.

[0015] The request for beam training may include an indication of the beam weights to be used with the requested antenna array configuration.

[0016] The representation of the beam weight may be a pointer to an analog beamforming codebook index.

[0017] The indication of the antenna array configuration for the UE may indicate a requested antenna array configuration and a number of reference signals to use for beam training with the requested antenna array configuration.

[0018] The method of wireless communication may further include configuring an antenna array based on a requested antenna array configuration to activate the reconfigured active antenna array configuration, training the reconfigured active antenna array configuration based on a reference signal, and transmitting a set of reference signal received power (RSRP) and associated beam indexes to a base station.

[0019] The indication of the antenna array configuration for the UE may indicate an active antenna array configuration.

[0020] In one aspect of the disclosure, a method, a computer-readable medium, and an apparatus (e.g., a base station) are provided. The method may include receiving a request from a UE at a base station for beam training for a requested antenna array configuration. The method may include determining whether to allow or reject the requested antenna array configuration. The method may include transmitting an indication of the antenna array configuration for the UE from the base station.

[0021] In one aspect, the present disclosure provides an apparatus for wireless communication. The apparatus may include a memory and at least one processor coupled to the memory. The processor may be configured to receive a request from a UE at a base station for beam training for a requested antenna array configuration. The processor may be configured to determine whether to allow or reject the requested antenna array configuration. The processor may be configured to transmit an indication of the antenna array configuration for the UE from the base station.

[0022] In another aspect, the present disclosure provides an apparatus for wireless communications. The apparatus may include means for receiving a request from a UE at a base station for beam training for a requested antenna array configuration. The apparatus may include means for determining whether to allow or deny the requested antenna array configuration. The apparatus may include means for transmitting an indication of the antenna array configuration for the UE from the base station.

[0023] In another aspect, the present disclosure provides a non-transitory computer-readable medium storing computer-executable code that, when executed by a processor, causes the processor to receive a request from a UE at a base station for beam training for a requested antenna array configuration, determine whether to allow or deny the requested antenna array configuration, and transmit from the base station an indication of the antenna array configuration for the UE.

[0024] A request for beam training may indicate support for additional radio frequency chains utilizing a hybrid beamforming architecture.

[0025] The request for beam training may include an indication of the beam weights to be used with the requested antenna array configuration.

[0026] The representation of the beam weight may be a pointer to an analog beamforming codebook index.

[0027] The indication of the antenna array configuration for the UE may indicate a requested antenna array configuration and a number of reference signals to use for beam training with the requested antenna array configuration.

[0028] The method of wireless communication may further include transmitting the number of reference signals as a set of contiguous channel state information reference signals (CSI-RS).

[0029] The method of wireless communication may further include receiving a set of reference signal received powers (RSRPs) and associated beam indexes from the UE, and selecting a beam from the associated beam index for transmission to the UE.

[0030] In response to a determination that the requested antenna array configuration should be rejected, the indication of the antenna array configuration for the UE may indicate the current active antenna array configuration.

[0031] To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of the various aspects may be employed and the description is intended to include all such aspects and their equivalents. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 illustrates an example of a wireless communication system and access network. [Figure 2A] A figure showing an example of a first 5G / NR frame. [Figure 2B] FIG. 1 is a diagram illustrating an example of a DL channel in a 5G / NR subframe. [Figure 2C] A figure showing an example of a second 5G / NR frame. [Figure 2D] FIG. 1 illustrates an example of a UL channel in a 5G / NR subframe. [Diagram 3] FIG. 1 illustrates an example of a base station and user equipment (UE) in an access network. [Figure 4] 1 is a schematic diagram of an example antenna array for a UE. [Figure 5A] FIG. 2 is a schematic diagram of a first exemplary active antenna configuration including a linear array. [Figure 5B] FIG. 2 is a schematic diagram of a second exemplary active antenna configuration including a planar array. [Figure 6A] FIG. 13 is a schematic diagram of a third exemplary active antenna configuration including a planar array. [Figure 6B] FIG. 11 is a schematic diagram of a fourth exemplary active antenna configuration including a linear array. [Figure 6C] FIG. 13 is a schematic diagram of a fifth exemplary active antenna configuration including a distributed linear array. [Figure 7]A conceptual diagram showing exemplary beams and transmission paths in a wireless channel. [Figure 8] FIG. 11 is a message diagram illustrating example signaling for reconfiguring a UE antenna array. [Figure 9] 4 is a flowchart of an example method for reconfiguring a UE antenna array for a UE. [Figure 10] 4 is a flowchart of an example method for a base station to reconfigure a UE antenna array. [Figure 11] FIG. 2 is a schematic diagram of example components of the UE of FIG. 1. [Figure 12] 2 is a schematic diagram of exemplary components of the base station of FIG. 1; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of various configurations and does not represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form to avoid obscuring such concepts.

[0034] 5G NR systems may operate in the millimeter wave (mmWave) band. For example, a communication system may be described based on the frequency band in which the system operates. For example, Frequency Range 1 (FR1) may refer to frequencies up to 6 GHz, FR2 may refer to frequencies between about 24 GHz and 52.6 GHz, FR3 may refer to frequencies between 6 GHz and about 24 GHz, and FR4 may refer to frequencies above 52.6 GHz.

[0035] FR4 and above systems allow more "degrees of freedom" in terms of antenna array arrangement, placement, and dynamic selection (e.g., at symbol, slot, or slot-level collections). Typically, in sub-6GHz / FR1 or FR2 systems, all antennas are used, or some fixed, pre-defined subset of antennas is used. For example, a device may include a linear antenna array, and a subset of antennas in the array may be active. Antenna configurations may be used for limited purposes, such as hierarchical beamforming, where beam changes related to subarray changes are associated with a clear mapping across antennas. In contrast, in FR4 (and beyond), any subset of antennas in a large two-dimensional array may be selectively activated at symbol or slot or slot-level collections.

[0036] The degrees of freedom are described for two hypothetical systems, the first at 30 GHz that is FR2, and the second at 120 GHz that may be considered to be FR4 or possibly beyond FR4 (e.g., "FR5"). The wavelength (λ) at 120 GHz is 1 / 4 shorter than λ at 30 GHz. Thus, for antenna array configurations at 30 GHz and 120 GHz, the same physical aperture / area may be used at both frequencies. For example, a system may include simultaneous operation at multiple carriers with flexible / collocated antenna arrays using multiple antenna feeds for different bands. For the same physical aperture at 30 GHz, four times as many antennas may be packed in each dimension (azimuth or elevation) at 120 GHz. Thus, an aperture for a 4×1 array at 30 GHz can fit into a 16×4 antenna array at 120 GHz. Thus, a medium sized antenna array (e.g., for a mobile device) can become a very large array as the carrier frequency increases.

[0037] Although antenna arrays are (relatively) low cost, they are controlled by radio frequency integrated circuits (RFICs), which may include mixers, up / down converters, power amplifiers (PAs), low noise amplifiers (LNAs), phase shifters, automatic gain control (AGC), etc. RFICs can be relatively expensive components compared to antennas in integrated antenna arrays. Due to commercial and operational tradeoffs (e.g., cost, complexity, power, die size, etc.), only a certain number of antennas may be controlled by an RFIC. Typically, the number of antennas controlled by an RFIC is between 4 and 16. However, this number can change as technology improves / changes over time. Thus, the use of large antenna arrays may require more RFICs. To control costs (both in manufacturing and in operation (e.g., energy)), only a subset of the number of RFICs required to control the entire array may be included in the device, and only a subset of the included RFICs may be activated.

[0038] In one aspect, the present disclosure dynamically switches across these degrees of freedom based on channel / link, power, thermal conditions, and key performance indicator (KPI) goals. In particular, the present disclosure communicates between the UE and the base station to select and train a new active antenna configuration, especially when the new active antenna configuration is significantly different from the previous active antenna configuration. For example, changing the subset of active antennas may be performed autonomously by the UE (to dynamically control the beamwidth of the beams used in beamforming), while adding a new active antenna may involve communication between the UE and the base station. In one implementation, the UE may detect an antenna configuration change condition that triggers the need for an antenna configuration change. An antenna configuration change condition may refer to a condition detected in the UE that indicates potential for performance improvement if the current antenna configuration is changed. The antenna configuration change condition may be based on a predicted performance for the new antenna configuration compared to the current antenna configuration. For example, the antenna configuration change condition may be based on one or more of a beamwidth change, a power or thermal consideration, or support for more RF chains with hybrid beamforming. In response to detecting the antenna configuration change condition, the UE may send a request for beam training to the base station. The request for beam training may include the requested antenna array configuration. The base station may accept or reject the antenna array configuration change request by sending a response including an indication of the antenna array configuration for the UE. If the base station accepts the requested antenna array configuration, the base station and the UE may perform beam training using a number of reference signals transmitted by the base station.

[0039] Particular implementations of the subject matter described in this disclosure may be implemented to achieve one or more of the following potential advantages: The UE may autonomously request an antenna configuration based on conditions detectable at the UE. Thus, the UE may be more likely to move quickly to an antenna configuration that meets the UE's performance goals. For example, the UE may be able to autonomously reduce power consumption or temperature as needed. A change in antenna configuration may also initiate a beam training procedure. In response, the base station may update transmit and receive beams for use with the new antenna configuration. The updated beams may be selected to provide the best signal quality.

[0040] Several aspects of a telecommunications system are now presented with respect to various apparatus and methods that are 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 particular application and design constraints imposed on the overall system.

[0041] As an example, an element or any portion of an element or any combination of elements may be implemented as a "processing system" including 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 chips (SoCs), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gate logic, discrete hardware circuits, and other suitable hardware configured to perform various functions described throughout this disclosure. 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, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, and the like, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0042] Thus, in one or more exemplary embodiments, the functions described may be implemented in hardware, software, or any combination thereof. If implemented in software, the functions may be stored on or encoded on a computer-readable medium as one or more instructions or code. Computer-readable media includes computer storage media. A 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 comprise random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the above 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.

[0043] 1 illustrates an example of a wireless communication system and 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, an evolved packet core (EPC) 160, and another core network (e.g., 5G core (5GC)) 190. The base station 102 may include a macro cell (high power cellular base station) and / or a small cell (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.

[0044] In one aspect, the UE 104 may include an antenna configuration component 140 that changes the UE's active antenna array configuration. The antenna configuration component 140 may include a plurality of antennas 141 that are arranged as an array and may be selectively activated according to the active antenna array configuration. The antenna configuration component 140 may include a condition component 142 configured to detect an antenna array configuration change condition, a request component 144 configured to transmit a request for beam training including a requested active antenna configuration, a reconfiguration component 146 configured to configure the plurality of antennas 141 according to a received antenna array configuration change response, and a training component 148 configured to perform beam training for the requested active antenna configuration.

[0045] In another aspect, the base station 102 may include an antenna control component 198 that operates in conjunction with the antenna configuration component 140. For example, as shown in Figure 12, the antenna control component 198 may include a request component 1242 configured to receive a request for beam training, an evaluation component 1244 configured to determine whether the request should be granted or denied, a configuration component 1246 configured to send an antenna array configuration change response, and a training component 1248 configured to perform beam training for the new active antenna configuration.

[0046] A base station 102 configured for 4G LTE (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface with the EPC 160 through a backhaul link 132 (e.g., an S1 interface). The backhaul link 132 may be wired or wireless.

[0047] Base stations 102 configured for 5G NR (collectively referred to as Next Generation RAN (NG-RAN)) may interface with the 5GC 190 through a backhaul link 184. The backhaul link 184 may be wired or wireless. In addition to other functions, the base stations 102 may perform one or more of the following functions: forwarding of user data, encryption and decryption of radio channels, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection setup and release, load balancing, distribution for 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 alert messages. The base stations 102 may communicate with each other directly or indirectly (e.g., through the EPC 160 or the 5GC 190) via the backhaul link 134 (e.g., an X2 interface). The backhaul link 134 may be wired or wireless.

[0048] The base stations 102 may wirelessly communicate with the UE 104. Each of the base stations 102 may provide communication coverage to a respective 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 Node B (eNB) (HeNB) that may serve restricted groups called Closed Subscriber Groups (CSGs). A communication link 120 between the base station 102 and the UE 104 may include an uplink (UL) (also referred to as a reverse link) transmission from the UE 104 to the base station 102, and / or a downlink (DL) (also referred to as a forward link) transmission from the base station 102 to the UE 104. The communication link 120 may use multiple-input multiple-output (MIMO) antenna techniques, including spatial multiplexing, beamforming, and / or transmit diversity. The communication link may be over one or more carriers. The base station 102 / UE 104 may use spectrum with bandwidth up to Y MHz (e.g., 5, 10, 15, 20, 100, 400 MHz, etc.) per carrier allocated in carrier aggregation with up to a total of Yx MHz (x component carriers) used for transmission in each direction. The carriers may or may not be adjacent to each other. The carrier allocation may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated for DL ​​than for UL). The component carriers 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).

[0049] Several UEs 104 may communicate with each other using device-to-device (D2D) communication links 158. The D2D communication links 158 may use DL / UL WWAN spectrum. The D2D communication links 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 the IEEE 802.11 standard, LTE, or NR.

[0050] The wireless communication system may further include a Wi-Fi access point (AP) 150 in communication with a Wi-Fi station (STA) 152 via a communication link 154 in the 5 GHz unlicensed frequency spectrum. When communicating in the unlicensed frequency spectrum, the STA 152 / AP 150 may perform clear channel assessment (CCA) before communicating to determine if a channel is available.

[0051] The small cell 102' may operate in a licensed and / or unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell 102' may employ NR and may use the same 5 GHz unlicensed frequency spectrum used by the Wi-Fi AP 150. A small cell 102' employing NR in the unlicensed frequency spectrum may extend coverage to and / or increase capacity of an access network.

[0052] The base station 102, whether a small cell 102' or a large cell (e.g., a macro base station), may include an eNB, a gNode B (gNB), or other type of base station. Some base stations, such as the gNB 180, may operate within one or more frequency bands in the electromagnetic spectrum.

[0053] The electromagnetic spectrum is often subdivided into various classes, bands, channels, etc. based on frequency / wavelength. In 5G NR, two initial operating bands have been identified with frequency range designations FR1 (410 MHz-7.125 GHz) and FR2 (24.25 GHz-52.6 GHz). Frequencies between FR1 and FR2 are often referred to as mid-band frequencies. Although a portion of FR1 is higher than 6 GHz, FR1 is often referred to (interchangeably) as the "sub-6 GHz" band in various documents and papers. Similar nomenclature issues may arise with respect to FR2, which is often referred to (interchangeably) as the "millimeter wave" (mmW) band in documents and papers, even though it is different from the extremely high frequency (EHF) band (30 GHz-300 GHz) identified by the International Telecommunications Union (ITU) as the "mmWave" band.

[0054] With the above aspects in mind, it should be understood that, unless otherwise specified, terms such as "sub-6 GHz" as used herein may broadly refer to frequencies that may be below 6 GHz, may be within FR1, or may include mid-band frequencies. Additionally, it should be understood that terms such as "mmWave" as used herein may broadly refer to frequencies that may include mid-band frequencies, may be within FR2, or may be within the EHF band, unless otherwise specified. Communications using mmW radio frequency bands have extremely high path loss and short distances. The mmW base station 180 may utilize beamforming 182 with the UE 104 to compensate for path loss and short distances.

[0055] 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 be in communication 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. In general, the MME 162 performs bearer and connection management. All user Internet Protocol (IP) packets are forwarded through the Serving Gateway 166, which is itself connected to the PDN Gateway 172. The PDN Gateway 172 provides UE IP address allocation as well as 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), PS streaming services, and / or other IP services. The BM-SC 170 may provide functionality for MBMS user service provisioning and delivery. The BM-SC 170 may act as an entry point for content provider MBMS transmissions and may be used to authorize and initiate MBMS bearer services in a Public Land Mobile Network (PLMN) and may be used to schedule MBMS transmissions.The MBMS gateway 168 may be used to deliver MBMS traffic to base stations 102 that belong to a Multicast Broadcast Single Frequency Network (MBSFN) area that broadcasts a particular service, and may be responsible for session management (start / stop) and collecting eMBMS-related charging information.

[0056] The 5GC 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 be in communication with a Unified Data Management (UDM) 196. The AMF 192 is a control node that handles signaling between the UE 104 and the 5GC 190. In general, the AMF 192 provides QoS flow and session management. All user Internet Protocol (IP) packets are forwarded through the UPF 195. The UPF 195 provides UE IP address allocation as well as other functions. The UPF 195 is connected to IP Services 197. The IP Services 197 may include Internet, Intranet, IP Multimedia Subsystem (IMS), PS streaming services, and / or other IP services.

[0057] A base station may also be referred to as a gNB, Node B, evolved Node B (eNB), access point, base transceiver station, radio base station, radio transceiver, transceiver function, basic service set (BSS), enhanced service set (ESS), transmit / receive point (TRP), or some other suitable terminology. The base station 102 provides an access point to the EPC 160 or 5GC 190 for the UE 104. Examples of the UE 104 include a cellular phone, a smartphone, 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 (e.g., MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a large or small cooking appliance, a health management device, an implant, a sensor / actuator, a display, or any other similar function device. Some of the UEs 104 may be referred to as IoT devices (e.g., a parking meter, a gas pump, a toaster, a vehicle, a heart monitor, etc.). The UE 104 may also be referred to as a station, mobile station, subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable terminology.

[0058] Although the following description may focus on 5G NR, the concepts described herein may be applicable to other similar domains, such as LTE, LTE-A, CDMA, GSM, and other wireless technologies.

[0059] FIG. 2A is a diagram 200 illustrating an example of a first subframe in a 5G / NR frame structure. FIG. 2B is a diagram 230 illustrating an example of a DL channel in a 5G / NR subframe. FIG. 2C is a diagram 250 illustrating an example of a second subframe in a 5G / NR frame structure. FIG. 2D is a diagram 280 illustrating an example of a UL channel in a 5G / NR subframe. The 5G / NR frame structure may be FDD, where for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated to either DL or UL, or may be TDD, where for a particular set of subcarriers (carrier system bandwidth), subframes within the set of subcarriers are dedicated to both DL and UL. In the example provided by FIG. 2A, FIG. 2C, the 5G / NR frame structure is assumed to be TDD, subframe 4 is configured with slot format 28 (with mostly DL), where D is DL, U is UL, and X is flexible for use between DL / UL, and subframe 3 is configured with slot format 34 (with mostly UL). Subframes 3, 4 are shown with slot formats 34, 28, respectively, although any particular subframe may be configured with any of the various available slot formats 0-61. Slot formats 0, 1 are all DL, UL, respectively. The other slot formats 2-61 include a mix of DL, UL, and flexible symbols. The UE is configured with the slot format through a received slot format indicator (SFI) (dynamically through DL control information (DCI) or semi-statically / statically through radio resource control (RRC) signaling). Note that the following description also applies to the 5G / NR frame structure, which is TDD.

[0060] Other wireless communication technologies may have different frame structures and / or different channels. A frame (10 ms) may be divided into 10 subframes (1 ms) of equal size. Each subframe may include one or more time slots. A subframe may also include a minislot, which may include 7, 4, or 2 symbols. Each slot may include 7 or 14 symbols depending on the slot configuration. For slot configuration 0, each slot may include 14 symbols, and for slot configuration 1, each slot may include 7 symbols. Symbols on the DL may be Cyclic Prefix (CP) OFDM (CP-OFDM) symbols. 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 called Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols) (for power-limited scenarios and limited to single stream transmission). The number of slots in a subframe is based on the slot configuration and numerology. For slot configuration 0, the different numerologies μ=0-5 allow 1, 2, 4, 8, 16, and 32 slots per subframe, respectively. For slot configuration 1, the different numerologies 0-2 allow 2, 4, and 8 slots per subframe, respectively. Thus, for slot configuration 0 and numerology μ, there are 14 symbols / slot and 2μ slots / subframe. The subcarrier spacing and symbol length / duration are functions of the numerology. The subcarrier spacing is 2 μ * may be equal to 15 kHz, where μ is a numerology 0-5. Thus, numerology μ=0 has a subcarrier spacing of 15 kHz, and numerology μ=5 has a subcarrier spacing of 480 kHz. The symbol length / duration is inversely related to the subcarrier spacing. Figures 2A-2D provide an example of slot configuration 0 with 14 symbols per slot and numerology μ=0 with 1 slot per subframe. The subcarrier spacing is 15 kHz and the symbol duration is approximately 66.7 μs.

[0061] A resource grid can be used to represent the frame structure. Each time slot contains a resource block (RB) (also called physical RB (PRB)) that spans 12 consecutive subcarriers. The resource grid is divided into multiple resource elements (RE). The number of bits carried by each RE depends on the modulation scheme.

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

[0063] FIG. 2B illustrates an example of various DL channels in a subframe of a frame. A physical downlink control channel (PDCCH) carries DCI in one or more control channel elements (CCEs), each CCE including 9 RE groups (REGs), each REG including 4 consecutive REs in an OFDM symbol. A primary synchronization signal (PSS) may be in symbol 2 of a particular subframe of a frame. The PSS is used by the UE 104 to determine subframe / symbol timing and physical layer identity. A secondary synchronization signal (SSS) may be in symbol 4 of a particular subframe of a frame. The SSS is used by the UE to determine a physical layer cell identity group number and radio frame timing. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI). Based on the PCI, the UE can determine the location of the DM-RS mentioned above. The Physical Broadcast Channel (PBCH), which carries the Master Information Block (MIB), may be logically grouped with the PSS and SSS to form the Synchronization Signal (SS) / PBCH block. The MIB provides the number of RBs in the system bandwidth and the System Frame Number (SFN). The Physical Downlink Shared Channel (PDSCH) carries user data, broadcast system information not transmitted over the PBCH, such as the System Information Block (SIB), and paging messages.

[0064] As shown in FIG. 2C, some of the REs carry DM-RS (denoted as R for one particular configuration, but other DM-RS configurations are possible) for channel estimation at the base station. The UE may transmit DM-RS for the physical uplink control channel (PUCCH) and DM-RS for the physical uplink shared channel (PUSCH). The PUSCH DM-RS may be transmitted in the first one or two symbols of the PUSCH. The PUCCH DM-RS may be transmitted in different configurations depending on whether a short or long PUCCH is transmitted and depending on the particular PUCCH format used. Although not shown, the UE may transmit a sounding reference signal (SRS). The SRS may be used by the base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

[0065] 2D shows an example of various UL channels within a subframe of a frame. The PUCCH, in one configuration, may be located as shown. The PUCCH carries uplink control information (UCI), such as scheduling requests, channel quality indicators (CQI), precoding matrix indicators (PMI), rank indicators (RI), and HARQ ACK / NACK feedback. The PUSCH carries data and may additionally be used to carry buffer status reports (BSR), power headroom reports (PHR), and / or UCI.

[0066] 3 is a block diagram of a base station 310 communicating with a UE 350 in an access network. In the DL, IP packets from the EPC 160 may be provided to a controller / processor 375. The controller / processor 375 performs Layer 3 and Layer 2 functions. 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 functions related to broadcasting of system information (e.g., MIBs, SIBs), RRC connection control (e.g., 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 functions related to header compression / decompression, security (encryption, decryption, integrity protection, integrity verification), and handover support functions; RLC layer functions related to transfer of upper layer packet data units (PDUs), error correction via 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 functions related to 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 via HARQ, priority handling, and logical channel prioritization.

[0067] The transmit (TX) processor 316 and receive (RX) processor 370 perform Layer 1 functions related to various signal processing functions. Layer 1, including the physical (PHY) layer, may include error detection on transport channels, forward error correction (FEC) coding / decoding of transport channels, interleaving, rate matching, mapping onto physical channels, modulation / demodulation of physical channels, and MIMO antenna processing (e.g., with active antenna array configurations). The TX processor 316 handles mapping to signal constellations based on various modulation schemes (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-phase shift keying (M-PSK), M-ary quadrature amplitude modulation (M-QAM)). The coded and modulated symbols may then be split into parallel streams. Each stream may then be mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and / or frequency domain, and then combined together using an inverse fast Fourier transform (IFFT) to generate a physical channel carrying a time-domain OFDM symbol stream. The OFDM stream is spatially precoded to generate multiple spatial streams. Channel estimates from a channel estimator 374 may be used to determine the coding and modulation scheme and for spatial processing. The channel estimates may be derived from a reference signal and / or channel condition feedback transmitted by the UE 350. Each spatial stream may then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX may modulate an RF carrier with a respective spatial stream for transmission.

[0068] At the UE 350, each receiver 354RX receives a signal through its respective antenna 352. Each receiver 354RX recovers information modulated onto an RF carrier and provides the information to a receive (RX) processor 356. The TX processor 368 and the RX processor 356 perform layer 1 functions related to various signal processing functions. The RX processor 356 may perform spatial processing on the information to recover any spatial streams destined for the UE 350. Multiple spatial streams may be combined into a single OFDM symbol stream by the RX processor 356 when destined for the UE 350. The RX processor 356 then converts the OFDM symbol stream from the time domain to the frequency domain using a fast Fourier transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, as well as the reference signal, are recovered and demodulated by determining the most likely signal constellation point transmitted by the base station 310. These soft decisions may be based on channel estimates calculated by the channel estimator 358. The soft decisions are then decoded and deinterleaved to recover the data and control signals originally transmitted on the physical channel by the base station 310. The data and control signals are then provided to a controller / processor 359, which performs Layer 3 and Layer 2 functions.

[0069] The controller / processor 359 can 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 performs demultiplexing between transport 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 and / or NACK protocol to support HARQ operations.

[0070] Similar to the functions described with respect to DL transmission by the base station 310, the controller / processor 359 provides RRC layer functions related to system information (e.g., MIBs, SIBs) collection, RRC connection, and measurement reporting; PDCP layer functions related to header compression / decompression and security (encryption, decryption, integrity protection, integrity verification); RLC layer functions related to transfer of upper layer PDUs, error correction via ARQ, concatenation, segmentation, and reassembly of RLC SDUs, resegmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functions related to mapping between logical channels and transport channels, multiplexing of MAC SDUs onto the TB, demultiplexing of MAC SDUs from the TB, scheduling information reporting, error correction via HARQ, priority handling, and logical channel prioritization.

[0071] Channel estimates derived by the channel estimator 358 from a reference signal or feedback transmitted by the base station 310 may be used by the TX processor 368 to select an appropriate coding and modulation scheme 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 respective spatial stream for transmission.

[0072] The UL transmission is processed at the base station 310 in a manner similar to that described with respect to the receiver functions at the UE 350. Each receiver 318RX receives a signal through its respective antenna 320. Each receiver 318RX recovers the information modulated onto the RF carrier and provides the information to the RX processor 370.

[0073] The controller / processor 375 can 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 performs demultiplexing between transport and logical channels, packet reassembly, decryption, header decompression, and control signal processing to recover IP packets from the UE 350. 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 and / or NACK protocol to support HARQ operations.

[0074] At least one of the TX processor 368, the RX processor 356, and the controller / processor 359 may be configured to perform aspects related to the antenna configuration component 140 of FIG. 1 at the UE 104. At least one of the TX processor 316, the RX processor 370, and the controller / processor 375 may be configured to perform aspects related to the antenna control component 198 of FIG. 1 at the base station 102.

[0075] Referring to FIG. 4, a schematic diagram 400 of an exemplary antenna array 410 includes multiple antennas 420 and multiple RFICs 430 (e.g., RFICs 430a, 430b, 430c, 430d). The antenna array 410 may be located in the UE 104 (e.g., as antenna 141). The antenna array 410 may include up to four RFICs 430 for controlling multiple antenna modules or antenna panels via RF switches. In the illustrated example, each RFIC 430 can control up to 16 antennas. Putting more RFICs in the UE may increase manufacturing costs. A common RFIC bank with dynamic switching across antenna modules / panels and subarrays may allow flexibility for RFICs to control multiple antennas. Complex feed line crossings are a tradeoff for flexibility. In the alternative, a 16×4 array at 120 GHz may use 8 RFICs (64 antennas / 8 antennas per RFIC) if each RFIC can control 8 antennas per RFIC.

[0076] As described in more detail below, to reduce power consumption, the antenna configuration component 140 may configure a subset of the antennas 420 as active antennas. In some scenarios, the antenna configuration component 140 may limit the number of active RFICs 430 to conserve power.

[0077] 5A, a schematic diagram 500 includes a first exemplary active antenna configuration 510 for the exemplary antenna array 410. The active antenna configuration 510 includes a 4×1 linear array of antennas 420, each controlled by an RFIC 430b. In FIG. 5B, a schematic diagram 502 includes a second exemplary active antenna configuration 520. The second exemplary active antenna configuration 520 includes a 2×2 planar array of antennas 420, each controlled by an RFIC 430b.

[0078] In one aspect, the antenna configuration component 140 may switch between a 4×1 linear array of the active antenna configuration 510 and a 2×2 planar array of the active antenna configuration 520 without loss of equivalent isotropic radiated power (EIRP). For example, the 4×1 linear array of the active antenna configuration 510 may produce a relatively wide elevation propagation and a relatively narrow azimuth propagation compared to the 2×2 planar array of the active antenna configuration 520, which may produce a relatively wide azimuth propagation and a relatively narrow elevation propagation at the same EIRP. Thus, the antenna configuration component 140 may make the appropriate angular propagation tradeoff in azimuth and elevation by changing the active antenna configuration.

[0079] 6A, 6B, and 6C, three exemplary antenna configurations 610, 620, and 630 are shown, each controlled by two RFICs 430. In a first exemplary active antenna configuration 610, RFIC 430b may control a 4×2 planar array. In a second exemplary active antenna configuration 620, RFICs 430b and 430c may control an 8×1 linear array. In a third exemplary antenna configuration 630, RFICs 430a and 430c may control a 4×2 distributed array, each with two 4×1 segments.

[0080] In one aspect, the antenna configuration component 140 may switch between the active antenna configurations 610, 620, and 630. The 4×2 array of the active antenna configuration 610 may consume less power because the array is controlled by a single RFIC 430b. The 4×2 array of the active antenna configuration 610 may still have a wider beamwidth than the active antenna configuration 510. Thus, the active antenna configuration 610 may be suitable for scenarios where the angular propagation of the dominant cluster is wider. The 8×1 array of the active antenna configuration 620 may consume more power than the active antenna configuration 610 because the array is controlled by two RFICs 430b and 430c. The active antenna configuration 620 may have a narrower beamwidth in azimuth and a wider beamwidth in elevation. Thus, the active antenna configuration 620 may be suitable for scenarios where the angular propagation of the dominant cluster is matched to the beam shape / beam pattern being produced. The 4×2 distributed array of active antenna configuration 630 may consume more power than active antenna configuration 610 because active antenna configuration 630 is controlled by two RFICs 430a and 430c. Active antenna configuration 630 may be useful with hybrid beamforming because the antennas are widely spaced and therefore uncorrelated, which allows for the use of independent data streams across each 4×1 array.

[0081] In one aspect, dynamically changing the active beam configuration when there are more degrees of freedom among the possible configurations may have a larger impact on the base station than dynamically changing a linear array. For example, without needing to change the base station beam, the UE may change the active antenna configuration among a subset of antennas in a linear array. For example, when the UE changes from a 4×1 array to a 2×1 array to a 1×1 array, the beam width may be wider. The 1×1 array is a subset of the 2×1 array, which is a subset of the 4×1 array. In contrast, with additional degrees of freedom (e.g., as in the example active antenna configurations above), the antennas of the second array may not have a relationship to the antennas of the first array. Thus, the beam widths of the different active antenna configurations may not be related. The base station may need to change its beam in response to the UE antenna array configuration or beam change. In one aspect, the base station may control the UE antenna array configuration or beam change, at least if the change results in the activation or deactivation of antennas that are not related to the previous or new configuration.

[0082] Referring to FIG. 7, a conceptual diagram 700 includes a beam 710 transmitted from a base station 102 to a UE 104. The beam 710 may be the result of various antenna configurations at the base station 102, which may typically include a large antenna array for beam steering. For example, the beam 710 may include a relatively narrow first beam 710a and a relatively wide second beam 710b. The base station 102 may control beam weights to steer the beam 710 in a particular direction. For example, a channel may include multiple paths 720 (e.g., paths 720a-720e) between the base station 102 and the UE 104. For example, if there is a line of sight between the base station 102 and the UE 104, a direct path 720c may exist. RF signals may also follow indirect paths. For example, the signal may reflect off objects such as buildings, vehicles, or windows. From the perspective of the UE 104, the signal may appear to arrive from a cluster 730. The clusters (e.g., clusters 730b-730d) may be reflected or diffracted sources of signals arriving at the UE 104. For example, cluster 730c may correspond to base station 102, and clusters 730b and 730d may correspond to objects reflecting signals in indirect paths 720b and 720d, respectively. Other paths, such as paths 720a and 720e, may not reach the UE 104 with sufficient signal strength. The UE 104 may have an active antenna configuration that generates a receive beam 740 (e.g., receive beams 740a and 740b). For example, receive beam 740a may be generated by a first active antenna configuration, and receive beam 740b may be generated by a second active antenna configuration. The UE 104 may control antenna weights to steer receive beam 740 toward one or more clusters 730. The strongest cluster may be referred to as a dominant cluster, and other clusters may be referred to as subdominant clusters.

[0083] The UE 104 may dynamically change the active antenna configuration to focus on one or more clusters. For example, the UE 104 may use the active antenna configuration that generates the receive beam 740a when cluster 730b is the dominant cluster. The UE 104 may change the active antenna configuration to generate the receive beam 740b when there are multiple strong clusters. In the case of a linear antenna array, changing between a subset of antennas may affect the beamwidth of the receive beam 740 but may not have a large effect on the direction of other dimensions of the receive beam 740. When the UE 104 has a larger antenna array with more degrees of freedom, changing the active antenna configuration may change the receive beam 740 in different dimensions. For example, the beam may expand or contract in the azimuth or elevation dimension. Thus, as the degrees of freedom in the active antenna configuration selection increase, there is a greater chance that the best beam for the base station 102 will also change.

[0084] 8 is a message diagram 800 illustrating an example process and messages for dynamically changing an active antenna configuration of a UE 104. Initially, the UE 104 may communicate a message 810 with the base station 102 according to a first antenna configuration. For example, the first antenna configuration may be a default antenna configuration, the base station 102 may configure the UE 104 with the first antenna configuration (e.g., using RRC signaling), or the first antenna configuration may be dynamically selected by the UE 104.

[0085] In process block 820, the UE 104 may detect an antenna configuration change condition. The antenna configuration change condition may be based on one or more of beam width change, power or thermal considerations, or support for more RF chains with hybrid beamforming. For example, as described above with respect to FIG. 7, the UE 104 and / or antenna configuration component 140 may determine (e.g., based on a reference signal) that a different active antenna configuration will produce a receive beam 740 that will result in better performance (e.g., greater signal strength). For example, the new active antenna configuration may obtain an angular propagation of a dominant and / or subdominant cluster in the RF channel. As another example, the UE 104 and / or antenna configuration component 140 may determine that the power consumption of a current active antenna configuration is too high (e.g., based on measured power consumption or battery charge) or that the temperature of the UE 104 or its components is too high (e.g., based on a thermal sensor). In another aspect, the UE 104 and / or the antenna configuration component 140 may determine that support for additional RF chains may be desirable, for example, if a higher data rate is required. The UE 104 and / or the antenna configuration component 140 may determine that an active antenna configuration, such as the exemplary active antenna configuration 630, may support additional RF chains to receive additional streams. The above antenna change conditions may be based on measurements performed at the UE or an internal status of the UE that may not be reported to the base station. Thus, by detecting the antenna change condition and initiating antenna array configuration changes and beam training, the UE may improve the UE's performance goals that may not be detectable by the network.

[0086] In response to detecting the antenna configuration change condition in process block 820, the UE 104 may transmit a request message 830 requesting beam training for the antenna array configuration. Beam training may refer to a process in which the UE 104 and the base station 102 communicate using various beams to select a beam for future communications. For example, the base station 102 may transmit a reference signal using various beams, and the UE may feedback the selected beam and / or actual measurements of the various beams. The request message 830 may indicate a requested antenna array configuration (e.g., one of the active antenna configurations 510, 520, 610, 620, 630). For example, the requested antenna array configuration may be based on the detected antenna array change condition. In some implementations, the request message 830 may be referred to as an antenna array configuration change request message. In one aspect, the antenna array configuration may include an indication of beam weights to be used with the requested antenna array configuration. For example, the UE 104 may select beam weights based on actual measurements of reference signals received during communications with the current antenna array configuration. For example, the beam weights may be based on a prediction of the best beam to use with the requested antenna array configuration. The beam weights may be indicated as codebook entries, for example, from a codebook defined in a standard, regulation, or signaled configuration. The request message 830 may be transmitted, for example, as an RRC configuration message or a MAC CE.

[0087] The base station 102 may decide whether to grant or reject the request message 830. For example, the base station 102 may reject the requested antenna array configuration if the base station 102 cannot support the requested antenna array configuration given the current allocation of resources (e.g., transmit antennas). The base station 102 may transmit a response message 840 indicating the antenna array configuration that the UE should use. When the base station 102 rejects the requested antenna array configuration, the response message 840 may indicate the UE's current antenna array configuration. When the base station 102 accepts the requested antenna array configuration, the response message 840 may indicate the number of reference signals to be used for beam training with the requested antenna array configuration. For example, the response message 840 may indicate the time and frequency domain resources when the various reference signals 860 are transmitted. The response message 840 may be transmitted, for example, as an RRC configuration message, a MAC CE, or a DCI.

[0088] In process block 850, the UE 104 may perform beam training for the requested antenna array configuration. That is, the UE 104 may change to the requested antenna array configuration as the new active antenna configuration. The UE 104 may measure each of the reference signals 860 using the new active antenna configuration to determine the best beam. For example, the best beam may be the beam used to transmit one of the reference signals 860 having the best reference signal received power (RSRP). The UE 104 may transmit a beam training message 870 including the beam index of the best beam and the RSRP of the best beam. In response, the base station 102 may select the best beam to use for communication with the UE 104.

[0089] 9 is a flow chart of a method 900 of wireless communication. The method 900 may be performed by a UE (e.g., the UE 104, which may include the memory 360 and may be the entire UE 104 or a component of the UE 104 such as the antenna configuration component 140, the TX processor 368, the RX processor 356, and / or the controller / processor 359). In an aspect, the method 900 may be performed in communication with a base station (e.g., the base station 102, which may include the memory 376 and may be the entire base station 102 or a component of the base station 102 such as the antenna control component 198, the TX processor 316, the RX processor 370, and / or the controller / processor 375). Optional blocks are indicated by dashed lines.

[0090] At block 910, the method 900 may include detecting an antenna array change condition at the UE. In an aspect, for example, the UE 104, the RX processor 356, and / or the controller / processor 359 may execute the antenna configuration component 140 and / or the condition component 142 to detect the antenna array change condition at the UE 104. For example, the antenna array change condition may be based on angular propagation of a dominant cluster and a subdominant cluster in a channel between the base station and the UE. For example, the UE 104 may determine that a different active antenna array configuration may generate a beam including one or more additional clusters. As another example, the antenna array change condition may be based on a power consideration (e.g., a low battery state) of the UE. As another example, the antenna array change condition may be based on a thermal consideration (e.g., a temperature exceeds a threshold) of the UE. As another example, the antenna array change condition may be based on support for an additional radio frequency chain utilizing a hybrid beamforming architecture. Thus, the UE 104, the RX processor 356, and / or the controller / processor 359 executing the antenna configuration component 140 and / or the condition component 142 may provide a means for detecting an antenna array change condition at the UE.

[0091] At block 920, the method 900 may include transmitting a request for beam training for the antenna array configuration from the UE in response to the detection. In an aspect, for example, the UE 104, the TX processor 368, and / or the controller / processor 359 may execute the antenna configuration component 140 and / or the request component 144 to transmit a request for beam training for the antenna array configuration (e.g., request message 830) from the UE in response to the detection. The request for beam training may include the requested antenna array configuration. The request for beam training may include an indication of beam weights to be used with the requested antenna array configuration. For example, the indication of beam weights may be a pointer to an analog beamforming codebook index. Thus, the UE 104, the TX processor 368, and / or the controller / processor 359 executing the antenna configuration component 140 and / or the request component 144 may provide a means for transmitting a request for beam training for the antenna array configuration from the UE in response to the detection.

[0092] At block 930, the method 900 may include receiving an indication of an antenna array configuration for the UE from a base station. In an aspect, for example, the UE 104, the RX processor 356, and / or the controller / processor 359 may execute the antenna configuration component 140 and / or the reconfiguration component 146 to receive an indication of an antenna array configuration for the UE 104 from the base station 102 (e.g., an antenna array configuration change response message 840). When the base station approves the request, the indication of the antenna array configuration for the UE may indicate the requested antenna array configuration and the number of reference signals to be used for beam training with the requested antenna array configuration. When the base station rejects the request, the indication of the antenna array configuration may indicate an active antenna array configuration. Thus, the UE 104, the RX processor 356, and / or the controller / processor 359 executing the antenna configuration component 140 and / or the reconfiguration component 146 may provide a means for receiving an indication of an antenna array configuration for the UE from the base station.

[0093] At block 940, the method 900 may optionally include configuring the antenna array of the UE based on the requested antenna array configuration to activate the reconfigured active antenna array configuration. In one aspect, for example, the UE 104, the RX processor 356, and / or the controller / processor 359 may execute the antenna configuration component 140 and / or the reconfiguration component 146 to configure the antenna array 410 of the UE 104 based on the requested antenna array configuration to activate the reconfigured active antenna array configuration. For example, the reconfiguration component 146 may control one or more of the RFICs 430 to energize the antennas 420 in the active array of the requested antenna array configuration. For example, if the active antenna array configuration 510 is selected, the RFIC 430b may energize the antennas in the linear array. As another example, if the active antenna configuration 630 is selected, the RFICs 430a and 430c may energize the antennas in the distributed planar array. Thus, the UE 104, the RX processor 356, and / or the controller / processor 359 executing the antenna configuration component 140 and / or the reconfiguration component 146 may provide means for configuring the UE's antenna array based on the requested antenna array configuration to activate the reconfigured active antenna array configuration.

[0094] At block 950, the method 900 may optionally include training the reconfigured active antenna array configuration based on the number of reference signals. In an aspect, for example, the UE 104, the RX processor 356, and / or the controller / processor 359 may execute the antenna configuration component 140 and / or the training component 148 to train the reconfigured active antenna array configuration based on the number of reference signals. Thus, the UE 104, the RX processor 356, and / or the controller / processor 359 executing the antenna configuration component 140 and / or the training component 148 may provide a means for training the reconfigured active antenna array configuration based on the number of reference signals.

[0095] At block 960, the method 900 may optionally include transmitting the set of reference signal received powers (RSRPs) and associated beam indexes to the base station. In one aspect, for example, the UE 104, the TX processor 368, and / or the controller / processor 359 may execute the antenna configuration component 140 and / or the training component 148 to transmit the reference signal received powers (RSRPs) and associated beam indexes to the base station. Thus, the UE 104, the TX processor 368, and / or the controller / processor 359 executing the antenna configuration component 140 and / or the training component 148 may provide a means for transmitting the reference signal received powers (RSRPs) and associated beam indexes to the base station. The base station 102 may utilize the RSRPs and associated beam indexes to select a beam for transmission. The UE 104 may then receive transmissions from the base station 102 using the reconfigured active antenna array configuration.

[0096] 10 is a flow chart of a method 1000 of wireless communication. The method 1000 may be performed by a base station (e.g., the base station 102, which may include the memory 376 and may be the entire base station 102 or a component of the base station 102 such as the antenna control component 198, the TX processor 316, the RX processor 370, and / or the controller / processor 375). In an aspect, the method 1000 may be performed in communication with a UE (e.g., the UE 104, which may include the memory 360 and may be the entire UE 104 or a component of the UE 104 such as the antenna configuration component 140, the TX processor 368, the RX processor 356, and / or the controller / processor 359). Optional blocks are indicated by dashed lines.

[0097] At block 1010, the method 1000 may include receiving a request from the UE at the base station to change the UE's active antenna array configuration to the requested antenna array configuration. In an aspect, for example, the base station 102, the RX processor 370, and / or the controller / processor 375 may execute the antenna control component 198 and / or the request component 1242 to receive a request from the UE 104 at the base station 102 for beam training for the requested antenna array configuration. For example, the request for beam training may indicate support for additional radio frequency chains utilizing a hybrid beamforming architecture. As another example, the request for beam training may include an indication of beam weights to be used with the requested antenna array configuration. The indication of beam weights may be a pointer to an analog beamforming codebook index. Thus, the base station 102, the RX processor 370, and / or the controller / processor 375 executing the antenna control component 198 and / or the request component 1242 may provide a means for receiving a request from the UE at the base station for beam training for the requested antenna array configuration.

[0098] At block 1020, the method 1000 may include determining whether to allow or deny the requested antenna array configuration of the UE. In an aspect, for example, the base station 102 and / or the controller / processor 375 may execute the antenna control component 198 and / or the evaluation component 1244 to determine whether to allow or deny the requested antenna array configuration of the UE. For example, the evaluation component 1244 may deny the requested antenna array configuration if the base station 102 cannot support the requested antenna array configuration given the current allocation of resources (e.g., transmit antennas). For example, the requested active antenna array configuration may require additional antennas at the base station to steer the beam. If the required antennas are in use for another UE or another frequency band, the evaluation component 1244 may deny the request. Thus, the base station 102 and / or the controller / processor 375 executing the antenna control component 198 and / or the evaluation component 1244 may provide a means for determining whether to allow or deny the requested antenna array configuration of the UE.

[0099] At block 1030, the method 1000 may include transmitting an indication of the antenna array configuration for the UE from the base station. In an aspect, for example, the base station 102, the TX processor 316, and / or the controller / processor 375 may execute the antenna control component 198 and / or the configuration component 1246 to transmit from the base station 102 the indication of the antenna array configuration for the UE. Thus, the base station 102, the TX processor 316, and / or the controller / processor 375 executing the antenna control component 198 and / or the configuration component 1246 may provide a means for transmitting from the base station the indication of the antenna array configuration for the UE.

[0100] At block 1040, the method 1000 may optionally include transmitting a number of reference signals as a set of consecutive CSI-RS. In an aspect, for example, the base station 102, the TX processor 316, and / or the controller / processor 375 may execute the antenna control component 198 and / or the training component 1248 to transmit the number of reference signals as a set of consecutive CSI-RS. Thus, the base station 102, the TX processor 316, and / or the controller / processor 375 executing the antenna control component 198 and / or the training component 1248 may provide a means for transmitting a number of reference signals as a set of consecutive CSI-RS.

[0101] At block 1050, the method 1000 may optionally include receiving the set of RSRPs and associated beam indexes from the UE. In an aspect, for example, the base station 102, the RX processor 370, and / or the controller / processor 375 may execute the antenna control component 198 and / or the training component 1248 to receive the set of RSRPs and associated beam indexes from the UE. Thus, the base station 102, the RX processor 370, and / or the controller / processor 375 executing the antenna control component 198 and / or the training component 1248 may provide a means for receiving the set of RSRPs and associated beam indexes from the UE.

[0102] At block 1060, the method 1000 may optionally include selecting a beam from the associated beam index for transmission to the UE. In an aspect, for example, the base station 102, the TX processor 316, and / or the controller / processor 375 may execute the antenna control component 198 and / or the training component 1248 to select a beam from the associated beam index for transmission to the UE. That is, the training component 1248 may determine antenna weights to be used to transmit a reference signal corresponding to the selected beam index and may use those antenna weights for future transmissions to the UE. The training component 1248 may also select a transmit power based on the RSRP. Thus, the base station 102, the RX processor 370, and / or the controller / processor 375 executing the antenna control component 198 and / or the training component 1248 may provide a means for selecting a beam from the associated beam index for transmission to the UE. The base station 102 may proceed with communication with the UE using information from the antenna array configuration and beam training for the UE.

[0103] 11, an example implementation of a UE 104 may include various components, some of which have already been described above, including one or more processors 1112 and memory 1116 and transceiver 1102 in communication via one or more buses 1144, which may operate in conjunction with a modem 1114 and an antenna configuration component 140 to enable one or more of the functions described herein related to configuring an active antenna array at the UE. Additionally, the one or more processors 1112, modem 1114, memory 1116, transceiver 1102, RF front end 1188, and one or more antennas 1165 may be configured to support voice and / or data calls (simultaneously or not) in one or more radio access technologies. The antennas 1165 may include one or more antennas, antenna elements, and / or antenna arrays.

[0104] In one aspect, the one or more processors 1112 may include a modem 1114 using one or more modem processors. Various functions related to the antenna configuration component 140 may be included in the modem 1114 and / or the processor 1112, and in one aspect may be performed by a single processor, and in other aspects different ones of the functions may be performed by a combination of two or more different processors. For example, in one aspect, the one or more processors 1112 may include any one of a modem processor, or a baseband processor, or a digital signal processor, or a transmit processor, or a receiver processor, or a transceiver processor associated with the transceiver 1102, or any combination thereof. In other aspects, some of the features of the one or more processors 1112 and / or the modem 1114 associated with the antenna configuration component 140 may be performed by the transceiver 1102.

[0105] The memory 1116 may also be configured to store data used herein and / or a local version of the application 1175, the antenna configuration component 140, and / or one or more of its subcomponents being executed by the at least one processor 1112. The memory 1116 may include any type of computer readable medium usable by the computer or the at least one processor 1112, such as random access memory (RAM), read only memory (ROM), tape, magnetic disk, optical disk, volatile memory, non-volatile memory, and any combination thereof. In one aspect, for example, the memory 1116 may be a non-transitory computer readable storage medium that stores one or more computer executable codes defining the antenna configuration component 140 and / or one or more of its subcomponents and / or data associated therewith when the UE 104 operates the at least one processor 1112 to execute the antenna configuration component 140 and / or one or more of its subcomponents.

[0106] The transceiver 1102 may include at least one receiver 1106 and at least one transmitter 1108. The receiver 1106 may include hardware, firmware, and / or software code executable by a processor to receive data, the code comprising instructions and stored in a memory (e.g., a computer-readable medium). The receiver 1106 may be, for example, a radio frequency (RF) receiver. In an aspect, the receiver 1106 may receive signals transmitted by at least one base station 102. Additionally, the receiver 1106 may process such received signals and may also obtain actual measurements of the signals, such as, but not limited to, Ec / Io, SNR, RSRP, RSSI, etc. The transmitter 1108 may include hardware, firmware, and / or software code executable by a processor to transmit data, the code comprising instructions and stored in a memory (e.g., a computer-readable medium). A suitable example of the transmitter 1108 may include, but is not limited to, an RF transmitter.

[0107] Moreover, in an aspect, the UE 104 may include an RF front end 1188 that may be in operative communication with one or more antennas 1165 and a transceiver 1102 for receiving and transmitting radio transmissions, e.g., wireless communications transmitted by at least one base station 102 or wireless transmissions transmitted by the UE 104. The RF front end 1188 may be connected to the one or more antennas 1165 and may include one or more low noise amplifiers (LNAs) 1190, one or more switches 1192, one or more power amplifiers (PAs) 1198, and one or more filters 1196 for transmitting and receiving RF signals.

[0108] In one aspect, the LNAs 1190 may amplify the received signal at a desired power level. In one aspect, each LNA 1190 may have a specified minimum and maximum gain value. In one aspect, the RF front end 1188 may use one or more switches 1192 to select a particular LNA 1190 and its specified gain value based on the desired gain value for a particular application.

[0109] Further, for example, one or more PAs 1198 may be used by the RF front end 1188 to amplify a signal for RF output at a desired output power level. In an aspect, each PA 1198 may have a specified minimum and maximum gain value. In an aspect, the RF front end 1188 may use one or more switches 1192 to select a particular PA 1198 and its specified gain value based on the desired gain value for a particular application.

[0110] Also, for example, one or more filters 1196 may be used by the RF front end 1188 to filter a received signal to obtain an input RF signal. Similarly, in an aspect, for example, each filter 1196 may be used to filter an output from a respective PA 1198 to generate an output signal for transmission. In an aspect, each filter 1196 may be connected to a particular LNA 1190 and / or PA 1198. In an aspect, the RF front end 1188 may use one or more switches 1192 to select a transmit or receive path that uses a specified filter 1196, LNA 1190, and / or PA 1198 based on a configuration as specified by the transceiver 1102 and / or processor 1112.

[0111] Thus, the transceiver 1102 may be configured to transmit and receive wireless signals through one or more antennas 1165 via the RF front end 1188. In an aspect, the transceiver 1102 may be tuned to operate at a designated frequency such that the UE 104 can communicate with, for example, one or more base stations 102, or one or more cells associated with the one or more base stations 102. In an aspect, for example, the modem 1114 may configure the transceiver 1102 to operate at a designated frequency and power level based on the UE configuration of the UE 104 and a communication protocol used by the modem 1114.

[0112] In one aspect, the modem 1114 may be a multi-band multi-mode modem capable of processing digital data and communicating with the transceiver 1102 such that digital data is sent and received using the transceiver 1102. In one aspect, the modem 1114 may be multi-band and configured to support multiple frequency bands for a particular communication protocol. In one aspect, the modem 1114 may be multi-mode and configured to support multiple operating networks and communication protocols. In one aspect, the modem 1114 may control one or more components of the UE 104 (e.g., the RF front end 1188, the transceiver 1102) to enable transmission and / or reception of signals from the network based on a specified modem configuration. In one aspect, the modem configuration may be based on the modem mode and the frequency band in use. In another aspect, the modem configuration may be based on UE configuration information associated with the UE 104 such as provided by the network during cell selection and / or cell reselection.

[0113] With reference to FIG. 12 , an example implementation of a base station 102 may include various components, some of which have already been described above, including components such as one or more processors 1212 and memories 1216 and transceivers 1202 in communication via one or more buses 1254, which may operate in conjunction with a modem 1214 and an antenna control component 198 to enable one or more of the functions described herein related to UE antenna configuration control.

[0114] The transceiver 1202, receiver 1206, transmitter 1208, one or more processors 1212, memory 1216, application 1275, bus 1254, RF front end 1288, LNA 1290, switch 1292, filter 1296, PA 1298, and one or more antennas 1265 may be the same as or similar to corresponding components of the UE 104, as described above, but may be configured or otherwise programmed for base station operation rather than UE operation.

[0115] It is understood that the particular order or hierarchy of blocks in the disclosed processes / flowcharts is illustrative of example approaches. Based on design preferences, it is understood that the particular order or hierarchy of blocks in the processes / flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in an example order, and are not limited to the particular order or hierarchy presented.

[0116] The above description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein but are to be accorded the widest scope consistent with the claim language, and reference to an element in the singular does not mean "the one and only" unless so expressly stated, but rather means "one or more." The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any aspect described herein as "exemplary" should not necessarily be construed as preferred or advantageous over other aspects. Unless otherwise expressly stated, 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" include any combination of A, B, and / or C and may include multiple As, multiple Bs, or multiple Cs. In particular, 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, where any such combination may include one or more members of A, B, or C. All structural and functional equivalents to the elements of the various embodiments described throughout this disclosure that are known or that later become known to those of skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be made public, regardless of whether such disclosure is expressly recited in the claims.Words such as "module," "mechanism," "element," "device," and the like may not be substitutes for the word "means." Thus, no claim element should be construed as a means-plus-function unless the element is expressly recited using the phrase "means for." [Explanation of symbols]

[0117] 100 Wireless communication systems and access networks 102 Base station 102' Small Cell 104 User Equipment (UE) 110 Geographic Coverage Areas 110 Coverage Area 120 Communication Links 132, 134 backhaul links 140 Antenna Components 141 Antenna 142 Conditional Components 144 Requirement Component 146 Reconstruction Components 148 Training Components 150 Wi-Fi access points (AP) 152 Wi-Fi stations (STA) 154 Communication Links 158 Device-to-Device (D2D) Communication Links 160 Evolved Packet Core (EPC) 162, 164 Mobility Management Entity (MME) 166 Serving Gateway 168 Multimedia Broadcast Multicast Service (MBMS) Gateway 170 Broadcast Multicast Service Center (BM-SC) 172 Packet Data Network (PDN) Gateway 174 Home Subscriber Server (HSS) 176 IP Services 180g Node B (gNB), mmW base station 182 Beamforming 184 backhaul links 190 Core Network 192, 193 Access and Mobility Management Function (AMF) 194 Session Management Facility (SMF) 195 User Plane Function (UPF) 196 Unified Data Management (UDM) 197 IP Services 198 Antenna Control Components 200 1st subframe 230 DL Channels 250 Second Subframe 280 UL Channel 310 base station 316 Transmit (TX) Processor 318RX Receiver 318TX Transmitter 320 Antenna 350 User Equipment (UE) 352 Antenna 354RX Receiver 354TX Transmitter 356 Receive (RX) Processor 358 Channel Estimator 359 Controller / Processor 360 Memory 368 Transmit (TX) Processor 370 Receive (RX) Processor 374 Channel Estimator 375 Controller / Processor 376 Memory 410 Antenna Array 420 Antenna 430 Radio Frequency Integrated Circuits (RFICs) 510, 520, 610, 620, 630 Active Antenna Configurations 710 Beam 720 Routes 730 Cluster 740 receiving beam 830 Request Message 840 Response Message 860 Reference Signal 870 Beam Training Message 1102 Transceiver 1106 Receiver 1108 Transmitter 1112 Processor 1114 Modem 1116 Memory 1144 Bus 1165 Antenna 1175 Applications 1188 RF Front End 1190 Low Noise Amplifier (LNA) 1192 Switch 1196 Filters 1198 Power Amplifier (PA) 1202 Transceiver 1206 Receiver 1208 Transmitter 1212 processor 1214 Modem 1216 Memory 1242 Request Component 1244 Evaluation Components 1246 Components 1248 Training Components 1254 Bus 1265 Antenna 1275 Application 1288 RF Front End 1290 Low Noise Amplifier (LNA) 1292 Switch 1296 Filter 1298 Power Amplifier (PA)

Claims

1. 1. A method of wireless communication, comprising: detecting an antenna array change condition at a user equipment (UE); transmitting, in response to the detection, a request from the UE for beam training for an antenna array configuration; receiving from a base station an indication of an antenna array configuration for the UE; A method for providing the above.

2. The method of claim 1 , wherein the antenna array change condition is based on angular propagation of a dominant cluster and a subdominant cluster in a channel between the base station and the UE.

3. The method of claim 1 , wherein the antenna array modification condition is based on power considerations of the UE.

4. The method of claim 1 , wherein the antenna array modification condition is based on thermal considerations of the UE.

5. 10. The method of claim 1, wherein the antenna array change condition is based on support for additional radio frequency chains utilizing a hybrid beamforming architecture.

6. 2. The method of claim 1, wherein the request for beam training comprises a request to change an active antenna array configuration of the UE to a requested antenna array configuration.

7. 7. The method of claim 6, wherein the request for beam training for the antenna array configuration includes an indication of beam weights to be used with the requested antenna array configuration.

8. 8. The method of claim 7, wherein the representation of a beam weight is a pointer to an analog beamforming codebook index.

9. 7. The method of claim 6, wherein the indication of the antenna array configuration for the UE indicates the requested antenna array configuration and a number of reference signals to use for beam training with the requested antenna array configuration.

10. configuring an antenna array of the UE based on the requested antenna array configuration to activate a reconfigured active antenna array configuration; training the reconfigured active antenna array configuration based on the number of reference signals; transmitting a set of reference signal received powers (RSRPs) and associated beam indices to the base station; The method of claim 9 , further comprising:

11. The method of claim 6 , wherein the indication of the antenna array configuration for the UE indicates the active antenna array configuration of the UE.

12. 1. A method of wireless communication, comprising: receiving a request from a user equipment (UE) at a base station for beam training for a requested antenna array configuration; determining whether the requested antenna array configuration should be allowed or rejected; transmitting from the base station an indication of an antenna array configuration for the UE; A method for providing the above.

13. 13. The method of claim 12, wherein the request for beam training indicates support for additional radio frequency chains utilizing a hybrid beamforming architecture.

14. 13. The method of claim 12, wherein the request for beam training includes an indication of beam weights to be used with the requested antenna array configuration.

15. 15. The method of claim 14, wherein the representation of a beam weight is a pointer to an analog beamforming codebook index.

16. 13. The method of claim 12, wherein the indication of the antenna array configuration for the UE indicates the requested antenna array configuration and a number of reference signals to use for beam training with the requested antenna array configuration.

17. 17. The method of claim 16, further comprising transmitting the number of reference signals as a set of contiguous channel state information reference signals (CSI-RS).

18. receiving a set of Reference Signal Received Powers (RSRPs) and associated beam indices from the UE; selecting a beam from the associated beam index for transmission to the UE; The method of claim 16, further comprising:

19. 13. The method of claim 12, wherein, in response to the determination that the requested antenna array configuration should be rejected, the indication of the antenna array configuration for the UE indicates a current active antenna array configuration.

20. 1. An apparatus for wireless communication, comprising: Memory, at least one processor coupled to the memory, the processor comprising: Detecting an antenna array change condition at a user equipment (UE); Responsive to the detection, transmitting a request from the UE for beam training for an antenna array configuration; configured to receive from a base station an indication of an antenna array configuration for the UE. Device.

21. 21. The apparatus of claim 20, wherein the antenna array change condition is based on angular propagation of a dominant cluster and a subdominant cluster in a channel between the base station and the UE.

22. The apparatus of claim 20 , wherein the antenna array modification condition is based on power considerations of the UE.

23. The apparatus of claim 20 , wherein the antenna array modification condition is based on thermal considerations of the UE.

24. 21. The apparatus of claim 20, wherein the antenna array change condition is based on support for additional radio frequency chains utilizing a hybrid beamforming architecture.

25. 21. The apparatus of claim 20, wherein the request for beam training comprises a request to change an active antenna array configuration of the UE to a requested antenna array configuration.

26. 26. The apparatus of claim 25, wherein the request for beam training for the antenna array configuration includes an indication of beam weights to be used with the requested antenna array configuration.

27. 27. The apparatus of claim 26, wherein the representation of a beam weight is a pointer to an analog beamforming codebook index.

28. 26. The apparatus of claim 25, wherein the indication of the antenna array configuration for the UE indicates the requested antenna array configuration and a number of reference signals to use for beam training with the requested antenna array configuration.

29. the at least one processor: configuring an antenna array of the UE based on the requested antenna array configuration to activate a reconfigured active antenna array configuration; training the reconfigured active antenna array configuration based on the number of reference signals; configured to transmit a set of Reference Signal Received Power (RSRP) and associated beam index to the base station; 29. The apparatus of claim 28.

30. 26. The apparatus of claim 25, wherein the indication of the antenna array configuration for the UE indicates the active antenna array configuration of the UE.

31. 1. An apparatus for wireless communication, comprising: Memory, at least one processor coupled to the memory, the processor comprising: receiving a request from a user equipment (UE) at a base station for beam training for a requested antenna array configuration; determining whether to allow or deny the requested antenna array configuration of the UE; configured to transmit, from the base station, an indication of an antenna array configuration for the UE. Device.

32. 32. The apparatus of claim 31, wherein the request for beam training indicates support for additional radio frequency chains utilizing a hybrid beamforming architecture.

33. 32. The apparatus of claim 31, wherein the request for beam training includes an indication of beam weights to be used with the requested antenna array configuration.

34. 34. The apparatus of claim 33, wherein the representation of a beam weight is a pointer to an analog beamforming codebook index.

35. 32. The apparatus of claim 31, wherein the indication of the antenna array configuration for the UE indicates the requested antenna array configuration and a number of reference signals to use for beam training with the requested antenna array configuration.

36. 36. The apparatus of claim 35, wherein the at least one processor is configured to transmit the number of reference signals as a set of contiguous channel state information reference signals (CSI-RS).

37. the at least one processor: receiving a set of reference signal received powers (RSRPs) and associated beam indices from the UE; and configured to select a beam from the associated beam index for transmission to the UE.

36. The apparatus of claim 35.

38. 32. The apparatus of claim 31, wherein, in response to the determination that the requested antenna array configuration should be rejected, the indication of the antenna array configuration for the UE indicates a current active antenna array configuration.

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