Channel state information feedback

Abstract

Embodiments of the present disclosure relate to methods, devices, apparatuses, and computer-readable storage media for channel state information (CSI) feedback. A first device determines a first indicator of a first CSI mode based on a current measurement of a channel between the first device and the second device. The first device determines a second indicator of a second CSI mode based at least in part on previous CSI feedback. Then, the first device selects a target CSI mode for current CSI feedback from the first CSI mode and the second CSI mode based on the first indicator and the second indicator. Through this dynamic design of explicit CSI feedback, by flexibly switching between different CSI modes, a trade-off between system performance and CSI feedback payload can be achieved, especially for new radio systems. In this way, gains in saving CSI payload and average cell throughput can be achieved.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to the field of telecommunications, and in particular to methods, devices, apparatuses, and computer-readable storage media for channel state information (CSI) feedback. Background Art

[0002] In 3GPP NR Rel-15, the Type 2 codebook has been introduced due to stronger performance gains than what could be achieved in 3GPP LTE Rel-14. In 3GPP NR Rel-16, the Type 2 codebook is further designed to specify and support frequency domain compression techniques, which can significantly reduce the CSI feedback overhead at each subband level without any performance loss.

[0003] With the advent of 5G New Radio (NR), in order to improve the system performance of Multi-User Multiple Input Multiple Output (MU-MIMO), the concept of massive Multiple Input Multiple Output (MIMO) is proposed, which is one of the key technologies proposed in NR. Current systems usually require finer granularity and higher accuracy channel feedback, as well as reasonable feedback overhead. In this case, CSI feedback with coarse frequency granularity will inevitably limit the improvement of MU precoding accuracy and MU-MIMO scheduling performance. Summary of the invention

[0004] In general, example embodiments of the present disclosure provide a solution for CSI feedback.

[0005] In a first aspect, a first device is provided. The first 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, using the at least one processor, cause the first device to: determine a first indicator of a first CSI mode based on a current measurement of a channel between the first device and a second device; determine a second indicator of a second CSI mode based at least in part on previous CSI feedback; and select a target CSI mode for current CSI feedback from the first CSI mode and the second CSI mode based on the first indicator and the second indicator.

[0006] In a second aspect, a second device is provided. The second 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, using the at least one processor, cause the second device to: determine a target CSI mode based on a first part of current CSI feedback of a channel between the first device and the second device, the target CSI mode being selected by the first device from a first CSI mode and a second CSI mode for the current CSI feedback; and receive a second part of the current CSI feedback based on the target CSI mode.

[0007] In a third aspect, a method implemented at a first device is provided. The method includes: determining a first indicator of a first CSI mode based on a current measurement of a channel between the first device and a second device; determining a second indicator of a second CSI mode based at least in part on previous CSI feedback; and selecting a target CSI mode for current CSI feedback from the first CSI mode and the second CSI mode based on the first indicator and the second indicator.

[0008] In a fourth aspect, a method implemented at a second device is provided. The method includes: determining a target CSI mode based on a first part of current CSI feedback of a channel between the first device and the second device, the target CSI mode being selected by the first device from a first CSI mode and a second CSI mode for the current CSI feedback; and receiving a second part of the current CSI feedback based on the target CSI mode.

[0009] In a fifth aspect, an apparatus is provided, comprising: a component for determining a first indicator of a first CSI mode based on a current measurement of a channel between a first device and a second device; a component for determining a second indicator of a second CSI mode based at least in part on previous CSI feedback; and a component for selecting a target CSI mode for current CSI feedback from the first CSI mode and the second CSI mode based on the first indicator and the second indicator.

[0010] In a sixth aspect, an apparatus is provided, comprising: a component for determining a target CSI mode based on a first part of current CSI feedback of a channel between a first device and a second device, the target CSI mode being selected from a first CSI mode and a second CSI mode for CSI feedback; and a component for receiving a second part of the current CSI feedback based at least in part on the target CSI mode.

[0011] In a seventh aspect, a non-transitory computer-readable medium is provided, comprising program instructions for causing an apparatus to at least execute the method according to the third aspect or the fourth aspect.

[0012] It should be understood that the invention summary is not intended to identify the key or essential features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0014] Figure 1 shows an example communication network in which example embodiments of the present disclosure may be implemented;

[0015] Figure 2 A flowchart of a method implemented at a first device according to some embodiments of the present disclosure is shown;

[0016] Figure 3 A flowchart showing a method implemented at a second device according to some other embodiments of the present disclosure is shown;

[0017] Figure 4 A signaling flow chart of CSI transmission according to some example embodiments of the present disclosure is shown;

[0018] Figure 5 shows a simplified block diagram of an apparatus suitable for implementing an embodiment of the present disclosure; and

[0019] Figure 6 A block diagram of an example computer-readable medium is shown in accordance with some embodiments of the present disclosure.

[0020] Throughout the drawings, the same or similar reference numerals refer to the same or similar elements. DETAILED DESCRIPTION

[0021] The principle of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described only for illustrative purposes and to help those skilled in the art understand and implement the present disclosure without implying any limitation on the scope of the present disclosure. The present disclosure described herein can be implemented in various ways except for the way described below.

[0022] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0023] In this disclosure, references to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is claimed that it is within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0024] It should be understood that although the terms "first" and "second" etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish between elements. For example, without departing from the scope of the exemplary embodiments, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0025] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the exemplary embodiments. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when the terms "include", "have" and / or "comprise" are used herein, these terms specify the presence of stated features, elements and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0026] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0027] (a) hardware circuit implementation only (such as implementation in analog and / or digital circuits only) and

[0028] (b) a combination of hardware circuitry and software such as (where applicable):

[0029] (i) a combination of analog and / or digital hardware circuits and software / firmware and

[0030] (ii) any portion of a hardware processor(s) with software (including digital signal processor(s), software and memory(s) that work together to enable a device such as a mobile phone or server to perform various functions) and

[0031] (c) Hardware circuit(s) and / or processor(s) that require software (e.g., firmware) to operate, such as microprocessor(s) or portions of microprocessor(s), but which may not be present when no software is needed for operation.

[0032] This definition of circuitry applies to all uses of this term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term "circuitry" also covers, for example and if applicable to a particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0033] As used herein, the term "communication network" refers to a network that complies with any suitable communication standard, such as, Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High Speed ​​Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), etc. In addition, the communication between the terminal device and the network equipment in the communication network can be performed according to any suitable generation of communication protocols, including but not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, future fifth generation (5G) communication protocols and / or any other protocols currently known or to be developed in the future. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of the communication field, there will certainly be future types of communication technologies and systems that can be used to implement the present disclosure. It should not be regarded as limiting the scope of the present disclosure to only the aforementioned systems.

[0034] As used herein, the term "first device" refers to any terminal device capable of wireless communication. In some embodiments, the first device may be a terminal device. As an example and not limitation, the terminal device may also be referred to as a communication device, a user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS), or an access terminal (AT). The terminal device may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a voice over IP (VoIP) phone, a wireless local loop phone, a tablet computer, a wearable terminal device, a personal digital assistant (PDA), a portable computer, a desktop computer, an image capture terminal device such as a digital camera, a game terminal device, a music storage and playback device, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop embedded device (LEE), a laptop mounted device (LME), a USB dongle, a smart device, a wireless customer enterprise equipment (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head mounted display (HMD), a vehicle, a drone, medical equipment and applications (e.g., remote surgery), industrial equipment and applications (e.g., robots and / or other wireless devices operating in an industrial and / or automated process chain environment), consumer electronic devices, devices operating on a commercial and / or industrial wireless network, etc. In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

[0035] The term "second device" refers to a node in a communication network, via which a terminal device accesses the network and receives services therefrom. In some embodiments, the second device may be a network device. The network device may refer to a base station (BS) or an access point (AP), for example, a Node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also known as a gNB), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, a low-power node such as a femto, a micro, etc., depending on the terminology and technology applied.

[0036] An explicit CSI feedback design is proposed to exploit the sparsity of the time domain channel, reduce the CSI feedback overhead, and improve the CSI accuracy. According to a specific compression standard such as orthogonal matching pursuit (OMP), important channel taps are selected from all channel taps in the time domain channel to form a sparse basis matrix, which includes, for example, a discrete Fourier transform (DFT) vector. Since both the first device (e.g., UE) and the second device (e.g., gNB) sides know the DFT basis design, that is, a predetermined set of DFT vectors, the first device only needs to report the index of the DFT vector corresponding to the valid channel tap. The second device can then reconstruct the sparse basis matrix by the index of the DFT vector. In this case, the CSI feedback overhead mainly depends on the quantization of the compressed linear combination (LC) coefficients, which is related to the number of valid channel taps between the first device and the second device.

[0037] Another CSI feedback design is proposed to provide better channel compression behavior by using channel statistics based on Karhunen-Loeve transform (KLT). f ×N f The dominant eigenvector of the frequency domain (FD) covariance matrix constructs a sparse basis matrix, where N f In this case, since the sparse base matrix is ​​unknown to the second device, a higher feedback overhead is required for the quantization of the LC coefficients and the quantization of the sparse base matrix.

[0038] As mentioned above, MU-MIMO technology places higher requirements on system performance. Therefore, a new CSI feedback design is needed to achieve finer granularity and higher channel feedback accuracy as well as reasonable feedback overhead.

[0039] Embodiments of the present disclosure provide a dynamic scheme for explicit CSI feedback. In the dynamic scheme, the target CSI mode of the current CSI feedback can be switched between different CSI modes by using high-level configuration parameters (such as a switching factor α). For example, in each feedback instance, the first device (e.g., UE) can select a target CSI mode so that the best compromise between system performance and CSI feedback payload can be achieved. This scheme can save CSI payload and improve the average cell throughput by flexibly switching between different CSI modes.

[0040] In a communication network where multiple network devices are jointly deployed in a geographic area to serve each cell, when a terminal device is located in a corresponding cell, it can have an active connection with the network device. In an active connection, the terminal device can communicate with the network device on both the uplink (UL) and downlink (DL) frequency bands. Due to various reasons such as quality degradation in the UL, the terminal device may need to switch a link in one direction such as the UL to another network device. Some example embodiments of the present disclosure will be described below with reference to the accompanying drawings. However, it will be readily appreciated by those skilled in the art that the detailed description given here for these drawings is for explanatory purposes, because the present disclosure goes beyond these limited embodiments.

[0041] Figure 1 An example communication network 100 in which implementations of the present disclosure may be implemented is shown. The communication network 100 includes a first device 110 and a second device 120. For example, the network 100 may provide one or more cells to serve the first device 110. It should be understood that the number of first devices, second devices, and / or cells is given for illustrative purposes and does not imply any limitation of the present disclosure. The communication network 100 may include any appropriate number of network devices, terminal devices, and / or cells suitable for implementing implementations of the present disclosure.

[0042] In the communication network 100, the first device 110 may transmit data and CSI feedback to the second device 120, and the second device 120 may allocate resources to the first device 110 and receive CSI feedback from the first device 110. A link from the first device 110 to the second device 120 is referred to as an uplink (UL), and a link from the second device 120 to the first device 110 is referred to as a downlink (DL).

[0043] The CSI may ensure the reliability of wireless communication between the first device 110 and the second device 120. The process of reporting the CSI is also referred to as “CSI feedback”. In order to obtain the CSI of the communication channel between the first device 110 and the second device 120, the second device 120 may allocate resources to the first device 110. Then, the first device 110 may report the CSI to the second device 120 on the PUSCH.

[0044] Communications in network 100 may conform to any appropriate standard, including, but not limited to, Global System for Mobile Communications (GSM), Long Term Evolution (LTE), LTE-Evolution, LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), GSM EDGE Radio Access Network (GERAN), etc. In addition, communications may be performed according to any generation of communications protocols currently known or to be developed in the future. Examples of communications protocols include, but are not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G) communications protocols.

[0045] The CSI feedback includes a set of CSI feedback parameters, which can be divided into two parts, namely CSI Part 1 and CSI Part 2. CSI Part 1 has a fixed payload size, while CSI Part 2 has a variable payload size, depending on the parameters included in CSI Part 1. This two-part CSI structure will be discussed in detail below.

[0046] Figure 2 FIG. 2 is a flowchart of a method 200 implemented at a first device according to some example embodiments of the present disclosure. For discussion purposes, reference will be made to Figure 1 200. Process 200 may involve Figure 1 A first device 110 and a second device 120 are shown.

[0047] As described above, the first device 110 may measure the channel between the first device 110 and the second device 120 based on the current measurement of the downlink channel (e.g., the measurement of the CSI reference signal (CSI-RS)). Then, the first device 110 may determine the channel matrix H for characterizing the channel based on the current measurement of the channel. FD In other words, the channel matrix H FD The measured channel may be indicated.

[0048] In some example embodiments, the channel matrix H FD It can be based on the dimension N obtained from downlink measurement f ×N p The frequency domain matrix, and the channel matrix H FD It can be expressed as follows:

[0049]

[0050] Among them, N f is the number of active subcarriers, N p =N tx ×N rxis the number of channel paths, each path connecting the transmit port of the second device 120 and the receive port of the first device 110, N tx is the number of transmission ports of the second device 120, and N rx is the number of receiving ports of the first device 110 .

[0051] In some example embodiments, without spatial compression, the number of transmit ports may be the number of transmit antennas of the second device. If spatial compression is performed, spatial beams may be formed and the number of transmit ports may be the number of spatial beams.

[0052] If there is no spatial compression, the number of receive ports may be the number of receive antennas of the first device. If a spatial transformation is performed, spatial beams may also be formed, and the number of receive ports may be the number of spatial beams.

[0053] In some example embodiments, a set of discrete Fourier transform (DFT) vectors may be predetermined and known by both the first device 110 and the second device 120. The first device 110 may select at least a portion of the DFT vectors to form a vector having a size of N. f ×N p The first fundamental matrix Where N tap is the number of dominant taps. At least a portion of the DFT vector can be determined, for example, by an OMP search rule. Then, the channel matrix H FD Compressed into the first transformation matrix H TD1 The first transformation matrix H TD1 The formula can be is determined by the formula with lower dimension N tap ×N p The compressed linear combination (LC) coefficients are composed of N, because the number of dominant taps is tap Much smaller than the number of active subcarriers N f In this embodiment, the first basic matrix For all N p The channel paths are common and can be represented as

[0054]

[0055] Then, the first transformation matrix H TD1 can be quantized to obtain the first transformation matrix H TD1 The quantitative version of Next, we can use the formula To recover the quantized channel matrix It represents the estimated channel. Finally, the estimated channel is calculated The channel H of the current measurement FD The normalized mean square error (NMSE) between can be calculated as follows:

[0056]

[0057] Reference now Figure 2 At 210, the first device 110 may determine a first indicator of a first CSI pattern based on a current measurement of a channel. In this embodiment, the first indicator may be NMSE DFT .

[0058] In some example embodiments, the first CSI mode may be designed to feedback the following CSI parameters, including but not limited to, a first basic matrix The selected tap index set in , and the first transformation matrix H TD1 The quantitative version of ) tap ×N p It should be understood that the first CSI mode may include other necessary CSI parameters for reconstructing channel information.

[0059] At 220, first device 110 may determine a second indicator for the second CSI pattern based at least in part on the previous CSI feedback. In some example embodiments, the second indicator for the second CSI pattern is determined based on the previous CSI feedback and a current measurement of the channel.

[0060] In addition to the current measurement of the channel, the second CSI mode may also take into account previous CSI feedback. For example, the second CSI mode may utilize the Karhunen-Loeve transform (KLT), which results in very limited CSI feedback overhead.

[0061] In this embodiment, the estimation matrix is ​​reconstructed by utilizing the previous feedback information that has been shared to both the first device 110 and the second device 120. Estimation Matrix can be expressed as follows:

[0062]

[0063] in is the estimated channel vector in the previous feedback instance, with size N_f×1 for channel path n, and n=1,…,N p .

[0064] As an example, according to the KLT operation, for channel path n, only one tap is considered, because after the KLT operation, all the energy of the FD channel is integrated in this tap. The second basis vector associated with channel path n can be obtained by the following two options:

[0065] In option 1, the estimation matrix can be determined The covariance matrix R H and its eigendecomposition (ED), and the second basis vector is the dominant eigenvector from U as follows:

[0066]

[0067]

[0068] The covariance matrix R H The dimension is N f ×N f , and U consists of the eigenvectors, and Σ consists of the eigenvalues ​​along the main diagonal.

[0069] Alternatively, in option 2, the channel vector is estimated is normalized, and the channel vector The normalized version of is used directly as the second basis vector As shown below:

[0070]

[0071] Therefore, for channel path n, the second basis vector The channel vector for the current measurement can then be used FD compression in is the current channel matrix H FD After FD compression, the corresponding LC coefficients are calculated for channel path n as follows:

[0072]

[0073] LC coefficients for all channel paths can be quantified as And form the second transformation matrix H TD2 The quantitative version of The estimated channel matrix can then be obtained as follows:

[0074]

[0075] Similarly, estimating the channel The channel H of the current measurement FD The normalized mean square error (NMSE) between can be calculated as follows:

[0076]

[0077] In this embodiment, the second indicator may be NMSE KLT , and the second CSI mode can be designed to feed back the quantized second transformation matrix 1×N p LC coefficients without feeding back a second basis matrix including a set of basis vectors because they are determined according to previous CSI feedback known in both the first device 110 and the second device 120. It should be understood that the second CSI pattern may include other necessary CSI parameters for reconstructing channel information.

[0078] At 230 , the first device 110 may select a target CSI mode for current CSI feedback from the first CSI mode and the second CSI mode based on the first indicator and the second indicator.

[0079] In some example embodiments, first device 110 may receive a switching factor α for selecting a target CSI mode from second device 120 via a high-layer RRC signaling message. A switching factor α ranging from 0 to 1 (i.e., α∈[0,1]) is defined for adjusting and comparing the first indicator and the second indicator, such as the NMSE values ​​of the two CSI modes described above. Then, the target CSI mode of the current CSI feedback may be determined based on, for example, whether the following conditions are met:

[0080] NMSE KLT ×α≤NMSE DFT (11)

[0081] In this embodiment, the first CSI mode is a DFT-based CSI mode, and the second CSI mode is a KLT-based CSI mode. According to formula (11), the second indicator is adjusted by switching factor α. If the adjusted second indicator NMSE KLT , such as the value NMSE KLT The product of the switching factor α is greater than the first indicator NMSE DFT , the first CSI mode is selected as the target CSI mode. And if the adjusted second indicator is less than or equal to the first indicator NMSE DFT , the second CSI mode is selected as the target CSI mode.

[0082] Typically, the first CSI mode corresponding to the DFT-based CSI mode uses only the current measurement of the channel for CSI feedback, and thus has higher feedback accuracy; whereas the second CSI mode corresponding to the KLT-based CSI mode uses previous CSI feedback and currently measured channel information for CSI feedback, and thus has significantly lower CSI feedback overhead. According to an exemplary embodiment of the present invention, since the switching factor α effectively adjusts the switching probability of different CSI modes, the payload and system performance of the explicit CSI feedback can be flexibly controlled.

[0083] In some example embodiments, first device 110 may send current CSI feedback indicating a target CSI mode to second device 120. The current CSI feedback may include a CSI mode indicator for indicating the target CSI mode. This aspect will be discussed in detail below.

[0084] Figure 3 FIG. 3 is a flowchart of a method 300 implemented at a second device according to some other embodiments of the present disclosure. The method 300 may be implemented as follows: Figure 1 The second device 120 shown is implemented. For the purpose of discussion, reference will be made to Figure 1 Process 300 is described.

[0085] At 310, upon receiving current CSI feedback from the first device 110, the second device 120 may determine a target CSI mode based on a first portion of the current CSI feedback for a channel between the first device 110 and the second device 120. For example, the second device 120 may determine the target CSI mode based on a CSI mode indicator included in the first portion of the current CSI feedback.

[0086] At 320, the second device 120 may receive a second part of the current CSI feedback based at least in part on the target CSI pattern. Table 1 below lists CSI parameters included in the two-part CSI structure.

[0087] Table 1 - CSI parameters for CSI feedback

[0088]

[0089] In the above table, in CSI part 1,

[0090] 1) Define a CSI mode indicator to indicate the target CSI mode of the current CSI feedback;

[0091] 2) The number of non-zero (NZ) linear combination (LC) coefficients K. Typically, the maximum number of NZ LC coefficients K0 is defined as an RRC configuration parameter, where K0 ≤ N tap ×N p and Ntap ≥1 is also an RRC configuration parameter. Therefore, the number of NZ LC coefficients can be quantified as bits. In CSI Part 2:

[0092] 3) The selection of spatial domain (SD) beams is performed in the transmit port such as Rel.15 Type II CSI and occupies Bit;

[0093] 4) Only when the first CSI mode, i.e., the DFT-based CSI mode, is selected and the dimension is N f ×N f The selection of the channel tap is only sent when the DFT vector corresponding to the tap index is selected in the DFT matrix of the channel. Therefore, the indication of the selection of the tap set occupies Bit;

[0094] 5) The bitmap of the LC coefficients occupies different bits depending on the target CSI mode. If the first CSI mode corresponding to DFT-based explicit CSI is selected, N indicating the position and type of the LC coefficients (e.g., zero or non-zero LC coefficients) is used. tap ×2L×N rx The bitmap is defined by 2L×N bits. For example, "1" indicates a non-zero coefficient and "0" indicates a zero coefficient. It is not necessary to report the amplitude and phase values ​​of the zero coefficient according to the bitmap indication. If the second CSI mode corresponding to the KLT-based explicit CSI is selected, 2L×N rx The bits define the corresponding bitmap.

[0095] 6) For the strongest LC coefficient, use The bit signals the index of the strongest NZ LC coefficient.

[0096] 7) For LC coefficients, a total of K NZ LC coefficients are signaled according to amplitude and phase quantization. The strongest LC coefficient may have a different quantization bit length and quantization set than other LC coefficients.

[0097] It should be understood that the above CSI parameters are described for illustrative purposes only and do not imply any limitation on the scope of the present disclosure, and CSI feedback may include other necessary CSI parameters for reconstructing channel information.

[0098] In some example embodiments, in the case where it is determined that the target CSI mode is the first CSI mode, the second device 120 may obtain the first transformation matrix H TD1In this example, the first transformation matrix H is determined based on at least a portion of the current CSI feedback (such as the CSI mode indicator, the number K of NZ LC coefficients, the bitmap of LC coefficients, the strongest NZ LC coefficients, and the amplitude and phase quantization of the NZ LC coefficients). TD1 The bitmap indicates the first transformation matrix H TD1 The position and type of LC coefficients in the bitmap, and the size of the bitmap is associated with the number of at least a portion of the taps in the first device 110 and the number of receiving ports in the first device 110 and the number of transmitting ports in the second device 120.

[0099] In some example embodiments, in the case where it is determined that the target CSI mode is the second CSI mode, the second device 120 may at least obtain the second transformation matrix H TD2 In this example, the second transformation matrix H is determined based on at least a portion of the current CSI feedback. TD2 , and the bitmap indicates the second transformation matrix H TD2 The position and type of the LC coefficients in the bitmap, and the size of the bitmap is associated with the number of receiving ports in the first device 110 and the number of transmitting ports in the second device 120.

[0100] In some example embodiments, second device 120 may determine a first base matrix based on tap indices of at least a portion of the taps included in the second part of the current CSI feedback and a set of vectors shared by first device 110 and second device 120. The second device 120 may be based at least in part on the first base matrix and the first transformation matrix To reconstruct the channel matrix, that is, to estimate the channel matrix For example, through the formula

[0101] In some example embodiments, the second device 120 may determine the second base matrix based on previous CSI feedback. Then based at least in part on the second fundamental matrix and the second transformation matrix To reconstruct the channel matrix, that is, to estimate the channel matrix For example, through

[0102] According to an example embodiment of the present disclosure, the first CSI mode may utilize a DFT operation, while the second CSI mode may utilize an operation based on a Karhunen-Loeve transform.

[0103] Statistics and comparison of payload sizes under different CSI modes

[0104] In this section, the corresponding payload sizes of different CSI modes, such as DFT-based explicit CSI, KLT-based explicit CSI and dynamic explicit CSI, Rel-16 Type II CSI and Rel-15 Type II CSI are discussed and compared. It should be understood that the above CSI modes are discussed with reference to the following simulations for the purpose of illustration and not limitation. The parameters or configurations can be changed according to the different requirements of the simulation. For example, in some of the simulations discussed below, the parameters in CSI Part 1 are preset to default values, which can be determined according to system requirements, experimental values, etc. In addition, it should be understood that for the purpose of simulation, the bitmap can also be set to a predefined bitmap.

[0105] Now suppose

[0106] The number of transmit ports is 16, where (N1, N2) = (4, 2), and oversampling (O1, O2) = (4, 4);

[0107] The number of receiving ports is 2;

[0108] For polarization, the number of spatial domain (SD) beams is L=4; and

[0109] The number of active subcarriers is N f =600.

[0110] For simplicity, assume that the number of NZ LC coefficients is equal to the total number of LC coefficients N tap ×2L×N rx Therefore, the bitmap indication and CSI part 1 are not considered in the following statistics for explicit CSI payload.

[0111] Payload size of DFT-based CSI mode

[0112] The selection of SD beam is performed in the transmit port as in Rel-15 Type II CSI. bits to signal the selection of the SD beam. Assume the number of dominant taps is N tap =5, and the dimension of the DFT matrix is ​​600×600. Therefore, the indication of the selection of the tap set occupies Bit.

[0113] After selecting the SD beam and channel taps, the total number of LC coefficients is N tap ×2L×2=80. The strongest LC coefficient among all LC coefficients is used to signal the following contents respectively, using The bit is used to indicate the position and 4 bits are used for phase / amplitude quantization. The other LC coefficients are first normalized by the strongest coefficient and then quantized according to 4 bits of phase and 3 bits of amplitude respectively. Table 2 below lists the detailed statistics of the payload.

[0114] Table 2 - Payload statistics of DFT-based CSI modes

[0115]

[0116]

[0117] Payload size of CSI mode based on KLT

[0118] According to the KLT operation, each channel path has only one channel tap, so the total number of LC coefficients is 1×2L×2=16. The strongest of all LC coefficients is signaled as follows, using 1 bit is used for position indication and 4 bits are used for phase / amplitude quantization. The other LC coefficients are first normalized by the strongest coefficient and then quantized according to 4 bits of phase and 3 bits of amplitude, respectively. Sparse basis vectors (e.g., the second basis vector) do not need to be reported because they can be obtained based on previous CSI feedback information and are known on both the first device 110 and the second device 120 sides. Table 3 lists the detailed statistics of the payload of the KLT-based CSI mode.

[0119] Table 3 - Payload statistics of CSI mode based on KLT

[0120] CSI parameters Feedback Payload (bits) SD beam selection 11 Strongest LC coefficient (indication / phase / amplitude) 4+4+4＝12 Other LC coefficients (phase / amplitude) (16-1)×(4+3)＝105 Total Payload 128

[0121] Dynamic explicit CSI payload size

[0122] For dynamic explicit CSI, the payload size of each CSI mode is calculated separately as described above, and then the average payload size of dynamic explicit CSI feedback is determined to be (1-γ)×619+γ×128 based on the average switching ratio statistics, i.e., γ of the CSI mode selection probability based on KLT.

[0123] Rel-16 Type II CSI Payload Size

[0124] For Rel-16 Type II CSI, it is assumed that:

[0125] The number of configured PMI subbands is N3 = 13;

[0126] · Number of layers RI = 2;

[0127] The number of FD basis components is M = 8;

[0128] The total number of non-zero (NZ) LC coefficients across layers is K NZ =36;

[0129] The reference amplitude of the strongest FD coefficient in weak polarization is quantized to 4 bits;

[0130] For the remaining FD coefficients, the differential amplitude is quantized to 3 bits;

[0131] The phase quantization of the LC coefficients is 3 bits.

[0132] Table 4 lists the statistics of Rel-16 CSI payload.

[0133] Table 4 - Rel-16 Type II CSI payload statistics

[0134]

[0135] Rel-15 Type II CSI Payload Size

[0136] For Rel-15 Type II CSI, it is assumed that:

[0137] The number of configured PMI subbands is N3 = 13;

[0138] · Number of layers RI = 2;

[0139] The wideband amplitude of the LC coefficients is quantized to 3 bits;

[0140] The sub-band differential amplitude of the LC coefficient is quantized to 1 bit;

[0141] The subband phase of the LC coefficient is quantized to 3 bits;

[0142] The payload statistics of Rel-15 CSI are listed in Table 5.

[0143] Table 5 - Payload statistics for Rel-15 Type II CSI

[0144]

[0145]

[0146] Table 6 shows the comparison of the respective total payloads of the above CSI schemes.

[0147] Table 6 - Comparison of payload sizes for different CSI schemes

[0148] CSI Program Total payload (bits) Rel-15 Type II CSI 787 Rel-16 Type II CSI 377 DFT-based explicit CSI 619 Dynamic Explicit CSI (1-γ)×619+γ×128

[0149] Comparison of system performance

[0150] For the performance evaluation of the dynamic explicit CSI scheme provided according to the example embodiments of the present disclosure, a full-buffer system-level evaluation is performed in the LTE 3DUMA scenario. Results are provided for 16 transmit ports with (N1, N2) = (4, 2) in the horizontal and vertical dimensions, respectively. Table 7 below lists the relevant simulation parameters. Rel-15 and Rel-16 type IICSI are used as performance references. The simulation results are shown in Table 8.

[0151] Table 7 - Simulation assumptions for system-level evaluation

[0152]

[0153]

[0154] Table 8 - System-level evaluation of different CSI solutions

[0155]

[0156] As shown in Table 8, if the switching factor α is set to 1.0, only 18% of the CSI modes are selected as KLT-based explicit CSI, so without the need for mode switching, dynamic explicit CSI has very similar system performance to DFT-based explicit CSI with only 14% payload reduction.

[0157] If the switching factor α is set to 0.9, 62% of the CSI modes are switched to KLT-based explicit CSI that utilizes previous CSI feedback information, so dynamic explicit CSI significantly reduces the feedback overhead by 49% compared to the fixed DFT-based CSI mode with only limited performance loss. Compared with Rel.16 CSI, dynamic explicit CSI still has 16% payload saving capability and more than 10% cell average throughput gain. Therefore, adjusting the switching factor α can achieve a trade-off between system performance and feedback payload of dynamic explicit CSI feedback, and provides an effective implementation method for explicit CSI in Rel-17 NR MIMO.

[0158] Reference now Figure 4 , Figure 4 FIG. 4 is a signaling flow chart of CSI transmission according to some example embodiments of the present disclosure. Figure 1 The first device 110 and the second device 120 are implemented as shown. For the purpose of discussion, reference will be made to Figure 1 4. The process 400 is described below.

[0159] like Figure 4As shown, the first device 110 may determine 405 a first indicator of a first CSI mode based on a current measurement of a channel between the first device and the second device, and determine 410 a second indicator of a second CSI mode based at least in part on a previous CSI feedback. Then, the first device 110 may select 415 a target CSI mode for the current CSI feedback from the first CSI mode and the second CSI mode based on the first indicator and the second indicator. The first device 110 may send 420 the current CSI feedback indicating the target CSI mode to the second device 120. The current CSI feedback also includes other CSI parameters, such as the number K of NZLC coefficients, the selection of SD beams, the selection of channel taps, a bitmap of LC coefficients, etc.

[0160] After receiving the current CSI feedback, the second device 120 may determine 425 a target CSI mode based on the first part of the current CSI feedback. The second device 120 may receive 430 a second part of the current CSI feedback based at least in part on the target CSI mode. The second device 120 may then reconstruct 435 a channel matrix for characterizing the channel.

[0161] In some embodiments, an apparatus capable of performing any of the methods 200 (e.g., the first device 110) may include components for performing the various steps of the method 200. These components may be implemented in any suitable form. For example, these components may be implemented in a circuit or a software module.

[0162] In some embodiments, the apparatus includes: means for determining a first indicator for a first CSI mode based on a current measurement of a channel between the first device and the second device; means for determining a second indicator for a second CSI mode based at least in part on previous CSI feedback; and means for selecting a target CSI mode for current CSI feedback from the first CSI mode and the second CSI mode based on the first indicator and a second indicator CSI parameter set indicating a payload of at least a first portion of a target CSI report.

[0163] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of method 200. In some embodiments, these means comprise at least one processor; and at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause execution of the apparatus.

[0164] In some embodiments, the apparatus further comprises means for receiving, from the second device, a switching factor for selecting the target CSI pattern.

[0165] In some embodiments, the apparatus further comprises: a component for adjusting the second indicator by a switching factor; a component for selecting the first CSI mode as the target CSI mode in response to the adjusted second indicator being greater than the first indicator; and a component for selecting the second CSI mode as the target CSI mode in response to the adjusted second indicator being less than or equal to the first indicator.

[0166] In some embodiments, the apparatus further comprises: a component for generating a channel matrix for characterizing the channel based on a current measurement of the channel; a component for determining a first base matrix of tap indices indicating at least a portion of the taps of the channel matrix from a set of vectors shared by the first device and the second device; a component for determining a first transformation matrix based on the first base matrix and the channel matrix; a component for determining an estimated channel matrix based on the first transformation matrix and the first base matrix; and a component for determining a first indicator based on a difference between the channel matrix and the estimated channel matrix.

[0167] In some embodiments, the apparatus further comprises: a component for generating a channel matrix for characterizing a channel based on a current measurement of the channel; a component for determining a second base matrix based on previous CSI feedback; a component for determining a second transform matrix based on a second transform matrix and a channel matrix; a component for determining an estimated channel matrix based on the second transform matrix and the second base matrix; and a component for determining a second indicator based on a difference between the channel matrix and the estimated channel matrix.

[0168] In some embodiments, the apparatus further includes: a component for obtaining one or more estimated channel vectors corresponding to one or more channel paths between the first device and the second device from previous CSI feedback; a component for determining a corresponding covariance matrix for each of the one or more channel paths based on the corresponding estimated channel vectors; and a component for determining a second base matrix based on a corresponding dominant eigenvector of the covariance matrix for each of the one or more channel paths.

[0169] In some embodiments, the apparatus further includes: a component for obtaining one or more estimated channel vectors corresponding to one or more channel paths between the first device and the second device from previous CSI feedback; and a component for determining a second base matrix by normalizing each of the one or more estimated channel vectors of the corresponding channel path.

[0170] In some embodiments, the apparatus further comprises means for sending current CSI feedback indicating the target CSI mode to the second device.

[0171] In some embodiments, if the target CSI mode is the first CSI mode, the current CSI feedback includes at least a bitmap of the first transform matrix and tap indices of at least a portion of the taps associated with the channel matrix, the bitmap indicating the position and type of linear combination coefficients in the first transform matrix, and the size of the bitmap is associated with the number of at least a portion of the taps and the number of receive ports in the first device and the number of transmit ports in the second device.

[0172] In some embodiments, if the target CSI mode is the second CSI mode, the current CSI feedback includes at least a bitmap of the second transformation matrix, which indicates the position and type of linear combination coefficients in the second transformation matrix, and the size of the bitmap is associated with the number of receiving ports in the first device and the number of transmitting ports in the second device.

[0173] In some embodiments, the current CSI feedback includes a CSI mode indicator for indicating a target CSI mode.

[0174] In some embodiments, the first CSI mode utilizes discrete Fourier transform based operations.

[0175] In some embodiments, the second CSI mode utilizes an operation based on the Karhunen-Loeve transform.

[0176] In some embodiments, the first device is a terminal device and the second device is a network device.

[0177] In some embodiments, an apparatus capable of performing any of the processes 400 (e.g., the second device 120) may include components for performing the various steps of the processes 400. These components may be implemented in any suitable form. For example, these components may be implemented in circuits or software modules.

[0178] In some embodiments, the apparatus includes: a component for determining a target CSI mode based on a first portion of current CSI feedback for a channel between a first device and a second device, the target CSI mode being selected by the first device for the current CSI feedback from a first CSI mode and a second CSI mode; and a component for receiving a second portion of the current CSI feedback based at least in part on the target CSI mode.

[0179] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of process 400. In some embodiments, these means comprise at least one processor; and at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause execution of the apparatus.

[0180] In some embodiments, the apparatus further comprises: a component for obtaining, in response to determining that the target CSI mode is a first CSI mode, at least a bitmap of a first transform matrix and tap indices of at least a portion of taps associated with a channel matrix for characterizing a channel, wherein the first transform matrix is ​​determined based on at least a portion of current CSI feedback, and wherein the bitmap indicates locations and types of linear combination coefficients in the first transform matrix, and a size of the bitmap is associated with the number of at least a portion of the taps and the number of receive ports in the first device and the number of transmit ports in the second device.

[0181] In some embodiments, the apparatus further comprises: a component for determining a first base matrix based on tap indices of at least a portion of the taps included in the second part of the current CSI feedback and a set of vectors shared by the first device and the second device; and a component for reconstructing a channel matrix based at least in part on a bitmap of the first base matrix and the first transformation matrix.

[0182] In some embodiments, the apparatus further comprises: a component for obtaining, in response to determining that the target CSI mode is a second CSI mode, at least a bitmap of a second transformation matrix, wherein the second transformation matrix is ​​determined based on at least a portion of the current CSI feedback, and wherein the bitmap indicates the position and type of linear combination coefficients in the second transformation matrix, and a size of the bitmap is associated with the number of receive ports in the first device and the number of transmit ports in the second device.

[0183] In some embodiments, the apparatus further comprises: means for determining a second base matrix based on previous CSI feedback; and means for reconstructing the channel matrix based on the second base matrix and the second transformed matrix.

[0184] In some embodiments, the first CSI mode utilizes discrete Fourier transform based operations.

[0185] In some embodiments, the second CSI mode utilizes an operation based on the Karhunen-Loeve transform.

[0186] In some embodiments, the first device is a terminal device and the second device is a network device.

[0187] Figure 5 is a simplified block diagram of a device 500 suitable for implementing an embodiment of the present disclosure. The device 500 may be provided to implement a communication device, such as Figure 1 The first device 110 or the second device 120 is shown. As shown, the device 500 includes one or more processors 510, one or more memories 520 coupled to the processor 510, and one or more communication modules 540 coupled to the processor 510.

[0188] The communication module 540 is used for two-way communication. The communication module 540 has at least one antenna to facilitate communication. The communication interface may represent any interface required to communicate with other network elements.

[0189] Processor 510 may be of any type suitable for the local technology network, and may include one or more of the following: as non-limiting examples, a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 500 may have multiple processors, such as application specific integrated circuit chips that are time slaved to a clock synchronized with a main processor.

[0190] The memory 520 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 524, electrically programmable read-only memory (EPROM), flash memory, hard disk, compact disk (CD), digital video disk (DVD), and other magnetic storage and / or optical storage. Examples of volatile memories include, but are not limited to, random access memory (RAM) 522 and other volatile memories that do not persist over the duration of a power outage.

[0191] Computer program 530 includes computer executable instructions that are executed by associated processor 510. Program 530 may be stored in ROM 524. Processor 510 may perform any appropriate actions and processes by loading program 530 into RAM 522.

[0192] The embodiments of the present disclosure may be implemented by a program 530, so that the device 500 may execute the reference Figure 2 and Figure 3 Any process of the present disclosure discussed. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0193] In some embodiments, program 530 may be tangibly embodied in a computer-readable medium that may be included in device 500 (such as in memory 520) or in other storage devices accessible to device 500. Device 500 may load program 530 from the computer-readable medium to RAM 522 for execution. Computer-readable media may include any type of tangible, non-volatile storage device, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Figure 6 An example of a computer readable medium 600 in the form of a CD or DVD is shown. The computer readable medium has a program 530 stored thereon.

[0194] In general, various embodiments of the present disclosure may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are shown and described as block diagrams, flow charts, or using some other graphical representation, it is understood that the blocks, devices, systems, techniques, or methods described herein may be implemented as, as non-limiting examples, hardware, software, firmware, dedicated circuits or logic, general hardware or controllers or other computing devices, or some combination thereof.

[0195] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer executable instructions, such as those included in a program module, executed in a device on a target real or virtual processor to perform the above-referenced Figure 3-4 Method 300 or 400 described. In general, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functions of program modules can be combined or split between program modules as needed. The machine executable instructions of program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in both local and remote storage media.

[0196] The program code for executing the method of the present disclosure can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device so that when executed by the processor or controller, the program code enables the functions / operations specified in the flow chart and / or block diagram to be realized. The program code can be executed entirely on the machine, partially on the machine, as an independent software package, partially on the machine and partially on a remote machine or entirely on a remote machine or server.

[0197] In the context of the present disclosure, computer program codes or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform various processes and operations as described above. Examples of carriers include signals, computer readable media, etc.

[0198] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer readable medium may include, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared or semiconductor system, device or apparatus, or any suitable combination of the foregoing. More specific examples of computer readable storage media would include an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0199] In addition, although the operations are described in a particular order, this should not be construed as requiring that the operations be performed in the particular order or sequence order shown, or requiring that all of the operations shown be performed to obtain the desired results. In some cases, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these details should not be interpreted as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to a particular embodiment. Certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any appropriate sub-combination.

[0200] Although the disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Instead, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A method implemented at a first device, comprising: determining a first indicator of a first CSI pattern based on a current measurement of a channel between the first device and a second device; determining a second indicator for a second CSI mode based at least in part on previous CSI feedback; Selecting, based on the first indicator and the second indicator, a target CSI mode for current CSI feedback from the first CSI mode and the second CSI mode; as well as Receiving, from the second device, a switching factor for selecting the target CSI mode, wherein the selecting the target CSI mode comprises: adjusting the second indicator by the switching factor; In response to the adjusted second indicator being greater than the first indicator, selecting the first CSI mode as the target CSI mode; and In response to the adjusted second indicator being less than or equal to the first indicator, selecting the second CSI mode as the target CSI mode.

2. The method of claim 1 , wherein the determining the first indicator of the first CSI pattern comprises: generating a channel matrix for characterizing the channel based on the current measurement of the channel; determining a first base matrix from a set of vectors shared by the first device and the second device, the first base matrix indicating tap indices of at least a portion of taps of the channel matrix; determining a first transformation matrix based on the first base matrix and the channel matrix; determining an estimated channel matrix based on the first transformation matrix and the first base matrix; as well as The first indicator is determined based on a difference between the channel matrix and the estimated channel matrix.

3. The method of claim 2, wherein the determining the first indicator of the first CSI pattern comprises: generating a channel matrix for characterizing the channel based on the current measurement of the channel; determining a second base matrix based on the previous CSI feedback; determining a second transformation matrix based on the second base matrix and the channel matrix; determining an estimated channel matrix based on the second transform matrix and the second base matrix; as well as The second indicator is determined based on a difference between the channel matrix and the estimated channel matrix.

4. The method of claim 3, wherein the determining the second fundamental matrix comprises: obtaining one or more estimated channel vectors corresponding to one or more channel paths between the first device and the second device from the previous CSI feedback; determining a corresponding covariance matrix for each of the one or more channel paths based on the corresponding estimated channel vector; as well as The second base matrix is ​​determined based on a respective dominant eigenvector of a covariance matrix for each of the one or more channel paths.

5. The method of claim 3, wherein the determining the second base matrix comprises: obtaining one or more estimated channel vectors corresponding to one or more channel paths between the first device and the second device from the previous CSI feedback; as well as The second base matrix is ​​determined by normalizing each of the one or more estimated channel vectors for the corresponding channel path.

6. The method according to claim 3, further comprising: The current CSI feedback indicating the target CSI mode is sent to the second device.

7. A method according to claim 6, wherein if the target CSI mode is the first CSI mode, the current CSI feedback includes at least a bitmap of the first transform matrix and tap indices of at least a portion of the taps associated with the channel matrix, the bitmap indicating the positions and types of linear combination coefficients in the first transform matrix, and the size of the bitmap is associated with the number of the at least a portion of the taps, the number of receiving ports in the first device, and the number of transmitting ports in the second device.

8. A method according to claim 6, wherein if the target CSI mode is the second CSI mode, the current CSI feedback includes at least a bitmap of the second transformation matrix, the bitmap indicating the position and type of linear combination coefficients in the second transformation matrix, and the size of the bitmap is associated with the number of receiving ports in the first device and the number of transmitting ports or spatial beams in the second device. 9 . The method according to claim 1 , wherein the current CSI feedback comprises a CSI mode indicator for indicating the target CSI mode.

10. The method of claim 1, wherein the first CSI mode utilizes a discrete Fourier transform based operation, and / or the second CSI mode utilizes a Karolinen-Loewe transform based operation.

11. The method according to any one of claims 1-10, wherein the first device is a terminal device, and the second device is a network device.

12. A method implemented at a second device, comprising: determining a target CSI mode according to a first part of current CSI feedback for a channel between the first device and the second device, the target CSI mode being selected by the first device from a first CSI mode and a second CSI mode for current CSI feedback; receiving a second portion of the current CSI feedback based at least in part on the target CSI mode; as well as In response to determining that the target CSI mode is the first CSI mode, obtaining at least a bitmap of a first transform matrix and tap indices of at least a portion of taps associated with a channel matrix for characterizing the channel, wherein the first transform matrix is ​​determined based on at least a portion of the current CSI feedback, and The bitmap indicates the location and type of linear combination coefficients in the first transformation matrix, and the size of the bitmap is associated with the number of at least a portion of the taps, the number of receiving ports in the first device, and the number of transmitting ports in the second device.

13. The method according to claim 12, further comprising: determining a first base matrix based on the tap indices of at least a portion of the taps included in the second part of the current CSI feedback and a set of vectors shared by the first device and the second device; as well as The channel matrix is ​​reconstructed based at least in part on the first base matrix and the first transform matrix.

14. The method according to claim 12, further comprising: In response to determining that the target CSI mode is the second CSI mode, obtaining at least a bitmap of a second transform matrix, wherein the second transform matrix is ​​determined based on at least a portion of the current CSI feedback, and The bitmap indicates the positions and types of linear combination coefficients in the second transformation matrix, and the size of the bitmap is associated with the number of receiving ports in the first device and the number of transmitting ports in the second device.

15. The method according to claim 14, further comprising: determining a second base matrix based on previous CSI feedback; as well as The channel matrix is ​​reconstructed based on the second base matrix and the second transformation matrix.

16. The method of claim 12, wherein the first CSI mode utilizes a discrete Fourier transform based operation, and / or the second CSI mode utilizes a Karolinen-Loewe transform based operation.

17. The method according to any one of claims 12-16, wherein the first device is a terminal device, and the second device is a network device.

18. A first device, 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 first device to perform the method according to any one of claims 1 to 11.

19. A second device, 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 second device to perform the method according to any one of claims 12 to 17.

20. An apparatus for communication, comprising: means for determining a first indicator of a first CSI pattern based on a current measurement of a channel between the first device and the second device; means for determining a second indicator for a second CSI mode based on previous CSI feedback; means for selecting a target CSI mode for current CSI feedback from the first CSI mode and the second CSI mode based on the first indicator and the second indicator; as well as means for receiving, from the second device, a switching factor for selecting the target CSI pattern, The component for selecting the target CSI mode is further used for: adjusting the second indicator by the switching factor; In response to the adjusted second indicator being greater than the first indicator, selecting the first CSI mode as the target CSI mode; as well as In response to the adjusted second indicator being less than or equal to the first indicator, selecting the second CSI mode as the target CSI mode.

21. An apparatus for communication, comprising: means for determining a target CSI mode based on a first portion of current CSI feedback for a channel between the first device and the second device, the target CSI mode being selected from a first CSI mode and a second CSI mode for CSI feedback; means for receiving a second portion of the current CSI feedback based at least in part on the target CSI mode, the second portion of the current CSI feedback comprising at least one CSI parameter; as well as means for obtaining at least a bitmap of a first transform matrix and tap indices of at least a portion of taps associated with a channel matrix for characterizing the channel in response to determining that the target CSI mode is the first CSI mode, wherein the first transform matrix is ​​determined based on at least a portion of the current CSI feedback, and The bitmap indicates the location and type of linear combination coefficients in the first transformation matrix, and the size of the bitmap is associated with the number of at least a portion of the taps, the number of receiving ports in the first device, and the number of transmitting ports in the second device.

22. A computer-readable storage medium comprising program instructions stored thereon, wherein when the program instructions are executed by a processor of a device, the device is caused to perform the method of any one of claims 1-11 and 12-17.

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