CN100388645C

CN100388645C - Pre-coding method and device for improving V-BLAST detection performance

Info

Publication number: CN100388645C
Application number: CNB2004100667609A
Authority: CN
Inventors: 杨红卫
Original assignee: Alcatel Lucent Shanghai Bell Co Ltd
Current assignee: Nokia Shanghai Bell Co Ltd
Priority date: 2004-09-28
Filing date: 2004-09-28
Publication date: 2008-05-14
Anticipated expiration: 2024-09-28
Also published as: CN1756119A

Abstract

The present invention provides a pre-encoding method in a multi-antenna system based on V-BLAST technology, which comprises the following steps: a channel matrix H fed by a reverse channel is received; the singular value of the matrix is decomposed according to a formula * H=U. D. V< + >* so as to obtain a unitary matrix V and a diagonal matrix D which is the diagonal matrix comprising singular values; + represents Hermitian transposition; the Hermitian transposition matrix of the matrix V and the matrix D is calculated so as to obtain a matrix V< + > and a matrix D< + >; the matrix multiplication operation is carried out to generate a code generation matrix X=V. D < + >. V< + >; the matrix X generated by the codes encodes the input modulation symbol vector a so as to obtain and output an encoding symbol vector b=X. a=V. D < + >. V< + >. a. After the pre-encoding is adopted, the equivalent space sub-channel has the same receiving power, and thereby, the capacity of the space relative channel is effectively increased. Compared with the existing pre-treatment and after-treatment proposal based on the channel singular value decomposition, the present invention obviously improves the performance of the traditional V-BLAST system, and the hardware cost of a receiver is eliminated.

Description

A kind of method for precoding and device that improves V-BLAST detection performance

Technical field

The present invention designs method for precoding and the device that a kind of V-BLAST of improvement (Vertical-Bell LaboratoriesLayered Space-Time, vertical-structure during dblast) detects performance.This V-BLAST of improvement detects the method for precoding of performance and installs in the multiaerial system that can be applied to based on the V-BLAST technology.

Background technology

Multiaerial system capacity and number of transmit antennas based on the V-BLAST technology are linear, can obtain very high spectrum efficiency under the condition of not sacrificing extra bandwidth and transmitted power, thereby are subjected to extensive concern.Traditional V-BLAST technology adopts identical modulation system and transmitted power, send independently data in each transmitting antenna unit, receiving terminal adopts detection algorithm ([1] G.D.Golden based on the continuous Interference Cancellation of optimal sequencing, C.J.Foschini, R.A.Valenzuela and P.W.Wolniansky.Detectionalgorithm and initial laboratory results using V-BLASTspace-time communication architecture.Electronics Letters, Vol.35, No.1,7th January 1999.).Independently under the multidiameter fading channel, traditional V-BLAST technology has obtained good performance in the space.Yet, under the multidiameter fading channel of space correlation, stronger spatial coherence has reduced the signal to noise ratio of several equivalent space subchannels of space correlation channel, thereby reduced channel capacity ([5] Da-Shan Shiu, Gerard J.Foschini, Michael J.Gans, etc.Fading correlationand its effect on the capacity of multi-element antenna systems.IEEE Trans on Commu., Vol.48, No.3, March 2000, pp.502-513.) if. transmitting terminal still sends data with multiplexing each space channel of higher rate, and receiving terminal will be difficult to recover error code occurs in the data of the subspace of equal value of low signal-to-noise ratio Channel Transmission.These error codes are constantly propagated between layer at the layer of V-BLAST, cause bit error rate performance ([2] the Cong Shen that seriously descends, Ha iruo Zhang, Lin Dai and Shidong Zhou.Detection algorithm improving V-BLAST performance over errorpropagation.Electronics Letters, Vol.39, No.13,26th June2003.).Therefore, improving V-BLAST is to utilize multiaerial system to improve the important topic that power system capacity need face in the performance of space correlation channel.

In disclosed document, it is Guaranteed that the channel singular value decomposition method has been applied to the speed and the power of multiaerial system.Document [3] passes through at the pretreatment unit of transmitting terminal and the post-processing unit diagonalization space correlation fading channel matrix of receiving terminal, thereby the design of the speed of making and power division is more convenient.Therefore yet this method does not change the signal to noise ratio of the equivalent space subchannel of space channel, can not improve the performance of modulation system and transmitted power V-BLAST when constant.The method of channel singular value decomposition also is widely used in ([4] Young-Doo Kim Inhyoung Kim in the Adaptive Modulation of multiaerial system, Jihoon Choi, etc.Adaptive modulation for MIMO systems with V-BLAST detection.Vehicular Technology Conference, 2003, VTC 2003-Spring, The57th IEEE Semiannual, Vol.2,22-25, April 2003.).

The techniques described herein adopt the method for channel singular value decomposition, according to the equivalent space subchannel etc. the received power principle designed a kind of new method for precoding and device, improved the performance of the V-BLAST of fixed modulation mode and transmitted power under the space correlation fading channel well.

Under the space correlation fading channel, the V-BLAST data transmission scheme of transmission rate and power invariability has two kinds.A kind of is that transmitting terminal and receiving terminal do not adopt any traditional V-BLAST[1 that handles at the space channel correlation], when being based on channel matrix singular value decomposition empty, handles another kind V-BLAST scheme ([3] Jeongseok Ha, Apurva N.Mody, JoonHyun Sung, etc.LDPC-coded OFDM with Alamouti/SVD diversitytechnique.Wireless Personal Communications, vol.23, No.1, October 2002, pp.183-194 (12)).

Based on the block diagram of the multiaerial system of traditional V-BLAST technology as shown in Figure 1, be example with 44 systems of receiving among the figure.

Suppose that there are M transmitting antenna Tx and N reception antenna Rx in general V-BLAST system, wherein, N 〉=M.Source bits stream 1 produces the stream of modulation symbols of serial through digital modulator 2.Be converted to parallel transmission symbolic vector a=(α through vector coding device 3 then ₁, α ₂..., α _M) ^TIn a symbol time interval, transmitting antenna sends symbolic vector to spatial fading channel H with the identical power of single antenna.V-BLAST detector 4 based on the continuous symbol Interference Cancellation of optimal sequencing detects the symbolic vector that receives, and produces the estimated value that sends symbolic vector.Then, send digital demodulator 5 demodulation.

Handle the V-BLAST system block diagram as shown in Figure 2 during based on channel matrix singular value decomposition empty.The singular value decomposition of channel matrix H is

H=UDV ⁺(formula-1)

Wherein, U and V are unitary matrice, and D is the diagonal matrix that comprises the H singular value ,+expression Hermitian transposition.In Fig. 2, send to the space correlation channel after the transmission symbolic vector process V unitary transformation.Receiving terminal is through post-processing unit U ⁺After, send V-BLAST detector 4 to detect and digital demodulator 5 demodulation.

Described according to document [5], suppose that channel is smooth, quasi-static space correlation rayleigh fading channel, transmitting antenna adopt constant power to send, and total transmitted power is ρ, and then the capacity of multiaerial system is the capacity sum of all M a single aerial systems of equal value, promptly

C = Σ_{k = 1}^{M} \log_{2} (1 + \frac{ρ}{N_{α}} \cdot ϵ_{k}^{2})

(formula-2)

Wherein, ε _kIt is the singular value of H.Correspondingly, ε _k ²It is the channel gain of equivalent space subchannel.

The statistical model of typical space correlated channels H can be described [5] with following formula:

H=Ψ _RH _wΨ _T(formula-3)

Wherein, Ψ _RAnd Ψ _TThe half-phase that is reception antenna and transmitting antenna respectively closes matrix, H _wIt is space independence rayleigh fading channel matrix.

Be subjected to the distance between the bay and the influence of scattering environments, the spatial fading channel has certain spatial coherence.This spatial coherence will influence ε _k, k=1 ..., the numeric distribution of M, thus influence the capacity of equivalent space subchannel.When channel has stronger correlation, ε _k, k=1 ..., the numeric distribution of M is seriously unbalance, and the singular value difference of maximum singular value and minimum is up to tens of decibels.

For traditional modulation system in [1] and the constant V-BLAST system of transmitted power, minimum channel gain will seriously reduce received signal to noise ratio, thereby a large amount of flase drop symbols appear in the symbol that causes high rate data transmission, and in the continuous Interference Cancellation process of V-BLAST, cause error propagation, the severe exacerbation performance.

For in [3] based on channel matrix singular value decomposition empty the time handle the V-BLAST scheme, send symbolic vector and be equivalent to through the channel matrix between the receiving symbol vector of reprocessing

H _*=U ⁺HV (formula-4)

Wherein, H _*Be the equivalent channels matrix of V-BLAST, it will directly influence the detection performance of V-BLAST.Bring formula-1 into formula-4, put in order

H _*=D (formula-5)

Obviously, the preliminary treatment of transmitting terminal and the reprocessing of receiving terminal have made things convenient for the design of further speed and power control with the channel diagonalization.Yet distributing through the singular value of the multi-antenna channel matrix of preliminary treatment and reprocessing changes, and therefore this method can not be improved the performance of the constant V-BLAST of modulation system and transmitted power.

Summary of the invention

The singular value decomposition through pretreated spatial channel matrix is not shown in (formula-1).

Wherein,

D = [\begin{matrix} d_{11} & 0 & . . . & 0 \\ 0 & d_{22} & . . . & . . . \\ . . . & . . . & . . . & 0 \\ 0 & . . . & 0 & d_{MN} \end{matrix}]

(formula-6)

After making the equivalent space associated sub-channels through transmitting terminal pretreatment unit x, each subchannel has identical received power, i.e. H _*=HX is after singular value decomposition, and diagonal matrix is unit matrix I, makes

HX=UIV ⁺(formula-7)

Can solve:

X=VD ⁺V ⁺(formula-8)

With (formula-2) serves as that the sign indicating number generator matrix is encoded to sending code sign a, can obtain coding vector b, the parallel then spatial fading channel that sends to.Fig. 3 has provided the V-BLAST system block diagram based on spatial pre-coding that this paper proposes.

Source bits stream 1 produces the stream of modulation symbols of serial through digital modulator 2.Be converted to parallel transmission symbolic vector a=(α through vector coding device 3 then ₁, α ₂..., α _M) ^T, and send spatial pre-coding device 9, encode output encoder vector b=Xa=VD according to the coding generator matrix of (formula-8) ⁺V ⁺A.In a mark space, transmitting antenna sends coding vector b to spatial fading channel H with the identical power of single antenna.V-BLAST detector 4 based on the continuous symbol Interference Cancellation of optimal sequencing detects the symbolic vector that receives, and produces the estimated value of the coded identification vector that sends.Then, send digital demodulator 5 demodulation.

Through after the above-mentioned precoding, the channel matrix that sends between symbolic vector a and the V-BLAST reception vector is equivalent to

H _*=HVD ⁺V ⁺(formula-9)

(formula-1) brought into following formula, put in order

H _*=UIV ⁺(formula-10)

Obviously, through behind the above-mentioned spatial pre-coding, the equivalent space subchannel has identical received power, has improved the capacity of space correlation channel effectively.Compare with the reprocessing scheme with existing preliminary treatment based on the channel singular value decomposition, the pre-coding apparatus of this programme design can obviously improve the performance of the V-BLAST system of traditional speed and power invariability, and has eliminated the hardware spending that brings to receiver.

Description of drawings

Quote and the accompanying drawing of forming a specification part shows embodiments of the present invention at this, and explain the present invention in conjunction with following illustrated example ground.

Fig. 1 represents the multiaerial system block diagram based on V-BLAST;

Fig. 2 handles the V-BLAST system block diagram when representing based on channel matrix singular value decomposition empty;

Fig. 3 represents the system block diagram of the spatial pre-coding V-BLAST among the present invention;

Fig. 4 represents according to spatial pre-coding system block diagram of the present invention;

The performance that V-BLAST correlated channels a little less than the space is received in 44 of Fig. 5 (a) expressions compares;

44 of Fig. 5 (b) expressions are received V-BLAST and are compared in the performance of space strong correlation channel;

The performance that V-BLAST correlated channels a little less than the space is received in 22 of Fig. 5 (c) expressions compares;

22 of Fig. 5 (d) expressions are received V-BLAST and are compared in the performance of space strong correlation channel.

Embodiment

Specifically describe enforcement of the present invention below in conjunction with accompanying drawing.

Fig. 4 has provided the complete system block diagram of spatial pre-coding V-BLAST.At transmitting terminal, the information bit code stream of source encoder 41 outputs forms modulation symbol vector a through digital modulator 2 and string and after changing 42, and send precoder 9 codings.Precoder 9 is encoded to modulation symbol vector a according to the channel matrix of backward channel feedback, output encoder vector b, and form Frame, with the multiplexing identical transmitting antenna of pilot channel.Each transmitting antenna unit sends data and pilot tone with identical transmitted power in forward channel 53.At receiving terminal, the reception data of pilot channel are used to estimate channel matrix, and auxiliary V-BLAST detector 4 carries out the detection of next Frame, and is used for the precoding of next Frame to transmitting terminal by the backward channel feedback channel matrixes.

Simultaneously, the reception data of data channel send the V-BLAST detector 4*V-BLAST detector channel matrix that 4 bases are pre-estimated to sending symbol detection, the transmission symbolic vector that generation is estimated, and process and string conversion send digital modulator 5 to separate 44 decodings of mediation source decoder.

The course of work of contrive equipment as herein described is as follows:

Step 1: receive the channel matrix H of backward channel feedback, the row matrix of going forward side by side singular value decomposition obtains unitary matrice V shown in (formula-1) and diagonal matrix D;

Step 2: the Hermitian transposed matrix of compute matrix V and D obtains matrix V ⁺And D ⁺

Step 3: carry out the matrix multiplication operation, produce sign indicating number generator matrix X=VD ⁺V ⁺

Step 4: use the sign indicating number generator matrix that the modulation symbol vector a that imports is encoded, obtain coded identification vector b=Xa=VD ⁺V ⁺A, and output.

The precoder 9 that this paper proposes can guarantee that multiaerial system equivalent space subchannel has identical received power, improves the capacity of space correlation channel effectively under the space correlation fading channel.Be used in combination with the V-BLAST technology, can make V-BLAST, when obtaining high spectral efficiency, obtain good performance improvement with fixing speed and transmitted power transmission data.

This paper is by the above-mentioned performance improvement of Computer Simulation checking.

Simulated conditions:

Modulator/demodulator: 16QAM

Backward channel: error free, no time delay feedback channel

Forward channel: flat fading, quasi-static space correlation channel.Spatial correlation matrix produces according to document [5], and wherein, the angle spread of transmitter received signal is 5 degree, and the average angle of arrival is 0 degree, and distance is 4 times of wavelength between weak antenna element when relevant, and distance is a half-wavelength between the antenna element during strong correlation, no crosscorrelation.

Channel estimating: desirable channel estimating

Dual-mode antenna number: receive for 22 and 44 receipts

V-BLAST detector: MMSE detects

Signal to noise ratio: the total received power of each reception antenna and noise power ratio.

The spatial pre-coding V-BLAST scheme that contrast scheme: this paper proposes, traditional V-BLAST detection scheme, the scheme that the space preprocess method that decomposes based on channel SVD combines with V-BLAST.

The performance that V-BLAST correlated channels a little less than the space is received in 44 of Fig. 5 (a) expressions compares.44 of Fig. 5 (b) expressions are received V-BLAST and are compared in the performance of space strong correlation channel.The performance that V-BLAST correlated channels a little less than the space is received in 22 of Fig. 5 (c) expressions compares.22 of Fig. 5 (d) expressions are received V-BLAST and are compared in the performance of space strong correlation channel.

Among the figure, solid line is the performance of the spatial pre-coding V-BLAST that this paper proposes, and the dotted line of band "+" number be the performance of the V-BLAST in [1], be with " ^*" number dotted line be in [3] based on channel matrix singular value decomposition empty the time handle the performance of V-BLAST scheme.No matter relatively can obviously find out from the performance of Fig. 5, be under weak correlated channels or strong correlation channel, and the precoding V-BLAST that this paper proposes has all obtained tangible performance improvement under same frequency spectrum efficient.Further, if use actual chnnel coding, performance improvement will be more obvious.

The technical scheme that this paper proposes relatively is fit to time division multiplex system and slow fading channel and uses.At present, at HSDPA (High-Speed Downlink Packet Access, high-speed downlink packet inserts) about closed-loop MIMO (Multiple Input Multiple Output, multiple-input and multiple-output) in the motion, the expense that increases reverse channel resources almost is the cost that all motions all need be paid.Therefore, the technical scheme that this paper proposes has obtained tangible performance improvement under the situation that increases the backward channel expense that can tolerate and transmitter implementation complexity, have good application prospects.

Claims

1. one kind based on the method for precoding in the multiaerial system of V-BLAST technology, it is characterized in that may further comprise the steps:

Receive the channel matrix H of backward channel feedback, and according to H=UDV ⁺Carry out Singular Value Decomposition Using, obtain unitary matrice V, U and diagonal matrix D, D is the diagonal matrix that comprises the H singular value ,+expression close conjugate transpose in distress,

The in distress close associate matrix of compute matrix V and D obtains matrix V ⁺And D ⁺

Carry out the matrix multiplication operation, produce sign indicating number generator matrix X=VD ⁺V ⁺

Use sign indicating number generator matrix X that the modulation symbol vector a of input is encoded, obtain coded identification vector b=Xa=VD ⁺V ⁺A, and output.

2. according to the method for claim 1, it is characterized in that

Before according to sign indicating number generator matrix coded modulation symbolic vector a, modulation symbol vector a is formed through digital modulation and string and after changing by source bits stream.

3. according to the method for claim 1, it is characterized in that forming Frame, data channel and the multiplexing identical transmitting antenna of pilot channel by coded identification vector b.

4. according to the method for claim 1, it is characterized in that each transmitting antenna unit sends data and pilot tone with identical transmitted power in forward channel.

5. according to the method for claim 1, the reception data that it is characterized in that pilot channel are used to estimate channel matrix, detect with the auxiliary V-BLAST that carries out next Frame, and give transmitter with the estimated channel matrix feedback, to be used for the precoding of next Frame by backward channel.

6. according to the method for claim 5, it is characterized in that according to the channel matrix of pre-estimating the reception data of data channel being carried out V-BLAST detects, the transmission symbolic vector of produce estimating, and described transmission symbolic vector carried out and go here and there conversion, digital demodulation and decoding.

7. a pre-coding system that is used for V-BLAST technology multiaerial system is characterized in that

This system comprises source encoder, digital modulator, string and conversion equipment, pre-coding apparatus and transmitting antenna at transmitting terminal, comprise reception antenna, channel estimator, V-BLAST detector and go here and there conversion equipment, digital demodulator and source decoder at receiving terminal

This pre-coding apparatus carries out precoding to the modulation symbol vector from string and conversion equipment, and this pre-coding apparatus receives the channel matrix H of backward channel feedback, and according to H=UDV ⁺Carry out Singular Value Decomposition Using, obtain unitary matrice V, U and diagonal matrix D, D is the diagonal matrix that comprises the H singular value ,+expression close conjugate transpose in distress; The in distress close associate matrix of compute matrix V and D obtains matrix V ⁺And D ⁺Carry out the matrix multiplication operation, produce sign indicating number generator matrix X=VD ⁺V ⁺Use sign indicating number generator matrix X that the modulation symbol vector a of input is encoded, obtain coded identification vector b=Xa=VD ⁺V ⁺A, and export with transmitting antenna.

8. according to the pre-coding system of claim 7, it is characterized in that

At transmitting terminal, behind the message bit stream process digital modulator and string and conversion equipment of source encoder output, form modulation symbol vector a.

9. according to the pre-coding system of claim 7, it is characterized in that the coded identification vector b of pre-coding apparatus output forms Frame, data channel and the multiplexing identical transmitting antenna of pilot channel.

10. according to the pre-coding system of claim 7, it is characterized in that each transmitting antenna unit sends data and pilot tone with identical transmitted power in forward channel.

11. pre-coding system according to claim 9, it is characterized in that at receiving terminal, channel estimator utilizes the reception data estimation channel matrix of pilot channel, carry out the detection of next Frame with auxiliary V-BLAST detector, and the estimated channel matrix feedback is used for the precoding of next Frame to pre-coding apparatus by backward channel.

12. pre-coding system according to claim 10, it is characterized in that reception data for data channel, the V-BLAST detector carries out the V-BLAST detection according to the channel matrix of pre-estimating to receiving data, produce the transmission symbolic vector of estimating, this sends symbolic vector process and the conversion of string conversion equipment, and digital demodulator is separated the decoding of mediation source decoder.