CN101567765A - Distribution type space-time pre-coding transmission method based on channel angle domain information - Google Patents

Abstract

The invention discloses a distribution type space-time pre-coding transmission method based on channel angle domain information. A receiving terminal feeds back the channel angle domain information estimated by the channel comprising the average incidence angle, angle extension and normalization receiving antenna distance, to a transmitting terminal and after receiving the feedback information, the transmitting terminal firstly constructs the statistical information of the channel comprising the mean and correlation matrix and then designs the best pre-coding matrix using the information design and performing the pre-treatment of the space-time code word designed in advance. The distribution type space-time pre-coding transmission method based on channel angle domain information can obtain the more accurate statistical information of the channel and reduce the required feedback amount.

Description

Distribution type space-time pre-coding transmission method based on channel angle domain information

Technical field

The present invention relates to wireless communication field, relate in particular to a kind of distribution type space-time pre-coding transmission method based on channel angle domain information.

Background technology

As a kind of special multiaerial system, distributing antenna system (DAS) is distributed in each antenna element in the whole sub-district, and they are coupled together with optical fiber or microwave and CPU, guaranteed the independence between transmitting antenna so on the one hand, simultaneously because R-T unit is separated with treatment system, like this can be so that system have very strong extensibility, and can reduce the construction cost of system.Compare with traditional centralized multiaerial system, distributed system can further improve system throughput, enhancing transmission reliability, minimizing transmitting power and expand the coverage area.Especially, access mode compatibilities such as distributing antenna system and existing TDMA, FDMA and CDMA, and be applicable to wireless communication technology standards such as 2G, 3G, Wi-Fi and WiMax, so it has good application prospects.

Distributing antenna system can also utilize distributed Space Time Coding to obtain to transmit and receive diversity, but Space Time Coding can not obtain the array gain of system except intrinsic grand diversity.Studies show that, if can obtain all or part of channel information at transmitting terminal, and code word is carried out preliminary treatment when utilizing these information to sky, and code word can be done adaptive variation along with channel fluctuation when making these skies, just can further improve the performance of system.Current since the channel quantitative method of distributed system that is that all right is ripe, main day this mode of line options of utilizing is carried out preliminary treatment.People such as the Han Shuanfeng of Tsing-Hua University are target with the minimizing disruption probability in " Outage Probability BasedOptimal Transmission of Space Time Block Codes over Correlated DistributedAntenna " literary composition, propose a kind of antenna selecting plan of the best, and provided the corresponding power allocation strategy.

In recent years, many documents propose to utilize the statistical information of channel to design pre-coding matrix, and owing to channel statistical information does not change with the fluctuation of channel, so it has higher reliability than feedback channel prompting message.In the document in front, the statistical information of channel, comprise channel average and autocorrelation matrix, the main utilization realizes that to instantaneous channel getting time average replaces statistical average, this method only just has enough accuracy when a large amount of channel of feedback is realized, this will increase the feedback quantity of system greatly.On the other hand, there be limited evidence currently of has documents to utilize statistical information to design the awane pre-coding matrix design problem of Ricean, particularly the influence that designs about Ricean K factor pair code word.

Summary of the invention

The objective of the invention is for solve above-mentioned each scheme neutral can be low, feedback quantity is big, the channel statistical information precision is not high enough and seldom relate to problems such as Ricean pre-coding matrix design on the downside, proposes a kind of distribution type space-time pre-coding transmission method based on channel angle domain information.

The objective of the invention is to be achieved through the following technical solutions, a kind of distribution type space-time pre-coding transmission based on channel angle domain information comprises the steps:

1) receiving terminal obtains the sighting distance component incidence angle corresponding to each transmitting antenna by channel estimating

, the average incidence angle θ of non line of sight component _m, angle spread σ _m ², normalization reception antenna distance, delta _rWith K factor equal angles domain information, and they are fed back to transmitting terminal;

2) after transmitting terminal is received feedback information, according to channel average and channel autocorrelation matrix construction method, obtain corresponding channel average H and channel autocorrelation matrix ∑ respectively based on angle domain information;

3) if K=0, then channel H is Rayleigh fading, if at this moment the emission signal to noise ratio then adopts single-antenna power apportion design design pre-coding matrix less than 10dB, if the emission signal to noise ratio, then adopts average power allocation method design pre-coding matrix greater than 10dB;

4) still it if at this moment the emission signal to noise ratio is less than 10dB, then adopts simple beam method design pre-coding matrix less than 20 if K is not equal to zero, if the emission signal to noise ratio, then adopts average power allocation method design pre-coding matrix greater than 10dB;

5) if K, utilizes the precoding design method design pre-coding matrix based on singular value decomposition greater than 20 o'clock;

6) after obtaining pre-coding matrix, transmitting terminal during to the distributed orthogonal space that designs code word carry out preliminary treatment, then it is launched, receiving terminal to receive empty the time code word carry out maximum likelihood decoding, code word when recovering sent empty.

Further, described channel average construction method based on angle domain information is:

Wherein, H ^(m)Be the m row of channel average H, $a_m=d_m^{-4}$ Be path loss, d _mBe the distance of m transmit antennas to receiving terminal, f _cBe carrier frequency, c represents the light velocity,

N _tBe number of transmit antennas.

Further, described channel autocorrelation matrix construction method based on angle domain information is: the channel autocorrelation matrix can be expressed as a N _tN _r* N _tN _rBlock diagonal matrix $\mathrm{\Σ}=\mathrm{diag}\{{\mathrm{\Σ}}^{\left(1\right)}...{\mathrm{\Σ}}^{\left(N_t\right)}\},$ ∑ wherein ^(m)Be the reception antenna autocorrelation matrix corresponding to the m transmit antennas, N _rBe the reception antenna number.∑ ^(m)The capable n column element of l ∑ _{L, n} ^(m)The coefficient correlation of representing l and n root reception antenna, it can calculate by following formula:

${\mathrm{\&Sigma;}}_{l,n}^{\left(m\right)}=a_{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="A20091009927600102.png,A20091009927600111.png"\; state="\{\{state\}\}">m</figure-callout>}}^2\exp (-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A20091009927600102.png,A20091009927600111.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}|l-n\left|{\mathrm{\&Delta;}}_r\cos \left({\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_m\right)\right)\exp (-\frac{1}{2}{\left(2\mathrm{\&pi;}\right|l-n\left|{\mathrm{\&Delta;}}_r\sin \left({\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_m\right){\mathrm{\&sigma;}}_m\right)}^2)$

Further, described single-antenna power apportion design is: give the antenna of channel gain maximum, i.e. pre-coding matrix F=diag{0 transmit power allocations ... 1 ... 0}, wherein the position at 1 place can be determined by following formula:

$i=\arg \underset{1\&le;i\&le;N_t}{\max }\mathrm{tr}\left({\mathrm{\&Sigma;}}^{\left(i\right)}\right)$

Tr (∑ wherein ⁽ⁱ⁾) expression asks the matrix ∑ ⁽ⁱ⁾Mark.

Further, described average power allocation method is: give all transmitting antennas the transmitting power mean allocation, promptly pre-coding matrix is $F=\frac{1}{\sqrt{N_t}}U,$ Wherein U is any N _t* N _tUnitary matrice.

Further, described simple beam power power division method is: give the launching beam of channel gain maximum transmit power allocations, promptly pre-coding matrix is F=V ^(k)U, wherein V ^(k)Be the pairing right singular value vector of the maximum singular value of channel average H, U is any N _t* N _tUnitary matrice.

Further, described pre-coding matrix design method based on characteristic value decomposition is: H carries out singular value decomposition QDV with the channel average ^H, then pre-coding matrix is F=VU, wherein U is any N _t* N _tUnitary matrice.

The beneficial effect that the present invention has is: the present invention utilizes channel angle domain information, construct the average and the autocorrelation matrix of channel, and obtained the air time precoding matrix on this basis, as long as this method is because the angle domain information of feedback channel, can effectively reduce the feedback quantity of system, on the other hand, it is more accurate than the channel information that utilized time average to obtain originally, therefore can improve the performance of system.In addition, the sub best pre-coding matrix method for designing when this patent has provided Rayleign and Ricean decline respectively, this method can effectively be hanged down the complexity of design when keeping systematic function.In addition, the present invention gives the pre-coding matrix method for designing of K factor when higher, and this pre-coding matrix can asymptoticly be obtained the upper limit of systematic function.

Description of drawings

Fig. 1 is the entire system block diagram;

Fig. 2 is when adopting different air time precodings to transmit, the comparison diagram of system's error sign ratio (SER) performance;

When Fig. 3 is different path loss, the comparison diagram of system's error sign ratio (SER) performance;

Fig. 4 is different reception antennas when counting, the comparison diagram of system's error sign ratio (SER) performance;

When Fig. 5 is different normalization antenna distances (NAS), the comparison of system's error sign ratio (SER) performance;

When Fig. 6 is the different Ricean K factor, the comparison diagram of system's error sign ratio (SER) performance.

Embodiment

Describe the present invention below with reference to the accompanying drawings in detail, it is more obvious that purpose of the present invention and effect will become.

Distribution type space-time pre-coding transmission method based on channel angle domain information of the present invention comprises the steps:

1) receiving terminal obtains the sighting distance component incidence angle corresponding to each transmitting antenna by channel estimating

, the average incidence angle θ of non line of sight component _m, angle spread σ _m ², normalization reception antenna distance, delta _rWith K factor equal angles domain information, and they are fed back to transmitting terminal;

Fig. 1 is a N _r* N _tDistributing antenna system, wherein base station (BS) has N _tRoot antenna (being access point), be distributed in the whole sub-district, and their same CPU (CPU) are coupled together with optical fiber or microwave, each access point only is responsible for the transmitting-receiving of signal, all signal processing all realize in CPU, the extensibility that helps system so at any time can be according to the requirement increase of system or the number of minimizing access point.At mobile client (MU), dispose N _rThe centralized antenna of root.

Before the data that send required transmission, transmitting terminal sends one section training sequence earlier, and receiving terminal utilizes these training sequences, estimates the average incidence angle θ of each transmitting antenna institute respective signal _mWith angle spread σ _m ², m=1 ..., N _t, and them with normalization reception antenna distance, delta _rFeed back to transmitting terminal together with the Ricean decline K factor.

2) after transmitting terminal is received feedback information, according to channel average and channel autocorrelation matrix construction method, obtain corresponding channel average H and channel autocorrelation matrix ∑ respectively based on angle domain information;

Generally, channel matrix H can be expressed as $H=\sqrt{\frac{K}{K+1}}\stackrel{\&OverBar;}{H}+\sqrt{\frac{1}{K+1}}\tilde{H},$ Wherein H represents the standing part of channel, i.e. channel matrix,

Be the variable part of channel, it is caused by multipath fading.We consider the variable part of channel earlier According to the electromagnetic propagation principle, by the signal of antenna m emission, after the scattering object scattering, with the form arrival receiving terminal of multipath, its average incidence angle is θ _m, angle spread is σ _m ², like this,

Autocorrelation matrix can be expressed as

Wherein, ∑ ^(m)Be the reception antenna autocorrelation matrix with respect to antenna m, its capable n column element of l can be expressed as ${\mathrm{\&Sigma;}}_{l,n}^{\left(m\right)}=a_{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="A20091009927600102.png,A20091009927600111.png"\; state="\{\{state\}\}">m</figure-callout>}}^2\exp (-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A20091009927600102.png,A20091009927600111.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}|l-n\left|{\mathrm{\&Delta;}}_r\cos \left({\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_m\right)\right)\exp (-\frac{1}{2}{\left(2\mathrm{\&pi;}\right|l-n\left|{\mathrm{\&Delta;}}_r\sin \left({\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_m\right){\mathrm{\&sigma;}}_m\right)}^2).$ For channel constant part H, its m row can be expressed as

Wherein, H ^(m)Be the m row of channel average H, $a_m=d_m^{-4}$ Be path loss, d _mBe the distance of m transmit antennas to receiving terminal, f _cBe carrier frequency, c represents the light velocity,

3) if K=0, then channel H is Rayleigh fading, if at this moment launch signal to noise ratio lower (less than 10dB), then adopts single-antenna power apportion design design pre-coding matrix, if emission signal to noise ratio higher (greater than 10dB) then adopts average power allocation method design pre-coding matrix.

In the present invention, the pair-wise error probability with Space Time Coding is that optimization aim designs pre-coding matrix.When channel was the Rayleigh decline, its optimization aim can be expressed as ${\mathrm{<figure-callout\; id="1"\; label="J"\; filenames="A20091009927600102.png,A20091009927600111.png"\; state="\{\{state\}\}">J</figure-callout>}}_1=\det (I+\frac{\mathrm{\&mu;\&gamma;}}{4}{\mathrm{\&Sigma;}}^{1/2}\mathrm{\&Phi;}{\mathrm{\&Sigma;}}^{1/2}),$ Wherein $\mathrm{\&Phi;}=I_{N_r}{\&CircleTimes;\mathrm{FF}}^{*}.$ When emission signal to noise ratio γ hour, to J ₁Carry out Taylor expansion, cast out its higher order term, its optimization aim is reduced to J ₂=tr (∑ ^1/2The Ф ∑ ^1/2), utilize method of Lagrange multipliers to find the solution this optimization problem, can get pre-coding matrix F=diag{0 ... 1 ... 0}, wherein the position at 1 place can be determined by following formula: $i=\arg \underset{1\&le;i\&le;N_t}{\max }\mathrm{tr}\left({\mathrm{\&Sigma;}}^{\left(i\right)}\right),$ Tr (∑ wherein ⁽ⁱ⁾) expression asks the matrix ∑ ⁽ⁱ⁾Mark, promptly transmit power allocations is given that root antenna of channel gain maximum.

When emission signal to noise ratio γ was big, optimization aim can be reduced to J ₂=det (∑ ^1/2The Ф ∑ ^1/2), find the solution this problem, can get pre-coding matrix and be $F=\frac{1}{\sqrt{N_t}}U,$ Wherein U is any N _t* N _tUnitary matrice, promptly give all transmitting antennas the transmitting power mean allocation.

Fig. 2 compares the performance of the air time precoding transmission policy under the Rayleign fade condition, and the pre-coding matrix method for designing that the present invention provides has very low design complexities, but it has very approaching performance with best pre-coding matrix.When Fig. 3 is different path loss, the changes of properties of the air time precoding transmission policy that the present invention proposes, when the path loss between antenna differed big more, the performance of this precoding strategy was good more, and the signal-noise ratio thresholds that two kinds of strategies switch are put off more backward.When Fig. 4 accepts antenna number for difference, the changes of properties of the air time precoding strategy that the present invention proposes, along with the increase of accepting antenna number, the diversity order of passable acquisition is also increased accordingly, and this is that the performance of system is also improved accordingly.When Fig. 5 accepts antenna distance for different normalization, the comparison of systematic function, along with the increase of antenna distance, the coefficient correlation between them constantly reduces, precoding strategy diversity that can obtain and coding gain just increase thereupon like this, so the reliability of system constantly strengthens.

4) if but K is not equal to zero its less (less than 20), if at this moment launch signal to noise ratio lower (less than 10dB), then adopt simple beam method design pre-coding matrix, if emission signal to noise ratio higher (greater than 10dB) then adopts average power allocation method design pre-coding matrix.

When K was not equal to zero, channel was the Ricean decline, and at this moment the optimization aim of system can be expressed as

${\mathrm{<figure-callout\; id="4"\; label="J"\; filenames="A20091009927600102.png,A20091009927600111.png"\; state="\{\{state\}\}">J</figure-callout>}}_4=\frac{\exp (-{\mathrm{vec}}^{*}\left(\mathrm{\&mu;}\right)V_{\mathrm{\&Phi;}}{\left(V_{\mathrm{\&Phi;}}^{*}({\left(\frac{\mathrm{\&mu;\&gamma;}}{4}\mathrm{\&Phi;}\right)}^{-1}+\mathrm{\&Sigma;})V_{\mathrm{\&Phi;}}\right)}^{-1}{V}_{\mathrm{\&Phi;}}^{*}\mathrm{vec}\left(\mathrm{\&mu;}\right))}{\det (I+\frac{\mathrm{\&mu;\&gamma;}}{4}{\mathrm{\&Sigma;}}^{1/2}{\mathrm{\&Phi;\&Sigma;}}^{1/2})}$

When emission signal to noise ratio γ hour, this optimization aim can be reduced to J ₅=tr (HFF ^*H ^*), find the solution this optimization problem, can get pre-coding matrix is F=V ^(k)U, wherein V ^(k)Be the pairing right singular value vector of the maximum singular value of channel average H, U is any N _t* N _tUnitary matrice, promptly transmitting power is all distributed to that wave beam of channel gain maximum.

When γ hour, above-mentioned optimization aim can be reduced to J ₆=det (∑ ^1/2The Ф ∑ ^1/2), find the solution this problem, can get pre-coding matrix and be $F=\frac{1}{\sqrt{N_t}}U,$ Wherein U is any N _t* N _tUnitary matrice, promptly give all transmitting antennas the transmitting power mean allocation.

When Fig. 6 is the different K factor, the comparison of systematic function, as we know from the figure, the air time precoding strategy that adopts the present invention to propose, can obtain more performance than under the Rayleigh fade condition under the Ricean fade condition, and along with the increase of K, obtainable performance gain increases constantly.

5) if when K is big (greater than 20), utilize precoding design method design pre-coding matrix based on singular value decomposition.Since when K is enough big, the variable item of channel

Can ignore, at this moment transmitting terminal almost can be known channel information fully, at this moment, the right singular value matrix that utilizes channel during to sky code word carry out precoding, can obtain maximum performance.

6) after obtaining pre-coding matrix, transmitting terminal during to the distributed orthogonal space that designs code word carry out preliminary treatment, then it is launched, receiving terminal to receive empty the time code word carry out maximum likelihood decoding, code word when recovering sent empty.

Adaptive accidental beam mode selection method of the present invention and system can maximize the capacity from user network minimizing under the prerequisite that main user network is disturbed, thereby significantly improve the spectrum efficiency of system.

Claims (7)

1, a kind of distribution type space-time pre-coding transmission method based on channel angle domain information is characterized in that, comprises the steps:

1) receiving terminal obtains the sighting distance component incidence angle corresponding to each transmitting antenna by channel estimating , the average incidence angle θ of non line of sight component _m, angle spread σ _m ², normalization reception antenna distance, delta _rWith K factor equal angles domain information, and they are fed back to transmitting terminal.

2) after transmitting terminal is received feedback information, according to channel average and channel autocorrelation matrix construction method, obtain corresponding channel average H and channel autocorrelation matrix ∑ respectively based on angle domain information.

3) if K=0, then channel H is Rayleigh fading, if at this moment the emission signal to noise ratio then adopts single-antenna power apportion design design pre-coding matrix less than 10dB, if the emission signal to noise ratio, then adopts average power allocation method design pre-coding matrix greater than 10dB.

4) still it if at this moment the emission signal to noise ratio is less than 10dB, then adopts simple beam method design pre-coding matrix less than 20 if K is not equal to zero, if the emission signal to noise ratio, then adopts average power allocation method design pre-coding matrix greater than 10dB.

5) if K, utilizes the precoding design method design pre-coding matrix based on singular value decomposition greater than 20 o'clock.

6) after obtaining pre-coding matrix, transmitting terminal during to the distributed orthogonal space that designs code word carry out preliminary treatment, then it is launched, receiving terminal to receive empty the time code word carry out maximum likelihood decoding, code word when recovering sent empty.

2, the distribution type space-time pre-coding transmission policy based on channel angle domain information according to claim 1 is characterized in that, described channel average construction method based on angle domain information is:

Wherein, H ^(m)Be the m row of channel average H, $a_m=d_m^{-4}$ Be path loss, d _mBe the distance of m transmit antennas to receiving terminal, f _cBe carrier frequency, c represents the light velocity, N _tBe number of transmit antennas.

3, the distribution type space-time pre-coding transmission policy based on channel angle domain information according to claim 1 is characterized in that, described channel autocorrelation matrix construction method based on angle domain information is: the channel autocorrelation matrix can be expressed as a N _tN _r* N _tN _rBlock diagonal matrix $\mathrm{\&Sigma;}=\mathrm{diag}\{{\mathrm{\&Sigma;}}^{\left(1\right)}...{\mathrm{\&Sigma;}}^{\left(N_t\right)}\},$ ∑ wherein ^(m)Be the reception antenna autocorrelation matrix corresponding to the m transmit antennas, N _rBe the reception antenna number.∑ ^(m)The 1st row n column element ∑ _{L, n} ^(m)The coefficient correlation of representing l and n root reception antenna, it can calculate by following formula:

${\mathrm{\&Sigma;}}_{l,n}^{\left(m\right)}=a_m^2\exp (-j2\mathrm{\&pi;}|l-n\left|{\mathrm{\&Delta;}}_r\cos \left({\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_m\right)\right)\exp (-\frac{1}{2}{\left(2\mathrm{\&pi;}\right|l-n\left|{\mathrm{\&Delta;}}_r\sin \left({\stackrel{\&OverBar;}{\mathrm{\&theta;}}}_m\right){\mathrm{\&sigma;}}_m\right)}^2).$

4, the distribution type space-time pre-coding transmission policy based on channel angle domain information according to claim 1, it is characterized in that, described single-antenna power apportion design is: the antenna of transmit power allocations being given the channel gain maximum, be pre-coding matrix F=diag{0 ... 1 ... 0}, wherein the position at 1 place can be determined by following formula:

$i=\arg \underset{1\&le;i\&le;N_t}{\max }\mathrm{tr}\left({\mathrm{\&Sigma;}}^{\left(i\right)}\right);$

Tr (∑ wherein ⁽ⁱ⁾) expression asks the matrix ∑ ⁽ⁱ⁾Mark.

5, the distribution type space-time pre-coding transmission policy based on channel angle domain information according to claim 1 is characterized in that, described average power allocation method is: give all transmitting antennas the transmitting power mean allocation, promptly pre-coding matrix is $F=\frac{1}{\sqrt{N_t}}U,$ Wherein U is any N _t* N _tUnitary matrice.

6, the distribution type space-time pre-coding transmission policy based on channel angle domain information according to claim 1, it is characterized in that, described simple beam power power division method is: give the launching beam of channel gain maximum transmit power allocations, promptly pre-coding matrix is F=V ^(k)U, wherein V ^(k)Be the pairing right singular value vector of the maximum singular value of channel average H, U is any N _t* N _tUnitary matrice.

7, the distribution type space-time pre-coding transmission policy based on channel angle domain information according to claim 1 is characterized in that, described pre-coding matrix design method based on characteristic value decomposition is: H carries out singular value decomposition QDV with the channel average ^H, then pre-coding matrix is F=VU, wherein U is any N _t* N _tUnitary matrice.

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