CN100373841C - A multi-user space-time block code detection method - Google Patents

Abstract

The invention discloses a multi-user space-time block coding (STBC) detection method. Before each user is detected at the receiving end, the receiving signal-to-noise ratio is first sorted to find the user corresponding to the largest signal-to-noise ratio. First detect the user, get the estimated value of the signal sent by the user, then subtract the influence of the estimated value of the signal from the received signal, that is, reconstruct the signal, and then sort the remaining signals again to determine the corresponding value of the next largest SNR users, and detect them in turn until all users’ sending signals are detected. Since each time a user's transmission signal is detected, the transmission signal corresponding to the user with the highest signal-to-noise ratio among the signals to be detected is always selected, so the accuracy of each detection is improved, and the accuracy of the reconstructed signal is also improved. accuracy, thereby reducing the bit error rate.

Description

A kind of multi-user space time block code detection method

Technical field

The invention belongs to wireless communication technology field, particularly the detection method of multi-user space time block code (STBC).

Background technology

From present development of Communication Technique, follow-on mobile communication system must have higher spectrum efficiency and transmission reliability.Multi-user MIMO system adopts many transmitting antennas and reception antenna respectively at transmitting terminal and receiving terminal, can be under the prerequisite that does not increase bandwidth, the channel capacity of raising system, obtain simultaneously to send and the receive diversity gain, improve transmission reliability, therefore become the main developing direction of next generation wireless communication.

The key that mimo system obtains the high-transmission reliability is to have adopted the Space Time Coding technology.Space Time Coding mainly comprises at present: trellis coding when empty (Space-Time Trellis Coded, STTC) and space-time block code (Space-Time Block Coded, STBC).Single user's space-time block code is proposed by Alamouti the earliest, a user utilizes two transmitting antennas to send symbol, owing to carried out orthogonal coding for the symbol on two antennas at transmitting terminal, therefore in receiving terminal decoding, utilize the orthogonality of its code word, only need to adopt simple linear process to get final product, thereby greatly reduce decoding complexity, be beneficial to realization.Content sees Alamouti S M. for details, A Simple Transmit Diversity Technique for Wireless Communications[J] .IEEE Journal on Select Areas in Communications, 1998,16 (8). adopt another advantage of STBC to be, because there is certain contact in the transmitting terminal symbol, (this contact be by the decision of the orthogonal configuration of its code word) therefore, under the flat fading channel condition, obtain channel estimating by over-sampling, can make the number of the number of reception antenna less than transmitting antenna, this is other system, does not accomplish as VBLAST.Subsequently, Tarokh is generalized to situation more than two antennas to the scheme of Alamouti on the basis of orthogonal design theory.

The method of Interference Cancellation is adopted in the detection of traditional multi-user STBC system, whenever detects after a user's the transmission symbol, rebuilds residual signal, successively up to the transmission symbol that detects all users.Content sees Waleed M.Younis for details, AliH.Sayed, Naofal Al-Dhahir, Efficient Adaptive Receivers for Joint Equalization and InterferenceCancellation in Mutiuser Space-Time Block-Coded Systems[J], IEEE Transactions on SignalProcessing, Vol.51.No.11, November 2003.

The shortcoming that this method exists is: detect fixed order, detect to first user from last user successively, owing to do not consider the influence of received signal to noise ratio to demodulation, cause performance not good.

Summary of the invention

The detection method that the purpose of this invention is to provide a kind of multi-user space time block code adopts this method, can improve greatly and detect performance under the prerequisite of the detection method complexity that does not significantly improve traditional multi-user STBC system.

The invention provides the detection method of a kind of multi-user space time block code STBC, this method is to adopt following step to realize:

Step 1: initialization, set up multi-user STBC system model:

Our define system has M user, and each user has two transmitting antennas, and the signal that defines j user's transmission is X _j, i root reception antenna receives that signal is Y _i, Λ _IjThe equivalent channel matrix of representing the corresponding i root of j user reception antenna, N _iNoise vector for corresponding i root reception antenna.The method of the single user STBC of the foundation system that proposes according to Alamouti then, single user STBC system model can be expressed as:

Y _i＝Λ _ijX _j+N _i (1)

$Y_i=\left(\begin{array}{c}{Y}_i^{\left(k\right)}\\ {\stackrel{\‾}{Y}}_i^{(k+1)}\end{array}\right),$ $X_j=\left(\begin{array}{c}{X}_{j_1}^{\left(k\right)}\\ X_{j_2}^{\left(k\right)}\end{array}\right),$ $N_i=\left(\begin{array}{c}{N}_i^{\left(k\right)}\\ {\stackrel{\‾}{N}}_i^{(k+1)}\end{array}\right)$ (2)

K and k+l represent to be in two adjacent time-slots under the same channel status,

Represent the signal that i root reception antenna is received constantly at k,

The conjugation of representing the signal that i root reception antenna is constantly received at (k+1).

Represent the symbols of first, second root transmitting antenna of j user respectively in the transmission of seven moment, Represent i root reception antenna at k pairing noise component(s) of the moment,

Represent the conjugation of i root reception antenna at pairing noise component(s) of (k+1) moment.

Λ _IjExpression formula be:

${\mathrm{\&Lambda;}}_{\mathrm{ij}}=\left(\begin{array}{cc}{\mathrm{\&Lambda;}}_{i{\mathrm{<figure-callout\; id="1"\; label="j"\; filenames="C20041004055200181.png"\; state="\{\{state\}\}">j</figure-callout>}}_1}& {\mathrm{\&Lambda;}}_{i{j}_2}\\ {\mathrm{\&Lambda;}}_{i{j}_2}^{*}& {-\mathrm{\&Lambda;}}_{i{\mathrm{<figure-callout\; id="1"\; label="j"\; filenames="C20041004055200181.png"\; state="\{\{state\}\}">j</figure-callout>}}_1}^{*}\end{array}\right)---\left(3\right)$

Wherein

The channel fading factor of representing j user's the corresponding i root of first, second root transmitting antenna reception antenna respectively,

Be respectively

Conjugation, claim matrix Λ _IjMatrix for the Alamouti structure.

According to the method for setting up multi-user STBC system of propositions such as Waleed, multi-user STBC system model can be expressed as:

Claim that Y is the received signal vector, X is for sending signal phasor, and N is a noise vector, wherein Y _i, X _i, N _i, 1≤i≤M is the structure of formula (2) expression.

Claim that Λ is the channel matrix of M user STBC system, wherein each Λ _Ij, 1≤i≤M, 1≤j≤M are the matrix of 2 * 2 Alamouti structure of formula (3) expression.For convenience, we define Λ _IjBe the element of matrix Λ, so Λ is the matrix of M * M.

Step 2: determine the detection order:

Owing to after detecting a user's transmission symbol, will rebuild residual signal one time at every turn, upgrades one time channel matrix, thereby determine that the detection that makes new advances in proper order.And, suppose that at the channel matrix of the i time definite detection in proper order the time be Λ because the every renewal of channel matrix once, will reduce by row ⁱSo, Λ ⁱMatrix for M * (M+1-i).So the initial channel matrix Λ in the formula (4) is Λ ¹

1) divides channel matrix Λ ⁱ:

Divide Λ the i time ⁱMethod: at matrix Λ ⁱCapable and last the row line of inverse i, two lines are with matrix Λ ⁱBe divided into four submatrixs, be made as A respectively, B, C, D.Here still define Λ _Ij, 1≤i≤M, 1≤j≤M+1-i are an element.

Divide Λ when determining the detection order for the first time ¹As follows:

Wherein A is the submatrix of (M-1) * (M-1), and B is the submatrix of (M-1) * 1, and C is 1 * (M-1) submatrix, and D is 1 * 1 submatrix.

Divide Λ during the i time definite detection order ⁱAs follows:

Wherein A is the submatrix of (M-i) * (M-i), and B is the submatrix of (M-i) * 1, and C is the submatrix of i * (M-i), and D is the submatrix of i * 1.

2) according to formula

${\mathrm{\&Delta;}}_{k_i}=D-C{A}^{-1}B---\left(7\right)$

Obtain

Matrix, and calculate

The row norm of first row of matrix.

3) reset channel matrix Λ ⁱ:

With channel matrix Λ ⁱFirst row place last row, all the other leu prefaces are that original secondary series is become first row in advance, the 3rd row become secondary series, the rest may be inferred, the channel matrix after obtaining resequencing.

4) repeating step 1), 2), 3), altogether (M+1-i) is inferior, obtains (M+1-i) individual row norm successively, determines the channel matrix Λ of wherein maximum row norm correspondence ⁱArrangement mode, and determine the channel matrix Λ of maximum row norm correspondence ⁱLast be listed as pairing user.

Step 3: demodulation draws the estimated value that step 2 is determined user's transmission signal

Utilize the orthogonality of STBC, can obtain the channel matrix Λ of the row norm correspondence of the maximum that obtains through step 2 ⁱDiagonalizable matrix P, receive vector Y with diagonalizable matrix P premultiplication, obtain following expression:

Z wherein _{1: M-i}, , ∑ _{1: M-i}, be intermediate variable, I _{2 (M-i) * 2 (M-i)}Be the unit matrix of 2 (M-i) * 2 (M-i), I _{2i * 2i}, be the unit matrix of 2i * 2i, establish:

$X_{k_i}=\left(\begin{array}{c}{X}_{k_i^1}\\ X_{k_i^2}\\ .\\ .\\ .\\ \stackrel{\&OverBar;}{X_{k_i^{M+1-i}}}\end{array}\right),\tilde{N}=\begin{array}{c}\left(\begin{array}{c}{\tilde{N}}_1\\ {\tilde{N}}_2\\ .\\ .\\ .\\ \stackrel{\&OverBar;}{{\tilde{N}}_M}\end{array}\right)---\left(9\right)\end{array}$

Expression detects k _iDuring individual user, by the channel matrix Λ of the row norm correspondence of maximum ⁱThe determined user's to be detected of arrangement mode the transmission signal phasor that puts in order.

The correction noise vector that obtains for P matrix premultiplication noise vector N.

According to formula:

${\hat{X}}_{k_i}=Q\left({\left({\mathrm{\&Delta;}}_{k_i}\right)}^{-1}{Z}_{k_i}\right)---\left(10\right)$

Obtain k _iThe estimated value of individual user's transmission signal

, wherein Q () represents decision function, will

Value be mapped to point in the planisphere.So just can demodulate a matting user's transmission signal.

Step 4: reconstruction signal:

At first, the k that step 3 is obtained _iThe estimated value of individual user's transmission signal

Influence from received signal Y the inside deduction, so obtain Y ':

$Y\&prime;=\left(\begin{array}{c}{Y}_1^{\&prime;}\\ Y_2^{\&prime;}\\ .\\ .\\ .\\ Y_M^{\&prime;}\end{array}\right)=Y-{\hat{X}}_{k_i}{\mathrm{\&Lambda;}}_{k_i}=\left(\begin{array}{c}{Y}_1\\ Y_2\\ .\\ .\\ .\\ Y_M\end{array}\right)-{\hat{X}}_{k_i}\left(\begin{array}{c}{\mathrm{\&Lambda;}}_{{1k}_i}\\ {\mathrm{\&Lambda;}}_{{2k}_i}\\ .\\ .\\ .\\ {\mathrm{\&Lambda;}}_{{\mathrm{Mk}}_i}\end{array}\right)---\left(11\right)$

Wherein

Be initial channel matrix Λ k in the formula (4) _iRow.

Secondly, rebuild the residual signal model: renewal Y is Y '.From Λ ⁱIn remove initial channel matrix Λ k _iRow, promptly

Upgrade channel matrix Λ ⁱBe Λ ^I+1:

Step 5: repeating step 2,3,4, altogether (M-1) is inferior, will come out than (M-1) the individual user's of high s/n ratio correspondence transmission signal demodulation.

Step 6: demodulation last, i.e. the user's that signal to noise ratio is minimum transmission signal:

When remaining last user, expression formula is arranged:

$Y_{k_M}={\mathrm{\&Lambda;}}_{k_M}{X}_{k_M}+N_{k_M}---\left(13\right)$

Wherein Be the received signal vector after deduction detected (M-1) individual user's the influence, K for initial channel matrix Λ _MRow, Be last user's transmission signal,

The noise vector of correspondence when detecting last user.

According to formula:

${\hat{X}}_{k_M}=Q\left({\left({\mathrm{\&Lambda;}}_{k_M}\right)}^{-1}{Y}_{k_M}\right)---\left(14\right)$

Get to the end, i.e. k _MThe estimated value of individual user's transmission signal , wherein Q () is the decision function in the formula (10), so just can demodulate last user's transmission signal.

Through after the above step, just can realize detection to multi-user STBC system.

Need to prove:

What we used in step 2 the inside is vectorial two norms, also can be with other norm.

What we used in step 3 the inside is hard decision, also can be soft-decision.

After step 6 finished, in order further to improve systematic function, we can also adopt iterative idea, i.e. the operation of repeating step 2～6, and the present invention no longer describes in detail.

Essence of the present invention is: the received signal that needs are detected sorts, detect earlier the strongest signal of received signal to noise ratio, secondly the influence of this signal of deduction is rebuild from received signal, then to residual signal minor sort again, by same quadrat method, successively up to detecting all transmission signals.

Innovation part of the present invention is:

Consider that received signal to noise ratio is for detecting Effect on Performance, the thought of introducing ordering.Before user of the every detection of receiving terminal, earlier received signal to noise ratio is sorted, find the maximum pairing user of signal to noise ratio, at first detect this user, obtain the estimated value that this user sends signal, from received signal, deduct the influence of the estimated value of this signal then, be reconstruction signal, then residual signal carried out minor sort again, determine the pairing user of next maximum signal to noise ratio, and detect, successively up to the transmission signal that detects all users.Because when a user's of each detection transmission signal, always select the transmission signal of that user's correspondence that signal to noise ratio is the highest in the signal to be detected, so improved the accuracy of each detection, also improved the accuracy of reconstruction signal simultaneously, thereby reduced the error rate.Method proposed by the invention can be widely used in the detection of multi-user STBC system.

Description of drawings

Fig. 1 is the fundamental diagram of traditional multi-user STBC system

Wherein, the 1st, data source unit, the 2nd, space-time block code element, the 3rd, launching antenna array column unit, the 4th, receiving antenna array column unit, the 5th, multi-user STBC detecting unit, the 6th, single user STBC detecting unit, y ₁, y ₂, y _MBe the input signal of unit 5,

,

Be respectively the output signal of each single user STBC detecting unit in the unit 6.

Fig. 2 is the workflow diagram of groundwork step of the present invention

Fig. 3 is the fundamental diagram of multi-user STBC of the present invention system

Wherein, the 1st, data source unit, the 2nd, space-time block code element, the 3rd, launching antenna array column unit, the 4th, receiving antenna array column unit, the 7th, multi-user STBC detecting unit of the present invention, the 6th, single user STBC detecting unit, y ₁, y ₂, y _MBe the input signal of unit 7,

,

Be respectively the output signal of each single user STBC detecting unit in the unit 6.

Fig. 4 is the performance comparison diagram under an instantiation of traditional multi-user STBC detection method and multi-user STBC detection method of the present invention

Wherein curve 1 is the performance curve of traditional detection method, and curve 2 is performance curves of detection method of the present invention.If TX represents number of transmit antennas, RX represents the reception antenna number, can see, the improvement multi-user STBC algorithm that adopts ordering thought has the raising of about 3dB left and right sides performance during than the past 15dB of traditional multi-user STBC detection algorithm.

Embodiment:

Example of the present invention is as described below, and parameter setting does not influence generality, the The data BPSK modulation in tentation data source, number of users M=4, number of transmit antennas is 2M=8, reception antenna is counted N=4, channel is uncorrelated slow fading channel, 5 kilometers/hour of the speed of a motor vehicle.

The data of emission are through after the BPSK modulation, go here and there and change, and are divided into M road signal flow, go out by transmission antennas transmit, the signal of launching is through after the space channel, and by N reception antenna reception of receiving terminal, the signal phasor of supposing transmission antennas transmit is a=(X ₁X ₂X ₃X ₄The signal phasor that) ', reception antenna is received is r=(Y ₁Y ₂Y ₃Y ₄) ', white Gaussian noise vector is v=(N ₁N ₂N ₃N ₄) ', channel matrix is

$\mathrm{\&Lambda;}=\left(\begin{array}{cccc}{\mathrm{\&Lambda;}}_{11}& {\mathrm{\&Lambda;}}_{12}& {\mathrm{\&Lambda;}}_{13}& {\mathrm{\&Lambda;}}_{14}\\ {\mathrm{\&Lambda;}}_{21}& {\mathrm{\&Lambda;}}_{22}& {\mathrm{\&Lambda;}}_{23}& {\mathrm{\&Lambda;}}_{24}\\ {\mathrm{\&Lambda;}}_{31}& {\mathrm{\&Lambda;}}_{32}& {\mathrm{\&Lambda;}}_{33}& {\mathrm{\&Lambda;}}_{34}\\ {\mathrm{\&Lambda;}}_{41}& {\mathrm{\&Lambda;}}_{42}& {\mathrm{\&Lambda;}}_{43}& {\mathrm{\&Lambda;}}_{44}\end{array}\right),$ The detailed process that detects is as follows:

1. when the i time definite detection order, establishing channel matrix is Λ ⁱ, divide Λ ⁱThe time, as follows it is divided into four sub-matrix A, B, C, D:

According to formula (7), obtain , calculate First row the row norm, reset Λ then ⁱ, calculate the Λ after resetting once more ⁱObtain through dividing once more

The matrix column norm up to obtaining (5-i) individual row norm, is determined the channel matrix Λ of wherein maximum row norm correspondence ⁱArrangement mode, and determine the channel matrix Λ of maximum row norm correspondence ⁱLast be listed as pairing user.

2. demodulation draws the estimated value of the determined user's of step 1 transmission signal

Obtain the channel matrix Λ of the row norm correspondence of the maximum that obtains through step 1 ⁱDiagonalizable matrix P, receive vector Y with diagonalizable matrix P premultiplication, obtain following expression:

According to formula:

${\hat{X}}_{k_i}=Q\left({\left({\mathrm{\&Delta;}}_{k_i}\right)}^{-1}{Z}_{k_i}\right)---\left(17\right)$

Obtain k _iThe estimated value of individual user's transmission signal

, wherein Q () represents decision function, will

Value be mapped to point in the planisphere.So just can demodulate k _iIndividual user's transmission signal.

3. reconstruction received signal is about to

Influence from received signal the inside deduction, so obtain Y ':

$Y\&prime;=\left(\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="Y"\; filenames="C20041004055200181.png"\; state="\{\{state\}\}">Y</figure-callout>}}_1^{\&prime;}\\ Y_2^{\&prime;}\\ {\mathrm{<figure-callout\; id="3"\; label="Y"\; filenames="C20041004055200181.png"\; state="\{\{state\}\}">Y</figure-callout>}}_3^{\&prime;}\\ {\mathrm{<figure-callout\; id="4"\; label="Y"\; filenames="C20041004055200181.png"\; state="\{\{state\}\}">Y</figure-callout>}}_4^{\&prime;}\end{array}\right)=Y-{\hat{X}}_{k_i}{\mathrm{\&Lambda;}}_{k_i}=\left(\begin{array}{c}{Y}_1\\ Y_2\\ Y_3\\ Y_4\end{array}\right)-{\hat{X}}_{k_i}\left(\begin{array}{c}{\mathrm{\&Lambda;}}_{1k_i}\\ {\text{\&Lambda;}}_{2k_i}\\ {\mathrm{\&Lambda;}}_{3k_i}\\ {\mathrm{\&Lambda;}}_{4k_i}\end{array}\right)---\left(18\right)$

Renewal Y is Y '.From Λ ⁱIn remove the k of initial channel matrix Λ _iRow upgrade channel matrix Λ ⁱBe Λ ^I+1:

${\mathrm{\&Lambda;}}^{i+1}\stackrel{\mathrm{\&Delta;}}{=}\left(\begin{array}{cccccc}{\mathrm{\&Lambda;}}_{11}& \&CenterDot;\&CenterDot;\&CenterDot;& {\mathrm{\&Lambda;}}_{1k_i-1}& {\mathrm{\&Lambda;}}_{1k_i+1}& \&CenterDot;\&CenterDot;\&CenterDot;& {\mathrm{\&Lambda;}}_{1(4+1-i)}\\ {\mathrm{\&Lambda;}}_{21}& \&CenterDot;\&CenterDot;\&CenterDot;& {\mathrm{\&Lambda;}}_{2k_i-1}& {\mathrm{\&Lambda;}}_{2k_i+1}& \&CenterDot;\&CenterDot;\&CenterDot;& {\mathrm{\&Lambda;}}_{2(4+1-i)}\\ {\mathrm{\&Lambda;}}_{31}& \&CenterDot;\&CenterDot;\&CenterDot;& {\mathrm{\&Lambda;}}_{3k_i-1}& {\mathrm{\&Lambda;}}_{3k_i+1}& \&CenterDot;\&CenterDot;\&CenterDot;& {\mathrm{\&Lambda;}}_{3(4+1-i)}\\ {\mathrm{\&Lambda;}}_{41}& \&CenterDot;\&CenterDot;\&CenterDot;& {\mathrm{\&Lambda;}}_{4k_i-1}& {\mathrm{\&Lambda;}}_{4k_i+1}& \&CenterDot;\&CenterDot;\&CenterDot;& {\mathrm{\&Lambda;}}_{4(4+1-i)}\end{array}\right)---\left(19\right)$

4. repeating step 1,2,3, three times altogether, will come out than three users' of high s/n ratio correspondence transmission signal demodulation.

5. last (signal to noise ratio is minimum) user's of demodulation transmission signal:

When remaining last user, expression formula is arranged:

${\mathrm{<figure-callout\; id="4"\; label="Y\; k"\; filenames="C20041004055200181.png"\; state="\{\{state\}\}">Y</figure-callout>}}_{k_{}}={\mathrm{\&Lambda;}}_{k_4}{\mathrm{<figure-callout\; id="4"\; label="X\; k"\; filenames="C20041004055200181.png"\; state="\{\{state\}\}">X</figure-callout>}}_{k_{}}+N_{k_4}---\left(20\right)$

Wherein

Be the received signal vector after detected three users' of deduction the influence,

K for initial channel matrix Λ ₄Row,

Be last user's transmission signal,

The noise vector of correspondence when detecting last user.

According to formula:

${\hat{X}}_{{\mathrm{<figure-callout\; id="4"\; label="k"\; filenames="C20041004055200181.png"\; state="\{\{state\}\}">k</figure-callout>}}_4}=Q\left({\left({\mathrm{\&Lambda;}}_{k_4}\right)}^{-1}{Y}_{k4}\right)---\left(21\right)$

Get to the end, i.e. k ₄The estimated value of individual user's transmission signal , wherein Q () is the decision function in the formula (10), so just can demodulate last user's transmission signal.

Through after the above step, just can realize detection to four-function family STBC system.

Claims (1)

1. the detection method of a multi-user space time block code STBC, it is that step below adopting realizes:

Step 1: initialization, set up multi-user STBC system model:

Our define system has M user, and each user has two transmitting antennas, and to define the signal that j user send be X _j, i root reception antenna receives that signal is Y _i, Λ _IjThe equivalent channel matrix of representing the corresponding i root of j user reception antenna, N _iNoise vector for corresponding i root reception antenna; Single user STBC system model can be expressed as:

Y _i＝Λ _ijX _j+N _i (1)

Wherein

$Y_i=\left(\begin{array}{c}{Y}_i^{\left(k\right)}\\ {\stackrel{\&OverBar;}{Y}}_i^{(k+1)}\end{array}\right),$ $X_j=\left(\begin{array}{c}{X}_{j_1}^{\left(k\right)}\\ X_{j_2}^{\left(k\right)}\end{array}\right),$ $N_i=\left(\begin{array}{c}{N}_i^{\left(k\right)}\\ {\stackrel{\&OverBar;}{N}}_i^{(k+1)}\end{array}\right)---\left(2\right)$

K and k+1 represent to be in two adjacent time-slots under the same channel status, Y _i ^(k)Represent the signal that i root reception antenna is received constantly at k,

The conjugation of representing the signal that i root reception antenna is constantly received at (k+1); X _J1 ^(k), X _J2 ^(k)Represent the symbol that first, second secondary transmitting antenna of j user sends constantly at k respectively, N _i ^(k)Represent i root reception antenna at k pairing noise component(s) of the moment,

Represent the conjugation of i root reception antenna at pairing noise component(s) of (k+1) moment;

Λ _IjExpression formula be:

${\mathrm{\&Lambda;}}_{\mathrm{ij}}=\left(\begin{array}{cc}{\mathrm{\&Lambda;}}_{{\mathrm{ij}}_1}& {\mathrm{\&Lambda;}}_{{\mathrm{ij}}_2}\\ {\mathrm{\&Lambda;}}_{{\mathrm{ij}}_2}^{*}& -{\mathrm{\&Lambda;}}_{{\mathrm{ij}}_1}^{*}\end{array}\right)---\left(3\right)$

Λ wherein _Ij, Λ _Ij2The channel fading factor of representing j user's the corresponding i root of first, second root transmitting antenna reception antenna respectively, Λ _Ij1 ^*, Λ _Ij2 ^*Be respectively Λ _Ij1, Λ _Ij2Conjugation;

Multi-user STBC system model can be expressed as:

Claim that Y is the received signal vector, X is for sending signal phasor, and N is a noise vector, wherein Y _i, X _i, N _i, 1≤i≤M is the structure of formula (2) expression;

Claim that Λ is the channel matrix of M user STBC system, wherein each Λ _Ij, 1≤i≤M, 1≤j≤M are the matrix of 2 * 2 Alamouti structure of formula (3) expression; For convenience, we define Λ _IjBe the element of matrix Λ, so Λ is the matrix of M * M;

Step 2: determine the detection order:

Channel matrix when being defined in the i time definite detection order is Λ ⁱSo, Λ ⁱMatrix for M * (M+1-i);

1) divides channel matrix Λ ⁱ:

Divide Λ the i time ⁱMethod: at matrix Λ ⁱCapable and last the row line of inverse i, two lines are with matrix Λ ⁱBe divided into four submatrixs, be made as A respectively, B, C, D still defines Λ here _IjBe an element, and 1≤i≤M, 1≤j≤M+1-i,

Divide Λ when determining the detection order for the first time ⁱAs follows:

Wherein A is the submatrix of (M-1) * (M-1), and B is the submatrix of (M-1) * 1, and C is 1 * (M-1) submatrix, and D is 1 * 1 submatrix;

Divide Λ during the i time definite detection order ⁱAs follows:

Wherein A is the submatrix of (M-i) * (M-i), and B is the submatrix of (M-i) * 1, and C is the submatrix of i * (M-i), and D is the submatrix of i * 1;

2) according to formula

${\mathrm{\&Delta;}}_{k_i}=D-{\mathrm{CA}}^{-1}B---\left(7\right)$

Obtain Δ _KiMatrix, and calculate Δ _KiThe row norm of first row of matrix;

3) reset channel matrix Λ ⁱ:

With channel matrix Λ ⁱFirst row place last row, all the other leu prefaces are that original secondary series is become first row in advance, the 3rd row become secondary series, the rest may be inferred, the channel matrix after obtaining resequencing;

4) repeating step 1), 2), 3), altogether (M+1-i) is inferior, obtains (M+1-i) individual row norm successively, determines the channel matrix Λ of wherein maximum row norm correspondence ⁱArrangement mode, and determine the channel matrix Λ of maximum row norm correspondence ⁱLast be listed as pairing user;

Step 3: demodulation draws the estimated value that step 2 is determined user's transmission signal

Utilize the orthogonality of STBC, can obtain the channel matrix Λ of the row norm correspondence of the maximum that obtains through step 2 ⁱDiagonalizable matrix P, receive vector Y with diagonalizable matrix P premultiplication, obtain following expression:

Z wherein _1:M-i, Z _Ki, ∑ _1:M-iBe intermediate variable, I _{2 (M-i) * 2 (M-i)}Be the unit matrix of 2 (M-i) * 2 (M-i), I _{2i * 2i}Be the unit matrix of 2i * 2i, establish:

$X_{k_i}=\left(\begin{array}{c}{X}_{k_i^1}\\ X_{k_i^2}\\ .\\ .\\ .\\ \stackrel{\&OverBar;}{X_{k_i^{M+1-i}}}\end{array}\right),$ $\tilde{N}=\left(\begin{array}{c}{\tilde{N}}_1\\ {\tilde{N}}_2\\ .\\ .\\ .\\ \stackrel{\&OverBar;}{{\tilde{N}}_M}\end{array}\right)---\left(9\right)$

X _KiExpression detects k _iDuring individual user, by the channel matrix Λ of the row norm correspondence of maximum ⁱThe determined user's to be detected of arrangement mode the transmission signal phasor that puts in order;

The correction noise vector that obtains for P matrix premultiplication noise vector N;

According to formula:

${\hat{X}}_{k_i}=Q\left({\left({\mathrm{\&Delta;}}_{k_i}\right)}^{-1}{Z}_{k_i}\right)---\left(10\right)$

Obtain k _iThe estimated value of individual user's transmission signal

Wherein Q () represents decision function, with (Δ _Ki) ^-1Z _KiValue be mapped to point in the planisphere; So just can demodulate k _iIndividual user's transmission signal;

Step 4: reconstruction signal:

At first, the k that step 3 is obtained _iThe estimated value of individual user's transmission signal

Influence from received signal Y the inside deduction, so obtain Y ':

$Y^{\&prime;}=\left(\begin{array}{c}{Y}_1^{\&prime;}\\ Y_2^{\&prime;}\\ .\\ .\\ .\\ Y_M^{\&prime;}\end{array}\right)=Y-{\hat{X}}_{k_i}$ ${\mathrm{\&Lambda;}}_{k_i}=\left(\begin{array}{c}{Y}_1\\ Y_2\\ .\\ .\\ .\\ Y_M\end{array}\right)-{\hat{X}}_{k_i}\left(\begin{array}{c}{\mathrm{\&Lambda;}}_{{1k}_i}\\ {\mathrm{\&Lambda;}}_{{2k}_i}\\ .\\ .\\ .\\ {\mathrm{\&Lambda;}}_{{\mathrm{Mk}}_i}\end{array}\right)---\left(11\right)$

Λ k wherein _iBe initial channel matrix Λ k in the formula (4) _iRow;

Secondly, rebuild the residual signal model: renewal Y is Y '; From Λ ⁱIn remove initial channel matrix Λ k _iRow, i.e. Λ _Ki, upgrade channel matrix Λ ⁱBe Λ ^I+1:

Step 5: repeating step 2,3,4, altogether (M-1) is inferior, will come out than (M-1) the individual user's of high s/n ratio correspondence transmission signal demodulation;

Step 6: demodulation last, i.e. the user's that signal to noise ratio is minimum transmission signal:

When remaining last user, expression formula is arranged:

$Y_{k_M}={\mathrm{\&Lambda;}}_{k_M}{X}_{k_M}+N_{k_M}---\left(13\right)$

Y wherein _KMBe the received signal vector after deduction detected (M-1) individual user's the influence, Λ _KMK for initial channel matrix Λ _MRow, X _KMBe last user's transmission signal, N _KMThe noise vector of correspondence when detecting last user;

According to formula:

${\hat{X}}_{k_M}=Q\left({\left({\mathrm{\&Lambda;}}_{k_M}\right)}^{-1}{Y}_{k_M}\right)---\left(14\right)$

Get to the end, i.e. k _MThe estimated value of individual user's transmission signal

Wherein Q () is the decision function in the formula (10), so just can demodulate last user's transmission signal;

Through after the above step, just can realize detection to multi-user STBC system.

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