Patent Description:
In 3GPP New Radio (NR) Rel-<NUM> and <NUM>, a compression mechanism has been introduced to reduce the overhead in reporting Channel State Information (CSI) from UEs to the Base Transceiver Station (BTS), which is required to operate Multi-User Multiple Input Multiple Output (MU-MIMO) in the downlink. The mechanism consists in two DFT-based operations in the spatial domain and in the frequency domain. These operations are applied to each layer for rank indicators (RI) from <NUM> to <NUM>. The CSI message may comprise a Channel Quality Indicator (CQI) and a Precoding Matrix Indicator (PMI). The CQI may be obtained from an estimate of the expected SINR after decoding of a codeword multiplexed across the reported spatial layers and PMI may comprise a set of complex-valued precoding weights that are needed to achieve that CQI. Both CQI and PMI parameters are reported per sub-band. The PMI is represented by a matrix for each reported layer, each containing as many column vectors as the number of sub-bands. The SD and FD compression operations are applied to these PMI matrices across their rows and columns respectively.

An important aspect of CSI signalling for MU-MIMO is the arrangement of the components of the compressed PMI in uplink control information (UCI) message. In a conventional way, this message may be organised in two parts, namely "UCI part <NUM>" and "UCI part <NUM>". The "UCI part <NUM>'' may comprise the CQI information and the parameters needed to determine the payload size of the "UCI part <NUM>". The "UCI part <NUM>" transmitted in the Physical Uplink Control Channel (PUCCH) may have a very short and fixed-size payload and may be encoded with very strong forward error correction code to guarantee error-free decoding. The "UCI part <NUM>" may comprise the bulk of compressed PMI and be transmitted in the Physical Uplink Shared Channel (PUSCH), hence it has the same error protection as data. 3GPP Draft R1-<NUM> relates to CSI Overhead reduction for Type II codebook up to rank <NUM> and discloses multiple schemes for linear combination coefficient quantization.

As used herein, the term "communication network" refers to a network that follows any suitable communication standards or protocols such as long term evolution (LTE), LTE-Advanced (LTE-A) and <NUM> NR, and employs any suitable communication technologies, including, for example, Multiple-Input Multiple-Output (MIMO), OFDM, time division multiplexing (TDM), frequency division multiplexing (FDM), code division multiplexing (CDM), Bluetooth, ZigBee, machine type communication (MTC), eMBB, mMTC and uRLLC technologies. For the purpose of discussion, In some example embodiments, the LTE network, the LTE-A network, the <NUM> NR network or any combination thereof is taken as an example of the communication network.

As used herein, the term "network device" refers to any suitable device at a network side of a communication network. The network device may include any suitable device in an access network of the communication network, for example, including a base station (BS), a relay, an access point (AP), a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a <NUM> or next generation NodeB (gNB), a Remote Radio Module (RRU), a radio header (RH), a remote radio head (RRH), a low power node such as a femto, a pico, and the like. For the purpose of discussion, in some example embodiments, the gNB is taken as an example of the network device.

The network device may also include any suitable device in a core network, for example, including multi-standard radio (MSR) radio equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), Multi-cell/multicast Coordination Entities (MCEs), Mobile Switching Centers (MSCs) and MMEs, Operation and Management (O&M) nodes, Operation Support System (OSS) nodes, Self-Organization Network (SON) nodes, positioning nodes, such as Enhanced Serving Mobile Position Centers (E-SMLCs), and/or Mobile Data Terminals (MDTs).

As used herein, the term "terminal device" refers to a device capable of, configured for, arranged for, and/or operable for communications with a network device or a further terminal device in a communication network. The communications may involve transmitting and/or receiving wireless signals using electromagnetic signals, radio waves, infrared signals, and/or other types of signals suitable for conveying information over air. In some example embodiments, the terminal device may be configured to transmit and/or receive information without direct human interaction. For example, the terminal device may transmit information to the network device on predetermined schedules, when triggered by an internal or external event, or in response to requests from the network side.

Examples of the terminal device include, but are not limited to, user equipment (UE) such as smart phones, wireless-enabled tablet computers, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), and/or wireless customer-premises equipment (CPE). For the purpose of discussion, in the following, some embodiments will be described with reference to UEs as examples of the terminal devices, and the terms "terminal device" and "user equipment" (UE) may be used interchangeably in the context of the present disclosure.

As used herein, the term "location server" may refer to a service function which provides the positioning of the target UE to a location client. The location server may communicate with the target UE to obtain the positioning measurement report from the target UE via a high layer signaling. The location service may also communicate with the network device to obtain information associated with the positioning of the target UE. The location server may be a component independent of the network device. As an option, the location server may be any function module or function entity embedded in the network device.

Corresponding to the term "location server", the term "location client", as used herein, may refer to an application or entity which requests the location of the target UE. The location client may transmit a location request to the location service and receives the positioning of the target UE from the location server. Also, the location client may be considered as the target UE itself.

As used herein, the term "cell" refers to an area covered by radio signals transmitted by a network device. The terminal device within the cell may be served by the network device and access the communication network via the network device.

As described above, the Precoding Matrix Indicator (PMI) is represented by a matrix for each reported layer, each containing as many column vectors as the number of sub-bands. The SD and FD compression operations are applied to these PMI matrices across their rows and columns respectively. As a result, the PMI for a layer is compressed in three component parts: an orthogonal basis set of DFT vectors for SD compression, an orthogonal basis set of DFT vectors for FD compression and a set of complex-valued linear combination (LC) coefficients. Therefore, both compression operations are linear projections on two orthogonal bases. When the two orthogonal bases are reported by indicating a subset from a DFT-based codebook, the LC coefficients are quantized in amplitude and phase by using scalar quantizers. Because only a subset of nonzero LC coefficients can be reported per layer to reduce overhead, both the location of the reported nonzero coefficients and their complex values are required to be reported. A bitmap per layer is used to report these locations.

Each PMI vector can be reported to the BTS based on a complex (amplitude and phase) scaling factor because this factor does not affect the precoder design. This property is used, for example, to apply appropriate phase shifts to the columns of the PMI matrix before FD compression to optimise the compression operation. This property also allows to apply a common scaling to all the LC coefficients before quantization, such that they are upper-bounded in amplitude by <NUM> and the quantization interval for amplitude becomes [<NUM>,<NUM>].

This common scaling of LC coefficients is applied independently to the coefficients of each layer and consists in the amplitude and phase of the "strongest" coefficient, i.e., the coefficient with the largest magnitude, for that layer. Since the strongest coefficient after normalization may equal to <NUM>, neither amplitude nor phase for the strongest coefficient are required to be reported. Instead, its location in the bitmap is signalled by means of a strongest coefficient indicator (SCI).

An important aspect of Channel State Information (CSI) signalling for Multi-User Multiple Input Multiple Output (MU-MIMO) is the arrangement of the components of the compressed PMI in uplink control information (UCI) message. In a conventional way, this message may be organised in two parts, namely "UCI part <NUM>" and "UCI part <NUM>". The "UCI part <NUM>" may comprise the CQI information and the parameters needed to determine the payload size of the "UCI part <NUM>". The "UCI part <NUM>" transmitted in the Physical Uplink Control Channel (PUCCH) may have a very short and fixed-size payload and may be encoded with very strong forward error correction code to guarantee error-free decoding. The "UCI part <NUM>" may comprise the bulk of compressed PMI and be transmitted in the Physical Uplink Shared Channel (PUSCH), hence it has the same error protection as data.

The information in the "UCI part <NUM>" that is used to determine the payload size of "UCI part <NUM>" can be arranged in two manners, namely (<NUM>) the number of the nonzero LC coefficients per each layer (the number of the layers equal to the maximum reported rank) and (<NUM>) the total number of nonzero LC coefficients for all reported layers and the RI indicator. The both ways allow determining the reported rank and therefore number of bitmaps in the "UCI part <NUM>". The number of the quantized coefficients is also reported in the "UCI part <NUM>", from which the payload size can be determined.

Note that some parameters needed for determining the size of the "UCI part <NUM>" and for correct PMI decoding are not reported in "UCI part <NUM>" because they are configured by the network. These are the parameters controlling the maximum overhead for CSI reporting, i.e., the size of the SD and FD bases and the maximum number of nonzero coefficients.

The manner (<NUM>), as mentioned above, is preferable, because the overhead for indicating the number of nonzero LC coefficients in the "UCI part <NUM>" may be significantly reduced. However, the manner (<NUM>) has a drawback of making the signalling of the SCI more inefficient. In fact, there is one SCI for each reported layer in part <NUM>, because the normalization of the LC coefficients is done independently per layer. Unless a restriction is introduced in the number of nonzero coefficients per layer, the SCI should contain <MAT> bits, with NNZ total number of nonzero coefficients.

Introducing such a restriction is not desirable either because the UE should select the LC coefficients to be reported to optimise the compression jointly across the reported layers for a given maximum budged of coefficients. Adding unnecessary constraints to this optimisation, for example by limiting the number of coefficients allowed to be reported per layer, may have a negative impact in performance.

Thus, the present disclosure proposes a signalling mechanism for the SCIs and the FD bases that reduces the overhead of the UCI message by exploiting a property of DFT-based frequency compression, namely that any phase ramp applied across the columns of the LC coefficient matrix before FD compression is transparent to the BTS and does not require signalling.

Embodiments of the present disclosure provide a solution for UCI design, so as to at least in part solve the above and other potential problems. Some example embodiments of the present disclosure will be described below with reference to the figures. However, those skilled in the art would readily appreciate that the detailed description given herein with respect to these figures is for explanatory purpose as the present disclosure extends beyond theses limited embodiments.

<FIG> shows an example communication network <NUM> in which implementations of the present disclosure can be implemented. The communication network <NUM> includes a network device <NUM> and terminal devices <NUM>-<NUM>, <NUM>-<NUM>. and <NUM>-N, which can be collectively or individually referred to as "terminal device(s)" <NUM>. The network <NUM> can provide one or more cells <NUM> to serve the terminal device <NUM>. It is to be understood that the number of network devices, terminal devices and/or cells is given for the purpose of illustration without suggesting any limitations to the present disclosure. The communication network <NUM> may include any suitable number of network devices, terminal devices and/or cells adapted for implementing implementations of the present disclosure.

In the communication network <NUM>, the network device <NUM> can communicate data and control information to the terminal device <NUM> and the terminal device <NUM> can also communication data and control information to the network device <NUM>. A link from the network device <NUM> to the terminal device <NUM> is referred to as a downlink (DL), while a link from the terminal device <NUM> to the network device <NUM> is referred to as an uplink (UL).

The communications in the network <NUM> may conform to any suitable standards 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), and the like. Furthermore, the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (<NUM>), the second generation (<NUM>), <NUM>, <NUM>, the third generation (<NUM>), the fourth generation (<NUM>), <NUM>, the fifth generation (<NUM>) communication protocols.

In order to obtain CSI of a communication channel between the network device <NUM> and the terminal device <NUM>, the network device <NUM> may transmit a Channel State Information-reference signal (CSI-RS) to the terminal device <NUM>. The terminal device <NUM> may receive the CSI-RS from the network device <NUM>, and obtain channel information by measuring the CSI-RS. The terminal device <NUM> may then determine the CSI of the communication channel based on the obtained channel information and a corresponding codebook. For example, the obtained channel information can be quantized into the CSI based on the corresponding codebook. The terminal device <NUM> may report the CSI to the network device <NUM>. The process for reporting the CSI is also called as "CSI feedback". The CSI may ensure reliability of the wireless communication between the network device <NUM> and the terminal device <NUM>. As mentioned above, for the CSI signalling, an important aspect is the arrangement of the components of the compressed PMI in uplink control information (UCI) message.

<FIG> shows a schematic diagram of a process <NUM> for the UCI design according to example embodiments of the present disclosure. For the purpose of discussion, the process <NUM> will be described with reference to <FIG>. The process <NUM> may involve the terminal device <NUM> and the network devices <NUM> as illustrated in <FIG>.

As shown in <FIG>, the terminal device <NUM> determines <NUM> a matrix characterizing a channel between the terminal device <NUM> and a network device <NUM>. The matrix may have spatial components and frequency components and corresponding to a bitmap indicating a set of non-zero linear combination coefficients for quantizing the channel.

In some example embodiments, the terminal device <NUM> may receive the downlink control information received from the network device <NUM> and obtain a resource indication associate with the spatial components and the frequency components, which is known for both terminal device and the network device. The terminal device <NUM> may determine the matrix based on the downlink control information and the resource indication.

Such matrix and the corresponding bitmap may be shown in <FIG>, respectively. As shown in <FIG>, the matrix has spatial components in the spatial domain <NUM> and frequency components in the frequency domain <NUM>. Such matrix shown in <FIG> may be referred to as a LC coefficient matrix.

As mention above, the matrix may be obtained by applying the compression to a PMI matrix representing the collection of precoding vectors for a given spatial layer for all the configured sub-bands, which may be indicated in the downlink control information received from the network device <NUM>. Given the PMI matrix W of size <NUM>N<NUM>N<NUM> × N<NUM>, where N<NUM> × N<NUM> is the number of antenna ports for each polarisation in the transmit two-dimensional cross-polarised antenna array and N<NUM> is the number of configured PMI sub-bands. For rank indicators (RI) larger than one, there is one such PMI matrix for each of the RI spatial layers. The compression operations on PMI matrix W are linear and can be represented by the following equation: <MAT> where the column vectors of matrix W<NUM> are the components of the SD orthogonal basis of size <NUM>, the columns of Wf form the FD orthogonal basis of size M, and W̃<NUM> is a <NUM>L × M matrix of complex-valued LC coefficients. The matrix W̃<NUM> may refer to the matrix shown in <FIG>. To further reduce the signalling overhead, only a subset of the 2LM LC coefficients are reported, and the remaining ones are set to zero. This group of reported LC coefficients are referred to as non-zero (NZ) coefficients. The NZ coefficient may refer to the cells in <FIG> which are not equal to zero, for example, the cell <NUM>.

Thus, the PMI report for a layer may consists of two indicators for the SD and FD basis subset selection, respectively and a <NUM>L × M bitmap indicating the location of the KNZ nonzero coefficients in the W̃<NUM> matrix. The bitmap corresponding to the W̃<NUM> matrix may be shown in <FIG>. As shown in <FIG>, the row and column of the bitmap may corresponding to the spatial components and the frequency components, for example, the <NUM>th frequency component in the frequency domain <NUM> corresponds to the <NUM>th column of the bitmap.

There is the target coefficient in the KNZ nonzero coefficients in the W̃<NUM> matrix. The target coefficient may be referred to as the maximum coefficient of the non-zero coefficients, i.e. the strongest coefficient. In order to reducing the overhead for reporting the indication for strongest coefficient, the terminal device <NUM> determines shifting operation for the frequency components of the matrix, such that the strongest coefficient is located in a frequency component with a predetermined index.

In some example embodiments, the terminal device <NUM> may determine indices of the frequency components and perform modulo operation for the frequency components in the matrix based on the indices of the frequency components, the number of the frequency components in a predefined set of frequency components, the predetermined index and a reference index of the frequency component. The reference index may indicate frequency component associated with the target coefficient before shifting. The terminal device <NUM> may perform the shifting operation based on result of the modulo operation.

For example, N<NUM> is the number of frequency components, M < N<NUM> the size of the frequency domain basis formed by frequency components with indices m<NUM>, m<NUM>,. , mM-<NUM>, and mimax is the index of the frequency component with the strongest coefficient. For example, assuming that the predefined index value for the component mimax is <NUM>. The terminal device <NUM> may perform the shifting operation based on the following equation: <MAT>.

Then, the terminal device <NUM> determines an indication for the strongest coefficient, i.e. the SCI, based on the the spatial components where the strongest coefficient located. The SCI may indicate the spatial component associated with the target coefficient in the matrix.

The terminal device <NUM> further generates another indication for indicating a frequency range associated with a subset of the frequency components based on the based on the predetermined index and the frequency components. That is, the subset of the frequency components excludes the frequency component with the predetermined index.

In some example embodiments, the terminal device <NUM> may determine, from the frequency components, a target frequency component associated with the predetermined index and select from the frequency components, the subset of the frequency components excluding the target frequency component. The terminal device <NUM> may determine the indices of the subset of the frequency components and generate the indication for indicating the frequency range based on the indices of the subset of the frequency component.

Referring back to the assumption related to the equation (<NUM>), the terminal device <NUM> may report the subset of the frequency components of size M - <NUM>, without the "<NUM>th" frequency component as below: <MAT>.

After determining the SCI and the indication associated with the frequency range, the terminal device <NUM> may transmit <NUM> the uplink control information comprising both of the indications to the network device <NUM>.

It should be understood that the UCI may comprise other necessary message for reporting the related parameters for estimating the channel state.

In some example embodiments, the UCI may also comprise a bitmap corresponding to the matrix of the LC coefficient. A bitmap may be determined based on the matrix before the shifting operation. As mentioned above, such bitmap may indicate the locations of the NZ coefficient in the matrix. After the shifting operation of the matrix, the bitmap may also be updated based on the predetermined index.

In some example embodiments, the terminal device <NUM> may determine a corresponding relationship between the predetermined index and each index of the indices of the frequency components based on the indices of the frequency components and the predetermined index and update the bitmap based on the corresponding relationship.

In some example embodiments, the terminal device <NUM> transmits the uplink control information also comprising the updated bitmap.

With reference to <FIG> and <FIG>, the shifting operation may be shown clearly. As mention above the matrix of <FIG> may have a size of <NUM>*M, there are a set of NZ coefficients in the matrix and <FIG> shows a bitmap corresponding to the matrix of <FIG>. As shown in <FIG>, assuming the strongest coefficient <NUM> is located in the <NUM>th frequency component <NUM>. For example, the terminal device <NUM> may shift the matrix such that the strongest coefficient is located in the <NUM>th frequency component. The shifted matrix may be shown in <FIG>. The strongest coefficient <NUM> is located in the <NUM>th frequency component <NUM>. Correspondingly, the bitmap shown in <FIG> may be updated to be the bitmap shown in <FIG>.

If we assume, without loss of generality, a row-wise reading order of the bitmap in <FIG>, the strongest coefficient is the third NZ coefficient, hence, without the proposal of the present disclosure, it would be indicated with <MAT> bits: SCI=<NUM> or <NUM> (<NUM>-bit binary representation of <NUM>). The value KNZ = <NUM> for this layer should also be reported in "UCI part <NUM>".

According to the solution of the present disclosure, if the predetermined index is "0th", the terminal device <NUM> may apply the shift operation to the frequency components of one position to the left, in the example of <FIG>. For example, let us assume the frequency
components are {m<NUM>, m<NUM>,. , mM-<NUM>} = {<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>} with the index of the FD component with the strongest coefficient given by mimax = <NUM>. After the circular shift and re-ordering the FD basis subset is given by {<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>}. On the other hand, the SCI is indicated with <MAT> bits reporting the SD component index, which in the example is: SCI=<NUM> or <NUM> (<NUM>-bit binary representation of <NUM>).

Referring <FIG> again, the network device <NUM> receives the uplink control information from the terminal device <NUM> and determines state information of the channel based on the uplink control information.

In some example embodiments, the network device <NUM> may determine the matrix based on the uplink control information and determine the state information based on the matrix. As mentioned above, the matrix may be obtained by apply the compression of the PMI matrix. The network device <NUM> needs to reconstruct the PMI matrix based on the matrix. According to the UCI, the network device <NUM> may determine the subset of the frequency components excluding the target frequency component and the network device <NUM> may reconstruct the PMI by adding the target frequency component to the subset of the frequency components.

In this way, a new solution for designing the UCI may reduce the overhead for reporting the parameters in the "UCI part <NUM>" and "UCI part <NUM>".

In the following, the principle for circular shift will be explained. As mention above, any circular shift applied to the frequency components is equivalent to a multiplication of the columns of the PMI by a phase ramp before applying frequency compression. Such phase ramp operation performed at the terminal device <NUM> does not need to be reported to the network device <NUM> because it is transparent to the precoder design.

It is well known that a phase rotation across the columns of a precoding matrix W does not affect the precoder performance, hence the network device <NUM> may reconstruct W up to a phase adjustment per column without affecting performance. This is true for any type of precoder design. It will be shown that phase adjustments applied across the columns of matrix W<NUM> before frequency domain compression do not need to be reported to the network device <NUM>. It will also be pointed out that the choice of these phases is an important degree of freedom that a terminal device <NUM> can exploit to improve frequency compression, i.e. reduce the reconstruction error at the network device <NUM>.

At first, considering an ideal case for frequency compression, without basis subset selection, i.e. assuming that M = N<NUM>, and with reporting of all <NUM>LN<NUM> unquantized frequency domain coefficients. Note that this is just a hypothetical case as there is no actual compression gain in the frequency domain. Assuming that a terminal device <NUM> applies phase adjustments on the columns of W<NUM> before the DFT processing across the sub-bands and we indicate with R a diagonal matrix of arbitrary phase rotations: <MAT>.

If the network device <NUM> knows R, the precoder W is reconstructed as: <MAT>
whereas, if the network device <NUM> is unaware of R, the reconstruction yields: <MAT>.

In this ideal case, we observe that <NUM>) the difference between the reconstruction (<NUM>) and (<NUM>) is just a phase rotation across the precoder's columns, i.e. <MAT>
and <NUM>) assuming perfect reporting of the <NUM>L × N<NUM> linear combination matrix W<NUM>, applying the phase rotations in (<NUM>) is irrelevant.

Considering the realistic case of basis subset selection with M ≤ N<NUM> and quantization of the linear combination coefficients and say W̃'<NUM> is the <NUM>L × N<NUM> matrix of FD coefficients known at the network device <NUM>. Note that only up to K<NUM> coefficients of W̃'<NUM> are nonzero. Quantisation error also affects the nonzero coefficients. Introducing the error matrix between the realistic and ideal matrix of linear combination coefficients: <MAT>.

Such that W̃'<NUM> can be expressed, in a very general case, as: <MAT>.

If the network device <NUM> knows the phase shifts R, the precoder W' is reconstructed, with error, as: <MAT>.

If the network device <NUM> is unaware of R, the precoder reconstruction yields: <MAT>.

By comparing (<NUM>) and(<NUM>), it will have: <MAT> i.e., the difference between the two reconstructions, with and without reporting of R, is a phase rotation applied to the precoder's columns, which does not affect the precoder's performance. However, unlike in the ideal case, applying appropriate phase rotations at the terminal device does make a difference in terms of reconstruction error. In fact, the terminal device may optimise the selection of the phase rotations R such that the reconstruction error E is minimised according to some metric, even if the network device is unaware of these phase adjustments.

Note that both results (<NUM>) and (<NUM>) hold when Wf is <NUM> × M, instead of <NUM> × N<NUM>, but the expressions for W' and W'(R) are more complicated because <MAT> is no longer the identity matrix.

In conclusion, when applying frequency domain compression, optimisation of the phase adjustments R can be used by the terminal device to improve the PMI accuracy. However, these adjustments do not need to be communicated to the network device to achieve this gain.

Note that several operations can be expressed by these phase rotations. An oversampled DFT codebook can be described as the union of O<NUM> circularly shifted versions of a critically sampled codebook, where the minimum shift is fractional. Accordingly, we can express the selection of one of the O<NUM> orthogonal groups of size N<NUM> by using notation (<NUM>) with R given by the phase ramp: <MAT> and k ∈ [<NUM>,. , O<NUM> - <NUM>]. Similarly, a circular shift of the N<NUM> frequency domain candidate components can be obtained by applying a phase ramp across the columns of W<NUM> , in the original domain, with minimum shift multiple of O<NUM>. For example, a circular shift that moves FD component of index n to position '<NUM>' can be expressed by (<NUM>) with R given by the phase ramp: <MAT> and n ∈ [<NUM>,. , N<NUM> - <NUM>]. Finally, oversampling and circular shifts can also be combined with phase adjustments on the columns of W<NUM> to ensure smooth phase transitions along its rows before applying frequency domain compression and avoid 'phase jumps'. Denoting the diagonal matrix of these phase adjustments as Rφ: <MAT> with φn ∈ [<NUM>,2π). In general, a terminal device can apply a combination of these three operations (oversampling, circular shifts, phase adjustments) by performing a set of phase rotations on the columns of W<NUM>, as described in(<NUM>), with a rotation matrix given by: <MAT>.

More details of the example embodiments in accordance with the present disclosure will be described with reference to <FIG>.

<FIG> shows a flowchart of an example method <NUM> for UCI design according to some example embodiments of the present disclosure. The method <NUM> can be implemented at the terminal device <NUM> as shown in <FIG>. For the purpose of discussion, the method <NUM> will be described with reference to <FIG>.

At <NUM>, the terminal device <NUM> determines a matrix comprising a set of non-zero linear combination coefficients for quantizing a channel between the terminal device and a network device, the matrix having spatial components and frequency components.

In some example embodiments, the terminal device <NUM> may receive downlink control information received from the network device and obtain a resource indication associate with the spatial components and the frequency components. The terminal device <NUM> may also determine the matrix based on the downlink control information and the resource indication.

At <NUM>, the terminal device <NUM> shifts the frequency components of the matrix circularly, such that a target coefficient of the set of non-zero linear combination coefficients is located in a frequency component with a predetermined index of the frequency components in a shifted matrix.

In some example embodiments, the terminal device <NUM> may determine indices of the frequency components. The terminal device <NUM> may also determine a reference index from the indices of the frequency components, the reference index indicating a frequency component associated with the target coefficient in the matrix and shift the frequency components based on the indices of the frequency components, the predetermined index and the reference index.

At <NUM>, the terminal device <NUM> generates a first indication indicating the spatial component associated with the target coefficient in the matrix.

In some example embodiments, the terminal device <NUM> may determine, as the target coefficient, a maximum coefficient from the set of non-zero linear combination coefficients and generate the first indication based on the index of the spatial component associated with the target coefficient in the matrix.

At <NUM>, the terminal device <NUM> transmits, to the network device <NUM>, uplink control information comprising the first indication.

In some example embodiments, the terminal device <NUM> may determine, based on the shifted matrix, a bitmap indicating locations of the non-zero linear combination coefficients in the shifted matrix; and transmit the uplink control information comprising the bitmap.

In some example embodiments, the terminal device <NUM> may generate, based on the predetermined index and the frequency components, a second indication indicating a frequency range associated with a subset of the frequency components and transmit the uplink control information comprising the second indication.

In some example embodiments, the terminal device <NUM> may determine, from the frequency components, a target frequency component associated with the predetermined index and select, from the frequency components, the subset of the frequency components excluding the target frequency component. The terminal device <NUM> may also determine indices of the subset of the frequency components after the shifting and generate the second indication based on the indices of the subset of the frequency component.

<FIG> shows a flowchart of an example method <NUM> for UCI design according to some example embodiments of the present disclosure. The method <NUM> can be implemented at the network device <NUM> as shown in <FIG>. For the purpose of discussion, the method <NUM> will be described with reference to <FIG>.

At <NUM>, the network device <NUM> receives at a network device and from a terminal device <NUM>, uplink control information comprising a first indication, the first indication indicating spatial components associated with a target coefficient in a matrix comprising a set of non-zero linear combination coefficients for quantizing a channel between the terminal device and the network device, the matrix having the spatial components and frequency components.

At <NUM>, the network device <NUM> determines state information of the channel based on the uplink control information.

In some example embodiments, the network device <NUM> may determine the matrix based on the uplink control information and determine the state information based on the matrix.

In some example embodiments, the network device <NUM> may receive uplink control information comprising the uplink control information comprising the bitmap indicating locations of the non-zero linear combination coefficients in a shifted matrix obtained by shifting the frequency components of the matrix circularly.

In some example embodiments, the network device <NUM> may receive uplink control information comprising the second indication indicating a frequency range associated with a subset of the frequency components.

In some example embodiments, an apparatus capable of performing the method <NUM> (for example, implemented at the terminal device <NUM>) may comprise means for performing the respective steps of the method <NUM>. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises means for determining, at a terminal device, a matrix comprising a set of non-zero linear combination coefficients for quantizing a channel between the terminal device and a network device, the matrix having spatial components and frequency components; means for shifting the frequency components of the matrix circularly, such that a target coefficient of the set of non-zero linear combination coefficients is located in a frequency component with a predetermined index of the frequency components in a shifted matrix; means for generating a first indication indicating the spatial component associated with the target coefficient in the matrix; and means for transmitting, to the network device, uplink control information comprising the first indication.

In some example embodiments, an apparatus capable of performing the method <NUM> (for example, implemented at the network device <NUM>) may comprise means for performing the respective steps of the method <NUM>. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises means for receiving, at a network device and from a terminal device, uplink control information comprising a first indication, the first indication indicating spatial components associated with a target coefficient in a matrix comprising a set of non-zero linear combination coefficients for quantizing a channel between the terminal device and the network device, the matrix having the spatial components and frequency components and means for determining state information of the channel based on the uplink control information.

<FIG> is a simplified block diagram of a device <NUM> that is suitable for implementing embodiments of the present disclosure. The device <NUM> may be provided to implement the communication device, for example the terminal device <NUM> and the network device <NUM> as shown in <FIG>. As shown, the device <NUM> includes one or more processors <NUM>, one or more memories <NUM> coupled to the processor <NUM>, and one or more transmitters and/or receivers (TX/RX) <NUM> coupled to the processor <NUM>.

The TX/RX <NUM> is for bidirectional communications. The TX/RX <NUM> has at least one antenna to facilitate communication.

In some embodiments, the program <NUM> may be tangibly contained in a computer readable medium which may be included in the device <NUM> (such as in the memory <NUM>) or other storage devices that are accessible by the device <NUM>.

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 program modules, being executed in a device on a target real or virtual processor, to carry out the methods <NUM> and <NUM> as described above with reference to <FIG>. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Claim 1:
A method, comprising:
Determining (<NUM>), at a first device (<NUM>), a <NUM> × M matrix W̃<NUM> comprising linear combination coefficients for a pre-coder matrix indicator, PMI, matrix, wherein the matrix W̃<NUM> has <NUM> spatial components and M frequency components;
determining a shifted matrix by shifting (<NUM>) the frequency components of matrix W̃<NUM> circularly, such that a maximum coefficient of matrix W̃<NUM> is located in a frequency component with a predetermined index;
generating (<NUM>) a strongest coefficient indicator with <MAT> bits, indicating the index of the spatial component associated with the maximum coefficient of matrix W̃<NUM>; and
transmitting (<NUM>), to a second device (<NUM>), uplink control information comprising the strongest coefficient indicator and locations and complex values of non-zero linear combination coefficients of the shifted matrix, wherein the non-zero linear combination coefficients are scaled by the maximum coefficient, wherein the transmitted complex values of the non-zero linear
combination coefficients exclude the maximum coefficient.