CN102710371B - Transmission method using limiting feedback information in multi-antenna two-hop relay system - Google Patents

Abstract

The invention discloses a transmission method using limiting feedback information in a multi-antenna two-hop relay system. The transmission method comprises the following steps: firstly, the system confirms the feedback bit number on two feedback links according to information such as the transmitting power and the antenna numbers of a base station and a relay station, the limited performance loss thresholds, the user antenna numbers and the like, and selects a limited number of multi-antenna users which meet the requirement on the antenna number to wait for receiving the data by adopting a random schedule method; secondly the relay station and each user obtain the channel information from the base station to the relay station and from the relay station to the user through the channel estimation respectively; subsequently the relay station and the user quantize the obtained channel information respectively, and feed back the information to a prior stage through a limited number of bits determined by the system; finally, the base station and the relay station carry out precoding transmission according to the channel information obtained through the feedback respectively. With the adoption of the transmission method, the covering range of a cell of origin is widened effectively; and a system accessible transmission rate which is approximate to ideal channel information condition is obtained.

Description

In many antennas two-hop relaying, utilize the transmission method of Limited Feedback information

Technical field

The present invention relates to the transmission method based on information feedback in a kind of many antennas two-hop relaying, belong to the pre-coding transmission method design field in many antenna relays system.

Background technology

In existing cellular communication system, Cell Edge User is owing to being subject to the strong interference of neighbor cell signal, and it is generally lower that it receives Signal to Interference plus Noise Ratio (SINR), had a strong impact on the communication quality of edge customer, restricting the further lifting of systematic function.In order to address this problem, Recent study personnel attempt introducing relay station in cellular cell, the base station signal of Dui Zhe community carries out being transmitted to Cell Edge User after power enhancing, to improve the signal strength signal intensity of its reception, and then the coverage of expansion cellular cell, reached at the transmission rate of raising whole system.On the other hand, nearly ten years, multi-antenna technology (MIMO) is subject to researcher's extensive concern day by day, a plurality of spatial degrees of freedom that this technology can utilize many antennas of transmitting terminal and receiving terminal to provide, to if having time and frequency resource carry out multiplexing on space, thereby significantly improve the utilization ratio of frequency spectrum resource and the message capacity of system.

Yet, make full use of the spatial degrees of freedom that many antennas provide, make system obtain full spatial multiplexing gain, transmitting terminal need to be known desirable downlink channel condition information.And in practical application scene, no matter be time division duplex (TDD) or Frequency Division Duplexing (FDD) (FDD) system, this prerequisite is all difficult to meet.If system adopts time division duplex (TDD), transmitting terminal can pass through reciprocity principle, at base station estimating uplink channel information the channel information using it as down link.But up link and down link are not full symmetric, thereby in the channel information that obtains by reciprocity of base station, just unavoidably there is evaluated error.If system adopts Frequency Division Duplexing (FDD) (FDD), conventionally by user terminal, carry out estimating down-ward link channel information, then user by feedback link by the feedback of channel information of down link to base station.But in real system, user can feedack amount be limited, user is in order to meet the capacity requirement of feedback link, first channel information is quantized often, then by the excessively limited bit feedback of the information exchange after quantizing to base station, last base station recovers channel information as much as possible according to this feedback information, and this scheme is called as limit bit feedback.Adopt limit bit feedback between the system channel information that causes base station to obtain and real channel information, to have certain quantization error, the size of this quantization error is determined by the capacity of feedback link.Thereby, in many antenna relays system of reality, we need to assess the harmful effect that downlink channel condition information that transmitting terminal knows exists quantization error to cause systematic function, and accordingly Limited Feedback technology is necessarily improved, the system of approaching ideal communication channel information state to obtain can reach transmission rate.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, the transmission method that utilizes Limited Feedback information in a kind of many antennas two-hop relaying is provided, to expand the coverage of cellular cell, and obtain the system approach ideal communication channel information state and can reach transmission rate.

The technical solution used in the present invention is: in a kind of many antennas two-hop relaying, utilize the transmission method of Limited Feedback information, the method comprises the following steps:

1) base station has M root antenna, and relay station and each user have respectively N _tand N _rthe two-hop relaying of root antenna, system is according to transmitting power and the antenna number of base station and relay station, and the information such as the performance loss threshold value limiting and user antenna number, determine relay station to base station and user to the two-stage number of bits of feedback B of relay station ₁and B ₂size:

2) system is according to the antenna number N of relay station _t, in Zhe community, adopt accidental scheduling method to select K many antennas user to wait for transfer of data, to meet N _t=KN _r;

3) when each transmission starts, first relay station carries out channel estimating, obtains base station to the channel information G of relay station; Each user, by channel estimating, obtains relay station to this user's descending channel information H simultaneously _k;

4) relay station carries out singular value decomposition to obtained channel information G, and G=U[∑ 0] [V V ₀] ^h, wherein, U represents unitary matrice, and ∑ represents that diagonal element is the diagonal matrix of the singular value of G, and V represents the front N of another unitary matrice _trow, V ₀the rear M-N that represents this unitary matrice _trow.Relay station according to code word number is existing code book, the column vector of matrix V is quantized, quantized result is designated as V.Then relay station passes through B by the information V after quantizing ₁individual bit feedback is to base station, and base station is carried out precoding transmission according to this information to sending symbol;

5) user k according to code word number is existing code book, to obtained channel information H _kcarry out matrix quantization, quantized result is designated as H _k.Then this user is by the information H after quantizing _kpass through B ₂individual bit feedback is to relay station, and relay station, according to the descending channel information of all user feedbacks, adopts block diagonalization technology to carry out precoding transmission to transmitting symbol.

In many antenna relays system of the present invention, utilize the transmission method of Limited Feedback channel information, require relay station to base station and user to relay station two-stage number of bits of feedback B ₁and B ₂according to following formula, adjust, with assurance system, can reach transmission rate and be scheduled in controlled scope in one compared to the performance loss of ideal situation:

$B_1=\mathrm{Ceil}\left\{(M-1)({\log }_2{P}_2-{\log }_2(M+\frac{N_t}{P_1})+{\log }_2\frac{2T}{N_t(b^{\frac{1}{N_r}}-1)})\right\}$

$B_2=\mathrm{Ceil}\{T{\log }_2{P}_2+T{\log }_2\frac{2A}{N_t(b^{\frac{1}{N_r}}-1)}\}$

Wherein, P ₁and P ₂the transmitting power that represents respectively base station and relay station, the limited loss of energy threshold value of b, Ceil{X} represents to be not less than the smallest positive integral of X, and T and A are provided by following formula respectively:

T=N _t(N _t-N _r)

$A=\frac{N_t}{N_r}\frac{\mathrm{\Γ}\left(\frac{1}{T}\right)}{T}{\left(\frac{1}{T!}\underset{i=1}{\overset{N_r}{\mathrm{\Π}}}\frac{(N_t-i)!}{(N_r-i)!}\right)}^{-\frac{1}{T}}$

Wherein, $\mathrm{\Γ}\left(\mathrm{\α}\right)={\∫}_0^{\∞}{e}^{-t}{t}^{\mathrm{\α}-1}\mathrm{dt}$ Represent gamma function.

Beneficial effect: 1) the inventive method can improve cellular cell edge customer received signal strength, expands cell coverage area, the linear predictive coding mode adopting, and implementation complexity is low, and better performances;

2) in the inventive method according to transmitting power and the antenna number of base station and relay station, and the information such as the performance loss threshold value limiting and user antenna number determines that the way of two-stage number of bits of feedback size can guarantee, for ideal communication channel information state, the performance loss of system is controlled in a limited range, and obtains the system approach ideal situation and can reach transmission rate.

Accompanying drawing explanation

Fig. 1 utilizes the system block diagram of the transmission method of Limited Feedback information in many antennas two-hop relaying of proposing of the present invention;

Fig. 2 knows under different channels information state at transmitting terminal, and system can reach transmission rate and increase with base station and relay station transmitting power the curve chart changing.

Embodiment

Below in conjunction with the drawings and specific embodiments, the invention will be further described:

As shown in Figure 1: specific embodiment of the invention step is as follows:

1) system is according to the transmitting power P of base station and relay station ₁, P ₂and antenna number M, N _t, and the performance loss threshold value and the user antenna that by b, are limited are counted N _retc. information, according to following formula determine relay station to base station and user to the two-stage number of bits of feedback B of relay station ₁and B ₂size:

$B_1=\mathrm{Ceil}\left\{(M-1)({\log }_2{P}_2-{\log }_2(M+\frac{N_t}{P_1})+{\log }_2\frac{2T}{N_t(b^{\frac{1}{N_r}}-1)})\right\}$

$B_2=\mathrm{Ceil}\{T{\log }_2{P}_2+T{\log }_2\frac{2A}{N_t(b^{\frac{1}{N_r}}-1)}\}.$

2) system is according to the antenna number N of relay station _t, in Zhe community, adopt accidental scheduling method to select K many antennas user to wait for transfer of data, to meet N _t=KN _r;

3) when each transmission starts, first relay station carries out channel estimating, obtains base station to the channel information G of relay station, and then, relay station carries out singular value decomposition to obtained channel information G, and G=U[∑ 0] [V V ₀] ^h, wherein, U represents unitary matrice, and ∑ represents that diagonal element is the diagonal matrix of the singular value of G, and V represents the front N of another unitary matrice _trow, V ₀the rear M-N that represents this unitary matrice _trow;

4) relay station according to code word number is existing code book, the column vector of matrix V is quantized, and the information V after quantizing is passed through to B ₁individual bit feedback is to base station, and base station is carried out precoding transmission according to this information to sending symbol;

5) each user, by channel estimating, obtains relay station to this user's descending channel information H _k, then according to code word number be existing code book, to obtained channel information H _kcarry out matrix quantization, and by quantized result H _kpass through B ₂individual bit feedback is to relay station, and relay station, according to the descending channel information of all user feedbacks, adopts block diagonalization technology to carry out precoding transmission to transmitting symbol.

As shown in Figure 2: our predetermined performance loss threshold value is 2bps/Hz, in figure, can find, the scheme of the adjustment two-stage number of bits of feedback that the present invention proposes effectively control channel quantizes the performance loss causing, and fixedly number of bits of feedback will cause in high s/n ratio situation, the sharply deterioration of performance loss.

It should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.In the present embodiment not clear and definite each part all available prior art realized.

Claims (1)

1. a transmission method that utilizes Limited Feedback information in the two-hop relaying of antenna more than, is characterized in that: this transmission method carries out according to the following steps:

1. base station has M transmit antennas, and relay station and each user have respectively N _tand N _rthe two-hop relaying of root antenna, system is according to transmitting power and the antenna number of base station and relay station, and the performance loss threshold value b limiting and user antenna count that these information are determined relay station to base station and user to the big or small B of the two-stage number of bits of feedback of relay station ₁and B ₂; Described number of bits of feedback B ₁and B ₂by following formula, determined, assurance system can reach transmission rate and be scheduled in controlled scope in one compared to the performance loss of ideal situation:

$B_1=\mathrm{Ceil}\left\{(M-1)({\log }_2{P}_2-{\log }_2(M+\frac{N_t}{P_1})+l{\mathrm{og}}_2\frac{2T}{N_t(b^{\frac{1}{N_r}}-1)})\right\}$

$B_2=\mathrm{Ceil}\{T{\log }_2{P}_2+T{\log }_2\frac{2A}{N_t(b^{\frac{1}{N_r}}-1)}\}$

Wherein, P ₁and P ₂the transmitting power that represents respectively base station and relay station, the limited loss of energy threshold value of b, Ceil{X} represents to be not less than the smallest positive integral of X, and T and A are provided by following formula respectively:

T＝N _t(N _t-N _r)

$A=\frac{N_t}{N_r}\frac{\mathrm{\Γ}\left(\frac{1}{T}\right)}{T}{\left(\frac{1}{T!}\underset{i=1}{\overset{N_r}{\mathrm{\Π}}}\frac{(N_t-i)!}{(N_r-i)!}\right)}^{-\frac{1}{T}}$

Wherein, represent gamma function;

2. system is according to the antenna number N of relay station _t, in Zhe community, adopt accidental scheduling method to select K many antennas user to wait for transfer of data, to meet N _t=KN _r, N wherein _rthe antenna number that represents each user;

3. when each transmission starts, first relay station carries out channel estimating, obtains base station to the channel information G of relay station; Each user, by channel estimating, obtains relay station to this user's descending channel information H simultaneously _k;

4. relay station carries out singular value decomposition to obtained channel information G, and G=U[Σ 0] [V V ₀] ^h, wherein, U represents unitary matrice, and Σ 0 represents the diagonal matrix of the singular value that diagonal element is G, and V represents the front N of another unitary matrice _trow, V ₀the rear M-N that represents this unitary matrice _trow, M represents the number of transmit antennas of base station; Relay station according to code word number is existing code book, the column vector of matrix V is quantized, quantized result is designated as then relay station is by the information after quantizing pass through B ₁individual bit feedback is to base station, and base station is carried out precoding transmission according to this information to sending symbol;

5. user k according to code word number is existing code book, to obtained descending channel information H _kcarry out matrix quantization, quantized result is designated as then this user is by the information after quantizing pass through B ₂individual bit feedback is to relay station, and relay station, according to the descending channel information of all user feedbacks, adopts block diagonalization technology to carry out precoding transmission to transmitting symbol.