CN102195672B - OFDM (Orthogonal Frequency Division Multiplexing) system inter-cell interference elimination method based on IDMA (Interleave-Division Mutiple-Access) - Google Patents

Abstract

The invention provides an OFDM (Orthogonal Frequency Division Multiplexing) system inter-cell interference elimination method based on IDMA (Interleave-Division Mutiple-Access), which comprises the following steps of: distinguishing different cell base station transmitters by configurations of different interleavers; and classifying all the base stations except a T-BS (Target cell Base Station) into an S-BS (Strong interference Base Station) and a W-BS (Weak interference Base Station) according to strength of interference signals by a mobile user receiver, wherein a signal of the W-BS is processed as a gaussian noise, a signal of the T-BS and a signal of the S-BS are detected in iteration, therefore interference outside the T-BS can be suppressed and estimate data of the T-BS can be obtained. The OFDM system inter-cell interference elimination method based on IDMA, provided by the invention, has the advantage of excellent interference suppression performance gained from iteration.

Description

A kind of ofdm system inter-cell interference cancellation method based on IDMA

Technical field

The present invention relates to the technology of the presence of intercell interference inhibition of mobile communication system, specifically a kind of ofdm system inter-cell interference cancellation method based on IDMA.

Background technology

Presence of intercell interference is an intrinsic problem of cell mobile communication systems.It is very low that orthogonal frequency division multiplex OFDM technology drops to community internal interference, and presence of intercell interference becomes the main interference that affects systematic function.At present both at home and abroad to the more existing researchs of ofdm system presence of intercell interference inhibition technology, and domestic research to this concentrates on interference coordination, relatively less to interference cancellation techniques research.Patent of the present invention is paid close attention to the interference elimination method based on IDMA.

Interlacing multi-address IDMA (Interleave-Division Multiple Access) is a kind of multiple access communication mode, adopt Low Bit-rate Coding, utilize different interleaving device to distinguish different user, it has not only saved special frequency expansion sequence, and the method that can detect by iteration signal significantly reduces the complexity of Multiuser Detection, thus the performance of raising system.The domestic patent relevant to IDMA technology is less at present, does not relate to the patent that application IDMA technology is eliminated presence of intercell interference.

The Cellular Networks model of the ofdm system of accompanying drawing 1, in the signal of the cell base station that mobile subscriber can receive, large with the signal strength signal intensity of the cell base station of mobile subscriber's near distance, little with the signal strength signal intensity of the cell base station of mobile subscriber's distance.Therefore, while utilizing IDMA to carry out inter-cell interference cancellation, should consider the problem that each interference signal is strong and weak different, traditional IDMA multi-user test method be improved, to realize better inter-cell interference cancellation effect.

Summary of the invention

The object of the invention is to overcome the above-mentioned defect that prior art exists, a kind of ofdm system inter-cell interference cancellation method based on IDMA is provided, the present invention is applied to ofdm system IDMA and carries out inter-cell interference cancellation, built system model, and on traditional IDMA multi-user test method basis, the detection algorithm of baseband signal estimator ESE is improved, make it be applied to better inter-cell interference cancellation, concrete technical scheme is as follows.

An ofdm system inter-cell interference cancellation method based on IDMA, ofdm system comprises cell base station transmitter and mobile subscriber's receiver, the method is distinguished different cell base station transmitters by configuring different interleavers; Mobile subscriber's receiver adopts the method for IDMA Multiuser Detection to carry out inter-cell interference cancellation.

In the above-mentioned ofdm system inter-cell interference cancellation method based on IDMA, the signal treatment step of cell base station transmitter comprises:

(2.1) coding unit C encodes and spread processing to sending data;

(2.2) data of interleaver pi after coding unit is processed are carried out interleaving treatment; Different interlacing patterns is used in base station, different districts;

(2.3) inverse Fourier transform unit IFFT carries out inverse Fourier transform processing to the data after interweaving, and produces ofdm signal and sends by antenna.

In the above-mentioned ofdm system inter-cell interference cancellation method based on IDMA, the signal treatment step of mobile subscriber's receiver comprises:

(3.1) Fourier transform unit FFT, to antenna reception to ofdm signal carry out Fourier transform processing;

(3.2) channel estimator CHE, utilizes the pilot frequency information of the reception signal after FFT conversion to carry out channel estimating, obtains channel coefficients;

(3.3) baseband signal estimator ESE is 0 prior probability likelihood ratio information initializing;

(3.4) baseband signal estimator ESE, using reception signal after FFT processes, channel coefficients that channel estimator generates and prior probability likelihood ratio information as input, the detection algorithm of operation ESE, carries out Multiuser Detection, output multi-channel log-likelihood ratio information;

(3.5) each deinterleaver π ^-1, ESE output Mei road log-likelihood ratio information is carried out to deinterleaving, each deinterleaver is corresponding with the interleaver of each cell base station;

(3.6) each decoder DEC, the information after the deinterleaving of Dui Mei road is carried out decoding, generates log-likelihood ratio information; Meanwhile, the transmission data of the corresponding decoder export target of target cell base station cell base station;

(3.7) each interleaver pi, the log-likelihood ratio information that each DEC is generated interweaves; Each interleaver is identical with the interleaver of each cell base station; The prior probability likelihood ratio information generating that interweaves will be inputted baseband signal estimator;

(3.8) repeat above step (3.4) and carry out iteration to step (3.7), iterations is more, disturbs eradicating efficacy better.

In the above-mentioned ofdm system inter-cell interference cancellation method based on IDMA, the method of described Multiuser Detection is: mobile subscriber's receiver is according to the power of interference signal, all base stations beyond target cell base station T-BS are categorized as to strong jamming base station S-BS and weak jamming base station W-BS, the signal of W-BS is used as to Gaussian noise to be processed, the signal of T-BS and S-BS is carried out to iterative detection, thereby suppress the interference beyond T-BS, obtain the data estimator of T-BS.

In the above-mentioned ofdm system inter-cell interference cancellation method based on IDMA, the detection algorithm of described ESE is used as the signal of W-BS as Gaussian noise processing, and the signal of T-BS and S-BS is carried out to iterative detection, detection algorithm mathematical expression subrepresentation:

$e_{\mathrm{ESE}}=\left(x_k\left(j\right)\right)$

$=\log \left(\underset{m\∈(1,...,p)}{\underset{I_m\∈\left(\mathrm{0,1}\right)}{\mathrm{\Σ}}}\left(\exp \right\{-\frac{{(r\left(j\right)-(h_n+\underset{n\≠k,n\∈(1,...,p)}{\mathrm{\Σ}}{(-1)}^{I_{n-1}}{h}_n))}^2}{2\mathrm{Var}\left({\mathrm{\ζ}}_k\left(j\right)\right)}\}\·\underset{n\≠k,n\∈(1,...,p)}{\mathrm{\Π}}{\left({\exp \{e}_{\mathrm{DEC}}\left(x_n\left(j\right)\right)\right\})}^{(1-I_{n-1})})\right)$

$-\log \left(\underset{m\∈(1,...,p)}{\underset{I_m\∈\left(\mathrm{0,1}\right)}{\mathrm{\Σ}}}\left(\exp \right\{-\frac{{(r\left(j\right)-(-h_n+\underset{n\≠k,n\∈(1,...,p)}{\mathrm{\Σ}}{(-1)}^{I_{n-1}}{h}_n))}^2}{2\mathrm{Var}\left({\mathrm{\ζ}}_k\left(j\right)\right)}\}\·\underset{n\≠k,n\∈(1,...p)}{\overset{p}{\mathrm{\Π}}}{\left({\exp \{e}_{\mathrm{DEC}}\left(x_n\left(j\right)\right)\right\})}^{(1-I_{n-1})})\right)$

$\mathrm{Var}\left({\mathrm{\ζ}}_k\left(j\right)\right)=\frac{1}{J}\underset{j=1}{\overset{J}{\mathrm{\Σ}}}{(r\left(j\right)-\underset{k=1}{\overset{p}{\mathrm{\Σ}}}{h}_{k}E\left(x_k\left(j\right)\right))}^2$

Wherein,

$E\left(x_k\left(j\right)\right)=\tanh \left(\frac{e_{\mathrm{DEC}}\left(x_k\left(j\right)\right)}{2}\right)$

{ e _eSE(x _k(j)), k ∈ (1 ..., p) represent ESE output about x _k(j) log-likelihood ratio information, x _k(j) represent the data of j bit of k cell base station, p is the number of T-BS and S-BS, and J is the number of bits of present frame, and r (j) is the reception signal after FFT conversion, { h _k, k ∈ (1 ..., p) } be the channel coefficients that channel estimator generates, { e _dEC(x _k(j)), and k ∈ (1 ..., p) } be initialized as 0, in iteration, upgrade, be the prior probability log-likelihood ratio information that iteration loop generates, ζ _k(j) be the stack of interchannel noise and all W-BS interference signals, be similar to average and be 0, variance is Var (ζ _k(j) Gaussian Profile), this mathematic(al) representation acquiescence adopts BPSK modulation.

Compared with prior art, tool has the following advantages and technique effect in the present invention: adopt the method for IDMA Multiuser Detection, can obtain better interference rejection, and iterations is more by iteration, disturb eradicating efficacy better.

Accompanying drawing explanation

Fig. 1 is the Cellular Networks model of ofdm system;

Fig. 2 is the ofdm system model based on IDMA;

Fig. 3 is the structure of the coding unit of cell base station transmitter.

specific implementation method

Below in conjunction with accompanying drawing, enforcement of the present invention is described further, but enforcement of the present invention is not limited to this.

Ofdm system inter-cell interference cancellation method based on IDMA is to distinguish different cell base station transmitters by configuring different interleavers; Mobile subscriber's receiver is according to the power of interference signal, all base stations beyond target cell base station T-BS are categorized as to strong jamming base station S-BS and weak jamming base station W-BS, the signal of W-BS is used as to Gaussian noise to be processed, the signal of T-BS and S-BS is carried out to iterative detection, thereby suppress the interference beyond T-BS, obtain the data estimator of T-BS.

Ofdm system model based on IDMA as shown in Figure 2.Mainly contain two parts: cell base station transmitter and mobile subscriber's receiver.

Cell base station transmitter comprises three important component parts: coding unit, interleaver, inverse Fourier transform unit.The signal treatment step of cell base station transmitter comprises:

1) coding unit C, encodes and spread processing to sending data, and the structural representation of coding unit as shown in Figure 3, mainly comprises error correction code module and spread spectrum module;

2) interleaver pi, the data after coding unit is processed are carried out interleaving treatment, and base station, different districts is distinguished with different interlacing patterns;

3) inverse Fourier transform unit IFFT, carries out inverse Fourier transform processing to the data after interweaving, and produces ofdm signal and sends by antenna.

Mobile subscriber's receiver comprises six important component parts: Fourier transform unit, channel estimator, baseband signal estimator, deinterleaver and interleaver, decoder.The signal treatment step of mobile subscriber's receiver comprises:

1) Fourier transform unit FFT, to antenna reception to ofdm signal carries out Fourier transform processing;

2) channel estimator CHE, utilizes the pilot frequency information of the reception signal after FFT conversion to carry out channel estimating, obtains channel coefficients;

3) baseband signal estimator ESE is 0 prior probability likelihood ratio information initializing;

4) baseband signal estimator ESE, usings reception signal after FFT processes, channel coefficients that channel estimator generates and prior probability likelihood ratio information as input, and the detection algorithm of operation ESE, carries out Multiuser Detection, output multi-channel log-likelihood ratio information;

5) each deinterleaver π ^-1, ESE output Mei road log-likelihood ratio information is carried out to deinterleaving, each deinterleaver is corresponding with the interleaver of each cell base station;

6) each decoder DEC, the information after the deinterleaving of Dui Mei road is carried out decoding, generates log-likelihood ratio information; Meanwhile, the transmission data of the corresponding decoder export target of target cell base station cell base station;

7) each interleaver pi, the log-likelihood ratio information that each DEC is generated interweaves.Each interleaver is identical with the interleaver of each cell base station; The prior probability likelihood ratio information generating that interweaves will be inputted baseband signal estimator;

8) repeat above step 4) to step 7) carrying out iteration, iterations is more, disturbs eradicating efficacy better.

Consider the scene shown in accompanying drawing 1, this mobile subscriber can receive the signal (N value is very large) of N cell base station, and p is the number of T-BS and S-BS.The signal treatment step of cell base station transmitter comprises:

1) coding unit C encodes and spread processing to sending data, and coding unit mainly comprises error correction code module and spread spectrum module; For k cell base station, data sequence d _kthrough error correction code module, generated data sequence b _k, spread spectrum module is to b _kadopt predefined spreading code to carry out spread spectrum, in practical application, can to data sequence, carry out reprocessing with duplication code, spreading code has s bit, generated data sequence c _k=[c _k(1), c _k(2), c _k(3) ..., c _k(s)];

2) data of interleaver pi after coding unit is processed are carried out interleaving treatment, and base station, different districts is distinguished with different interlacing patterns; For k cell base station, the data sequence c that coding unit generates _kinput interleaver pi _kin, the data sequence x after being interweaved _k=[x _k(1), x _k(2), x _k(3) ..., x _k(s)];

3) inverse Fourier transform unit IFFT carries out inverse Fourier transform processing to the data after interweaving, and produces ofdm signal and sends by antenna;

● the signal treatment step of mobile subscriber's receiver comprises:

1) Fourier transform unit FFT to antenna reception to ofdm signal carry out Fourier transform processing, obtain signal r (j), j ∈ 1,2 ... J, J is the number of bits of present frame;

2) channel estimator CHE utilizes the pilot frequency information of the reception signal after FFT conversion to carry out channel estimating, obtains channel coefficients estimated value { h _k, k ∈ (1 ..., p) };

3) baseband signal estimator ESE, prior probability likelihood ratio information { e _dEC(x _k(j)), and k ∈ (1 ..., p) } be initialized as 0;

4) baseband signal estimator ESE, with signal r (j), j ∈ 1,2 ... J, channel coefficients { h _k, k ∈ (1 ..., p) } and prior probability likelihood ratio information { e _dEC(x _k(j)), and k ∈ (1 ..., p) } as input, the detection algorithm of operation ESE, carries out Multiuser Detection, output multi-channel log-likelihood ratio information { e _eSE(x _k(j)), and k ∈ (1 ..., p) };

5) each deinterleaver (π ^-1) Dui Mei road log-likelihood ratio information { e _eSE(x _k(j)), and k ∈ (1 ..., p) } carry out deinterleaving, export { e _eSE(c _k(j)), k ∈ (1 ..., p) }, each road deinterleaver is corresponding with the interleaver of each cell base station;

6) information { e after each decoder DECYi Mei road deinterleaving _eSE(c _k(j)), and k ∈ (1 ..., p) } be input, decoding generates the code symbols posterior probability { L of each cell base station _aPP(b _k), k ∈ (1 ..., p) }; If complete the iterations of setting, the L to target cell base station _aPP(b _k) adjudicate output data sequence

7), if iteration does not also complete, each DEC generates each road log-likelihood ratio information { e _dEC(c _k(j)), and k ∈ (1 ..., p) };

8) each interleaver pi Dui Mei road { e _dEC(c _k(j)), k ∈ (1 ..., p) } interweave, each road prior probability likelihood ratio { e generated _dEC(x _k(j)), k ∈ (1 ..., p) }, input ESE completes information updating, returns to step 4), realize iteration one time; Iterations is more, and inter-cell interference cancellation effect is better.

● the detection algorithm of ESE:

Receiving signal r (j) can be expressed as $r\left(j\right)=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{h}_n{x}_n\left(j\right)+n\left(j\right)$

Wherein { n (j) } is the additive white Gaussian noise of channel.Mobile subscriber's receiver, according to the power of interference signal, is categorized as strong jamming base station S-BS and weak jamming base station W-BS all base stations beyond target cell base station T-BS, and the number summation of T-BS and S-BS is p, and the expression formula of r (j) is rewritten into

$r\left(j\right)=\underset{n=1}{\overset{p}{\mathrm{\Σ}}}{h}_n{x}_n\left(j\right)+{\mathrm{\ζ}}_k\left(j\right)$

Wherein, represent the stack of all W-BS interference signals and interchannel noise.Adopt in the situation of BPSK modulation, according to central-limit theorem, ζ _k(j) be similar to that average is 0, variance is Var (ζ _k(j) Gaussian Profile).Receiving signal r (j) can be represented by a condition Gaussian probability-density function

$P\left(r\left(j\right)\right|x_1\left(j\right)=\±1,x_2\left(j\right)=\±1,...,x_p\left(j\right)=\±1)$

$=\frac{1}{\sqrt{2\mathrm{\πVar}\left({\mathrm{\ζ}}_k\left(j\right)\right)}}\exp \{-\frac{{(r\left(j\right)-(\±h_1\±h_2\±.....\±h_p))}^2}{2\mathrm{Var}\left({\mathrm{\ζ}}_k\left(j\right)\right)}\}---\left(1\right)$

Define k cell base station signal x _k(j) prior probability log-likelihood ratio

$e_{\mathrm{DEC}}\left(x_k\left(j\right)\right)=\log \left(\frac{P(x_k\left(j\right)=+1)}{P\left(x_k\left(j\right)\right)=-1}\right)---\left(2\right)$

ESE output log-likelihood ratio external information

$e_{\mathrm{ESE}}\left(x_k\left(j\right)\right)=\log \left(\frac{P\left(r\left(j\right)\right|x_k\left(j\right)=+1)}{P\left({r\left(j\right)|x}_k\left(j\right)\right)=-1}\right)---\left(3\right)$

By formula (2), can be obtained

$\left\{\begin{array}{c}P(x_k\left(j\right)=+1)=\frac{e^{e_{\mathrm{DEC}}\left(x_k\left(j\right)\right)}}{e^{e_{\mathrm{DEC}}\left(x_k\left(k\right)\right)}+1}\\ P(x_k\left(j\right)=-1)=\frac{1}{e^{e_{\mathrm{DWC}}\left(x_k\left(j\right)\right)}+1}\end{array}\right.---\left(4\right)$

Based on condition probability formula $P\left(A\right|B)=\underset{i}{\mathrm{\Σ}}P\left(A\right|B{C}_i)*P\left(C_i\right)$

Through directly calculating, can obtain the signal processing algorithm of ESE

$e_{\mathrm{ESE}}=\left(x_k\left(j\right)\right)$

$=\log \left(\underset{m\∈(1,...,p)}{\underset{I_m\∈\left(\mathrm{0,1}\right)}{\mathrm{\Σ}}}\left(\exp \right\{-\frac{{(r\left(j\right)-(h_n+\underset{n\≠k,n\∈(1,...,p)}{\mathrm{\Σ}}{(-1)}^{I_{n-1}}{h}_n))}^2}{2\mathrm{Var}\left({\mathrm{\ζ}}_k\left(j\right)\right)}\}\·\underset{n\≠k,n\∈(1,...,p)}{\mathrm{\Π}}{\left({\exp \{e}_{\mathrm{DEC}}\left(x_n\left(j\right)\right)\right\})}^{(1-I_{n-1})})\right)$

$-\log \left(\underset{m\∈(1,...,p)}{\underset{I_m\∈\left(\mathrm{0,1}\right)}{\mathrm{\Σ}}}\left(\exp \right\{-\frac{{(r\left(j\right)-(-h_n+\underset{n\≠k,n\∈(1,...,p)}{\mathrm{\Σ}}{(-1)}^{I_{n-1}}{h}_n))}^2}{2\mathrm{Var}\left({\mathrm{\ζ}}_k\left(j\right)\right)}\}\·\underset{n\≠k,n\∈(1,...p)}{\overset{p}{\mathrm{\Π}}}{\left({\exp \{e}_{\mathrm{DEC}}\left(x_n\left(j\right)\right)\right\})}^{(1-I_{n-1})})\right)$

$\mathrm{Var}\left({\mathrm{\ζ}}_k\left(j\right)\right)=\frac{1}{J}\underset{j=1}{\overset{J}{\mathrm{\Σ}}}{(r\left(j\right)-\underset{k=1}{\overset{p}{\mathrm{\Σ}}}{h}_{k}E\left(x_k\left(j\right)\right))}^2$

Wherein,

$E\left(x_k\left(j\right)\right)=\tanh \left(\frac{e_{\mathrm{DEC}}\left(x_k\left(j\right)\right)}{2}\right)$

● DEC signal processing flow:

1) input e _eSE(c _k(j)), to b _kcarry out soft estimation:

$L\left(b_k\right)=\underset{j=1}{\overset{S}{\mathrm{\Σ}}}{e}_{\mathrm{ESE}}\left(c_k\left(j\right)\right)=\underset{j=1}{\overset{S}{\mathrm{\Σ}}}\log \left(\frac{P\left(r\left(j\right)\right|c_k\left(j\right)=+1)}{P\left(r\left(j\right)\right|c_k\left(j\right)=-1)}\right)$

Wherein s is the figure place of spread spectrum duplication code;

2) to L (b _k) carry out the posteriori decoding of forward error correction coding, generate the code symbols posterior probability L of k cell base station _aPP(b _k),

3) spread spectrum generates L _aPP(c _k(j))=L _aPP(b _k), j=1,2 ..., S, and generate log-likelihood ratio information e _dEC(c _k(j))

$e_{\mathrm{DEC}}\left(c_k\left(j\right)\right)=L_{\mathrm{APP}}\left(c_k\left(j\right)\right)-e_{\mathrm{ESE}}\left(c_k\left(j\right)\right)$

$=\log \left(\frac{P(c_k\left(j\right)=+1|r\left(j\right))}{P(c_k\left(j\right)=-1\left|r\left(j\right)\right)}\right)-e_{\mathrm{ESE}}\left(c_k\left(j\right)\right)$

$=\log \left(\frac{P(c_k\left(j\right)=+1)}{P(c_k\left(j\right)=-1)}\right)$

4) complete iteration, to L _aPP(b _k) carry out hard decision, output estimation value

Claims (1)

1. the ofdm system inter-cell interference cancellation method based on IDMA, ofdm system comprises cell base station transmitter and mobile subscriber's receiver, it is characterized in that: by configuring different interleavers, distinguish different cell base station transmitters; Mobile subscriber's receiver adopts the method for IDMA Multiuser Detection to carry out inter-cell interference cancellation; The signal treatment step of cell base station transmitter comprises:

(2.1) coding unit C encodes and spread processing to sending data;

(2.2) interleaver data after coding unit is processed are carried out interleaving treatment; Different interlacing patterns is used in base station, different districts;

(2.3) inverse Fourier transform unit IFFT carries out inverse Fourier transform processing to the data after interweaving, and produces ofdm signal and sends by antenna;

The signal treatment step of mobile subscriber's receiver comprises:

(3.1) Fourier transform unit FFT, to antenna reception to ofdm signal carry out Fourier transform processing;

(3.2) channel estimator CHE, utilizes the pilot frequency information of the reception signal after FFT conversion to carry out channel estimating, obtains channel coefficients;

(3.3) baseband signal estimator ESE is 0 prior probability likelihood ratio information initializing;

(3.4) baseband signal estimator ESE, using reception signal after FFT processes, channel coefficients that channel estimator generates and prior probability likelihood ratio information as input, the detection algorithm of operation ESE, carries out Multiuser Detection, output multi-channel log-likelihood ratio information;

(3.5) each deinterleaver , ESE output Mei road log-likelihood ratio information is carried out to deinterleaving, each deinterleaver is corresponding with the interleaver of each cell base station;

(3.6) each decoder DEC, the information after the deinterleaving of Dui Mei road is carried out decoding, generates log-likelihood ratio information; Meanwhile, the transmission data of the corresponding decoder export target of target cell base station cell base station;

(3.7) each interleaver , the log-likelihood ratio information that each DEC is generated interweaves; Each interleaver is identical with the interleaver of each cell base station; The prior probability likelihood ratio information generating that interweaves will be inputted baseband signal estimator;

(3.8) repeat above step 3.4) to step 3.7) carrying out iteration, iterations is more, disturbs eradicating efficacy better; The method of described Multiuser Detection is: mobile subscriber's receiver is according to the power of interference signal, all base stations beyond target cell base station T-BS are categorized as to strong jamming base station S-BS and weak jamming base station W-BS, the signal of W-BS is used as to Gaussian noise to be processed, the signal of T-BS and S-BS is carried out to iterative detection, thereby suppress the interference beyond T-BS, obtain the data estimator of T-BS; The detection algorithm of described ESE is used as the signal of W-BS as Gaussian noise processing, and the signal of T-BS and S-BS is carried out to iterative detection, detection algorithm mathematical expression subrepresentation:

Wherein,

Wherein, represent ESE output about log-likelihood ratio information, the data that represent j bit of k cell base station, p is the number of T-BS and S-BS, J is the number of bits of present frame, the reception signal after FFT conversion, the channel coefficients that channel estimator generates, being initialized as 0, in iteration, upgrading, is the prior probability log-likelihood ratio information that iteration loop generates, be the stack of interchannel noise and all W-BS interference signals, be similar to average and be 0, variance is gaussian Profile, this mathematic(al) representation acquiescence adopts BPSK modulation.