Apparatus, method and computer program

Abstract

A device is provided, the device comprising a component for the following operations: receiving a multiple-input multiple-output signal from a network, determining a frequency domain basis subset for each layer of the multiple-input multiple-output signal; determining the number M of frequency domain components common to each layer from the frequency domain basis subset C , determining the number of layer-specific frequency domain components from the frequency domain basis subset, and providing an indication of the frequency domain components common to each layer and the layer-specific frequency domain components to the network in uplink control information.

Description

Technical Field

[0001] The present application relates to a method, an apparatus, a system and a computer program, and particularly but not exclusively to uplink control information (UCI) design for high-rank channel state information (CSI) feedback. Background Art

[0002] A communication system may be viewed as a facility that enables communication sessions between two or more entities such as user terminals, base stations and / or other nodes by providing carrier waves between the various entities involved in the communication path. A communication system may be provided, for example, by means of a communication network and one or more compatible communication devices (also referred to as stations or user equipment) and / or application servers. A communication session may include, for example, data communications for carrying communications such as voice, video, electronic mail (email), text messages, multimedia, content data, time-sensitive network (TSN) streams and / or data in industrial applications, such as critical system messages between actuators and controllers, critical sensor data (such as measurements, video feeds, etc.) towards a control system, and the like. Non-limiting examples of the services provided include two-way or multi-way calls, data communications or multimedia services, and access to data network systems such as the Internet.

[0003] In a wireless communication system, at least a part of a communication session, e.g. between at least two stations or between at least one station and at least one application server (e.g. for video), takes place over a wireless link. Examples of wireless systems include public land mobile networks (PLMNs) operating based on 3GPP radio standards such as E-UTRA, new radio, satellite-based communication systems, and different wireless local area networks, e.g. wireless local area networks (WLANs). Wireless systems are typically divided into cells and are therefore often referred to as cellular systems.

[0004] A user can access a communication system with the aid of an appropriate communication device or terminal. The user's communication device may be referred to as a user equipment (UE) or user equipment. The communication device is provided with appropriate signal receiving and sending means for implementing communication, such as implementing access to a communication network or communicating directly with other users. The communication device may access one or more carriers provided by a network (e.g., a base station of a cell) and send and / or receive communications on one or more carriers.

[0005] A communication system and associated equipment typically operate according to a given standard or specification that states what the various entities associated with the system are allowed to do and how it should be implemented. Communication protocols and / or parameters that should be used for connections are also typically defined. An example of a communication system is UTRAN (3G radio). Other examples of communication systems are the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) based on E-UTRAN radio access technology, and the so-called 5G System (5GS) including 5G or Next Generation Core (NGC) and a 5G access network based on New Radio (NR) radio access technology. 5GS including NR is being standardized by the Third Generation Partnership Project (3GPP). Summary of the invention

[0006] In a first aspect, an apparatus is provided, comprising: receiving a multiple-input multiple-output signal from a network; determining a frequency domain basis subset for each layer of the multiple-input multiple-output signal; determining the number M of frequency domain components common to each layer from the frequency domain basis subset C ; determining the number of layer-specific frequency domain components from the frequency domain basis subset; and providing a component for the network to indicate the frequency domain components common to each layer and the frequency domain components specific to the layer.

[0007] The apparatus may include means for providing the indication in uplink control information.

[0008] The apparatus may comprise means for determining the subset of frequency domain bases for each layer independently, commonly or in a partially common manner.

[0009] The apparatus may include a method for determining M C So that the maximum number of non-zero coefficients are concentrated in M C components in the frequency domain.

[0010] M C It may be determined according to a predetermined number of layers.

[0011] The predetermined number of layers may be the first two of the layers or any combination of the layers.

[0012] The apparatus may include means for determining non-zero coefficients that are commonly mapped to each layer and providing an indication of the non-zero coefficients to a network.

[0013] The apparatus may include means for determining non-zero coefficients that are mapped independently by layer; and providing an indication of the non-zero coefficients to a network.

[0014] The apparatus may include means for providing an indication of the non-zero coefficients in uplink control information.

[0015] The signal may be a channel state information reference signal.

[0016] In a second aspect, a method is provided, comprising: receiving a multiple-input multiple-output signal from a network; determining a frequency domain basis subset for each layer of the multiple-input multiple-output signal; determining a number M of frequency domain components common to each layer from the frequency domain basis subset C ; determining the number of layer-specific frequency domain components from the frequency domain basis subset; and providing an indication to the network of the frequency domain components common to each layer and the layer-specific frequency domain components.

[0017] The method may include providing the indication in uplink control information.

[0018] The method may include determining the frequency domain basis subset for each layer independently, commonly, or in a partially common manner.

[0019] The method may include determining M C So that the maximum number of non-zero coefficients are concentrated in M C frequency domain components.

[0020] M C It may be determined according to a predetermined number of layers.

[0021] The predetermined number of layers may be the first two of the layers or any combination of the layers.

[0022] The method may include determining non-zero coefficients that are commonly mapped to each layer and providing an indication of the non-zero coefficients to a network.

[0023] The method may include determining non-zero coefficients that are mapped independently by layer; and providing an indication of the non-zero coefficients to a network.

[0024] The method may comprise providing an indication of the non-zero coefficients in uplink control information.

[0025] The signal may be a channel state information reference signal.

[0026] In a third aspect, an apparatus is provided, comprising at least one processor and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the apparatus to at least receive a multiple-input multiple-output signal from a network; determine a frequency domain basis subset for each layer of the multiple-input multiple-output signal; determine the number M of frequency domain components common to each layer from the frequency domain basis subset C ; determining the number of layer-specific frequency domain components from the frequency domain basis subset; and providing an indication to the network of the frequency domain components common to each layer and the layer-specific frequency domain components.

[0027] The apparatus may be configured to provide the indication in uplink control information.

[0028] The apparatus may be configured to determine the frequency domain basis subset for each layer independently, commonly or in a partially common manner.

[0029] The device may be configured to determine M C So that the maximum number of non-zero coefficients are concentrated in M C frequency domain components.

[0030] M C It may be determined according to a predetermined number of layers.

[0031] The predetermined number of layers may be the first two of the layers or any combination of the layers.

[0032] The apparatus may be configured to determine non-zero coefficients that are commonly mapped to each layer and to provide an indication of the non-zero coefficients to the network.

[0033] The apparatus may be configured to determine non-zero coefficients that are mapped independently per layer; and provide an indication of the non-zero coefficients to a network.

[0034] The apparatus may be configured to provide an indication of the non-zero coefficients in uplink control information.

[0035] The signal may be a channel state information reference signal.

[0036] In a fourth aspect, a computer-readable medium is provided, comprising program instructions for causing an apparatus to at least perform the following operations: receiving a multiple-input multiple-output signal from a network; determining a frequency domain basis subset for each layer of the multiple-input multiple-output signal; determining the number M of frequency domain components common to each layer from the frequency domain basis subset C ; determining the number of layer-specific frequency domain components from the frequency domain basis subset; and providing an indication to the network of the frequency domain components common to each layer and the layer-specific frequency domain components.

[0037] The apparatus may be caused to perform providing the indication in the uplink control information.

[0038] The apparatus may be caused to perform determining the frequency domain basis subset for each layer independently, commonly or in a partially common manner.

[0039] The apparatus may be caused to perform the determination C So that the maximum number of non-zero coefficients are concentrated in M C frequency domain components.

[0040] M C It may be determined according to a predetermined number of layers.

[0041] The predetermined number of layers may be the first two of the layers or any combination of the layers.

[0042] The apparatus may be caused to perform determining non-zero coefficients that are commonly mapped to each layer and providing an indication of the non-zero coefficients to the network.

[0043] The apparatus may be caused to perform determining non-zero coefficients that are independently mapped per layer; and providing an indication of the non-zero coefficients to a network.

[0044] The apparatus may be caused to perform providing an indication of the non-zero coefficients in uplink control information.

[0045] The signal may be a channel state information reference signal.

[0046] In a fifth aspect, a non-transitory computer readable medium is provided, comprising program instructions for causing an apparatus to at least perform the method according to the second aspect.

[0047] In the above statement, many different embodiments have been described. It should be understood that further embodiments can be provided by combining any two or more of the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0049] Figure 1 A schematic diagram of an example communication system including a base station and a plurality of communication devices is shown;

[0050] Figure 2 A schematic diagram of an example mobile communication device is shown;

[0051] Figure 3 A schematic diagram of an example control device is shown;

[0052] Figure 4 A schematic diagram showing non-zero coefficient (NZC) mapping for FD compression of Type II CSI feedback;

[0053] Figure 5 A flow chart showing a method according to an example embodiment is shown;

[0054] Figure 6 shows a schematic diagram of NZC mapping and FD component selection according to an example embodiment;

[0055] Figure 7 A schematic diagram showing a process at a UE and a gNB according to an example embodiment is shown;

[0056] Figure 8 A schematic diagram showing a process at a UE and a gNB according to an example embodiment is shown;

[0057] Fig. 9 A schematic diagram of the process at the UE and the gNB according to an example embodiment is shown. DETAILED DESCRIPTION

[0058] Before explaining the examples in detail, refer to Figures 1 to 3 Certain general principles of wireless communication systems and mobile communication devices are briefly explained to assist in understanding the underlying basic technology of the described examples.

[0059] In the wireless communication system 100, such as Figure 1 As shown, mobile communication devices or user equipment (UE) 102, 104, 105 are provided with wireless access via at least one base station (e.g., next generation NB, gNB) or similar wireless transmission and / or reception node or point. The base station can be controlled or assisted by at least one appropriate controller device to enable its operation and management of mobile communication devices communicating with the base station. The controller device can be located in a radio access network (e.g., wireless communication system 100) or a core network (CN) (not shown) and can be implemented as a central device, or its functions can be distributed over several devices. The controller device can be part of the base station and / or provided by a separate entity such as a radio network controller. In Figure 1 In the embodiment, control means 108 and 109 are shown as controlling respective macro level base stations 106 and 107. The control means of the base stations may be interconnected with other control entities. The control means are typically provided with memory capacity and at least one data processor. The control means and functions may be distributed between a plurality of control units. In some systems, the control means may additionally or alternatively be provided in a radio network controller.

[0060] exist Figure 1 In FIG. 1 , base stations 106 and 107 are shown connected to a wider communications network 113 via a gateway 112. A further gateway function may be provided to connect to another network.

[0061] Smaller base stations 116, 118, and 120 may also be connected to the network 113 (e.g., via a separate gateway function and / or via a controller of a macro-level station). The base stations 116, 118, and 120 may be pico base stations or femto-level base stations, etc. In this example, the stations 116 and 118 are connected via the gateway 111, while the station 120 is connected via the controller device 108. In some embodiments, smaller stations may not be provided. The smaller base stations 116, 118, and 120 may be part of a second network, such as a WLAN and may be a WLAN AP.

[0062] The communication devices 102, 104, 105 may access the communication system based on various access technologies, such as code division multiple access (CDMA) or wideband CDMA (WCDMA). Other non-limiting examples include time division multiple access (TDMA), frequency division multiple access (FDMA) and various schemes thereof, such as interleaved frequency division multiple access (IFDMA), single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA), space division multiple access (SDMA), etc.

[0063] An example of a wireless communication system is an architecture standardized by the Third Generation Partnership Project (3GPP). Development based on One3GPP is generally referred to as the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio access technology. The various development stages of the 3GPP specification are referred to as releases. More recent developments of LTE are generally referred to as Advanced LTE (LTE-A). LTE (LTE-A) adopts a radio mobile architecture referred to as Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and a core network referred to as Evolved Packet Core (EPC). The base station of such a system is referred to as an evolved or enhanced Node B (eNB), and provides E-UTRAN features to communication devices, such as user plane packet data convergence / radio link control / media access control / physical layer protocol (PDCP / RLC / MAC / PHY) and control plane radio resource control (RRC) protocol termination. Other examples of radio access systems include those provided by base stations of systems based on technologies such as wireless local area networks (WLAN) and / or WiMax (Worldwide Interoperability for Microwave Access). Base stations can provide coverage for an entire cell or similar radio service area. The core network elements include the Mobility Management Entity (MME), the Serving Gateway (S-GW) and the Packet Gateway (P-GW).

[0064] An example of a suitable communication system is the 5G or NR concept. The network architecture in NR may be similar to that of advanced LTE. The base station of the NR system may be referred to as a next generation node B (gNB). Changes to the network architecture structure may depend on the need to support various radio technologies and more refined QoS support, as well as some on-demand requirements for QoS levels such as QoE to support the user's point of view. New functions are defined in the 5G system architecture, including access management function (AMF), session management function (SMF), user plane function (UPF), and other network functions in the next generation core (NGC). The 5G system supports new capabilities, including network slicing, which can better customize the network for application requirements and provide virtual networks for tenants. It also uses a service-based architecture that provides greater flexibility for introducing new services and features compared to the EPC that relies on fixed peer reference points. NR can use multiple input multiple output (MIMO) antennas, many more base stations or nodes than LTE (the so-called small cell concept), including macro sites that operate in conjunction with smaller stations, and may also adopt various radio technologies for better coverage and enhanced data rates. MR can also support lower latency for air interface transmission due to revisions to the physical and MAC layer protocols.

[0065] Future networks may utilize network function virtualization (NFV), which is a network architecture concept that proposes virtualizing network node functions into "building blocks" or entities that can be operationally connected or linked together to provide services. A virtualized network function (VNF) may include one or more virtual machines that use standard or general-purpose servers rather than custom hardware to run computer program code. Cloud computing or data storage may also be utilized. In radio communications, this may mean that node operations are to be implemented by a centralized unit (CU) at least in part in a server, host, or node that is operably coupled to a distributed unit (DU), which may be connected to a remote radio head (RRH). Node operations may also be distributed among multiple servers, nodes, or hosts. It should also be understood that the labor distribution between core network operations and base station operations may be different from that of LTE, or even non-existent.

[0066] Example 5G Core Network (CN) includes functional entities. CN is connected to UE via Radio Access Network (RAN). UPF (User Plane Function) can be PSA (PDU Session Anchor) that provides anchor point for user IP, Ethernet or unstructured user data session. UPF can be responsible for forwarding frames to and from DN (Data Network) and gNB through tunnels established on transport network to (multiple) UEs that want to exchange traffic with DN.

[0067] The UPF is controlled by the SMF (Session Management Function) which receives policies from the PCF (Policy Control Function). The CN may also include an AMF (Access and Mobility Function) which terminates the control plane interface with the RAN and manages UE registration and mobility.

[0068] Now refer to Figure 2 describing in more detail possible mobile communication devices, Figure 2 A schematic partial cross-sectional view of a communication device 200 is shown. Such a communication device is generally referred to as a user equipment (UE) or a terminal. Suitable mobile communication devices can be provided by any device capable of sending and receiving radio signals. Non-limiting examples include a mobile station (MS) or a mobile device such as a mobile phone or a so-called "smart phone", a computer provided with a wireless interface card or other wireless interface device (e.g., a USB dongle), a personal data assistant (PDA), or a tablet computer provided with wireless communication capabilities, or any combination of these, etc. The mobile communication device can provide, for example, data communications for carrying communications such as voice, e-mail (email), text messages, multimedia, etc. Therefore, users can be supplied or provided with a variety of services via their communication devices. Non-limiting examples of these services include two-way or multi-way calls, data communications or multimedia services, or simply access to a data communication network system such as the Internet. Users can also be provided with broadcast or multicast data. Non-limiting examples of content include downloads, television and radio programs, videos, advertisements, various alarms and other information.

[0069] In industrial applications, the communications device may be a modem integrated into an industrial actuator (e.g., a robotic arm) and / or a modem acting as an Ethernet hub that would act as a connection point for one or more connected Ethernet devices (the connection may be wired or wireless).

[0070] The mobile device is typically provided with at least one data processing entity 201, at least one memory 202 and other possible components 203 for software and hardware assistance in performing the tasks it is designed to perform, including controlling access to and communications with access systems and other communication devices. Data processing, storage and other related control devices may be provided on appropriate circuit boards and / or in chipsets. This feature is represented by reference numeral 204. The user can control the operation of the mobile device with the aid of a suitable user interface (such as a keyboard 205, voice commands, a touch-sensitive screen or a tablet or a combination thereof). A display 208, a speaker and a microphone may also be provided. In addition, the mobile communication device may include appropriate connectors (wired or wireless) to other devices and / or for connecting external accessories (e.g., hands-free devices).

[0071] The mobile device 200 may receive signals over the air or radio interface 207 via suitable means for receiving, and may transmit signals via suitable means for transmitting radio signals. Figure 2 In the embodiment of the present invention, the transceiver arrangement is schematically designated by block 206. The transceiver arrangement 206 may be provided, for example, by means of a radio part and an associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

[0072] Figure 3 An example embodiment of a control device for a communication system is shown, for example, coupled to and / or used to control a station of an access system, such as a RAN node, such as a base station, eNB or gNB, a relay node or a core network node, such as an MME or S-GW or P-GW or a core network function, such as an AMF / SMF, or a server or a host. The method can be implanted in a single control device or across more than one control device. The control device can be integrated with a node or module of a core network or RAN or external to it. In some embodiments, the base station includes a separate control device unit or module. In other embodiments, the control device can be another network element, such as a radio network controller or a spectrum controller. In some embodiments, each base station can have such a control device, such as a CU control plane (CU-CP) and a control device provided in a radio network controller. The control device 300 can be arranged to provide control of communications in a service area of ​​the system. The control device 300 includes at least one memory 301, at least one data processing unit 302, 303 and an input / output interface 304. Via the interface, the control device can be coupled to a receiver and a transmitter of the base station. The receiver and / or the transmitter may be implemented as a radio front end or a remote radio head.

[0073] In response to the growing demand for mobile services and the proliferation of new services, 5G NR supports a wide range of services with demanding KPIs. To meet its performance targets, 5G NR can rely on technologies including MU-MIMO.

[0074] MIMO technology can deliver the expected increase in spectral efficiency and improve reliability. MU-MIMO enables spatial multiplexing of a large number of devices while enhancing the reliability and performance of the radio link. In addition, MIMO can be used for high carrier frequencies (FR2, FR3), where the beamformed air interface guarantees coverage.

[0075] MIMO BS uses transmit precoding and receive combining to achieve spatial multiplexing of many UE terminals with increased spectral efficiency and reliability. However, this gain is conditional on the availability of accurate channel state information that can be obtained from uplink or downlink reference signals (CSI-RS, SRS). A MIMO signal can be considered to have multiple layers (one layer for each antenna), or a rank indicator (RI).

[0076] The performance of MIMO comes from its ability to focus radiated energy on a specific target. However, this capability is only possible when accurate and timely CSI estimates are obtained at the BS side. The accuracy of beamforming, which is the cornerstone of multi-antenna processing, depends on the accuracy of the CSI estimates obtained. Obtaining accurate CSI estimates from the UE can be challenging due to the required signaling and processing overhead.

[0077] In Release 15 NR MIMO, two types of CSI feedback are specified, namely Type I and Type II. In order to achieve enhanced CSI resolution, i.e., to obtain CSI estimates with finer granularity, Type II CSI feedback is specified in Rel 15 NR. Type II CSI feedback can be provided with high accuracy using linear combinations of oversampled 2D DFT beams. However, this improved accuracy can come at the expense of large feedback overhead. The UE is expected to feed back the index of the selected beam and the associated wideband and subband coefficients. The resulting overhead has prompted the development of several methods to reduce Type II overhead.

[0078] Several Type II CSI feedback compression schemes have been proposed, including DFT subset-based FD compression. FD compression can reduce feedback overhead by exploiting the correlation of channels across subbands. In RAN1#95, DFT-based FD compression was approved as a supported mechanism for Type II overhead reduction for rank 1 and 2.

[0079] 3GPP retains the most promising of the Type II overhead reduction methods, namely FD Type II CSI compression, for MU CSI enhancement in Release 16. Based on the DFT basis, FD compression can achieve a good trade-off between performance and overhead for ranks 1 to 2. Enhancements to Type II CSI feedback for Rel. 16 are agreed upon in 3GPP. Since support for RI>2 provides flexibility and performance improvements, extensions to Type II CSI for higher ranks are agreed upon by 3GPP.

[0080] In the agreed framework for Type II CSI FD compression for Rel.16 NR, feedback overhead reduction is achieved by applying an FD compression scheme to Rel.15 Type II PMI parameters.

[0081] The precoder W for each layer and across frequency domain units is derived as follows

[0082]

[0083] where the size of W is ((2N1 N2)×N3). The rows and columns of W correspond to the spatial and frequency domains of the reporting subbands, respectively. W1 is defined as Rel.15 type II and corresponds to the spatial domain basis (L beams per polarization).

[0084] represents the matrix of linear combination coefficients including amplitude and phase. Finally, W f W represents the FDDFT basis subset used for compression. f The size of is N3×M, where M represents the number of selected FD components. Therefore, the overhead payload for FD compression type IICSI includes the necessary bits to convey the selected SD beam β for all layers and for each layer. SD The index of K1 non-zero linear combination coefficients The number and index of the selected FD components β FD The index of the strongest coefficient and the magnitude β a and in-phase β p The non-zero coefficients are indexed by Figure 4 The bitmap of each layer depicted is indicated.

[0085] Therefore, the total payload when the compressed Type II CSI is processed independently by layer can be given by:

[0086]

[0087] The resulting increase in overhead as a function of channel rank is prohibitive. Therefore, it is critical to avoid substantial increases in CSI overhead for ranks above 1. For example, the total overhead for rank 4 may be twice that of rank 2, which may be impractical.

[0088] To support ranks 3 and 4, appropriate adaptation of DFT-based FD compression is necessary. Current FD compression methods that maintain ranks higher than or equal to 2 can result in problematic overhead proportional to the rank indicator. Without additional optimization, a simple extension will result in an unacceptable 3 to 4 times increase in overhead beyond rank 1 (relative to the linear increase in overhead with rank). That is, the current FD compression framework needs to be extended to high-rank channels.

[0089] However, extending Type II CSI to higher ranks may not be straightforward. Since the FD compression framework requires feedback of the index of the selected beam, the index of the selected FD basis subset, the set of non-zero linear combination coefficients, and their index in the bitmap, it may not be practical to simply extend Type II CSI to ranks higher than 2 without additional optimization. In fact, the overhead for rank 4 may be twice that of rank 2.

[0090] Towards reduction of CSI overhead for RI=3-4, an agreement was reached in RAN1#96 to consider several alternatives for SD and FD basis selection. In order to maintain an acceptable overhead increment for high rank channels, an agreement was reached to select downward from RI-common or RI-specific SD parameters L and layer-common or layer / layer group-specific FD parameters p and their combinations for RI∈{3,4}.

[0091] Furthermore, several alternatives for defining the maximum number of non-zero coefficients for RI∈{3,4} are currently under study.The final design of the UCI and the bitmap indicating the locations of non-zero coefficients will be the next step to complete the design for MU CSI enhancement.

[0092] In order to fully exploit the potential of MIMO, two aspects need to be addressed.

[0093] First, the feedback overhead should be reduced. Reducing the feedback overhead can achieve an increase in feedback resolution in the spatial domain and support expansion to ranks greater than 2, which is the second aspect to be addressed. Reducing the CSI reporting overhead is important because the saved resources can be used to improve spatial resolution, which ultimately leads to higher spectral efficiency.

[0094] In the ongoing 3GPP meeting, two alternatives for FD basis subset selection are proposed, namely independent and common.

[0095] However, due to the DFT-based properties, the FD components to be selected for FD compression in each layer are likely to be correlated. This correlation can be exploited to reduce the number of bits required to feed back the selected FD components in addition to the indices of the non-zero coefficients in the bitmap.

[0096] Figure 5 A flow chart of a method according to an example embodiment is shown.

[0097] In a first step S1 , the method comprises receiving a multiple-input multiple-output signal from a network.

[0098] In a second step S2, the method comprises determining a frequency domain basis subset for each layer of the multiple-input multiple-output signal.

[0099] In a third step S3, the method comprises determining the number M of frequency domain components common to each layer from the frequency domain basis subset C .

[0100] In a fourth step S4, the method comprises determining the number of layer-specific frequency domain components from the frequency domain basis subset.

[0101] In a fifth step S5, the method comprises providing an indication of the frequency domain components common to each layer and the layer specific frequency domain components to the network.

[0102] The method may be executed at a UE.

[0103] The indication may be provided in uplink control information (UCI). The signal may be a channel state information reference signal (CSI-RS). The signal may be received from the gNB.

[0104] The method is based on the agreed-upon type II FD compression, and the same set of parameters defining the compressed CSI overhead will be reused. This parameter set includes the number of selected FD components per layer M, the total number of non-zero coefficients K0, the length of the DFT basis vectors N3, and the DFT basis oversampling factor O3. In addition to the definition of the PMI FD compression unit, we also preserve the resolution of the amplitude and phase quantization.

[0105] In addition to the above parameters, the following parameters are defined:

[0106] M c = Number of common frequency domain components

[0107] M l = Number of layer-specific frequency domain components

[0108] L l = Number of spatial domain beams

[0109] K 1，c =The number of non-zero coefficients that are commonly mapped.

[0110] K 1，l =The number of non-zero coefficients mapped independently by layer.

[0111] K0 = maximum total number of non-zero quantized coefficients across layers fed back to the gNB.

[0112] K1 = the actual total number of non-zero quantized coefficients across layers fed back to the gNB.

[0113] DFT-based FD compression of the linear combination coefficient matrix W2 was agreed upon in the 3GPP meeting (RAN1#95). Using an oversampled DFT matrix, the PMI payload overhead can be reduced by exploiting FD correlation. In this approach, the same principle is retained and applies to the case of RI>2.

[0114] When extending FD PMI compression to higher ranks, there are two main alternatives to choose from, either common or layer-specific FD basis subset selection. Selecting one of these options amounts to addressing the trade-off between overhead and flexibility.

[0115] In this approach, although the FD basis subset selection can be independent, the signaling is hybrid.

[0116] The frequency domain basis subsets for each layer may be determined independently, commonly, or in a partially common manner. That is, the UE selects the FD basis subset for each layer independently, commonly, or in a partially common manner according to a specified method. The UE then derives a parameter M that specifies the size of the common portion of the bitmap. c .

[0117] For common FD basis subset selection, UE sets M c =M and the basis is signaled jointly for all layers.

[0118] For layer / layer-specific group (or independent) FD basis subset selection, the UE derives the common basis subset M c In this case, M x is the number of FD components selected by all layers. These components will constitute Represents the common basis subset.

[0119] For partial common selection, the UE selects M jointly for all layers. c FD components and select MM independently by layer / layer group c FD components. For some common choices, M c is defined to maximize the magnitude of non-zero (NZ) coefficients with overlapping positions. That is, the UE may determine M c The maximum number of NZ coefficients is concentrated in the first M c FD components, where concentrated means that the FD vector has the highest number of non-zero coefficients in the initially determined frequency domain basis subset M.

[0120] M c It may be determined for a predetermined number of layers, such as the first two layers of the layers of the MIMO signal or any other combination of layers in the layers of the MIMO signal.

[0121] The layer-specific FD components form a matrix with different RI The size of the layer-specific FD basis subsets can be cross-layer as in the considered alternatives But different.

[0122] Then, the FD basis subset for each layer will be the result of combining the common and layer-specific parts. More precisely, the FD basis for each layer is given by

[0123] Make the size

[0124] Distinguishing between layer-specific and common FD basis subsets for different layers may provide several advantages.For high-rank channels, the overhead payload for FD component selection feedback may be reduced.

[0125] This approach can support common indexes in a common FD base subset.

[0126] The method may include: determining non-zero coefficients that are commonly mapped to each layer; determining non-zero coefficients that are independently mapped per layer; and providing an indication of the non-zero coefficients to a network.

[0127] After selecting the common and layer-specific FD components, the UE will have a FD compression basis for each layer, Based on the latter, UE calculates the linear combination coefficient matrix

[0128] As mentioned above, the strongest coefficients of each layer can be associated with a common FD component (DFT tends to concentrate energy in the low-pass component) or independent of it. 1，c In practice, the non-zero coefficients associated with a common FD basis subset will be mapped jointly across layers in the bitmap mapping. The result will be K to be used by all layers 1，c Note that the values ​​of the coefficients mapped commonly are unrelated (each layer may be associated with a different value for each common index). Figure 6 An example of the approach taken is shown in .

[0129] UE construction size is M c The common FD basis of contains the FD components selected by all layers. (For the common basis subset, select M c = M and for independent basis subset selection and partially common basis subset selection M c <M).

[0130] When independent FD basis subset selection is supported, the UE constructs a layer-specific FD basis for each layer l=1...RI such that

[0131] UE calculation size is 2L×M c The common part of the bitmap K 1，c To locate the position of the common part of the bitmap, the UE may consider joint determination across all layers, or calculate the bitmap based on one layer (the first layer) or any combination of layers and apply it on other layers.

[0132] For each layer l=1...RI, the UE calculates K 1，c The indices of the layer-specific non-zero coefficients. 1，l , l = 1... The value of RI is chosen such that:

[0133]

[0134] Depending on the indexing method used, the cost of non-zero coefficient subset selection is as follows

[0135]

[0136] The cost of the baseline approach using independent indexes for each layer is given by

[0137]

[0138]

[0139] Therefore, when a bitmap index is used and The proposed method for indicating the position of NZC leads to ZLM c Overhead gain of (RI-1).

[0140] Considering (M c , L, RI) with typical values ​​of (3, 4, 4), the proposed scheme provides 72 bits of overhead gain in NZC subset selection.

[0141] Since this method distinguishes between common and layer parts in FD basis subset and NZC subset selection, part 2 of the two-part UCI will be modified to reflect this distinction and reduce subsequent overhead. The UCI will contain the following information.

[0142] UCI Section 1:

[0143] The number of non-zero coefficients K1

[0144] oThe number of common FD components M c .

[0145] UCI Part 2:

[0146] ο Oversampling rotation factor (q1, q2, q3).

[0147] o Layer-common, layer-specific or partially common spatial beams.

[0148] οM across layers c Common FD components: Bits

[0149] οM l Layer-specific FD components bits.

[0150] ο Public NZC subset selection: 2LM c bits.

[0151] ο Layer-specific NZC subset selection: 2LM l bits,

[0152] ο Layer-specific strongest coefficient.

[0153] οQuantize amplitudes per layer.

[0154] ο Quantize the phase per layer.

[0155] A more detailed description of the procedures on the UE and gNB side is as follows Figure 7 , Figure 8 and Fig. 9 As shown, all possible alternatives for FD component selection, namely, common FD component selection across layers, layer / layer group specific FD component selection and the proposed partially common FD component selection, respectively.

[0156] The proposed method can achieve accurate CSI with reduced overhead increment for high rank (RI>2). The approach can be applied with different or similar number of SD beams per layer, which can be layer common, layer specific or partially common for all layers. The proposed approach can be applied with bitmap or combined index.

[0157] The method can be applied with any FD-based subset selection method.

[0158] The method can provide a CSI feedback process that extends the Type II CSI framework to higher channel ranks (RI>2). Based on Type II CSI feedback FD compression, a flexible scheme is proposed to reduce feedback overhead, where RI>2. When RI≥2, common and layer-specific parts of UCI are defined to reduce feedback overhead. This approach can exploit any correlation across layers in terms of FD components and non-zero coefficient index selection.

[0159] Leveraging DFT properties and the possibility of rank-deficient channels, a flexible framework is proposed that can reduce feedback overhead while maintaining accuracy. FD component selection can reduce the overhead required to signal the selected FD basis subset. The UCI bitmap design can be used with any FD component selection alternative, which results in reduced overhead for signaling the positions of non-zero coefficients.

[0160] By distinguishing the common and layer-specific parts of the UCI, any redundant information can be removed from the feedback.

[0161] The proposed method mainly modifies two parts of UCI, namely the feedback and non-zero coefficient selection related to the FD basis subset, respectively. Regardless of whether the approach adopted for the FD basis subset selection is common, partially common, or cross-layer independent, the method adopts a hybrid signaling approach by distinguishing between the common and layer-specific parts. In fact, a part of the non-zero coefficients is mapped jointly, which can significantly reduce the overhead generated. In addition, any commonly selected FD component is signaled once in a specific part, which also reduces the overhead contribution of the FD basis subset selection.

[0162] The method can be found in the reference Figure 3 The control device described is implemented in the embodiment of the present invention.

[0163] The apparatus may include: a component for the following operations: receiving a multiple-input multiple-output signal from a network; determining a frequency domain basis subset for each layer of the multiple-input multiple-output signal; determining the number M of frequency domain components common to each layer from the frequency domain basis subset C ; determining the number of layer-specific frequency domain components from the frequency domain basis subset; and providing an indication to the network of the frequency domain components common to each layer and the layer-specific frequency domain components.

[0164] It should be understood that the apparatus may include or be coupled to other units or modules, etc., such as a radio part or radio head used in transmission and / or reception. Although the apparatus has been described as one entity, the different modules and memories may be implemented in one or more physical or logical entities.

[0165] Note that while embodiments have been described with respect to 5G NR, similar principles may be applied with respect to other networks and communication systems. Thus, while certain embodiments are described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, the embodiments may be applied to any other suitable form of communication system in addition to the communication system shown and described herein.

[0166] It is also noted herein that while the above describes exemplary embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

[0167] In general, the various example embodiments may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software, which may be executed by a controller, microprocessor, or other computing device, although the invention is not limited thereto. Although aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other graphical representation, it is well understood that the blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general purpose hardware or controllers, or other computing devices, or some combination thereof, as non-limiting examples.

[0168] Example embodiments of the present invention may be implemented by computer software executable by a data processor of a mobile device (such as in a processor entity), or by hardware, or by a combination of software and hardware. Computer software or programs (also referred to as program products) include software routines, applets and / or macros that can be stored in any device-readable data storage medium, and they include program instructions for performing specific tasks. A computer program product may include one or more computer executable components that are configured to perform various embodiments when the program is running. One or more computer executable components may be at least one software code or part thereof.

[0169] Furthermore, it should be noted at this point that any box of the logic flow in the figure may represent program steps, or interconnected logic circuits, boxes and functions, or a combination of program steps and logic circuits, boxes and functions. The software may be stored on a physical medium such as a memory chip or a memory block implemented within a processor, a magnetic medium such as a hard disk or a floppy disk, and an optical medium such as, for example, a DVD and its data variant CD. Physical media are non-transient media.

[0170] The memory may be of any type suitable for the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. As non-limiting examples, the data processor may be of any type suitable for the local technical environment and may include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), an FPGA, a gate-level circuit, and a processor based on a multi-core processor architecture.

[0171] Exemplary embodiments of the present invention may be practiced in various components such as integrated circuit modules. The design of integrated circuits is generally a highly automated process. Complex and powerful software tools are available to convert a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[0172] The foregoing description provides a complete informative description of exemplary embodiments of the present invention by way of non-limiting examples. However, when read in conjunction with the accompanying drawings and the appended claims, various modifications and adaptations may become apparent to those skilled in the relevant art in view of the foregoing description. However, all of these and similar modifications taught by the present invention will still fall within the scope of the present invention as defined by the appended claims. In fact, there are other embodiments comprising a combination of one or more embodiments with any of the other embodiments previously discussed.

Claims

1. An apparatus for communication, comprising: receiving a multiple-input multiple-output signal from a network; determining a frequency domain basis subset for each layer of the multiple-input multiple-output signal; Determine the number of frequency domain components M common to each layer from the frequency domain basis subset C ; determining a number of layer-specific frequency-domain components from the frequency-domain basis subset; as well as providing to the network an indication of the frequency domain components common to each layer and the frequency domain components specific to the layer, The device further comprises components for: Determining the frequency domain basis subset for each layer independently, commonly or in a partially common manner; In the case where the frequency domain basis subset is determined for each layer in a common manner, the number M of the frequency domain components is set C is equal to the number M of selected frequency domain basis components; In case the frequency domain basis subset is determined for each layer in an independent manner, the number M of the frequency domain components is set C is equal to the number of frequency domain basis components selected by all layers; as well as In the case where the frequency domain basis subset is determined for each layer in a partially common manner, the number M of the frequency domain components C is defined to maximize the magnitude of non-zero coefficients with overlapping positions.

2. The apparatus of claim 1, comprising means for providing the indication in uplink control information.

3. The device according to any one of claims 1 to 2, wherein M C It is determined based on a predetermined number of layers. The apparatus according to claim 3 , wherein the predetermined number of layers is the first two of the layers or any combination of the layers.

5. The device according to any one of claims 1 to 2, comprising means for: determining non-zero coefficients that are commonly mapped to each layer; and An indication of the non-zero coefficients is provided to the network.

6. The device according to any one of claims 1 to 2, comprising means for: determining non-zero coefficients that are independently mapped per layer; and An indication of the non-zero coefficients is provided to the network.

7. The apparatus of claim 5, comprising means for providing the indication of the non-zero coefficients in uplink control information.

8. The apparatus according to any one of claims 1 to 2, wherein the signal is a channel state information reference signal.

9. A method of communication, comprising: receiving a multiple-input multiple-output signal from a network; determining a frequency domain basis subset for each layer of the multiple-input multiple-output signal; Determine the number of frequency domain components M common to each layer from the frequency domain basis subset C ; determining a number of layer-specific frequency-domain components from the frequency-domain basis subset; as well as providing to the network an indication of the frequency domain components common to each layer and the frequency domain components specific to the layer, The method further comprises: Determining the frequency domain basis subset for each layer independently, commonly or in a partially common manner; In the case where the frequency domain basis subset is determined for each layer in a common manner, the number M of the frequency domain components is set C is equal to the number M of selected frequency domain basis components; In case the frequency domain basis subset is determined for each layer in an independent manner, the number M of the frequency domain components is set C is equal to the number of frequency domain basis components selected by all layers; and In the case where the frequency domain basis subset is determined for each layer in a partially common manner, the number M of the frequency domain components C is defined to maximize the magnitude of non-zero coefficients with overlapping positions.

10. An apparatus for communication, comprising: at least one processor and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to at least: receiving a multiple-input multiple-output signal from a network; determining a frequency domain basis subset for each layer of the multiple-input multiple-output signal; Determine the number of frequency domain components M common to each layer from the frequency domain basis subset C ; determining a number of layer-specific frequency-domain components from the frequency-domain basis subset; as well as providing to the network an indication of the frequency domain components common to each layer and the frequency domain components specific to the layer, The device is further configured to: Determining the frequency domain basis subset for each layer independently, commonly or in a partially common manner; In the case where the frequency domain basis subset is determined for each layer in a common manner, the number M of the frequency domain components is set C is equal to the number M of selected frequency domain basis components; In case the frequency domain basis subset is determined for each layer in an independent manner, the number M of the frequency domain components is set C is equal to the number of frequency domain basis components selected by all layers; as well as In the case where the frequency domain basis subset is determined for each layer in a partially common manner, the number M of the frequency domain components C is defined to maximize the magnitude of non-zero coefficients with overlapping positions.

11. A computer-readable medium comprising program instructions, wherein the program instructions are used to cause an apparatus to perform at least the following operations: receiving a multiple-input multiple-output signal from a network; determining a frequency domain basis subset for each layer of the multiple-input multiple-output signal; Determine the number of frequency domain components M common to each layer from the frequency domain basis subset C ; determining a number of layer-specific frequency-domain components from the frequency-domain basis subset; as well as providing to the network an indication of the frequency domain components common to each layer and the frequency domain components specific to the layer, The program instructions are also used to cause the device to perform at least the following operations: Determining the frequency domain basis subset for each layer independently, commonly or in a partially common manner; In the case where the frequency domain basis subset is determined for each layer in a common manner, the number M of the frequency domain components is set C is equal to the number M of selected frequency domain basis components; In case the frequency domain basis subset is determined for each layer in an independent manner, the number M of the frequency domain components is set C is equal to the number of frequency domain basis components selected by all layers; as well as In the case where the frequency domain basis subset is determined for each layer in a partially common manner, the number M of the frequency domain components C is defined to maximize the magnitude of non-zero coefficients with overlapping positions.

Images