CN101777970A - Adaptive multi-antenna receiving and transmission method by using mean and covariance information - Google Patents

Abstract

The invention relates to an adaptive multi-antenna transmission method by using mean and covariance information, which can improve the frequency spectrum utilization and the power efficiency of a communication system to the maximum. The transmission method is performed according to the following steps: calculating statistical information of a channel, namely mean information and covariance information of the channel, by using a result estimated by the channel at a receiving end; determining a mode of power distribution and precoding according to the mean information and the covariance information of the channel and transmitting the mode of power distribution and precoding to a transmitting end; performing power distribution at the transmitting end according to the mode of power distribution and precoding and the channel statistical information which are fed back by the receiving end; and performing precoding transmission at the transmitting end according to the mode of power distribution and precoding and the channel statistical information which are fed back by the receiving end. Through the adaptive multi-antenna system transmission scheme by using the channel statistical information provided by the invention, transmission parameters can be regulated according to the statistical characteristics of the channel; and the obtained mutual information amount approaches the capacity of the channel.

Description

Utilize the adaptive multi-antenna of average and covariance information to receive transmission method

Technical field

The present invention relates to a kind of mobile communication system, relate in particular to a kind of multiaerial system adaptive transmission method that utilizes channel statistical information by using a plurality of send/receive antennas to come transmitting high speed data.

Background technology

For adapting to the needs of future development, back three generations (B3G) or claim the 4th generation (4G) mobile communication system to require to support up to per second tens of million even go up the high-speed packet data transmission of gigabit, under situation about being becoming tight Radio Resource day, adopt many antenna transmission and many antennas to receive (MIMO) Radio Transmission Technology, abundant digging utilization space resources, improve the availability of frequency spectrum and power efficiency to greatest extent, become the key point of back 3 g mobile communication research.

In the actual propagation environment, because the antenna distance and the limitation of scattering object on every side, channel usually exists decline correlation and line of sight, and under the situation of transmitter unknown channel state information, these factors have directly caused the decline of mimo system channel capacity.The adaptive MIMO transmission is the main means that overcome non-ideal factor in the actual propagation environment, need utilize the prior information of channel at transmitting terminal.Under the situation of the known channel condition information completely of transmitter, " water filling " method can reach maximum channel capacity.Yet because the time variation of wireless channel, the time delay of channel estimating and feedback and the skew of frequency make to be difficult to obtain channel condition information completely at transmitting terminal.A kind of method of compromise is to utilize the channel condition information of part, i.e. the statistic behavior information of channel.Channel statistic property, its pace of change are very slow with respect to the instantaneous state of channel, and transmitting terminal can obtain the statistic behavior information of channel reliably.Achievement in research in recent years shows that when transmitting terminal utilized partial channel-state information to carry out the precoding transmission, the channel capacity of mimo system and transmission reliability can be greatly improved.

Theoretical research shows, all exist under the relevant rayleigh fading channel environment in the sending and receiving end, and under the uncorrelated rician fading channel environment, when receiving end knows channel condition information and during the equal value matrix of the transmitting-receiving correlation matrix of the known channel of making a start or channel, the optimal transmission under the channel capacity maximization criterion is the space pre-filtering transmission of feature mode.The design of this transmission mode transmitting terminal is divided into two parts: the selection of optimum sending direction (promptly sending the characteristic vector of signal covariance matrix) and the optimal power allocation on all directions (promptly sending the characteristic value of signal covariance matrix).Studies show that under the channel capacity maximization criterion, under the relevant rayleigh fading channel environment of the relevant battle array of transmitting-receiving of transmitting terminal known channel, optimum sending direction is the characteristic vector that channel sends relevant battle array; Under the incoherent rician fading channel environment of the equal value matrix of transmitting terminal known channel, optimum sending direction is the battle array characteristic vector of the conjugate transpose and the channel average matrix multiple gained matrix of the equal value matrix of channel.About power division, work reported is primarily aimed at numerical solution at present, needs repeatedly iteration, the computation complexity height.Therefore, how know that at transmitting terminal the expression formula that obtains the simple and practical power division of mimo system is necessary under the condition of statistic behavior information of channel.

Summary of the invention

Technical problem: the purpose of this invention is to provide a kind of adaptive multi-antenna of average and covariance information that utilizes and receive transmission method, can be adaptive to complicated multi-antenna wireless transmission environment, improve the power efficiency of communication system.

Technical scheme: the adaptive multi-antenna transmission method of average and covariance information that utilizes of the present invention carries out according to the following steps:

1) utilize the statistical information of the calculating channel as a result of channel estimating at receiving terminal, promptly the equal value information and the covariance information of channel according to the pattern of the equal value information of channel and covariance information decision power division and precoding, and send it to transmitting terminal,

2) at power division and precoding pattern and the channel statistical information of transmitting terminal, carry out power division according to the receiving terminal feedback,

3), carry out the precoding transmission at power division and the precoding pattern and the channel statistical information of transmitting terminal according to the receiving terminal feedback.

Power division and precoding pattern are divided into two kinds: equal binarization mode and covariance pattern, and determine the condition of the pattern that is used to be:

1), the equal value information E[H of channel that statistics obtains if when channel variation is slow] keep off null matrix, then select equal binarization mode, wherein E[] to ask expectation, H be channel matrix in expression, number of transmit antennas is n _T, the reception antenna number is n _R, this moment, channel matrix H was modeled as at transmitting terminal

Wherein this factor K of Lay is represented the ratio of line of sight and scattering footpath power, and H is normalized line of sight matrix, H _wBeing one is zero by average, and variance is 1 independent identically distributed collision matrix of answering the gaussian variable composition, and the singular value decomposition of supposing H is H=UDV ^H, subscript () wherein ^HThe expression conjugate transpose,

With

Be unitary matrice, D is a n _R* n _T" diagonal matrix ", n here _R* n _T" diagonal matrix " refer to when i ≠ j matrix (i, j) element is 0, its " diagonal element " d ₁₁〉=d ₂₂〉=L 〉=d _Mm〉=0, m=min (n _T, n _R), power division and method for precoding are under this pattern: the sending direction pre-coding matrix is chosen as U _Q=V, power division matrix are diagonal matrix, and its diagonal element is

1≤i≤n _T, μ is by total emission power

The constant of decision, σ ²Be the noise variance on each antenna of receiving terminal;

2) if channel variation is very fast, the equal value information E[H of channel that statistics obtains] near null matrix, then select the covariance pattern, this moment, channel matrix H was modeled as at transmitting terminal

H wherein _wDefinition identical with the definition under equal binarization modes, Θ _TAnd Θ _RBe the Hermite matrix of positive definite, representative transmits and receives the decline correlation matrix respectively, supposes Θ _TAnd Θ _RCharacteristic value decomposition be

And Wherein

Diag{} represents that with element in { } be the diagonal matrix of diagonal entry, diagonal element

Under this pattern, power division and pre-coding scheme are: the sending direction pre-coding matrix is chosen as U _Q=U _T, the power division matrix is a diagonal matrix, its diagonal element is 1≤i≤n _T, μ is by total emission power

The constant of decision, σ ²Be the noise variance on each antenna of receiving terminal.

Beneficial effect: the invention provides a kind of adaptive multi-antenna of average and covariance information that utilizes and receive transmission method, this programme has following advantage:

1. this programme only needs the statistical information of channel, therefore only can know that to transmitting terminal the system of channel statistical information is very practical.

2. the power allocation scheme computation complexity in this programme is low, does not need to carry out the numerical optimization process in the numerical method.

3. it is very approaching that channel capacity that this programme obtained and optimum power are distributed the channel capacity that is obtained.

Description of drawings

Fig. 1 is the multiaerial system adaptive transmission method block diagram that the present invention utilizes average and covariance information.

Embodiment

Consider that a number of transmit antennas is n _T, the reception antenna number is n _RMimo wireless communication system, on the basis that its channel capacity is analyzed, can construct as shown in Figure 1 transmitting terminal pre-coding scheme by the upper bound of maximum channel capacity.This scheme can be described as:

At receiving terminal, to digital baseband receiving signals

Carry out channel estimating, wherein y _i(n) received signal of i reception antenna of expression, subscript () ^TThe expression conjugate transpose.Utilize the statistical information of the calculating channel as a result of channel estimating.Utilizing the equal binarization mode of statistical information selection employing of these channels still is the covariance pattern, and will adopt the channel statistical information under which kind of pattern and the corresponding modes to feed back to transmitting terminal.

At transmitting terminal, utilize the pattern information and the channel statistical information of feedback, computer memory power division matrix Λ and sending direction pre-coding matrix U _QIncoming symbol is flowed

Carry out linear predictive coding, obtain sending signal

D wherein _i(n) i incoming symbol stream of expression, s _i(n) the transmission signal of i transmitting antenna of expression.Satisfy following relation between d (n) and the s (n):

s(n)＝Fd(n)， 【1】

Wherein,

F＝U _QΛ ^1/2 【2】

It is pre-coding matrix.

For making the technical scheme among the present invention clearer, below this programme is specifically described:

One, the acquisition of channel statistical information

Channel statistical information in the described scheme is the noise variance σ on each antenna of receiving terminal ², and the equal value information of channel or the covariance information of channel.We use n _R* n _TMatrix H represent channel matrix.

(1) the equal value information of channel

When in equal binarization modes following time, when the channel statistical information that transmitting terminal is known was equal value information, channel matrix H was modeled as at transmitting terminal:

$H=\sqrt{\frac{K}{K+1}}\stackrel{\‾}{H}+\sqrt{\frac{1}{K+1}}{H}_w,$ 【3】

Wherein this factor K of Lay is represented the ratio of line of sight and scattering footpath power.H is normalized line of sight matrix, tr (HH ^H)=n _Tn _R, the mark of tr () representing matrix, subscript () ^HThe expression conjugate transpose.H _wBeing one is zero by average, and variance is 1 independent identically distributed collision matrix of answering the gaussian variable composition.K and H are the equal value information of the known channel of transmitting terminal.Utilize the estimated value of channel parameter, K and H can be expressed as:

$K=\frac{\mathrm{tr}\left(E\right[H\left]E{\left[H\right]}^H\right)}{E[\mathrm{tr}\left((H-E[H){(H-E[H\left]\right)}^H\right)},$ 【4】

$\stackrel{\‾}{H}=\sqrt{\frac{1+K}{K}}E\left[H\right],$ 【5】

E[wherein] expression asks expectation.

(2) covariance information

Under the covariance pattern, transmitting terminal known channel covariance information, channel matrix H is modeled as at transmitting terminal:

$H={\mathrm{\Θ}}_R^{1/2}{H}_w{\mathrm{\Θ}}_T^{1/2},$ 【6】

H wherein _wThe definition of definition during with the equal value information of transmitting terminal known channel identical.Θ _TAnd Θ _RBe the Hermite matrix of positive definite, representative transmits and receives the decline correlation matrix respectively, satisfies tr (Θ _T)=n _T, tr (Θ _R)=n _RΘ _TAnd Θ _RBe the known channel covariance information of transmitting terminal.Utilize the estimated value of channel parameter, Θ _TAnd Θ _RCan be expressed as:

${\mathrm{\Θ}}_T=\frac{1}{n_R}E\left[H^{H}H\right],$ 【7】

${\mathrm{\Θ}}_R=\frac{1}{n_T}E\left[{\mathrm{HH}}^H\right].$ 【8】

Two, sending direction pre-coding matrix

Sending direction pre-coding matrix U in the described scheme _QSelection be divided into equal binarization mode and two kinds of situations of covariance pattern.

(1) equal binarization mode

Under equal binarization mode, the channel statistical information that transmitting terminal is known is equal value information, and the singular value decomposition of supposing H is H=UDV ^H, wherein With

Be unitary matrice, D is a n _R* n _T" diagonal matrix " (n here _R* n _T" diagonal matrix " refer to (i, j) element is 0) of matrix when i ≠ j, its " diagonal element " d ₁₁〉=d ₂₂〉=L 〉=d _Mm〉=0, m=min (n _T, n _R).In this case, sending direction pre-coding matrix U _QBe chosen as U _Q=V.

(2) covariance pattern

Under the covariance pattern, the channel statistical information that transmitting terminal is known is a covariance information, order emission decline correlation matrix Θ _TWith reception decline correlation matrix Θ _RCharacteristic value decomposition be

And

Wherein

Diag{} represents that with element in { } be the diagonal matrix of diagonal entry, diagonal element

In this case, sending direction pre-coding matrix U _QBe chosen as U _Q=U _T

Three, power division matrix

Power division matrix Λ in this programme can be expressed as:

$\mathrm{\Λ}=\mathrm{diag}\{{\mathrm{\λ}}_1,{\mathrm{\λ}}_2,L,{\mathrm{\λ}}_{n_T}\},$ 【9】

Wherein ${\mathrm{\λ}}_1\≥{\mathrm{\λ}}_2\≥L{\≥\mathrm{\λ}}_{n_T}\≥0.$

(1) equal binarization mode

Under equal binarization mode, the diagonal element of corresponding power allocation matrix is:

${\mathrm{\λ}}_i=\max (0,\mathrm{\μ}-\frac{{\mathrm{\σ}}^2(1+K)K}{\frac{n_R(n_R-1)({\mathrm{Kn}}_T+1)}{n_T{n}_R-d_{\mathrm{ii}}^2}+K{d}_{\mathrm{ii}}^2}),1\≤i\≤n_T,$ 【10】

Thresholding μ is by total emission power The constant of decision.

(2) covariance pattern

Under the covariance pattern, the diagonal element of corresponding power allocation matrix is:

${\mathrm{\λ}}_i=\max (0,\mathrm{\μ}-\frac{n_R{\mathrm{\σ}}^2}{n_R^2-{\mathrm{\Σ}}_{j=1}^{n_R}{\mathrm{\λ}}_{\mathrm{rj}}^2}{\mathrm{\λ}}_{\mathrm{ti}}^{-1}),1\≤i\≤n_T,$ 【11】

Thresholding μ is by total emission power

The constant of decision.

The specific embodiment of the invention is as follows:

Receiving terminal:

1) utilize received signal to carry out channel estimating, calculate E[H], it still is the covariance pattern that equal binarization mode is adopted in decision.If E[H] near zero, then adopt the covariance pattern, utilize formula [7]-[8] to calculate Θ _TAnd Θ _ROtherwise the employing mean value model utilizes formula [4]-[5] calculating K and H.

2) will adopt the feedback information of which kind of pattern to give transmitting terminal, simultaneously the channel statistical information under the corresponding modes be fed back to transmitting terminal: if employing is equal binarization mode, then with K and H feedback; If what adopt is the covariance pattern, then with Θ _TAnd Θ _RFeedback.

Transmitting terminal:

3) pattern information of utilizing receiving terminal to feed back, which kind of pattern what judge employing is.If what adopt is equal binarization mode, then the H to feedback carries out singular value decomposition H=UDV ^H, obtain sending direction precoding battle array U _Q=V and D; As if what adopt is the covariance pattern, then the emission decline correlation matrix Θ to feeding back _TWith reception decline correlation matrix Θ _RCarry out characteristic value decomposition

Obtain sending direction precoding battle array U _Q=U _T, Λ _TAnd Λ _R

4) rated output allocation matrix.If what adopt is equal binarization mode, then utilize 3) in the D that obtains and the noise variance σ in the statistical information ²With this factor K of Lay, according to formula [9]-[10] rated output allocation matrix Λ; If what adopt is the covariance pattern, utilize 3) in the Λ that obtains _TAnd Λ _RAnd noise variance σ ², according to formula [9] and formula [11] rated output allocation matrix Λ.

5) utilize 3) and 4) in the U that calculates _QAnd Λ, calculate the linear predictive coding matrix according to formula [2] and send control.

Claims (1)

1. adaptive multi-antenna transmission method that utilizes average and covariance information is characterized in that this transmission method carries out according to the following steps:

1) utilize the statistical information of the calculating channel as a result of channel estimating at receiving terminal, promptly the equal value information and the covariance information of channel according to the pattern of the equal value information of channel and covariance information decision power division and precoding, and send it to transmitting terminal; The condition of the pattern that decision is adopted is:

A), the equal value information E[H of channel that statistics obtains if when channel variation is slow] keep off null matrix, then select equal binarization mode, wherein E[] to ask expectation, H be channel matrix in expression, number of transmit antennas is n _T, the reception antenna number is n _R, this moment, channel matrix H was modeled as at transmitting terminal

Wherein K is the ratio that this factor of Lay is represented line of sight and scattering footpath power, and H is normalized line of sight matrix, H _wBeing one is zero by average, and variance is 1 independent identically distributed collision matrix of answering the gaussian variable composition, and the singular value decomposition of supposing H is H=UDV ^H, subscript () wherein ^HThe expression conjugate transpose,

With

Be unitary matrice, D is a n _R* n _T" diagonal matrix ", n here _R* n _T" diagonal matrix " refer to when i ≠ j matrix (i, j) element is 0, its " diagonal element " d ₁₁〉=d ₂₂〉=L 〉=d _Mm〉=0, m=min (n _T, n _R), the minimum value that element in () is got in min () expression.Power division and method for precoding are under this pattern: sending direction pre-coding matrix U _QBe chosen as U _Q=V, power division matrix are diagonal matrix, and its diagonal element is

μ serves as reasons The constant of decision, P total emission power, σ ²Be the noise variance on each antenna of receiving terminal;

B) if channel variation is very fast, the equal value information E[H of channel that statistics obtains] near null matrix, then select the covariance pattern, this moment, channel matrix H was modeled as at transmitting terminal

H wherein _wDefinition identical with the definition under equal binarization modes, Θ _TAnd Θ _RBe the Hermite matrix of positive definite, representative transmits and receives the decline correlation matrix respectively, supposes Θ _TAnd Θ _RCharacteristic value decomposition be

And

Wherein

Diag{} represents that with element in { } be the diagonal matrix of diagonal entry, diagonal element

Under this pattern, power division and pre-coding scheme are: sending direction pre-coding matrix U _QBe chosen as U _Q=U _T, the power division matrix is a diagonal matrix, its diagonal element is

μ serves as reasons

The constant of decision, P total emission power, σ ²Be the noise variance on each antenna of receiving terminal;

2) at power division and precoding pattern and the channel statistical information of transmitting terminal, carry out power division according to the receiving terminal feedback;

3), carry out the precoding transmission at power division and the precoding pattern and the channel statistical information of transmitting terminal according to the receiving terminal feedback.

Images