Two-stage linear combined channel state information feedback

Abstract

A user equipment obtains a phase rotation matrix that converts an original channel state information matrix into a rotation channel state information matrix. The user equipment determines the original channel state information matrix from measurements of reference signals transmitted by the base station. The user equipment applies the phase rotation matrix to the original channel state information matrix to generate the rotation channel state information matrix. The user equipment determines a first set of coefficients that are applied to a discrete Fourier transform basis matrix, obtaining the rotating channel state information matrix. The user equipment reports to the base station a second set of coefficients derived from the first set of coefficients.

Description

[0001] [Cross-reference to related applications]

[0002] This application claims priority to U.S. Provisional Application No. 63 / 369,389, filed on July 26, 2022, entitled “Two-Stage Linear Combination Channel State Information Feedback,” which is incorporated by reference in its entirety into this application. [Technical field]

[0003] The present disclosure relates generally to communication systems, and more particularly to techniques for compressing channel state information at user equipment. [Background technology]

[0004] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0005] Wireless communication systems are widely deployed to provide a variety of telecommunication services such as telephony, video, data, messaging, and broadcast. Typical wireless communication systems may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of these 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.

[0006] These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate at a municipal, national, regional, and even global level. An example of a telecommunication standard is 5G New Radio (NR). 5G NR is part of the continued mobile broadband evolution promoted by the 3rd Generation Partnership Project (3GPP) to meet new requirements related to latency, reliability, security, scalability (e.g., related to the Internet of Things (IoT)), and other requirements. Certain 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 apply to other multiple access technologies and the telecommunication standards that adopt them. [Summary of the invention]

[0007] The following provides a simplified summary of one or more aspects in order to provide a basic understanding of these aspects. This summary is not an extensive overview of all proposed aspects and is intended to neither identify key or critical elements of all aspects nor 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 provided later.

[0008] In one aspect of the present disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a user equipment (UE). The user equipment obtains a phase rotation matrix to convert an original channel state information matrix into a rotated channel state information matrix. The user equipment determines the original channel state information matrix based on a measurement of a reference signal transmitted by a base station. The user equipment applies the phase rotation matrix to the original channel state information matrix to generate a rotated channel state information matrix. The user equipment determines a first set of coefficients that are applied to a discrete Fourier transform (DFT) basis matrix to obtain a rotated channel state information matrix. The user equipment reports a second set of coefficients derived from the first set of coefficients to the base station.

[0009] In another aspect of the present disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a base station. The base station receives coefficients for recovering a channel state information matrix from a user equipment (UE). The base station obtains a discrete Fourier transform (DFT) basis matrix. The base station recovers a rotated channel state information matrix by applying the received coefficients to the DFT basis matrix. The base station applies a phase rotation matrix to the rotated channel state information matrix to obtain an approximate original channel state information matrix. The base station uses the approximate original channel state information matrix to perform wireless communication with the user equipment.

[0010] To achieve the above and related purposes, one or more aspects include the features particularly pointed out in the claims. The following description and the accompanying drawings set forth in detail certain specific features of one or more aspects. However, these features illustrate only a small part of several different ways of utilizing the principles of the various aspects, and this description is intended to include all such aspects and their equivalents.

Brief Description of the Drawings

[0011] Figure 1 is a schematic diagram showing an example of a wireless communication system and access network.

[0012] Figure 2 is a schematic diagram showing the communication between a base station and a user equipment in an access network.

[0013] Figure 3 An example of a logical architecture for a distributed access network is presented.

[0014] Figure 4 An example of the physical architecture of a distributed access network is shown.

[0015] Figure 5 is a schematic diagram showing an example of a downlink-centric subframe.

[0016] Figure 6 is a diagram showing an example of an uplink-centric subframe.

[0017] Figure 7 is a schematic diagram showing the communication between a base station and a user equipment.

[0018] Figure 8 is a schematic diagram showing the channel state information compression technique based on two-stage linear combination.

[0019] Fig. 9 is a diagram showing an example of a phase-rotated discrete Fourier transform basis matrix.

[0020] Fig.10 is a flow chart illustrating a method or process for channel state information matrix reporting.

[0021] Fig.11 is a flow chart showing a method or process for recovering a channel state information matrix.

[0022] Fig.12 is a schematic diagram showing an example of a hardware implementation of an apparatus employing a processing system.

[0023] Fig.13 is a schematic diagram showing an example of hardware implementation of another apparatus using a processing system. [Specific implementation method]

[0024] The following detailed description is presented in conjunction with the accompanying drawings, which is intended to describe various configurations and does not imply that these concepts can only be practiced in the described configurations. The detailed description includes specific details that are presented to provide a thorough understanding of the various concepts. However, for those familiar with the technology, these specific details are not required to practice these concepts. In some cases, in order to avoid obscuring these concepts, known structures and components are shown in block diagram form.

[0025] Several aspects of telecommunication systems will now be described with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and depicted in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as "elements"). These elements can be implemented using electronic hardware, computer software, or any combination of the two. Whether these elements are implemented as hardware or software depends on the specific application and design constraints imposed on the overall system.

[0026] For example, an element, any portion of an element, or any combination of elements may be implemented as a "processing system" that includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on chips (SoCs), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configurations for performing the various functions described herein. One or more processors in a processing system may execute software. Software should be broadly understood as instructions, instruction sets, codes, code segments, program codes, programs, subroutines, software components, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, processes, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0027] Thus, in one or more example embodiments, the functions described may be implemented in hardware, software, or any combination of the two. If implemented in software, the functions may be stored or encoded in the form of one or more instructions or codes, stored on a computer-readable medium. Computer-readable media include computer storage media. The storage medium may be any available medium that a computer can access. For example, and without limitation, such a computer-readable medium may include a random access memory (RAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, a combination 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.

[0028] Figure 1 is an example diagram showing a wireless communication system and access network 100. The wireless communication system (also referred to as a wireless wide area network (WWAN)) includes base stations 102, user equipment (UEs) 104, and a core network 160. Base stations 102 may include macro cells (high-power cellular base stations) and / or small cells (low-power cellular base stations). Macro cells include base stations. Small cells include home base stations, micro cells, and medium cells.

[0029] The base stations 102 (collectively referred to as the Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) interface with the core network 160 via a backend link 132 (e.g., an S1 interface). The base stations 102 may perform one or more of the following functions, among other functions: user data transmission, radio channel encryption and decryption, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, non-access stratum (NAS) message distribution, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), user and device tracking, RAN information management (RIM), paging, positioning, and warning messaging. The base stations 102 may communicate with each other directly or indirectly (e.g., via the core network 160) via a backend link 134 (e.g., an X2 interface). The backend link 134 may be wired or wireless.

[0030] Base stations 102 may communicate wirelessly with user equipment 104. Each base station 102 may provide communication coverage for a corresponding geographic coverage area 110. There may be overlapping geographic coverage areas 110. For example, a small base station 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 small base stations and macro base stations may be referred to as a heterogeneous network. A heterogeneous network may also include Home Evolved Node Bs (HeNBs), which may provide services to a restricted group called a closed subscriber group (CSG). The communication link 120 between the base station 102 and the user equipment 104 may include uplink (UL) (also called reverse link) transmissions from the user equipment 104 to the base station 102 and / or downlink (DL) (also called forward link) transmissions from the base station 102 to the user equipment 104. The communication link 120 may use multiple-input and multiple-output (MIMO) antenna technology, including spatial multiplexing, beamforming and / or transmit diversity. The communication link may be performed through one or more carriers. The base station 102 / user equipment 104 may use a spectrum with a bandwidth of up to Y MHz (e.g., 5, 10, 15, 20, 100 MHz), each carrier being allocated in carrier aggregation, and a total spectrum for transmission in each direction of up to Yx MHz (x component carriers). The carriers may be adjacent or non-adjacent. For DL ​​and UL, the allocation of carriers may be asymmetric (e.g., more or less carriers may be allocated for DL ​​than for UL). The component carriers may include one 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).

[0031] The wireless communication system may also include a Wi-Fi access point (AP) 150 that communicates with Wi-Fi stations (STAs) 152 in the 5 GHz unlicensed spectrum via a communication link 154. When communicating in the unlicensed spectrum, STAs 152 / AP 150 may perform a clear channel assessment (CCA) before communicating to determine whether the channel is available.

[0032] The small base station 102' can operate in licensed and / or unlicensed spectrum. When operating in the unlicensed spectrum, the small base station 102' can adopt NR and use the same 5GHz unlicensed spectrum as the Wi-Fi AP 150. The small base station 102' adopting NR in the unlicensed spectrum can enhance the coverage and / or increase the capacity of the access network.

[0033] The gNodeB (gNB) 180 can communicate with the user equipment 104 in millimeter wave (mmW) frequencies and / or near mmW frequencies. When the gNB 180 operates in mmW or near mmW frequencies, the gNB 180 can be referred to as a mmW base station. Extremely high frequency (EHF) is a part of the radio frequency in the electromagnetic spectrum. The range of EHF is 30GHz to 300GHz, and the wavelength is between 1 mm and 10 mm. The radio waves in this frequency band can be referred to as millimeter waves. Frequencies close to mmW can extend to 3GHz and have a wavelength of 100 mm. The super high frequency (SHF) band is between 3GHz and 30GHz and is also called centimeter waves. Communications using mmW / near mmW radio frequency bands have extremely high path loss and short distances. The mmW base station 180 can use beamforming 184 with the user equipment 104 to compensate for the extremely high path loss and short distance.

[0034] The core network 160 may include a Mobility Management Entity (MME) 162, other MMEs 164, a serving gateway 166, a Multimedia Broadcast Multicast Service (MBMS) gateway 168, a Broadcast Multicast Service Center (BM-SC) 170, and a Packet Data Network (PDN) gateway 172. The MME 162 may communicate with a Home Subscriber Server (HSS) 174. The MME 162 is a control node that handles signaling between the user equipment 104 and the core network 160. Typically, the MME 162 provides bearer and connection management. All user Internet Protocol (IP) packets are transmitted through the serving gateway 166, which itself is connected to the PDN gateway 172. The PDN gateway 172 provides user equipment IP address allocation and other functions. The PDN gateway 172 and the BM-SC 170 are connected to the IP service 176. The IP services 176 may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service (PSS) and / or other IP services. The BM-SC 170 may provide configuration and delivery functions for MBMS user services. The BM-SC 170 may serve as an entry point for content providers' MBMS transmissions, may be used to authorize and initiate MBMS bearer services within a public land mobile network (PLMN), and may be used to schedule MBMS transmissions. The MBMS gateway 168 may be used to distribute MBMS traffic to base stations 102 that belong to a Multicast Broadcast Single Frequency Network (MBSFN) area that broadcasts a specific service, and may be responsible for session management (start / stop) and collecting eMBMS-related billing information.

[0035] A base station may also be referred to as a gNB, Node B, evolved Node B (eNB), access point, base transceiver station, wireless base station, radio transceiver, transceiver function, basic service set (BSS), extended service set (ESS), or other appropriate terminology. Base station 102 provides an access point to core network 160 for user equipment (UE) 104. Examples of user equipment 104 include a cellular phone, a smart phone, a Session Initiation Protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., an MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, a utility meter, a gas pump, a toaster, or any other device with similar functionality. Some user equipment 104 may be referred to as IoT devices (e.g., parking meters, gas pumps, toasters, vehicles, etc.). User device 104 may also be referred to as a site, a mobile site, a subscription site, a mobile unit, a subscription unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communication device, a remote device, a mobile subscription site, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handheld device, a user agent, a mobile client, a client, or other appropriate terminology.

[0036] Figure 2 2 is a block diagram of a base station 210 communicating with a user equipment 250 in an access network. In the downlink (DL), IP packets from the core network 160 may be provided to the controller / processor 275. The controller / processor 275 implements layer 3 and layer 2 functions. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller / processor 275 provides RRC layer functions associated with broadcasting of system information (e.g., MIB, SIBs), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), measurement configuration for cross-radio access technology (RAT) mobility, and user equipment measurement reporting; PDCP layer functions associated with header compression / decompression, security (encryption, decryption, integrity protection, integrity verification), and handover support functions; RLC layer functions associated with transmission of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functions associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs to transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel priority.

[0037] The transmit (TX) processor 216 and the receive (RX) processor 270 implement layer 1 functions associated with various signal processing functions. Layer 1, including the physical (PHY) layer, may include error detection of transmission channels, forward error correction (FEC) encoding / decoding of transmission channels, interleaving, rate matching, mapping to physical channels, modulation / demodulation of physical channels, and MIMO antenna processing. The TX processor 216 processes signal constellation mapping based on various modulation schemes (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-phase shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols may then be split into parallel streams. Each stream is then 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 produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from the channel estimator 274 may be used to determine coding and modulation schemes, as well as to perform spatial processing. Channel estimates may be derived from reference signals and / or feedback of channel conditions transmitted by the user equipment 250. Each spatial stream may then be provided to a different antenna 220 via a separate transmitter 218TX. Each transmitter 218TX may modulate an RF carrier with a corresponding spatial stream for transmission.

[0038] At the user equipment 250, each receiver 254RX receives a signal through its corresponding antenna 252. Each receiver 254RX recovers the information modulated onto the RF carrier and provides the information to a receive (RX) processor 256. The transmit (TX) processor 268 and the RX processor 256 implement layer 1 functions associated with various signal processing functions. The RX processor 256 may perform spatial processing on the information to recover any spatial streams destined for the user equipment 250. If there are multiple spatial streams destined for the user equipment 250, they may be combined into a single OFDM symbol stream by the RX processor 256. The RX processor 256 then converts the OFDM symbol stream from the time domain to the frequency domain using a fast Fourier transform (FFT). The frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols and reference signals on each subcarrier are recovered and demodulated by determining the most likely signal constellation point transmitted by the base station 210. These soft decisions may be based on channel estimates calculated by the channel estimator 258. 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 210. The data and control signals are then provided to the controller / processor 259, which implements Layer 3 and Layer 2 functions.

[0039] The controller / processor 259 may be associated with a memory 260 that stores program codes and data. The memory 260 may be referred to as a computer readable medium. In the uplink (UL), the controller / processor 259 provides demultiplexing between transport and logical channels, packet reassembly, decryption, header decompression, and control signal processing to recover IP packets from the core network 160. The controller / processor 259 is also responsible for error detection using an acknowledgement (ACK) and / or negative acknowledgement (NACK) protocol to support hybrid automatic repeat request (HARQ) operations.

[0040] Similar to the downlink (DL) transmission functions of the base station 210, the controller / processor 259 provides RRC layer functions related to system information (e.g., primary information block (MIB), secondary system information blocks (SIBs)) acquisition, radio resource control (RRC) connection and measurement reporting; packet data convergence protocol (PDCP) layer functions related to header compression / decompression and security (encryption, decryption, integrity protection, integrity verification); RLC layer functions related to upper layer protocol data unit (PDUs) transmission, error correction through automatic repeat request (ARQ), connection, segmentation and reassembly of radio link control (RLC) service data units (SDUs), resegmentation of RLC data PDUs and reordering of RLC data PDUs; and medium access control (MAC) layer functions related to mapping between logical channels and transport channels, multiplexing of MAC service data units (SDUs) to transport blocks (TBs), demultiplexing MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority processing and logical channel priority.

[0041] A reference signal transmitted by the base station 210 or feedback channel estimates derived by the channel estimator 258 may be used by the TX processor 268 to select an appropriate coding and modulation scheme and facilitate spatial processing. The spatial streams generated by the TX processor 268 may be provided to different antennas 252 via separate transmitters 254TX. Each transmitter 254TX may modulate a radio frequency carrier with a corresponding spatial stream for transmission. The uplink transmission is processed in the base station 210 in a manner similar to the receive function at the UE 250. Each receiver 218RX receives the signal through its corresponding antenna 220. Each receiver 218RX recovers the information modulated onto the radio frequency carrier and provides the information to the RX processor 270.

[0042] The controller / processor 275 may be associated with a memory 276 that stores program codes and data. The memory 276 may be referred to as a computer readable medium. In the uplink, the controller / processor 275 provides demultiplexing between transports and logical channels, packet reassembly, decryption, header decompression, and control signal processing to recover IP packets from the user equipment 250. The IP packets from the controller / processor 275 may be provided to the core network 160. The controller / processor 275 is also responsible for error detection using an acknowledgement (ACK) and / or negative acknowledgement (NACK) protocol to support hybrid automatic repeat request (HARQ) operations.

[0043] New Radio (NR) may refer to a radio configured to operate according to a new air interface (e.g., a non-orthogonal frequency division multiple access (OFDMA) based air interface) or a fixed transport layer (e.g., non-Internet Protocol (IP)). NR may utilize orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) on both the uplink and downlink, and may include support for half-duplex operation using time division duplex (TDD). NR may include enhanced mobile broadband (eMBB) services for wide bandwidth (e.g., over 80 MHz), millimeter wave (for high carrier frequencies, such as 60 GHz), massive machine type communications (mMTC) (for non-backward compatible MTC technologies), and / or mission-critical ultra-reliable low latency communications (URLLC) services.

[0044] A single component carrier bandwidth may support 100 MHz. In one example, NR resource blocks (RBs) may span 12 subcarriers with a subcarrier bandwidth of 60 kHz and a duration of 0.125 ms, or a bandwidth of 15 kHz and a duration of 0.5 ms. Each radio frame may include 20 or 80 subframes (or NR slots) with a length of 10 ms. Each subframe may indicate the link direction (i.e., DL or UL) for data transmission, and the link direction may switch dynamically for each subframe. Each subframe may include DL / UL data and DL / UL control data. NR's UL and DL subframes may be as follows about Figure 5 and Figure 6 The described in more detail.

[0045] The NR radio access network (RAN) may include a central unit (CU) and distributed units (DUs). A NR base station (e.g., gNB, 5GNode B, Node B, transmission reception point (TRP), access point (AP)) may correspond to one or more base stations. NR cells may be configured as access cells (ACells) or data-only cells (DCells). For example, the RAN (e.g., a central unit or a distributed unit) may configure the cell. DCells may be cells for carrier aggregation or dual connectivity and may not be used for initial access, cell selection / reselection, or switching. In some cases, DCells may not transmit a synchronization signal (SS), and in some cases, DCells may transmit SS. The NR base station may transmit a downlink signal to the user equipment indicating the cell type. Based on the cell type indication, the user equipment may communicate with the NR base station. For example, the user equipment may determine the NR base station for cell selection, access, switching and / or measurement based on the indicated cell type.

[0046] Figure 3 An example logical architecture 300 of a distributed radio access network (RAN) is shown, in accordance with various aspects of the present disclosure. A 5G access node 306 may include an access node controller (ANC) 302. The ANC may be a central unit (CU) of the distributed RAN 300. The backend interface to the next generation core network (NG-CN) 304 may terminate at the ANC. The backend interface to adjacent next generation access nodes (NG-ANs) may terminate at the ANC. The ANC may include one or more transmission points (TRPs) 308 (which may also be referred to as base stations (BSs), NR BSs, Node Bs, 5G NBs, access points (APs) or other terms). As described above, TRPs may be used interchangeably with "cells". TRPs 308 may be a distribution unit (DU). TRPs may be connected to one ANC (ANC 302) or multiple ANCs (not shown). For example, for RAN sharing, radio as a service (RaaS), and service-specific AND deployments, the TRP may be connected to multiple ANCs. The TRP may include one or more antenna ports. TRPs can be configured to serve traffic for user equipment (UE) individually (e.g., dynamically selected) or collectively (e.g., joint transmission).

[0047] The local architecture of the distributed RAN 300 can be used to illustrate the fronthaul definition. The architecture can be defined to support fronthaul solutions across different deployment types. For example, the architecture can be based on transport network capabilities (e.g., bandwidth, latency, and / or jitter). The architecture may share features and / or components with LTE. According to aspects, the next generation access node (NG-AN) 310 may support dual connectivity with NR. The NG-AN may share a common fronthaul for LTE and NR.

[0048] The architecture may enable cooperation between TRPs 308 and between TRPs. For example, cooperation may be provisioned within a TRP and / or across TRPs via ANC 302. Depending on the aspect, an interface between TRPs may not be required / exist.

[0049] According to aspects, there may be a dynamic configuration of split logical functions in the architecture of the distributed RAN 300. PDCP, RLC, MAC protocols may be adaptively placed in the ANC or TRP.

[0050] Figure 4 An example physical architecture of a distributed RAN 400 is shown, in accordance with various aspects of the present disclosure. A centralized core network unit (C-CU) 402 may host core network functions. The C-CU may be centrally deployed. C-CU functions may be offloaded (e.g., to Advanced Wireless Services (AWS)) in an effort to handle peak capacity. A centralized RAN unit (C-RU) 404 may host one or more ANC functions. Optionally, the C-RU may host core network functions locally. The C-RU may have a distributed deployment. The C-RU may be closer to the edge of the network. A distribution unit (DU) 406 may host one or more TRPs. The DU may be located at the edge of the network and have radio frequency (RF) functions.

[0051] Figure 5 500 illustrates an example of a downlink (DL)-centric subframe. The DL-centric subframe may include a control portion 502. The control portion 502 may be present at the beginning or start of the DL-centric subframe. The control portion 502 may include various scheduling information and / or control information corresponding to various portions of the DL-centric subframe. In some configurations, the control portion 502 may be a physical downlink control channel (PDCCH), such as Figure 5 As shown. The DL-centric subframe may also include a DL data portion 504. The DL data portion 504 may sometimes be referred to as the payload of the DL-centric subframe. The DL data portion 504 may include communication resources for communicating DL data from a scheduling entity (e.g., a UE or a BS) to a subordinate entity (e.g., a UE). In some configurations, the DL data portion 504 may be a physical downlink shared channel (PDSCH).

[0052] The DL-centric subframe may also include a common uplink (UL) portion 506. Common UL portion 506 may sometimes be referred to as UL burst, common UL burst, and / or various other suitable terms. Common UL portion 506 may include feedback information corresponding to various other portions of the DL-centric subframe. For example, common UL portion 506 may include feedback information corresponding to control portion 502. Non-limiting examples of feedback information may include an ACK signal, a NACK signal, a HARQ indicator, and / or various other suitable types of information. Common UL portion 506 may include additional or alternative information, such as information related to random access channel (RACH) procedures, scheduling requests (SRs), and various other suitable types of information.

[0053] like Figure 5 As shown, the end of the DL data portion 504 may be separated in time from the beginning of the common UL portion 506. This time separation may sometimes be referred to as a gap, a guard period, a guard interval, and / or various other suitable terms. This separation provides a switching time from DL communication (e.g., a reception operation by a subordinate entity (e.g., a UE)) to UL communication (e.g., a transmission by a subordinate entity (e.g., a UE)). Those of ordinary skill in the art will appreciate that the foregoing is merely an example of a DL-centric subframe, and that alternative structures with similar characteristics may exist without necessarily departing from the aspects described herein.

[0054] Figure 6 600, illustrating an example of an uplink (UL) centric subframe. The UL centric subframe may include a control portion 602. The control portion 602 may be present at the beginning or start of the UL centric subframe. Figure 6 The control portion 602 in the above reference may be Figure 5 The control portion 502 is similar. The UL-centric subframe may also include a UL data portion 604. The UL data portion 604 may sometimes be referred to as the payload of the UL-centric subframe. The UL portion may refer to the communication resources used to communicate UL data from a subordinate entity (e.g., a UE) to a scheduling entity (e.g., a UE or a BS). In some configurations, the control portion 602 may be a physical downlink control channel (PDCCH).

[0055] like Figure 6As shown, the end of the control portion 602 may be separated in time from the beginning of the UL data portion 604. This time separation may sometimes be referred to as a gap, a guard period, a guard interval, and / or other appropriate terminology. This separation provides time for switching from downlink (DL) communications (e.g., reception operations of the scheduling entity) to uplink (UL) communications (e.g., transmissions of the scheduling entity). The UL-centric subframe may also include a common UL portion 606. Figure 6 The common UL portion 606 in the above reference may be Figure 6 The common UL portion 606 is similar. The common UL portion 606 may also include information related to a channel quality indicator (CQI), a sounding reference signal (SRSs), and various other appropriate types of information. A person skilled in the art will appreciate that the above is merely an example of a UL-centric subframe, and there may be alternative structures with similar features without necessarily departing from the aspects described herein.

[0056] In some cases, two or more slave entities (e.g., UEs) may communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relay, vehicle-to-vehicle (V2V) communications, Internet of Things (IoE) communications, Internet of Things (IoT) communications, mission-critical mesh networks, and / or various other appropriate applications. Generally, sidelink signals may refer to signal communications from one slave entity (e.g., UE1) to another slave entity (e.g., UE2) without relaying the communication through a scheduling entity (e.g., UE or BS), even though the scheduling entity may be used for scheduling and / or control purposes. In some examples, the sidelink signals may use licensed spectrum for communication (unlike wireless local area networks that typically use unlicensed spectrum).

[0057] Figure 7 700 illustrates communication between a base station 702 and a UE 704 over a channel 710. In addition, the base station 702 may transmit a spatial beam 740 over the channel 710. The channel properties of the channel 710 (i.e., the wireless communication link) are referred to as channel state information (CSI) 714. This information describes how the signal propagates from the transmitter of the base station 702 to the receiver of the UE 704 and represents the combined effects of scattering, multipath fading, the power of the signal attenuating with distance, etc. Knowing the CSI 714 at the transmitter and / or receiver allows the data transmission to be adjusted according to the current channel conditions, which is critical to achieving reliable and robust high data rate communications in multi-antenna systems. The CSI 714 typically needs to be estimated at the receiver and typically needs to be quantized and fed back to the transmitter.

[0058] The time and frequency resources used by UE704 to report CSI714 are controlled by base station 702. CSI714 may include CQI, precoding matrix indication (PMI), CSI-RS resource indication (CRI), SS block resource indication, layer indication (LI), rank indication (RI) and / or L1-RSRP measurement. For CQI, PMI, CRI, LI, RI, L1-RSRP, UE704 may be configured with multiple CSI-reportConfig report settings, CSI-ResourceConfig resource settings and one or two trigger state lists through radio resource control (RRC) signaling, indicating the resource set IDs used for channel and optional interference measurements. Each trigger state contains an associated CSI-ReportConfig.

[0059] New Radio (NR) supports three types of spatial resolution CSI: standard resolution (Type I), high resolution (Type II), and enhanced Type II (eType II). Low-resolution CSI targets SU-MIMO transmissions because it relies on the UE receiver to suppress inter-layer interference. This is possible because for a given UE, the number of receive layers is less than the number of receive antennas. For MU-MIMO transmissions, the number of receive layers is typically greater than the number of receive antennas of the UE. The base station utilizes beamforming / precoding to suppress inter-UE interference. Therefore, higher resolution CSI is required to capture more propagation paths of the channel to provide sufficient degrees of freedom at the transmitter.

[0060] UE 704 measures the spatial channel between itself and the serving base station and generates a CSI report using the CSI-RS transmitted by the base station 702 transmit antenna port. UE 704 then calculates CSI-related metrics and reports the CSI to base station 702. Using the CSI reported by all UEs, base station 702 performs link adaptation and scheduling. The goal of CSI measurement and reporting is to obtain an approximate value for the CSI. This can be achieved when the reported PMI accurately represents the dominant channel eigenvector, thereby achieving accurate beamforming.

[0061] Type II and eType IICSI provide channel information with significantly higher spatial granularity. A set of beams is reported on a wideband basis, and a set of combining coefficients is reported on a narrower band basis. The reported beams provide a set of precoding vectors, one for each layer, by linear combinations of the combining coefficients.

[0062] For Type II channel state information (Type IICSI), the combining coefficients are reported separately for each subband, although the channels of adjacent subbands usually have significant mutual correlation. It is this relatively large number of combining coefficients reported on a per-subband basis that leads to the relatively large reporting overhead of Type II channel state information. The overall precoder W that the user equipment (UE) needs to report to the base station can be expressed as the product of two matrices W = W 1 W 2 , where W 1 is the wideband precoder, W 2 is the subband precoder.

[0063] Assume that the matrix W 1 captures the long-term frequency-independent nature of the channel. Therefore, a single W is chosen 2 And reported for the entire reporting bandwidth (wideband reporting).

[0064] In contrast, suppose the matrix W 2 captures shorter-term and possibly frequency-dependent channel characteristics. Therefore, W 2 is selected and reported on a subband basis, where one subband covers a portion of the entire reporting bandwidth. In addition, extended Type II channel state information (eType IICSI) allows for improved PMI reporting at a frequency domain (FD) granularity.

[0065] W 1 The matrix selects a set of spatial beams 740 as a linear combination of W 2 The basis beam 742 is performed. This subset selection may be common across both polarizations and possibly both transmission layers. The linear combination is performed independently for each subband and across polarizations and layers to obtain the combined beam 744.

[0066] In some configurations, to reduce W 2 The feedback overhead, some partial information related to the linear combination, such as the strongest and 2L-1 wideband reference amplitudes in the 2L linear combination coefficients, and the linear combination coefficients for subband differential coding in W 2 Also included in W 1 Therefore, the amplitude component of the linear combination coefficient may include wideband and sub-band components. The phase component may be per sub-band and can be configured as QPSK or 8-PSK.

[0067] In more detail, in this example, base station 702 has an N 1 ·N 2 Cross-polarized antenna elements. N 1 is the number of rows of antenna elements. N 2 is the number of antenna elements per row. For a given layer k, the reported precoding vectors for all frequency domain units can be expressed as Where N 3 is the number of frequency domain cells to report. W 1 This is the same for all frequency domain units (wideband reporting) and for all layers.

[0068] Note that the matrix Instead of a precoding matrix that maps layers to antenna ports, there is only a set of precoding vectors (one per frequency domain element) that describe all frequency domain elements for a given layer k. Compressed matrices and frequency domain (FD) basics Size M×N 3 It consists of a set of row vectors from the discrete Fourier transform (DFT) basis and provides a 3 The frequency domain corresponds to the N covered by the CSI report. 3 Frequency domain unit, conversion to a smaller delay domain of dimension M. Linear combination coefficient matrix The size 2L×M is mapped from the smaller delay domain to the beam domain.

[0069] Figure 8 8 is a diagram 800 illustrating a CSI compression technique based on a two-stage linear combination. A user equipment 804 measures a reference signal 880 transmitted by a base station 802 over a channel 810. Based on these measurements, the user equipment 804 can determine the original precoding matrix P that needs to be fed back to the base station 802.

[0070] As mentioned above, P can be expressed as:

[0071] P=W 1 W 2 W f H

[0072] P contains N 3 precoding vectors, corresponding to N 3 sub-band. 1 Contains 2L vectors, corresponding to 2L DFT basis beams. L is the number of basis beams per polarization. In total, 2L spatial beams are selected for both polarizations. W f H N 3 subbands are mapped to M delay domains. Therefore, the above equation can be written as:

[0073]

[0074] p (i) Represents corresponding to i th Subband precoding vector, i = 0, 1, ..., N 3 -1. p (i) There are 2N 1N 2 elements. SD,j Representative th Discrete Fourier transform basis beam, j = 0, 1, ..., 2L-1. b SD,j There are 2N 1 N 2 elements. FD,k Corresponding to k th Delay domain dimension, i = 0, 1, ..., M-1. b FD,k YesN 3 elements. Therefore, W 2 is a 2L×M matrix. In addition, P can be written as:

[0075]

[0076] In addition, a j,k The set is W 2 The coefficient of is denoted as a.

[0077] In order to further reduce the reporting overhead of the channel state information, the user equipment 804 may adopt a two-stage reporting scheme. In the first stage, the user equipment 804 reports W 1 and W f H In the second stage, the user equipment 804 determines W 2 and coefficient a, and then report coefficient a.

[0078] Furthermore, in this technique, in the first stage, the pre-processing component 822 of the user equipment 804 applies a phase rotation matrix D H to the original precoding matrix P to generate a rotated precoding matrix P′.

[0079] Then, in the second stage, the rotation precoding matrix P′ is input to the PMI generation component 824. The PMI generation component 824 generates the rotation precoding matrix P′ according to the rotation precoding matrix P′ from W 1 and W f H Derived discrete Fourier transform basis matrix The coefficient of determination is a. More specifically,

[0080]

[0081] Additionally, the PMI generation component 824 may truncate small coefficients in a to generate It is expressed by the following equation.

[0082]

[0083] Then, the user equipment 804 reports to the base station 802

[0084] After receiving the coefficient reported by the user equipment 804 Then, the base station 802 uses the PMI determination component 834 to determine the approximate rotation precoding matrix as follows:

[0085]

[0086] The post-processing component 832 then applies D to the approximately rotated precoding matrix To obtain the approximate original precoding matrix

[0087]

[0088] In some configurations, the phase rotation matrix D may be selected as follows:

[0089]

[0090] In the first stage of the present technology, the base station 802 obtains long-term statistical information of the channel 810 based on the channel state information (CSI) report or uplink detection of the user equipment 804. For example, the statistical information may be the channel covariance matrix Q of the channel 810. Based on this, the base station 802 may determine the phase rotation vector based on the channel characteristics. to concentrate the energy distributed in the transform domain. The phase rotation vector θ can be determined in several ways. For example, θ can be equal to argmax θ d H Qd to maximize the beamforming gain, where θ can also be decomposed by Q = VΛV H and θ = angle (v 1 ) is found, where v 1 Represents the most important eigenvector of Q.

[0091] In particular, DW DFT can be considered as a replacement basis matrix W pDF1 (θ). Therefore,

[0092]

[0093] θ can be determined by the base station or the user equipment. In either case, θ is passed to the other party, and both parties update the linear combination codebook basis W pDFT (θ). In this example, W pDFT (θ) is a phase-rotated version of the discrete Fourier transform (DFT) basis and is an orthogonal basis. The linear combination coefficients can be obtained by vectorizing W pDFT The projection on (θ) is found. In addition, W pDFT(θ) can be used exclusively for conventional DFT and oversampled DFT basis. By properly choosing the diagonal phase in D and the phase rotation vector θ, the energy distributed in the transform domain can be concentrated to obtain Make can be efficiently represented by a small number of non-zero coefficients.

[0094] when When there is no quantization (ie, Q = I), the original precoding matrix P can be fully recovered. For the case of D = I, it will be degraded to the traditional DFT basis.

[0095] The user equipment 804 and the base station 802 need to communicate about D. Additional overhead may be generated. Since the channel statistics of the user equipment are relatively long-term measurements, they may not need to be updated very frequently. The CSI-RS resources are transmitted by the base station, and the user equipment measures the channel, determines the CSI, and uses the base station W pDFT (θ) represents CSI. The user equipment feeds back the linear combination coefficients of the custom basis. In the above example, the precoding matrix P is used as an example of a CSI matrix that the user equipment can report to the base station according to the disclosed techniques. Other CSI matrices can also be reported according to these techniques. These CSI matrices may be H (channel coefficients), H H H or the transmitter precoder. CSI-RS resources can be non-precoded and can be reused by multiple user equipments, because the user equipment-specific statistics are characterized by the codebook basis determined in the first stage. The second-stage CSI-RS resources can also be considered to be precoded for a group of user equipments with similar second-order channel statistics. Precoded CSI-RS can effectively reduce the number of resources required for user equipment measurements.

[0096] Fig. 9 FIG. 900 is a diagram illustrating an example of a phase-rotated discrete Fourier transform basis. In this simplified example, base station 802 forms a beam consisting of five beams b 1 , b 2 , b 3 , b 4, and b 5 The optimal communication beam 926 determined by the user equipment 804 to communicate with the base station 802 can be expressed as a linear combination of the discrete Fourier transform base beam 912 W=a 1 b 1 +a 2 b 2 +a 3 b 3 +a 4 b 4 .

[0097] As described above, the user equipment 804 utilizes the pre-processing component 822 to rotate the discrete Fourier transform base beam 922 to obtain the phase-rotated beam 924. The communication beam 926 can be represented using the phase-rotated beam 924 as W=a′ 2 b′ 2 +a′ 3 b′ 3 Therefore, the user equipment 804 now only reports the coefficient a′ 2 and a′ 3 The linear combination representation of the optimal beamforms (or spatial filters) can be sparser, with fewer significant coefficients, and therefore results in better compression.

[0098] The oversampled DFT basis is an implementation of the phase-rotated DFT basis, but its performance is tied to the linear array architecture assumption. Cophasing across non-colocated antenna panels / clusters is another implementation of the phase-rotated DFT basis. In fact, the phase-rotated DFT basis can be viewed as cophasing applied to each antenna.

[0099] Fig.10 1000, describing a method (process) of channel state information matrix reporting. The method may be performed by a user device (e.g., 804). In operation 1002, the user device obtains a phase rotation matrix that converts an original channel state information matrix into a rotated channel state information matrix. In operation 1004, the user device determines the original channel state information matrix based on a measurement of a reference signal transmitted by a base station. In operation 1006, the user device applies the phase rotation matrix to the original channel state information matrix to generate a rotated channel state information matrix.

[0100] In operation 1008, the user equipment determines a first set of coefficients to be applied to a discrete Fourier transform basis matrix to obtain a rotated channel state information matrix. In operation 1010, the user equipment reports a second set of coefficients derived from the first set of coefficients to the base station.

[0101] In some configurations, the channel state information matrix is ​​one of a precoding matrix or a channel matrix. In some configurations, the user equipment receives a phase rotation matrix from the base station. In some configurations, the user equipment determines the phase rotation matrix to maximize beamforming gain or by eigendecomposition and reports the phase rotation matrix to the base station. The phase rotation matrix may be reported in the first stage of a multi-stage report.

[0102] In some configurations, the user equipment determines a discrete Fourier transform basis matrix based on long-term channel statistics between the user equipment and the base station, and reports the discrete Fourier transform basis matrix to the base station. The discrete Fourier transform basis matrix may be reported in a first phase of reporting, and a second set of coefficients may be reported in a second phase of reporting that is more frequent than the first phase.

[0103] In some configurations, the user equipment truncates small coefficients in the first set of coefficients when generating the second set of coefficients. In some configurations, the second set of coefficients is the same as the first set of coefficients.

[0104] Fig.11 1100 is a flow chart describing a method (process) of channel state information matrix recovery. The method may be performed by a base station (e.g., base station 702). In operation 1102, the base station receives coefficients for recovering a channel state information matrix from a user equipment. In operation 1104, the base station obtains a discrete Fourier transform basis matrix. In operation 1106, the base station recovers a rotated channel state information matrix by applying the received coefficients to the discrete Fourier transform basis matrix.

[0105] In operation 1108, the base station applies the phase rotation matrix to the rotated channel state information matrix to obtain an approximate original channel state information matrix. In operation 1110, the base station wirelessly communicates with the user equipment using the approximate original channel state information matrix.

[0106] In some configurations, the base station transmits a phase rotation matrix to the user equipment. In some configurations, the base station determines the phase rotation matrix to maximize the beamforming gain and transmits the phase rotation matrix to the user equipment. In some configurations, the base station determines the phase rotation matrix by eigendecomposition and transmits the phase rotation matrix to the user equipment. In some configurations, the base station determines a discrete Fourier transform basis matrix based on long-term channel statistics between the user equipment and the base station and transmits the discrete Fourier transform basis matrix to the user equipment. In some configurations, the base station receives a discrete Fourier transform basis matrix from the user equipment.

[0107] Fig.121200, illustrating an example of a hardware implementation of an apparatus 1202 employing a processing system 1214. The apparatus 1202 may be a user device (e.g., user device 704). The processing system 1214 may be implemented using a bus architecture, generally represented by a bus 1224. The bus 1224 may include any number of interconnecting buses and bridges depending on the specific application and overall design constraints of the processing system 1214. The bus 1224 connects various circuits together, including one or more processors and / or hardware components, represented by one or more processors 1204, a receiving component 1264, a transmitting component 1270, a phase rotation component 1276, a CSI matrix reporting component 1278, and a computer-readable medium / memory 1206. The bus 1224 may also connect various other circuits, such as timing sources, peripherals, voltage regulators, and power management circuits.

[0108] The processing system 1214 may be connected to a transceiver 1210, which may be one or more transceivers 254. The transceiver 1210 is connected to one or more antennas 1220, which may be communication antennas 252.

[0109] The transceiver 1210 provides a means of communicating with various other devices over a transmission medium. The transceiver 1210 receives signals from one or more antennas 1220, extracts information from the received signals, and provides the extracted information to the processing system 1214, particularly the receiving component 1264. In addition, the transceiver 1210 receives information from the processing system 1214, particularly the transmitting component 1270, and generates signals to be applied to the one or more antennas 1220 based on the received information.

[0110] The processing system 1214 includes one or more processors 1204 connected to a computer-readable medium / memory 1206. The one or more processors 1204 are responsible for general processing, including executing software stored on the computer-readable medium / memory 1206. When the one or more processors 1204 execute the software, it causes the processing system 1214 to perform various functions of any specific device described above. The computer-readable medium / memory 1206 can also be used to store data that is operated by the one or more processors 1204 when executing the software. The processing system 1214 also includes at least one receiving component 1264, a transmission component 1270, a phase rotation component 1276, and a CSI matrix reporting component 1278. These components may be software components running in one or more processors 1204, resident / stored in the computer-readable medium / memory 1206, one or more hardware components connected to one or more processors 1204, or some combination of the two. The processing system 1214 can be a component of the user equipment 250 and can include a memory 260 and / or at least one TX processor 268, RX processor 256, and communication processor 259.

[0111] In one configuration, the wireless communication device 1202 includes a Fig.10 The above-mentioned means may be one or more of the above-mentioned components of the above-mentioned device 1202 and / or the processing system 1214 of the device 1202 configured to perform the functions described by the above-mentioned means.

[0112] As described above, the processing system 1214 may include the TX processor 268, the RX processor 256, and the communication processor 259. Thus, in one configuration, the above means may be the TX processor 268, the RX processor 256, and the communication processor 259 configured to perform the functions described by the above means.

[0113] Fig.13 1300, illustrating an example hardware implementation of an apparatus 1302 employing a processing system 1314. The apparatus 1302 may be a base station (e.g., base station 802). The processing system 1314 may be implemented using a bus architecture, generally represented as a bus 1324. The bus 1324 may include any number of interconnecting buses and bridges, depending on the specific application and overall design constraints of the processing system 1314. The bus 1324 connects various circuits, including one or more processors and / or hardware components, represented by one or more processors 1304, a receiving component 1364, a transmitting component 1370, a phase rotation component 1376, and a CSI matrix recovery component 1378, and a computer readable medium / memory 1306. The bus 1324 may also connect various other circuits, such as timing sources, peripherals, voltage regulators, and power management circuits, etc.

[0114] The processing system 1314 may be connected to a transceiver 1310, which may be one or more transceivers 254. The transceiver 1310 is connected to one or more antennas 1320, which may be communication antennas 220.

[0115] The transceiver 1310 provides a means of communicating with various other devices over a transmission medium. The transceiver 1310 receives signals from one or more antennas 1320, extracts information from the received signals, and provides the extracted information to the processing system 1314, particularly the receiving component 1364. In addition, the transceiver 1310 receives information from the processing system 1314, particularly the transmitting component 1370, and based on the received information, generates signals to be applied to the one or more antennas 1320.

[0116] The processing system 1314 includes one or more processors 1304 connected to a computer readable medium / memory 1306. The one or more processors 1304 are responsible for general processing, including executing software stored on the computer readable medium / memory 1306. When the one or more processors 1304 execute the software, it causes the processing system 1314 to perform various functions of any specific device described above. The computer readable medium / memory 1306 can also be used to store data that is operated by the one or more processors 1304 when executing the software. The processing system 1314 also includes at least one receiving component 1364, a transmission component 1370, a phase rotation component 1376, and a CSI matrix recovery component 1378. These components may be software components running in the one or more processors 1304, resident / stored in the computer readable medium / memory 1306, one or more hardware components connected to the one or more processors 1304, or some combination of the two. The processing system 1314 can be a component of the base station 210 and can include a memory 276 and / or at least one TX processor 216, RX processor 270, and controller / processor 275.

[0117] In one configuration, the wireless communication device 1302 includes a Fig.11 The above-mentioned means may be one or more of the above-mentioned components of the above-mentioned device 1302 and / or the processing system 1314 of the device 1302 configured to perform the functions described by the above-mentioned means.

[0118] As described above, the processing system 1314 may include the transmit processor 216, the receive processor 270, and the controller / processor 275. Therefore, in one configuration, the above means may be the transmit processor 216, the receive processor 270, and the controller / processor 275 configured to perform the functions described by the above means.

[0119] It should be understood that the specific order or hierarchy of blocks in the process / flowchart is an illustration of an exemplary method. Based on design preferences, it is understood that the specific order or hierarchy of blocks in the process / flowchart can be rearranged. In addition, some blocks can be merged or omitted. The accompanying method claims present elements of each block in an exemplary order and are not meant to be limited to the specific order or hierarchy presented.

[0120] The foregoing description is provided to enable any skilled person to practice the various aspects described herein. Various modifications of these aspects will be apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects. Therefore, the claims are not intended to be limited to the aspects shown herein, but to be given a complete scope in accordance with the language of the claims, wherein the singular reference to an element does not mean "only one", unless specifically stated, but means "one or more". The word "example" used herein means "as an example, instance or illustration". Any aspect described herein as an "example" is not necessarily understood to be superior to other aspects. Unless specifically 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 of A, multiple of B or multiple of C. Specifically, combinations such as "at least one of A, B, or C," "one or more of A, B, or C," "at least one of A, B and C," "one or more of A, B, and C," and "A, B, C, or any combination thereof" may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, wherein any such combination may contain one or more members of A, B, or C. All structural and functional equivalents of the elements of the various aspects described in the present disclosure, which are known or later become known to those skilled in the art, are hereby incorporated herein by reference and are intended to be covered by the claims. In addition, regardless of whether such disclosure is explicitly stated in the claims, nothing disclosed herein is intended to be dedicated to the public. The words "module," "mechanism," "element," "device," and the like may not be substitutes for "means." Therefore, no claim element shall be interpreted as a means containing a function unless the element is explicitly stated using the phrase "means for."

Claims

1. A wireless communication method of a user equipment (UE), comprising: Obtaining a phase rotation matrix that converts an original channel state information matrix into a rotated channel state information matrix; Determining the original channel state information matrix based on measurements of a reference signal transmitted by a base station; Applying the phase rotation matrix to the original channel state information matrix to generate the rotated channel state information matrix; Determining a first set of coefficients, the first set of coefficients being applied to a discrete Fourier transform basis matrix to obtain the rotated channel state information matrix; and A second set of coefficients derived from the first set of coefficients is reported to the base station.

2. The method of claim 1, wherein the channel state information matrix is ​​one of a precoding matrix or a channel matrix.

3. The method of claim 1, further comprising: The phase rotation matrix is ​​received from the base station.

4. The method of claim 1, further comprising: determining the phase rotation matrix to maximize beamforming gain or by eigendecomposition; and The phase rotation matrix is ​​reported to the base station.

5. The method of claim 4, further comprising: The phase rotation matrix is ​​reported to the base station in the first stage of multi-stage reporting.

6. The method of claim 1, further comprising: Determining the discrete Fourier transform basis matrix based on long-term channel statistics between the user equipment and the base station; and The discrete Fourier transform basis matrix is ​​reported to the base station.

7. The method of claim 1, wherein the discrete Fourier transform basis matrix is ​​reported to the base station in a first phase of reporting, wherein the second set of coefficients is reported to the base station in a second phase of reporting, wherein the reporting in the second phase is more frequent than the reporting in the first phase.

8. The method of claim 1, further comprising: Small coefficients in the first set of coefficients are truncated when generating the second set of coefficients.

9. The method of claim 1, wherein the second set of coefficients is the same as the first set of coefficients.

10. A wireless communication method of a base station, comprising: receiving coefficients for recovering a channel state information matrix from a user equipment; Get the discrete Fourier transform basis matrix; Recovering a rotated channel state information matrix by applying the received coefficients to the discrete Fourier transform basis matrix; Applying a phase rotation matrix to the rotated channel state information matrix to obtain an approximate original channel state information matrix; and Wireless communication is performed with the user equipment using the approximate original channel state information matrix.

11. The method of claim 10, further comprising: The phase rotation matrix is ​​transmitted to the user equipment.

12. The method of claim 10, further comprising: determining the phase rotation matrix to maximize the beamforming gain; and The phase rotation matrix is ​​transmitted to the user equipment.

13. The method of claim 10, further comprising: Determine the phase rotation matrix by eigendecomposition; and The phase rotation matrix is ​​transmitted to the user equipment.

14. The method of claim 10, further comprising: Determining the discrete Fourier transform basis matrix based on long-term channel statistics between the user equipment and the base station; and The discrete Fourier transform basis matrix is ​​transmitted to the user equipment.

15. The method of claim 10, further comprising: The discrete Fourier transform basis matrix is ​​received from the user equipment.

16. An apparatus for wireless communication, the apparatus being a user equipment, comprising: Memory; and At least one processor is connected to the memory and configured to: Obtaining a phase rotation matrix, thereby converting an original channel state information matrix into a rotated channel state information matrix; Determining the original channel state information matrix based on measurements of a reference signal transmitted by a base station; Applying the phase rotation matrix to the original channel state information matrix to generate the rotated channel state information matrix; determining a first set of coefficients to be applied to a discrete Fourier transform basis matrix to obtain the rotated channel state information matrix; and A second set of coefficients derived from the first set of coefficients is reported to the base station.

17. The apparatus of claim 16, wherein the channel state information matrix is ​​one of a precoding matrix or a channel matrix.

18. The apparatus of claim 16, wherein the at least one processor is further configured to receive the phase rotation matrix from the base station.

19. The apparatus of claim 16, wherein the at least one processor is further configured to: determining the phase rotation matrix to maximize beamforming gain or by eigendecomposition; and The phase rotation matrix is ​​reported to the base station.

20. The apparatus of claim 19, wherein the phase rotation matrix is ​​reported to the base station in a first phase of a multi-phase report.

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