CN103117787B - Self-adaptive bit allocation method and device in a kind of collaboration multiaerial system - Google Patents

Abstract

The invention provides a kind of self-adaptive bit allocation method and device cooperateed with multiaerial system, methods described includes extracting the Delay of data-signal and the receiving power of interference signal and each channel according to channel estimation；Calculate the Optimal Feedback bit number distributed on the premise of total number of bits of feedback is fixed for data channel and each interference channel respectively according to the Delay of signal reception power and each channel, and the rate loss that channel information nonideality is caused carries out minimum processing；The size of code book is determined according to Optimal Feedback bit number, and channel condition information and transmission after corresponding codeword quantizations are chosen from code book according to minimum chordal distance criterion using ideal communication channel information；Receive and ZF pre-coding matrix is generated according to the interference channel information of the quantization.The present invention carries out ZF pre-encode operation by base station using the non-ideal communication channel information obtained, suppresses the multi-user interference in this cell and the inter-cell interference to adjacent cell.

Description

Self-adaptive bit allocation method and device in cooperative multi-antenna system

Technical Field

The invention relates to a self-adaptive bit allocation method and a device in a cooperative multi-antenna system, belonging to the technical field of wireless communication.

Background

In a wireless communication system, inter-cell interference is an important factor that causes degradation of communication quality for cell-edge users. For the user at the center of the cell, the distance from the base station is relatively short, and the interference signal distance of the outer cell is relatively long, the signal-to-interference-and-noise ratio is relatively large. For the users at the edge of the cell, because the interference to the users occupying the same bandwidth resource by the adjacent cell is larger, and the distance from the adjacent cell to the base station is longer, the signal to interference plus noise ratio of the users is relatively smaller, so that although the throughput of the whole cell is higher, the service quality of the users at the edge of the cell is poorer, and the throughput is lower. Therefore, an inter-cell interference suppression technique is very important in a wireless communication system.

A conventional method of reducing inter-cell interference is a frequency reuse technique. When the cell cluster is larger, i.e. the frequency reuse factor is larger, the inter-cell interference can be effectively reduced, but at the same time the spectrum efficiency is also reduced accordingly. Currently, OFDM (Orthogonal Frequency Division Multiplexing) has become an important technology for next-generation wireless communication systems. In the OFDM system, in order to increase the system capacity, the frequency reuse factor should be close to 1, where the spectrum efficiency is high, but the inter-cell interference is very serious. Therefore, solving the problem of inter-cell interference is crucial to improving the overall performance of the wireless communication system.

In a frequency division multiplexing-based multi-cell cooperative communication system, a user can estimate complete interference channel information through a channel estimation technology and feeds the information back to a cell base station through a feedback link. The base station of the cell transmits the interference channel information to the base station which causes interference to the users of the cell through an X2 interface. The base station of the interference cell performs zero forcing precoding operation by using the acquired information of the interference channel, so that the interference to the interference cell can be completely eliminated. However, in the codebook-based limited feedback system, CSI (Channel state Information) fed back to the base station by the user is quantized and has Channel delay, which is not ideal CSI, so zero-forcing precoding still cannot completely eliminate interference, which causes residual interference, and the residual interference may cause a decrease in user transmission rate.

Disclosure of Invention

The embodiment of the invention provides a self-adaptive bit allocation method and a self-adaptive bit allocation device in a cooperative multi-antenna system, which can solve the problem of inter-cell interference by obtaining the maximum transmission rate by using fixed feedback overhead. Therefore, the invention provides the following technical scheme:

an adaptive bit allocation method in a cooperative multi-antenna system, comprising the steps of:

extracting data channel information of the cell, interference channel information of an adjacent cell, receiving power of a data signal and an interference signal and time delay information of each channel according to channel estimation;

respectively calculating the optimal feedback bit number distributed to the data channel and each interference channel on the premise that the total feedback bit number is fixed according to the signal receiving power and the time delay information of each channel, and minimizing the rate loss caused by the non-ideal state of the channel information to obtain ideal channel information;

determining the size of a codebook according to the optimal feedback bit number, selecting corresponding channel state information after codeword quantization from the codebook according to a minimum chordal distance criterion by using the ideal channel information, and feeding back the channel state information to a service base station through a feedback link with time delay;

and receiving the quantized channel state information through an X2 interface with time delay, and generating a zero-forcing precoding matrix according to the quantized interference channel information.

An adaptive bit allocation apparatus in a cooperative multi-antenna system, comprising:

the receiving unit is used for extracting the data channel information of the cell, the interference channel information of the adjacent cell, the receiving power of the data signal and the interference signal and the time delay information of each channel according to the channel estimation;

a feedback calculation unit, configured to calculate optimal feedback bit numbers allocated to the data channels and the interference channels on the premise that a total feedback bit number is fixed according to the signal receiving power and the delay information of each channel, and minimize a rate loss caused by a non-ideal state of channel information to obtain ideal channel information;

the quantization calculation unit is used for determining the size of a codebook according to the optimal feedback bit number, selecting corresponding channel state information after codeword quantization from the codebook according to a minimum chordal distance criterion by utilizing the ideal channel information, and feeding back index information corresponding to the channel state information to a service base station through a feedback link with time delay;

and the base station precoding unit is used for receiving the quantized channel state information through an X2 interface with time delay and generating a zero-forcing precoding matrix according to the quantized interference channel information.

The invention carries out zero forcing precoding operation by utilizing the acquired non-ideal channel information through the base station, thereby inhibiting multi-user interference in the cell and interference between cells to adjacent cells.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic flowchart of an adaptive bit allocation method in a cooperative multi-antenna system according to the present invention;

fig. 2 is a system block diagram of cooperative MIMO in an embodiment of the present invention;

fig. 3 is a schematic structural diagram of an adaptive bit allocation apparatus in a cooperative multi-antenna system according to the present invention.

Detailed Description

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.

As shown in fig. 1, an embodiment of the present invention provides an adaptive bit allocation method in a cooperative multiple antenna system, including the following steps:

step 1, extracting data channel information of a cell, interference channel information of an adjacent cell, receiving power of a data signal and an interference signal and time delay information of each channel according to channel estimation;

step 2, respectively calculating the optimal feedback bit number distributed for the data channel and each interference channel on the premise that the total feedback bit number is fixed according to the signal receiving power and the time delay information of each channel, and minimizing the rate loss caused by the non-ideal state of the channel information to obtain ideal channel information;

step 3, determining the size of a codebook according to the optimal feedback bit number, selecting corresponding channel state information after codeword quantization from the codebook according to a minimum chordal distance criterion by utilizing the ideal channel information, and feeding back the channel state information to a service base station through a feedback link with time delay;

and step 4, receiving the quantized channel state information through an X2 interface with time delay, and generating a zero-forcing pre-coding matrix according to the quantized interference channel information.

In this embodiment, it is assumed that in the multi-cell-coordinated multiple-input multiple-output system, M neighboring cells are located around one reference cell, and a base station in the reference cell schedules K users to perform data transmission simultaneously. N is respectively configured for each base station and each user in the system_TAnd n_RAnd an antenna. When the system frequency reuse factor is 1, each user will experience two kinds of interference: 1. inter-user interference from the own cell, and inter-cell interference from the neighboring cell 2. The interference base received by the kth user in the reference cell from the serving base station and the mth (M is more than or equal to 1 and less than or equal to M)The signal power of the station is P_kAndwhereinIs a power coefficient, i.e. the power of the data signal of the local cell is stronger than the power of the interference signal of the interfering cell.The value of (c) depends on the channel large scale fading, including path loss and shadow fading. Receiving signal of k user of reference cell at time point nCan be written as:

whereinAndchannel matrices for the reference cell and the mth interfering cell to user k, respectively.For transmitting data vectors, the maximum transmit power limit is satisfied: a unitary matrix is precoded diagonally for a block. z is a radical of_k[n]Denotes the obedience distribution as CN (0, σ)²) Complex gaussian noise vector of。

In this embodiment, H_k[n]And G_k，m[n]Respectively, with a codebook W based on Random Vector Quantization (RVQ)_kAnd W_k,mTo be quantized. The codebook used by each user is generated in advance online, and the whole content of the codebook is acquired in advance by both the transmitting end and the receiving end. Codebook W_kAnd W_k,mRespectively has the size ofAndnamely, it is Each element in the codebook is a randomly generated semi-unitary matrix. Suppose the total feedback bandwidth per user is B_totBit, wherein B_kAnd B_k,mBit-wise quantization of H_k[n]And G_k，m[n]. The user selects the corresponding code word from the codebook as the quantized channel matrixAndthe selection method is based on the minimum chord distance criterion:

（2）

channel delays due to information interaction of the feedback and X2 interfaces can also result in a loss of system performance. In this embodiment, a time-varying block fading channel model is considered, i.e., the channel is fixed in one symbol interval and the channel responses between adjacent symbols are correlated. The channel correlation can be expressed as:

H_k[n]＝η_kH_k[n-D_k]+E_k[n](3)

G_k，m[n]＝η_k,mG_k，m[n-D_k,m]+E_k，m[n]

wherein E_k[n]And E_k，m[n]Is a channel error matrix and is associated with H_k[n-D_k]And G_k，m[n-D_k,m]Are relatively independent. D_kAnd D_k,mRespectively the number of sampling points of the channel delay. E_k[n]And E_k，m[n]Subject to distribution of elements in (1)Andand respectively satisfy Correlation coefficient η_kAnd η_k,mDetermined by the clarca autocorrelation model:

η_k＝J₀(2πf_dD_kT_s) (4)

η_k,m＝J₀(2πf_dD_k,mT_s)

wherein, J₀(. h) is a Bessel function of order 0, f_dFor Doppler shift, T_sIs a symbol interval.

When the transmitting end can obtain ideal channel state information without time delay, the method of cooperative block diagonal precoding based on zero forcing can completely eliminate the inter-cell interference and the inter-user interference, and the precoding matrix of the method meets the following limitations:

H_j[n]T_k[n]＝0,forj＝1,2…Kand j≠k (5)

G_k，m[n]T_k[n]＝0,for1≤m≤M

wherein the first equation in equation (5) represents a zero-forcing constraint for intra-cell interference and the second equation represents a zero-forcing constraint for inter-cell interference. Therefore, the precoding matrix of the k-th user in the cell should be includedIn the null space of (a).Can be defined asWhereinAndaggregation matrices for multiuser interference channels and inter-cell interference channels, respectively:

(6)

to pairPerforming standard singular value decomposition to obtain

Make up ofA set of orthonormal bases of the right null space. Order toThe restriction in the expression (5) can be satisfied. In the present embodiment, n is the number of n_T≥(K-1)n_R+Mn_RTo meet the constraints of antenna dimensions. Dynamic clustering cooperation and multi-user scheduling algorithms can be employed to reduce the values of K and M. When the transmitting end has ideal channel state information, the block diagonal precoding method can completely delete multi-user interference and inter-cell interference, and the user average transmission rate expression is as follows:

considering that in an actual system, a transmitting end cannot acquire ideal channel state information without time delay, and a base station can only acquire quantized and time-delayed data channel information at the nth timeAnd interference channel information. Using block diagonal precoding matricesMutual interference cannot be completely eliminated, and the following limitations can only be satisfied:

(9)

the average transmission rate of users under the non-ideal channel is expressed as:

wherein R is_k[n]The covariance matrix for interference plus noise for the kth user is expressed as:

(11)

the interference in the formula (10) cannot be completely removed due to the existence of non-ideal channel information, i.e. the interference is not completely removedAndthus, the residual interference may deteriorate system performance.

In the specific embodiment, a closed expression based on the difference between the user transmission rate when the limited feedback and the channel delay exist and the user transmission rate under the ideal channel condition is firstly deduced, and a self-adaptive bit allocation algorithm is provided based on the closed expression. Wherein, the closed expression of the rate loss caused by the non-ideal channel state information is derived as follows:

(12)

wherein R is neglected in the formula (a)_k[n]Partial positive definite term of (2). T is_k[n]Andis distributed isotropically and is reacted with H_k[n]Are independent of each other, thereforeAndthe expectation is equal. (b) The formula is according to the Jansen inequality. The derivation of equation (c) is as follows:

for item S1:

(13)

wherein (d) is according to equation (3) and E_k[n]And H_k[nD_k]Are independently distributed. (e) Is according to H_k[n-D_k]The eigenvalue decomposition expression of (a):whereinMake up of H_k[nD_k]Λ in a subspace spanned by the column vectors_kIs a diagonal matrix whose diagonal elements areN of (A) to (B)_RNon-zero, descending order of eigenvalues. (e) Formula (II) is according to E_k[n]Is a complex Gaussian matrix and T_j[n]Is a unitary matrix, thus E_k[n]T_j[n]Also obeys for each elementA gaussian matrix of distribution. Matrix arrayCan be decomposed as follows:

whereinIs a set of isotropically distributed orthonormal bases, formed by stretchingN in the left null space of_RAnd (4) dimensional plane. C_kIs n_R×n_RAnd an upper triangular matrix, the diagonal elements of which are positive values and satisfy:and, S_kAnd C_kAre independent of each other. The following can be obtained from the equation (14):

(15) the last equation in the equation is based on S_kAnd T_j[n]Is isotropically distributed inAnd both are independent of each other, thusFor the matrix the random variable obedience parameter is n_RAnd n_T-2n_RBeta distribution of (i.e.According to the nature of the (14) matrix decomposition, there are Wherein phi_kFor quantization errors can be approximately equal to:

wherein T is n_R(n_T-n_R)，Thus, the formula (f) is obtained.

The derivation of S2 is similar to S1 as follows:

(17)

whereinComposition G_k[n-D_k,m]The column vector of (a) opens up a set of orthonormal bases in space, Λ_k，mIs a diagonal matrix whose diagonal elements areN of (A) to (B)_RNon-zero, descending order of eigenvalues. Phi_k，mTo quantify the error:

finally, the closed expression of the rate loss caused by the finite feedback and the channel delay is obtained as follows:

from equation (19), the rate loss is mainly due to two factors: residual multi-user interference and inter-cell interference. One key problem is when the total number of feedback bits B for each user_totAt fixed time, to minimize rate loss, how many feedback bits number B should be allocated for the data channel_k(ii) a And how many bits B should be allocated for the interference channel_k，m. The present embodiment will next propose a new optimal bit allocation scheme to minimize the rate loss of equation (19).

According to equation (19), noting that the logarithmic function is a monotonically increasing function, neglecting the constant term, the objective function can be obtained as follows:

(20)

wherein,

(20) the formula is a convex function and can be solved by a convex optimization method. The lagrange function can be written as:

from equation (21), the first-order optimal KKT condition can be obtained as follows:

solving the equation in equation (22) yields the optimal solution as follows:

whereinFrom the formula (23)With followingIs increased. That is, when the power of the data signal is stronger or the delay of the data channel is smaller, the system allocates more feedback bits to quantize the data channel. On the contrary, when the interference channel is strong and the delay is small, more feedback bits are allocated to the quantized interference channel. In other words, the algorithm proposed in this embodiment is adaptive to allocate more feedback bits for channels with stronger power and smaller delay; less feedback bits are allocated for channels with weaker power and larger delay to minimize rate loss.

The following describes in detail an adaptive bit allocation method in a cooperative multi-antenna system according to a specific embodiment. In the block diagram of the multi-antenna system shown in fig. 2, each user not only receives the data channel of the local cell, but also is interfered by signals of neighboring cells, and the user acquires channel state information of the data channel and the interference channel by using channel estimation, and feeds back the quantized information to the serving base station. The serving base station then transfers the interfering channel information to the interfering cell base station via the X2 interface.

The base station broadcasts the broadcast channel periodically. The user estimates the channel information of the data channel of the cell and the interference channel of the adjacent cell by using the channel estimation, and the related information of the signal power and the time delay. And (4) respectively calculating the optimal feedback bit number distributed by the data channel and each interference channel by the user according to the formula (22) by utilizing the information of the signal power and the time delay. Determining the optimum number of feedback bits, i.e. determining the size of the codebook, e.g. W_kAnd W_k,mRespectively has the size ofAnduser from separate codebook rootSelecting corresponding code words as quantized channel matrix according to the minimum chord distance criterionAndand feeding back the codebook indication information to the serving base station through a feedback channel with time delay. The base station transmits the interference channel information through an X2 interfaceAnd transmitting to the corresponding adjacent cell base station. And the base station performs zero forcing precoding operation by using the acquired non-ideal channel information so as to inhibit multi-user interference in the cell and inter-cell interference to the adjacent cell.

In order to implement the foregoing method, an embodiment of the present invention further provides an adaptive bit allocation apparatus in a cooperative multiple antenna system, as shown in fig. 3, including:

a receiving unit 31, configured to extract data channel information of the local cell, interference channel information of an adjacent cell, receiving powers of a data signal and an interference signal, and delay information of each channel according to channel estimation;

a feedback calculating unit 32, configured to calculate optimal feedback bit numbers allocated to the data channel and each interference channel on the premise that a total feedback bit number is fixed according to the signal receiving power and the delay information of each channel, and minimize a rate loss caused by a non-ideal state of channel information to obtain ideal channel information;

the quantization calculation unit 33 is configured to determine the size of a codebook according to the optimal feedback bit number, select channel state information after quantization of a corresponding codeword from the codebook according to a minimum chordal distance criterion by using the ideal channel information, and feed back index information corresponding to the channel state information to a serving base station through a feedback link with a time delay;

and the base station precoding unit 34 is configured to receive the quantized channel state information through an X2 interface with a time delay, and generate a zero-forcing precoding matrix according to the quantized interference channel information.

Preferably, included in the feedback calculation unit 32;

the minimization processing subunit is used for allocating more feedback bits for the channels with stronger signal power and smaller time delay; and allocating fewer feedback bits for the channel with weaker signal power and larger time delay.

Preferably, the base station precoding unit 4 includes;

and the interference suppression subunit is used for acquiring a null space matrix of the interference channel by using singular value decomposition, and using the null space matrix as a precoding matrix to suppress the two kinds of interference.

The specific implementation of the processing function of each unit included in the adaptive bit allocation apparatus in the cooperative multi-antenna system has been described in the previous method implementation, and is not described again here.

By adopting the scheme of the embodiment, the base station performs zero forcing precoding operation by using the acquired non-ideal channel information, so that multi-user interference in the cell and inter-cell interference to the adjacent cell are suppressed.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (6)

1. A method for adaptive bit allocation in a cooperative multiple antenna system, comprising the steps of:

extracting data channel information of the cell, interference channel information of an adjacent cell, receiving power of a data signal and an interference signal and time delay information of each channel according to channel estimation; wherein, there are M adjacent cells around the cell, the base station of the cell arranges K users to transmit data simultaneously, the K user receives the signal at time point nExpressed as:

$y_k\[n\]=H_k\[n\]T_k\[n\]x_k\[n\]+H_k\[n\]\underset{j=1,j\≠k}{\overset{K}{\Σ}}{T}_j\[n\]x_j\[n\]+\underset{m=1}{\overset{M}{\Σ}}{G}_{k,m}\[n\]T_m\[n\]x_m\[n\]+z_k\[n\]$

in the formula, n_T、n_RThe number of antennas configured for each base station and each user respectively;andchannel matrixes from the local cell and the mth interference cell to the user k at the time point n are respectively;for transmitting data vectors, the maximum transmit power limit is satisfied:P_kthe signal power from the service base station received by the kth user of the cell;precoding a unitary matrix for the block diagonal; z is a radical of_k[n]Denotes the obedience distribution as CN (0, σ)²) Complex gaussian noise vector of (a);

respectively calculating the optimal feedback bit number distributed to the data channel and each interference channel on the premise that the total feedback bit number is fixed according to the signal receiving power and the time delay information of each channel, and minimizing the rate loss caused by the non-ideal state of the channel information to obtain ideal channel information;

determining the size of a codebook according to the optimal feedback bit number, selecting corresponding channel state information after codeword quantization from the codebook according to a minimum chordal distance criterion by using the ideal channel information, and feeding back the channel state information to a service base station through a feedback link with time delay; wherein H_k[n]And G_k,m[n]Respectively by a codebook W based on random vector quantization_kAnd W_k,mTo quantize; codebook W_kAnd W_k,mRespectively has the size ofAndnamely, it is Each element in the codebook is a randomly generated semi-unitary matrix; assume each total feedback bandwidth is B_totBit, wherein B_kAnd B_k,mBit-wise quantization of H_k[n]And G_k,m[n](ii) a Selecting corresponding code words from the codebook as quantized channel matrixAndthe selection method is based on the minimum chord distance criterion:

$\begin{array}{c}{\hat{H}}_k\[n\]=\underset{W_{k\∈}{W}_k}{\arg \min }{d}^2(H_k\[n\],W_k)\\ {\hat{G}}_{k,m}\[n\]=\underset{W_{k,m\∈}{W}_{k,m}}{\arg \min }{d}^2(G_{k,m}\[n\],W_{k,m})\end{array};$

receiving the quantized channel state information through an X2 interface with time delay, and generating a zero-forcing pre-coding matrix according to the quantized interference channel information;

the channel delay due to feedback and information interaction of the X2 interface also causes a loss of system performance, and considering the time-varying block fading channel model, that is, the channel is fixed in one symbol interval and the channel responses between adjacent symbols are correlated, the channel correlation is expressed as:

H_k[n]＝η_kH_k[n-D_k]+E_k[n]

G_k,m[n]＝η_k,mG_k,m[n-D_k,m]+E_k,m[n]；

wherein E is_k[n]And E_k,m[n]Is a channel error matrix and is associated with H_k[n-D_k]And G_k,m[n-D_k,m]Relatively independently, D_kAnd D_k,mNumber of sampling points, E, respectively, of channel delay_k[n]And E_k,m[n]Subject to distribution of elements in (1)Andand respectively satisfyCorrelation coefficient η_kAnd η_k,mDetermined by the clarca autocorrelation model:

η_k＝J₀(2πf_dD_kT_s)

η_k,m＝J₀(2πf_dD_k,mT_s)；

wherein, J₀(. h) is a Bessel function of order 0, f_dFor Doppler shift, T_sIs a symbol interval;

when the transmitting end can obtain ideal channel state information without time delay, the method of cooperative block diagonal precoding based on zero forcing is adopted to completely eliminate the inter-cell interference and the inter-user interference, and the precoding matrix of the method meets the following limitations:

$\begin{array}{c}{H}_j\[n\]T_k\[n\]=0,forj=1,\mathrm{2...}Kandj\≠k\\ G_{k,m}\[n\]T_k\[n\]=0,for1\≤m\≤M\end{array};$

where the first equation represents a zero-forcing limit for intra-cell interference and the second equation represents a zero-forcing limit for inter-cell interference.

2. The method of claim 1, wherein minimizing the rate loss due to channel information non-ideality comprises:

allocating more feedback bits for channels with stronger signal power and smaller time delay; and allocating fewer feedback bits for the channel with weaker signal power and larger time delay.

3. The method of claim 1, wherein generating a zero-forcing precoding matrix according to the quantized interfering channel information comprises:

and obtaining a zero-space matrix of an interference channel by using singular value decomposition, and using the zero-space matrix as a precoding matrix to suppress the two kinds of interference.

4. An adaptive bit allocation apparatus in a cooperative multiple antenna system, comprising:

the receiving unit is used for extracting the data channel information of the cell, the interference channel information of the adjacent cell, the receiving power of the data signal and the interference signal and the time delay information of each channel according to the channel estimation; wherein, there are M adjacent cells around the cell, the base station of the cell arranges K users to transmit data simultaneously, the K user receives the signal at time point nExpressed as:

$y_k\[n\]=H_k\[n\]T_k\[n\]x_k\[n\]+H_k\[n\]\underset{j=1,j\≠k}{\overset{K}{\Σ}}{T}_j\[n\]x_j\[n\]+\underset{m=1}{\overset{M}{\Σ}}{G}_{k,m}\[n\]T_m\[n\]x_m\[n\]+z_k\[n\]$

in the formula, n_T、n_RRespectively for each base station, eachThe number of antennas configured by each user;andchannel matrixes from the local cell and the mth interference cell to the user k at the time point n are respectively;for transmitting data vectors, the maximum transmit power limit is satisfied:P_kthe signal power from the service base station received by the kth user of the cell;precoding a unitary matrix for the block diagonal; z is a radical of_k[n]Denotes the obedience distribution as CN (0, σ)²) Complex gaussian noise vector of (a);

a feedback calculation unit, configured to calculate optimal feedback bit numbers allocated to the data channels and the interference channels on the premise that a total feedback bit number is fixed according to the signal receiving power and the delay information of each channel, and minimize a rate loss caused by a non-ideal state of channel information to obtain ideal channel information;

the quantization calculation unit is used for determining the size of a codebook according to the optimal feedback bit number, selecting corresponding channel state information after codeword quantization from the codebook according to a minimum chordal distance criterion by utilizing the ideal channel information, and feeding back index information corresponding to the channel state information to a service base station through a feedback link with time delay; wherein H_k[n]And G_k,m[n]Respectively by a codebook W based on random vector quantization_kAnd W_k,mTo quantize; codebook W_kAnd W_k,mRespectively has the size ofAndnamely, it isEach element in the codebook is a randomly generated semi-unitary matrix; assume each total feedback bandwidth is B_totBit, wherein B_kAnd B_k,mBit-wise quantization of H_k[n]And G_k,m[n](ii) a Selecting corresponding code words from the codebook as quantized channel matrixAndthe selection method is based on the minimum chord distance criterion:

$\begin{array}{c}{\hat{H}}_k\[n\]=\underset{W_{k\∈}{W}_k}{\arg \min }{d}^2(H_k\[n\],W_k)\\ {\hat{G}}_{k,m}\[n\]=\underset{W_{k,m\∈}{W}_{k,m}}{\arg \min }{d}^2(G_{k,m}\[n\],W_{k,m})\end{array};$

the base station precoding unit is used for receiving the quantized channel state information through an X2 interface with time delay and generating a zero forcing precoding matrix according to the quantized interference channel information;

the channel delay due to feedback and information interaction of the X2 interface also causes a loss of system performance, and considering the time-varying block fading channel model, that is, the channel is fixed in one symbol interval and the channel responses between adjacent symbols are correlated, the channel correlation is expressed as:

H_k[n]＝η_kH_k[n-D_k]+E_k[n]

G_k,m[n]＝η_k,mG_k,m[n-D_k,m]+E_k,m[n]；

wherein E is_k[n]And E_k,m[n]Is a channel error matrix and is associated with H_k[n-D_k]And G_k,m[n-D_k,m]Relatively independently, D_kAnd D_k,mNumber of sampling points, E, respectively, of channel delay_k[n]And E_k,m[n]Subject to distribution of elements in (1)Andand respectively satisfyCorrelation coefficient η_kAnd η_k,mDetermined by the clarca autocorrelation model:

η_k＝J₀(2πf_dD_kT_s)

η_k,m＝J₀(2πf_dD_k,mT_s)；

wherein, J₀(. h) is a Bessel function of order 0, f_dFor Doppler shift, T_sIs a symbol interval;

when the transmitting end can obtain ideal channel state information without time delay, the method of cooperative block diagonal precoding based on zero forcing is adopted to completely eliminate the inter-cell interference and the inter-user interference, and the precoding matrix of the method meets the following limitations:

$\begin{array}{c}{H}_j\[n\]T_k\[n\]=0,forj=1,\mathrm{2...}Kandj\≠k\\ G_{k,m}\[n\]T_k\[n\]=0,for1\≤m\≤M\end{array};$

where the first equation represents a zero-forcing limit for intra-cell interference and the second equation represents a zero-forcing limit for inter-cell interference.

5. The apparatus of claim 4, wherein the feedback calculation unit comprises;

the minimization processing subunit is used for allocating more feedback bits for the channels with stronger signal power and smaller time delay; and allocating fewer feedback bits for the channel with weaker signal power and larger time delay.

6. The apparatus according to claim 4, wherein the base station precoding unit comprises;

and the interference suppression subunit is used for acquiring a null space matrix of the interference channel by using singular value decomposition, and using the null space matrix as a precoding matrix to suppress the two kinds of interference.