Channel state information overhead reduction for multiple transmission reception points / panels and cell-less MIMO

Abstract

A technique for performing CSI reporting includes identifying clusters of TRPs that share common information in their CSI and transmitting a full CSI report to a selected TRP of the cluster while transmitting partial CSI reports to the other TRPs of the cluster. Along these lines, in an example implementation, a UE receives a CSI‑RS from a network, the CSI‑RS carrying multiple reference symbols from multiple TRPs. Based on the multiple symbols, the UE generates TRP data representing CSI feedback for each TRP. From the CSI feedback, the UE identifies a subset of TRPs that share common information within the CSI feedback as a cluster. The UE then sends first identification data to the network that identifies the subset of TRPs that constitute the cluster.

Description

Technical Field

[0001] This description relates to communications. Background Art

[0002] A communication system may be a facility that enables communication between two or more nodes or devices, such as fixed or mobile communication devices. Signals may be carried on wired or wireless carriers.

[0003] An example of a cellular communication system is the architecture standardized by the Third Generation Partnership Project (3GPP). The latest development in this area is generally referred to as the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio access technology. E-UTRA (Evolved UMTS Terrestrial Radio Access) is the air interface of 3GPP's LTE upgrade path for mobile networks. In LTE, a base station or access point (AP), called an enhanced node AP (eNB), provides wireless access within a coverage area or cell. In LTE, a mobile device or mobile station is called a user equipment (UE). LTE includes many improvements or developments.

[0004] For example, the global bandwidth shortage faced by wireless operators has prompted consideration of underutilized millimeter wave (mmWave) spectrum for future broadband cellular communication networks. For example, mmWave (or very high frequency) may include a frequency range between 30 and 300 gigahertz (GHz). For example, radio waves in this band may have wavelengths from ten to one millimeter, hence the name millimeter band or mmWave. The amount of wireless data is likely to increase significantly in the coming years. Various technologies have been used to try to address this challenge, including obtaining more spectrum, having smaller cell sizes, and using improved technologies that achieve more bits / second / hertz. One element that can be used to obtain more spectrum is to move to higher frequencies, such as above 6 GHz. For fifth-generation wireless systems (5G), an access architecture for deploying cellular radio equipment that uses mmWave radio spectrum has been proposed. Other example spectrums, such as cmWave radio spectrum (e.g., 3 to 30 GHz), may also be used. Summary of the Invention

[0005] According to an example implementation, a method includes: receiving, by a control circuit system of a user equipment (UE), transmit and receive point (TRP) data representing corresponding channel state information (CSI) feedback for a plurality of TRPs connected to a network; performing an identification operation on the TRP data to identify a TRP subset of the plurality of TRPs, each TRP in the identified TRP subset having a common portion within its corresponding CSI feedback; and transmitting identification data representing the identified TRP subset to the network.

[0006] According to an example implementation, an apparatus includes at least one processor and at least one memory, the at least one memory including computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least: receive transmit and receive point (TRP) data, the TRP data representing corresponding channel state information (CSI) feedback for a plurality of TRPs connected to a network; perform an identification operation on the TRP data to identify a TRP subset of the plurality of TRPs, each TRP in the identified TRP subset having a common portion within its corresponding CSI feedback; and transmit identification data representing the identified TRP subset to the network.

[0007] According to an example implementation, an apparatus includes components for receiving, by a control circuit system of a user equipment (UE), transmit and receive point (TRP) data representing corresponding channel state information (CSI) feedback for a plurality of TRPs connected to a network; components for performing an identification operation on the TRP data to identify a TRP subset of the plurality of TRPs, each TRP in the identified TRP subset having a common portion within its corresponding CSI feedback; and components for transmitting identification data representing the identified TRP subset to the network.

[0008] According to an example implementation, a computer program product includes a computer-readable storage medium and stores executable code, which, when executed by at least one data processing device, is configured to cause the at least one data processing device to receive transmission and reception point (TRP) data, the TRP data representing corresponding channel state information (CSI) feedback for multiple TRPs connected to a network; perform an identification operation on the TRP data to identify a TRP subset of the multiple TRPs, each TRP in the identified TRP subset having a common portion within its corresponding CSI feedback; and transmit identification data representing the identified TRP subset to the network.

[0009] According to an example implementation, a method includes: receiving, by a control circuit system of a network processor and from a user equipment (UE), first identification data representing a TRP set of multiple transmission reception points (TRPs); determining a quality of a backhaul connection between the TRP sets; and adjusting the first identification data based on the determined quality of the backhaul connection between the TRP sets to generate second identification data.

[0010] According to an example implementation, an apparatus includes at least one processor and at least one memory, the at least one memory including computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause the apparatus to at least: receive first identification data representing a TRP set of a plurality of transmission reception points (TRPs); determine a quality of a backhaul connection between the TRP sets; and adjust the first identification data based on the determined quality of the backhaul connection between the TRP sets to generate second identification data.

[0011] According to an example implementation, an apparatus includes a component for receiving, by a control circuit system of a network processor and from a user equipment (UE), first identification data representing a TRP set of multiple transmission reception points (TRPs); a component for determining a quality of a backhaul connection between the TRP sets; and a component for adjusting the first identification data based on the determined quality of the backhaul connection between the TRP sets to generate second identification data.

[0012] According to an example implementation, a computer program product includes a computer-readable storage medium and stores executable code, which, when executed by at least one data processing device, is configured to cause the at least one data processing device to: receive first identification data, the first identification data representing a TRP set of multiple transmission reception points (TRPs); determine the quality of a backhaul connection between the TRP sets; and adjust the first identification data based on the determined quality of the backhaul connection between the TRP sets to generate second identification data.

[0013] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a block diagram of a digital communication network according to an example implementation.

[0015] Figure 2 is a diagram illustrating a TRP cluster according to an example implementation.

[0016] Figure 3 is a flow chart illustrating a process of determining a TRP in a cluster according to an example implementation.

[0017] Figure 4 is a flow chart illustrating a process of adjusting the TRP in a cluster based on the quality of the backhaul connection according to an example implementation.

[0018] Figure 5 is a block diagram of a node or wireless station (e.g., a base station / access point, a relay node, or a mobile station / user equipment) according to an example implementation. DETAILED DESCRIPTION

[0019] Figure 1 is a block diagram of a digital communication system, such as wireless network 130, according to an example implementation. Figure 1 In a wireless network 130, user devices 131, 132, 133, and 135 (also referred to as mobile stations (MSs) or user equipment (UEs)) can connect to (and communicate with) a base station (BS) 134, which can also be referred to as an access point (AP), an enhanced Node B (eNB), a gNB (which can be a 5G base station), or a network node. At least some of the functionality of an access point (AP), base station (BS), or (e)Node B (eNB) can also be performed by any node, server, or host operatively coupled to a transceiver (such as a remote radio head). BS (or AP) 134 provides wireless coverage within cell 136, including to user devices 131, 132, and 133. Although only three user devices are shown connected or attached to BS 134, any number of user devices can be provided. BS 134 is also connected to core network 150 via interface 151. This is just one simple example of a wireless network, and others can be used.

[0020] User equipment (UE) may refer to a portable computing device, including wireless mobile communication devices operating with or without a subscriber identity module (SIM), including but not limited to the following device types: mobile station (MS), mobile phone, cell phone, smartphone, personal digital assistant (PDA), mobile phone, device using a wireless modem (such as alarm or measurement equipment), laptop and / or touch screen computer, tablet, phablet, game console, notebook computer and multimedia device. It should be understood that a user equipment may also be almost exclusively an uplink-only device, an example of which is a camera or video camera that uploads images or video clips to a network.

[0021] In LTE (as an example), the core network 150 may be referred to as an evolved packet core (EPC), which may include a mobility management entity (MME) that may handle or assist in mobility / handover of user equipment between BSs, one or more gateways that may forward data and control signals between the BSs and a packet data network or the Internet, and other control functions or blocks.

[0022] The various example implementations may be applied to a wide variety of wireless technologies, wireless networks, such as LTE, LTE-A, 5G (New Radio or NR), cmWave and / or mmWave band networks, or any other wireless network or use case. LTE, 5G, cmWave, and mmWave band networks are provided as illustrative examples only, and the various example implementations may be applied to any wireless technology / wireless network. The various example implementations may also be applied to a variety of different applications, services, or use cases, such as, for example, ultra-reliable low-latency communications (URLLC), Internet of Things (IoT), enhanced mobile broadband, massive machine-type communications (MMTC), vehicle-to-vehicle (V2V), vehicle-to-device, etc. Each of these use cases or UE types may have its own set of requirements.

[0023] Some aspects of 5G New Radio (NR) are based on a beamformed air interface. Being able to beamform radio signals is crucial because it focuses the radiated energy on its intended target and improves the receiver's sensitivity to the desired signal. Beamforming capabilities can be achieved by increasing the number of antennas at both the base station (gNB) and the user equipment (UE). In 5G NR, gNBs may be able to use more antenna elements than in 4G. However, such capabilities depend on the need to obtain accurate estimates of channel state information (CSI).

[0024] One use case for multiple Transmit Receiver Point (TRP) transmission is joint transmission, which involves transmitting data from multiple TRPs to a given UE simultaneously. This can be performed in a coherent or non-coherent manner. In the ongoing Rel-16 3GPP multi-TRP discussion, non-coherent joint transmission (NC-JT) with multiple PDCCHs (Physical Downlink Control Channels) and single PDCCH designs is being considered.

[0025] Joint transmission requires the availability of accurate CSI at the TRP to exploit the beamforming-based air interface of 5G NR and, moreover, to achieve gains in throughput or any other major network key performance indicators (KPIs).

[0026] However, at least for the single PDCCH design in Rel-16, TRPs are required to exchange received channel state information. Similar requirements may be required in other design options anticipated in the Rel-17 discussion. However, due to backhaul speed limitations and varying propagation delays, timing errors cannot be completely eliminated. Furthermore, obtaining accurate CSI estimates for cooperative TRPs and feeding them back in a timely manner may prove to be a challenging task, especially when feedback capabilities are limited.

[0027] Therefore, a specific CSI estimation scheme for multiple TRPs is needed.

[0028] A CSI report may include one or more of the following:

[0029] Rank Indicator (RI), which is the appropriate number of transmission layers for downlink (DL) transmission;

[0030] A precoder matrix indicator (PMI), which indicates to the device what to estimate as the appropriate precoder matrix based on the selected rank; and

[0031] • A channel quality indicator (CQI), which tells the device what it estimates to be the appropriate channel coding rate and modulation scheme based on the selected precoder matrix.

[0032] In Rel.15 3GPP, the precoder matrix W is written as W = W1W2, where W1 is a beam grid matrix of size 2N1N2 × 2L, consisting of L orthogonal vectors / beams for each polarity r from an oversampled O1O2N1N2 DFT beam set, where N1 and N2 are the number of antenna ports in the horizontal and vertical domains. O1 and O2 are the oversampling factors in both dimensions; and W2 is a matrix of size 2L × N3, where N3 is the number of PMI frequency subbands. W2 carries the linear combination coefficients used to phase the long-term spatial beams for each subband.

[0033] In Rel.16 3GPP, W2 is compressed by N3×M frequency domain (FD) matrix W f Further compression is performed, where M is the number of FD components. The precoder matrix W for each layer and across frequency domain units is in is a 2L×M matrix of linear combination coefficients, and H denotes Hermitian, ie, conjugate transpose.

[0034] For time-domain explicit CSI feedback, the channel frequency response Via the projection matrix Compression is performed. N is the number of receiving antennas, N a is the number of active subcarriers, and N s is the length of the common channel support, i.e., the locations of the active taps in all transmit-receive beams. The columns of are plotted according to their positions on the common channel support on the DFT basis. It can be regarded as the FD basis subset matrix W in Rel.16 3GPP f 's counterpart.

[0035] The long-term CSI components for Rel.15 3GPP CSI feedback and time-domain explicit feedback are as follows:

[0036] Spatial domain: Grid-of-beam (GoB) matrix W1,

[0037] Frequency / time: FD basis subset W f / Projection Matrix

[0038] In a traditional multi-TRP scenario, a UE can be connected to multiple TRPs simultaneously. Each has its own complexity range, from a small panel with 4 antenna ports to a macro base station with 64 antenna ports. Accurate CSI feedback requires a non-negligible payload in the uplink control signaling, especially for the Type II CSI codebook.

[0039] This causes an uplink signaling bottleneck that is exacerbated in multiple TRPs. In fact, in this case, the uplink CSI feedback overhead increases significantly not only based on the number of TRPs but also with the number of UE connections.

[0040] This issue prompted the study of FD compression type II CSI in Rel-16 3GPP to reduce CSI reporting overhead. However, this does not completely solve the uplink CSI overhead problem, especially for multi-TRP scenarios.

[0041] In contrast to the conventional multi-TRP scenario described above, an improved technique for performing CSI reporting includes identifying clusters of TRPs that share common information in their CSI, and transmitting a full CSI report to a selected TRP of the cluster, while transmitting a partial CSI report to the other TRPs of the cluster. Along these lines, in an example implementation, a UE receives a CSI-RS from a network, and the CSI-RS carries multiple reference symbols from multiple TRPs. Based on the multiple symbols, the UE generates TRP data representing CSI feedback for each TRP. From the CSI feedback, the UE identifies a subset of TRPs that share common information within the CSI feedback as a cluster. The UE then sends first identification data to the network that identifies the subset of TRPs that constitute the cluster. In some implementations, the network identifies the TRP cluster and the UE then selects a subset of the cluster based on the generated TRP data. In some implementations, the network, after receiving the first identification data, generates second identification data identifying some TRPs of the cluster based on the quality of the backhaul connection between the TRPs.

[0042] Advantageously, transmitting complete CSI feedback to only one TRP of the cluster and a smaller amount of information to the other TRPs of the cluster reduces the uplink CSI overhead. For example, when the beam grid matrix W1 is included in the CSI feedback and the common information includes some columns of the matrix, the UE can send the CSI feedback corresponding to the primary TRP to the primary TRP and only send the columns of the beam grid matrix that are not common to the TRPs of the cluster to each other secondary TRP. In this way, the information that is common to the TRPs of the cluster - in this case, the columns of the beam grid matrix W1 that are common to the TRPs of the cluster can be transmitted from the primary TRP to the secondary TRP cluster via the backhaul connection.

[0043] Figure 2 is a diagram illustrating a cluster of TRPs 200 according to an example implementation. Figure 2 In the illustrated implementation, there are two clusters 210 and 220, with three TRPs in each cluster. The TRPs in cluster 210 are connected via backhaul connections 212(1) and 212(2), and the TRPs in cluster 220 are connected via backhaul connections 222(1) and 222(2). UE 230 determines clusters 210 and 220 based on common information in the CSI feedback for each TRP. CSI clusters 210 and 220 and the TRPs in UE 230 are connected to network 240.

[0044] The improved technique exploits correlations in long-term CSI, i.e., in the channel spatial structure and / or support for closely spaced TRPs / panels. In practice, in high / medium density deployment scenarios, when the distance between a group of TRPs / panels and the UE 230 is greater than the distance between the TRPs / panels themselves, the radio channel between the latter group of TRPs / panels and the UE will be characterized by correlated spatial subspaces and temporal support in the time domain.

[0045] UE 230 is able to detect commonalities in long term CSI between several TRPs based on CSI-RS measurements and therefore group them into two clusters, alternatively clustering can also be performed based on SSB measurements. The TRP grouping is based on the measurements of UE 230, i.e. UE specific clustering, and therefore, it is specific to the UE. For example, different UEs at different locations may not see the same CSI commonalities between TRPs 1, 2 and 3. It is also important to note that UE 230 can be connected to more than one cluster (e.g. clusters 210 and 220) at the same time, i.e. it is not assumed that all TRPs to which the UE is connected have commonalities in long term CSI. In this IR, the TRPs within a cluster in which the TRPs show commonalities in the long term CSI for one UE are called CSI clusters.

[0046] The UE 230 may always be connected to one or more TRPs within each CSI cluster 210 and 220. From the perspective of the UE 230, there may be a primary TRP or reference TRP determined by CSI feedback for a TRP within a CSI cluster 210 or 220. Therefore, there may be two types of TRPs across the entire TRP set: a primary TRP (reference TRP) and a secondary TRP. The following methods for transmitting CSI feedback may be used:

[0047] Perform full UL CSI feedback between the UE and the primary TRP (reference TRP) within the CSI cluster,

[0048] • Partial UL CSI feedback is performed between the UE and any TRP within the cluster.

[0049] The long-term CSI between the UE and the primary TRP (reference TRP, e.g., TRP-1) is then shared within CSI cluster 210 so that the secondary TRPs (e.g., TRP-2 and TRP-3) can infer some information about the long-term CSI between the UE and the secondary TRPs. UE 230 may still have to provide a reduced amount of long-term CSI feedback characterizing the links to the secondary TRPs. Note that sending CSI information to the primary TRP is an implementation option; UE 230 may also send CSI feedback characterizing the primary and secondary links to one or more TRPs.

[0050] The improved technique is applicable to both FD and TD CSI feedback. Depending on the backhaul status (ideal / non-ideal), the improved technique involves feedback with reduced overhead FD / TD independent / joint CSI estimation. When indicating the CSI-RS configuration, for example, the UE 230 can indicate the backhaul quality of each TRP. The UE 230 can use the backhaul quality of each TRP in the grouping criteria, and in some implementations only allow TRPs with the same backhaul quality in the same cluster / group.

[0051] The goal of the improved techniques proposed herein is to reduce the CSI feedback overhead for both TD and FD CSI feedback in high / medium density deployment scenarios for multiple TRPs / panels and cell-free massive MIMO. As described above, TRPs within a CSI cluster (e.g., CSI cluster 210) share commonality in long-term CSI with respect to UE 230. Therefore, the UE should contribute to the cluster's decision making. However, from the network's perspective, the TRPs within a CSI cluster 210 share reliable backhaul quality (ideal or near-ideal backhaul), making the exchange of long-term CSI within the CSI cluster 210 feasible.

[0052] To achieve this goal, there are several options for grouping TRPs into CSI clusters:

[0053] The network 240 notifies the UE 230 in advance of the TRPs belonging to one network cluster 210 (i.e., TRPs with ideal backhaul). The UE 230 then groups only the TRPs with ideal backhaul connections into a CSI cluster. For example, the UE 230 will indicate the backhaul quality during the time when the CSI-RS configuration is provided. Thus, each CSI-RS resource corresponding to a TRP will indicate the backhaul quality of the TRP from which the CSI-RS originated. In some implementations, a specific TRP index, while potentially helpful, is not required in this indication.

[0054] • UE 230 informs network 240 of its selection of CSI cluster 210 (e.g., in uplink control signaling). Network 240 then responds with a modified selection of CSI cluster such that all TRPs within one CSI cluster have ideal backhaul (e.g., DCI).

[0055] The network indication of the TRP cluster can be implicit or explicit. In some implementations, CSI feedback for multiple TRPs is scheduled by a TRP within the network cluster (a primary or reference TRP from the perspective of the UE 230), and the UE 230 implicitly indicates the network cluster is the TRP CSI calculation (and the requested feedback). In some implementations, the higher layer configuration for CSI resources can be associated with the TRP-ID or some other indication to distinguish the TRPs. In this case, the UE 230 can determine the CSI cluster based on simultaneous CSI reporting requests. In some implementations, the network 240 indicates the TRP associated with each CSI cluster 210, 220 in a separate indication.

[0056] In some implementations, the primary TRP is a reference TRP that UE 230 uses to determine and simplify CSI feedback for other TRPs. In some implementations, the primary TRP is the TRP that schedules or receives PUCCH or PUSCH transmissions. In some implementations, the selection of the primary TRP is indicated by the network 240 (e.g., based on CQI feedback).

[0057] In some implementations, the fact is exploited that when a UE is connected to another TRP y that belongs to the same CSI cluster as TRP x, some spatial beams within the beam grid matrix W1 (selected from the oversampled DFT codebook) chosen by the UE connected to one TRP x will also be chosen. Therefore, after a complete CSI update for one TRP x, the beam grid matrix W1 of another TRP y can be partially or completely taken from the selection of the beam grid matrix W1 of TRP x.

[0058] In some implementations, the following procedure is followed to reduce CSI feedback overhead:

[0059] 1. Within a CSI cluster, such as CSI cluster 210, complete UL CSI feedback is sent by UE 230 to the primary TRPTRP-1.

[0060] 2. CSI feedback from W1 to the main TRP is provided by W 1，1 express.

[0061] 3. For every other auxiliary TRP x, the beam grid matrix is ​​constructed as W 1，x =[W 1，xc W 1，xs ], where W 1，xc represents the portion that is common to the beam grid feeding the main TRP and can therefore be inferred from it, while W 1，xs W represents the part specific to auxiliary TRPx. 1，xc The size is 2N1N2×L c , and W 1，xs The size is 2N1N2×L s .

[0062] 4. UE 230 only needs to feed back information about a specific part to TRP xW 1，xs This can reduce the overhead

[0063] 5. In some implementations, TRP x may use only the public part W 1，xc , and no UE feedback is required; this can reduce the overhead and reducing signaling delays.

[0064] In some implementations, exploitation is made of the fact that the selection of spatial beams within the beam grid matrix W1 (selected from the oversampled DFT codebook) chosen by the UE connected to TRP y can use a "shifted" version of the selection of spatial beams within the beam grid matrix W1 of TRP x.

[0065] In some implementations, the following procedure is followed to reduce CSI feedback overhead:

[0066] 1. Within a CSI cluster, such as CSI cluster 210, complete UL CSI feedback is sent by UE 230 to the primary TRP TRP-1.

[0067] 2. CSI feedback from W1 to the main TRP is provided by W 1，1 express.

[0068] 3. Every other TRP x uses W with different horizontal and / or vertical rotation factors O1 and O2 1，1 This can cause or or The cost is reduced.

[0069] In some implementations, the fact that there is a correlation in the selection of the GoB matrix between the primary TRP and each secondary TRP is exploited. Therefore, assuming that the UE and the secondary TRPs know the selection of the GoB for the primary TRP, when the UE reports the GoB for the secondary TRP, instead of picking L beams from the N1N2 possible orthogonal beams, a simplified set of N1′N2′<N1N2 possible orthogonal beams is constructed based on the selection of the primary TRP beam. For example, if the combination index is used to signal the GoB matrix Then the overhead saved for feedback to the secondary TRP will be:- For example, the reduced set of orthogonal beams can be centered around the strongest beam of the primary TRP, whose index is typically fed back to the gNB.

[0070] In some implementations, the fact is exploited that the FD basis subset matrix W chosen by a UE connected to a TRP x is tf(y) when the UE is connected to another TRP y belonging to the same CSI cluster as TRP x. f Some FD components within (selected from the oversampled DFT codebook) will also be picked. Therefore, after a complete CSI update for one TRP x, the FD basis subset matrix W of another TRPy f The FD basis subset matrix W can be partially or completely taken from TRP x f choice.

[0071] In some implementations, the following procedure is followed to reduce CSI feedback overhead:

[0072] 1. Within a CSI cluster, such as CSI cluster 210, complete UL CSI feedback is sent by UE 230 to the primary TRPTRP-1.

[0073] 2. Include W f The CSI feedback to the main TRP is provided by W f，1 express.

[0074] 3. For every TRP x, the FD basis subset matrix for each layer is constructed as W f，x =[W f，xc W f，xs ], where W f，xc represents the part that is common to the FD basis subset matrix fed to the main TRP and can therefore be inferred from it, while W f，xs Indicates the part specific to TRP x. f，xs The size is N3×M c , and W f，xs The size is N3×M s .

[0075] 4.UE only needs to feed back information about the specific part to TRP x W f，xs This can reduce the overhead

[0076] 5. In some implementations, TRP x may use only the public part W f，xc No UE feedback is required. This can reduce the overhead and reducing signaling delays.

[0077] In some implementations, the fact is exploited that the FD basis subset matrix W chosen by the UE connected to TRP y is f The selection of FD components within (selected from the oversampled DFT codebook) can be done using the FD basis subset matrix W of TRP x. f A "shifted" version of the selection within the FD component.

[0078] In some implementations, the following procedure is followed to reduce CSI feedback overhead:

[0079] 1. Within a CSI cluster, such as CSI cluster 210, complete UL CSI feedback is sent by UE 230 to the primary TRP TRP-1.

[0080] 2. Include W f The CSI feedback to the main TRP is provided by W f，1 express.

[0081] 3. For every other TRP x, use W with different rotation factor O3 f1 Please note that currently in Rel.16, the oversampling factor is not fed back to the gNB. Therefore, this scheme can cause The cost is reduced.

[0082] In some implementations, the fact that in time domain explicit CSI, the channel support vectors of UEs connected to two TRPs belonging to the same CSI cluster will have some common elements are exploited. Therefore, after a complete CSI update for one TRP x, the channel support vectors of the other TRP ys y The channel support vectors can be partially or completely taken from TRP xs x In some implementations, the reduced set of orthogonal beams is centered around the strongest beam of the primary TRP, whose index is typically fed back to the gNB.

[0083] In some implementations, the following procedure is followed to reduce CSI feedback overhead:

[0084] 1. Within a CSI cluster, such as CSI cluster 210, complete UL CSI feedback is sent by UE 230 to the primary TRPTRP-1.

[0085] 2. The CSI feedback including s to the primary TRP is represented by s1.

[0086] 3. For every TRP x, the channel support vector is constructed as s x =[s c s xs ], where s c represents the part that is common to the channel support vectors fed to the main TRP and can therefore be inferred from it, while s xs Indicates the part specific to TRP x. c The size is 1×N s，c , and s xs The size is 1×N s，s .

[0087] 4. UE 230 only needs to feed back information about the specific part to TRP xs c . This reduces the overhead to:

[0088] 5. In some implementations, TRP x may use only the public part N s，c , and no UE feedback is required; this can reduce the overhead and reducing signaling delays.

[0089] In some implementations, the fact that in time domain explicit CSI, the channel support vectors of UEs connected to two TRPs belonging to the same CSI cluster will have some correlation is exploited. Therefore, each tap can be y The position within the channel support vector of (i) is reported as TRP xs x The corresponding taps in (i) are shifted versions. This reduces the reported channel support vector s y Required expenses.

[0090] In some implementations, the following procedure is followed to reduce CSI feedback overhead:

[0091] 1. Within a CSI cluster, such as CSI cluster 210, complete UL CSI feedback is sent by UE 230 to the primary TRPTRP-1.

[0092] 2. The CSI feedback including s to the primary TRP is represented by s1.

[0093] 3. For every TRP x, the channel support vector s xEach lth element in is reported as different from the corresponding lth element in the channel support vector s1.

[0094] 4. Therefore, not from f OS ×L range possible tap positions, but rather from D < < f OS ×L range The lth tap is selected from a set of possible taps.

[0095] 5. Then, the UL overhead is reduced to

[0096] Example 1: Figure 3 3 is a flow chart illustrating an example method 300 for performing the improved technique. Operation 310 includes receiving, by control circuitry of a user equipment (UE), transmission and reception point (TRP) data representing corresponding channel state information (CSI) feedback for a plurality of TRPs connected to a network. Operation 320 includes performing an identification operation on the TRP data to identify a subset of TRPs of the plurality of TRPs, each TRP in the identified subset of TRPs having a common portion within its corresponding CSI feedback. Operation 330 includes transmitting identification data representing the identified subset of TRPs to the network.

[0097] Example 2: An example implementation according to Example 1, wherein receiving TRP data includes: receiving a reference signal, the reference signal including multiple reference symbols from each TRP in a plurality of TRPs; and generating CSI feedback based on the multiple reference symbols.

[0098] Example 3: An example implementation according to any one of Examples 1 or 2, wherein the identification data is first identification data, the reference signal is a CSI reference signal (CSI-RS), and wherein the method further includes: receiving second identification data representing a modified TRP subset from the network, the second identification data being based on the quality of the backhaul connection between the TRP subsets.

[0099] Example 4: An example implementation according to any one of Examples 1 to 3, wherein the identification data includes a primary TRP identifier, which identifies the primary TRP of the identified TRP subset, the other TRPs in the TRP subset are secondary TRPs, and the method further includes: (i) transmitting complete CSI feedback for the primary TRP to the TRP of the TRP subset, and (ii) transmitting a portion of the corresponding CSI feedback that is not common to the TRP subset to each of the other TRPs in the TRP subset.

[0100] Example 5: An example implementation according to Example 4, wherein the primary TRP is a TRP configured to receive PUCCH and / or PUSCH transmissions.

[0101] Example 6: An example implementation according to Example 4 or 5, wherein the TRP to which the complete CSI feedback for the primary TRP is sent is the primary TRP.

[0102] Example 7: An example implementation according to any one of Examples 1 to 6, wherein the CSI feedback for multiple TRPs is frequency domain CSI feedback, including corresponding beam grid (GoB) matrix W1, corresponding linear combination coefficient matrix And the corresponding frequency domain compression matrix W f .

[0103] Example 8: An example implementation according to Example 7, wherein the common portion of the CSI feedback for the TRP subsets includes at least one column of the GoB matrix W1 of the master TRP for the TRP subsets.

[0104] Example 9: An example implementation according to any one of Examples 7 to 8, wherein the GoB matrix W1 for the first TRP of the TRP subset includes a shifted version of the GoB matrix W1 for the second TRP of the TRP subset, and the method further includes: transmitting complete CSI feedback for the main TRP to the main TRP, and the CSI feedback for other TRPs in the TRP subset is derived from the CSI feedback for the main TRP.

[0105] Example 10: An example implementation according to any one of Examples 7 to 9, wherein the common portion of the CSI feedback for the TRP subset includes data representing a reduced set of orthogonal beams selected from an oversampled beam grid.

[0106] Example 11: An example implementation of any of Examples 7 to 10, wherein the common portion of the CSI feedback for the TRP subsets comprises a frequency domain compression matrix W for a master TRP of the TRP subsets f At least one column.

[0107] Example 12: An example implementation according to any one of Examples 7 to 11, wherein the frequency domain compression matrix W for the first TRP of the TRP subset is f The frequency domain compression matrix W of the second TRP for the TRP subset is included f A shifted version of the CSI feedback for the primary TRP is transmitted to the primary TRP, and the method further includes: transmitting complete CSI feedback for the primary TRP to the primary TRP, and CSI feedback for other TRPs in the TRP subset is derived from the CSI feedback for the primary TRP.

[0108] Example 13: An example implementation of any of Examples 7 to 12, wherein the portion of the CSI feedback that is not common to the subset of TRPs comprises a linear combination coefficient matrix elements.

[0109] Example 14: An example implementation according to any one of Examples 1 to 13, wherein the CSI feedback for multiple TRPs is time-domain explicit CSI feedback including a channel support vector s.

[0110] Example 15: An example implementation according to Example 14, wherein the common portion of the CSI feedback for the TRP subset includes at least one element of the channel support vector s.

[0111] Example 16: An example implementation according to any one of Examples 14 to 15, wherein the channel support vector s for the first TRP of the TRP subset includes a shifted version of the channel support vector s for the second TRP of the TRP subset, and the method further includes: transmitting complete CSI feedback for the main TRP to the main TRP, and the CSI feedback for other TRPs in the TRP subset is derived from the CSI feedback for the main TRP.

[0112] Example 17: An apparatus comprising means for performing the method of any of Examples 1 to 16.

[0113] Example 18: A computer program product comprising a non-transitory computer-readable storage medium and storing executable code which, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform the method of any one of claims 1 to 16.

[0114] Figure 4 4 is a flow chart illustrating an example method 400 for performing the improved technique. Operation 410 includes receiving, by control circuitry of a network processor and from a user equipment (UE), first identification data representing a set of transmission reception points (TRPs) of a plurality of TRPs. Operation 420 includes determining the quality of a backhaul connection between the TRP sets. Operation 430 includes adjusting the first identification data based on the determined quality of the backhaul connection between the TRP sets to generate second identification data.

[0115] Example 2: According to the example implementation of Example 1, it also includes: transmitting second identification data to the UE.

[0116] Example 3: An example implementation according to any of Examples 1 or 2, wherein determining the quality of the backhaul connection between the TRP sets includes: performing a count of the number of ideal backhaul connections between the TRP sets.

[0117] Example 4: The example implementation according to any one of Examples 1 to 3 further includes: before receiving the first identification data, identifying the plurality of TRPs as a TRP cluster.

[0118] Further example implementations and / or example details will now be provided.

[0119] Example abbreviation list:

[0120] 3GPP Third Generation Partnership Project

[0121] BWP Bandwidth Part

[0122] CSI Channel State Information

[0123] DFT Discrete Fourier Transform

[0124] DL Downlink

[0125] FDD Frequency Division Duplex

[0126] FD frequency domain

[0127] gNB Next Generation NodeB

[0128] LC linear combination

[0129] LTE Long Term Evolution

[0130] MIMO Multiple Input Multiple Output

[0131] MR Maximum Rank

[0132] NR New Radio

[0133] PMI Precoding Matrix Indicator

[0134] PRB Physical Resource Block

[0135] RB Resource Block

[0136] SB sub-band

[0137] SSB Synchronous Signal Block

[0138] TRP Transmission Reception Point

[0139] UL Uplink

[0140] WB Broadband

[0141] WI Work Items

[0142] WID Work Item Description

[0143] Figure 5is a block diagram of a wireless station (e.g., an AP, BS, eNB, UE, or user equipment) 500 according to an example implementation. The wireless station 500 may include, for example, one or two RF (radio frequency) or wireless transceivers 502A, 502B, each of which includes a transmitter for transmitting signals and a receiver for receiving signals. The wireless station also includes a processor or control unit / entity (controller) 504 to execute instructions or software and control the transmission and reception of signals, and a memory 506 to store data and / or instructions.

[0144] The processor 504 may also make decisions or determinations, generate frames, packets, or messages for transmission, decode received frames or messages for further processing, and other tasks or functions described herein. For example, the processor 504, which may be a baseband processor, may generate messages, packets, frames, or other signals for transmission via the wireless transceiver 502 (502A or 502B). The processor 504 may control the transmission of signals or messages over a wireless network, and may control the reception of signals or messages, etc., over a wireless network (e.g., after being down-converted by, for example, the wireless transceiver 502). The processor 504 may be programmable and capable of executing software or other instructions stored in a memory or other computer medium to perform the various tasks and functions described above, such as one or more of the tasks or methods described above. The processor 504 may be (or may include), for example, hardware, programmable logic, a programmable processor executing software or firmware, and / or any combination thereof. For example, using other terminology, the processor 504 and transceiver 502 may be considered together as a wireless transmitter / receiver system.

[0145] In addition, reference Figure 5 , the controller (or processor) 508 can execute software and instructions and can provide overall control for the station 500 and can Figure 5 Other systems not shown provide controls, such as controlling input / output devices (e.g., display, keypad), and / or may execute software for one or more applications that may be provided on wireless station 500, such as, for example, an email program, audio / video applications, a word processor, a voice over IP application, or other applications or software.

[0146] Additionally, a storage medium may be provided that includes stored instructions that, when executed by a controller or processor, may cause the processor 504 or other controller or processor to perform one or more of the functions or tasks described above.

[0147] According to another example implementation, the RF or wireless transceiver 502A / 502B may receive signals or data and / or transmit or send signals or data. The processor 504 (and possibly the transceiver 502A / 502B) may control the RF or wireless transceiver 502A or 502B to receive, send, broadcast or transmit signals or data.

[0148] However, the embodiments are not limited to the systems given as examples, but those skilled in the art may apply the solutions to other communication systems. Another example of a suitable communication system is the 5G concept. It is assumed that the network architecture in 5G will be very similar to LTE Advanced. 5G is likely to 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 cooperation with smaller base stations and may also employ various radio technologies to achieve better coverage and higher data rates.

[0149] It should be understood that future networks will likely utilize network function virtualization (NFV), 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. Virtualized network functions (VNFs) may include one or more virtual machines that use standard or general-purpose servers rather than customized hardware to run computer program code. Cloud computing or data storage may also be utilized. In radio communications, this may mean that node operations may be performed at least partially in a server, host, or node that is operatively coupled to a remote radio head. Node operations may also be distributed across multiple servers, nodes, or hosts. It should also be understood that the distribution of labor between core network operations and base station operations may be different from LTE or even non-existent.

[0150] Implementations of the various techniques described herein may be implemented in digital electronic circuit systems, or in computer hardware, firmware, software, or a combination thereof. Implementations may be implemented as computer program products, i.e., computer programs tangibly embodied in information carriers, such as in machine-readable storage devices or in propagated signals, for execution or control of operations by data processing apparatus (e.g., programmable processors, computers, or multiple computers). Implementations may also be provided on computer-readable media or computer-readable storage media that may be non-transitory media. Implementations of the various techniques may also include implementations provided via transient signals or media, and / or programs and / or software implementations that may be downloaded via the Internet or (multiple) other networks (wired networks and / or wireless networks). In addition, implementations may be provided via machine type communications (MTC) and the Internet of Things (IoT).

[0151] A computer program may be in source code form, object code form, or some intermediate form, and may be stored on some carrier, distribution medium, or computer-readable medium, which may be any entity or device capable of carrying the program. Examples of such carriers include recording media, computer memory, read-only memory, optical and / or electrical carrier signals, telecommunications signals, and software distribution packages. Depending on the required processing power, a computer program may be executed on a single electronic digital computer or distributed across multiple computers.

[0152] Furthermore, implementations of the various techniques described herein may use cyber-physical systems (CPS) (systems where collaborative computing elements control physical entities). CPS can implement and utilize a large number of interconnected ICT devices (sensors, actuators, processors microcontrollers, ...) embedded in physical objects at different locations. Mobile cyber-physical systems (where the physical system in question has inherent mobility) are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robots and electronic devices transported by humans or animals. The popularity of smartphones has increased interest in the field of mobile cyber-physical systems. Therefore, various implementations of the techniques described herein may be provided via one or more of these technologies.

[0153] Computer programs (such as the computer program(s) described above) may be written in any form of programming language, including compiled or interpreted languages, and may be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment, or as a portion thereof. A computer program may be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

[0154] The method steps may be performed by one or more programmable processors executing a computer program or portion of a computer program to perform functions by operating on input data and generating output. The method steps may also be performed by, and apparatus may be implemented as, special purpose logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit).

[0155] Processors suitable for the execution of computer programs include, for example, general-purpose and special-purpose microprocessors, and any one or more processors of any kind of digital computer, chip, or chipset. Typically, the processor will receive instructions and data from a read-only memory or a random access memory, or both. Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer may also include, or be operatively coupled to, receive data from or transfer data to, or both, one or more mass storage devices (e.g., magnetic, magneto-optical, or optical disks) for storing data. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including, for example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD ROM and DVD-ROM disks. The processor and memory may be supplemented by, or incorporated in, special-purpose logic circuitry.

[0156] To provide for interaction with a user, an implementation may be implemented on a computer having a display device (e.g., a cathode ray tube (CRT) or liquid crystal display (LCD) monitor) for displaying information to the user and a user interface (e.g., a keyboard and a pointing device, such as a mouse or trackball, through which the user can provide input to the computer). Other types of devices may also be used to provide for interaction with a user; for example, feedback provided to the user may be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; and input from the user may be received in any form, including sound, voice, or tactile input.

[0157] The implementation may be implemented in a computer system that includes a back-end component (e.g., as a data server) or includes a middleware component (e.g., an application server) or includes a front-end component (e.g., a client computer with a graphical user interface or a web browser through which a user can interact with the implementation), or any combination of such back-end, middleware, or front-end components. The components may be interconnected by any form or medium of digital data communication, such as a communication network. Examples of communication networks include local area networks (LANs) and wide area networks (WANs), such as the Internet.

[0158] While certain features of the described implementations have been illustrated as described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It should, therefore, be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the various embodiments.

Claims

1. A method of communication, comprising: generating, by a user equipment (UE), transmission and reception point (TRP) data representing corresponding channel state information (CSI) feedback for a plurality of TRPs connected to a network; performing an identification operation on the TRP data to identify a TRP subset of the plurality of TRPs, each TRP in the identified TRP subset having a common portion within its corresponding CSI feedback; as well as transmitting identification data representing the identified subset of TRPs to the network, The CSI feedback for the multiple TRPs is frequency domain CSI feedback, and the frequency domain CSI feedback includes the corresponding frequency domain compression matrix W f , The frequency domain compression matrix W for the first TRP of the TRP subset is f The frequency domain compression matrix W comprising the second TRP for the TRP subset f A shifted version of And wherein the method further comprises: transmitting complete CSI feedback for the main TRP to a main TRP, and the CSI feedback for other TRPs in the TRP subset is derived from the CSI feedback for the main TRP.

2. The method of claim 1 , wherein generating the TRP data comprises: receiving a reference signal comprising a plurality of reference symbols from each of the plurality of TRPs; as well as The CSI feedback is generated based on the plurality of reference symbols, and wherein the reference signal is a CSI reference signal (CSI-RS).

3. The method according to claim 2, wherein the identification data is first identification data, And wherein the method further comprises: Second identification data representing a modified subset of TRPs is received from the network, the second identification data being based on a quality of a backhaul connection between the subset of TRPs.

4. The method of claim 1 , wherein the identification data comprises a primary TRP identifier that identifies the primary TRP, and the other TRPs in the TRP subset are secondary TRPs, And wherein the method further comprises: Transmitting a portion of the corresponding CSI feedback that is not common to the TRP subset to each of the other TRPs in the TRP subset.

5. The method of claim 1, wherein the primary TRP is a TRP configured to receive PUCCH and / or PUSCH transmissions.

6. The method of claim 1 , wherein the common portion of the CSI feedback for the TRP subset comprises the frequency domain compression matrix W for the master TRP of the TRP subset. f At least one column.

7. The method according to claim 1, wherein the frequency domain CSI feedback further includes a corresponding beam grid (GoB) matrix W1 and a corresponding linear combination coefficient matrix 8. The method of claim 7, wherein the common portion of the CSI feedback for the TRP subset comprises at least one column of the GoB matrix W1 for the primary TRP.

9. The method of claim 7, wherein the GoB matrix W1 for a first TRP of the TRP subset comprises a shifted version of the GoB matrix W1 for a second TRP of the TRP subset.

10. The method of claim 7, wherein the common portion of the CSI feedback for the subset of TRPs comprises data representing a reduced set of orthogonal beams selected from an oversampled beam grid.

11. The method of claim 7, wherein the portion of the CSI feedback that is not common to the subset of the TRPs comprises the linear combination coefficient matrix elements.

12. The method of claim 1, wherein the CSI feedback for the multiple TRPs is time-domain explicit CSI feedback including a channel support vector s.

13. The method of claim 12, wherein the common portion of the CSI feedback for the TRP subset comprises at least one element of the channel support vector s.

14. The method of claim 12, wherein the channel support vector s for a first TRP of the TRP subset comprises a shifted version of the channel support vector s for a second TRP of the TRP subset.

15. An apparatus for communication, comprising: at least one processor; as well as at least one memory including computer program code; The at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least: generating transmission and reception point (TRP) data representing corresponding channel state information (CSI) feedback for a plurality of TRPs connected to the network; performing an identification operation on the TRP data to identify a TRP subset of the plurality of TRPs, each TRP in the identified TRP subset having a common portion within its corresponding CSI feedback; as well as transmitting identification data representing the identified subset of TRPs to the network, The CSI feedback for the multiple TRPs is frequency domain CSI feedback, and the frequency domain CSI feedback includes the corresponding frequency domain compression matrix W f , The frequency domain compression matrix W for the first TRP of the TRP subset is f The frequency domain compression matrix W comprising the second TRP for the TRP subset f A shifted version of and wherein the at least one memory and the computer program code are further configured to, with the at least one processor, further cause the apparatus to at least: The complete CSI feedback for the primary TRP is transmitted to the primary TRP, and the CSI feedback for other TRPs in the TRP subset is derived from the CSI feedback for the primary TRP.

16. The apparatus of claim 15, wherein the at least one memory and the computer program code configured to generate the TRP data with the at least one processor further cause the apparatus to at least: receiving a reference signal comprising a plurality of reference symbols from each of the plurality of TRPs; and The CSI feedback is generated based on the plurality of reference symbols, and wherein the reference signal is a CSI reference signal (CSI-RS).

17. The apparatus according to claim 15, wherein the identification data is first identification data, and wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to at least: Second identification data representing a modified subset of TRPs is received from the network, the second identification data being based on an indicated quality of a backhaul connection between the subset of TRPs.

18. The apparatus of claim 15, wherein the identification data comprises a primary TRP identifier that identifies the primary TRP, the other TRPs in the TRP subset being secondary TRPs, and wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus to: Transmitting a portion of the corresponding CSI feedback that is not common to the TRP subset to each of the other TRPs in the TRP subset.

19. The apparatus of claim 15, wherein the primary TRP is a TRP configured to receive PUCCH and / or PUSCH transmissions.

20. The apparatus of claim 15, wherein the common portion of the CSI feedback for the TRP subset comprises the frequency domain compression matrix W for the master TRP of the TRP subset. f At least one column.

21. The apparatus according to claim 15, wherein the frequency domain CSI feedback further comprises a corresponding grid of beams (GoB) matrix W1 and a corresponding linear combination coefficient matrix 22. The apparatus of claim 21, wherein the common portion of the CSI feedback for the TRP subset comprises at least one column of the GoB matrix W1 for the primary TRP.

23. The apparatus of claim 21, wherein the GoB matrix W1 for a first TRP of the TRP subset comprises a shifted version of the GoB matrix W1 for a second TRP of the TRP subset.

24. The apparatus of claim 21, wherein the common portion of the CSI feedback for the subset of TRPs comprises data representing a reduced set of orthogonal beams selected from an oversampled beam grid.

25. The apparatus of claim 21 , wherein the portion of the CSI feedback that is not common to the subset of the TRPs comprises the linear combination coefficient matrix elements.

26. The apparatus of claim 21, wherein the CSI feedback for the plurality of TRPs is time-domain explicit CSI feedback including a channel support vector s.

27. The apparatus of claim 26, wherein the common portion of the CSI feedback for the TRP subset comprises at least one element of the channel support vector s.

28. The apparatus of claim 26, wherein the channel support vector s for a first TRP of the TRP subset comprises a shifted version of the channel support vector for a second TRP of the TRP subset.

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