Hierarchical channel state information (CSI) feedback with partial reciprocity with user equipment (UE)

Abstract

A user equipment (UE) or other network component may be operable to configure channel state information (CSI) feedback in response to receiving a CSI reference signal (CSI-RS) according to a hierarchical precoding scheme that selectively reduces feedback overhead associated with the CSI feedback. The UE may be operable to divide and further subdivide a frequency band (e.g., a wideband or a specific frequency portion) into a precoding hierarchy to generate precoders for transmission to a base station, eNodeB (eNB), or next-generation NodeB (gNB) via the CSI feedback.

Description

[0001] Citation of Related Applications

[0002] This application is a national phase application of international patent application No. PCT / CN2020 / 107938, entitled “HIERARCHICAL CHANNEL STATEINFORMATION (CSI) FEEDBACK WITH PARTIAL RECIPROCITY WITH USER EQUIPMENT (UE)”, filed on August 7, 2020, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates to wireless technologies, and more particularly, to techniques for hierarchical channel state information (CSI) feedback for user equipment (UE) with partial reciprocity. Background Art

[0004] The explosive growth of wireless traffic has led to an urgent need for higher data rates. With mature physical layer technologies, further improvements in spectrum efficiency are likely to be negligible. On the other hand, the scarcity of licensed spectrum in low-frequency bands has resulted in insufficient increases in data rates. 5G, the next-generation wireless communication system, will provide information access and data sharing anytime, anywhere, across a wide range of users and applications. 5G is expected to be a unified network / system designed to address distinct and sometimes conflicting performance dimensions and services. These diverse, multi-dimensional demands are driven by different services and applications. Generally speaking, 5G can evolve based on 3GPP Long Term Evolution (LTE) Advanced (LTE-Advanced) with the addition of potential new radio access technologies (RATs), enriching people's lives with better, simpler, and more seamless wireless connectivity solutions. 5G will enable many devices to connect via wireless communication and deliver fast, rich content and services.

[0005] Similar to LTE, multi-antenna technology can become a key technical component in the 3GPP 5G New Radio (NR) system. Specifically, beamforming with very narrow beamwidth (resulting in very high beamforming gain) can become an important tool for high-frequency NR to achieve target coverage. For example, in order to operate in a wide frequency range from below 6GHz to 100GHz, 3GPP NR aims to provide a unified method to achieve single-beam and multi-beam transmission. Multiple antennas can also be implemented at transmission equipment such as transmission reception points (TRPs) (e.g., eNodeB (eNB) / next generation NodeB (gNB) / base station antenna panels) and user equipment (UE), and are called multiple-input multiple-output (MIMO) devices. MIMO technology is the use of multiple antennas or antenna arrays / panels at one or more transmitters (Tx) and one or more receivers (Rx). MIMO systems can be used to increase the data throughput and link reliability of a network without increasing the bandwidth frequency or increasing the transmission power of the network. To achieve this, data communicated between nodes (eNB / gNB) and mobile devices (e.g., UEs) can be distributed across multiple antennas to achieve array gain, improving spectral efficiency and achieving diversity gain. Massive MIMO deploys a large number of antenna elements in an antenna array. Multiple terminals can be deployed to combine Massive MIMO technology with conventional time and frequency division multiplexing using orthogonal frequency division multiplexing (OFDM).

[0006] Three-dimensional (3D) or full-dimensional (FD) MIMO systems can be used in MIMO networks to enhance cellular performance by deploying antenna elements in both the horizontal and vertical dimensions (e.g., a two-dimensional (2D) antenna array). FD MIMO systems can direct two-dimensional (i.e., horizontal and vertical) communications to locations in three-dimensional (3D) space. Compared to traditional two-dimensional MIMO systems, the communication direction in 3D space can improve directivity, thereby allowing for an increased number of communication paths, more focused beamforming, and improved throughput of spatial multiplexing. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a block diagram illustrating an example of a user equipment (UE) communicatively coupled via a network with a network component as a peer device, which can be used in conjunction with various aspects described herein.

[0008] Figure 2 is an exemplary simplified block diagram of a user equipment (UE) wireless communication device or other network device / component (e.g., eNB, gNB) according to various aspects.

[0009] Figure 3 is an illustration of an exemplary precoding hierarchy for a hierarchical precoding scheme in accordance with various aspects.

[0010] Figure 4 is an illustration of another exemplary precoding hierarchy for a hierarchical precoding scheme in accordance with various aspects.

[0011] Figure 5 is an illustration of another exemplary precoding hierarchy for a hierarchical precoding scheme in accordance with various aspects.

[0012] Figure 6 is another block diagram illustrating an exemplary process flow for hierarchical precoding in accordance with various aspects.

[0013] Figure 7 is another block diagram illustrating an exemplary process flow for hierarchical precoding in accordance with various aspects. DETAILED DESCRIPTION

[0014] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of authorized use should be clearly stated to users.

[0015] The present disclosure will now be described with reference to the accompanying drawings, wherein throughout the text, similar (or similar at the end) figure numbers are used to refer to similar elements, and the structures and devices shown therein need not be drawn to scale. As used herein, the terms "component", "system", "interface" etc. are intended to refer to entities, hardware, software (e.g., in execution) and / or firmware related to a computer. For example, a component can be a processor (e.g., a microprocessor, a controller or other processing device), a process running on a processor, a controller, an object, an executable file, a program, a storage device, a computer, a tablet computer and / or a user equipment (e.g., a mobile phone, etc.) with a processing device. By way of example, an application and a server running on a server can also be a component. One or more components can reside in a process, and a component can be located on a computer and / or distributed between two or more computers. This article can describe a set of elements or other component sets, wherein the term "set" can be interpreted as "one or more".

[0016] In addition, the components can execute from various computer-readable storage media having various data structures stored thereon, such as using modules, for example. The components can communicate via local and / or remote processes, such as according to signals having one or more data packets (e.g., data from one component interacts with another component in a local system, a distributed system, and / or across a network, such as the Internet, a local area network, a wide area network, or a similar network with other systems via signals).

[0017] As another example, a component may be a device that has a specific functionality provided by a mechanical component that operates through electrical or electronic circuitry, where the electrical or electronic circuitry may be operated by a software application or firmware application executed by one or more processors. The one or more processors may be internal or external to the device and may execute at least a portion of the software or firmware application. As another example, a component may be a device that provides a specific functionality through an electronic component without the need for a mechanical component; the electronic component may include one or more processors therein to execute at least a portion of the software and / or firmware that provides the functionality of the electronic component.

[0018] The use of the word "exemplary" is intended to present concepts in a concrete manner. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or." That is, unless otherwise specified or clear from the context, "X employs A or B" is intended to mean any natural inclusive permutation. That is, if X employs A; X employs B; or X employs both A and B, then "X employs A or B" is satisfied in any of the foregoing cases. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be construed to mean "one or more," unless otherwise specified or clear from the context to be directed to the singular. Furthermore, to the extent that the terms "comprising," "including," "having," "having," "with," or variations thereof are used in the detailed description and claims, such terms are intended to be inclusive in a manner similar to the term "comprising." Furthermore, when discussing one or more numbered items (e.g., "a first X," "a second X," etc.), generally, the one or more numbered items can be different or they can be the same, but in some cases, the context may indicate that they are different or that they are the same.

[0019] As used herein, the term "circuitry" may refer to, may be a part of, or may include an application-specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), or associated memory (shared, dedicated, or group) operably coupled to the circuit that executes one or more software or firmware programs, a combinational logic circuit, or other suitable hardware components that provide the described functionality. In some embodiments, the circuit may be implemented in one or more software or firmware modules, or the functionality associated with the circuit may be implemented by one or more software or firmware modules. In some embodiments, the circuit may include logic that is at least partially operable in hardware.

[0020] In light of the above, various aspects / implementations are disclosed for communications in beamforming systems or beamforming network devices (e.g., user equipment (UE), evolved Node B (eNB), next-generation Node B (gNB), new radio (NR) base station (BS), multiple-input multiple-output (MIMO) devices, single-input multiple-output (SIMO) devices, etc.). Specifically, with respect to LTE-Advanced and 5G NR devices, performance-related issues (power efficiency, beamforming, channel quality, etc.) may arise in beam management processes, including improving the channel state information (CSI) reporting observed by the receiver (Rx) regarding the downlink channel. For example, for MU-MIMO pairings, wideband precoding can result in significant losses in cell-edge and median UE throughput compared to subband precoding. For example, while the precoding scheme used for the physical downlink shared channel (PDSCH) is not always wideband, assuming that the same frequency-selective precoder used for the channel state information-reference signal (CSI-RS) is used for PDSCH transmission along with a wideband precoder as recommended by the UE, the composite precoder can be frequency selective. However, wideband PMI feedback works well with certain gNB precoding schemes for CSI-RS, but may not work well with other gNB precoding schemes, particularly those for full-division duplex (FDD) operation with partial reciprocity and for time-division duplex (TDD) operation. Therefore, improving precoding performance for UEs with network gNBs, for example by reducing overhead or feedback overhead while ensuring that the gNB accurately obtains channel or subband spacing information, is a priority.

[0021] CSI can be obtained from the transmitter (Tx) or the network side from the receiver: a) based on uplink channel estimation and utilizing channel reciprocity of the wireless channel; and b) derived from quantized feedback from receiver measurements. The quantized form of CSI feedback can be used for both FDD and TDD operating systems. Quantized CSI (or simply CSI) includes the precoding matrix index (PMI) to assist with beamforming or precoding selection on the gNB's Tx antennas. The set (or group) of possible PMIs is represented as a codebook. For the different possible deployments of 5G New Radio (NR) systems, codebooks are designed and configured to provide reasonable performance in all possible serving directions of the gNB. However, depending on the actual gNB deployment, some PMIs may be avoided from use in such codebooks. For example, due to potential interference to neighboring cells, some PMI vectors may cause higher interference in the downlink (DL) channel than other PMI vectors or PMIs. To avoid CSI reporting with large feedback overhead, a hierarchical precoding scheme can be configured and used by the UE for CSI feedback, specifically with beamforming in mind.

[0022] In one aspect, the UE may configure CSI feedback according to a hierarchical precoding scheme to selectively reduce feedback overhead associated with the CSI feedback. Specifically, the UE may configure a precoding hierarchy for hierarchical frequency selective precoding to provide precoders for CSI feedback associated with the hierarchical precoding levels of the precoding hierarchy. This may selectively reduce feedback overhead by allowing the UE to prune precoders belonging to subbands of frequency portions at the hierarchical levels. As generally referred to herein, subbands may be portions of frequency portions divided according to frequency bands at the lowest hierarchical precoding level of the precoding hierarchy, where, for example, these subbands are at the highest index level. Frequency portions may be referred to herein as divided portions of a frequency band that are not at the lowest level of the precoding hierarchy. However, the terms "frequency portion" and subband may be used interchangeably.

[0023] Other aspects and details of the disclosure are further described below with respect to the accompanying drawings.

[0024] Figure 1 An exemplary architecture of a system 100 of a network according to various embodiments (aspects) is shown. The following description is provided for an exemplary system 100 operating in conjunction with LTE system standards and 5G or NR system standards provided by 3GPP technical specifications. However, the exemplary embodiments are not limited in this regard and may be applied to other networks that benefit from the principles described herein, such as future 3GPP systems (e.g., sixth generation (6G) systems), IEEE 802.16 protocols (e.g., WMAN, WiMAX, etc.), and the like.

[0025] like Figure 1As shown, system 100 includes UE 101a and UE 101b (collectively referred to as "UE 101"). In this example, UE 101 is shown as a smartphone (e.g., a handheld touchscreen mobile computing device that can connect to one or more cellular networks), but can include any mobile or non-mobile computing device, such as a consumer electronic device, a cellular phone, a smartphone, a feature phone, a tablet computer, a wearable computer device, a personal digital assistant (PDA), a pager, a wireless handheld device, a desktop computer, a laptop computer, an in-vehicle infotainment (IVI), an in-car entertainment (ICE) device, an instrument cluster (IC), a head-up display (HUD) device, an on-board diagnostic (OBD) device, a dashtop mobile equipment (DME), a mobile data terminal (MDT), an electronic engine management system (EEMS), an electronic / engine control unit (ECU), an electronic / engine electronic control module (ECM), an embedded system, a microcontroller, a control module, an engine management system (EMS), a connected or "smart" appliance, a machine type communication (MTC) device, a machine-to-machine (M2M) device, an Internet of Things (IoT) device, etc.

[0026] In some embodiments, any of the UEs 101 may be an IoT UE, which may include a network access layer designed for low-power IoT applications that utilize short-term UE connections. The IoT UE may utilize technologies such as M2M or MTC to exchange data with an MTC server or device via a public land mobile network (PLMN), proximity service (ProSe), or device-to-device (D2D) communication, a sensor network, or an IoT network. M2M or MTC data exchange may be machine-initiated data exchange. The IoT network describes interconnected IoT UEs, which may include uniquely identifiable embedded computing devices (within the Internet infrastructure) with short-term connections. The IoT UE may execute background applications (e.g., keep-alive messages, status updates, etc.) to facilitate connectivity to the IoT network.

[0027] UE 101 may be configured to connect or, for example, be communicatively coupled to a radio access network (RAN) 110. In an embodiment, RAN 110 may be a next generation (NG) RAN or 5G RAN, an evolved-UMTS terrestrial RAN (E-UTRAN), or a legacy RAN such as UTRAN or GERAN. As used herein, the term "NG RAN," etc., may refer to the RAN 110 operating in an NR or 5G system 100, while the term "E-UTRAN," etc., may refer to the RAN 110 operating in an LTE or 4G system 100. UE 101 utilizes connections (or channels) 102 and 104, respectively, each of which includes a physical communication interface / layer.

[0028] Alternatively or in addition, each UE in UE 101 can be configured with dual connectivity (DC) as multi-RAT or multi-radio dual connectivity (MR-DC), wherein a UE with multi-Rx / Tx capabilities can be configured to utilize resources provided by two different nodes (e.g., 111, 112, or other network nodes) that can be connected via non-ideal backhaul, for example, where one node provides NR access and the other node provides E-UTRA for LTE or NR access for 5G. One node can act as a master node (MN) and the other node can act as a secondary node (SN). The MN and SN can be connected via a network interface, and at least the MN is connected to the core network 120. At least one of the MN and / or SN can operate using shared spectrum channel access. All functions specified for the UE can be used for an integrated access and backhaul mobile terminal (IAB-MT). Similar to UE 101, the IAB-MT can access the network using one network node or using two different nodes with an EN-DC architecture, an NR-DC architecture, etc.

[0029] UE 101b is shown configured to access AP 106 (also referred to as "WLAN node 106," "WLAN 106," "WLAN terminal 106," "WT 106," etc.) via connection 107. Connection 107 may comprise a local wireless connection, such as a connection consistent with any IEEE 802.11 protocol, wherein AP 106 would include Wireless Fidelity. router. In this example, AP 106 is shown connected to the Internet without being connected to the core network of the wireless system (described in further detail below). In various embodiments, UE 101b, RAN 110, and AP 106 may be configured to utilize LTE-WLAN aggregation (LWA) operation and / or LTE / WLAN radio level operation integrated with IPsec tunneling (LWIP). LWA operation may involve RAN nodes 111a-111b configuring UE 101b in a radio resource control RRC_CONNECTED state to utilize radio resources of LTE and WLAN. LWIP operation may involve UE 101b using WLAN radio resources (e.g., connection 107) via an IPsec protocol tunnel to authenticate and encrypt packets (e.g., IP packets) sent over connection 107. IPsec tunneling may include encapsulating the entire original IP packet and adding a new packet header, thereby protecting the original header of the IP packet.

[0030] The RAN 110 may include one or more access nodes (ANs) or RAN nodes 111a and 111b (collectively or individually, "RAN node 111" or "RAN 111") that enable connections 102 and 104. As used herein, the terms "access node," "access point," and the like may describe equipment that provides radio baseband functionality for data and / or voice connections between a network and one or more users. These access nodes may be referred to as BSs, gNBs, RAN nodes, eNBs, Node-Bs, RSUs, transmit receive points (TRxPs), or TRPs, and may include ground stations (e.g., terrestrial access points) or satellite stations that provide coverage within a geographic area (e.g., a cell). As used herein, the terms "NG RAN node" and the like may refer to RAN nodes 111 (e.g., gNBs) operating in NR or 5G systems 100, and the terms "E-UTRAN node" and the like may refer to RAN nodes 111 (e.g., eNBs) operating in LTE or 4G systems 100. According to various embodiments, the RAN node 111 may be implemented as one or more dedicated physical devices such as a macrocell base station and / or a low power (LP) base station for providing a femtocell, picocell, or other similar cell with a smaller coverage area, smaller user capacity, or higher bandwidth than a macrocell.

[0031] In some embodiments, all or part of the multiple RAN nodes 111 may be implemented as one or more software entities running on a server computer as part of a virtual network, which may be referred to as a centralized RAN (CRAN) and / or a virtual baseband unit pool (vBBUP). In these embodiments, the CRAN or vBBUP may implement RAN functional splitting, such as packet data convergence protocol (PDCP) splitting, where the radio resource control (RRC) and PDCP layers are operated by the CRAN / vBBUP and other L2 protocol entities are operated by individual RAN nodes 111; media access control (MAC) / physical (PHY) layer splitting, where the RRC, PDCP, RLC, and MAC layers are operated by the CRAN / vBBUP and the PHY layer is operated by individual RAN nodes 111; or "lower PHY" splitting, where the RRC, PDCP, RLC, MAC layer, and upper portion of the PHY layer are operated by the CRAN / vBBUP and the lower portion of the PHY layer is operated by individual RAN nodes 111. This virtualization framework allows idle processor cores of the multiple RAN nodes 111 to execute other virtualized applications. In some implementations, the individual RAN nodes 111 may represent individual gNB distributed units (DUs) connected to a gNB central unit (CU) via respective F1 interfaces. In these implementations, the gNB-DUs may include one or more remote radio heads or RF front-end modules (RFEMs) (not shown), and the gNB-CUs may be operated by a server (not shown) located in the RAN 110 or by a server pool in a manner similar to a CRAN / vBBUP. Additionally or alternatively, one or more of the multiple RAN nodes 111 may be next-generation eNBs (gNBs), which are RAN nodes that provide E-UTRA user plane and control plane protocol terminations to the UE 101 and are connected to the 5GC via an NG interface.

[0032] Any of the RAN nodes 111 may serve as the endpoint for the air interface protocol and may be the first point of contact for the UE 101. In some embodiments, any of the RAN nodes 111 may perform various logical functions of the RAN 110, including but not limited to functions of a radio network controller (RNC), such as radio bearer management, uplink and downlink dynamic radio resource management and data packet scheduling, and mobility management.

[0033] In an embodiment, UEs 101 may be configured to communicate with each other or with any of RAN nodes 111 using orthogonal frequency division multiplexing (OFDM) communication signals over a multi-carrier communication channel in accordance with various communication techniques, such as, but not limited to, OFDMA communication techniques (e.g., for downlink communication) or single-carrier frequency division multiple access (SC-FDMA) communication techniques (e.g., for uplink and ProSe or sidelink communication), although the scope of the embodiments (aspects) is not limited in this respect. An OFDM signal may include multiple orthogonal subcarriers.

[0034] In some embodiments, a downlink resource grid can be used for downlink transmissions from any of the RAN nodes 111 to the UE 101, while similar techniques can be used for uplink transmissions. The grid can be a time-frequency grid, called a resource grid or time-frequency resource grid, which represents the physical resources in the downlink in each time slot. This type of time-frequency plane representation is common for OFDM systems, making radio resource allocation intuitive. Each column and row of the resource grid corresponds to an OFDM symbol and an OFDM subcarrier, respectively. The duration of the resource grid in the time domain corresponds to a time slot in a radio frame. The smallest time-frequency unit in the resource grid is represented as a resource element. Each resource grid includes multiple resource blocks, which describe the mapping of certain physical channels to resource elements. Each resource block includes a collection of resource elements; in the frequency domain, this can represent the minimum amount of resources that can currently be allocated. Such resource blocks are used to transmit several different physical downlink channels.

[0035] According to various embodiments, the UE 101 and the RAN node 111 communicate data (e.g., transmit data and receive data) over a licensed medium (also referred to as a "licensed spectrum" and / or a "licensed band") and an unlicensed shared medium (also referred to as an "unlicensed spectrum" and / or an "unlicensed band"). The licensed spectrum may include channels operating in a frequency range of approximately 400 MHz to approximately 2.8 GHz, while the unlicensed spectrum may include a 5 GHz band.

[0036] To operate in the unlicensed spectrum, the UE 101 and the RAN node 111 may operate using license-assisted access (LAA), eLAA, and / or feLAA mechanisms. In these implementations, the UE 101 and the RAN node 111 may perform one or more known medium sensing operations or carrier sensing operations to determine whether one or more channels in the unlicensed spectrum are unavailable or otherwise occupied before transmitting in the unlicensed spectrum. The medium / carrier sensing operations may be performed in accordance with a listen-before-talk (LBT) protocol.

[0037] The LAA mechanism is built on the carrier aggregation (CA) technology of the LTE-Advanced system. In CA, each aggregated carrier is called a component carrier (CC). In some cases, each CC may have a different bandwidth from other CCs. In a time division duplex (TDD) system, the number of CCs and the bandwidth of each CC may be the same for DL ​​and UL. CA also includes individual serving cells to provide each CC. The coverage of the serving cells may be different, for example, because CCs on different frequency bands will experience different path losses. The primary serving cell or PCell can provide a primary component carrier (PCC) for both UL and DL, and can handle radio resource control (RRC) and non-access layer (NAS) related activities. Other serving cells are called SCells, and each SCell can provide a single secondary component carrier (SCC) for both UL and DL. SCCs can be added and removed as needed, and changing PCCs may require UE101 to undergo switching. In LAA, eLAA, and feLAA, some or all of the SCells can operate in unlicensed spectrum (referred to as "LAA SCells"), and the LAA SCells are assisted by PCells operating in licensed spectrum. When a UE is configured with more than one LAA SCell, the UE may receive UL grants on the configured LAA SCells, indicating different PUSCH starting positions within the same subframe.

[0038] The PDSCH carries user data and higher-layer signaling to UE 101. The physical downlink control channel (PDCCH) carries information about, among other things, the transport format and resource allocation associated with the PDSCH channel. It may also inform UE 101 about the transport format, resource allocation, and hybrid automatic repeat request (HARQ) information associated with the uplink shared channel. Typically, downlink scheduling (allocation of control and shared channel resource blocks to UE 101b within a cell) may be performed at any of RAN nodes 111 based on channel quality information fed back from any of UEs 101. Downlink resource allocation information may be sent on the PDCCH for (e.g., allocated to) each of UEs 101.

[0039] PDCCH uses control channel elements (CCE) to transmit control information, where multiple (e.g., 6, etc.) CCEs may be composed of resource element groups (REGs), where REGs are defined as physical resource blocks (PRBs) in OFDM symbols. For example, before being mapped to resource elements, PDCCH complex-valued symbols may first be organized into quadruples, which may then be arranged using a sub-block interleaver for rate matching. Each PDCCH may be transmitted using one or more of these CCEs, where each CCE may correspond to nine sets of four physical resource elements, referred to as REGs. Four quadrature phase shift keying (QPSK) symbols may be mapped to each REG. Depending on the size of the DCI and the channel conditions, one or more CCEs may be used to transmit the PDCCH. Four or more different PDCCH formats with different numbers of CCEs (e.g., aggregation levels, L=1, 2, 4, 8, or 16) may be defined in LTE.

[0040] Some embodiments may use the concept of resource allocation for control channel information, which is an extension of the above concept. For example, some embodiments may utilize an extended (E)-PDCCH that uses PDSCH resources for control information transmission. One or more ECCEs may be used to transmit EPDCCH. Similar to the above, each ECCE may correspond to a set of nine physical resource elements, called EREGs, including four physical resource elements. In some cases, an ECCE may have other numbers of EREGs.

[0041] The RAN nodes 110 may be configured to communicate with each other via an interface. In an embodiment in which the system 100 is an LTE system, the interface may be an X2 interface. The X2 interface may be defined between two or more RAN nodes 111 (e.g., two or more eNBs / gNBs, etc.) connected to an evolved packet core (EPC) or core network 120, and / or between two eNBs connected to the EPC 120. In some implementations, the X2 interface may include an X2 user plane interface (X2-U) and an X2 control plane interface (X2-C). The X2-U may provide a flow control mechanism for user packets transmitted over the X2 interface and may be used to transmit information about the delivery of user data between eNBs or gNBs. For example, X2-U may provide specific sequence number information about user data transmitted from the master eNB (MeNB) to the secondary eNB (SeNB); information about successful in-sequence delivery of PDCP packet data units (PDUs) for user data from the SeNB to the UE 101; information about PDCP PDUs that were not delivered to the UE 101; information about the current minimum expected buffer size at the SeNB for transmitting user data to the UE; etc. The X2-C may provide intra-LTE access mobility functions, including context transfer from the source eNB to the target eNB, user plane transmission control, etc.; load management functions; and inter-cell interference coordination functions.

[0042] RAN 110 is shown as being communicatively coupled to a core network—in this embodiment, to a core network (CN) 120. CN 120 may include multiple network elements 122 configured to provide various data and telecommunication services to customers / subscribers (e.g., users of UE 101) connected to CN 120 via RAN 110. Components of CN 120 may be implemented in one physical node or separate physical nodes, including components for reading and executing instructions from machine-readable or computer-readable media (e.g., non-transitory machine-readable storage media). In some embodiments, NFV may be used to virtualize any or all of the aforementioned network node functions (described in further detail below) via executable instructions stored on one or more computer-readable storage media. A logical instance of CN 120 may be referred to as a network slice, and a logical instance of a portion of CN 120 may be referred to as a network sub-slice. Network Function Virtualization (NFV) architecture and infrastructure may be used to virtualize one or more network functions onto physical resources comprising a combination of industry-standard server hardware, storage hardware, or switches (alternatively, performed by proprietary hardware). In other words, the NFV system may be used to perform a virtual or reconfigurable implementation of one or more Evolved Packet Core (EPC) components / functions.

[0043] Generally, the application server 130 may be an element that provides applications that use IP bearer resources with the core network (e.g., Universal Mobile Telecommunications System Packet Service (UMTS PS) domain, LTE PS data service, etc.). The application server 130 may also be configured to support one or more communication services (e.g., VoIP sessions, PTT sessions, group communication sessions, social networking services, etc.) for the UE 101 via the EPC 120.

[0044] In an embodiment, CN 120 may be a 5GC or 5GC 120, and RAN 110 may be connected to CN 120 via an NG interface 113. In an embodiment, NG interface 113 may be divided into two parts: a next-generation (NG) user plane (NG-U) interface 114, which carries traffic data between RAN node 111 and the user plane function (UPF); and an S1 control plane (NG-C) interface 115, which is a signaling interface between RAN node 111 and the access and mobility management function (AMF). Core network CN 120 may also be a 5GC 120.

[0045] In an embodiment, CN 120 may be a 5G CN (referred to as "5GC 120," etc.), while in other embodiments, CN 120 may be an Evolved Packet Core (EPC). In the case where CN 120 is an EPC (referred to as "EPC 120," etc.), RAN 110 may be connected to CN 120 via an S1 interface 113. In an embodiment, S1 interface 113 may be divided into two parts: an S1 user plane (S1-U) interface 114, which carries traffic data between RAN node 111 and the S-GW; and an S1-MME interface 115, which is a signaling interface between RAN node 111 and the MME.

[0046] refer to Figure 2 , shows a block diagram of a user equipment (UE) device or other network device / component (e.g., a gNB, eNB, or other participating network entity / component). UE device 200 includes: one or more processors 210 (e.g., one or more baseband processors), the one or more processors including processing circuitry and associated interfaces; transceiver circuitry 220 (e.g., including RF circuitry, which may include transmitter circuitry (e.g., associated with one or more transmit chains) and / or receiver circuitry (e.g., associated with one or more receive chains), the transmitter circuitry and the receiver circuitry may employ common circuit elements, different circuit elements, or a combination thereof); and memory 230 (which may include any of a variety of storage media and may store instructions and / or data associated with one or more of processor 210 or transceiver circuitry 220).

[0047] In addition, memory 230 (and other memory components discussed herein, such as memory, data storage devices, etc.) may include one or more machine-readable media, including instructions that, when executed by the machine or component herein, cause the machine to perform the actions of the method or device or system for concurrent communication using multiple communication technologies according to the embodiments and examples described herein. It should be understood that the aspects described herein can be implemented by hardware, software, firmware, or any combination thereof. When implemented in software, the function can be stored as one or more instructions or codes on a computer-readable medium (e.g., a memory or other storage device described herein) or transmitted via a computer-readable medium. Computer-readable media include both computer storage media and communication media, which include any media that facilitates transferring a computer program from one place to another. Storage media or computer-readable storage devices can be any available media that can be accessed by a general-purpose or special-purpose computer. By way of example only and not limitation, such computer-readable media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage devices, magnetic disk storage devices or other magnetic storage devices or other tangible and / or non-transitory media that can be used to carry or store desired information or executable instructions. Moreover, any connection may also be referred to as a computer-readable medium. For example, if coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave are used to transmit software from a website, server, or other remote source, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. As described in more detail below, system 400 can facilitate higher power efficiency for beam management operations, including CSI reporting / feedback based on a hierarchical precoding scheme.

[0048] According to various aspects, a UE 200 / 101 may be operable to configure a channel state information (CSI) reporting configuration to enable a precoding matrix indicator (PMI) as CSI feedback (report) associated with a rank indicator (RI), a wideband channel quality indicator (CQI), or a subband CQI. The PMI precoder may be configured based on a hierarchical precoding scheme for hierarchical frequency selective precoding to configure CSI feedback from the UE 200 / 101. The transmission may then be processed by the gNB 111, 112, or 200 for beamforming based on a codebook formed from the feedback.

[0049] For example, CSI feedback for FDD or TDD can be based on partial reciprocity between UE 101 and gNB 111. Theoretically, not all multipath parameters for FDD downlink and uplink channels are necessarily equivalent. Therefore, full reciprocity does not necessarily hold, but rather partial reciprocity. The uplink sounding reference signal (SRS) is primarily used for CSI measurement to enable scheduling and link adaptation for the UL frequency band. For example, in TDD, by leveraging channel reciprocity, the transmitter or gNB 111 can estimate the downlink channel based on the SRS on the uplink channel. However, such reciprocity relies on accurate calibration of the transceiver RF chain at gNB 111. The sounding mechanism used to estimate the UL channel across different bandwidths (subband or wideband) depends on the terminal channel conditions. Terminals close to gNB 111 are not necessarily power-limited and can therefore allocate wideband sounding to provide CSI estimates for the entire frequency band. On the other hand, cell-edge terminals are power-limited and can only allocate power to a limited number of subbands. gNB 111 relies on CSI to coherently process antennas. For example, gNB 111 utilizes subband spacing information, but ensuring such information can incur overhead costs, especially for MIMO schemes. Therefore, subband feedback to gNB 111 in CSI can be beneficial, particularly compared to limiting PMI feedback in CSI feedback.

[0050] In the specific example of SRS signaling, UE 101, for example, uses an uplink carrier frequency f u The SRS is transmitted to the gNB 111. The gNB 111 may receive the SRS using multiple Rx antennas and extract parameters / characteristics such as angle of arrival (AoA), delay spread, angular spread, average AoD (transmission angle), etc. from the received signal. The gNB 111 assumes the same parameters / characteristics or calculates the same parameters / characteristics for the downlink frequency f d After generating the precoder for CSI-RS, gNB111 can derive the parameters / characteristics based on the constructed downlink frequency f d gNB 111 may also employ frequency-selective (subband-based) precoding for the CSI-RS. UE 101 may then receive the CSI-RS and respond by feeding back the wideband PMI and subband CQI as CSI feedback to the network. However, CSI feedback may impact network system performance with respect to average throughput or cell-edge throughput.

[0051] In one aspect, a hierarchical precoding scheme can be configured by UE 101 by configuring a precoding hierarchy. For example, a frequency band or broadband can be divided into frequency portions and configured as a hierarchical tree, such that these divided portions form different hierarchical levels of the precoding hierarchy. The frequency portions can be further subdivided into subbands. If differences in the precoders associated with the subbands are achieved, these precoders are not eliminated and are retained to be transmitted in the CSI feedback. However, if no differences are observed between the frequency portions and the subbands, the frequency portions of the subbands of the frequency portions are eliminated. Thus, the hierarchical precoding scheme can selectively reduce the amount of feedback overhead used for CSI feedback, improve efficiency, and remove network costs in terms of resources.

[0052] refer to Figure 3 , shows an example of a precoding hierarchy configured for performing hierarchical frequency selective precoding based on a hierarchical scheme according to various aspects (or implementation aspects). The precoding hierarchy 300 includes a root frequency portion 302 that includes a wideband or frequency band considered for use in generating a PMI precoder in CSI feedback. The root frequency portion can be designated as a frequency portion indexed as PMI. 0,0 , which corresponds to the lowest indexed level of the precoding hierarchy 300, as shown at the top level of the precoding hierarchy 300. Although three hierarchical precoding levels (level 0, level 1, level 2) are shown, the precoding hierarchy 300 may be configured to have any number of hierarchical levels.

[0053] The next higher index level (level 1) relative to the root frequency portion 302 corresponds to frequency portions 304 and 306 that have been divided from the root frequency portion 302, which root frequency portion includes, for example, both frequency portions 302 and 304 and sub-bands 308, 310, 312, and 314. 1,0 、P 1,1 Each frequency portion 304 and 306 is further divided (subdivided) into subbands 308 to 314 at the highest index level (level 2) of the precoding hierarchy 300, as subbands indexed as P 2,0 、P 2,1 、P 2,2 、P 2,3 sub-band.

[0054] Each subband may belong to a frequency portion at H hierarchical level, where H may be any integer greater than 0. In one example, the hierarchical level H may be represented as follows: Where N may be the subband used for CSI feedback (eg, indexed as P 2,0 、P 2,1 、P 2,2 、P 2,3At level 0 (root), there is a single frequency portion P 0,0 As the root frequency portion 302 consisting of all sub-bands 308 to 314. At level 1, the frequency portion P at a higher index level (level 1) than level 0 0,0 Below, there is a frequency part P indexed as 1,0 、P 1,1 The two frequency parts 304 and 306 of FIG.

[0055] In summary, at the hierarchical precoding level h, for the frequency part P h-1,m ,m=0,…,2 h-1 -1, according to level h-1, there are two frequency parts P h,2m and P h,2m+1 , these two frequency parts divide the subband from the frequency part P h-1,m Partition out, they are roughly equal; alternatively, the partition can be formulated so that there are h-1,m The two subtrees (leaves) P h,2m and P h,2m+1 (For a specific N that is not a power of 2, the precoding hierarchy can be configured so that at a given hierarchical precoding level there are only h-1,m A subtree (leaf) P h,2m or P h,2m+1 (For example, for the leftmost leaf or the rightmost leaf). For example, for N=7, P 3,7 or P 3,0 exist Figure 4 may not exist (note Figure 4 is a diagram for N=8.) In another case, some leaves (or one leaf, as a frequency portion or subband) on the rightmost side and some leaves (one leaf) on the leftmost side do not necessarily exist at a given hierarchical precoding level.

[0056] In one aspect, the frequency portion P indexed as being at level 1 1,0 、P 1,1 The frequency portions 304 and 306 may be divided into frequency portions P 0,0, which are approximately equal. Thus, each frequency partition of the precoding hierarchy 300 can be a nearly equal or equal division of the parent frequency partition at a lower index level. Specifically, a wideband precoder can still be configured for all four subbands, but the wideband frequency partition can be divided into two partitions. For example, if a certain number (e.g., 32 or another number) of physical resource blocks (PRBs) are divided into two partitions, another precoder can be configured to enter one frequency partition within a portion of the PRBs, and if the differences between the equivalent partitions (e.g., 308 or 310) as part of the same parent frequency partition (e.g., 304) are small or negligible, then these subbands (e.g., 308, 310) can be eliminated from the CSI feedback. Similar evaluation / elimination can be performed throughout the precoder hierarchy, for example, to select a single subband and associated parent partition for feedback. Then, the same operation can be performed for the other subbands under the lower index frequency partition, where the PRBs can be divided into two partitions again and two additional PMI precoders can be configured and compared. For example, if the difference is not significant enough, no feedback overhead is incurred for these parts or subbands. In this way, the same performance can be achieved for PMI, but with less overhead feedback.

[0057] In one example, pruning or elimination can be performed or analyzed based on a top-down approach or a bottom-up approach. Here, one or more bitmaps corresponding to the hierarchical precoding levels can be configured or evaluated based on a bottom-up approach, starting from the lowest indexed hierarchical precoding level in the precoding hierarchy of the hierarchical precoding scheme. For example, the lowest indexed hierarchical precoding level includes the frequency band that serves as the root frequency portion 302. Alternatively or in addition, one or more bitmaps can be configured or evaluated based on a bottom-up approach, starting from the highest indexed hierarchical precoding level (such as subbands 308 to 314), corresponding to the hierarchical precoding levels. One or both approaches can be used to determine the precoder position, for example, based on the CSI feedback provided by UE 101 to gNB 111 based on the hierarchical precoding scheme.

[0058] Alternatively or in addition, the precoding hierarchy may be configured such that there are two subtrees (leaves) 304 and 306 from the root 302 of the hierarchical tree structure comprising the precoding hierarchy 300. For example, each of these may further form branches in a subtree that is further divided into subbands 308 and 310 subdivided from the frequency portion 304 and subbands 312 and 314 subdivided from the frequency portion 306. Although three levels including the root frequency portion 302 at level 0, frequency portions 304 and 306 at level 1, and subbands 308 to 314 at level 2 are shown as three levels, one or more different hierarchical precoding levels may also be configured as part of the precoding hierarchy 300 to form additional frequency portions or subbands for determining CSI feedback. In summary, feedback information from different hierarchical levels can be used in several ways: first, feedback information from the root level to the highest indexed level can be utilized. This can be in the form of a product of precoders applied at different hierarchical levels, or in the form of all underlying feedback parameters applied at different hierarchical levels to produce composite feedback parameters applicable to the current subband. In a second approach, feedback information can come from a single hierarchical level used.

[0059] The same partitioning process corresponding to the precoder hierarchy 300 can be configured by the UE 101 until level H is reached for generating precoders for CSI feedback, where H represents the number of hierarchical levels of the precoding hierarchy. The UE 101 generates precoders associated with the frequency parts 304, 306 or subbands 308 to 314 at different hierarchical levels (hierarchical precoding levels). For example, W h，m may correspond to a precoder at a hierarchical precoding level h and a frequency portion M, where h = 0, 1, ..., H and m = 0, ..., 2 h -1. Dimension W 0，0 It can be expressed as N tx ×R, where N tx may denote a CSIRS port number, and R denotes a feedback rank indicator (RI) value.

[0060] Alternatively or additionally, W 0,0 It can be expressed as and B 0,0 The product of Yes N tx ×R1, and B 0,0 is R1×R,N tx can be the CSI-RS port number, and R1 can be a parameter that depends on the number or value of the feedback rank indicator (RI), ie, R, where R1>R. The parameter R1 can be used to distinguish these values ​​from R as seen for R=1: If R1=R, where because W 0，0It is already a rank 1 precoder, so it may be difficult to introduce frequency adaptation. However, in the case of R1=2, for example, different combining coefficients or rotation matrices can be configured accordingly for adapting the channel to frequency.

[0061] Alternatively or in addition, for h = 0, 1, ..., H and m = 0, ..., 2 h -1, generate two matrices A h，m and B h，m , where A h，m is R1×R1, and B h，m is rank-dependent, for example, R1×R. Then the precoder for subband n can be given by Given, where

[0062] In another aspect, the UE 101 may configure the feedback overhead according to one or more overhead reduction mechanisms. For example, the UE 101 may configure each hierarchical precoding level differently with a different amount of feedback overhead. At the root level or level 0, the feedback overhead may be higher, and then, gradually, the feedback overhead at higher indexed levels (e.g., level 1 or level 2) may be increasingly limited with higher indexed hierarchical levels, or prevented from increasing after a predefined level. At the root frequency portion 302, for example, a larger amount of information with a higher feedback priority is utilized, and thus more refined additional information (e.g., rotation angle or other parameter data) is defined for CSI feedback. At each lower level or higher indexed hierarchical level, refinement may be performed so that the information is coarser or less detailed, has a lower priority, and therefore utilizes fewer information bits for CSI feedback. In one example, a precoder codebook with a precoder used for CSI feedback may have a progressively coarser resolution for rotation angles at higher indexed hierarchical precoding levels (e.g., level 1 with frequency portions (304, 306) or level 2 with subbands (308 to 314)) than for rotation angles at lower indexed hierarchical precoding levels (e.g., level 1, root 302) for the hierarchical precoding scheme.

[0063] In another aspect, the UE 101 may configure feedback overhead according to one or more overhead reduction mechanisms, including pruning individual subbands, or a subtree (e.g., subbands 308 and 310 with frequency portion 304) formed together as child nodes (e.g., subbands 308, 310, 312, or 314) of a parent hierarchical level of one or more frequency portions (e.g., 304 or 306) in a hierarchical precoding scheme. For some subtrees, finer distinctions between its two child nodes are not required (and therefore, distinctions are not required for all descendants (e.g., subbands 308 and 310 of that particular subtree (e.g., parent frequency portion 304)). In such cases, the entire subtree structure (e.g., subbands 308 and 310 with frequency portion 304) may be pruned, and no feedback overhead is incurred for its descendants (e.g., subbands 308 and 310). In connection with this mechanism, the UE 101 may configure a bitmap indicating the subbands 308 to 314 that may be used in the CSI report, where each bit may correspond to a subband 308 to 314. The UE 101 may configure the bitmap with the hierarchical precoding level to indicate the non-pruned subbands and pruned subbands associated with the CSI feedback.

[0064] For example, for a given subband, a "0" may indicate no feedback at level H, and a "1" indicates feedback is provided at level H, or vice versa.

[0065] In other aspects, feedback overhead reduction can be configured by combining the above aspects for reduction or utilizing each aspect independently of each other, so that it is generally consistent with a hierarchical precoding scheme, not directly dependent on the physical characteristics of the channel, but rather on the channel correlation between CSI pairs or related parameters. For example, pruning can be combined with coarser feedback with higher index precoding levels.

[0066] The number N may be determined based on the number of PRBs in the bandwidth part and the subband size, which may be similar to that found in TS 38.214 with reference to Table 5.2.1.4-2: Configurable Subband Sizes. When N subbands is not a power of 2, the frequency part may be determined based on a fixed size or adapted to the size of its parent frequency part, so that approximately equal portions are given to sibling parts or subparts. In a simplified example, N = 4 subbands may be generated for CSI reporting, which may be numbered B k , k = 1, 2, 3, .., N. Here, to simplify the description, N is a power of 2, but further description is provided below where N is not a power of 2, such as Figure 4 UE 101 may generate the following precoder representation W h，mThe precoder may be a precoder in a hierarchical structure h and a frequency part M. UE 101 generates a precoder in a hierarchical structure h=0, 1, ..., 2 for a wideband or a frequency band. 0，0 The wideband precoder associated with the root 402 may be represented for all frequency parts with a subband. 0，0 N tx ×R means, where N tx is the CSI RS port number, and R is the feedback rank number, which can be a matrix or a value. 1，0 The first part of the subband (ie, subbands 1, 2, and W) may be represented as 1，1 ), which may be an additional precoder for the second part of the subbands (e.g., for level 1, i.e., 3, 4). Similarly, the second level precoder may be composed of W 2，m Denote that m=0, 1, 2, 3, which corresponds to an additional precoder for the (m+1)th quarter of the subband (ie, subband M).

[0067] Let the precoder W h，m Parameter a h,m parameterized, so W h，m =G(a h,m ), where G(.) is a mapping function. For example, a precoder may be generated for the first subband 308, which may correspond to the precoder G(a 0,0 +a 1,0 +a 2,0 A precoder may be generated for the second subband 310, which may be represented by G(a 0,0 +a 1，0 +a 2,1 ) is represented by G(a). A precoder may be generated for the third subband 312, which may be represented by G(a 0,0 +a 1,1 +a 2，2 ) is represented by G(a). A precoder may be generated for the fourth subband 314, which may be represented by G(a 0，0 +a 1,1 +a 2，3 )express.

[0068] Additionally or alternatively, for W h，m The codebook construction may be of type II with progressively coarser resolution as configured by UE 101 to be provided to gNB 111 or for a given rotation with coarser resolution for the rotation angle (e.g., W with type II). 0，0 , and W for h>0 h，mA given rotation, as configured for selectively reducing CSI feedback overhead, may have progressively coarser resolution for the rotation angle. UE 101 may generate a precoder codebook with a precoder for CSI feedback that includes progressively coarser resolution for the rotation angle at higher indexed hierarchical precoding levels than at lower indexed hierarchical precoding levels, independently of or in combination with pruning mechanisms for selectively reducing CSI feedback overhead.

[0069] Additionally or alternatively, the hierarchical structure precoding level h and frequency part M, h = 0, 1, ..., H and m = 0, ..., 2 h -1, precoder W h，m With size N tx ×R, where N tx may denote a CSI RS port number, and R denotes a feedback rank indicator (RI) value.

[0070] refer to Figure 4 , shows another example of a precoding hierarchy for a hierarchical precoding scheme according to various aspects or embodiments. The precoding hierarchy 400 includes Figure 3 The similarly indexed frequency portions 404 to 414 and subbands 416 to 432 are shown so that at hierarchical precoding level h of hierarchical precoding layer H, frequency portions P from level h-1 may be used. h-1，m Indicates that m = 0, ..., 2 h-1 -1. UE 101 can use the frequency part P h-1，m Divided into two frequency parts P h，2m and P h，2m+1 , for example, the two frequency parts may be approximately equal; alternatively, the partitioning may be formulated such that there is a h-1，m The two subtrees (leaves) P h，2m and P h，2m+1 .

[0071] In one aspect, as part of a hierarchical precoding scheme, the UE 101 may prune one or more hierarchical precoding levels (e.g., levels 1 to 3) of the frequency portions 404 to 414 or subbands 416 to 432 based on an overhead reduction mechanism for CSI feedback. A bitmap for each hierarchical precoding level may then be configured by the UE 101, the bitmap indicating non-pruned subbands and pruned subbands associated with CSI feedback. Figure 4 As shown, for example, pruned subbands 416 to 430 are indicated by Xs above them and are therefore not considered in the CSI feedback to gNB 111 and are eliminated to reduce feedback overhead.

[0072] Specifically, UE 101 may determine whether there are predetermined differences or differences in precoder configurations between the subbands and may subsequently eliminate these precoders associated with the subbands from the feedback. Thus, in the exemplary precoding hierarchy 400, only subband 432 and parent frequency portions 414, 406, and 402 are configured in the CSI feedback. For example, UE 101 may make such a determination of the difference between the precoders corresponding to any two subbands (e.g., 416 and 418) of the subtree or the frequency portion (e.g., 408) from which they are divided. Similarly, similar determinations may be made through the precoding hierarchy 400 until a single subband (e.g., 432, etc.) is determined for CSI feedback. UE 101 selects the subband at the lowest level of the precoding hierarchy for the precoder for CSI feedback and may subsequently generate precodes for frequency bands at one or more hierarchical precoding levels that include the frequency portion of the subband selected by the precoder for CSI feedback.

[0073] Alternatively or in addition, a precoder may be configured or mapped to CSI feedback for each hierarchical level of a precoding hierarchy, or at any one or more hierarchical levels of a precoding hierarchy. For example, a bitmap or mapping to CSI feedback may be generated at hierarchical precoding levels higher than the highest indexed precoding level, such as only at level 2, level 1, or level 0, or any combination of hierarchical levels. A bitmap or mapping to CSI feedback may be generated or determined only for the highest indexed hierarchical level (e.g., level 3), or any one or more hierarchical levels of a precoding hierarchy. For example, any combination of one or more hierarchical levels may be associated with one or more bitmaps generated or mapped for the associated one or more precoders.

[0074] Using the established symbols, Figure 3 In a similar manner, a precoder can be generated according to the selected subband, where Figure 3 In the example, the first, second, third, fourth sub-bands, etc. may correspond to their respective representations: 2，0 、W 2，1 、W 2，2 and W 2，3 . Figure 4 Another example is shown where there are N=8 subbands for CSI feedback reporting. Here, UE 101 may report a level 3 bitmap [00 00 00 01], where the hierarchical level may be H=log2(8)=3, as representing the highest index level; and for level 2, the UE reports [0 0 0 1], and for level 1, the UE reports

[01] . Then, in response to receiving such feedback, gNB 111 may configure or infer information based on a different bitmap. For example, based on the level 1 bitmap, gNB 111 may determine W 1，0Not included in feedback, but W 1，1 Included in the feedback. For example, based on the level 2 bitmap, gNB 111 may further determine: 2，0 、W 2，1 、W 2，2 Not included in feedback, but W 2，3 Based on the level 3 bitmap, gNB 111 may further determine W 3，k , k=0,1,2,4,5,6 are not included in the feedback, but W 3，7 Included in feedback.

[0075] Additionally or alternatively, in response to receiving CSI feedback from UE 101, gNB 111 may configure the PMI precoder component from level 0 to level H without considering subtree pruning as follows:

[0076] W 0，0

[0077] W 1，0 , W 1，1 ,

[0078] W 2，0 , W 2，1 , W 2，2 , W 2，3 ,

[0079] W 3，0 , W 3，1 , W 3，2 , W 3，3 , W 3，4 , W 3，5 , W 3，6 , W 3，7 .

[0080] When considering subtree pruning, gNB 111 may arrange the PMI components from level 0 to level H, excluding the underlined components for CSI reporting, as follows:

[0081] W 0，0 ,

[0082] W 1，0 , W 1，1 ,

[0083] W 2，0 , W 2，1 , W 2，2 , W 2，3 ,

[0084] W 3，0 , W 3，1 , W 3,2 , W 3，3 , W 3，4 ,W 3，5 ， W 3,6 ，W 3，7

[0085] The omission of underlined components may be fully determined by gNB 111 based on the Level 1 to Level H bitmap included in the CSI feedback, or provided by higher layer signaling (e.g., RRC signaling, etc.). Thus, according to one embodiment or aspect, gNB 111 may process the CSI feedback provided by UE 101, for example, based on an omission rule. Typical CSI feedback also includes an RI (rank indication), a wideband CQI, and a subband CQI, which may be a different CQI from the wideband CQI. Considering NR, up to 8 transmission layers are supported. If the RI indicates 5 or more spatial layers, these spatial layers are mapped to two transport blocks, and the CQI and subband CQI are calculated separately for each transmission. It can be seen that the CSI feedback is not fixed, depending on whether the RI is > 4 and the number of pruned subbands selected (and, accordingly, the number of non-pruned subbands). To aid decoding on the gNB side, CSI feedback can be divided into two parts: Part 1 includes the RI, wideband CQI, subband CQI for the first transport block, and a bitmap indicating pruned / non-pruned subbands; and Part 2, in the second transmission or feedback, includes the subband CQI for the second transport block and PMI feedback as given below in the readout sequence. If more than one CSI-RS resource is provided to the UE for hierarchical precoding feedback, the CRI (CSI-RS resource indicator) may also be included in the first part (or Part 1) of the CSI feedback, which may be in a different / separate transmission used for feedback than the second part of the CSI. Specifically, omission rules can be configured based on when the feedback overhead for a given rank is greater than the feedback overhead that can be sent back to gNB 111 using the specified resources. Based on the hierarchical precoding scheme described in accordance with aspects or embodiments herein, the readout or report provided by UE 101 for feedback may be sequentially ordered from the lowest index level (i.e., level 0) to the highest index level (i.e., level H) of the precoder, or alternatively, from the highest index level to the lowest index level of the precoder. Within the same level, the readout is from the lowest indexed frequency component to the highest indexed frequency component. For example, UE 101 may be configured to read no more precoder components than the payload given by the specified resources. Thus, for example, resource or CSI limits may be provided to UE 101 by gNB 111 or higher layer signaling. In this manner, two-step CSI feedback may be configured by UE 101 in response to exceeding the limits. In the first step, a level H bitmap may be included in the first part or step of the CSI feedback. For example, gNB 111 may determine the size of the feedback based on the bitmap, where the feed size may be constant, and the bitmap indicates the feedback size associated with the precoder included in the second part or step with the second CSI feedback.

[0086] In one example, pruning or elimination can be performed or analyzed based on a top-down approach or a bottom-up approach. Here, one or more bitmaps corresponding to the hierarchical precoding levels can be configured or evaluated based on a bottom-up approach, starting from the lowest indexed hierarchical precoding level in the precoding hierarchy of the hierarchical precoding scheme. For example, the lowest indexed hierarchical precoding level includes a frequency band that is a root frequency portion. Alternatively or additionally, these bitmaps can be configured by UE 101 or evaluated by gNB 111 based on a bottom-up approach, starting from the highest indexed hierarchical precoding level.

[0087] In another aspect, hierarchical coding can be configured as a product of multiple precoders, where a similar process can be applied to one or more parameters. For example, UE 101 can configure a precoder to be parameterized by α and β, such as W(α, β). Here, α and β can be functions of frequency, and the wideband parameter function for α can be averaged over all N subbands, and α h，m It can be to h，m Here it becomes a matter of utilizing different quantization levels for different subtrees, where progressively fewer bits are available for higher levels.

[0088] refer to Figure 5 , showing a similar scheme for hierarchical precoding according to various aspects. Figure 4 Another exemplary precoding hierarchy 500 of the precoding hierarchy 400 is shown. As described above, feedback information from different hierarchical levels can be used in various ways. For example, feedback information from the root level 402 (level 0) to the highest indexed level (level 3) can be utilized. This can take the form of a product of precoders applied at different hierarchical levels or a selection of precoders applied at different hierarchical levels, corresponding to unpruned leaves or unpruned subbands in the hierarchical tree structure of the precoding hierarchy 500. The reading or determination at gNB 111 of the correspondence between precoders and CSI feedback locations can be from the lowest indexed level (i.e., level 0) to the highest indexed level (i.e., level H). At the same level, the reading (presentation, processing, or other means of evaluation or provision) can be from the lowest indexed frequency portion to the highest indexed frequency portion. For example, the evaluation or reading of the corresponding precoder for CSI feedback can begin at the highest indexed level. If a leaf (i.e., frequency portion or subband) is "0," the leaf may be pruned; otherwise, the leaf is not pruned, where the corresponding bitmap bit may be "1" (or vice versa). For another index level, if both sub-leaves of a leaf are "0", the leaf is pruned, otherwise the leaf is not pruned.

[0089] Alternatively or in addition, a hierarchical precoding level of frequency portions (e.g., level 2) may have more than one non-pruned frequency portion, wherein although Figure 5 The child nodes (424 and 426) of are pruned, but the frequency portion corresponding to portion 412 may still be reported and determined in the CSI feedback. For example, level 2 may include bits [0 0 1 1].

[0090] Additionally or alternatively, for the highest index level, if a leaf (as a frequency portion or subband) is "0", then the leaf is pruned or marked for omission; otherwise, the leaf is not pruned or marked for omission. For leaves at levels between the highest index level and the top level (root level), if the leaf is "0", then the leaf is pruned or marked for omission; if the leaf is "1", if at least one sub-leaf is "0", then the leaf is not pruned or marked for omission, otherwise (both sub-leafs are "1"), then the leaf is pruned or marked for omission. For the top level, if at least one sub-leaf is "0", then the leaf is not pruned or marked for omission, otherwise (both sub-leafs are "1"), then the leaf is pruned or marked for omission. The precoder for the pruned leaf (or the leaf marked for omission) is not included in the CSI feedback. Note that this pruning process can be used for the case where a single bitmap for the highest index level is fed back by the UE, and can also be used for the case where bitmaps for multiple or all hierarchical levels are fed back by the UE. In case of bitmaps for multiple or all hierarchical levels, they are included in the first part of the CSI report.

[0091] Additionally or alternatively, gNB 111 may reconstruct the applicable precoder from the CSI feedback in a sequence from bottom to top, or from the highest index level to the lowest index level (or vice versa), and from left to right, or from the lowest index frequency portion to the highest index frequency portion, at each level. For example, subband 432 may have its own precoder, while subbands 424 or 426 may have a precoder derived from parent 412, and subband 430 may have a precoder derived from parent 414. Subbands 416, 418, 420, and 422 may have a precoder derived from great-grandfather 402. Working in reverse from the highest index level to the lowest index level, the precoder used for the parent will apply to the child.

[0092] refer to Figure 6, illustrates an exemplary process flow 600 for a network device or component (e.g., UE 101, base station 110, AP 106, or other network component) to implement a hierarchical precoding scheme according to various aspects / implementations described herein. Process flow 600 begins at 602, where a CSI-RS within one or more OFDM symbols is received. At 604, in accordance with any one or more aspects described herein, the process flow further includes generating channel state information (CSI) feedback based on a hierarchical precoding scheme that selectively reduces feedback overhead associated with the CSI feedback. The UE may further transmit the CSI feedback to a base station.

[0093] In one aspect, the UE 101 may, for example, subdivide a frequency band of a hierarchical precoding level into frequency portions at one or more lower hierarchical levels for the hierarchical precoding scheme. For example, subdividing the frequency portions at one or more hierarchical levels into subbands may be performed to form a subtree of the precoding hierarchy, wherein the frequency portions comprise equally divided frequency portions of the frequency band, and the subbands comprise a highest indexed hierarchical precoding level for the hierarchical precoding scheme.

[0094] In response to CSI feedback that exceeds the feedback payload limit, CSI feedback may be generated in two parts by providing a bitmap of subbands indicating which of the subbands or frequency parts are associated with the CSI feedback and further providing CSI feedback associated with a precoding matrix index (PMI) precoder based on a hierarchical precoding scheme.

[0095] refer to Figure 7 , illustrates an example process flow 700 for a network device or component (e.g., eNB / gNB 111, base station 110, AP 106, or other network component) to implement a hierarchical precoding scheme according to various aspects / embodiments described herein. Process flow 700 begins at 702, where a channel state information reference signal (CSI-RS) for CSI feedback is provided. At 704, the process flow includes receiving CSI feedback for frequency portions corresponding to hierarchical precoding levels of a wideband frequency based on the hierarchical precoding scheme.

[0096] In one aspect, gNB 111 or other network components may determine which precoders correspond to one or more frequency portions or one or more subbands for a hierarchical precoding level associated with the CSI feedback to pair the CSI feedback with a physical channel for the UE. The precoders may be configured based on the product of a first matrix for the hierarchical precoding levels and a second matrix for the hierarchical precoding scheme, where the first matrix includes CSI-RS port numbers and the second matrix is ​​rank-dependent based on a feedback rank indicator (RI). Alternatively or additionally, the precoders may be configured based on a separate matrix of CSI-RS port numbers with rank values.

[0097] Bitmaps corresponding to the hierarchical precoding levels can be further generated based on a bottom-up approach starting from the first hierarchical level (including the root frequency portion) or a bottom-up approach starting from the highest indexed hierarchical level (including the frequency portions within the subtree branch partition of the subband derived from the root frequency portion). These can then be used to evaluate or reconstruct CSI feedback.

[0098] In one aspect, for example, a payload limit associated with CSI feedback may be provided by gNB 111 or received by UE 101. In response to the CSI feedback exceeding the payload limit, a bitmap indicating one or more precoders associated with the CSI feedback and other precoders omitted from the CSI feedback may be received and processed, while receiving a second CSI feedback based on the payload size indicated by the bitmap. The size of the feedback may be further determined based on the bitmap for allocating resources accordingly.

[0099] As used in this specification, the term "processor" may refer to substantially any computational processing unit or device, including but not limited to a single-core processor; a single processor with software multi-threaded execution capability; a multi-core processor; a multi-core processor with software multi-threaded execution capability; a multi-core processor with hardware multi-threading technology; a parallel platform; and a parallel platform with distributed shared memory. In addition, a processor may refer to an integrated circuit, an application-specific integrated circuit, a digital signal processor, a field programmable gate array, a programmable logic controller, a complex programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions and / or processes described herein. The processor may utilize nanoscale architectures, such as, but not limited to, molecular and quantum dot-based transistors, switches, and gates, in order to optimize space usage or enhance performance of mobile devices. The processor may also be implemented as a combination of computational processing units.

[0100] Embodiments (implementations) may include subject matter such as a method, an apparatus for performing the actions or blocks of the method, and at least one machine-readable medium comprising instructions that, when executed by a machine (e.g., a processor with memory, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), etc.), cause the machine to perform the actions of a method or apparatus or system for concurrent communication using multiple communication technologies according to the embodiments and examples described herein.

[0101] The first embodiment is a user equipment (UE) device comprising: a memory; a processor configured to: receive a channel state information reference signal (CSI-RS) within one or more orthogonal frequency division multiplexing (OFDM) symbols; generate channel state information (CSI) feedback based on a hierarchical precoding scheme that selectively reduces feedback overhead associated with the CSI feedback; and transmit the CSI feedback to a base station.

[0102] A second embodiment may include the first embodiment, wherein the processor is further configured to subdivide the frequency band into different hierarchical precoding levels of a precoding hierarchy for a hierarchical precoding scheme.

[0103] A third embodiment may include the first or second embodiment, wherein the different hierarchical precoding levels of the precoding hierarchy include: at least one hierarchical precoding level, the at least one hierarchical precoding level including a frequency portion of a frequency band; and at least one other hierarchical precoding level, the at least one other hierarchical precoding level being lower than the at least one hierarchical precoding level.

[0104] A fourth embodiment may include any one or more of the first to third embodiments, wherein the at least one other hierarchical precoding level includes subbands formed as subtrees of the precoding hierarchy from frequency portions of the at least one hierarchical precoding level.

[0105] The fifth embodiment may include any one or more of the first to fourth embodiments, wherein the processor is further configured to: select (map, determine or identify) a subband at a highest index level of a precoding hierarchy for a precoder for CSI feedback.

[0106] The sixth embodiment may include any one or more embodiments of the first to fifth embodiments, wherein the processor is further configured to: generate CSI feedback including a bitmap indicating non-pruned subbands and pruned subbands among subbands of a highest indexed hierarchical precoding level of a precoding hierarchy structure for a hierarchical precoding scheme.

[0107] The seventh embodiment may include any one or more embodiments of the first to sixth embodiments, wherein the processor is further configured to: generate CSI feedback according to the bitmap, the CSI feedback including feedback of precoders corresponding to frequency portions with non-pruned subbands from a lowest indexed hierarchical precoding level to a highest indexed hierarchical precoding level, and increasing with frequency portion indices at the same hierarchical precoding level.

[0108] The eighth embodiment may include any one or more embodiments of the first to seventh embodiments, wherein the processor is further configured to: provide feedback including one or more of the following: a CSI-RS resource indicator (CRI), a rank indicator (RI), a wideband channel quality indicator (CQI) for a first transport block, a subband CQI for a first transport block with an increasing order of subband indices, wherein a bitmap indicates non-pruned subbands and pruned subbands among subbands of a highest indexed hierarchical precoding level; and other precoder construction information in a first part of the CSI feedback; and if RI>4, provide feedback including a wideband CQI for a second transport block and a subband CQI for a second transport block, and a precoder generated according to the bitmap in a second part of the CSI feedback.

[0109] The ninth embodiment may include any one or more of the first to eighth embodiments, wherein the size of the bitmap is the number of subbands at the highest indexed hierarchical precoding level, the subbands including both pruned subbands and non-pruned subbands.

[0110] The tenth embodiment may include any one or more of the first to ninth embodiments, wherein the processor is further configured to: determine the precoder at one or more hierarchical precoding levels based on at least one of the following: N tx xR or N tx xR1, where N tx includes a CSI-RS port number, and R includes a feedback rank indicator (RI), and R1 is greater than R.

[0111] The eleventh embodiment may include any one or more embodiments of the first to tenth embodiments, wherein the processor is further configured to: generate a hierarchical precoding scheme based on an overhead reduction mechanism, the overhead reduction mechanism including distinguishing the feedback overhead of CSI feedback among the hierarchical precoding levels of the precoding hierarchy.

[0112] The twelfth embodiment may include any one or more of the first to eleventh embodiments, wherein the feedback overhead among the hierarchical precoding levels is less at a higher indexed hierarchical precoding level of the precoding hierarchy than at a lower indexed hierarchical precoding level of the precoding hierarchy.

[0113] The thirteenth embodiment may include any one or more embodiments of the first to twelfth embodiments, wherein the processor is further configured to: prune one or more hierarchical precoding levels of frequency portions or subbands based on an overhead reduction mechanism for CSI feedback; and generate a bitmap indicating non-pruned subbands and pruned subbands associated with the CSI feedback.

[0114] The fourteenth embodiment may include any one or more embodiments of the first to thirteenth embodiments, wherein the processor is further configured to: determine different partitions of the frequency portion of the frequency band based on a predetermined size, or adapt the size of the different partitions based on the parent frequency portion of the lower index hierarchical level, so that approximately equal parts of the different partitions are allocated to the sub-band partitions of the higher index hierarchical level for the hierarchical precoding scheme.

[0115] The fifteenth embodiment may include any one or more embodiments of the first to fourteenth embodiments, wherein the processor is further configured to: generate a precoder codebook having a precoder for CSI feedback, the precoder codebook comprising a rotation angle of gradually coarser resolution at a lower index hierarchical precoding level compared to a higher index hierarchical precoding level comprising a frequency portion or subband of a frequency band for a hierarchical precoding scheme.

[0116] The sixteenth embodiment may include any one or more embodiments of the first to fifteenth embodiments, wherein the processor is further configured to: generate CSI feedback based on an omission rule, wherein the omission rule includes: in response to a feedback overhead of the CSI feedback not exceeding a resource limit derived from at least one of a network configuration or a network signaling, including one or more precoders for CSI feedback from a lowest index hierarchical precoding level to a highest index hierarchical precoding level in the CSI feedback; and generate CSI feedback based on the omission rule for omitting one or more precoders at a hierarchical precoding level indexed higher than the lowest index precoding level, the CSI feedback including feedback of one or more precoders corresponding to frequency portions of non-pruned subbands from the lowest index hierarchical precoding level to the highest index hierarchical precoding level, and increasing with the frequency portion index at the same hierarchical precoding level until the resource limit is reached.

[0117] The seventeenth embodiment may include any one or more embodiments of the first to sixteenth embodiments, wherein the processor is further configured to: provide feedback comprising one or more of: a CSI-RS resource indicator (CRI), a rank indicator (RI), a wideband channel quality indicator (CQI) for a first transport block, a subband CQI for a first transport block with an increasing order of subband indices, wherein a bitmap indicates non-pruned subbands and pruned subbands among subbands of a highest indexed hierarchical precoding level; and other precoder construction information in a first part of the CSI feedback; and if RI>4, provide feedback comprising a wideband CQI for a second transport block and a subband CQI for a second transport block, and one or more precoders generated from the bitmap in a second part of the CSI feedback.

[0118] An eighteenth embodiment may include any one or more of the first to seventeenth embodiments, wherein the processor is further configured to: average one or more parameters as a function of frequency within a sub-band range of a frequency portion associated with a frequency band; and apply the one or more parameters across one or more hierarchical precoding levels of a hierarchical precoding scheme.

[0119] The nineteenth embodiment is a tangible computer-readable storage device that stores executable instructions that, in response to execution, cause one or more processors of a user equipment (UE) to perform operations, the operations comprising: receiving a channel state information reference signal (CSI-RS) within one or more orthogonal frequency division multiplexing (OFDM) symbols; and generating channel state information (CSI) feedback based on a hierarchical precoding scheme that selectively reduces feedback overhead associated with the CSI feedback.

[0120] The twentieth embodiment may include the nineteenth embodiment, wherein the operations further comprise: subdividing a frequency band of a hierarchical precoding level into frequency portions at one or more lower hierarchical levels.

[0121] The twenty-first embodiment may include any one or more of the nineteenth to twentieth embodiments, wherein the operations further comprise: subdividing frequency portions at one or more hierarchical levels into subbands to form subtrees of a precoding hierarchical structure, wherein the frequency portions comprise equally divided frequency portions of the frequency band, and the subbands comprise a highest indexed hierarchical precoding level for the hierarchical precoding scheme.

[0122] The twenty-second embodiment may include any one or more of the nineteenth to twenty-first embodiments, wherein the operations further comprise: in response to the CSI feedback exceeding the feedback payload limit, generating CSI feedback in two parts by providing a bitmap of subbands indicating which of the subbands are associated with the CSI feedback and further providing CSI feedback including a precoding matrix index (PMI) precoder based on a hierarchical precoding scheme.

[0123] The twenty-third embodiment may be a baseband processor comprising: a memory; a processor configured to: receive a channel state information reference signal (CSI-RS) within one or more orthogonal frequency division multiplexing (OFDM) symbols; determine frequency portions of a frequency band and a subband from the frequency portions to be configured at different hierarchical levels in a hierarchical precoding scheme that selectively reduces feedback overhead associated with channel state information (CSI) feedback; and generate CSI feedback based on a precoding hierarchy of the hierarchical precoding scheme.

[0124] A twenty-fourth embodiment may include the twenty-third embodiment, wherein the processor is further configured to prune subtrees of the precoding hierarchy formed from the frequency parts or subbands based on precoder differences between the subbands.

[0125] The twenty-fifth embodiment may be a next-generation Node B (gNB), comprising: a memory; one or more processors configured to: transmit a channel state information reference signal (CSI-RS) for CSI feedback; and in response to providing the CSI-RS, receive channel state information (CSI) feedback corresponding to one or more frequency parts of a hierarchical precoding level in a frequency band based on a hierarchical precoding scheme.

[0126] The twenty-sixth embodiment may include the twenty-fifth embodiment, wherein the hierarchical precoding levels include a highest index precoding level including subbands subdivided from one or more frequency parts for the hierarchical precoding scheme.

[0127] A twenty-seventh embodiment may include any one of the twenty-fifth to twenty-sixth embodiments, wherein the lowest indexed hierarchical precoding level includes a frequency band as a root frequency portion.

[0128] The twenty-eighth embodiment may include any one of embodiments twenty-fifth to twenty-seventh, wherein the CSI feedback includes one or more bitmaps indicating non-pruned subbands and one or more pruned subbands among the subbands and frequency parts of one or more hierarchical precoding levels in a precoding hierarchy structure for a hierarchical precoding scheme.

[0129] The twenty-ninth embodiment may include any one of the twenty-fifth to twenty-eighth embodiments, identifying non-pruned subbands and one or more pruned subbands among subbands and frequency parts of one or more hierarchical precoding levels of a precoding hierarchy structure for a hierarchical precoding scheme based on one or more bitmaps; and mapping a precoder received from CSI feedback to one or more non-pruned subbands among the non-pruned subbands at the one or more hierarchical precoding levels.

[0130] A thirtieth embodiment may include any one of embodiments twenty-fifth to twenty-ninth, wherein the one or more processors are further configured to map a precoder received in the CSI feedback to a hierarchical precoding level for a frequency band.

[0131] A thirty-first embodiment may include any one of embodiments twenty-fifth to thirtieth, wherein the one or more processors are further configured to determine a precoder based on CSI feedback based on a hierarchical precoding scheme.

[0132] The thirty-second embodiment may include any one of embodiments twenty-fifth to thirty-first, wherein the one or more processors are further configured to determine which precoder positions to eliminate from the CSI feedback and the precoder positions at the hierarchical precoding levels associated with the CSI feedback.

[0133] The thirty-third embodiment may include any one of embodiments twenty-fifth to thirty-second, wherein the one or more processors are further configured to: map the precoder of the CSI feedback into a hierarchical tree structure of hierarchical precoding levels; and based on the hierarchical precoding scheme, determine which subtrees of the hierarchical tree structure are pruned according to the CSI feedback, wherein the subtrees are derived from frequency portions of the frequency bands at the hierarchical precoding levels.

[0134] The thirty-fourth embodiment may include any one of embodiments twenty-fifth to thirty-third, wherein the one or more processors are further configured to: in response to the CSI feedback exceeding the payload limit, determine the feedback size based on one or more bitmaps for the second CSI feedback.

[0135] The thirty-fifth embodiment may include any one of embodiments twenty-fifth to thirty-fourth, wherein one or more precoders associated with the CSI feedback are parameterized by one or more parameters that are a function of frequency and averaged across subbands of one or more frequency portions for a hierarchical precoding scheme.

[0136] The thirty-sixth embodiment may be a tangible computer-readable storage device storing executable instructions that, in response to execution, cause one or more processors of a network device including an access point or a next-generation Node B (gNB) to perform operations including: providing a channel state information reference signal (CSI-RS) for CSI feedback; and receiving CSI feedback for a frequency portion of a hierarchical precoding level corresponding to a wideband frequency based on a hierarchical precoding scheme.

[0137] The thirty-seventh embodiment may include the thirty-sixth embodiment, wherein the operations further include: determining which precoders of one or more frequency portions or one or more subbands corresponding to the hierarchical precoding levels are associated with the CSI feedback to pair the CSI feedback with a physical channel for a user equipment (UE).

[0138] The thirty-eighth embodiment may include any one of the thirty-sixth to thirty-seventh embodiments, wherein the precoder, wherein the precoder is configured based on the product of a first matrix and a second matrix for a hierarchical precoding level for a hierarchical precoding scheme, wherein the first matrix includes CSI-RS port numbers and the second matrix is ​​rank-related based on a feedback rank indicator (RI).

[0139] The thirty-ninth embodiment may include any one of the thirty-sixth to thirty-eighth embodiments, wherein the operations further include: determining one or more bitmaps corresponding to the hierarchical precoding levels respectively based on a bottom-up approach, the bottom-up approach starting from the highest indexed hierarchical level, the highest indexed hierarchical level including frequency portions within a subtree branch partition of a subband derived from a root frequency portion.

[0140] A fortieth embodiment may include any one of embodiments thirty-sixth to thirty-ninth, wherein the operations further comprise: providing a payload limit associated with the CSI feedback; and in response to the CSI feedback exceeding the payload limit: receiving a bitmap indicating one or more precoders associated with the CSI feedback and other precoders omitted from the CSI feedback in response to the CSI feedback exceeding the payload limit; and receiving a second CSI feedback based on the payload size indicated by the bitmap.

[0141] The forty-first embodiment may include any one of the thirty-sixth to fortieth embodiments, wherein the feedback overhead among the hierarchical precoding levels is less at a higher indexed hierarchical precoding level than at a higher hierarchical precoding level with a lower feedback priority of the precoding hierarchy.

[0142] The forty-second embodiment may be a baseband processor comprising: a memory; a processing circuit configured to: provide a channel state information reference signal (CSI-RS) for CSI feedback; and receive channel state information (CSI) feedback corresponding to one or more frequency portions of a frequency band based on a hierarchical precoding scheme.

[0143] The forty-third embodiment may include the forty-second embodiment, wherein the processing circuit is further configured to: determine which precoders are associated with the CSI feedback and which precoders are omitted from the CSI feedback based on one or more bitmaps corresponding to the hierarchical precoding levels, respectively.

[0144] The forty-fourth embodiment may include any one of embodiments forty-second to forty-third, wherein the processing circuit is further configured to: in response to the CSI feedback exceeding the payload limit: receive a bitmap indicating one or more precoders associated with the CSI feedback and other precoders omitted from the CSI feedback in response to the CSI feedback exceeding the payload limit; and receive a second CSI feedback based on the payload size indicated by the bitmap.

[0145] In addition, the various aspects or features described herein can be implemented as methods, devices or products using standard programming and / or engineering techniques. As used herein, the term "product" is intended to cover computer programs that can be accessed from any computer-readable device, carrier or medium. For example, computer-readable media may include, but are not limited to, magnetic storage devices (e.g., hard disks, floppy disks, magnetic strips), optical disks (e.g., compact disks (CDs), digital versatile disks (DVDs), etc.), smart cards, and flash memory devices (e.g., EPROMs, cards, sticks, key drives, etc.). In addition, the various storage media described herein may represent one or more devices and / or other machine-readable media for storing information. The term "machine-readable medium" may include, but is not limited to, wireless channels and various other media capable of storing, containing and / or carrying instructions and / or data. In addition, a computer program product may include a computer-readable medium having one or more instructions or codes that are operable to cause a computer to perform the functions described herein.

[0146] Communication media embodies computer-readable instructions, data structures, program modules, or other structured or unstructured data in a data signal, such as a modulated data signal, such as a carrier wave, or other transport mechanism, and includes any information delivery or transmission media. The term "modulated data signal" or signal refers to a signal that has one or more characteristics set or changed in such a manner as to encode information in one or more signals. By way of example, and not limitation, communication media includes wired media, such as a wired network or direct-wired connection, and wireless media, such as acoustic, RF, infrared, and other wireless media.

[0147] An exemplary storage medium may be coupled to a processor so that the processor can read information from the storage medium and write information to the storage medium. In an alternative, the storage medium may be integrated with the processor. Furthermore, in some aspects, the processor and the storage medium may reside in an ASIC. Additionally, the ASIC may reside in a user terminal. In an alternative, the processor and the storage medium may reside in a user terminal as discrete components. Furthermore, in some aspects, the processes and / or actions of the method or algorithm may reside on a machine-readable medium and / or computer-readable medium as one or any combination or set of codes and / or instructions and may be incorporated into a computer program product.

[0148] In this regard, although the subject matter disclosed herein has been described in conjunction with various embodiments and corresponding drawings, it should be understood that other similar embodiments may be used or modifications and additions may be made to the described embodiments to perform the same, similar, alternative, or alternative functions of the disclosed subject matter without departing from the described embodiments. Accordingly, the disclosed subject matter should not be limited to any single embodiment described herein, but rather should be construed in accordance with the breadth and scope of the claims appended hereto.

[0149] In particular, with respect to the various functions performed by the aforementioned components (assemblies, devices, circuits, systems, etc.), unless otherwise indicated, terms used to describe such components (including references to "means") are intended to correspond to any component or structure that performs the specified function of the component (e.g., functionally equivalent), even if not structurally equivalent to the disclosed structure that performs the function in the exemplary implementations of the disclosure shown herein. In addition, while particular features have been disclosed with respect to only one of several implementations, for any given or particular application, such features may be combined with one or more other features of other implementations, as may be desirable and advantageous.

Claims

1. A user equipment (UE), comprising: Memory; A processor configured to: Receiving a channel state information reference signal CSI-RS in one or more orthogonal frequency division multiplexing (OFDM) symbols; as well as Channel state information (CSI) feedback is generated based on a hierarchical precoding scheme that selectively reduces feedback overhead associated with the CSI feedback, and a precoder codebook is generated having a precoder for the CSI feedback, the hierarchical precoding scheme selectively reducing feedback overhead associated with the CSI feedback, the precoder codebook comprising progressively coarser resolution for rotation angles at lower indexed hierarchical precoding levels than for rotation angles at higher indexed hierarchical precoding levels, the higher indexed hierarchical precoding levels comprising frequency portions or subbands of a frequency band used for the hierarchical precoding scheme, wherein the CSI feedback comprises a bitmap indicating non-pruned subbands and pruned subbands among the subbands for each hierarchical precoding level of a precoding hierarchy for the hierarchical precoding scheme.

2. The UE according to claim 1, wherein the processor is further configured to: subdividing a frequency band into different hierarchical precoding levels of a precoding hierarchy for the hierarchical precoding scheme; The different hierarchical precoding levels of the precoding hierarchy structure include: at least one hierarchical precoding level, the at least one hierarchical precoding level comprising a frequency portion of the frequency band; and at least one other hierarchical precoding level, the at least one other hierarchical precoding level being lower than the at least one hierarchical precoding level, and wherein the at least one other hierarchical precoding level comprises subbands formed as a subtree of the precoding hierarchy from the frequency portion of the at least one hierarchical precoding level.

3. The UE according to claim 1, wherein the processor is further configured to: The CSI feedback is generated according to the bitmap, the CSI feedback including feedback of precoders corresponding to frequency portions having non-pruned subbands from a lowest-indexed hierarchical precoding level to a highest-indexed hierarchical precoding level, and the feedback of the precoders increases with frequency portion index at the same hierarchical precoding level.

4. The UE according to claim 3, wherein the processor is further configured to: providing feedback comprising one or more of: a CSI-RS resource indicator (CRI), a rank indicator (RI), a wideband channel quality indicator (CQI) for a first transport block, subband CQIs for the first transport block in increasing order of subband indices, wherein the bitmap indicates the non-pruned subbands and the pruned subbands among the subbands of the highest indexed hierarchical precoding level; and other precoder construction information in a first part of the CSI feedback; and If RI>4, providing feedback including a wideband CQI for a second transport block and a subband CQI for the second transport block, and providing a precoder generated according to the bitmap in the second part of the CSI feedback. 5 . The UE of claim 4 , wherein the size of the bitmap at the hierarchical precoding level is the number of subbands at the highest indexed hierarchical precoding level, the subbands including both pruned subbands and non-pruned subbands.

6. The UE according to claim 1, wherein the processor is further configured to: The precoders at one or more hierarchical precoding levels are determined based on at least one of the following: tx ×R or N tx ×R1, where N tx includes the CSI-RS port number, and R includes the feedback rank indicator RI, and R1 is greater than R.

7. The UE according to claim 1, wherein the processor is further configured to: The hierarchical precoding scheme is generated based on an overhead reduction mechanism including differentiating the feedback overhead of the CSI feedback among hierarchical precoding levels of a precoding hierarchy.

8. The UE of claim 7, wherein the feedback overhead among the hierarchical precoding levels is less at a higher indexed hierarchical precoding level of the precoding hierarchy than at a lower indexed hierarchical precoding level of the precoding hierarchy.

9. The UE according to claim 1, wherein the processor is further configured to: pruning one or more hierarchical precoding levels of frequency parts or subbands based on an overhead reduction mechanism for said CSI feedback; The bitmap indicates non-pruned subbands and pruned subbands associated with the CSI feedback.

10. The UE according to claim 1, wherein the processor is further configured to: The different partitions of the frequency parts of the frequency band are determined based on a predetermined size, or the sizes of the different partitions are adapted based on the parent frequency parts of the lower index hierarchical level, so that approximately equal parts of the different partitions are allocated to the sub-band partitions of the higher index hierarchical level for the hierarchical precoding scheme.

11. The UE according to claim 1 , wherein the processor is further configured to: The CSI feedback is generated based on an omission rule, wherein the omission rule comprises: In response to the feedback overhead of the CSI feedback not exceeding a resource limit derived from at least one of a network configuration or network signaling, including one or more precoders from a lowest indexed hierarchical precoding level to a highest indexed hierarchical precoding level in the CSI feedback; as well as The CSI feedback is generated based on the omission rule for omitting one or more precoders at the highest indexed hierarchical precoding level or one or more hierarchical precoding levels indexed higher than the lowest indexed hierarchical precoding level, the CSI feedback including feedback of one or more precoders corresponding to frequency portions having non-pruned subbands from the lowest indexed hierarchical precoding level to the highest indexed hierarchical precoding level, and the feedback of the precoders increases with frequency portion index at the same hierarchical precoding level until the resource limit is reached.

12. The UE according to claim 11, wherein the processor is further configured to: providing feedback comprising one or more of: a CSI-RS resource indicator (CRI), a rank indicator (RI), a wideband channel quality indicator (CQI) for a first transport block, subband CQIs for the first transport block in increasing order of subband indices, wherein the bitmap indicates the non-pruned subbands and the pruned subbands among the subbands for each hierarchical precoding level; and other precoder construction information in a first part of the CSI feedback; and If RI>4, providing feedback including a wideband CQI for a second transport block and a subband CQI for the second transport block, and providing one or more precoders generated from the bitmap in the second part of the CSI feedback.

13. The UE according to claim 1, wherein the processor is further configured to: averaging one or more parameters as a function of frequency within a sub-band of a frequency portion associated with the frequency band; and The one or more parameters are applied across one or more hierarchical precoding levels of the hierarchical precoding scheme.

14. A tangible computer-readable storage device storing executable instructions that, in response to execution, cause one or more processors of user equipment (UE) to perform operations comprising: Receiving a channel state information reference signal CSI-RS in one or more orthogonal frequency division multiplexing (OFDM) symbols; subdividing a frequency band at a hierarchical precoding level into frequency portions at one or more lower hierarchical levels; subdividing the frequency portions at the one or more lower hierarchical levels into subbands to form subtrees of a precoding hierarchy, wherein the frequency portions comprise equally divided frequency portions of the frequency band and the subbands comprise a highest indexed hierarchical precoding level for a hierarchical precoding scheme; as well as Channel state information (CSI) feedback is generated based on a hierarchical precoding scheme that selectively reduces feedback overhead associated with the CSI feedback.

15. The tangible computer-readable storage device of claim 14, wherein the operations further comprise: In response to the CSI feedback exceeding the feedback payload limit: The CSI feedback is generated in two parts by providing a bitmap of subbands indicating which of the subbands are associated with the CSI feedback and further providing the CSI feedback including a precoding matrix index (PMI) precoder based on the hierarchical precoding scheme.

16. A baseband processor, comprising: Memory; A processor configured to: Receiving a channel state information reference signal CSI-RS in one or more orthogonal frequency division multiplexing (OFDM) symbols; In a hierarchical precoding scheme for selectively reducing feedback overhead associated with channel state information (CSI) feedback, frequency portions of frequency bands and subbands are determined from frequency portions to be configured at different hierarchical levels; pruning a subtree of a precoding hierarchy formed from the subbands based on a difference in precoders between the frequency parts or the subbands; generating a precoder codebook with a precoder for the CSI feedback, the precoder codebook comprising progressively coarser resolution for rotation angles at lower indexed hierarchical precoding levels than for rotation angles at higher indexed hierarchical precoding levels, the higher indexed hierarchical precoding levels comprising frequency portions or subbands of a frequency band used for the hierarchical precoding scheme; and The CSI feedback is generated based on a precoding hierarchy of the hierarchical precoding scheme.

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