CN102457453B - Signal detecting method under multipath channel and device - Google Patents

Abstract

The invention discloses the signal detecting method under a kind of multipath channel and device.Wherein, the method comprises: the Received signal strength utilizing channel estimation value and baseband frequency-domain, obtains the likelihood distance of described Received signal strength according to maximum posteriori criterion; Get the business opening the result of radical sign of the mould square of described likelihood distance and described channel estimating as Soft Inform ation; In units of a modulating-coding block, after carrying out unified displacement calibration to described Soft Inform ation, intercept high n position, input to the bit decoder of fixed point, wherein, n is the bit number that described bit decoder comprises the input parameter of sign bit.By the present invention, the error rate of the Soft Inform ation that the soft demodulator of fixed point exports can be reduced.

Description

Signal detecting method under multipath channel and device

Technical field

The present invention relates to the communications field, in particular to the signal detecting method under a kind of multipath channel and device.

Background technology

Modulation-demodulation technique is divided into analog-modulated solution mediation digital modulation and demodulation.Analog-modulated technology is that the frequency domain of signal is moved, and can carry out signals revivification by the method for coherent demodulation and non-coherent demodulation to modulation signal.Digital modulation is the principle of application input, is convenient to the design that receiving terminal detects to transmitting, and digital modulation signals can do detection reduction by the principle of certain input to signal.

Wherein, digital demodulation techniques is divided into the hard solution soft demodulation of mediation two kinds of methods.Hard demodulation is exactly implement direct method of adjudicating according to Received signal strength and maximum posteriori criterion to launching constellation.Soft-decision is the posterior probability ratio extracting constellation according to Received signal strength and maximum posteriori criterion, i.e. likelihood ratio.Under many circumstances, calculate the process more complicated of likelihood ratio, under the condition not affecting precision, generally get exponential part being similar to as likelihood ratio of likelihood ratio, i.e. likelihood distance.In actual applications, also can do further approximate to likelihood distance, as long as ensure that approximate mapping relations are dull.

In principle, system model can be expressed as:

$\begin{array}{cc}r=\mathrm{Hs}+n& s=\left\{\begin{array}{cc}1& p=1/2\\ -1& p=1/2\end{array}\right.\end{array}---\left(1\right)$

N obeys gaussian Profile, s represents the information source (1 represents 1, and-1 represents 0) of this Bit, and the sampling of the Received signal strength that r representative is once actual, H represents channel gain, and p represents the probability that s gets this value.

The output of the soft demodulator of numeral is the likelihood ratio of some Bit, can be expressed as:

$\begin{array}{c}\mathrm{LLR}=\frac{P(s=1/R=r)}{P(s=-1/R=r)}\\ =e^{-(\frac{{\left|\right|r-H\left|\right|}^2}{2N_0^2}-\frac{{\left|\right|r-(-H)\left|\right|}^2}{2N_0^2})}\end{array}---\left(2\right)$

R represents Received signal strength possible values, and what P represented is conditional probability.

Due to the monotonic function that likelihood ratio is Received signal strength r, so in fact, the output of demodulator is the approximation of getting likelihood ratio, i.e. likelihood distance, is represented by SI, then:

$\mathrm{SI}=\ln \left(\mathrm{LLR}\right)=-(\frac{{\left|\right|r-H\left|\right|}^2}{2N_0^2}-\frac{{\left|\right|r-(-H)\left|\right|}^2}{2N_0^2})\≈\mathrm{LLR}---\left(3\right)$

Formula (1) is substituted into formula (3) obtain:

$\mathrm{SI}=-\frac{{\left|\right|H\left|\right|}^2}{2N_0^2}({\left|\right|s-1+\frac{n}{H}\left|\right|}^2-{\left|\right|s+1+\frac{n}{H}\left|\right|}^2)---\left(4\right)$

Any modulation scheme, for a Bit, this Bit can be divided into get the set of the constellation of 0, be expressed as set A, and this Bit gets the set of the constellation of 1, is expressed as set B.Get set A and nearest two constellations of set B middle distance Received signal strength r respectively, as possible transmitting symbol, that system just can be similar to above-mentioned system model again.

For the 16Qam shown in Fig. 1, constellation wherein in square frame represents that this Bit is the constellation set of 0, this Bit of expression outside square frame is the constellation set of 1, the sampling of the Received signal strength that r representative is once actual, the constellation (two constellation point that the band namely in figure is filled) choosing two set middle distance r nearest asks for likelihood distance.

Consider that a bandwidth is the wireless channel of B, assuming that bandwidth is very large, so when signal transmits through this channel, decline will be caused because of multipath effect, now, in time domain, a shock pulse as source forcing is by this channel, will produce the time-domain response that has q multipath response, as shown in Figure 2.The response of this multipath will cause occurring serious frequency selective fading in the frequency domain spectra of channel, as shown in Figure 3.

It can thus be appreciated that, a broadband communicates, serious frequency selective fading may be occurred due to multipath effect, causing signal to noise ratio uneven in whole frequency range, in order to resist this frequency selective fading, in correlation technique, adopting multi-transceiver technology.At transmitting terminal, the low speed that original high-speed serial data utilizes multiple carrier wave to walk abreast is sent, to increasing the time domain length of the transmission symbol on each carrier wave, reduce the bandwidth that each symbol is done to need accordingly, thus, it is not very serious that the frequency selective fading response that whole frequency range seems very serious is become on single sub-carrier, as shown in Figure 4.When carrier number segmentation abundant, the width of carrier wave will be very little, now, the frequency domain response on single carrier wave can be regarded as a multiple constant, as shown in Figure 5.Wherein, the frequency domain decline in Fig. 5 can be shown:

H(ω)＝α(ω)e ^-jθ(ω)

In above-mentioned formula, can amplitude response be regarded as constant, i.e. α (ω) ≈ ρ, and regard constant as, i.e. θ (ω) ≈ φ by also approximate for phase response, therefore have:

By channel being divided into the method for each sub-channels, each subcarrier obtains the frequency-domain model of a flat fading.

Said method solves the problem of the frequency selective fading of subchannel self, but multiple subcarrier may be included for the modulating-coding block of a Unified coding, each subcarrier may be distributed in any one position of frequency domain, the decline of these subcarrier processes is each different, and its signal to noise ratio is also different.The significance bit exported due to the soft demodulator of fixed point is limited (consistent with fixed point decoder, for n), Soft Inform ation (these Soft Inform ation comprise a large amount of redundant informations) for the less subcarrier that declines in a modulating-coding block will take too much effective bit, for the Soft Inform ation of the larger subcarrier that declines, lost owing to there is no enough significance bits to represent, thus make the error rate of system can not follow the lifting of signal to noise ratio and reduce.

Summary of the invention

Main purpose of the present invention is to provide signal detecting method under a kind of multipath channel and device, can not follow the lifting of signal to noise ratio and the problem reduced with the error rate at least solving said system.

According to an aspect of the present invention, provide the signal detecting method under a kind of multipath channel, comprising: the Received signal strength utilizing channel estimation value and baseband frequency-domain, obtain the likelihood distance of described Received signal strength according to maximum posteriori criterion; Calculate the result opening radical sign of the mould square of described channel estimation value, get the business of described likelihood distance and described result as Soft Inform ation; In units of a modulating-coding block, after carrying out unified displacement calibration to described Soft Inform ation, intercept high n position, input to the bit decoder of fixed point, wherein, n is the bit number that described bit decoder comprises the input parameter of sign bit.

According to a further aspect in the invention, provide the signal supervisory instrument under a kind of multipath channel, comprising: acquisition module, for utilizing channel estimation value and base band at the Received signal strength of frequency domain, obtaining the likelihood distance of described Received signal strength according to maximum posteriori criterion; Computing module, for calculating the result opening radical sign of the mould square of described channel estimation value, gets the business of described likelihood distance and described result as Soft Inform ation; Scaling module, in units of a modulating-coding block, carries out unified displacement calibration to described Soft Inform ation; Output module, for intercepting the high n position of the Soft Inform ation after described scaling module displacement calibration, export to the bit decoder of fixed point, wherein, n is the bit number that described bit decoder comprises the input parameter of the number of meeting position.

Pass through the present invention, when detection signal, calculate the result opening radical sign of the mould square of described channel estimation value, get the business of likelihood distance and the above results as Soft Inform ation, thus the error rate solving system in prior art can not follow the lifting of signal to noise ratio and the problem that reduces, and then reduce the error rate of the Soft Inform ation that the soft demodulator of fixed point exports.

Accompanying drawing explanation

Accompanying drawing described herein is used to provide a further understanding of the present invention, and form a application's part, schematic description and description of the present invention, for explaining the present invention, does not form inappropriate limitation of the present invention.In the accompanying drawings:

Fig. 1 is according to the constellation set schematic diagram in the 16QAM of correlation technique;

Fig. 2 is the schematic diagram that in correlation technique, shock pulse produces multipath response;

Fig. 3 is the schematic diagram that in correlation technique, multipath response causes frequency selective fading;

Fig. 4 is the schematic diagram of the frequency selective fading in multi-transceiver technology;

Fig. 5 is the schematic diagram of the frequency domain response in multi-transceiver technology on single carrier wave;

Fig. 6 is the flow chart according to the signal detecting method under the multipath channel of the embodiment of the present invention;

Fig. 7 is the flow chart of input according to the preferred embodiment of the invention;

Fig. 8 is the structural representation according to the signal supervisory instrument under the multipath channel of the embodiment of the present invention;

Fig. 9 is the structural representation according to acquisition module in the preferred embodiment of the present invention;

Figure 10 is the structural representation of the signal supervisory instrument according to the preferred embodiment of the invention under multipath channel.

Embodiment

Hereinafter also describe the present invention in detail with reference to accompanying drawing in conjunction with the embodiments.It should be noted that, when not conflicting, the embodiment in the application and the feature in embodiment can combine mutually.

Before the technical scheme provided the embodiment of the present invention is described, first the proposition of the technical scheme of the embodiment of the present invention is described.

Under high s/n ratio condition, suppose that certain modulating-coding block just includes H _maxand H _minfrequency.This two frequency bins is expressed as A0, A1.So the likelihood distance of this two frequency bins can be expressed as:

$S{I}_{\max }=-\frac{{\left|\right|H_{\max }\left|\right|}^2}{2N_0^2}({\left|\right|s-1+\frac{n}{H_{\max }}\left|\right|}^2-{\left|\right|s+1+\frac{n}{H_{\max }}\left|\right|}^2)---\left(6\right)$

With

$S{I}_{\min }=-\frac{{\left|\right|H_{\min }\left|\right|}^2}{2N_0^2}({\left|\right|s-1+\frac{n}{H_{\min }}\left|\right|}^2-{\left|\right|s+1+\frac{n}{H_{\min }}\left|\right|}^2)---\left(7\right)$

Suppose that signal to noise ratio is enough large again soft Inform ation so after normalization can be expressed as:

SI _max＝1 (8)

$\begin{array}{c}S{I}_{\min }=\frac{-\frac{{\left|\right|H_{\min }\left|\right|}^2}{2N_0^2}({\left|\right|s-1+\frac{n}{H_{\min }}\left|\right|}^2-{\left|\right|s+1+\frac{n}{H_{\min }}\left|\right|}^2)}{-\frac{{\left|\right|H_{\max }\left|\right|}^2}{2N_0^2}({\left|\right|s-1+\frac{n}{H_{\max }}\left|\right|}^2-{\left|\right|s+1+\frac{n}{H_{\max }}\left|\right|}^2)}\\ =\frac{1}{\mathrm{\κ}}\end{array}---\left(9\right)$

In frequency selective fading channels, improve the transmitting power of transmitting terminal, H can be improved simultaneously _maxand H _minbut, can not change as can be seen here, when signal to noise ratio is enough large, the quality of the output Soft Inform ation of soft demodulator is determined by κ, improves the transmitting power of transmitting terminal, can not change the quality exporting Soft Inform ation.

Suppose there is one other channel, || H _max|| ²=|| H _min|| ², it also has two frequency bins, and a frequency is subject to noise jamming, another frequency receives this two frequency bins is expressed as B0, B1 and having then the Soft Inform ation of this two frequency bins can be expressed as:

$S{I}_{\max }=-\frac{{\left|\right|H_{\min }\left|\right|}^2}{2N_0^2}({\left|\right|s-1+\frac{n_0}{H_{\min }}\left|\right|}^2-{\left|\right|s+1+\frac{n_0}{H_{\min }}\left|\right|}^2)---\left(11\right)$

With

$S{I}_{\min }=-\frac{{\left|\right|H_{\min }\left|\right|}^2}{2N_1^2}({\left|\right|s-1+\frac{n_1}{H_{\min }}\left|\right|}^2-{\left|\right|s+1+\frac{n_1}{H_{\min }}\left|\right|}^2)---\left(12\right)$

Suppose that signal to noise ratio is enough large again $10\log \left(\frac{{\left|\right|H_{\min }\left|\right|}^2}{2N_0^2}\right)>20\mathrm{db},10\log \left(\frac{{\left|\right|H_{\min }\left|\right|}^2}{2N_1^2}\right)>20\mathrm{db},$ Soft Inform ation then after normalization can be expressed as:

SI _max＝1 (13)

$\begin{array}{c}S{I}_{\min }=\frac{-\frac{{\left|\right|H_{\min }\left|\right|}^2}{2N_1^2}({\left|\right|s-1+\frac{n_1}{H_{\min }}\left|\right|}^2-{\left|\right|s+1+\frac{n_1}{H_{\min }}\left|\right|}^2)}{-\frac{{\left|\right|H_{\min }\left|\right|}^2}{2N_0^2}({\left|\right|s-1+\frac{n_0}{H_{\min }}\left|\right|}^2-{\left|\right|s+1+\frac{n_0}{H_{\min }}\left|\right|}^2)}\\ =\frac{1}{\mathrm{\κ}}\end{array}---\left(14\right)$

As can be seen here, A1 and B0 has identical channel gain, and is subject to identical noise jamming, but respective Soft Inform ation but differs greatly; The channel gain that contrary A1 with B1 tool is identical, but be subject to different noise jamming, but respective Soft Inform ation is consistent.At this moment, the Soft Inform ation of channel A follows the Soft Inform ation of channel B to be the same, and that is the high signal power of channel A, does not bring the lifting of the quality of Soft Inform ation.

Fig. 6 is the flow chart according to the signal detecting method under the multipath channel of the embodiment of the present invention, and the method is applied in the soft modulator of fixed point, and as shown in Figure 6, the method mainly comprises the following steps:

Step S602, utilizes the Received signal strength of channel estimation value and baseband frequency-domain, obtains the likelihood distance of described Received signal strength according to maximum posteriori criterion;

Such as, first prior information can be utilized to estimate the channel response of each current carrier wave, obtain channel estimation value, then according to channel estimation value and the Received signal strength of each carrier wave, utilize above-mentioned formula (3), calculate the likelihood distance SI of each bit that the soft modulator of fixed point exports:

$\mathrm{SI}=-(\frac{{\left|\right|r-H\left|\right|}^2}{2N_0^2}-\frac{{\left|\right|r-(-H)\left|\right|}^2}{2N_0^2});$

Wherein, r is described Received signal strength, and H is channel gain, N ₀for noise power.

Particularly, the above-mentioned likelihood distance of each Bit of Received signal strength can be obtained by following steps:

Step 1, carries out poll to all Bit of constellation, and all constellation point are divided into two set, set A represents that this Bit gets the constellation set of 0, and set B represents that this Bit gets the constellation set of 1;

Step 2, according to constellation structures, asks for the distance of Received signal strength r to each constellation point according to the following equation, these distances also can be divided into two set according to the set belonging to his constellation, have D respectively _aand D _brepresent;

wherein, r represents Received signal strength, and H represents channel estimating, and s represents constellation point, and the probable value of constellation is specified by modulation system and agreement.

Step 3, finds out set D _aand D _bin minimum range min (D _a) and min (D _b);

Step 4, by above-mentioned two minimum range min (D _a) and min (D _b) subtract each other, namely obtain likelihood distance.

Step S604, gets the business opening the result of radical sign of the mould square of likelihood distance and the described channel estimating obtained in step S602 as Soft Inform ation;

Preferably, in embodiments of the present invention, only has operation multipath channel just being performed to step S604, therefore, before step S604, the method can also comprise: the channel estimation value (channel estimation value namely in step S602) according to a modulating-coding block carries out estimation of channel characteristics to channel, determines that the channel that described modulating-coding block experiences is multipath channel.

Such as, can judge whether the channel that described modulating-coding block experiences is multipath channel by following steps:

Step 1, obtains the mean value H of this modulating-coding block in the channel estimating of each carrier wave _avg;

Step 2, obtains the mould square σ of the channel estimating of each carrier wave and the difference of above-mentioned mean value ²(i), σ ²(i)=|| H (i)-H _avg|| ², i=1,2 ... .., N represent carrier wave sequence number, and N is current total number subcarriers;

Step 3, to σ ²i () is cumulative is averaging, and obtains multipath characteristics parameter, judges whether this multipath characteristics parameter exceedes default multi-path threshold, if so, then determine that the channel that this modulating-coding block experiences is multipath channel.

If judge that the channel that modulating-coding block experiences is not multipath channel, then directly get the likelihood distance that calculates as Soft Inform ation.

Step S606, in units of a modulating-coding block, after carrying out unified displacement calibration to Soft Inform ation, intercept high n position, as the Soft Inform ation exported, input to the bit decoder of fixed point, wherein, n is the bit number that described bit decoder comprises the input parameter of sign bit.

Preferably, n=8.In actual applications, n is identical with the significance bit that soft demodulator exports.

By the said method that the embodiment of the present invention provides, making full use of of the Bit position of Soft Inform ation can be ensured, namely in a modulating-coding block, have at least the highest order of data to be significance bits, thus ensure that the accuracy of the Soft Inform ation that the soft modulator of fixed point exports, reduce the error rate.

Fig. 7 is the flow chart of input according to the preferred embodiment of the invention, and as shown in Figure 7, in the preferred embodiment, the soft demodulator of fixed point detects signal and mainly comprises the following steps:

Step 701, utilizes prior information to estimate the channel response of each carrier wave, is called channel estimating;

Step 702, the likelihood distance of each Bit of Received signal strength is asked for according to channel estimating, Received signal strength and formula (3):

Such as, the likelihood distance of each Bit can be gathered by following steps carrier wave:

Step 1, carries out poll to all Bit of this constellation, and all constellation point are divided into two set, set A represents that this Bit gets the constellation set of 0, and set B represents that this Bit gets the constellation set of 1;

Step 2, according to constellation structures, asks for the distance of Received signal strength r to each constellation point, these distances also can be divided into two set according to the set belonging to his constellation, have D respectively _aand D _brepresent;

Step 3, finds out set D _aand D _bin minimum range min (D _a) and min (D _b);

Step 4, by above-mentioned two minimum range min (D _a) and min (D _b) subtract each other, namely obtain likelihood distance;

Step 703, the channel estimating according to a modulating-coding block carries out estimation of channel characteristics to channel, judges whether the channel that this modulating-coding block experiences is multipath channel, if, then enter step 704, otherwise the likelihood distance getting each Bit is as Soft Inform ation, enters step 705;

Such as, can judge whether the channel that this modulating-coding block experiences is multipath channel by following steps:

Step 1, asks for the mean value H of the channel estimating of whole modulating-coding block _avg;

Step 2, asks for the mould square of channel estimating with the difference of average channel estimation of each carrier wave, σ ²(i)=|| H (i)-H _avg|| ², i=1,2 ... ..N represents carrier wave sequence number;

Step 3, to σ ²i () is cumulative is averaging, as multipath characteristics parameter, when multipath characteristics parameter is greater than default multi-path threshold, export 1, the channel of instruction experience is multipath channel, otherwise exports 0, and the channel of instruction experience is not multipath channel, in actual applications, above-mentioned default multi-path threshold can be set according to test result.

It should be noted that, illustrate although above-mentioned whether a kind of channel judging that modulating-coding block experiences is multipath channel method, be not limited to this, in actual applications, also other method can be adopted to judge, such as, judge by doing correlation computations to each channel.

Step 704, to likelihood distance divided by channel estimating mould square open radical sign

Step 705, to Soft Inform ation in units of a modulating-coding block, carry out unifying calibration, to ensure making full use of of the Bit position of Soft Inform ation, namely, in a modulating-coding block, have at least the highest order of data to be significance bits, then intercept high 8Bit, after completing the Soft Inform ation calculating of a modulating-coding block, give decoder for decoding by result.

Fig. 8 is the structural representation according to the signal supervisory instrument under the multipath channel of the embodiment of the present invention, this device is arranged in the soft modulator of fixed point, as shown in Figure 8, this device comprises: acquisition module 10, for utilizing channel estimation value and base band at the Received signal strength of frequency domain, obtain the likelihood distance of described Received signal strength according to maximum posteriori criterion; Computing module 20, for getting the business opening the result of radical sign of the mould square of described likelihood distance and described channel estimating as Soft Inform ation; Scaling module 30, in units of a modulating-coding block, carries out unified displacement calibration to described Soft Inform ation; Output module 40, for intercepting the high n position of the Soft Inform ation after described scaling module displacement calibration, export to the bit decoder of fixed point, wherein, n is the bit number that described bit decoder comprises the input parameter of sign bit.

In a preferred implementation of the embodiment of the present invention, n=8.

As shown in Figure 9, in another preferred implementation of the embodiment of the present invention, acquisition module 10 can comprise: estimator module 100, for the channel response utilizing prior information to estimate the carrier wave that described Received signal strength uses, obtains described channel estimation value; Calculating sub module 102, for described channel estimation value and described Received signal strength, obtains the likelihood distance SI of each bit of described Received signal strength according to formulae discovery below:

$\mathrm{SI}=-(\frac{{\left|\right|r-H\left|\right|}^2}{2N_0^2}-\frac{{\left|\right|r-(-H)\left|\right|}^2}{2N_0^2});$

Wherein, r is described Received signal strength, and H is channel gain, N ₀for noise power.

In another preferred implementation of the embodiment of the present invention, as shown in Figure 10, this device can also comprise: judge module 50, for the channel estimation value according to a modulating-coding block, estimation of channel characteristics is carried out to channel, determine whether the channel that described modulating-coding block experiences is multipath channel, if so, triggers described computing module, otherwise, trigger described scaling module.

Such as, judge module 50 first can ask for the mean value H of the channel estimating of whole modulating-coding block _avg; Then the mould square of channel estimating with the difference of average channel estimation of each carrier wave is asked for, σ ²(i)=|| H (i)-H _avg|| ², i=1,2 ... ..N represents carrier wave sequence number; Again to σ ²i () is cumulative is averaging, and as multipath characteristics parameter, when multipath characteristics parameter is greater than default multi-path threshold, exports 1, and the channel of instruction experience is multipath channel, otherwise exports 0, and the channel of instruction experience is not multipath channel.

From above description, can find out, in embodiments of the present invention, for the feature of multipath channel and the soft demodulator of fixed point, by measuring the multipath characteristics of channel, result according to measuring selects suitable Soft Inform ation approximate data, improves the output performance of soft demodulator, reaches the object of elevator system detection perform.Further, the embodiment of the present invention takes into account multipath channel and flat channel, reduces system to the dependence of channel, simultaneously the detection perform of elevator system in deep frequency selective fading channel, and method is simple, flexible, practical.

Obviously, those skilled in the art should be understood that, above-mentioned of the present invention each module or each step can realize with general calculation element, they can concentrate on single calculation element, or be distributed on network that multiple calculation element forms, alternatively, they can realize with the executable program code of calculation element, thus, they can be stored and be performed by calculation element in the storage device, and in some cases, step shown or described by can performing with the order be different from herein, or they are made into each integrated circuit modules respectively, or the multiple module in them or step are made into single integrated circuit module to realize.Like this, the present invention is not restricted to any specific hardware and software combination.

The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (10)

1. the signal detecting method under multipath channel, is characterized in that, comprising:

Utilize the Received signal strength of channel estimation value and baseband frequency-domain, obtain the likelihood distance of described Received signal strength according to maximum posteriori criterion;

Calculate the result opening radical sign of the mould square of described channel estimation value, get the business of described likelihood distance and described result as Soft Inform ation;

In units of a modulating-coding block, after carrying out unified displacement calibration to described Soft Inform ation, intercept high n position, input to the bit decoder of fixed point, wherein, n is the bit number that described bit decoder comprises the input parameter of sign bit.

2. method according to claim 1, is characterized in that, utilizes described channel estimation value and described Received signal strength, obtains described likelihood distance comprise according to maximum posteriori criterion:

Utilize prior information to estimate the channel response of the carrier wave that described Received signal strength uses, obtain described channel estimation value, wherein, described channel estimation value is channel gain H;

According to described channel estimation value and described Received signal strength, obtain the likelihood distance SI of each bit of described Received signal strength according to formulae discovery below:

$\mathrm{SI}=-(\frac{{\left|\right|r-H\left|\right|}^2}{2N_0^2}-\frac{{\left|\right|r-(-H)\left|\right|}^2}{2N_0^2});$

Wherein, r is described Received signal strength, and H is channel gain, N ₀for noise power.

3. method according to claim 1, is characterized in that, calculating the result opening radical sign of mould square of described channel estimation value, get the business of described likelihood distance and described result as before Soft Inform ation, described method also comprises:

Channel estimation value according to a modulating-coding block carries out estimation of channel characteristics to channel, determines that the channel that described modulating-coding block experiences is multipath channel.

4. method according to claim 3, is characterized in that, determines that the channel that described modulating-coding block experiences is that multipath channel comprises:

Obtain the mean value H of described modulating-coding block at the channel estimation value of each carrier wave _avg;

Obtain the mould square σ of the channel estimation value of each carrier wave and the difference of described mean value ²(i), σ ²(i)=|| H (i)-H _avg|| ², i=1,2 ... .., N represent carrier wave sequence number, and N is current total number subcarriers;

To σ ²i () is cumulative is averaging, and obtains multipath characteristics parameter, judges whether described multipath characteristics parameter exceedes default multi-path threshold, if so, then determine that the channel that described modulating-coding block experiences is multipath channel.

5. the method according to claim 3 or 4, is characterized in that, if determine that the channel that described modulating-coding block experiences is not multipath channel, described method also comprises:

In units of a modulating-coding block, after carrying out unified displacement calibration to described likelihood distance, intercept high n position, input to the bit decoder of fixed point, wherein, n is the bit number of described bit decoder modulating-coding.

6. method according to any one of claim 1 to 4, is characterized in that, described n=8.

7. the signal supervisory instrument under multipath channel, is characterized in that, comprising:

Acquisition module, for utilizing channel estimation value and base band at the Received signal strength of frequency domain, obtains the likelihood distance of described Received signal strength according to maximum posteriori criterion;

Computing module, for calculating the result opening radical sign of the mould square of described channel estimation value, gets the business of described likelihood distance and described result as Soft Inform ation;

Scaling module, in units of a modulating-coding block, carries out unified displacement calibration to described Soft Inform ation;

Output module, for intercepting the high n position of the Soft Inform ation after described scaling module displacement calibration, export to the bit decoder of fixed point, wherein, n is the bit number that described bit decoder comprises the input parameter of the number of meeting position.

8. device according to claim 7, is characterized in that, described acquisition module comprises:

Estimator module, for the channel response utilizing prior information to estimate the carrier wave that described Received signal strength uses, obtains described channel estimation value, and wherein, described channel estimation value is channel gain H;

Calculating sub module, for described channel estimation value and described Received signal strength, obtains the likelihood distance SI of each bit of described Received signal strength according to formulae discovery below:

$\mathrm{SI}=-(\frac{{\left|\right|r-H\left|\right|}^2}{2N_0^2}-\frac{{\left|\right|r-(-H)\left|\right|}^2}{2N_0^2});$

Wherein, r is described Received signal strength, and H is channel gain, N ₀for noise power.

9. the device according to claim 7 or 8, is characterized in that, described device also comprises:

Judge module, carries out estimation of channel characteristics for the channel estimation value according to a modulating-coding block to channel, determines whether the channel that described modulating-coding block experiences is multipath channel, if so, triggers described computing module, otherwise, trigger described scaling module.

10. the device according to claim 7 or 8, is characterized in that, described n=8.