WO2009079813A1

WO2009079813A1 - A multi-antenna receiving diversity combining method and device with decoding feedback

Info

Publication number: WO2009079813A1
Application number: PCT/CN2007/003506
Authority: WO
Inventors: Jing Zhang; Jia Qiao
Original assignee: Utstarcom Telecom Co., Ltd.
Priority date: 2007-12-10
Filing date: 2007-12-10
Publication date: 2009-07-02
Also published as: CN101861706A

Abstract

A multi-antenna receiving diversity combining method with decoding feedback includes: (1) the multi-antenna receiver sorts each branch by value of signal noise ratio; (2) choosing the branch with the maximum signal noise ratio and demodulating and decoding, if the decode is right, the decode result is output; (3) if the decode is false, the branch with the second maximum signal noise ratio is added to the maximal ratio combining concourse, namely, carrying out maximal ratio combining for the branch with the maximum signal noise ratio and the branch with the subaltern maximum signal noise ratio, and demodulating and decoding, if the decode isright, the decode result is output; (4) if the decode is false, according to the said method, the branch with the third maximum signal noise ratio is added to the maximal ratio combining concourse, until the decode is right, or all branch have participated in the maximal ratio combining.

Description

Multiple antenna with decoding feedback

Method and apparatus for receiving diversity combining

The present invention relates to a method and apparatus for multi-antenna reception diversity combining with decoding feedback, and more particularly to a method and apparatus for multi-antenna reception diversity combining with decoding feedback for a wireless communication system. Background technique

In wireless communication systems, there is deep fading. Deep fading occurs rarely simultaneously during the same time interval on two or more paths, so diversity can reduce the effects of fading. Commonly used antenna diversity has spatial diversity and polarization diversity. If the receiver has multiple antennas that are far enough apart and the fading of the signals they receive are independent of each other, they can be spatially diversity received. When the antenna is separated by more than 10 wavelengths, a better spatial diversity effect is obtained. The receiver can also be +/-45. Or vertical/horizontal dual-polarized antennas for polarization diversity. The receiver obtains the diversity gain by combining two mutually orthogonal electric field component signals.

Commonly used merge processing for multi-antenna receive diversity signals has maximum ratio combining and selective combining. In maximum ratio combining, multiple signals are weighted before combining to achieve optimal performance and in phase. Selective combining is based on the principle that the receiver chooses to receive the best signal from all signals from different branches.

In wireless communication systems, wireless signals are reflected by various objects within the wireless channel, resulting in multipath propagation. Multipath propagation causes intersymbol interference. A common means of eliminating inter-symbol interference is time domain channel equalization. The complexity of the time domain channel equalizer increases as the ratio of the maximum multipath delay to the transmission symbol period increases. When transmitting information at a high symbol rate, the use of a time domain channel equalizer is no longer realistic. OFDM (Orthogonal Frequency Division Multiplexing) decomposes high-rate data streams into multiple low-rate data streams for parallelism The mode is transmitted on multiple subcarriers, since the symbol period of the data stream on each subcarrier is much larger than the original symbol period, thereby alleviating the influence of inter-symbol interference caused by multipath, and no time domain channel equalization is needed. The advantages of OFDM make it gradually replace single-carrier technology for wireless communication systems such as wireless local area networks, digital terrestrial television, and broadband wireless access.

For OFDM systems, the received symbol Yk of the kth subcarrier on the receiving side

Y _k = H _k X _{k +} N _k

Where Xk is the transmitted symbol, Hk is the channel response on subcarrier k, and Nk is additive noise. When Xk is a known pilot sequence, the channel response can be estimated. Under the least squares criterion (LS), the estimated channel response is:

Wherein, refers to a pilot symbol transmitted on the kth subcarrier. In general, the higher the signal-to-noise ratio of ^H k ^{≠ H} , the smaller the error of channel estimation; the lower the signal-to-noise ratio, the larger the error of channel estimation. By interpolating, the channel response on all subcarriers including the data symbols can be estimated. For maximum ratio combining, the maximum ratio of the combined output is

If the weights of the other branches except the one with the best signal quality are forcibly zeroed, they are degraded to selective merge:

Yd _ ^k,i _k

k,mrc― ^Λ where ik represents the branch with the best signal quality.

The output signal of the combiner is sent to the decoder for further processing.

As mentioned earlier, the lower the signal to noise ratio, the greater the error in channel estimation. In maximum ratio In the algorithm, the conjugate of the channel response is used as the weight. Therefore, in the case where a certain branch or some branches are in a low SNR, the performance of the maximum ratio combining is greatly reduced due to the error of channel estimation. , even with a large negative gain. Summary of the invention

The object of the present invention is to provide a method and apparatus for multi-antenna reception diversity combining with decoding feedback, which is compared with the prior art, in the case where a certain branch or some branches are at a low signal to noise ratio, The performance degradation caused by the maximum ratio combining due to the channel response estimation error and the signal to noise ratio estimation error is avoided.

In order to achieve the above object, the multi-antenna receiver of the present invention first arranges the branches in descending order of the estimated values of the signal to noise ratio. Select the branch with the largest signal-to-noise ratio for demodulation and decoding. If the decoding is correct, the decoding result is output. If the decoding is not correct, the branch with the second largest signal to noise ratio is added to the maximum ratio combining set, that is, the branch with the largest signal to noise ratio and the second largest signal to noise ratio is subjected to maximum ratio combining, and then demodulated and decoded. If the decoding is correct, the decoding result is output. If the decoding is not correct, the analogy of the third largest signal-to-noise ratio is added to the maximum ratio combining set until the decoding is correct, or all branches have participated in the maximum ratio combining.

The present invention also provides a receiving diversity combining apparatus for a multi-antenna system with decoding feedback, comprising:

a channel estimation/signal-to-noise ratio estimator for estimating a signal-to-noise ratio of a signal received by each branch of the multi-antenna receiver;

a combiner coupled to the channel estimation/signal-to-noise ratio estimator; and a decoder coupled to the combiner for decoding a signal output by the combiner;

The combiner performs the following actions in combination with the decoder:

(1) The combiner arranges each branch according to an estimated value of a signal to noise ratio;

(2) Select the branch with the largest signal-to-noise ratio for demodulation and decoding, if the decoding is positive Indeed, the decoding result is output;

(3) If the decoding is not correct, the branch with the second largest signal-to-noise ratio is added to the maximum ratio combining set, that is, the branch with the largest signal-to-noise ratio and the second largest signal-to-noise ratio is combined, and then demodulated. Decoding; if the decoding is correct, the decoding result is output;

(4) If the decoding is not correct, the third largest branch of the signal-to-noise ratio is added to the maximum ratio combining set according to the above method until the decoding is correct, or all the branches have participated in the maximum ratio combining.

The receiver of the present invention has great advantages. In the case where the quality of some tributary signals is good and the quality of some tributary signals is not good, the signal-to-noise ratio and channel response estimation error of the branch with poor signal quality are large, and the maximum ratio combining performance is deteriorated. The receiver according to the present invention controls the number of branches participating in the maximum ratio combining according to the decoding feedback to optimize the system performance.

The invention will be illustrated by the preferred embodiments in conjunction with the drawings. DRAWINGS

Figure 1 is a block diagram showing the structure of a prior art maximum ratio combining receiver.

Figure 2 is a block diagram showing a prior art selective combining receiver.

Figure 3 is a block diagram showing the structure of the receiver of the present invention.

Figure 4 is a flow chart showing the diversity combining algorithm of the present invention. detailed description

Specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In Figure 1, the transmitter transmits an OFDM-modulated wireless signal that is received by the receiver's four antennas. The four signals are down-converted to the baseband signal, and then subjected to FFT (Fast Fourier Transform) to the corresponding receiving symbol of each subcarrier, and the received symbol Yk of the kth subcarrier.

Y _k = H _k X _k + N _k Where Xk is the transmitted symbol, Hk is the channel corresponding to subcarrier k, and Nk is additive noise. The channel response is then estimated by the received pilot symbol Yk in the received signal and the pilot symbol transmitted by the transmitter.

Χζ ^k Χζ By interpolating ^H k , the channel response on all subcarriers including the data symbols can be estimated. Maximum ratio combining of four signals, the maximum ratio of combined outputs is

^Σ Μ γ τ τ *

_ _m =ik,i ⁿ k,m

k,mrc 2 In Figure 2, according to the estimated value of the channel response or the estimated value of the signal-to-noise ratio, the branch with the largest modulus value or the largest signal-to-noise ratio of the channel response is selected as the received signal for demodulation. The equalization algorithm is as follows :

Figure 3 shows a block diagram of the receiver of the present invention.

As can be seen from Fig. 3, the receiving and combining apparatus of the multi-antenna system with decoding feedback of the present invention comprises: a down converter, a fast Fourier transform module, a channel estimation/signal-to-noise ratio estimator, a combiner, and a decoder. The functions and interrelationships of the various components of the receiving and collecting apparatus of the present invention are described in detail below.

According to the present invention, the down converter converts the multiplexed signals to the baseband signals respectively, and the fast Fourier transform module transforms the baseband signals to the received symbols corresponding to each subcarrier, and the received symbols of the kth subcarriers _k

Y _k = H _k X _k + N _k

Where X _k is the transmitted symbol, H _k is the channel corresponding to subcarrier k, and N _k is the reactive noise. The channel estimation/signal-to-noise ratio estimator is configured to estimate a signal to noise ratio of a signal received by each branch of the multi-antenna receiver. Specifically, the channel estimation/signal-to-noise ratio estimator estimates a channel response based on the received pilot symbol _Yk in the received signal and the pilot symbol transmitted by the transmitter.

Then, by interpolating, the channel response on all subcarriers including the data symbols is estimated.

The combiner is coupled to the channel estimation/signal-to-noise ratio estimator; the decoder is coupled to the combiner for decoding a signal output by the combiner.

The combiner performs the following actions in combination with the decoder:

(1) The combiner arranges the branches according to the estimated value of the signal-to-noise ratio;

(2) Select the branch with the largest signal-to-noise ratio for demodulation and decoding. If the decoding is correct, the decoding result is output. Specifically, the combiner selects a branch with the largest modulus value or the largest signal to noise ratio as the received signal for demodulation according to the estimated value of the channel response or the estimated value of the signal to noise ratio, and the equalization algorithm is as follows:

Yd _ _m

k,mrc where i _k represents the branch with the best signal quality;

(3) If the decoding is not correct, the second largest branch of the signal-to-noise ratio is added to the maximum ratio combining set, that is, the branch with the largest signal-to-noise ratio and the second largest signal-to-noise ratio is subjected to maximum ratio combining, and then demodulated and decoded. If the decoding is correct, the decoding result is output;

(4) If the decoding is not correct, the third branch of the signal-to-noise ratio is added to the maximum ratio combining set according to the above method until the decoding is correct, or all the branches have participated in the maximum ratio combining.

Specifically, the combiner performs maximum ratio combining on multiple signals, and the maximum The output of the merge is

Σ ^Μ γ U*

Σ

Figure 4 is a flow chart showing the diversity combining algorithm of the present invention. Referring to Figure 4, S1 arranges the branches in descending order of the estimated value of the signal-to-noise ratio. S2 initializes each branch to not participate in the maximum ratio combining. S3 adds the remaining branch with the largest signal-to-noise ratio in the branch that does not participate in the maximum ratio combining to the set that participates in the maximum ratio combining. S4 maximum ratio merge. S5 decoding. S6 judges whether the decoding is successful, and if the decoding is successful, the process ends, and if the decoding is unsuccessful, S7 is executed. S7 determines if there are any branches that are not involved in the maximum ratio merger. If there are branches that are not involved in the maximum ratio combining, execute S3. If there are no branches that have not participated in the maximum ratio merge, then it ends.

Claims

A receiving diversity combining method for a multi-antenna system with decoding feedback, comprising the steps of:

(1) The multi-antenna receiver arranges the branches according to the estimated value of the signal-to-noise ratio;

(2) selecting the branch with the largest signal to noise ratio for demodulation and decoding, and if the decoding is correct, outputting the decoding result;

(3) If the decoding is not correct, the branch with the second largest signal to noise ratio is added to the maximum ratio combining set, that is, the branch with the largest signal to noise ratio and the second largest signal to noise ratio is combined, and then demodulated and decoded. If the decoding is correct, the decoding result is output;

(4) If the decoding is not correct, the analogy of the third largest signal-to-noise ratio is added to the maximum ratio combining set until the decoding is correct, or all the branches have participated in the maximum ratio combining.

2. The method of claim 1 wherein the adaptive multi-antenna system is an Orthogonal Frequency Division Multiplexing (OFDM) OFDM system.

3. The method according to claim 1, wherein in step (1), each branch is arranged in descending order according to an estimated value of the signal to noise ratio.

4. The method according to claim 2, wherein the step (2) further comprises the steps of:

1 The transmitter of the OFDM system transmits an OFDM-modulated wireless signal, and the receiver performs multi-channel antenna reception, and the multi-channel signals are respectively down-converted to baseband signals, and then subjected to fast Fourier transform to corresponding to each subcarrier. Receive symbol, receive symbol Y _{k of the kth} subcarrier

Y _k =H _k X _k+ N _k Where X _k is the transmitted symbol, H _k is the channel corresponding to subcarrier k, and N _k is the force P noise;

2 Estimating the channel response based on the received pilot symbol Y _k in the received signal and the pilot symbol ^ transmitted by the transmitter

Then, by interpolating, the channel response on all subcarriers including the data symbols is estimated;

3 According to the estimated value of the channel response or the estimated value of the signal-to-noise ratio, the branch with the largest modulus value or the largest signal-to-noise ratio of the channel response is selected as the received signal for demodulation. The equalization algorithm is as follows:

J

Yd k,i _k ·

k, rc , where i _k represents the branch with the best signal quality.

5. The method according to claim 2, wherein the maximum ratio combining process in steps (3), (4) comprises the steps of:

1 The transmitter of the OFDM system transmits an OFDM-modulated wireless signal, and the receiver performs multi-channel antenna reception, and the multi-channel signals are respectively down-converted to baseband signals, and then subjected to fast Fourier transform to corresponding to each subcarrier. Receive symbol, 接收k subcarrier receive symbols Y _k

Y _k = H _k X _{k +} N _k

Where X _k is the transmitted symbol, H _k is the channel corresponding to subcarrier k, and N _k is the additive ^p ;;

2 Estimating the channel response based on the received pilot symbol Y _k in the received signal and the pilot symbol transmitted by the transmitter ^ kk Then, by interpolating, the channel response on all subcarriers including the data symbols is estimated;

3 For the maximum ratio combining of multiple signals, the maximum ratio combined output is

Σ ^Μ γ

_ ,,,=l ,

― _Λ 2 °

y ^M H _k , _i

6. A receiving diversity combining apparatus for a multi-antenna system having decoding feedback, comprising:

The combiner performs the following actions in combination with the decoder:

(2) selecting a branch with the largest signal to noise ratio for demodulation and decoding, and if the decoding is correct, outputting the decoding result;

(4) If the decoding is not correct, the analogy of the third largest signal-to-noise ratio is added to the maximum ratio combining set until the decoding is correct, or all branches have participated in the maximum ratio combining.

7. The apparatus of claim 6, wherein the adaptive multi-antenna system is an Orthogonal Frequency Division Multiplexing (OFDM) system.

8. Apparatus according to claim 6 wherein the branches are arranged in descending order by an estimate of the signal to noise ratio.

9. The apparatus according to claim 7, further comprising a down converter and a fast Fourier transform module, wherein the down converter respectively downconverts the signal to a baseband signal, and the fast Fourier transform module converts the baseband signal Transform to the received symbol corresponding to each subcarrier, 接收k subcarriers receive symbol Y _k

Y _k = H _k X _{k +} N _k

Where X _k is the transmitted symbol, H _k is the channel corresponding to subcarrier k, and N _k is the force P noise;

The channel estimation/signal-to-noise ratio estimator estimates a channel response based on the received pilot symbol Y _k in the received signal and the pilot symbol transmitted by the transmitter

The combiner selects a branch with the largest modulus value or the largest signal to noise ratio as the received signal for demodulation according to the estimated value of the channel response or the estimated value of the signal to noise ratio. The equalization algorithm is as follows:

Where i _k represents the branch with the best signal quality.

10. The apparatus of claim 7, further comprising a downconverter and a fast Fourier transform module, the downconverter downconverting the multipath signals to baseband signals, respectively, the fast Fourier transform module to the baseband signals Transform to each child Receive symbol corresponding to the carrier, receive symbol Y _{k of the kth} subcarrier

Y _k = H _k X _{k +} N _k

Where X _k is the transmitted symbol, H _k is the channel corresponding to subcarrier k, and N _k is additive noise;

The channel estimation/signal-to-noise ratio estimator estimates a channel response based on the received pilot symbol Y _k in the received signal and the pilot symbol A transmitted by the transmitter.

The combiner performs maximum ratio combining on multiple signals, and the maximum ratio combined output is