Transmission of channel state information reference signals for different subband sizes

Abstract

Example embodiments generally relate to transmitting channel state information reference signals (CSI-RS) for different subband sizes. In example embodiments, a terminal device can receive, from a network device, information regarding a CSI-RS resource mapping. The information regarding the CSI-RS resource mapping includes first information indicating one or more resource elements in a resource block allocated for one or more CSI-RS ports and second information indicating one or more additional resource elements in the resource block allocated for the one or more CSI-RS ports. The second information is configured for an edge subband. Based on the information regarding the CSI-RS resource mapping, the terminal device can further receive, from the network device, the CSI-RS.

Description

Technical Field

[0001] The exemplary embodiments described in this application generally relate to communication technologies; and, more specifically, to wireless communication devices and methods for reducing overhead during the transmission of Channel State Information Reference Signals (CSI-RS). Background Technology

[0002] Some abbreviations appearing in this specification and / or accompanying drawings are defined as follows:

[0003] 3GPP Third Generation Partnership Project

[0004] AoA Angle of Arrival

[0005] AoD (Angle of Exit)

[0006] CSI Channel State Information

[0007] CSI-RS Channel State Information Reference Signal

[0008] DFT (Discrete Fourier Transform)

[0009] FD frequency domain

[0010] FDD (Frequency Division Duplex)

[0011] gNB Next Generation Base Station

[0012] MIMO (Multiple Input Multiple Output)

[0013] NR New Radio

[0014] PRB (Physical Resource Block)

[0015] PS Port Selection

[0016] RE Resource Elements

[0017] RRC (Radio Resource Control)

[0018] SD space domain

[0019] TDD (Time Division Duplex)

[0020] UE User Equipment

[0021] Multi-user massive MIMO is a fundamental feature of 5G NR, offering advantages such as high spectrum availability, high energy efficiency, and wide coverage. In massive MIMO systems, the base station (BS) needs accurate Channel State Information (CSI) to properly execute MIMO operations. For this purpose, 3GPP introduced the Type-II codebook, designed to report both wideband and subband CSI for accurate MIMO operation. Summary of the Invention

[0022] The following provides a brief overview of exemplary embodiments to offer a basic understanding of some aspects of the various embodiments. It should be noted that this overview is not intended to identify key features of the basic elements or define the scope of the embodiments; its sole purpose is to introduce some concepts in a simple form as a prelude to the more detailed description provided below.

[0023] In a first aspect, an example embodiment of a network device is provided. The network device may include: at least one processor; and at least one memory including computer program code. The at least one memory and the computer program code are configured to utilize the at least one processor to cause the network device to: transmit information about a Channel State Information Reference Signal (CSI-RS) resource mapping to a terminal device. The information about the CSI-RS resource mapping may include: first information indicating the allocation of one or more resource elements in a resource block for one or more CSI-RS ports; and second information indicating the allocation of one or more additional resource elements in a resource block for one or more CSI-RS ports. The second information is configured for edge subbands. The network device further precodes the CSI-RS using one or more frequency domain (FD) components; and transmits the CSI-RS to the terminal device based on the information about the CSI-RS resource mapping.

[0024] In a second aspect, an example embodiment of a terminal device is provided. The terminal device includes: at least one processor; and at least one memory including computer program code. The at least one memory and the computer program code are configured to utilize the at least one processor to cause the terminal device to: receive information about Channel State Information Reference Signal (CSI-RS) resource mapping from a network device. The CSI-RS resource mapping information may include: first information indicating the allocation of one or more resource elements for one or more CSI-RS port indication resource blocks; and second information indicating the allocation of one or more additional resource elements in the resource blocks for the one or more CSI-RS ports. The second information is configured for edge subbands. Based on the information about the CSI-RS resource mapping, the terminal device further receives CSI-RS from the network device.

[0025] Example embodiments of methods, apparatus, and computer programs for transmitting and receiving CSI-RS are also provided. Such embodiments generally correspond to the example embodiments of the networks and terminal devices described above; and, for ease of description, will not be repeated here.

[0026] When read in conjunction with the accompanying drawings, the drawings illustrate the principles of exemplary embodiments of this application; other features and advantages of exemplary embodiments of this application will also be apparent from the following description of specific embodiments. Attached Figure Description

[0027] Now, by way of non-limiting example, some exemplary embodiments will be described with reference to the accompanying drawings.

[0028] Figure 1 A schematic diagram of an example communication system that can implement embodiments of this application is shown;

[0029] Figure 2 A schematic diagram is shown, including subband bandwidths with subbands of the same size;

[0030] Figure 3 A schematic diagram showing subband bandwidths including subbands of different sizes is shown;

[0031] Figure 4 An operational interaction diagram for transmitting a Channel State Information Reference Signal (CSI-RS) according to an example embodiment of this application is shown;

[0032] Figure 5 A schematic diagram of a physical resource block including resource elements allocated to CSI-RS ports is shown according to an example embodiment of this application;

[0033] Figure 6A , 6B 6C illustrates an example of a bit string configuration for mapping FD components to physical resource blocks according to an exemplary embodiment of this application;

[0034] Figure 7 A flowchart of a method for transmitting CSI-RS according to an example embodiment of this application is shown;

[0035] Figure 8 A flowchart of a method for receiving CSI-RS according to an example embodiment of this application is shown;

[0036] Figure 9 A block diagram of an example communication system that can implement embodiments of this application is shown.

[0037] Throughout all the accompanying drawings, the same or similar reference numerals indicate the same or similar elements. Repeated descriptions of the same elements will be omitted. Detailed Implementation

[0038] Some exemplary embodiments are described in detail below with reference to the accompanying drawings. Specific details are included in the following description to provide a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts can be implemented without these specific details. In some cases, well-known circuits, technologies, and components are shown in block diagram form to avoid confusion with the described concepts and features.

[0039] As used in this application, the term "network device" refers to any suitable entity or device that can provide cellular or coverage access to a network or to receive services through which terminal devices can access the network. A network device may generally be referred to as a base station. The term "base station" as used in this application may refer to a Node B (or NB), an evolved Node B (or eNodeB or eNB), or a gNB. A base station can be implemented as a macro base station, a relay node, or a low-power node, such as a pico base station or a femto base station. A base station may consist of several distributed network elements, such as a central unit (CU), one or more distributed units (DU), one or more remote radio heads (RRHs) or remote radio units (RRUs). The number and functionality of these distributed elements depend on the selected discrete RAN architecture.

[0040] As used in this application, the terms "terminal device" or "user equipment" (UE) refer to any entity or device capable of wirelessly communicating with or with network devices. Examples of terminal devices may include mobile phones, mobile terminals (MT), mobile stations (MS), subscriber stations (SS), portable subscriber stations (PSS), access terminals (AT), computers, wearable devices, vehicular communication devices, machine-type communication (MTC) devices, D2D communication devices, V2X communication devices, sensors, etc. The term "terminal device" may be used interchangeably with UE, user terminal, mobile terminal, mobile station, or wireless device.

[0041] Figure 1 A schematic diagram of an example communication system 100 that can implement embodiments of this application is shown. (See reference...) Figure 1 A communication system 100, which may be part of a communication network, may include a user equipment (UE) 110 and a base station 120, shown as a gNB. The UE 110 may communicate with the gNB 120 on uplink (UL) and downlink (DL) channels. For massive MIMO systems, the gNB 120 may have a large number of antennas, and the UE 110 may also have multiple antennas, typically fewer than those of the gNB. The gNB 120 may transmit DL channels on a number of transmit antennas, which are received on a number of receive antennas at the UE 110, so that the MIMO channel has a dimension of Ta×Ra; where Ta is the number of transmit antennas and Ra is the number of receive antennas. For example, in some embodiments, the MIMO channel may be beamformed at the gNB 120 using a GoB (beam lattice) W1 precoder. In this case, the dimension of the MIMO channel can be reduced to B×Ra, where B is the number of transmit beams. Beamforming can reduce interference between signals and improve energy and spectral efficiency.

[0042] One challenge in MIMO communication is obtaining the downlink CSI at gNB 120 without unreasonable overhead. In TDD systems, reciprocity of the UL-DL channels can be assumed; and gNB 120 can obtain the downlink CSI via uplink pilot transmissions from UE 110. However, in FDD systems, because the UL and DL channels are often separated by a bandwidth exceeding the coherent frequency band, complete UL-DL channel reciprocity cannot be maintained. UE 110 needs to calculate the DL CSI via DL pilot transmissions from gNB 120 and report the calculated DL CSI to gNB 120, which significantly increases UE complexity and reporting overhead.

[0043] Some studies have shown that partial reciprocity is maintained for FDD systems. For example, for FDD DL and UL channels, the angle of departure (AoD) or angle of arrival (AoA) and the delay of multipath propagation are reciprocal. By utilizing this partial reciprocity property, the gNB 120 can use UL pilots, such as the sounding reference signal (SRS) received from the UE 110, to obtain delay-related information of the radio channel, such as the frequency domain (FD) components, which should be the same as those selected by the UE 110 via the DL pilots, such as the channel state information reference signal (CSI-RS). The gNB 120 can use one or more selected FD components to weight the beamforming CSI-RS resources that already contain spatial domain (SD) beams. Therefore, the UE 110 does not need to select FD components and report the corresponding index for Type II port selection (PS) CSI, which reduces UE complexity and reporting overhead.

[0044] In some implementations, the gNB 120 can select more than one optimal FD component to achieve better channel reconstruction quality. To transmit multiple FD components via beamforming CSI-RS, the gNB 120 needs to be configured with more CSI-RS ports. Subsequently, the consumption of DL CSI-RS resources will undesirably increase proportionally to the number of FD components. One solution to avoid excessive consumption of CSI-RS resources is to transmit more FD components on the CSI-RS port resources, which will refer to... Figure 2 Let's continue.

[0045] Figure 2 A schematic diagram showing bandwidths including subbands of the same size is shown. (Reference) Figure 2 The bandwidth can include N3 subbands with a subband size M, that is, it includes M physical resource blocks (PRBs). For example, the subband size M can be determined by parameters from a higher layer. Configure it. The size of the first sub-band can be set by... It is derived that; and the size of the last subband can be determined by... It is concluded that if Or for if in, It is the sequence number of the starting PRB within the bandwidth. It refers to the bandwidth size, that is, the number of PRBs contained within the bandwidth. Figure 2 This illustrates an example scenario where N3 subbands have the same size M=4. The PRBs contained within the N3 subbands can be divided into M PRB sets by their indices within each subband. For example, the first PRB within a subband can be grouped into a first PRB set; and the Mth PRB within a subband can be grouped into an Mth PRB set. In other words, the bandwidth comprises M PRB sets; and each of the M PRB sets contains N3 PRBs distributed across the N3 subbands. Figure 2 In this context, PRBs contained within subbands are labeled using PRB set numbers from #1 to #4.

[0046] Based on the multipath delay of the wireless channel, the gNB 120 can select the optimal M0 FD components for the CSI-RS port. For example, the gNB 120 can perform spatial (SD) and frequency (FD) transforms from UL pilot (e.g., SRS) measurements to obtain the optimal SD beam and optimal M0 FD components at the subband level. The FD component is a Discrete Fourier Transform (DFT) vector; and includes N3 precoding coefficients that will be mapped to N3 subbands on the CSI-RS resource, respectively. The M0 FD components can be transmitted on M PRB sets, examples of which are shown in Table 1 below. Referring to Table 1, for beamformed CSI-RS port 1-X, 4 (M0 = 4) FD components are transmitted on 4 (M = 4) PRB sets respectively. In Table 1, Indicates the SD beam #i associated with CSI-RS port #m m , where m∈{1,2,...,X}, and X is the number of beamforming CSI-RS ports in the spatial domain. m,n This represents the index of the FD component vector transmitted via PRB set #n on CSI-RS port #m, where n∈{1,2,…,M}, and currently n∈{1,2,3,4}. Represents the FD component vector #j m,n The k-th subband precoding coefficient (i.e., the k-th vector element) is applied to the n-th PRB of subband #k, where k∈{1,2,...,N3}. FD component vector The dimension is N3×1. For these CSI-RS ports, the groups of M0 FD components can be the same or different. In this example embodiment, the 4 FD components are transmitted on 4 PRB sets respectively; and the total number of CSI-RS ports is not scaled according to the number of FD components, thereby reducing the consumption of DL's CSI-RS resources.

[0047]

[0048] Table 1

[0049] However, in some embodiments, it depends on the sequence number of the starting PRB within the bandwidth. and bandwidth size Edge subbands of bandwidth, such as the first and / or last subband, can have different subband sizes than non-edge subbands. The size of the first subband may also be different from the size of the last subband. Figure 3 The illustration shows example bandwidths with different subband sizes. (Reference) Figure 3 The first subband contains 2 PRBs, the non-edge subband contains 4 PRBs, and the last subband contains 2 PRBs. That is, PRB sets #1 and #2 are of size N³, while PRB sets #3 and #4 are missing their first and last PRBs, and are of size (N³-2). Because the edge subband has fewer PRBs than the non-edge subband, the edge subband can transmit fewer FD components than the non-edge subband. For example, referring to Table 2 below, for CSI-RS port 1-X, two FD components... Transmission occurs within the first sub-band; four FD components. Transmission takes place within the non-edge subband; and both FD components... The transmission takes place within the last sub-band. This means the FD component. The initial precoding coefficients and FD components The loss of the final precoding coefficients will adversely affect the FD transform operation. The following example embodiments are provided to address this problem, but the application is not limited thereto.

[0050]

[0051] Table 2

[0052] Figure 4 An interactive diagram illustrating operations for transmitting a Channel State Information Reference Signal (CSI-RS) according to an example embodiment of this application is shown. These operations can be performed via... Figure 1 This is implemented using gNB 120 and UE 110 as shown.

[0053] Reference Figure 4In operation 210, gNB 120 can send CSI-RS resource mapping information to UE 110. The CSI-RS resource mapping information may include: first information indicating the allocation of one or more resource elements (REs) in the PRB for one or more CSI-RS ports. For example, the first information may include: information elements (IEs) firstOFDMSymbolInTimeDomain and firstOFDMSymbolInTimeDomain2 indicating the start symbol of the CSI-RS port in the time domain; IE frequencyDomainAllocation indicating the start subcarrier of the CSI-RS port in the frequency domain; IE freqBand indicating the bandwidth mapped to the CSI-RS port; IE cdm-Type indicating the code division multiplexing (CDM) type applied to the CSI-RS port; IE nrofPorts indicating the number of CSI-RS ports; IE density indicating the number of REs in the PRB for the CSI-RS ports, etc. Using the first information, the CSI-RS ports and the resource locations for the CSI-RS ports can be determined. Figure 5 The illustration shows a sample PRB including a RE assigned to a CSI-RS port. (Reference) Figure 5 The first piece of information contained in the information about CSI-RS resource mapping can indicate that four REs (RE set A) are assigned to these CSI-RS ports.

[0054] In addition to the first information, the information regarding CSI-RS resource mapping may also include second information indicating the allocation of one or more additional REs in one or more PRBs for one or more CSI-RS ports. It should be understood that one or more additional REs are allocated to compensate for lost PRBs within edge subbands. In other words, one or more additional REs are allocated to replicate the CSI-RS ports mapped to the one or more REs determined by the first information, rather than transferring new / additional CSI-RS ports. In some example embodiments, one or more additional REs can be determined by moving one or more REs indicated by the first information. For example, the second information may include an offset indicator in the time and / or frequency domains to indicate the offset of one or more additional REs relative to one or more configured REs. As an example, the offset indicator may include a pair of parameters, such as (t, f); where parameter t indicates the offset in the time domain, and parameter f indicates the offset in the frequency domain. The value "1" for parameters t and f represents an offset in the positive (increasing) direction, the value "-1" represents an offset in the negative (decreasing) direction, or the value "0" represents a zero offset. When both parameters t and f are "0", no additional REs are assigned. Additional REs can be copied and formed into a pattern adjacent to the REs determined by the first information. For example, refer to... Figure 5 The offset indicator (t=0, f=1) indicates that RE set B is additionally allocated to the CSI-RS port; the offset indicator (t=1, f=0) indicates that RE set C is additionally allocated; the offset indicator (t=0, f=-1) indicates RE set D; the offset indicator (t=-1, f=0) indicates RE set E; the offset indicator (t=1, f=1) indicates RE set F; the offset indicator (t=1, f=-1) indicates RE set G; the offset indicator (t=-1, f=-1) indicates RE set H; and the offset indicator (t=-1, f=1) indicates RE set I.

[0055] It should be understood that the first information can be applied to PRBs within both edge and non-edge subbands to allocate REs for CSI-RS ports, while the second information is configured to be used for at least one or two edge subbands. The second information can be applied to specific PRBs to compensate for lost PRBs within the edge subband. For example, if the first subband within the bandwidth has P fewer PRBs than the non-edge subband, the second information can be applied to the first P P PRBs within the bandwidth to compensate for the P lost P PRBs within the first subband. The first P P PRBs can belong to the first subband or to both the first and second subbands. In this case, one or more additional REs from the first P P PRBs will be configured to transmit the earliest precoding coefficients corresponding to the FD components of the P lost P PRBs within the first subband. If the last subband within the bandwidth has Q fewer PRBs than the non-edge subband, the second information can also be applied to the last Q PRBs within the bandwidth to compensate for the Q lost PRBs within the last subband. The last Q PRBs can belong to the last subband or to both the last and penultimate subbands. In this case, one or more additional REs in the last Q PRBs will be configured to transmit the final precoding coefficients corresponding to the FD components of the Q PRBs lost in the last subband.

[0056] As can be seen from the above discussion, by utilizing the second information, the edge (first and / or last) precoding coefficients of the FD component, which would otherwise be lost due to the absence of PRB in the edge subband, can be transmitted via the additional RE indicated by the second information. For example, referring to Table 2, for CSI-RS port 1-X, the FD component The first precoding coefficients can be transmitted on the additional REs in the first two PRBs of the bandwidth, while the last precoding coefficients are transmitted on the FD components. It can be transmitted on the additional RE in the last two PRBs of the bandwidth. Transmission of the complete FD component will facilitate FD conversion and channel reconstruction operations.

[0057] Return to reference Figure 4 In some example embodiments, at operation 220, gNB 120 may optionally send CSI-RS configuration information to UE 110. The CSI-RS configuration information may indicate the sequence of PRB sets that map M0 FD components to CSI-RS resources within the subband. In one example embodiment, the CSI-RS configuration information may include bit strings, etc., to indicate the sequence numbers of the FD components mapped to the PRB sets within the subband. The bit strings may include... Each bit. For example, reference Figure 6AIf the bandwidth comprises four PRB sets (i.e., non-edge subband size M = 4), and four (M0 = 4) FD components are selected at gNB 120, then the CSI-RS configuration information may include the bit string "1234" to indicate that the first FD component is mapped to the first PRB, the second FD component is mapped to the second PRB, and so on. For example, if two (M0 = 2) FD components are selected at gNB 120, then the CSI-RS configuration information may include the bit string "1212" to indicate that the first FD component is mapped to the first and third PRBs, while the second FD component is mapped to the second and fourth PRBs, such as... Figure 6B As shown; or, the bit string "1122" indicates that the first FD component is mapped to the first and second PRBs, and the second FD component is mapped to the third and fourth PRBs, as shown. Figure 6C As shown. It should be understood that when the number of FD components M0 is less than the number of PRB sets M in the bandwidth, the FD components can be mapped to more than one PRB set. The bit string provides a flexible way to map FD components to PRB sets in the bandwidth. Using this bit string, UE 110 can know which(s) of the FD components lost their first and / or last precoding coefficients due to missing PRBs in the edge subband. In some example embodiments, operation 220 can be omitted; instead, M0 FD components can be mapped to M PRB sets in a predefined sequence. The predefined sequence can be preconfigured or predefined at UE 110 and gNB 120.

[0058] When UE 110 receives information about CSI-RS resource mapping in operation 210, and optionally receives CSI-RS configuration information in operation 220, UE 110 learns of the CSI-RS resources for transmitting the complete FD component. For example, refer to Figure 3 and 6A The additional REs are allocated in the first two PRBs to transmit the earliest precoding coefficients of FD components "3" and "4"; and in the last two PRBs to transmit the final precoding coefficients of FD components "3" and "4". (See reference) Figure 3 and 6B Additional REs are allocated in the first two PRBs to transmit the earliest precoding coefficients of FD components "1" and "2"; and are allocated in the last two PRBs to transmit the final precoding coefficients of FD components "1" and "2". (See reference) Figure 3 and 6C The additional REs are allocated in the first two PRBs to transmit the first precoding coefficients of the FD component "2"; and are allocated in the last two PRBs to transmit the last precoding coefficients of the FD component "2".

[0059] exist Figure 6B and6C In the illustrated embodiment, when the number of FD components M0 is less than the number of PRB sets M, one FD component can be mapped to multiple PRB sets. In this case, if one or more of the multiple PRBs corresponding to the FD component are lost within the edge subband, while at least one of the multiple PRBs still exists within the edge subband transmitting the FD component, then in some example embodiments, gNB 120 may not allocate additional REs to compensate for the lost PRBs. Alternatively, the FD component transmitted on the existing PRBs can reuse the PRBs lost within the edge subband. For example, refer to... Figure 3 and 6B The FD components "1" and "2" transmitted on the first and second PRBs in the first sub-band can be reused to compensate for the third and fourth PRBs lost in the first sub-band; and the FD components "1" and "2" transmitted on the first and second PRBs in the last sub-band can be reused to compensate for the third and fourth PRBs dropped in the last sub-band. Since no additional RE is required, the offset indicator can have a value (t=0, f=0) or be omitted. Conversely, refer to... Figure 3 and 6C Both PRBs corresponding to FD component "2" are lost; and in the first and last subbands, no PRBs transmit FD component "2". Therefore, as described above, gNB 120 still needs to allocate additional REs to transmit FD component "2".

[0060] Return to reference Figure 4 At operation 230, gNB 120 can receive UL pilots such as probe reference signals (SRS) from UE 110.

[0061] Then, at operation 240, based on the multipath delay of the radio channel between gNB 120 and UE 110, gNB 120 can determine one or more FD components. For example, assuming partial channel reciprocity between the uplink channel from UE 110 to gNB 120 and the downlink channel from gNB 120 to UE 110, gNB 120 can determine the FD components by measuring UL pilots such as SRS. For example, gNB 120 can perform FD transformation on the obtained UL channel elements over the entire UL bandwidth and select the optimal M0 FD components.

[0062] At operation 250, the gNB 120 can precode the CSI-RS port using the FD components. As described above, the FD components are DFT vectors comprising N3 precoding coefficients; and, over the N3 subbands within the bandwidth, the gNB 120 can precode M0 FD components over M PRB sets for the beamformed CSI-RS port.

[0063] At operation 260, based on information regarding the CSI-RS resource mapping, gNB 120 can transmit precoded CSI-RS. As described above, the information regarding the CSI-RS resource mapping indicates the resource allocation of the CSI-RS port, including additional resource elements allocated to compensate for lost PRBs in edge subbands. Therefore, FD components can be fully transmitted on the allocated resources. In other words, the edge precoding coefficients in the FD component vector are not lost due to missing PRBs in the edge subbands. At operation 260, based on the information regarding the CSI-RS resource mapping received in operation 210, UE 110 can receive the complete CSI-RS resources.

[0064] At operation 270, UE 110 can combine the beamforming channel information obtained by CSI-RS measurements on each PRB set and obtain linear combination (LC) coefficients for each CSI-RS port. UE 110 can then report these LC coefficients to gNB 120.

[0065] Figure 7 A flowchart of a method 300 for transmitting CSI-RS according to an example embodiment of this application is shown. For example, method 300 can be performed in... Figure 1 The implementation is shown at gNB 120. Figure 7 The steps of method 300 are shown, which can be performed by means, modules, or elements of a device implemented at gNB 120. Since, reference Figures 1-6C The details of method 300 have been described above; for convenience, a brief description of method 300 will be provided here. It should be understood that the following description of method 300 may refer to references to... Figures 1-6C Please read the above description for better understanding.

[0066] Reference Figure 7 Method 300 may include: step S310, sending information about CSI-RS resource mapping to UE 110. The information about CSI-RS resource mapping may be sent via RRC signaling; and it may include: first information indicating the allocation of one or more resource elements in the PRB for one or more CSI-RS ports; and second information indicating the allocation of one or more additional REs in the PRB for one or more CSI-RS ports. It should be understood that the first information may be configured for subbands within the bandwidth on which gNB 120 operates; while the second information may be configured for at least one or two edge subbands of the bandwidth.

[0067] In some example embodiments, the second information may include an offset indicator indicating the offset of one or more additional REs relative to one or more REs in the time and / or frequency domains. That is, one or more additional REs can be determined by: determining one or more REs based on the first information; and then moving one or more REs in the time and / or frequency domains based on the offset indicator. Specifically, if the offset indicator has a zero value for both the time-domain offset and the frequency-domain offset, no additional RE is assigned.

[0068] Optionally, at step S320, gNB 120 may also send CSI-RS configuration information to UE 110. The CSI-RS configuration information may indicate the sequence of FD components within the bandwidth mapped to the PRB set. In some example embodiments, the CSI-RS configuration information may include a bit string indicating the sequence number of the FD components mapped to the PRB set. The CSI-RS configuration information can be sent via RRC signaling or downlink control information (DCI).

[0069] At step S330, based on the multipath delay of the radio channel between gNB 120 and UE 110, gNB 120 can determine one or more FD components. For example, assuming partial channel reciprocity between the uplink channel from UE 110 to gNB 120 and the downlink channel from gNB 120 to UE 110, gNB 120 can determine the FD components by measuring, for example, the UL pilot of the sounding reference signal (SRS) received from UE 110. The FD components are determined at the subband level and have a length equal to the number of subbands included in the bandwidth.

[0070] At step S340, gNB 120 may precode the CSI-RS using one or more FD components determined in step S330. The CSI-RS may be configured with one or more CSI-RS ports; and these CSI-RS ports may be precoded using one or more FD components respectively.

[0071] Next, at step S350, based on information about the CSI-RS resource mapping, gNB 120 can transmit CSI-RS precoded using one or more FD components to UE 110. gNB 120 can transmit CSI-RS over a bandwidth of N3 subbands, including edge subbands and at least one non-edge subband. The non-edge subbands can include M PRBs, while the edge subbands can include M1 PRBs, where M ≥ M1. The bandwidth of PRBs can be divided into M sets of PRBs; and each of the M sets of PRBs can include PRBs within its respective subband. Figure 2As shown, if the subbands have the same size (M1 = M), then the M PRB sets have the same size N3. As Figure 3 shown, if the size of the edge subbands is smaller than that of the non-edge subbands (M1 < M), then the size of the M1 PRB sets is N3, while the remaining (M - M1) PRB sets will have a smaller size (N3 - 1) or (N3 - 2).

[0072] One or more FD components can be mapped to the M PRB sets in a predefined sequence; and, the predefined sequence can be indicated by the CSI-RS configuration information sent to UE 110 in step 320, or pre-configured at gNB 120 and UE 110. When the number M of PRB sets is greater than the number M0 of FD components, one or more FD components can be mapped to multiple PRB sets to improve channel estimation accuracy.

[0073] As described above, the size of the FD component is N3, i.e., it includes N3 precoding coefficients. As Figure 2 shown, when the subbands have the same size (M1 = M), the M PRB sets also have the size N3, i.e., they include N3 PRBs distributed on N3 subbands. In such a case, according to the first information included in the information regarding CSI-RS resource mapping, the CSI-RS precoded with the FD component can be transmitted on the REs in each of the allocated PRBs, and no additional resources are required. The offset indicator of the second information for allocating additional resources can have a value (t = 0, f = 0) or be omitted.

[0074] On the other hand, if the edge subbands have a size smaller than that of the non-edge subbands (M1 < M), according to the first information of the information regarding CSI-RS resource mapping, in addition to the resources allocated in the existing PRBs, additional resources are required to compensate for the edge subbands of the missing PRBs. For example, if the first subband contains P fewer PRBs than the non-edge subbands (M - M1 = P), then the second information can indicate to allocate one or more additional REs in the first P PRBs of the bandwidth to compensate for the first subband missing P PRBs. One or more of the additional REs in the first P PRBs can be configured to transmit one or more CSI-RS ports precoded with the first precoding coefficients corresponding to the P missing PRBs in the first subband. If the last subband contains Q fewer PRBs than the non-edge subbands (M - M1 = Q), then the second information can indicate to allocate one or more additional REs in the last Q PRBs of the bandwidth. One or more of the additional REs in the last Q PRBs can be configured to transmit one or more CSI-RS ports precoded with the last precoding coefficients corresponding to the Q resource blocks missing in the last subband.

[0075] In some embodiments, if the PRB lost within the edge subband corresponds to an FD component transmitted on a PRB also included in the edge subband, then the lost PRB does not need to be compensated because the FD component on an existing PRB within the edge subband can be reused for the lost PRB. For example, refer to Figure 3 and 6B Since the lost third and fourth PRBs correspond to the FD components "1" and "2" transmitted on the first and second PRBs according to the bit string "1212", the FD components "1" and "2" transmitted on the first and second PRBs in the edge subband can be reused for the lost third and fourth PRBs in the edge subband. In this case, the offset indicator used to allocate the additional RE can have a value (t=0, f=0) or be omitted.

[0076] Figure 8 A flowchart of a method 400 for receiving CSI-RS according to an example embodiment of this application is shown. For example, method 400 can be performed in... Figure 1 The implementation is shown at UE 110. Figure 8 The steps of method 400 are shown, which can be performed by means, modules, or elements of a device implemented at UE 110. Since some details of method 400 have already been referenced above... Figures 1-7 The discussion has been conducted, and a brief description of Method 400 is given here. For ease of understanding, the following description of Method 400 can be found in [reference needed]. Figures 1-7 Read the relevant descriptions.

[0077] refer to Figure 8 Method 400 may begin at step S410, receiving information about CSI-RS resource mapping from gNB 120. The information about CSI-RS resource mapping may include: first information indicating the allocation of one or more resource elements in a PRB for one or more CSI-RS ports; and second information indicating the allocation of one or more additional resource elements in a PRB for one or more CSI-RS ports. The first information may configure subbands within the bandwidth on which gNB 120 operates; while the second information may be configured for at least one or two edge subbands of the bandwidth. In some example embodiments, the second information may include: an offset indicator indicating the offset of one or more additional REs relative to one or more REs in the time domain and / or frequency domain.

[0078] At step S420, UE 110 may optionally receive CSI-RS configuration information from gNB 120. The CSI-RS configuration information may indicate the sequence of FD components mapped to PRB sets within the bandwidth. When the number of FD components M0 is less than the number of PRB sets M, one or more FD components may be mapped to more than one PRB set. In some example embodiments, the CSI-RS configuration information may include bit strings, etc., to indicate the sequence number of the FD components mapped to the PRB set.

[0079] At step S430, UE 110 may send a UL pilot such as a probe reference signal (SRS) to gNB 120.

[0080] At step S440, based on information regarding the CSI-RS resource mapping, UE 110 can receive CSI-RS from gNB 120. The CSI-RS can be configured using one or more CSI-RS ports precoded with FD components. Based on the multipath delay of the radio channel between gNB 120 and UE 110, the one or more FD components can be determined by assuming partial channel reciprocity between the uplink channel from UE 110 to gNB 120 and the downlink channel from gNB 120 to UE 110.

[0081] In step S440, based on the CSI-RS resource mapping information received in step S410, UE 110 can determine the resources used for CSI-RS and receive CSI-RS on the determined resources. CSI-RS can be received over a bandwidth of N3 subbands, including edge subbands and at least one non-edge subband; the non-edge subbands may include M PRBs, and the edge subbands may include M1 PRBs. For example, from the subband size parameter... Sequence number of the starting PRB in the bandwidth and the bandwidth received from higher layers UE 110 can determine the edge subband size and non-edge subband size.

[0082] For non-edge subbands and edge subbands with the same size as the non-edge subbands (M1 = M), UE 110 can receive CSI-RS on REs of M PRBs according to the first information contained in the information about CSI-RS resource mapping; and the second information contained in the information about CSI-RS resource mapping can be ignored.

[0083] If the first subband within the bandwidth contains P fewer PRBs than the non-edge subband (M-M1=P), then UE 110 can receive CSI-RS on REs of M1 PRBs in the first subband indicated by the first information, and further on additional REs of the first P P PRBs in the bandwidth indicated by the second information.

[0084] If the last subband within the bandwidth contains Q fewer PRBs than the non-edge subband (M-M1=Q), then UE 110 can receive CSI-RS on REs of M1 PRBs in the last subband indicated by the first information, and further on additional REs of the last Q PRBs in the bandwidth indicated by the second information.

[0085] In some example embodiments, the FD component can be mapped to more than one PRB set, such as a first PRB set and a second PRB set. When a PRB of the first PRB set is included in the edge subband while a PRB of the second PRB set is missing in the edge subband, UE 110 can receive CSI-RS on the PRBs within the edge subband used for the first PRB set, and reuse the CSI-RS received on that PRB for the missing PRBs of the second PRB set in the edge subband. For example, refer to... Figure 3 and 6B UE 110 can reuse the FD components "1" and "2" received on the first and second PRBs in the edge subband for the missing third and fourth PRBs in the edge subband. In this case, the second information used to allocate the additional RE can have a value (t=0, f=0) or be omitted.

[0086] At step S450, UE 110 can combine the beamforming channel information obtained by CSI-RS measurements of each PRB set and obtain linear combination (LC) coefficients for each CSI-RS port. Then, UE 110 can report the LC coefficients to gNB120.

[0087] Figure 9 A block diagram of an example communication system 500 that can implement embodiments of this application is shown. Figure 9 As shown, the communication system 500 may include: a terminal device 510, which can be implemented as Figure 1 The UE 110 shown; and the network device 520, which can be implemented as Figure 1 Base station 120 is shown. Although, Figure 9 Only one terminal device 510 is shown; however, it will be understood that the communication system 500 may include multiple terminal devices 510 wirelessly connected to the network device 520.

[0088] refer to Figure 9Terminal device 510 may include one or more processors 511, one or more memories 512, and one or more transceivers 513 interconnected via one or more buses 514. The one or more buses 514 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, copper cables, optical fibers, or other electrical / optical communication devices. Each of the one or more transceivers 513 may include a receiver and a transmitter connected to one or more antennas 516. Terminal device 510 may wirelessly communicate with network device 520 via one or more antennas 516. The one or more memories 512 may include computer program code 515. The one or more memories 512 and computer program code 515 may be configured to, when executed by one or more processors 511, cause terminal device 510 to perform the processes and steps described above related to UE 110.

[0089] Network device 520 may include one or more processors 521, one or more memories 522, one or more transceivers 523, and one or more network interfaces 527 interconnected via one or more buses 524. The one or more buses 524 may be address, data, or control buses and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, copper cables, optical fibers, or other electrical / optical communication devices. Each of the one or more transceivers 523 may include a receiver and a transmitter connected to one or more antennas 526. Network device 520 may operate as a base station for terminal device 510 and wirelessly communicate with terminal device 510 via one or more antennas 526. The one or more network interfaces 527 may provide wired or wireless communication links through which network device 520 may communicate with other network devices, entities, or functions. The one or more memories 522 may include computer program code 525. The one or more memories 522 and computer program code 525 may be configured, when executed by one or more processors 521, to cause network device 520 to perform the processes and steps described above related to base station 120.

[0090] The aforementioned one or more processors 511, 521 can be any suitable type appropriate for the local technology network, and can include one or more general-purpose processors, dedicated processors, microprocessors, digital signal processors (DSPs), processors based on multi-core processor architectures, and dedicated processors such as those developed based on field-programmable gate arrays (FPGAs) and application-specific integrated circuits (ASICs). The one or more processors 511, 521 can be configured to control other elements of the UE / network device and cooperate with them to implement the aforementioned processes.

[0091] One or more memories 512, 522 may include at least one storage medium of various forms, such as volatile memory and / or non-volatile memory. Volatile memory may include, but is not limited to, random access memory (RAM) or cache. Non-volatile memory may include, but is not limited to, read-only memory (ROM), hard disk, flash memory, etc. Furthermore, one or more memories 512, 522 may include, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or apparatuses, or any combination thereof.

[0092] The network device 520 can be implemented as a single network node, or decomposed / distributed across two or more network nodes, such as a central unit (CU), a distributed unit (DU), or a remote radio headend (RRH), using different functional splitting architectures and different interfaces.

[0093] It should be understood that the blocks in the figures can be implemented in various ways, including software, hardware, firmware, or any combination thereof. In some exemplary embodiments, one or more blocks may be implemented using software and / or firmware, such as machine-executable instructions stored in a storage medium. In addition to or instead of machine-executable instructions, some or all of the blocks in the figures, at least in part, may be implemented by one or more hardware logic elements. Exemplary types of hardware logic elements that may be used, such as but not limited to, include: Field-Programmable Gate Arrays (FPGAs), Application-Specific Integrated Circuits (ASICs), Application Standard Products (ASSPs), System-on-Chip (SOCs), Complex Programmable Logic Devices (CPLDs), etc.

[0094] Some exemplary embodiments also provide computer program code or instructions that, when executed by one or more processors, cause a device or apparatus to perform the processes described above. The computer program code for performing the processes of the exemplary embodiments can be written in any combination of one or more programming languages. The computer program code can be provided to one or more processors or controllers of a general-purpose computer, special-purpose computer, or other programmable data processing apparatus such that, when executed by the processor or controller, the functions / operations specified in the flowcharts and / or block diagrams are implemented. The program code can be executed entirely on the machine, partially on the machine, as a stand-alone software package, partially on a computer and partially on a remote machine, or entirely on a remote machine or server.

[0095] Some exemplary embodiments also provide a computer program product implemented in a computer-readable medium including computer program code or instructions. The computer-readable medium can be any tangible medium that may contain or store a program used or associated with an instruction execution system, apparatus, or device. The machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. Machine-readable media may include, but are not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination thereof. More specific examples of machine-readable storage media will include electrical connections having one or more wires, portable computer floppy disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0096] Furthermore, although the operations are described in a specific order, this should not be construed as requiring that such operations be performed in the specific order or sequence shown, or that all illustrated operations be performed to obtain the desired result. In some cases, multitasking and parallel processing can be advantageous. Similarly, although several specific implementation details are included in the foregoing discussion, they should not be construed as limiting the scope of this application, but rather as descriptions of features that may be specific to particular embodiments. Certain features described in the context of a single embodiment may also be implemented in combination with that single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments.

[0097] Although the subject matter has been described in terms of specific structural features and / or methodological actions, it should be understood that the subject matter defined in the appended claims is not limited to the specific features or actions described above. Rather, the specific features and actions described above are disclosed as examples of implementing the claims.

Claims

1. A network device, comprising: At least one processor; as well as At least one memory including computer program code, said at least one memory and said computer program code being configured to utilize said at least one processor to cause the network device to: Sending information about Channel State Information Reference Signal (CSI-RS) resource mapping to terminal devices, the information about CSI-RS resource mapping including: first information indicating the allocation of one or more resource elements in a resource block for one or more CSI-RS ports; and second information indicating the allocation of one or more additional resource elements in the resource block for the one or more CSI-RS ports, the second information being configured for edge subband; CSI-RS is precoded using one or more frequency domain FD components; and Based on the information regarding CSI-RS resource mapping, CSI-RS is sent to the terminal device.

2. A terminal device, comprising: At least one processor; as well as At least one memory including computer program code, said at least one memory and said computer program code being configured to utilize said at least one processor to cause the terminal device to: Information about Channel State Information Reference Signal (CSI-RS) resource mapping is received from a network device. The information about CSI-RS resource mapping includes: first information indicating the allocation of one or more resource elements in a resource block for one or more CSI-RS ports; and second information indicating the allocation of one or more additional resource elements in the resource block for the one or more CSI-RS ports, wherein the second information is configured for edge subband. The CSI-RS is received from the network device based on the information regarding the CSI-RS resource mapping.

3. The terminal device according to claim 2, wherein, The second information includes an offset indicator that indicates the offset of the one or more additional resource elements relative to the one or more resource elements in the time domain and / or frequency domain.

4. The terminal device according to claim 2, wherein, Each CSI-RS port is precoded using one or more frequency domain FD components.

5. The terminal device according to claim 4, wherein, The one or more FD components are determined based on the multipath delay of the wireless channel between the network device and the terminal device.

6. The terminal device according to claim 2, wherein, The CSI-RS is received over a bandwidth comprising a first number of subbands, the first number of subbands including edge subbands and at least one non-edge subband, the at least one non-edge subband including a second number of resource blocks, the edge subband including a third number of resource blocks, the second number being greater than the third number. The CSI-RS ports are precoded using a fourth number of FD components.

7. The terminal device according to claim 6, wherein, For each CSI-RS port, the fourth number of FD components are mapped to a fifth number of resource block sets in a predetermined sequence, each resource block set including the corresponding resource block within each subband.

8. The terminal device according to claim 7, wherein, When the fifth quantity is greater than the fourth quantity, one or more FD components of the fourth quantity (M0) are mapped to more than one resource block set.

9. The terminal device according to claim 7, wherein, The at least one memory and the computer program code are further configured to utilize the at least one processor to further enable the terminal device: The network device receives CSI-RS configuration information, which indicates that the fourth number of FD components are mapped to a predetermined sequence of the fifth number of resource block sets.

10. The terminal device according to claim 6, wherein, The FD component includes precoding coefficients for each of the first number of subbands.

11. A method implemented on a network device, comprising: Sending information about Channel State Information Reference Signal (CSI-RS) resource mapping to terminal devices, the information about CSI-RS resource mapping including: first information indicating the allocation of one or more resource elements in a resource block for one or more CSI-RS ports; and second information indicating the allocation of one or more additional resource elements in the resource block for the one or more CSI-RS ports, the second information being configured for edge subband; CSI-RS is precoded using one or more frequency domain FD components; and Based on the information regarding CSI-RS resource mapping, CSI-RS is sent to the terminal device.

12. A method implemented on a terminal device, comprising: Information about Channel State Information Reference Signal (CSI-RS) resource mapping is received from a network device. The information about CSI-RS resource mapping includes: first information indicating the allocation of one or more resource elements in a resource block for one or more CSI-RS ports; and second information indicating the allocation of one or more additional resource elements in the resource block for the one or more CSI-RS ports, wherein the second information is configured for edge subband. The CSI-RS is received from the network device based on the information regarding the CSI-RS resource mapping.

13. The method according to claim 12, wherein, The second information includes an offset indicator that indicates the offset of the one or more additional resource elements relative to the one or more resource elements in the time domain and / or frequency domain.

14. The method of claim 12, wherein, The CSI-RS is received over a bandwidth comprising a first number of subbands, the first number of subbands including edge subbands and at least one non-edge subband, the at least one non-edge subband including a second number of resource blocks, the edge subband including a third number of resource blocks, the second number being greater than the third number. The CSI-RS ports are precoded using a fourth number of FD components.

15. The method of claim 14, further comprising: The network device receives CSI-RS configuration information, which indicates a predetermined sequence for mapping the fourth number of FD components to a fifth number of resource block sets, each of which includes corresponding resource blocks within its respective subband.

16. An apparatus for transmitting Channel State Information Reference Signal (CSI-RS), comprising: A means for transmitting information about Channel State Information Reference Signal (CSI-RS) resource mapping to a terminal device, the information about CSI-RS resource mapping including: first information indicating the allocation of one or more resource elements in a resource block for one or more CSI-RS ports; and second information indicating the allocation of one or more additional resource elements in the resource block for the one or more CSI-RS ports, the second information being configured for edge subband; A means for precoding CSI-RS using one or more frequency domain FD components; and A means for sending CSI-RS to the terminal device based on information about the CSI-RS resource mapping.

17. An apparatus for receiving a Channel State Information Reference Signal (CSI-RS), comprising: A means for receiving information about CSI-RS resource mapping from a network device, the information about CSI-RS resource mapping including: first information indicating the allocation of one or more resource elements to one or more CSI-RS port indication resource blocks; and second information indicating the allocation of one or more additional resource elements in the resource blocks to the one or more CSI-RS ports, the second information being configured for edge subband; and A means for receiving CSI-RS from the network device based on the information regarding CSI-RS resource mapping.

18. The device according to claim 17, wherein, Each CSI-RS port is precoded using a fourth number of FD components, and the device further includes: A means for receiving CSI-RS configuration information from the network device, the CSI-RS configuration information indicating a predetermined sequence for mapping the fourth number of FD components to a fifth number of resource block sets; the resource block sets each comprising corresponding resource blocks within each subband.

19. The device according to claim 18, wherein, FD components are mapped to a first resource block set and a second resource block set, and resource blocks of the first resource block set are included within the edge sub-band, while resource blocks of the second resource block set are missing within the edge sub-band. The apparatus for receiving the CSI-RS includes: Means for receiving the CSI-RS on the resource blocks in the edge subband of the first resource block set; and A means for reusing the received CSI-RS on resource blocks of missing resource blocks in the second resource block set within the edge subband.

20. A computer program product implemented in at least one computer-readable medium and including instructions, which, when executed by at least one processor in a network device, causes the network device to: Sending information about the Channel State Information Reference Signal (CSI-RS) resource mapping to the terminal device, wherein the information about the CSI-RS resource mapping includes: The first message indicates that one or more resource elements in a resource block are allocated to one or more CSI-RS ports; And, second information, indicating that one or more additional resource elements in the resource block are allocated for the one or more CSI-RS ports, the second information being configured for edge subband; CSI-RS is precoded using one or more frequency domain FD components; as well as Based on the information regarding CSI-RS resource mapping, CSI-RS is sent to the terminal device.

21. A computer program product implemented in at least one computer-readable medium and including instructions, which, when executed by at least one processor in a terminal device, causes the terminal device to: Receive information about the Channel State Information Reference Signal (CSI-RS) resource mapping from the network device, the information about the CSI-RS resource mapping including: The first message indicates that one or more resource elements in a resource block are allocated to one or more CSI-RS ports; And, second information, indicating that one or more additional resource elements in the resource block are allocated to the one or more CSI-RS ports, the second information being configured for edge subbands within the bandwidth; The CSI-RS is received from the network device based on the information regarding the CSI-RS resource mapping.

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