Digital predistortion training procedure for large scale arrays

Abstract

This disclosure provides systems, apparatus, devices, and methods for DPD training procedures, including computer programs encoded on a storage medium. A base station can transmit signals to at least one UE for multiple iterations, through multiple transmit chains, and with DPD applied. The signals transmitted for each iteration can be transmitted using a bandwidth (BW) extended over multiple subcarriers and include pilots extended over a subset of the BW, the subcarrier size of which increases for each iteration. For each iteration, the base station can receive feedback from the at least one UE based on the transmitted signals and apply DPD to each of the multiple transmit chains based on the feedback. Therefore, the base station can transmit to one or more UEs through the multiple transmit chains and with DPD pilot signals extended over the entire BW.

Description

Technical Field

[0001] This disclosure generally relates to communication systems, and more particularly to digital predistortion (DPD) training procedures for large-scale arrays. Background Technology

[0002] Wireless communication systems are widely deployed to provide a variety of telecommunications services such as telephone, video, data, messaging, and broadcasting. Typical wireless communication systems employ multiple access technologies that enable 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.

[0003] These multiple access technologies have been adopted in various telecommunications standards to provide a common protocol enabling different wireless devices to communicate at the city, country, region, and even global levels. An example telecommunications standard is 5G New Radio (NR). 5G NR is part of the continuous evolution of mobile broadband, promulgated by the 3rd Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with the Internet of Things (IoT), and other requirements. 5G NR includes services associated with enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low latency communications (URLLC). Some aspects of 5G NR can be based on the 4G Long Term Evolution (LTE) standard. There is a need for further improvements to 5G NR technology. These improvements can also be applied to other multiple access technologies and telecommunications standards that adopt them. Summary of the Invention

[0004] The following provides a brief overview of one or more aspects to offer a basic understanding of such aspects. This overview is not an exhaustive summary of all conceived aspects, nor is it intended to identify the key or decisive elements of all aspects, nor to define 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 an introduction to the more detailed description that follows.

[0005] Transmitters used to transmit wireless signals may include components such as power amplifiers (PAs) that introduce nonlinearity into the transmitted signal. Since this distortion in the transmitted signal can affect its transmission range, digital predistortion (DPD) can be performed to linearize / cancel this nonlinearity. One type of nonlinear distortion is out-of-band (OOB) distortion, for which regulatory agencies typically require transmissions to be below a predetermined threshold. While techniques such as power back-off (BO) can be used to reduce OOB transmissions below the threshold, a significant reduction in the overall power of the transmitted signal may occur as a result of applying too much BO. Therefore, it may be desirable to train DPD procedures to transmit signals at higher power while still using up to the maximum allowed bandwidth (BW) without violating the OOB transmission protocol.

[0006] Therefore, the DPD training procedure can be performed based on an iterative process in which the DPD is repeatedly applied to a subset of bandwidth (BW) whose size increases with each iteration until the DPD is trained for the maximum permissible transmission bandwidth (BW). To perform this training procedure, the transmitter can apply bypass to the DPD to transmit a pilot with a first bandwidth subset (e.g., BW / 8), which is acknowledged to the receiver for the first iteration of the DPD training procedure. The receiver can determine coefficients associated with the distortion caused by the PA and feed these coefficients back to the transmitter for training the DPD to transmit a second pilot with a second bandwidth subset (e.g., BW / 4). The second pilot can similarly be acknowledged to the receiver for the second iteration, a second coefficient determined based on the second distortion caused by the PA, and the second coefficient is fed back to the transmitter for further training of the DPD to transmit a third pilot with a third bandwidth subset (e.g., BW / 2). The same process (e.g., for BW / 2) can be repeated until the transmitter finally trains the DPD to transmit a signal extending across the full bandwidth (BW). In this way, the signal can be transmitted at the maximum permissible BW without increasing the power BO.

[0007] In one aspect of this disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may include a memory and at least one processor coupled to the memory and configured to, for each iteration i = 1, ..., m in a plurality of iterations m, transmit through a plurality of emit (Tx) chains and apply digital predistortion (DPD). i In the case of transmitting signal S to at least one UE i Where DPD1 is the initial DPD, and for signals S = i = 1, ..., m i Each of them is transmitted over a bandwidth (BW) and included in a subset of that bandwidth BW. iThe pilot signal is extended upwards, and the BW is extended on multiple subcarriers, wherein for each iteration i, the BW... i The subcarrier size is increased. The at least one processor can, for each iteration i in the multiple iterations m, adjust the value based on the transmitted signal S. i To receive feedback F from at least one UE i And for each iteration i in these multiple iterations m, based on the received feedback F i To apply digital predistortion (DPD) to each of the multiple Tx chains i+1 Furthermore, the at least one processor can be connected via the multiple Tx chains and in the application of DPD. m+1 In the case of transmission, the signal is transmitted to one or more UEs in the downlink (DL), and the transmission in the DL includes pilot signals that extend over the entire BW.

[0008] To achieve the foregoing and related objectives, these one or more aspects include the features fully described below and specifically pointed out in the claims. Certain illustrative features of these one or more aspects are set forth in detail in the following description and accompanying drawings. However, these features merely indicate a few of the various ways in which the principles of these various aspects may be employed, and this description is intended to cover all such aspects and their equivalents. Attached Figure Description

[0009] Figure 1 This is a diagram illustrating an example of a wireless communication system and access network.

[0010] Figure 2A , 2B Figures 2C and 2D are illustrations illustrating examples of the first 5G / NR frame, the DL channel within the 5G / NR subframe, the second 5G / NR frame, and the UL channel within the 5G / NR subframe, respectively.

[0011] Figure 3 This is a diagram illustrating an example of a base station and user equipment (UE) in an access network.

[0012] Figure 4 The feedback loop used to apply DPD to the transmitting element is explained.

[0013] Figure 5 The multiple feedback loops used to apply DPD to multiple transmitting elements are explained.

[0014] Figure 6 The feedback loop from the receiver for applying DPD to the transmitting element is explained.

[0015] Figure 7 The explanation covers out-of-band (OOB) transmission for different power back-off (BO) levels.

[0016] Figure 8 The DPD training procedure was explained.

[0017] Figure 9 This is a flowchart of the base station operation method.

[0018] Figure 10 It is a conceptual data flow diagram that explains the data flow between different devices / components in the example device.

[0019] Figure 11 This is a diagram illustrating an example of the hardware implementation of a device using a processing system. Detailed Implementation

[0020] The detailed description that follows, taken in conjunction with the accompanying drawings, is intended as a description of various configurations and is not intended to represent only the configurations in which the concepts described herein can be practiced. This detailed description includes specific details to provide a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts can 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.

[0021] Several aspects of a telecommunications system will now be described with reference to various apparatuses and methods. These apparatuses and methods will be described in detail below and explained in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively, “elements”). These elements can be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system.

[0022] As an example, an element, or any part 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, system-on-a-chip (SoCs), baseband processors, field-programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionalities described throughout this disclosure. One or more processors in a processing system can execute software. Software should be broadly interpreted as instructions, instruction sets, code, code segments, program code, programs, subroutines, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description languages, or other terms.

[0023] Accordingly, in one or more example embodiments, the described functionality can be implemented in hardware, software, or any combination thereof. If implemented in software, the functionality can be stored or encoded as one or more instructions or code on a computer-readable medium. A computer-readable medium includes a computer storage medium. The storage medium can be any available medium accessible to a computer. By way of example and not limitation, such computer-readable media can include 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 computer-readable media of the foregoing types, or any other medium that can be used to store computer-executable code in the form of instructions or data structures that is accessible to a computer.

[0024] Figure 1 This is a diagram illustrating an example of a wireless communication system and access network 100. The wireless communication system (also known as a wireless wide area network (WWAN)) includes base station 102, UE 104, evolved packet core (EPC) 160, and another core network 190 (e.g., a 5G core (5GC)). Base station 102 may include macrocells (high-power cellular base stations) and / or small cells (low-power cellular base stations). Macrocells include base stations. Small cells include femtocells, picocells, and microcells.

[0025] Base station 102 configured for 4G LTE (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) can interface with EPC 160 via a first backhaul link 132 (e.g., S1 interface). Base station 102 configured for 5G NR (collectively referred to as Next Generation RAN (NG-RAN)) can interface with core network 190 via a second backhaul link 184. Among other functions, base station 102 can also perform one or more of the following functions: user data delivery, radio channel cryptography and cryptography decoding, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection establishment and release, load balancing, distribution of Non-Access Stratum (NAS) messages, NAS node selection, synchronization, Radio Access Network (RAN) sharing, Multimedia Broadcast Multicast Service (MBMS), subscriber and equipment tracking, RAN Information Management (RIM), paging, location, and delivery of alarm messages. Base stations 102 can communicate with each other directly or indirectly (e.g., via EPC 160 or core network 190) on a third backhaul link 134 (e.g., an X2 interface). The third backhaul link 134 can be wired or wireless.

[0026] Base station 102 can wirelessly communicate with UE 104. Each base station 102 can provide communication coverage for its respective geographical coverage area 110. Overlapping geographical coverage areas 110 may exist. For example, small cell 102' may have coverage areas 110' that overlap with the coverage areas 110 of one or more macro base stations 102. A network that includes both small cells and macro cells may be referred to as a heterogeneous network. The heterogeneous network may also include a Home Evolved B Node (eNB) (HeNB) that can provide services to a restricted group referred to as a Closed Subscriber Group (CSG). The communication link 120 between base station 102 and UE 104 may include uplink (UL) (also known as reverse link) transmission from UE 104 to base station 102 and / or downlink (DL) (also known as forward link) transmission from base station 102 to UE 104. The communication link 120 may use multiple-input multiple-output (MIMO) antenna technologies, including spatial multiplexing, beamforming, and / or transmit diversity. These communication links may use one or more carriers. For each carrier allocated in a total of up to Yx MHz (x component carriers) for transmission in each direction, the base station 102 / UE 104 may use a spectrum with a bandwidth of up to Y MHz (e.g., 5, 10, 15, 20, 100, 400 MHz, etc.). These carriers may or may not be adjacent to each other. The allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or fewer carriers may be allocated to DL compared to UL). Component carriers may include primary component carriers and one or more secondary component carriers. The primary component carrier may be referred to as the primary cell (PCell), and the secondary component carrier may be referred to as the secondary cell (SCell).

[0027] Some UEs 104 may communicate with each other using device-to-device (D2D) communication link 158. D2D communication link 158 may use DL / UL WWAN spectrum. D2D communication link 158 may use one or more sidelink channels, such as the Physical Sidelink Broadcast Channel (PSBCH), Physical Sidelink Discovery Channel (PSDCH), Physical Sidelink Shared Channel (PSSCH), and Physical Sidelink Control Channel (PSCCH). D2D communication can be achieved through a wide variety of wireless D2D communication systems, such as, for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE 802.11 standard, LTE, or NR.

[0028] The wireless communication system may further include a Wi-Fi access point (AP) 150 communicating with a Wi-Fi station (STA) 152 via a communication link 154 in the 5 GHz unlicensed spectrum. When communicating in the unlicensed spectrum, the STA 152 / AP 150 may perform a clear channel assessment (CCA) before communication to determine whether the channel is available.

[0029] Small cell 102' can operate in licensed and / or unlicensed spectrum. When operating in unlicensed spectrum, small cell 102' can employ NR and use the same 5 GHz unlicensed spectrum as that used by Wi-Fi AP 150. Small cell 102' employing NR in unlicensed spectrum can enhance access network coverage and / or increase access network capacity.

[0030] Whether it is a small cell 102' or a large cell (e.g., a macro base station), base station 102 may include and / or be referred to as an eNB, gB node (gNB), or another type of base station. Some base stations (such as gNB 180) may operate in conventional sub-6 GHz spectrum, millimeter wave (mmW) frequencies, and / or near-mmW frequencies to communicate with UE 104. When gNB 180 operates in mmW or near-mmW frequencies, gNB 180 may be referred to as an mmW base station. Extremely high frequency (EHF) is a portion of the electromagnetic spectrum that contains radio frequency (RF). EHF has a range of 30 GHz to 300 GHz and wavelengths between 1 mm and 10 mm. Radio waves in this band may be referred to as millimeter waves. Near-mmW can extend down to 3 GHz frequencies with a wavelength of 100 mm. Ultra-high frequency (SHF) bands extend between 3 GHz and 30 GHz, and are also referred to as centimeter waves. Communication using mmW / near-mmW radio frequency bands (e.g., 3 GHz–300 GHz) has extremely high path loss and short range. mmW base station 180 can utilize beamforming 182 with UE 104 to compensate for extremely high path loss and short range. Base station 180 and UE 104 may each include multiple antennas, such as antenna elements, antenna panels and / or antenna arrays, to facilitate beamforming.

[0031] Base station 180 may transmit beamformed signals to UE 104 in one or more transmission directions 182'. UE 104 may receive beamformed signals from base station 180 in one or more reception directions 182'. UE 104 may also transmit beamformed signals to base station 180 in one or more transmission directions. Base station 180 may receive beamformed signals from UE 104 in one or more reception directions. Base station 180 / UE 104 may perform beam training to determine the optimal reception and transmission directions for each of base station 180 / UE 104. The transmission and reception directions of base station 180 may be the same or different. The transmission and reception directions of UE 104 may be the same or different.

[0032] EPC 160 may include Mobility Management Entity (MME) 162, other MMEs 164, Serving Gateway 166, Multimedia Broadcast Multicast Service (MBMS) Gateway 168, Broadcast Multicast Service Center (BM-SC) 170, and Packet Data Network (PDN) Gateway 172. MME 162 may communicate with Home Subscriber Server (HSS) 174. MME 162 is the control node that handles signaling between UE 104 and EPC 160. Generally, MME 162 provides bearer and connection management. All user Internet Protocol (IP) packets are delivered through Serving Gateway 166, which is itself connected to PDN Gateway 172. PDN Gateway 172 provides UE IP address allocation and other functions. PDN Gateway 172 and BM-SC 170 are connected to IP Service 176. IP Service 176 may include the Internet, intranet, IP Multimedia Subsystem (IMS), PS streaming service, and / or other IP services. The BM-SC 170 provides functionality for MBMS user service provisioning and delivery. The BM-SC 170 can serve as an entry point for content provider MBMS transmissions, authorize and initiate MBMS bearer services within a Public Land Mobile Network (PLMN), and schedule MBMS transmissions. The MBMS gateway 168 can be used to distribute MBMS traffic to base station 102 within a Broadcast-Specific Service Single Frequency Network (MBSFN) area, and can be responsible for session management (start / stop) and collecting eMBMS-related billing information.

[0033] The core network 190 may include Access and Mobility Management Functions (AMF) 192, other AMFs 193, Session Management Functions (SMF) 194, and User Plane Functions (UPF) 195. AMF 192 may communicate with Unified Data Management (UDM) 196. AMF 192 is the control node that handles signaling between UE 104 and the core network 190. Generally, AMF 192 provides QoS flow and session management. All user Internet Protocol (IP) packets are transmitted through UPF 195. UPF 195 provides UE IP address allocation and other functions. UPF 195 connects to IP services 197. IP services 197 may include the Internet, intranet, IP Multimedia Subsystem (IMS), PS streaming service, and / or other IP services.

[0034] Base stations may include and / or be referred to as gNB, B-node, eNB, access point, base transceiver station, radio base station, radio transceiver, transceiver function, basic service set (BSS), extended service set (ESS), transmit / receive point (TRP), or some other suitable term. Base station 102 provides UE 104 with access to EPC 160 or core network 190. Examples of UE 104 include cellular phones, smartphones, Session Initiation Protocol (SIP) phones, laptop devices, personal digital assistants (PDAs), satellite radios, GPS devices, multimedia devices, video devices, digital audio players (e.g., MP3 players), cameras, game consoles, tablet devices, smart devices, wearable devices, vehicles, electricity meters, air pumps, large or small kitchen appliances, healthcare devices, implants, sensors / actuators, displays, or any other similar functional devices. Some UE 104 may be referred to as IoT devices (e.g., parking timers, oil pumps, ovens, vehicles, heart monitors, etc.). UE 104 may also be referred to as a station, mobile station, subscriber station, mobile unit, subscriber unit, radio unit, remote unit, mobile device, radio device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, radio terminal, remote terminal, handheld device, user agent, mobile client, client, or some other suitable term.

[0035] Refer again Figure 1 In some respects, base station 180 may be configured to transmit signals to at least one UE for each iteration of the DPD training procedure; receive feedback from the at least one UE; apply DPD based on the received feedback; and use the DPD to transmit pilot signals (198) extending over a desired bandwidth. Although the following description may focus on 5G NR, the concepts described herein are applicable to other similar fields such as LTE, LTE-A, CDMA, GSM, and other wireless technologies.

[0036] Figure 2A This is a diagram 200 illustrating an example of the first subframe within the 5G / NR frame structure. Figure 2B Figure 230 is an example illustrating the DL channel within a 5G / NR subframe. Figure 2C Figure 250 is an example illustrating the second subframe within the 5G / NR frame structure. Figure 2D Figure 280 illustrates an example of the UL channel within a 5G / NR subframe. The 5G / NR frame structure can be FDD, where, for a given set of subcarriers (carrier system bandwidth), subframes within that set are dedicated to either DL or UL; or it can be TDD, where, for a given set of subcarriers (carrier system bandwidth), subframes within that set are dedicated to both DL and UL. Figure 2A , 2C In the provided example, the 5G / NR frame structure is assumed to be TDD, where subframe 4 is configured with slot format 28 (mostly DL) and subframe 3 is configured with slot format 34 (mostly UL), where D is DL, U is UL, and X is available for flexible use between DL and UL. Although subframes 3 and 4 are shown as having slot formats 34 and 28, respectively, any particular subframe can be configured with any of the various available slot formats 0-61. Slot formats 0 and 1 are full DL and full UL, respectively. Other slot formats 2-61 include a mixture of DL, UL, and flexible symbols. The UE is configured to have a slot format via the received Slot Format Indicator (SFI) (dynamically configured via DL Control Information (DCI) or semi-statically / statically configured via Radio Resource Control (RRC) signaling). Note that the following description also applies to 5G / NR frame structures for TDD.

[0037] Other wireless communication technologies may have different frame structures and / or different channels. A frame (10 ms) can be divided into 10 equally sized subframes (1 ms). Each subframe may include one or more time slots. Subframes may also include mini-time slots, which may include 7, 4, or 2 symbols. Each time slot may include 7 or 14 symbols, depending on the time slot configuration. For time slot configuration 0, each time slot may include 14 symbols, while for time slot configuration 1, each time slot may include 7 symbols. Symbols on the DL can be Cyclic Prefix (CP) OFDM (CP-OFDM) symbols. Symbols on the UL can be CP-OFDM symbols (for high-throughput scenarios) or Discrete Fourier Transform (DFT) Extended OFDM (DFT-s-OFDM) symbols (also known as Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols) (for power-constrained scenarios; limited to single-stream transmission). The number of time slots within a subframe is based on the time slot configuration and parameter design. For slot configuration 0, different parameter designs μ of 0 to 5 allow 1, 2, 4, 8, 16, and 32 slots per subframe, respectively. For slot configuration 1, different parameter designs 0 to 2 allow 2, 4, and 8 slots per subframe, respectively. Accordingly, for slot configuration 0 and parameter design μ, there are 14 symbols per slot and 2μ slots per subframe. The subcarrier spacing and symbol length / duration vary depending on the parameter design. The subcarrier spacing can be equal to 2^μ * 15kHz, where μ is the parameter design from 0 to 5. Thus, parameter design μ = 0 has a subcarrier spacing of 15kHz, while parameter design μ = 5 has a subcarrier spacing of 480kHz. Figure 2A-2D An example is provided with a slot configuration of 0 with 14 symbols per slot and a parameter design of μ=2 with 4 slots per subframe. The slot duration is 0.25ms, the subcarrier spacing is 60kHz, and the symbol duration is approximately 16.67μs.

[0038] A resource grid can be used to represent the frame structure. Each time slot includes a resource block (RB) (also known as a physical RB (PRB)) extending 12 consecutive subcarriers. This resource grid is divided into multiple resource elements (REs). The number of bits carried by each RE depends on the modulation scheme.

[0039] like Figure 2A As explained in the text, some REs carry reference (pilot) signals (RS) for the UE. RS may include demodulated RS (DM-RS) for channel estimation at the UE (indicated as R for a particular configuration). x (where 100x is the port number, but other DM-RS configurations are possible) and Channel State Information Reference Signal (CSI-RS). RS may also include Beam Measurement RS (BRS), Beam Refinement RS (BRRS), and Phase Tracking RS (PT-RS).

[0040] Figure 2BExamples of various DL channels within a subframe of a frame are explained. The Physical Downlink Control Channel (PDCCH) carries the DCI within one or more Control Channel Elements (CCEs), each CCE comprising 9 RE Groups (REGs), each REG comprising 4 consecutive REs in OFDM symbols. The Primary Synchronization Signal (PSS) is located within symbol 2 of a specific subframe of the frame. The PSS is used by the UE 104 to determine subframe / symbol timing and physical layer identity. The Secondary Synchronization Signal (SSS) is located within symbol 4 of a specific subframe of the frame. The SSS is used by the UE to determine the physical layer cell identity group number and radio frame timing. Based on the physical layer identity and physical layer cell identity group number, the UE can determine the Physical Cell Identifier (PCI). Based on the PCI, the UE can determine the location of the aforementioned DM-RS. The Physical Broadcast Channel (PBCH) carrying the Primary Information Block (MIB) can logically group together with the PSS and SSS to form a 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 (such as System Information Blocks (SIBs)) that are not transmitted through the PBCH, and paging messages.

[0041] As in Figure 2C As explained, some REs carry DM-RS for channel estimation at the base station (indicated as R for a specific configuration, but other DM-RS configurations are possible). The UE can transmit DM-RS for the Physical Uplink Control Channel (PUCCH) and DM-RS for the Physical Uplink Shared Channel (PUSCH). The PUSCH DM-RS can be transmitted in the first or first two symbols of the PUSCH. The PUCCH DM-RS can be transmitted in different configurations depending on whether a short or long PUCCH is being transmitted and depending on the specific PUCCH format used. The UE can transmit a probe reference signal (SRS). The SRS can be transmitted in the last symbol of a subframe. The SRS can have a comb structure, and the UE can transmit the SRS on one of the combs. The SRS can be used by the base station for channel quality estimation to enable frequency-dependent scheduling on the UL.

[0042] Figure 2D Examples of various UL channels within a subframe of the explanatory frame. The PUCCH can be located as indicated in one configuration. 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 clearance reports (PHR), and / or UCI.

[0043] Figure 3 This is a block diagram showing the communication between base station 310 and UE 350 in the access network. In the DL, IP packets from EPC 160 can be provided to controller / processor 375. Controller / processor 375 implements Layer 3 and Layer 2 functionality. Layer 3 includes the Radio Resource Control (RRC) layer, and Layer 2 includes the Serving Data Adaptation Protocol (SDAP) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, and Media Access Control (MAC) layer. The controller / processor 375 provides RRC layer functionality associated with broadcasting system information (e.g., MIB, SIB), 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 of UE measurement reports; PDCP layer functionality associated with header compression / decompression, security (cryptography, cryptographic decoding, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with upper-layer packet data unit (PDU) delivery, error correction via ARQ, concatenation, segmentation and reassembly of RLC service data units (SDUs), resegmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing MAC SDUs onto transport blocks (TBs), demultiplexing MAC SDUs from TBs, scheduling information reporting, error correction via HARQ, priority handling, and logical channel priority differentiation.

[0044] Transmit (TX) processor 316 and receive (RX) processor 370 implement Layer 1 functionality associated with various signal processing functions. Layer 1, including the physical (PHY) layer, may include error detection on the transport channel, forward error correction (FEC) decoding / decoding of the transport channel, interleaving, rate matching, mapping to the physical channel, modulation / demodulation of the physical channel, and MIMO antenna processing. TX processor 316 processes the mapping to the signal constellation 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 decoded 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., a pilot) in the time and / or frequency domains, and subsequently combined 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 generate multiple spatial streams. A channel estimate from channel estimator 374 can be used to determine the coding and modulation scheme and for spatial processing. This channel estimate can be derived from a reference signal transmitted by UE 350 and / or channel condition feedback. Each spatial stream can then be provided to a different antenna 320 via a separate transmitter 318TX. Each transmitter 318TX can use the corresponding spatial stream to modulate an RF carrier for transmission.

[0045] At UE 350, each receiver 354RX receives signals via its corresponding antenna 352. Each receiver 354RX recovers the information modulated onto the RF carrier and provides this information to the receive (RX) processor 356. The TX processor 368 and RX processor 356 implement Layer 1 functionality associated with various signal processing functions. The RX processor 356 can perform spatial processing on this information to recover any spatial stream destined for UE 350. If multiple spatial streams are destined for UE 350, they can be combined by the RX processor 356 into a single OFDM symbol stream. The RX processor 356 then uses a Fast Fourier Transform (FFT) to transform the OFDM symbol stream from the time domain to the frequency domain. This frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, along with the reference signal, are recovered and demodulated by determining the signal constellation points most likely to be transmitted by base station 310. These soft decisions can be based on a channel estimate calculated by channel estimator 358. These soft decisions are then decoded and deinterleaved to recover the original data and control signals transmitted by base station 310 over the physical channel. This data and control signals are then provided to controller / processor 359, which implements layer 3 and layer 2 functionality.

[0046] The controller / processor 359 may be associated with a memory 360 that stores program code and data. The memory 360 may be referred to as a computer-readable medium. In the UL, the controller / processor 359 provides demultiplexing between transport and logical channels, packet reassembly, cipher decoding, 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 ACK and / or NACK protocols to support HARQ operation.

[0047] Similar to the functionality described in conjunction with DL transmissions performed by base station 310, controller / processor 359 provides RRC layer functionality associated with system information (e.g., MIB, SIB) capture, RRC connection, and measurement reporting; PDCP layer functionality associated with header compression / decompression and security (cryptography, cryptographic decoding, integrity protection, integrity verification); RLC layer functionality associated with upper-layer PDU delivery, 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 functionality associated with mapping between logical channels and transport channels, multiplexing MAC SDUs onto TBs, demultiplexing MAC SDUs from TBs, scheduling information reporting, error correction via HARQ, priority handling, and logical channel priority differentiation.

[0048] The channel estimate derived by the channel estimator 358 from the reference signal or feedback transmitted by the base station 310 can be used by the TX processor 368 to select an appropriate coding and modulation scheme and to facilitate spatial processing. The spatial stream generated by the TX processor 368 can be provided to different antennas 352 via separate transmitters 354TX. Each transmitter 354TX can use the corresponding spatial stream to modulate an RF carrier for transmission.

[0049] UL transmissions are processed at base station 310 in a manner similar to that described in conjunction with the receiver function at UE 350. Each receiver 318RX receives signals via its respective antenna 320. Each receiver 318RX recovers the information modulated onto the RF carrier and provides that information to the RX processor 370.

[0050] The controller / processor 375 may be associated with a memory 376 that stores program code and data. The memory 376 may be referred to as a computer-readable medium. In the UL, the controller / processor 375 provides demultiplexing between transport and logical channels, packet reassembly, cipher decoding, header decompression, and control signal processing to recover IP packets from the UE 350. 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 ACK and / or NACK protocols to support HARQ operation.

[0051] At least one of the TX processor 316, RX processor 370, and controller / processor 375 can be configured to perform operations related to... Figure 1 The 198 combines various aspects.

[0052] Wireless communication systems can be configured to share available system resources and provide various telecommunications services (e.g., telephone, video, data, messaging, broadcasting, etc.) based on multiple access technologies that support communication with multiple users (such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, TD-SCDMA, etc.). In many cases, common protocols facilitating communication with wireless devices are adopted in various telecommunications standards. For example, communication methods associated with eMBB, mMTC, and URLLC can be incorporated into the 5G NR telecommunications standard, while others can be incorporated into the 4G LTE standard. As mobile broadband technology is part of continuous evolution, further improvements in mobile broadband remain useful for the continued development of such technologies.

[0053] Figure 4-6 The feedback loop that can be used to apply DPD to the transmitted signal is explained. Efficient use of resources is generally desirable in wireless system design. However, in instances where a transmitter is configured to transmit radiated power, the transmitter may include nonlinear components such as power amplifiers that can distort the transmitted signal based on the peak-to-average power ratio (PAPR). This distortion can affect the transmission range of the transmitted signal. Therefore, a digital processor can be configured to perform DPD on the signal to be transmitted to linearize the nonlinearity of the transmitted signal caused by the power amplifier.

[0054] Nonlinear distortion can include in-band distortion and out-of-band (OOB) distortion. In-band distortion can affect link performance for mutual information exchange and / or the associated error vector magnitude (EVM). OOB distortion can cause adjacent channel interference (ACI), which corresponds to the interference of the transmitted signal on signals in adjacent channels. Depending on the application, the drawbacks caused by in-band distortion may need to be overcome. In other instances, the drawbacks caused by OOB distortion may need to be overcome, and in still other instances, the drawbacks caused by both in-band and OOB distortion may need to be overcome. Therefore, pre-distortion can be performed on the transmitted signal to counteract distortion that might otherwise be caused by the power amplifier.

[0055] In various aspects, power back-off (BO) can also be used to reduce the degree of distortion caused by power amplifiers, as this degree of distortion is variable depending on the power supplied to the power amplifier. BO refers to reducing the power at the power amplifier to a value lower than the maximum power at which the power amplifier is configured to operate when generating the output. Power BO can be used with or without DPD to reduce distortion of the transmitted signal. However, increasing power BO can lead to lower power efficiency in the PA, because the signal transmitted through a channel with more BO may be weaker than the signal transmitted through a channel with less BO. Therefore, it may be necessary to use more expensive power amplifiers in conjunction with higher power BO, or the base station may need to consume more power to communicate with the UE.

[0056] Now refer to Figure 4 Applying a digital power amplifier (DPD) to the transmitted signal based on a determined nonlinear model of the power amplifier can lead to improved PA performance / efficiency. For base stations with a small number of transmitting elements, each element can have its own radio frequency (RF) feedback loop from the power amplifier. This feedback can be used to determine the nonlinear model of the power amplifier based on the analog and digital hardware included in the feedback loop.

[0057] Figure 400 illustrates at 402 the application of a digital power equalization (DPD) to the digital portion of the signal to be transmitted. After the DPD has been applied to the digital portion of the signal, it can be converted into an analog signal at 404. The analog signal from 404 can be provided to a power amplifier 406, which outputs the analog signal as the transmitted signal. Feedback from the transmitted signal can be received by an analog-to-digital converter 408 configured to perform linear equalization on the feedback. Nonlinear characteristics resulting from the operation of the power amplifier can be identified based on the feedback from the transmitted signal for applying the DPD to the digital portion of the signal at 402. The adjustment of the digital signal and the application of the DPD at 402 reduce distortion, thereby allowing the overall power output (BO) to be maintained at a low value (e.g., high total power can be supplied to the power amplifier). Although distortion based on the application of the DPD may not be completely eliminated, the efficiency of the power amplifier can be improved by maintaining a smaller BO using the DPD.

[0058] Now refer to Figure 5 The plurality of transmitting elements / antennas may include a first transmitting element 500 to an Nth transmitting element 550. While a DPD may be applied individually to each transmitting element to cancel the distortion caused by each of the respective power amplifiers (e.g., power amplifier 1 to power amplifier N), the signal transmitted through the channel is received together at the receiver as a signal combination. Therefore, applying a DPD on an element-by-element basis may not be optimal, because the receiver receives the transmitted signal as a combination of signals with combined distortion / nonlinearity, which may not be effectively canceled based on the determined individualized adjustments to each individual transmitting element.

[0059] While performing DPD on a per-element basis may not be optimal in some situations, it can still be effective in reducing distortion in the combined signal when performed on a small number of transmitter elements, such as 2-4 antennas. However, in mmW applications where 20-30 transmitter elements can be utilized, the per-element approach for applying DPD is less effective in reducing distortion in the combined signal. Furthermore, training DPD based on feedback from 20-30 transmitter elements may be impractical from a cost and / or computational perspective, as the transmitted signal in mmW applications can occupy an increased bandwidth, which increases the complexity of such implementations.

[0060] Now refer to Figure 6Figure 600 illustrates a feedback loop from receiver 602 (e.g., a receiver of the UE) that provides feedback to the multiple transmitting elements based on the total distortion identified in the combined signal received at receiver 602 from the multiple transmitting elements. The total distortion identified in the combined signal provides a common basis for adjusting each transmitting element in a common manner (e.g., rather than based on individualized adjustments). In other words, DPD can be performed at the data level based on the combined signal received at receiver 602, rather than individually at the antenna level for each of the signals transmitted from each of the multiple transmitting elements.

[0061] To characterize the nonlinear characteristics of the combined signal resulting from the cumulative effect of multiple power amplifiers, the signal transmitted from these multiple transmitting elements may need to be transmitted with a low BO (Bandwidth at Breakdown). Since a low BO corresponds to high power at the power amplifiers, in-band and / or out-of-band (OOB) distortion can originate from this transmission. Therefore, the base station may need to transmit compressed pilot signals to receive feedback associated with the power amplifiers. In some cases, compression performed by the power amplifiers can generate OOB transmissions prohibited by regulatory bodies such as the Federal Communications Commission (FCC), the Institute of Electrical and Electronics Engineers (IEEE), and 3GPP, and therefore, compression of the pilot signals may be impractical.

[0062] Figure 7 This is illustration 700 illustrating OOB distortion for different BOs. For example, the expected range of the subcarrier index (k) of a signal can be from -512k to 512k. The portions of the signal residing outside the expected range correspond to OOB distortion. Regulatory agencies may require base stations to maintain an OOB spectrum mask of -45dB, although this threshold may vary depending on the applicable protocol. In various respects, BOs can be used to reduce OOB transmission below the required threshold (e.g., below -45dB), because small clippings can still provide a considerable amount of OOB transmission. For example, in illustration 700, while BOs of 3dB and 8dB each reduce OOB transmission, a 12dB BO is required in illustration 700 to reduce the overall OOB transmission below the required -45dB threshold.

[0063] When identifying the desired BO level, the goal can be to transmit the signal with as much power as possible without violating the OOB transmission requirement. OOB distortion can be caused by compression at the power amplifier. When more compression occurs at the power amplifier, more power is transmitted (e.g., with a smaller BO). Furthermore, transmitting the signal with more power generally leads to an increase in OOB transmission. Although a certain compression in Figure 700 can be achieved with a BO of 12dB, the transmitted power corresponding to a BO of 12dB may be less than the desired power / undesirable. Thus, Figure 700 illustrates the trade-off between transmitted power and reducing OOB transmission. For example, transmitting a signal with a BO of 12dB, where a BO of 3dB is preferred, provides a 9dB power reduction that can result in a reduction of the cell radius of the base station by a factor of 3. In practice, this reduction in cell radius may require deploying up to 10 times more base stations to maintain the same coverage area.

[0064] Because DPD training protocols may be insensitive to small fluctuations in transmit power, a DPD can be trained on x dBm but with coefficients ranging from x-2 to x+2 without significantly impacting its performance. Furthermore, DPD coefficients tend to stabilize because they do not change significantly with the time, temperature, and / or BW used to estimate transmit power. A DPD may also be insensitive to small fluctuations in BW. For example, a DPD can be trained on a 50MHz BW but applied over a 0-100MHz range without significantly affecting its performance. This range can be further relaxed when transmit RF drops small (as is often required by protocols).

[0065] Figure 8 The diagram 800 illustrates the DPD training procedure. In the diagram 800, the BW can be the maximum expected BW for a given BO (e.g., the minimum expected BO). That is, the BO can be, for example, a minimum expected BO of 3dB, while maintaining the OOB distortion below a -45dB threshold. In various respects, the DPD training procedure can be based on an iterative process in which, for the transmitted signal, the coefficients associated with the distortion caused by the power amplifier are identified at the receiver, fed back to the transmitter, and applied / used to train the DPD in the next transmitted signal / iteration.

[0066] In Figure 800, the first signal can be transmitted with high power but a low bandwidth (BW) (e.g., BW / 8). Thus, even if the first signal is compressed, its out-of-band (OOB) distortion does not violate OOB transmission requirements because OOB distortion above the -45 dB threshold is within the permissible transmission range (e.g., -512k to 512k) where data is transmitted normally. The second signal with BW / 4 can be trained based on a nonlinearity at the receiver for the BW / 8 transmission identifier, since the bandwidth factor 2 may not have a significant impact on training the DPD. However, training the DPD for full BW based on a nonlinearity at the receiver for the BW / 8 transmission identifier may have too large a difference / factor for maintaining the threshold accuracy level in the DPD training procedure. Therefore, the third signal with BW / 2 may need to be trained based on a nonlinearity from the BW / 4 transmission identifier, and the fourth signal with full BW may need to be trained based on a nonlinearity from the BW / 2 transmission identifier. Throughout the entire training procedure, the BO can be maintained at a constant BO (e.g., 3dB) during each iteration.

[0067] To perform the training procedure, the transmitter can bypass the DPD to transmit a pilot with BW / 8, which is acknowledged to the receiver for the first iteration. The receiver can determine coefficients based on the distortion caused by the associated power amplifier using a predefined kernel set and predetermined pilot characteristics. Feedback indicating the coefficients can be returned to the transmitter using higher-level messages. The transmitter can use the coefficients identified at the receiver in the first iteration for BW / 8 to train / transmit a second pilot with BW / 4. The transmitted second pilot is similarly acknowledged to the receiver for the second iteration. The receiver can use the predefined kernel set and predetermined characteristics of the second pilot to determine a second set of coefficients based on the second distortion caused by the associated power amplifier, and feed this second set of coefficients back to the transmitter using higher-level message passing. The transmitter can also use the second set of coefficients identified at the receiver in the second iteration for BW / 4 to train / transmit a third pilot with BW / 2, which is acknowledged to the receiver for the third iteration. In the same manner as previous iterations, the third coefficient set can be determined and fed back to the transmitter. At the end of the third iteration, the transmitter can apply the third coefficient set to transmit the full BW for PDSCH or other channels such as PDCCH.

[0068] The first pilot transmitted in BW / 8 can be transmitted on 128 subcarriers ranging from -64k to 64k; the second pilot transmitted in BW / 4 can be transmitted on 256 subcarriers ranging from -128k to 128k; the third pilot transmitted in BW / 2 can be transmitted on 512 subcarriers ranging from -256k to 256k; and the fourth pilot transmitted in BW can be transmitted on 1024 subcarriers ranging from -512k to 512k. In these configurations, the factor by which BW varies with iteration can be a factor other than factor 2. For example, in some cases, the bandwidth variation factor can be factor 1.7. Despite the existence of an exact value for the bandwidth variation factor, the DPD training procedure should still be performed in the iterative steps; otherwise, signals transmitted at full bandwidth may not be able to pass through the OOB transmission protocol. That is, in Figure 800, if BW / 8 transmission were instead transmitted in full BW, the OOB transmission would exceed the required threshold. By using an iterative approach to train the DPD, OOB distortion below the transmit threshold for full BW can be provided at the same low BO / high power as BW / 8 transmission. In other words, if DPD training is not performed and the next iteration is transmitted at the same BO / power, the OOB distortion for the next iteration will start at the same dB level as the previous iteration (e.g., where the dB level at which OOB distortion starts will not decrease in the next iteration).

[0069] The coefficients indicating the nonlinearity associated with the power amplifier can change very slowly. Therefore, these coefficients can be used to provide an approximate approximation to train the DPD relative to the nonlinearity. In some configurations, DPD training procedures can be executed over hours or even days without significantly impacting the performance of the DPD training procedure. Consequently, the overhead of the network used to execute the DPD training procedure can be negligible, as the training procedure can be executed, for example, only once per day within a 200-300ms training window.

[0070] Since nonlinear distortion is generated on the transmit side of the DPD training procedure, a "crowded" nonlinear feedback technique can be used to distribute iterations of the DPD training procedure across multiple UEs. This crowded nonlinear feedback technique can be managed by the base station. For example, the base station can be in communication with multiple UEs, where different UEs can be used for different iterations of the training procedure. That is, the first UE can be used for the first iteration, the second UE for the second iteration, the first / second UE can be used again (or the third UE can be used) for the third iteration, and so on, so that the DPD training procedure is performed across any number of the same or different UEs in communication with the base station. The DPD training procedure can be implemented for different desired transmit powers and / or temperatures. While the DPD training procedure can be more suited to use in conjunction with an array of transmit elements, it can also be implemented for individual transmit elements within the array.

[0071] Figure 9 This is a flowchart 900 of a method for operating a base station (BS). For example, the method may be performed by (such as) base stations (102, 310); devices 1002 / 1202'; and / or processing system 1114 (which may include memory 376 and may be the entire base station 310 or components of base station 310 (such as TX processor 316, RX processor 370, and / or controller / processor 375)).

[0072] In 902, the base station can transmit through multiple transmission (Tx) chains for each iteration i = 1, ..., m in multiple iterations m and apply digital predistortion (DPD). i In the case of transmitting signal S to at least one UE i Where DPD1 is the initial DPD and for the signal S i = 1, ..., m i Each of them is transmitted over a bandwidth (BW) and included in a subset of that bandwidth BW. i The pilot signal is extended upwards, and the BW is extended on multiple subcarriers, wherein for each iteration i, the BW... i The subcarrier size increases. For example, referencing Figure 1 , 6 In Figure 800, base station 102 can transmit signals to at least one UE 104 via one or more transmit chains and, with DPD applied (as illustrated in Figure 600, e.g., via transmit chains and with DPD applied) for each iteration. In Figure 800, each of the signals corresponding to the iterations may include a pilot extending over a subset of the full bandwidth, wherein the subcarrier size of each bandwidth subset increases for each iteration. Furthermore, in Figure 800, DPD may be applied to each iteration of the transmitted signals.

[0073] BW can be centered on a single carrier frequency and for signal S i The pilot signal can be used in BW centered on this carrier frequency. i Inside and from within the BW in the BW i Excluded from other subcarriers. For example, refer to Figure 8 BW, BW / 2, BW / 4, and BW / 8 can each be centered at carrier frequency 0, such that the pilot for each corresponding signal is within the corresponding bandwidth / subset (e.g., BW, BW / 2, BW / 4, and BW / 8) and excluded from subcarriers outside that corresponding bandwidth / subset. In some configurations, BW... i It can be equal to BW / F c m+1-i F cThis is the bandwidth variation factor. For example, refer to... Figure 8 The bandwidth subset can correspond to the BW size that varies by a factor of 2 in each iteration.

[0074] At least one UE for iteration i may include a subset A of the UE set. i UE subsets A1,…,A m At least two UE subsets are different. For example, refer to Figure 1 and 8 The three iterations can be spread across multiple UE subsets included in UEs 1-4, such as the first UE for iterations 1 and 3 and the second UE for iteration 2. In other respects, the UE subsets A1,…,A m Each subset of UEs in the dataset can be different from each other. For example, refer to... Figure 1 and 8 Three iterations can be distributed across three different UEs in multiple UEs 104.

[0075] In 904, the base station can, for each iteration i in multiple iterations m, base itself on the transmitted signal S. i Receive feedback F from at least one UE i For example, refer to Figure 1 , 6 In addition, base station 102 can receive feedback from at least one UE for each iteration in Figure 800 based on the transmitted signal (as illustrated, for example, in Figure 600).

[0076] In 906, the base station can, for each iteration i in multiple iterations m, base the received feedback F. i To apply digital predistortion (DPD) to each of the multiple Tx chains i+1 For example, refer to Figure 1 , 6 And 8, base station 102 can, for each iteration in Figure 800, apply DPD (as illustrated, for example, in Figure 600) to each of the multiple transmission chains based on feedback received from at least one UE 104. For signal S i The transmission and feedback F i The reception and application of DPD can be a DPD training procedure, wherein the number of iterations m used for the DPD training procedure is based on at least one of the following: the power spectral density (PSD) at the BW edge, or as a transmission S i The resulting error vector magnitude (EVM) is less than the threshold. For example, referencing Figure 6The signal is transmitted from the power amplifier, feedback is received from receiver 602, and a DPD training procedure is provided for transmitting subsequent signals. The applied DPD can be further based on feedback from one or more of the multiple Tx chains. For example, refer to Figure 5-6 Feedback from receiver 602 can be based on a combination of signals received from multiple transmit links in transmitting elements 500-550.

[0077] In 908, the base station can access multiple Tx chains and apply DPD. m+1 In this case, transmission is made to one or more UEs in the downlink (DL), and the transmission in the DL includes pilot signals extending across the entire BW. For example, refer to Figure 1 , 6 And 8, base station 102 can transmit pilot signals extending across the entire BW to receiver 602 via multiple Tx chains and in the case of DPD application, as explained in Figure 800. For signals S i = 1, ..., m i And the transfer in DL can be independent of BW i Power P i To transmit. For example, refer to Figure 8 The signals in Figure 800 can be transmitted with the same power, regardless of iterations and / or bandwidth / bandwidth subset size. For signals S = i = 1, ..., m i And transmission in DL can be performed using power backoff (BO). i To transmit. For example, refer to Figure 8 The signal in Figure 800 can be transmitted with the same power BO (e.g., 3dB power BO) regardless of the iteration and / or bandwidth / bandwidth subset size.

[0078] In 910, where each of the multiple Tx chains includes a power amplifier, the base station can construct a database of PA parameters associated with the characteristics of each PA. For example, refer to Figure 1 and Figure 5-6 Base station 102 can construct a database associated with the characteristics of power amplifiers included, for example, in transmitting elements 500-550 and shown in Figure 600.

[0079] In 912, where each of the multiple Tx chains includes a power amplifier, the base station can transmit an index associated with the database to at least one UE, wherein the received feedback is based on the transmitted index and the database, which includes associated characteristics of the PA. For example, refer to Figure 1 and Figure 5-6The base station 102 can transmit to the receiver 602 an index associated with a database constructed based on the characteristics of a power amplifier included, for example, in transmitting elements 500-550 and in diagram 600, so that the received feedback in diagram 600 is based on the transmitted index and the database including the associated characteristics of the PA.

[0080] Figure 10 This is a conceptual data flow diagram 1000 illustrating the data flow between different devices / components in example device 1002. The device may be a base station (e.g., base station 102, 310). Device 1002 includes a transmission component 1004 capable of transmitting pilot signals to at least one UE 1050. For example, as described in conjunction with 902, transmission component 1004 may transmit signals to at least one UE for each of multiple iterations, via multiple transmission chains, and with the application of digital predistortion, over a subset of bandwidths that increases for each iteration's subcarrier size.

[0081] Device 1002 includes a receiving component 1006 for receiving feedback from at least one UE 1050 based on transmitted signals. For example, as described in conjunction with 904, the receiving component 1006 may receive feedback from at least one UE for each of multiple iterations based on transmitted signals. The characteristics of power amplifiers included in multiple transmit chains may be provided from the receiving component 1006 to other components in device 1002 based on the feedback received from at least one UE 1050.

[0082] Device 1002 includes an application component 1008 that receives power amplifier characteristics from receiving component 1006 to train multiple transmit chains to transmit the next pilot signal based on the application of a digital predistortion (DPD). For example, as described in conjunction with 906, application component 1008 can apply digital predistortion to each of the multiple transmit chains for each of multiple iterations based on the received feedback. Device 1002 further includes a construction component 1010 that also receives power amplifier characteristics from receiving component 1006 to construct a database of PA parameters. For example, as described in conjunction with 910, construction component 1010 can construct a database associated with the characteristics of each of the power amplifiers included in the multiple transmit chains.

[0083] As described in conjunction with 908, transmission component 1004 can transmit pilot signals extending across the entire BW to one or more UEs in the downlink via multiple transmit chains and with the application of digital predistortion. Additionally or alternatively, as described in conjunction with 912, transmission component 1004 can transmit an index associated with the database to at least one UE. Transmission component 1004 can transmit this index to at least one UE 1050 based on the database constructed by construction component 1010.

[0084] Device 1002 may include execution Figure 9 The additional components of each block of the algorithm in the aforementioned flowchart. Thus, Figure 9 Each block in the aforementioned flowchart can be executed by a component, and the device 1002 may include one or more of those components. These components may be one or more hardware components specifically configured to execute the process / algorithm, implemented by a processor configured to execute the process / algorithm, stored in a computer-readable medium for implementation by a processor, or some combination thereof.

[0085] Figure 11 Figure 1100 illustrates an example of a hardware implementation of device 1002' employing processing system 1114. Processing system 1114 can be implemented with a bus architecture generally represented by bus 1124. Depending on the specific application and overall design constraints of processing system 1114, bus 1124 may include any number of interconnect buses and bridges. Bus 1124 links together various circuits including one or more processors and / or hardware components (represented by processor 1104, components 1004-1010, and computer-readable medium / memory 1106). Bus 1124 may also link various other circuits, such as timing sources, peripheral devices, regulators, and power management circuits, which are well known in the art and therefore will not be described further.

[0086] Processing system 1114 may be coupled to transceiver 1110. Transceiver 1110 is coupled to one or more antennas 1120. Transceiver 1110 provides means for communicating with various other devices via a transmission medium. Transceiver 1110 receives signals from the one or more antennas 1120, extracts information from the received signals, and provides the extracted information to processing system 1114 (specifically, receiving component 1006). Additionally, transceiver 1110 receives information from processing system 1114 (specifically, transmission component 1004) and generates signals to be applied to the one or more antennas 1120 based on the received information. Processing system 1114 includes processor 1104 coupled to computer-readable medium / memory 1106. Processor 1104 is responsible for general processing, including the execution of software stored on computer-readable medium / memory 1106. When executed by processor 1104, the software causes processing system 1114 to perform the various functions described above for any particular device. The computer-readable medium / memory 1106 may also be used to store data manipulated by the processor 1104 during software execution. The processing system 1114 further includes at least one of the components 1004-1010. These components may be software components running in the processor 1104, software components residing in / stored in the computer-readable medium / memory 1106, one or more hardware components coupled to the processor 1104, or some combination thereof. The processing system 1114 may be a component of the base station 310 and may include memory 376 and / or at least one of the following: TX processor 316, RX processor 370, and controller / processor 375. Alternatively, the processing system 1114 may be the entire base station (e.g., see...). Figure 3 (310).

[0087] In one configuration, the device 1002 / 1002' for wireless communication includes means for transmitting, receiving, applying, and constructing. The aforementioned means may be one or more components of the aforementioned device 1002 and / or one or more components of the processing system 1114 of the device 1002' configured to perform the functions described by the aforementioned means. As described above, the processing system 1114 may include a TX processor 316, an RX processor 370, and a controller / processor 375. Thus, in one configuration, the aforementioned means may be the TX processor 316, the RX processor 370, and the controller / processor 375 configured to perform the functions described by the aforementioned means.

[0088] Therefore, the DPD training procedure can be performed based on an iterative process in which the DPD is repeatedly applied to a subset of bandwidth (BW) whose size increases with each iteration until the DPD is trained for the maximum permissible transmission bandwidth (BW). To perform this training procedure, the transmitter can apply bypass to the DPD to transmit a pilot with a first bandwidth subset (e.g., BW / 8), which is acknowledged to the receiver for the first iteration of the DPD training procedure. The receiver can determine coefficients associated with the distortion caused by the PA and feed these coefficients back to the transmitter for training the DPD to transmit a second pilot with a second bandwidth subset (e.g., BW / 4). The second pilot can similarly be acknowledged to the receiver for the second iteration, a second coefficient determined based on the second distortion caused by the PA, and the second coefficient is fed back to the transmitter for further training of the DPD to transmit a third pilot with a third bandwidth subset (e.g., BW / 2). The same process (e.g., for BW / 2) can be repeated until the transmitter finally trains the DPD to transmit a signal extending across the full bandwidth (BW). In this way, the signal can be transmitted at the maximum permissible BW without increasing the power BO.

[0089] It should be understood that the specific order or hierarchy of the boxes in the disclosed process / flowcharts is an explanation of exemplary methods. It should be understood that the specific order or hierarchy of the boxes in these process / flowcharts can be rearranged based on design preferences. Furthermore, some boxes may be combined or omitted. The appended method claims present the elements of the various boxes in an exemplary order and are not intended to be limited to the specific order or hierarchy presented.

[0090] The preceding description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be 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 granted the full scope consistent with the language of the claims, wherein references to the singular form of an element, unless specifically stated otherwise, are not intended to mean “one and only one,” but rather “one or more.” The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as superior to or overriding other aspects. Unless specifically stated otherwise, the term “some / a” 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 A, multiple B, or multiple C. Specifically, combinations such as "at least one of A, B, or C", "one or more of A, B, or C", "at least one of A, B, and C", "one or more of A, B, and C", and "A, B, C, or any combination thereof" can be only A, only B, only C, A and B, A and C, B and C, or A and B and C, wherein any such combination may include one or more members of A, B, or C. Elements of all aspects described throughout this disclosure that are presently or hereafter known to those skilled in the art are expressly incorporated herein by reference and are intended to be covered by the claims. Furthermore, nothing disclosed herein is intended as a donation to the public, whether or not such disclosure is expressly stated in the claims. The terms "module," "mechanism," "element," "device," etc., may not be a substitute for the term "apparatus." Thus, no claim element should be interpreted as an apparatus plus a function unless the element is expressly stated using the phrase "apparatus for..."

Claims

1. A method for operating a base station (BS), comprising: For each iteration i=1, …, m in multiple iterations m, through multiple emitter Tx chains and applying digital predistortion (DPD) i In the case of transmitting signal S to at least one user equipment (UE) i Where DPD1 is the initial DPD, and for the signal S i=1,…,m i Each of them is transmitted on bandwidth BW and included in a bandwidth subset BW of said BW. i The pilot signal is extended upwards, and the BW is extended on multiple subcarriers, wherein for each iteration i, the BW... i The size of the subcarrier increases; For each iteration i in the multiple iterations m, based on the transmitted signal S i Receive feedback F from the at least one UE i ; For each iteration i in the multiple iterations m, based on the received feedback F i To apply digital predistortion (DPD) to each of the plurality of Tx chains i+1 ); as well as Through the multiple Tx chains and in the application of DPD m+1 In this case, transmission is made to one or more UEs in the downlink DL, and the transmission in the DL includes pilot signals that extend over the entire BW.

2. The method of claim 1, wherein for the signal S i=1, …, m i The transmission described in DL is independent of the BW. i Power P i It was sent to deliver it.

3. The method of claim 1, wherein the signal S for i = 1, …, m i The transmission described in DL is performed using power back-off (BO). i It was sent to deliver it.

4. The method of claim 1, wherein the BW is centered on a carrier frequency and is for the signal S. i The pilot signal in the BW centered at the carrier frequency i Inside and from the BW in the BW i It was excluded from the subcarriers other than those mentioned above.

5. The method of claim 1, wherein the signal S i The transmission of the feedback F i The reception of the DPD and the DPD i The application is a DPD training procedure, wherein the number of iterations m used in the DPD training procedure is based on at least one of the following: the power spectral density (PSD) at the edge of the BW, or as the signal S. i The error vector magnitude (EVM) of the transmitted result is less than the threshold.

6. The method of claim 1, wherein BW i =BW / F c m+1-i And F c It is the bandwidth variation factor.

7. The method of claim 1, wherein the applied DPD is further based on feedback from one or more of the plurality of Tx chains.

8. The method of claim 1, wherein the at least one UE for iteration i includes a subset A of the UE set. i And the UE subsets A1, …, A m At least two UE subsets are different.

9. The method of claim 8, wherein the UE subsets A1, …, A m Each UE subset in the set is distinct from the others.

10. The method of claim 1, wherein each of the plurality of Tx chains comprises a power amplifier PA, and the method further comprises: Construct a database associated with the characteristics of the PA; as well as Transmit the index associated with the database to the at least one UE. The received feedback is based on the transmitted index and the database, which includes the associated characteristics of the PA.

11. An apparatus for operating a base station (BS), comprising: Memory; as well as At least one processor coupled to the memory, and the at least one processor is configured to: For each iteration i=1, …, m in multiple iterations m, through multiple emitter Tx chains and applying digital predistortion (DPD) i In the case of transmitting signal S to at least one user equipment (UE) i Where DPD1 is the initial DPD, and for the signal S i=1,…,m i Each of them is transmitted on bandwidth BW and included in a bandwidth subset BW of said BW. i The pilot signal is extended upwards, and the BW is extended on multiple subcarriers, wherein for each iteration i, the BW... i The size of the subcarrier increases; For each iteration i in the multiple iterations m, based on the transmitted signal S i Receive feedback F from the at least one UE i ; For each iteration i in the multiple iterations m, based on the received feedback F i To apply digital predistortion (DPD) to each of the plurality of Tx chains i+1 ); as well as Through the multiple Tx chains and in the application of DPD m+1 In this case, transmission is made to one or more UEs in the downlink DL, and the transmission in the DL includes pilot signals that extend over the entire BW.

12. The apparatus of claim 11, wherein the signal S for i = 1, …, m i The transmission described in DL is independent of the BW. i Power P i It was sent to deliver it.

13. The apparatus of claim 11, wherein the signal S for i = 1, …, m i The transmission described in DL is performed using power back-off (BO). i It was sent to deliver it.

14. The apparatus of claim 11, wherein the BW is centered on a carrier frequency and is directed towards the signal S. i The pilot signal in the BW centered at the carrier frequency i Inside and from the BW in the BW i It was excluded from the subcarriers other than those mentioned above.

15. The apparatus of claim 11, wherein the signal S i The transmission of the feedback F i The reception of the DPD and the DPD i The application is a DPD training procedure, wherein the number of iterations m used in the DPD training procedure is based on at least one of the following: the power spectral density (PSD) at the edge of the BW, or as the signal S. i The error vector magnitude (EVM) of the transmitted result is less than the threshold.

16. The apparatus of claim 11, wherein BW i =BW / F c m+1-i And F c It is the bandwidth variation factor.

17. The apparatus of claim 11, wherein the applied DPD is further based on feedback from one or more of the plurality of Tx chains.

18. The apparatus of claim 11, wherein the at least one UE for iteration i includes a subset A of the UE set. i And the UE subsets A1, …, A m At least two UE subsets are different.

19. The apparatus of claim 18, wherein the subset of UEs A1, …, A m Each UE subset in the dataset is distinct from the others.

20. The apparatus of claim 11, wherein each of the plurality of Tx chains comprises a power amplifier PA, and the at least one processor is further configured to: Construct a database associated with the characteristics of the PA; and Transmit the index associated with the database to the at least one UE. The received feedback is based on the transmitted index and the database, which includes the associated characteristics of the PA.

21. An apparatus for operating a base station (BS), comprising: For each iteration i=1, …, m in multiple iterations m, via multiple emitter Tx chains and in application of digital predistortion (DPD) i In the case of transmitting signal S to at least one user equipment (UE) i The apparatus, wherein DPD1 is the initial DPD, and for signals S i=1, …, m i Each of them is transmitted on bandwidth BW and included in a bandwidth subset BW of said BW. i The pilot signal is extended upwards, and the BW is extended on multiple subcarriers, wherein for each iteration i, the BW... i The size of the subcarrier increases; For each iteration i in the multiple iterations m, based on the transmitted signal S i Receive feedback F from the at least one UE i The device; For each iteration i in the multiple iterations m, based on the received feedback F i To apply digital predistortion (DPD) to each of the plurality of Tx chains i+1 ) device; as well as Used to pass through the multiple Tx chains and in application DPD m+1 In the case of transmission to one or more UEs in the downlink DL, the transmission in the DL includes pilot signals extending over the entire BW.

22. The device of claim 21, wherein the signal S for i=1, …, m i The transmission described in DL is independent of the BW. i Power P i It was sent to deliver it.

23. The device of claim 21, wherein the signal S for i=1, …, m i The transmission described in DL is performed using power back-off (BO). i It was sent to deliver it.

24. The device of claim 21, wherein the BW is centered on a carrier frequency and is for the signal S. i The pilot signal in the BW centered at the carrier frequency i Inside and from the BW in the BW i It was excluded from the subcarriers other than those mentioned above.

25. The device of claim 21, wherein the signal S i The transmission of the feedback F i The reception of the DPD and the DPD i The application is a DPD training procedure, wherein the number of iterations m used in the DPD training procedure is based on at least one of the following: the power spectral density (PSD) at the edge of the BW, or as the signal S. i The error vector magnitude (EVM) of the transmitted result is less than the threshold.

26. The device of claim 21, wherein BW i =BW / F c m+1-i And F c It is the bandwidth variation factor.

27. The device of claim 21, wherein the applied DPD is further based on feedback from one or more of the plurality of Tx chains.

28. The device of claim 21, wherein the at least one UE for iteration i includes a subset A of the UE set. i And the UE subsets A1, …, A m At least two UE subsets are different.

29. The device of claim 21, wherein each of the plurality of Tx chains comprises a power amplifier PA, and the device further comprises: A means for constructing a database associated with the characteristics of the PA; as well as A means for transmitting an index associated with the database to the at least one UE. The received feedback is based on the transmitted index and the database, which includes the associated characteristics of the PA.

30. A computer-readable medium storing computer-executable code, said code causing the processor, when executed by at least one processor, to: For each iteration i=1, …, m in multiple iterations m, through multiple emitter Tx chains and applying digital predistortion (DPD) i In the case of transmitting signal S to at least one user equipment (UE) i Where DPD1 is the initial DPD, and for the signal S i=1,…,m i Each of them is transmitted on bandwidth BW and included in a bandwidth subset BW of said BW. i The pilot signal is extended upwards, and the BW is extended on multiple subcarriers, wherein for each iteration i, the BW... i The size of the subcarrier increases; For each iteration i in the multiple iterations m, based on the transmitted signal S i Receive feedback F from the at least one UE i ; For each iteration i in the multiple iterations m, based on the received feedback F i To apply digital predistortion (DPD) to each of the plurality of Tx chains i+1 ); as well as Through the multiple Tx chains and in the application of DPD m+1 In this case, transmission is made to one or more UEs in the downlink DL, and the transmission in the DL includes pilot signals that extend over the entire BW.

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