CN101800721B - Method and device for estimating interference in orthogonal frequency division multiplexing communication system - Google Patents

Abstract

The embodiment of the invention relates to a method and a device for estimating interference in an orthogonal frequency division multiplexing communication system. The method mainly comprises the following steps that: data output by a decoder is encoded, interwoven, modulated and processed, and a modulation symbol estimation value is obtained and transmitted to an interference estimator. The interference estimator estimates the interference through a plurality of times of iterative processing according to a received modulation symbol sequence, the modulation symbol estimation value and a channel estimation result, and obtains the interference estimation results of all subcarriers in an OFDM symbol. By adopting the processing process of iterative algorithm in interference estimation, the embodiment of the invention greatly improves the interference estimation precision, so as to lead an OFDM communication system to obtain nearly the best system performance.

Description

The method and apparatus of the Interference Estimation in the orthogonal FDM communication system

Technical field

The present invention relates to wireless communication technology field, relate in particular to the method and apparatus of the Interference Estimation in a kind of OFDM (orthogonalfrequency division multiplexing, OFDM) communication system.

Background technology

In recent years; People require increasingly high to communication quality; The demand of the business that can provide communication network is also more and more, and along with the continuous development of communication requirement, the frequency spectrum resource that can supply communicate by letter becomes increasingly scarce; The distribution that has been fixed of most frequency resource, thereby new wireless communication system will face the problem of sharing frequency spectrum with existing wireless communication system coexistence.Frequency range like WLAN and share for Bluetooth 2.4G.On the other hand, result of study shows that the utilance of frequency spectrum is not high, and very big in the availability of frequency spectrum fluctuation of areal, and in order to solve the in short supply and low contradiction of utilance of frequency spectrum resource, people have proposed cognitive radio technology.In the communication system based on cognitive radio technology, communication equipment can detect wireless electromagnetic environment on every side, and adjusts adaptively, and is multiplexing in the enterprising line frequency of different time and space, greatly improved the utilization ratio of frequency spectrum.

OFDM is a kind of communicate by letter modulation and multiplex technique that in wireless and wired communication system, is widely used, its contrary frequency selectivity decline effectively.In the radio communication that frequency spectrum coexistence is shared, the OFDM radio communication is easy to receive the coloured interference from other wireless communication system, under the situation of the position of known disturbances and power, can effectively suppress coloured interference based on the receiver of maximum-likelihood criterion.

A kind of structural representation of the ofdm communication system that has adopted cognitive radio technology is as shown in Figure 1, in the channel of this ofdm communication system, has fast-changing narrow band interference, and the signals transmission of this ofdm communication system is following:

For reducing the error rate in the signals transmission, the primary signal that the OFDM transmitter will transmit is carried out chnnel coding through encoder.Be the influence of reduction burst error, the signal of encoder output delivered to done interleaving treatment in the interleaver, output in the modulator then.Modulator output modulation symbol; Pass through string and conversion, IFFT (Inverse Fast Fourier Transform again; Inverse fast Fourier transform) conversion and also string conversion obtain the OFDM time-domain symbol, to launching through the OFDM transmitter behind this OFDM time-domain symbol increase Cyclic Prefix.

The OFDM receiver carries out synchronously, removes circulation prefix processing this ofdm communication signal behind the ofdm communication signal that receives above-mentioned OFDM transmitter emission, obtains the OFDM time-domain symbol.Again with above-mentioned OFDM time-domain symbol through string and conversion, FFT (Fast Fourier Transform; Fast Fourier transform) conversion and also string conversion; Obtain modulation symbol sequence, these modulation symbol sequences have received the influence of fading channel, coloured interference and white Gaussian noise.The channel estimation module of OFDM receiver is exported the channel estimating of current channel simultaneously.The data detection module of OFDM receiver detects the primary signal that above-mentioned OFDM transmitter receives according to above-mentioned modulation symbol sequence and channel estimating information.

The position of a kind of interference to receiver of the prior art and the scheme that power is estimated are: adopt the sliding window average algorithm that the position and the power that disturb are estimated; The flow process of the processing procedure of this scheme is as shown in Figure 2; Concrete processing procedure is: at first the reception signal to input carries out the judgement of modulation symbol; The modulation symbol that will receive signal and judgement to each modulation symbol then subtracts each other and obtains error signal, ask this error signal mould square, and then carry out frequency domain filtering; Frequency domain filtering has adopted the sliding window averaging method of preseting length, obtains position and the power information disturbed at last.

In realizing process of the present invention, the inventor finds that there is following problem in the position of above-mentioned interference to receiver at least with the scheme that power is estimated: the estimated accuracy of interference is not high, and main cause is that the modulation symbol error rate of adjudicating is higher; Need bigger sliding window length.This scheme can only be applicable to that interference power has the occasion of big correlation on frequency domain and time domain; Be difficult to adapt to narrow band interference and disturb fast-changing situation, can not satisfy the requirement that resists coloured interference based on the OFDM wireless communication system of cognitive radio technology.

Summary of the invention

Embodiments of the invention provide the method and apparatus of the Interference Estimation in a kind of ofdm communication system; The estimated accuracy of the interference that exists in the scheme with the solution prior art is not high, can not be applicable to the problem based on the OFDM wireless communication system of cognitive radio technology.

The device of the Interference Estimation in a kind of orthogonal FDM communication system comprises:

Interference estimator; Be used for according to the modulation symbol sequence, modulation symbol estimated value and the channel estimation results that receive; Carry out Interference Estimation through iterative processing; Obtain the Interference Estimation result of each number of sub-carrier in the OFDM symbol, said modulation symbol estimated value for the data of decoder output again through coding, interweave and modulation treatment after obtain;

Demodulator is used for the Interference Estimation result that transmits according to the said modulation symbol sequence, said channel estimation results and the interference estimator that receive, carries out the metric that soft demodulation process obtains each coded-bit in the OFDM symbol;

Deinterleaver, the metric of each coded-bit of OFDM symbol that is used for transmitting according to demodulator carries out deinterleaving and handles, and obtains data symbols;

Decoder is used for the data symbols of deinterleaver output is carried out decoding processing, obtains the data after the decoding processing.

The method of the Interference Estimation in a kind of orthogonal FDM communication system comprises:

According to the modulation symbol sequence that receives, modulation symbol estimated value and channel estimation results; Carry out Interference Estimation through iterative processing; Obtain the Interference Estimation result of each number of sub-carrier in the OFDM symbol; According to said Interference Estimation result, modulation symbol sequence and channel estimation results, carry out the metric that soft demodulation process obtains each coded-bit in the OFDM symbol again;

Metric according to each coded-bit in the said OFDM symbol; Carrying out deinterleaving handles; Said deinterleaving is handled the data symbols of back output and carried out decoding processing; Obtain the data after the decoding processing, said modulation symbol estimated value for the data after the decoding processing again through coding, interweave and modulation treatment after obtain.

Technical scheme by the embodiment of the invention described above provides can be found out; The embodiment of the invention is through having adopted the processing procedure of iterative algorithm in Interference Estimation; Improved the estimated accuracy of having disturbed greatly, thereby made ofdm communication system obtain the systematic function of near-optimization.

Description of drawings

In order to be illustrated more clearly in the technical scheme of the embodiment of the invention; The accompanying drawing of required use is done to introduce simply in will describing embodiment below; Obviously, the accompanying drawing in describing below only is some embodiments of the present invention, for those of ordinary skills; Under the prerequisite of not paying creative work property, can also obtain other accompanying drawing according to these accompanying drawings.

Fig. 1 is a kind of structural representation that has adopted the ofdm communication system of cognitive radio technology of the prior art;

Fig. 2 is the flow chart of the processing procedure of the position of a kind of interference to receiver of the prior art and the scheme that power is estimated;

A kind of structural representation of uniting the device of Interference Estimation and encoding and decoding that Fig. 3 proposes for the embodiment of the invention one;

The process chart of the method for the Interference Estimation in a kind of ofdm communication system that Fig. 4 provides for the embodiment of the invention four;

Fig. 5 is the performance of the interference estimation method of embodiment of the invention proposition, the simulation result sketch map under the different interference intensity situation.

Embodiment

In embodiments of the present invention; Interference estimator is according to the modulation symbol sequence, modulation symbol estimated value and the channel estimation results that receive; Carry out Interference Estimation through iterative processing repeatedly; Obtain the Interference Estimation result of each number of sub-carrier in the OFDM symbol, give demodulator said Interference Estimation result transmission.The Interference Estimation result that demodulator transmits according to the said modulation symbol sequence, said channel estimation results and the interference estimator that receive; Carry out soft demodulation process and obtain the metric of each coded-bit in the OFDM symbol, the metric of said each coded-bit is transferred to deinterleaver.The metric of each coded-bit in the OFDM symbol that deinterleaver transmits according to demodulator carries out deinterleaving and handles, and gives decoder with the transmission of data symbols that obtains.Decoder carries out decoding processing to the data symbols of deinterleaver output, obtains the data after the decoding processing.

Further, said modulation symbol sequence for the OFDM symbol that coding side is sended over go Cyclic Prefix, string and conversion, fast Fourier transform and and the string conversion after obtain.Said modulation symbol estimated value for the data of decoder output again through coding, interweave and modulation treatment after obtain.

Further; Data to decoder output are carried out error correction coding through the cataloged procedure identical with transmitting terminal; Obtain the coded-bit of OFDM symbol; Coded-bit to said OFDM symbol carries out interleaving treatment through the interleaving process identical with transmitting terminal; Obtain the estimated value of each bit of each number of sub-carrier rise system symbol in the said OFDM symbol, the estimated value of said each bit is carried out modulation treatment, obtain each number of sub-carrier rise system sign estimation value in the said OFDM symbol.

Further, the number of times of the iterative processing in said Interference Estimation reaches predetermined value, and perhaps, the difference between the Interference Estimation result of the double output of said Interference Estimation judges then that less than predetermined value the iterative processing in the said Interference Estimation restrains.

Further; According to after the said decoding processing for the first time in the OFDM symbol that obtains of the data of output each number of sub-carrier raise system sign estimation value; And the channel estimation results and the said modulation symbol sequence of each number of sub-carrier in the OFDM symbol; Carry out Interference Estimation through predetermined algorithm, obtain the initial interference estimated result of each number of sub-carrier in the OFDM symbol;

Each number of sub-carrier raises system sign estimation value in the OFDM symbol that obtains according to the data of last output after the said decoding processing; And the channel estimation results and the said modulation symbol sequence of each number of sub-carrier in the OFDM symbol; Carry out Interference Estimation through predetermined algorithm, obtain the Interference Estimation result of this iteration of each number of sub-carrier in the OFDM symbol.

Further, obtain the subcarrier information that is not interfered according in the OFDM symbol that for the first time data of output obtain after the said decoding processing, the Interference Estimation result of all subcarriers that are not interfered is averaged;

Obtain the subcarrier information that is not interfered in the OFDM symbol that the data according to last output after the said decoding processing obtain, the Interference Estimation result of all subcarriers that are not interfered is averaged.

Further, the initial interference estimated result of each number of sub-carrier in the said OFDM symbol is carried out the sliding window Filtering Processing, the size of said sliding window is provided with according to the number of said subcarrier;

Interference Estimation result to this iteration of each number of sub-carrier in the said OFDM symbol carries out the sliding window Filtering Processing, and the size of said sliding window is provided with according to the number of said subcarrier.

For ease of the understanding to the embodiment of the invention, will combine accompanying drawing below is that example is done further and explained with several specific embodiments, and each embodiment does not constitute the qualification to the embodiment of the invention.

Embodiment one

It is as shown in Figure 3 that this embodiment proposes a kind of structural representation of device of uniting Interference Estimation and encoding and decoding; This device is arranged in the OFDM receiver; Comprise like lower module: unit such as interference estimator, demodulator, deinterleaver, decoder, encoder, interleaver, modulator and judgement control module; A loop has been formed in these unit, and the process of Interference Estimation and encoding and decoding can iteration be carried out in this loop, until reaching primary signal more accurately.Introduce the concrete function of each unit below respectively:

1, interference estimator:

The channel estimation results that the modulation symbol that interference estimator transmits according to modulator, channel estimation module transmit; And the modulation symbol sequence that receives; Carry out Interference Estimation; Obtain the power that noise stack on each number of sub-carrier is disturbed is estimated (hereinafter to be referred as Interference Estimation), and output to demodulator.

Said modulation symbol sequence for the OFDM symbol that coding side is sended over go Cyclic Prefix, string and conversion, FFT conversion and and the string conversion after obtain.

Comprise initial interference estimation module and iteration interference estimation block in the above-mentioned interference estimator.

1.1; The initial interference estimation module; Each number of sub-carrier of OFDM symbol that is used for obtaining according to the data that decoder is exported for the first time raises system sign estimation value; And the channel estimation results and the said modulation symbol sequence of each number of sub-carrier among the OFDM, carry out Interference Estimation through predetermined algorithm, obtain the initial interference estimated result of each number of sub-carrier in the OFDM symbol;

The computational methods that the initial interference of the modulation symbol that sends on the k number of sub-carrier in L the OFDM symbol in the ofdm communication signal that the OFDM receiver receives is estimated

are following:

${\hat{x}}_{k,0}^l=\arg \underset{x\∈\mathrm{\χ}}{\min }{|y_k^l-{\mathrm{\α}}_k^{l}x|}^2$

Above-mentioned χ is the set of all signaling points on the modulation constellation, α _k ^lBe the channel estimating of k number of sub-carrier in L the OFDM symbol of channel estimation module output of OFDM receiver, y _k ^lIt is said modulation symbol sequence.

To from 1 to L OFDM symbol, the initial Interference Estimation of the modulation symbol on the k number of sub-carrier superpose, the initial Interference Estimation that obtains

is:

${\widehat{\mathrm{\σ}}}_{k,0}^2=\frac{1}{L}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{|y_k^l-{\mathrm{\α}}_k^l{\hat{x}}_{k,0}^l|}^2$

1.2; The iteration interference estimation block; Be used for raising system sign estimation value according to each number of sub-carrier of OFDM symbol that the last data of exporting of decoder obtain; And the channel estimation results and the said modulation symbol sequence of each number of sub-carrier in the OFDM symbol, carry out Interference Estimation through predetermined algorithm, obtain the Interference Estimation result of this iteration of each number of sub-carrier in the OFDM symbol.

In device shown in Figure 3; With the data of decoder output through recompile, interweave and modulate after obtain modulation symbol; And feed back to interference estimator; The modulation symbol that the iteration interference estimation block is utilized this feedback carries out Interference Estimation through iterative process repeatedly, and this Interference Estimation is called as the Interference Estimation in the iteration.

Above-mentioned initial Interference Estimation is exactly the 0th Interference Estimation in the iteration.The signal bit of decoder output through recompile, interweave after; Obtain in the p time iteration the estimated value

of i bit of the modulation symbol on the k number of sub-carrier in L the OFDM symbol; Signal after above-mentioned interweaving obtains in the p time iteration the Interference Estimation

to the modulation symbol on the k number of sub-carrier in L the OFDM symbol through modulator again; To from 1 to L OFDM symbol, the Interference Estimation of the modulation symbol on the k number of sub-carrier superpose, the Interference Estimation in the new iteration that obtains

is:

${\widehat{\mathrm{\σ}}}_{k,p+1}^2=\frac{1}{L}\underset{l=1}{\overset{L}{\mathrm{\Σ}}}{|y_k^l-{\mathrm{\α}}_k^l{\hat{x}}_{k,p}^l|}^2$

2, demodulator

Demodulator receives the Interference Estimation that channel estimating that said modulation symbol sequence, channel estimation module transmit and interference estimator transmit; The above-mentioned signal that receives is carried out soft demodulation process, and the metric of each coded-bit is given deinterleaver in the output OFDM symbol.

At first calculate corresponding $c_k^{i,l}=b$ Metric, c wherein _k ^{I, l}Be i bit of modulation symbol on L the OFDM symbol k number of sub-carrier, 1≤i≤m, m is the exponent number of modulation, b ∈ 0,1}

${\mathrm{\&lambda;}}_p(c_k^{i,l}=b)=\underset{x\&Element;{\mathrm{\&chi;}}_b^i}{\min }\frac{{|y_k^l-{\mathrm{\&alpha;}}_k^{l}x|}^2}{{\widehat{\mathrm{\&sigma;}}}_{k,\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="H200910078020XE00032.png"\; state="\{\{state\}\}">p</figure-callout>}}^2}$

In the above-mentioned formula ${\mathrm{\&chi;}}_b^i=\left\{\mathrm{\&mu;}(c_{k,p}^{1,l},...c_{k,p}^{i,l},...c_{k,p}^{m,l})\right|c_{k,p}^{i,l}=b\}$ Be the set that corresponding i bit equals all signaling points of b on the modulation constellation, wherein μ is the modulation mapping function, and its effect is that m bit is mapped as a modulation symbol, Be the p time Interference Estimation on the iteration k number of sub-carrier.Corresponding each coded-bit, the metric of demodulator output is:

${\mathrm{\&lambda;}}_p\left(c_k^{i,l}\right)={\mathrm{\&lambda;}}_p(c_k^{i,l}=1)-{\mathrm{\&lambda;}}_p(c_k^{i,l}=0)$

3, deinterleaver

The metric of each coded-bit in the OFDM symbol of deinterleaver receiving demodulation device output, and carry out deinterleaving and handle, this deinterleaving processing procedure is the inverse process of interleaving treatment, and the data symbols that obtains is outputed to decoder.

4, decoder

Decoder carries out error correction decoding to the data symbols of decoder output to be handled, and the code element of correcting a mistake is removed redundant information, with the data output that obtains.

5, encoder

Encoder carries out error correction coding to the data of decoder output through the cataloged procedure identical with transmitting terminal, and the information bit of the OFDM symbol behind the coding that obtains is outputed to interleaver.

6, interleaver

The information bit of the OFDM symbol of interleaver after to the coding of encoder output carries out interleaving treatment, promptly the information bit behind the above-mentioned coding is upset its order by the same mode of transmitting terminal.The information bit of the OFDM symbol behind the above-mentioned coding is through after the interleaving treatment; Obtain in the p time iteration the estimated value

of i bit of modulation symbol on L the OFDM symbol k number of sub-carrier,

outputs to modulator with this estimated value.

7, modulator

Modulator is modulated the estimated value of each bit of modulation symbol on L the OFDM symbol k number of sub-carrier of above-mentioned interleaver output, obtains in the p time iteration the modulation symbol estimated value on the k number of sub-carrier in L the OFDM symbol

${\hat{x}}_{k,p}^l=\mathrm{\&mu;}({\hat{c}}_{k,p}^{1,l},{\hat{c}}_{k,\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="H200910078020XE00032.png"\; state="\{\{state\}\}">p</figure-callout>}}^{2,l},...{\widehat{,c}}_{k,p}^{m,l})$

Modulator outputs to the above-mentioned modulation symbol estimated value that obtains in the interference estimator.

8, judge control module, be used for judging whether the iterative processing of said interference estimator restrains, if then control with the data of said decoder output final decoded result as said OFDM symbol; Otherwise, then control the data of decoder output are passed through coding again, interweaved and modulation treatment, the modulation symbol estimated value that obtains is transferred to interference estimator again.

The data of above-mentioned decoder output or not as final decoded result immediately, but feed back to the new Interference Estimation of completion in the interference estimator, realize iteration.When iteration reaches stable promptly to k arbitrarily, have ${\widehat{\mathrm{\&sigma;}}}_{k,p+1}^2\&ap;{\widehat{\mathrm{\&sigma;}}}_{k,\mathrm{<figure-callout\; id="2"\; label="p"\; filenames="H200910078020XE00032.png"\; state="\{\{state\}\}">p</figure-callout>}}^2,$ Perhaps iterations reaches preset value, and iterative process convergence is then controlled the data of the said decoder output final decoded result as said OFDM symbol.

This embodiment has been through having adopted the processing procedure of iterative algorithm, improved greatly the estimated accuracy of having disturbed in Interference Estimation, thereby makes ofdm communication system obtain the systematic function of near-optimization.

Embodiment two

This embodiment improves the processing procedure of the interference estimator in the foregoing description 1, in interference estimator, increases the process of frequency domain part average treatment.The principle of this frequency domain part average treatment is: judge the information of number s of the subcarrier that is disturbed, the position that obtains this s number of sub-carrier judges that to all the other the noise power on the undisturbed subcarrier averages, and obtains mean value.

1, increased the initial Interference Estimation of frequency domain part average treatment

The computational methods of the initial Interference Estimation of describing according to the foregoing description one; To from 1 to L OFDM symbol, the initial Interference Estimation of the modulation symbol on the k number of sub-carrier superpose, the initial Interference Estimation that obtains is:

${\widehat{\mathrm{\&sigma;}}}_{k,0}^2=\frac{1}{L}\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{|y_k^l-{\mathrm{\&alpha;}}_k^l{\hat{x}}_{k,0}^l|}^2$

. judge that the maximum s number of sub-carrier of interference power is the subcarrier that is interfered in the above-mentioned Interference Estimation, decision method is following:

$\stackrel{\&OverBar;}{R}=\left\{(k_1,{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="H200910078020XE00032.png"\; state="\{\{state\}\}">k</figure-callout>}}_2,...,k_s)\right|\&ForAll;k_i\&Element;\stackrel{\&OverBar;}{R},\&ForAll;k_j\&Element;R-\stackrel{\&OverBar;}{R},{\widetilde{\mathrm{\&sigma;}}}_{k_i,0}^2\&GreaterEqual;{\widetilde{\mathrm{\&sigma;}}}_{k_j,0}^2\}$

R is the set of the sequence number of the s number of sub-carrier disturbed in the above-mentioned formula, and R is the set of the sequence number of all subcarriers, and the initial Interference Estimation of then having carried out exporting after the frequency domain part average treatment is following:

${\widehat{\mathrm{\&sigma;}}}_{k,0}^2=\left\{\begin{array}{cc}\frac{1}{K-s}\underset{k\&Element;R-\stackrel{\&OverBar;}{R}}{\mathrm{\&Sigma;}}{\widetilde{\mathrm{\&sigma;}}}_{k,0}^2& k\&Element;R-\stackrel{\&OverBar;}{R}\\ {\widetilde{\mathrm{\&sigma;}}}_{k,0}^2& k\&Element;\stackrel{\&OverBar;}{R}\end{array}\right.$

K is the number of all subcarriers of OFDM in the formula.

2, increased Interference Estimation in the iteration of frequency domain part average treatment

Computational methods according to the Interference Estimation in the iteration of the foregoing description one description; In the p time iteration; To from 1 to L OFDM symbol, the Interference Estimation of the modulation symbol on the k number of sub-carrier superpose, the Interference Estimation in the iteration that obtains

is:

${\widehat{\mathrm{\&sigma;}}}_{k,p+1}^2=\frac{1}{L}\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{|y_k^l-{\mathrm{\&alpha;}}_k^l{\hat{x}}_{k,p}^l|}^2$

. judge that the maximum s number of sub-carrier of interference power is the subcarrier that is interfered in the Interference Estimation, decision method is following:

$\stackrel{\&OverBar;}{R}=\left\{(k_1,{\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="H200910078020XE00032.png"\; state="\{\{state\}\}">k</figure-callout>}}_2,...,k_s)\right|\&ForAll;k_i\&Element;\stackrel{\&OverBar;}{R},\&ForAll;k_j\&Element;R-\stackrel{\&OverBar;}{R},{\widetilde{\mathrm{\&sigma;}}}_{k_i,p+1}^2\&GreaterEqual;{\widetilde{\mathrm{\&sigma;}}}_{k_j,p+1}^2\}$

R is the set of the sequence number of the subcarrier that is disturbed in the formula, and R is the set of the sequence number of all subcarriers, and the Interference Estimation of the p+1 time iteration of then having carried out exporting after the frequency domain part average treatment is following:

${\widehat{\mathrm{\&sigma;}}}_{k,p+1}^2=\left\{\begin{array}{cc}\frac{1}{K-s}\underset{k\&Element;R-\stackrel{\&OverBar;}{R}}{\mathrm{\&Sigma;}}{\widetilde{\mathrm{\&sigma;}}}_{k,p+1}^2& k\&Element;R-\stackrel{\&OverBar;}{R}\\ {\widetilde{\mathrm{\&sigma;}}}_{k,p+1}^2& k\&Element;\stackrel{\&OverBar;}{R}\end{array}\right.$

This embodiment can improve the speed of the iterative process convergence in the interference estimator effectively, reduces the time-delay of input, makes communication system can tackle arrowband and fast-changing disturbed condition.

Embodiment three

This embodiment improves the processing procedure of the interference estimator in the foregoing description 1, in interference estimator, increases the process of frequency domain sliding window Filtering Processing.

1, increased the initial Interference Estimation of frequency domain sliding window Filtering Processing

The computational methods of the initial Interference Estimation of describing according to the foregoing description one; To from 1 to L OFDM symbol, the initial Interference Estimation of the modulation symbol on the k number of sub-carrier superpose, the initial Interference Estimation that obtains

is:

${\widehat{\mathrm{\&sigma;}}}_{k,0}^2=\frac{1}{L}\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{|y_k^l-{\mathrm{\&alpha;}}_k^l{\hat{x}}_{k,0}^l|}^2$

Having increased the initial Interference Estimation of exporting after the frequency domain sliding window Filtering Processing is:

${\widehat{\mathrm{\&sigma;}}}_{k,0}^2=\underset{m=-M}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_m{\widetilde{\mathrm{\&sigma;}}}_{k+m,0}^2$

ω wherein _mBe the sliding filter coefficient, ω _mSatisfy $\underset{m=-M}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_m=1,$ The size of sliding window is 2M+1, and the size of this sliding window is provided with according to the number of said subcarrier.

Size with sliding window is 4 below, and subcarrier is 8 and is example, the basic principle of above-mentioned sliding window Filtering Processing is described.At first, extract the 1-4 number of sub-carrier, the interference power of this 4 number of sub-carrier is averaged, obtain the 1st mean value.Then, extract the 2-5 number of sub-carrier, the interference power of this 4 number of sub-carrier is averaged, obtain the 2nd mean value.And the like, extract 3-6,4-7,5-8 number of sub-carrier more respectively, obtain the 3rd, 4,5 mean value respectively.At last, with the interference power sequence of above-mentioned the 1st, 2,3,4,5 mean value that obtains as new subcarrier.

2, increased Interference Estimation in the iteration of frequency domain sliding window Filtering Processing

Computational methods according to the Interference Estimation in the iteration of the foregoing description one description; In the p time iteration; To from 1 to L OFDM symbol, the Interference Estimation of the modulation symbol on the k number of sub-carrier superpose, the Interference Estimation in the iteration that obtains

is:

${\widehat{\mathrm{\&sigma;}}}_{k,p+1}^2=\frac{1}{L}\underset{l=1}{\overset{L}{\mathrm{\&Sigma;}}}{|y_k^l-{\mathrm{\&alpha;}}_k^l{\hat{x}}_{k,p}^l|}^2$

The Interference Estimation that has increased the p+1 time iteration exporting after the frequency domain sliding window Filtering Processing is following:

${\widehat{\mathrm{\&sigma;}}}_{k,p+1}^2=\underset{m=-M}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_m{\widetilde{\mathrm{\&sigma;}}}_{k+m,p+1}^2$

ω wherein _mBe the sliding filter coefficient, ω _mSatisfy $\underset{m=-M}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_m=1,$ The size of sliding window is 2M+1, and the size of this sliding window is provided with according to the number of said subcarrier.

This embodiment can improve the speed of the iterative process convergence in the interference estimator effectively, reduces the time-delay of input, makes communication system can tackle the disturbed condition in broadband.

Embodiment four

The handling process of the method for the Interference Estimation in a kind of ofdm communication system that this embodiment provides is as shown in Figure 4, comprises following treatment step:

Step 41, according to the modulation symbol sequence, modulation symbol estimated value and the channel estimation results that receive, carry out Interference Estimation through iterative processing repeatedly, obtain the Interference Estimation result of each number of sub-carrier in the OFDM symbol.

Said modulation symbol sequence for the OFDM symbol that coding side is sended over go Cyclic Prefix, string and conversion, fast Fourier transform and and the string conversion after obtain, said modulation symbol estimated value for the data of exporting after the decoding processing again through coding, interweave and modulation treatment after obtain.

In above-mentioned interference estimation process; Each number of sub-carrier raises system sign estimation value in the OFDM symbol that obtains according to the data of exporting after the decoding processing the said first time; And the channel estimation results and the said modulation symbol sequence of each number of sub-carrier in the OFDM symbol; Carry out Interference Estimation through predetermined algorithm, obtain the initial interference estimated result of each number of sub-carrier in the OFDM symbol;

Each number of sub-carrier raises system sign estimation value in the OFDM symbol that obtains according to the data of exporting after the last decoding processing; And the channel estimation results and the said modulation symbol sequence of each number of sub-carrier in the OFDM symbol; Carry out Interference Estimation through predetermined algorithm, obtain the Interference Estimation result of this iteration of each number of sub-carrier in the OFDM symbol.

In practical application, can also improve above-mentioned interference estimation process.Such as: obtain the subcarrier information that is not interfered in the OFDM symbol that the data exported after the decoding processing according to the said first time obtain, the Interference Estimation result of all subcarriers that are not interfered is averaged, obtain mean value; Obtain the subcarrier information that is not interfered in the OFDM symbol that obtains according to the data of exporting after the said last decoding processing, the Interference Estimation result of all subcarriers that are not interfered is averaged, obtain mean value.

For another example, the initial interference estimated result of each number of sub-carrier in the said OFDM symbol is carried out the sliding window Filtering Processing, the size of said sliding window is provided with according to the number of said subcarrier; Interference Estimation result to this iteration of each number of sub-carrier in the said OFDM symbol carries out the sliding window Filtering Processing, and the size of said sliding window is provided with according to the number of said subcarrier.

Step 42, according to Interference Estimation result, modulation symbol sequence and the channel estimation results of each number of sub-carrier in the said OFDM symbol, carry out the metric that soft demodulation process obtains each coded-bit in the OFDM symbol.

Step 43, according to the metric of each coded-bit in the said OFDM symbol, carry out deinterleaving and handle, said deinterleaving is handled the data symbols of back output and is carried out decoding processing, with the data output that obtains.

Step 44, judge whether the iterative processing in the said Interference Estimation restrains, if, then with the final decoded result of the data of exporting after the said decoding processing as said OFDM symbol; Otherwise, execution in step 45.

The number of times of the iterative processing in said Interference Estimation reaches predetermined value, and perhaps, the difference between the Interference Estimation result of the double output of said Interference Estimation judges then that less than predetermined value the iterative processing in the said Interference Estimation restrains.

Step 45, with the data of exporting after the said decoding processing again through the coding identical with transmitting terminal, interweave and modulation treatment after obtain the modulation symbol estimated value, said modulation symbol estimated value is transferred to said interference estimation process.

One of ordinary skill in the art will appreciate that all or part of flow process that realizes in the foregoing description method; Be to instruct relevant hardware to accomplish through computer program; Described program can be stored in the computer read/write memory medium; This program can comprise the flow process like the embodiment of above-mentioned each side method when carrying out.Wherein, described storage medium can be magnetic disc, CD, read-only storage memory body (Read-Only Memory, ROM) or at random store memory body (Random Access Memory, RAM) etc.

In sum, the embodiment of the invention has been through having adopted the processing procedure of iterative algorithm, improved greatly the estimated accuracy of having disturbed in Interference Estimation, thereby makes ofdm communication system obtain the systematic function of near-optimization.The computation complexity of above-mentioned iterative algorithm is 2 times of general non-iteration interference estimation method computation complexity.The increase of this complexity is an acceptable.

The embodiment of the invention also through adopting the method for frequency domain part average treatment and frequency domain sliding window Filtering Processing, has improved the convergence rate of Interference Estimation and decoding greatly, makes communication system can tackle the arrowband and change fast, and the disturbed condition in broadband.

The embodiment of the invention not only can be used for the cognitive radio scene; Also be suitable for existing in the radio communication situation of other communication systems interference; As: under the coexistence situation of the ofdm communication system in broadband and the Bluetooth communication system of arrowband relatively, can be used for the wideband OFDM communication system and suppress interference from Bluetooth communication system; Perhaps be used for adopting the cell mobile communication systems of OFDM technology to suppress interference from neighbor cell.

In order to confirm the performance advantage of the embodiment of the invention, carried out Computer Simulation, enclosed partial simulation content and result below.What at first carry out is the emulation of system under the different interference intensity situation, and simulated environment is a narrow band interference, and simulation result is as shown in Figure 5.Abscissa is an interference strength among Fig. 5, and ordinate is the error rate.LIED represents the performance of the interference estimation method of embodiment of the invention proposition; IED represents the limiting performance of the interference estimation method of embodiment of the invention proposition; MLD has represented the limiting performance of all interference estimation methods; Conventional has represented the performance when not adopting interference estimation method, and parameter P representes iterations.As can beappreciated from fig. 4, the performance of the interference estimation method of embodiment of the invention proposition can reach the MLD limiting performance under all interference strength situation.

The above; Be merely the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, any technical staff who is familiar with the present technique field is in the technical scope that the present invention discloses; The variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.

Claims (9)

1. the device of the Interference Estimation in the orthogonal FDM communication system is characterized in that, comprising:

Interference estimator; Be used for according to the modulation symbol sequence, modulation symbol estimated value and the channel estimation results that receive; Carry out Interference Estimation through iterative processing; Obtain the Interference Estimation result of each number of sub-carrier in the OFDM symbol, said modulation symbol estimated value for the data of decoder output again through coding, interweave and modulation treatment after obtain;

Demodulator is used for the Interference Estimation result that transmits according to the said modulation symbol sequence, said channel estimation results and the interference estimator that receive, carries out the metric that soft demodulation process obtains each coded-bit in the OFDM symbol;

Deinterleaver, the metric of each coded-bit of OFDM symbol that is used for transmitting according to demodulator carries out deinterleaving and handles, and obtains data symbols;

Decoder is used for the data symbols of deinterleaver output is carried out decoding processing, obtains the data after the decoding processing;

Said Interference Estimation implement body comprises:

The initial interference estimation module; Each number of sub-carrier of OFDM symbol that is used for obtaining according to the data after the first time decoding processing raises system sign estimation value; And the channel estimation results and the said modulation symbol sequence of each number of sub-carrier in the OFDM symbol; Carry out Interference Estimation through predetermined algorithm, obtain the initial interference estimated result of each number of sub-carrier in the OFDM symbol;

The iteration interference estimation block; Each number of sub-carrier of OFDM symbol that is used for obtaining according to the data after the last decoding processing raises system sign estimation value; And the channel estimation results and the said modulation symbol sequence of each number of sub-carrier in the OFDM symbol; Carry out Interference Estimation through predetermined algorithm, obtain the Interference Estimation result of this iteration of each number of sub-carrier in the OFDM symbol;

Concrete; Described initial interference estimation module; Also be used for obtaining the subcarrier information that the OFDM symbol that obtains according to the data after the first time decoding processing is not interfered, the Interference Estimation result of all subcarriers that are not interfered is averaged, obtain mean value;

Described iteration interference estimation block; Also be used for obtaining the subcarrier information that the OFDM symbol that obtains according to the data after the last decoding processing is not interfered; The Interference Estimation result of all subcarriers that are not interfered is averaged, obtain mean value;

Perhaps,

Described initial interference estimation module also is used for the initial interference estimated result of said each number of sub-carrier of OFDM symbol is carried out the sliding window Filtering Processing, and the size of said sliding window is provided with according to the number of said subcarrier;

Described iteration interference estimation block also is used for the Interference Estimation result of this iteration of said each number of sub-carrier of OFDM symbol is carried out the sliding window Filtering Processing, and the size of said sliding window is provided with according to the number of said subcarrier.

2. the device of the Interference Estimation in the orthogonal FDM communication system according to claim 1 is characterized in that, said device also comprises:

Judge control module, be used for judging whether the iterative processing of said interference estimator restrains, if, then with the final decoded result of the data after the said decoding processing as said OFDM symbol; Otherwise, the data after the said decoding processing again through encoding, interweaving and modulation treatment, are transferred to said interference estimator with the modulation symbol estimated value that obtains.

3. the device of the Interference Estimation in the orthogonal FDM communication system according to claim 2 is characterized in that:

Said judgement control module; Also be used for reaching predetermined value at the number of times of the iterative processing of said interference estimator; Perhaps, the difference between the Interference Estimation result of the double output of said interference estimator judges then that less than predetermined value the iterative processing in the said interference estimator restrains.

4. the device of the Interference Estimation in the orthogonal FDM communication system according to claim 1 is characterized in that, said device also comprises:

Encoder is used for the data after the said decoding processing are carried out error correction coding through the cataloged procedure identical with transmitting terminal, obtains the coded-bit of OFDM symbol;

Interleaver; The coded-bit of the OFDM symbol that is used for encoder is transmitted carries out interleaving treatment through the interleaving process identical with transmitting terminal, obtains the estimated value that each number of sub-carrier in the said OFDM symbol raises each bit of making symbol;

Modulator, the estimated value of said each bit that is used for interleaver is transmitted is modulated, and obtains that each number of sub-carrier raises system sign estimation value in the said OFDM symbol, and said modulation symbol estimated value is transferred to interference estimator.

5. the method for the Interference Estimation in the orthogonal FDM communication system is characterized in that, comprising:

According to the modulation symbol sequence that receives, modulation symbol estimated value and channel estimation results; Carry out Interference Estimation through iterative processing; Obtain the Interference Estimation result of each number of sub-carrier in the OFDM symbol; According to said Interference Estimation result, modulation symbol sequence and channel estimation results, carry out the metric that soft demodulation process obtains each coded-bit in the OFDM symbol again;

Metric according to each coded-bit in the said OFDM symbol; Carrying out deinterleaving handles; Said deinterleaving is handled the data symbols of back output and carried out decoding processing; Obtain the data after the decoding processing, said modulation symbol estimated value for the data after the decoding processing again through coding, interweave and modulation treatment after obtain;

Describedly carry out Interference Estimation, obtain the Interference Estimation result of each number of sub-carrier in the OFDM symbol, specifically comprise through iterative processing:

Each number of sub-carrier raises system sign estimation value in the OFDM symbol that obtains according to the data after the said first time decoding processing; And the channel estimation results and the said modulation symbol sequence of each number of sub-carrier in the OFDM symbol; Carry out Interference Estimation through predetermined algorithm, obtain the initial interference estimated result of each number of sub-carrier in the OFDM symbol;

Each number of sub-carrier raises system sign estimation value in the OFDM symbol that obtains according to the data after the said last decoding processing; And the channel estimation results and the said modulation symbol sequence of each number of sub-carrier in the OFDM symbol; Carry out Interference Estimation through predetermined algorithm, obtain the Interference Estimation result of this iteration of each number of sub-carrier in the OFDM symbol;

Concrete, obtain the subcarrier information that is not interfered in the OFDM symbol that obtains according to the data after the said first time decoding processing, the Interference Estimation result of all subcarriers that are not interfered is averaged, obtain mean value;

Obtain the subcarrier information that is not interfered in the OFDM symbol that obtains according to the data after the said last decoding processing, the Interference Estimation result of all subcarriers that are not interfered is averaged, obtain mean value;

Perhaps,

Initial interference estimated result to each number of sub-carrier in the said OFDM symbol carries out the sliding window Filtering Processing, and the size of said sliding window is provided with according to the number of said subcarrier;

Interference Estimation result to this iteration of each number of sub-carrier in the said OFDM symbol carries out the sliding window Filtering Processing, and the size of said sliding window is provided with according to the number of said subcarrier.

6. the method for the Interference Estimation in the orthogonal FDM communication system according to claim 5; It is characterized in that, described modulation symbol sequence for the OFDM symbol that coding side is sended over go Cyclic Prefix, string and conversion, fast Fourier transform and and the string conversion after obtain.

7. the method for the Interference Estimation in the orthogonal FDM communication system according to claim 5 is characterized in that, described method also comprises:

Judge whether the iterative processing in the said Interference Estimation restrains, if, then with the final decoded result of the data after the said decoding processing as said OFDM symbol; Otherwise, with the data after the said decoding processing again through the coding, interweave and modulation treatment after obtain the modulation symbol estimated value, said modulation symbol estimated value is transferred to said interference estimation process.

8. the method for the Interference Estimation in the orthogonal FDM communication system according to claim 7 is characterized in that, describedly judges that whether the iterative processing in the said Interference Estimation restrains, and specifically comprises:

The number of times of the iterative processing in said Interference Estimation reaches predetermined value, and perhaps, the difference between the Interference Estimation result of the double output of said Interference Estimation judges then that less than predetermined value the iterative processing in the said Interference Estimation restrains.

9. the method for the Interference Estimation in the orthogonal FDM communication system according to claim 7 is characterized in that, described with the data of exporting after the said decoding processing again through the coding, interweave and modulation treatment after obtain the modulation symbol estimated value, comprising:

Data to exporting after the said decoding processing are carried out error correction coding through the cataloged procedure identical with transmitting terminal, obtain the coded-bit of OFDM symbol;

Coded-bit to said OFDM symbol carries out interleaving treatment through the interleaving process identical with transmitting terminal, obtains the estimated value of each bit of each number of sub-carrier rise system symbol in the said OFDM symbol;

Estimated value to said each bit is carried out modulation treatment, obtains each number of sub-carrier rise system sign estimation value in the said OFDM symbol.

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