CN101388712A - Distance measuring signal processing method and system for OFDM access system - Google Patents

Abstract

The invention provides a method for processing OFDMA distance signals and a system thereof, which are used to process the distance signals of a wireless communication system which uses the OFDMA technique to obtain a practical ranging code and timing offset in a present ranging time slot. A normal ranging method in an existing technique is a bi-dimensional ergodic process, the complexity of computation is high, and a frequency domain difference ranging method has the problem that the detecting performance of the ranging code and the timing estimating performance are worse due to multi-user disturbance. The processing method of the invention and the system thereof firstly calculate frequency domain difference cross-correlation functions of neighboring carriers in a range channel, then a first screening threshold is calculated, a candidate key set is screened according to the first screening threshold, estimated timing offset is calculated, then, the cross-correlation functions and a second screening threshold between a ranging code frequency domain sequence and a local ranging code are calculated, finally, the practical timing offset is calculated, and the practical ranging code is screened from the candidate key set. The method and the system of the invention can guarantee the ranging accuracy and also can guarantee lower complexity of computation.

Description

A kind of orthogonal frequency division multiple access system distance measuring signal processing method and system

Technical field

The present invention relates to the radio communication ranging technology, relate in particular to a kind of orthogonal frequency division multiple access system distance measuring signal processing method and system.

Background technology

IEEE 802.16d/e communication system uses OFDM (OFDM)/OFDM to insert (OFDMA) communication plan, promptly descending (data are transmitted to all users in the base station) adopts the OFDM technology, up (user transmits data to the base station) adopts the OFDMA technology, so users different when up transmit data to the base station by different subcarrier set, if do not reach between each user regularly synchronously, to lose the orthogonality between the subcarrier so, thereby cause the interference between the data on the subcarrier.So the timing of each up subcarrier is extremely important for the OFDMA technology synchronously.

For the timing that keeps each subcarrier synchronous, IEEE 802.16d/e standard definition range finding finish up timing synchronously and adjust each user's transmitted power, and defined corresponding ranging code set and the one or more range channel of range finding.Range finding is carried out in frequency domain usually, when finding range, the user selects a ranging slot earlier at random in the ranging slot set of system assignment, and in the ranging code set that distributes, select a ranging code at random, by range channel this ranging code is transferred to the base station then, the base station detects ranging code and corresponding timing offset (round-trip delay) thereof according to received distance measuring signal, the base station feedback message (being RNG_RSP message) that will comprise ranging code and corresponding timing offset and ranging slot is sent to each user in the mode of broadcasting then, ranging slot that each user takies according to oneself again and ranging code are looked for out one's own feedback message from broadcast message, the user judges according to the state information in the feedback message (continuing or success) whether the result of range finding and decision proceed range finding.Above-mentioned ranging code is the pseudo-random binary sequence (PRBS) of binary phase shift keying in frequency domain (BPSK) modulation.A plurality of in addition range finding users allow to collide on same range channel, and the number of users of finding range simultaneously on same time slot is subject to the their cross correlation and the channel distortion of ranging code.Moreover range finding has comprised initial ranging, switching range finding, bandwidth request and cycle range finding, and wireless communication system distributes different ranging code set at all different ranging process.

Above-mentioned base station detects the timing offset of ranging code and correspondence thereof from received distance measuring signal common method is a two-dimentional traversal method.This method is used a frequency-domain correlator group, a ranging code in the corresponding ranging code set of each correlator, in addition because different range finding users has different timing offset, above-mentioned correlator bank causes phase place rotations different in the frequency domain, so also will be made the traversal of an one dimension to possible timing offset.This shows that location algorithm commonly used is a two-dimentional ergodic process at ranging code set and possible timing offset.But this kind method computation complexity is very high, and performance is limited under the frequency-selective channel condition.

For overcoming the existing variety of problems of above-mentioned two-dimentional traversal method, the scheme that has proposed Differential Detection in the 3rd IEEE information technology and application international conference in " Differtial Detection Scheme WithCombining Multiple FFT Blocks for OFDMA Ranging of IEEE 802.16e " that people such as Doo Hwan Lee deliver is come the decline of contrary frequency selectivity, but the scheme of its proposition requires ranging code to use differential modulation, and ranging code uses in 802.16e OFDMA system is the BPSK modulation, so also there are some difficulties in actual applications in the method that this scheme proposed.

Altera corp has also proposed the scheme that a kind of frequency domain differential demodulation detects in " WiMAX OFDMA Ranging " operational manual of delivering in August, 2006, it will travel through the two dimension traversal for one dimension by the frequency domain differential demodulation that calculates adjacent sub-carrier in the range channel, it relatively detects ranging code by amplitude and the predefined thresholding of getting correlation function in addition, get the phase place of correlation function and estimate timing offset, detection for ranging code, the setting of thresholding is relevant with actual user's quantity with the quantity of the ranging code of current system assignment, make to set become unusual difficulty of a suitable thresholding, an inappropriate thresholding will cause the detection performance decrease.Set thresholding by the frequency domain energy that calculates on the range channel in the scheme that altera corp proposed, the method for this setting thresholding exists a plurality of range finding users also infeasible under case of collision on the same range channel.

Set the problem of being brought for overcoming above-mentioned thresholding, publication number is that the United States Patent (USP) of US 2007/0058524 A1 has proposed the scheme that a kind of frequency domain differential demodulation detects, this scheme was divided into for two steps with the setting of thresholding, first thresholding that the first step is set is used for determining whether current ranging slot exists ranging code, and second thresholding that second step was set is used for the ranging code that definite current time slots comprises.But, when setting first thresholding, must obtain noise variance earlier, and actual central noise variance is to be difficult to obtain, when setting second thresholding, must obtain received power actual on the range channel, when existing a plurality of users to find range, because the phase mutual interference between the different ranging codes is so this patent can't obtain actual reception power, so be difficult to accurately record second thresholding.So also there are problems in actual applications in this scheme.

Above-mentioned two frequency domain differential demodulation detection schemes also have problems when the estimation of timing offset except detecting this problem of poor-performing.Above-mentioned detection scheme utilizes the phase place of correlation function to carry out timing estimation, there is the problem of phasing back in this method, can be subjected to the influence of multi-user interference in addition, thereby the timing offset estimated performance of frequency domain differential demodulation detection scheme is relatively poor, can't satisfies the synchronous requirement of timing of up-link.

Therefore, how to provide a kind of orthogonal frequency division multiple access system distance measuring signal processing method and system guaranteeing accurately to obtain ranging code and timing offset, and reduce computation complexity simultaneously, become the technical problem that industry needs to be resolved hurrily.

Summary of the invention

The object of the present invention is to provide a kind of orthogonal frequency division multiple access system distance measuring signal processing method and system, can guarantee the accuracy of finding range, can guarantee lower computation complexity in addition by described method and system.

The object of the present invention is achieved like this: a kind of orthogonal frequency division multiple access system distance measuring signal processing method, be used for the distance measuring signal of wireless communication system with base station and user side is handled to draw actual ranging code and corresponding actual timing offset thereof in the current ranging slot, this orthogonal frequency division multiple access system is used for the up link of wireless communication system, the corresponding range finding of this wireless communication system is provided with ranging slot, range channel, the local Candidate key set and the first and second default thresholdings, this method may further comprise the steps: (1) carries out analog-to-digital conversion to obtain digital signal to the received analog signal in base station; (2) digital signal that will change gained is stored in the data buffer; (3) from this data buffer, take out two fast fourier transform windows time domain sequences of current ranging slot and it is carried out fast fourier transform and obtain two frequency domain sequences; (4) from this two frequency domain sequence, isolate the pairing frequency domain sequence of range channel; (5) the isolated frequency domain sequence of institute is carried out frequency domain differential demodulation computing cross-correlation and result of calculation added up to obtain the difference cross-correlation function; (6) the difference cross-correlation function is carried out modulo operation; (7) calculate the first screening thresholding according to the modulo operation result and the first default thresholding; (8) mould value among the modulo operation result is set at Candidate key greater than first ranging code that screens the difference cross-correlation function correspondence of thresholding, and it is stored to the Candidate key set memory that is used for storing the Candidate key set; (9) calculate according to the difference cross-correlation function and estimate timing offset; (10) determine actual timing offset hunting zone according to estimating timing offset; (11) isolated two frequency domain sequences in the step (4) are added up obtaining cross-correlation function with local Candidate key set carrying out computing cross-correlation and with result of calculation respectively, and cross-correlation function is carried out modulo operation; (12) calculate the second screening thresholding according to the cross-correlation function modulo operation result and the second default thresholding; (13) from the Candidate key set, filter out actual ranging code according to the second screening thresholding; (14) search out actual timing offset according to cross-correlation function modulo operation result and actual timing offset hunting zone.

In above-mentioned orthogonal frequency division multiple access system distance measuring signal processing method, this method between step (9) and step (10), also comprise the Candidate key correspondence that detects in the Candidate key set estimate whether timing offset phasing back takes place and when counter-rotating with its compensation to there not being inverted status.

The present invention also provides a kind of orthogonal frequency division multiple access system distance measuring signal treatment system, be used for the distance measuring signal of wireless communication system with base station and user side is handled to draw actual ranging code and corresponding actual timing offset thereof in the current ranging slot, this orthogonal frequency division multiple access system is used for the up link of wireless communication system, the corresponding range finding of this wireless communication system is provided with ranging slot, range channel, the local Candidate key set and the first and second default thresholdings, this distance measuring signal treatment system comprises and is linked in sequence and is used for successively the received analog signal in base station is carried out analog-to-digital conversion to obtain the analog to digital converter of digital signal, be used for the digital signal of conversion gained is carried out the data in buffer buffer, be used for taking out two fast fourier transform windows time domain sequences of current ranging slot and it being carried out fast fourier transform with fast fourier transformer that obtains two frequency domain sequences and the demultiplexer that is used for isolating from two frequency domain sequences of conversion gained pairing two frequency domain sequences of range channel from data buffer, this distance measuring signal treatment system also comprises: be connected behind the demultiplexer and be respectively applied for isolated two frequency domain sequences of institute are carried out the frequency domain differential demodulation computing cross-correlation, the Candidate key detector of timing offset is gathered and estimated to the computing of difference cross-correlation function and the first screening thresholding computing to obtain Candidate key, be used for by the frequency domain computing cross-correlation, the cross-correlation function computing and the second screening thresholding computing and from Candidate key set, detect ranging code and detect the ranging code and the timing offset detector of actual timing offset, wherein, this first screening thresholding is used for screening and draws the Candidate key set, this first screening thresholding computing is carried out according to the difference cross-correlation function and the first default thresholding, this second screening thresholding is used for drawing actual ranging code from Candidate key set screening, and this second screening thresholding computing is carried out according to the cross-correlation function and the second default thresholding.

In above-mentioned orthogonal frequency division multiple access system distance measuring signal treatment system, this orthogonal frequency division multiple access system distance measuring signal treatment system also comprises and being arranged between Candidate key detector and ranging code and timing offset detector, be used for detecting the Candidate key set the Candidate key correspondence estimate whether timing offset phasing back takes place and when counter-rotating with its compensation to the phasing back detection and the compensator that do not have inverted status.

In above-mentioned orthogonal frequency division multiple access system distance measuring signal treatment system, this Candidate key detector comprise be used for demultiplexer isolated two frequency domain sequences respectively with two difference computing cross-correlation devices of local Candidate key set carrying out difference computing cross-correlation, be used for two first accumulators that the result with the difference computing cross-correlation adds up respectively, be used for the accumulation result of two first accumulators is carried out modulo operation respectively to obtain two first modulo operation devices of corresponding difference cross correlation measure flow function, be used to store the difference cross correlation measure flow function memory of two first modulo operation device operation results, be used to store the Candidate key set memory of Candidate key set, be used for calculating the first screening thresholding according to the difference cross correlation measure flow function and the first default thresholding, and according to the first screening thresholding difference cross correlation measure flow function is screened, and will be set at Candidate key greater than the pairing ranging code of difference cross correlation measure flow function of the first screening thresholding and it is stored to the Candidate key screening washer of Candidate key set memory, be used for accumulation result according to two first accumulators calculate estimate timing offset estimate the timing offset calculator and be used to store estimate timing offset estimate the timing offset memory.

In above-mentioned orthogonal frequency division multiple access system distance measuring signal treatment system, this ranging code and timing offset detector comprise and being used for according to estimating the hunting zone calculator that timing offset calculates actual timing offset hunting zone, be used for carrying out the compensation branch road selector that the phase compensation branch road is chosen according to the correlation function that difference cross correlation measure flow function memory is stored, be used for demultiplexer isolated two frequency domain sequences respectively with two computing cross-correlation devices of local Candidate key set carrying out computing cross-correlation, be used for the result of computing cross-correlation is added up respectively to obtain two second accumulators of correlation function, the correlation function of gained of being used for adding up carries out modulo operation to obtain two second modulo operation devices of corresponding cross correlation measure flow function, be used to store the cross correlation measure flow function memory of the cross correlation measure flow function of two second modulo operation device gained, be used for inquiring the actual timing offset requestor of maximum pairing actual timing offset in actual timing offset hunting zone of cross correlation measure flow function, be used for calculating the second screening thresholding, and two cross correlation measure flow functions screened with ranging code screening washer that obtains actual ranging code and actual timing offset memory and the actual ranging code memory that is respectively applied for actual timing offset of storage and actual ranging code according to the second screening thresholding according to the two cross correlation measure flow functions and the second default thresholding.

Compare with two-dimentional traversal method commonly used of the prior art, the one dimension that orthogonal frequency division multiple access system distance measuring signal processing method of the present invention and system reduce to ranging code and timing offset by frequency domain differential demodulation with the two dimension traversal travels through, and has reduced the complexity of calculating greatly.

Compare with frequency domain differential demodulation detection scheme of the prior art, orthogonal frequency division multiple access system distance measuring signal processing method of the present invention and system filter out the Candidate key set of covering scope greater than actual ranging code by the first screening thresholding earlier, and then from Candidate key set, filter out actual ranging code by the second screening thresholding, so improved the performance that detects; The present invention is divided into the estimation of timing offset and estimates timing offset and actual timing offset inquired about for two steps in addition, has eliminated the influence of multi-user interference to timing estimation, has improved the timing offset estimation performance.

Generally speaking, the present invention has improved the detection performance and the timing offset estimated performance of frequency domain differential demodulation detection scheme greatly on the basis that increases limited computation complexity.

Description of drawings

Orthogonal frequency division multiple access system distance measuring signal processing method of the present invention and system are provided by following embodiment and accompanying drawing.

Fig. 1 is the flow chart of orthogonal frequency division multiple access system distance measuring signal processing method of the present invention;

Fig. 2 is the composition frame chart of orthogonal frequency division multiple access system distance measuring signal treatment system of the present invention;

Fig. 3 is the composition frame chart of Candidate key detector among Fig. 2;

Fig. 4 is the composition frame chart of ranging code and timing offset detector among Fig. 2.

Embodiment

Below will be described in further detail orthogonal frequency division multiple access system distance measuring signal processing method of the present invention and system.

Orthogonal frequency division multiple access system distance measuring signal processing method of the present invention, be used for the distance measuring signal of wireless communication system with base station and user side is handled to draw actual ranging code and corresponding actual timing offset thereof in the current ranging slot, described orthogonal frequency division multiple access system is used for the up link of wireless communication system, and the corresponding range finding of described wireless communication system is provided with ranging slot, range channel, local Candidate key set R and the first and second default thresholding T ₁And T ₂In the present embodiment, the value of the described first and second default thresholdings is respectively 2dB and 4.6dB.

Referring to Fig. 1, described method is at first carried out step S0, and the received analog signal in base station is carried out analog-to-digital conversion to obtain digital signal, and the received time domain sequences in base station is y _n, its value under additive white Gaussian noise (AWGN) channel as shown in Equation (1):

$y_n=\frac{1}{N}\underset{k=-N/2}{\overset{N/2}{\mathrm{\&Sigma;}}}{X}_k{H}_{\mathrm{<figure-callout\; id="2"\; label="k\; e\; j"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">k</figure-callout>}}{e}^j{2\mathrm{\&pi;n}(k+\mathrm{\&epsiv;})/N}^{}+w_n---\left(1\right)$

Wherein, ε is normalized carrier wave frequency deviation, X _kBe the ranging code of BPSK modulation, H _kBe channel response, w _nBe the multiple Gaussian noise of time domain.

Then continue step S1, the digital signal of changing gained is stored in the data buffer.

Then continue step S2, from described data buffer, take out two fast fourier transform windows time domain sequences of current ranging slot and it is carried out fast fourier transform and obtains two frequency domain sequences, two range findings of cause symbols have kept the continuity of phase place, and the round-trip delay in system is no more than N _s+ N _gThe time can obtain a complete ranging code by two fast fourier transform windows.

Then continue step S3, from described two frequency domain sequences, isolate the pairing frequency domain sequence of range channel, the frequency domain sequence of being separated as shown in Equation (2),

$Y_k=X_k{H}_k\frac{\sin \mathrm{\&pi;\&epsiv;}}{N\sin (\mathrm{\&pi;\&epsiv;}/N)}{e}^{\mathrm{j\&pi;\&epsiv;}(N-1)/N}{e}^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\&Delta;nk}/N}+I_k+W_k---\left(2\right)$

Wherein Δ n is a timing offset, I _kBe the presence of intercell interference (ICI) that carrier wave frequency deviation and timing offset cause, I _kDetailed presentations as shown in Equation (3), w _kBe multiple noise item.

$I_k=\underset{\stackrel{m=-N/2}{m\&NotEqual;k}}{\overset{N/2}{\mathrm{\&Sigma;}}}{X}_m{H}_m\frac{\sin \mathrm{\&pi;\&epsiv;}}{N\sin [\mathrm{\&pi;}(m-k+\mathrm{\&epsiv;})/N]}{e}^{\mathrm{j\&pi;\&epsiv;}(N-1)/N}{e}^{-\mathrm{j\&pi;}(m-k)/N}{e}^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\&Delta;nk}/N}---\left(3\right)$

Then continue step S4, the isolated frequency domain sequence of institute carried out the frequency domain differential demodulation computing cross-correlation and result of calculation is added up obtaining the difference cross-correlation function, its process of carrying out the frequency domain differential demodulation computing cross-correlation as shown in Equation (4),

$Z_k{Z}_{k+1}^{*}=\left(Y_k{\hat{X}}_k\right){\left(Y_{k+1}{\hat{X}}_{k+1}\right)}^{*}=Y_k{Y}_{k+1}^{*}{\hat{X}}_k{\hat{X}}_{k+1}^{*}$

$=H_k{H}_{k+1}^{*}{\left[\frac{\sin \mathrm{\&pi;\&epsiv;}}{N\sin (\mathrm{\&pi;\&epsiv;}/N)}\right]}^2{e}^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\&Delta;n}/N}+\mathrm{noise}\_\mathrm{terms}---\left(4\right)$

Ignore sin ²Item and phase term, the noise item noise-terms in the following formula can approximate representation be:

$\mathrm{noise}\_\mathrm{terms}=H_k{I}_{k+1}^{*}+H_k{W}_{k+1}^{*}+I_k{H}_{k+1}^{*}+I_k{I}_{k+1}^{*}+I_k{W}_{k+1}^{*}+W_k{H}_{k+1}^{*}+W_k{I}_{k+1}^{*}+W_k{W}_{k+1}^{*}.$

Supposing does not have correlation between channel response and the noise, and specific energy is very little mutually with useful signal in the ICI interference in addition.Yet w _kAnd w _K+1Between may have certain correlation according to the specific noise environment, but this correlation can not be present in whole range channel.

With the stack of the frequency domain cross-correlation of all adjacent sub-carriers in the range channel, obtain the difference cross-correlation function again, its process as shown in Equation (5),

Wherein K is the quantity of adjacent sub-carrier in the range channel, and when range channel took 6 adjacent subchannels, the quantity of subcarrier was 144, and the quantity of adjacent sub-carrier is K=6 * 6 * 3=108.

Then continue step S5, the difference cross-correlation function is carried out modulo operation, the amplitude of promptly getting the difference cross-correlation function is as difference cross correlation measure flow function M, and its detailed process as shown in Equation (6).

$M=\left|P\right|=\frac{1}{K}{\left[\frac{\sin \mathrm{\&pi;\&epsiv;}}{N\sin (\mathrm{\&pi;\&epsiv;}/N)}\right]}^2\left|\underset{k}{\mathrm{\&Sigma;}}{H}_k{H}_{k+1}^{*}\right|---\left(6\right)$

Then continue step S6, calculate the first screening thresholding T according to the modulo operation result and the first default thresholding T1 _{F, 1}Or T _{F, 2}, remember at first during calculating that the difference cross correlation measure flow function that utilizes first fast fourier transform windows position time domain sequences to obtain is M _{1, r}, the difference cross correlation measure flow function that utilizes second fast fourier transform windows position time domain sequences to obtain is M _{2, r}, r ∈ R wherein, R are the local Candidate key set of system assignment, and then calculate by the method shown in the formula (7), promptly by the first default thresholding T ₁And the root-mean-square value of difference cross correlation measure flow function calculates the first screening thresholding T that is used to obtain Candidate key set C _{F, 1}Or T _{F, 2}

$T_{f,n}={10}^{T_f/10}\sqrt{\underset{r\&Element;R}{\mathrm{\&Sigma;}}{M}_{n,\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">r</figure-callout>}}^2},n=\mathrm{1,2}---\left(7\right)$

Then continue step S7, mould value among the modulo operation result is set at Candidate key greater than first ranging code that screens the difference cross-correlation function correspondence of thresholding, and it is stored to the Candidate key set memory that is used for storing the Candidate key set, the quantity that described Candidate key set comprises ranging code is greater than the quantity of actual ranging code, described obtaining by formula (8) of C of Candidate key set undertaken, if promptly the difference cross correlation measure flow function value of certain ranging code correspondence has surpassed thresholding T _{F, 1}Or T _{F, 2}, so the ranging code of described difference cross correlation measure flow function correspondence is put into Candidate key set C.

r→C,if(M _1,r>T _f,1)or(M _2,r>T _f,2) (8)

Then continue step S8, calculate according to the difference cross-correlation function and estimate timing offset,, calculate by method shown in the formula (9) and to estimate timing offset at this.

${\widehat{\mathrm{\&delta;}}}_r=\mathrm{round}\left\{\frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">N</figure-callout>}}{2\mathrm{\&pi;}}\arg \left[P_{1,r}\right]\right\},\mathrm{if}(M_{1,r}>{\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">M</figure-callout>}}_{2,r}),r\&Element;C$

(9)

${\widehat{\mathrm{\&delta;}}}_r=\mathrm{round}\left\{\frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">N</figure-callout>}}{2\mathrm{\&pi;}}\arg \left[{\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">P</figure-callout>}}_{2,r}\right]\right\}+N_g,\mathrm{if}(M_{2,r}>M_{1,r})$

Then continue step S9, detect Candidate key correspondence in the Candidate key set estimate whether timing offset phasing back takes place and when counter-rotating with its compensation to there not being inverted status.

Because ranging code transmits in range channel by pairwise orthogonal frequency division multiplexing symbol (OFDM symbol), two OFDM symbols have kept the continuity of phase place, suppose that round-trip delay can not surpass N _s+ N _g, just can guarantee to get a complete range finding symbol by the time domain sequences of getting two continuous fast fourier transform windows positions so, the present invention suppose round-trip delay [0, N/2+N _g] in the scope, suppose that a certain range finding user's round-trip delay is To, under desirable channel condition, the estimated value of the timing offset that is obtained by the time domain sequences of two fast fourier transform windows is as shown in Equation (10).

${\widehat{\mathrm{\&delta;}}}_1=\mathrm{TO}$

(10)

${\widehat{\mathrm{\&delta;}}}_2=\mathrm{TO}-N_g$

Use the phase place of frequency domain differential demodulation cross-correlation function to calculate in the above-mentioned formula (9) and estimated timing offset, algorithm use the phase place of correlation function of the greater correspondence of two difference cross correlation measure flow functions estimate timing offset estimation since the scope that the periodicity of phase place has caused estimating timing offset be restricted, according to (10) formula as can be known, the estimation range of timing offset is $\widehat{\mathrm{\&delta;}}\&Element;[-N/2,N/2+N_g],$ When user's timing offset approaches N/2+N _gThe time, the possible phasing back of frequency domain differential demodulation cross-correlation function under the non-ideal communication channel condition, thus cause timing estimation to lose efficacy, and the value that estimate this moment is at N/2+N _gNear-the N.

Narrated the reason that phasing back occurs above, the method that the detected phase counter-rotating will be described in detail in detail below and compensate, consider timing offset approaching-during N/2, phasing back causes estimating timing offset and produced+deviation of N, that is to say that the result who estimates is near N/2, when the timing offset of reality is near N/2, M _{1, r}Be impossible greater than M _{2, r}.Can be set at (N so judge the thresholding that this situation occurs _g+ N/2)/2.When timing offset near N _gDuring+N/2, timing offset that phasing back causes estimating produced-deviation of N, that is to say that the result that estimates is at-N/2+N _gNear, when the timing offset of reality at-N/2+N _gWhen neighbouring, M _{2, r}Be impossible greater than M _{1, r}, can be set at [N so judge the thresholding that this situation occurs _g+ (N/2+N _g)]/2=-N/4.Comprehensive above-mentioned thresholding to after calculate estimating timing offset by formula (9), can reverse and compensates by the method detected phase of formula (11).

${\widehat{\mathrm{\&delta;}}}_r^c={\widehat{\mathrm{\&delta;}}}_r-N,\mathrm{if\; if}(M_{1,r}>{\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">M</figure-callout>}}_{2,r})\mathrm{and}({\widehat{\mathrm{\&delta;}}}_r>(N_g+N/2)/2)$

(11)

${\widehat{\mathrm{\&delta;}}}_r^c={\widehat{\mathrm{\&delta;}}}_r+N,\mathrm{if}({\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">M</figure-callout>}}_{2,r}>M_{1,r})\mathrm{and}({\widehat{\mathrm{\&delta;}}}_r<-N/4)$

It should be noted that, by formula (11) though calculate estimate the problem that timing offset has solved phasing back, but under the situation of multi-user's range finding, since a plurality of users' distance measuring signal on identical range channel overlaying influence the phase place of correlation function, so above-mentioned estimated value can only be as the reference value of a timing offset.

Then continuing step S10, determine actual timing offset hunting zone according to estimating timing offset, is L in this hypothesis one-side search length, and L is a configurable parameter, gets L=64 in the present embodiment, then the estimated value that is calculated according to formula (11)

Determine hunting zone S, its detailed process as shown in Equation (12).

$S=\left\{n\right|{\widehat{\mathrm{\&delta;}}}_r^c-L\&le;n\&le;{\widehat{\mathrm{\&delta;}}}_r^c+L\},r\&Element;C---\left(12\right)$

Then continue step S11, according to difference cross correlation measure flow function isolated two frequency domain sequences among the step S3 are carried out phase compensation, its penalty coefficient is the e in the formula (13) ^{J2 π kn/N}Or

Then continue step S12, two frequency domain sequences and local Candidate key after the compensation are gathered carried out computing cross-correlation and result of calculation is added up obtaining cross-correlation function, and cross-correlation function is carried out modulo operation, its detailed process as shown in Equation (13).

$P_{t,r}\left(n\right)=\underset{k}{\mathrm{\&Sigma;}}{Y}_k{X}_k^{*}{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">e</figure-callout>}}^j,\mathrm{if}{M}_{1,r}>{\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">M</figure-callout>}}_{2,r}$

$P_{t,r}\left(n\right)=\underset{k}{\mathrm{\&Sigma;}}{Y}_k{X}_k^{*}{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">e</figure-callout>}}^j,\mathrm{if}{\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">M</figure-callout>}}_{2,r}>M_{1,r}---\left(13\right)$

M _t，r(n)＝|P _t，r(n)|

Then continue step S13, according to the cross-correlation function modulo operation result and the second default thresholding T ₂Calculate the second screening thresholding T _r, its detailed process is referring to shown in the formula (14).

$T_r={10}^{{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="A200710045820E00191.png"\; state="\{\{state\}\}">T</figure-callout>}}_2/10}\sqrt{\underset{n\&Element;S}{\mathrm{\&Sigma;}}{M}_{t,r}^2\left(n\right)},r\&Element;C---\left(14\right)$

Then continue step S14, according to the second screening thresholding T _rFilter out actual ranging code from Candidate key set C, its detailed process can obtain actual ranging code U as shown in Equation (15).

$r\&RightArrow;U,\mathrm{if}(\underset{n}{\max }\left[M_{t,r}\left(n\right)\right]>T_r)---\left(15\right)$

Then continue step S15, search out actual timing offset according to cross-correlation function modulo operation result and actual timing offset hunting zone, its detailed process as shown in Equation (16).

${\widehat{\mathrm{\&delta;}}}_{\mathrm{fine},r}=\arg \left\{\underset{n}{\max }\left[M_{t,r}\left(n\right)\right]\right\}---\left(16\right)$

Referring to Fig. 2, orthogonal frequency division multiple access system distance measuring signal treatment system 2 of the present invention, be used for the distance measuring signal of wireless communication system 1 with base station 10 and user side 11 is handled to draw actual ranging code and corresponding actual timing offset thereof in the current ranging slot, described base station 10 is connected by wireless network 12 with user side 11, and be provided with the base station transceiver module 100 that is used for receiving and transmitting signal in the described base station 10, user side 11 is provided with range finder module 110 that is used to find range and the user side transceiver module 111 that is used for receiving and transmitting signal, described OFDMA system is used for the up link of wireless communication system, and described wireless communication system 1 corresponding range finding is provided with ranging slot, range channel, the local Candidate key set and the first and second default thresholdings.When finding range, range finder module 110 is selected a ranging slot earlier at random in the ranging slot set of system assignment, and in the ranging code set that distributes, select a ranging code at random, by user side transceiver module 111 and via range channel described ranging code is transferred to base station 10 then, base station transceiver module 100 receives distance measuring signal, handles to draw actual ranging code and corresponding actual timing offset thereof in the current ranging slot by 2 pairs of distance measuring signals of orthogonal frequency division multiple access system distance measuring signal treatment system then.

Continuation is referring to Fig. 2, and orthogonal frequency division multiple access system distance measuring signal treatment system 2 of the present invention comprises analog to digital converter 20, data buffer 21, fast fourier transformer 22, demultiplexer 23, Candidate key detector 24, phasing back detection and compensator 25, ranging code and the timing offset detector 26 that is linked in sequence.Below the member of this orthogonal frequency division multiple access system distance measuring signal treatment system 2 is elaborated:

Analog to digital converter 20 is used for the received analog signal in base station is carried out analog-to-digital conversion to obtain digital signal, and its digital signal that obtains as shown in Equation (1).

Data buffer 21 is used for the digital signal of conversion gained is carried out buffer memory.

Fast fourier transformer 22 is used for taking out two fast fourier transform windows time domain sequences of current ranging slot and it being carried out fast fourier transform to obtain two frequency domain sequences from data buffer.

Demultiplexer 23 is used for isolating pairing two frequency domain sequences of range channel from two frequency domain sequences of conversion gained, and the isolated frequency domain sequence of institute as shown in Equation (2).

Candidate key detector 24 is used for isolated two frequency domain sequences of institute are carried out frequency domain differential demodulation computing cross-correlation, the computing of difference cross-correlation function and the first screening thresholding computing to obtain the Candidate key set and to estimate timing offset.

Referring to Fig. 3, described Candidate key detector 24 comprises two difference computing cross-correlation device 240a and 240b, two first accumulator 241a and 241b, two first modulo operation device 242a and 242b, difference cross correlation measure flow function memory 243, Candidate key set memory 244, Candidate key screening washer 245, estimate timing offset calculator 246 and estimate timing offset memory 247, wherein, two difference computing cross-correlation device 240a and 240b are used for isolated two frequency domain sequences of demultiplexer institute are carried out the difference computing cross-correlation with local ranging code set respectively, and its detailed calculated process as shown in Equation (4); Two first accumulator 241a and 241b are used for the result of difference computing cross-correlation is added up respectively, and its detailed calculated process as shown in Equation (5); Two first modulo operation device 242a and 242b are used for the accumulation result of two first accumulator 241a and 241b is carried out modulo operation respectively to obtain corresponding difference cross correlation measure flow function, and its detailed calculated process as shown in Equation (6); The delivery result that difference cross correlation measure flow function memory 243 is used to store two first modulo operation device 242a and 242b; Candidate key set memory 244 is used to store the Candidate key set; Candidate key screening washer 245 is used for calculating the first screening thresholding according to the difference cross correlation measure flow function and the first default thresholding, its detailed calculated process as shown in Equation (7), and difference cross correlation measure flow function is screened according to the first screening thresholding, and will be set at Candidate key greater than the pairing ranging code of difference cross correlation measure flow function of the first screening thresholding and it is stored in the Candidate key set memory 244, its detailed calculated process is as shown in Equation (8); Estimate timing offset calculator 246 and be used for accumulation result according to two first accumulators and calculate and estimate timing offset, its detailed calculated process as shown in Equation (9); Estimating timing offset memory 247 is used for storage and estimates timing offset.

Phasing back detection and compensator 25 be used for detecting the Candidate key set the Candidate key correspondence estimate whether timing offset phasing back takes place and when counter-rotating with its compensation to there not being inverted status, its detailed calculated process is as shown in Equation (11).

Ranging code and timing offset detector 26 are used for detecting ranging code and detecting actual timing offset from the Candidate key set by frequency domain computing cross-correlation, cross-correlation function computing and the second screening thresholding computing.

Referring to Fig. 4, described ranging code and timing offset detector 26 comprise hunting zone calculator 260, compensation branch road selector 261, two computing cross-correlation device 262a and 262b, two second accumulator 263a and 263b, two second modulo operation device 264a and 264b, cross correlation measure flow function memory 265, actual timing offset requestor 266, ranging code screening washer 267, actual ranging code memory 268 and actual timing offset memory 269; Wherein, hunting zone calculator 260 is used for calculating actual timing offset hunting zone according to estimating timing offset, and its detailed calculated process as shown in Equation (12); Compensation branch road selector 261 is used for carrying out the phase compensation branch road according to the difference cross correlation measure flow function that difference cross correlation measure flow function memory 246 is stored and chooses; Two computing cross-correlation device 262a and 262b be used for 23 isolated two frequency domain sequences of demultiplexer respectively with local ranging code set carrying out computing cross-correlation; Two second accumulator 263a and 263b are used for the result of computing cross-correlation is added up respectively to obtain cross-correlation function; Two second modulo operation device 264a and 264b are used for the cross-correlation function of the gained that adds up is carried out modulo operation to obtain corresponding cross correlation measure flow function, the detailed calculated process of two computing cross-correlation device 262a and 262b, two second accumulator 263a and 263b and two second modulo operation device 264a and 264b such as formula (13); Cross correlation measure flow function memory 265 is used to store the cross correlation measure flow function of two second modulo operation device 264a and 264b gained; Actual timing offset requestor 266 is used for inquiring maximum pairing actual timing offset in actual timing offset hunting zone of cross correlation measure flow function; Ranging code screening washer 267 is used for calculating the second screening thresholding according to the two cross correlation measure flow functions of two second modulo operation device 264a and 264b gained and the second default thresholding, and according to the second screening thresholding two cross correlation measure flow functions are screened to obtain actual ranging code, its detailed calculated process is shown in formula (14) and (15); Actual timing offset memory 268 and actual ranging code memory 269 are respectively applied for actual ranging code of storage and actual timing offset.

In sum, processing method of the present invention and system calculate the frequency domain differential demodulation cross-correlation function of adjacent sub-carrier in the range channel earlier, calculate the first screening thresholding then and filter out the Candidate key set in view of the above and estimate and estimate timing offset, then calculate the cross-correlation function and the second screening thresholding of ranging code frequency domain sequence and local ranging code, calculate actual timing offset at last and from the Candidate key set, filter out actual ranging code, so can guarantee the accuracy of finding range, and can guarantee lower computation complexity.

Claims (6)

1, a kind of orthogonal frequency division multiple access system distance measuring signal processing method, be used for the distance measuring signal of wireless communication system with base station and user side is handled to draw actual ranging code and corresponding actual timing offset thereof in the current ranging slot, this orthogonal frequency division multiple access system is used for the up link of wireless communication system, the corresponding range finding of this wireless communication system is provided with ranging slot, range channel, the local ranging code set and the first and second default thresholdings, this method may further comprise the steps: (1) carries out analog-to-digital conversion to obtain digital signal to the received analog signal in base station; (2) digital signal that will change gained is stored in the data buffer; (3) from this data buffer, take out two fast fourier transform windows time domain sequences of current ranging slot and it is carried out fast fourier transform and obtain two frequency domain sequences; (4) from this two frequency domain sequence, isolate the pairing frequency domain sequence of range channel; (5) the isolated frequency domain sequence of institute is carried out frequency domain differential demodulation computing cross-correlation and result of calculation added up to obtain the difference cross-correlation function; (6) the difference cross-correlation function is carried out modulo operation; It is characterized in that this method is further comprising the steps of: (7) calculate the first screening thresholding according to the modulo operation result and the first default thresholding; (8) mould value among the modulo operation result is set at Candidate key greater than first ranging code that screens the difference cross-correlation function correspondence of thresholding, and it is stored to the Candidate key set memory that is used for storing the Candidate key set; (9) calculate according to the difference cross-correlation function and estimate timing offset; (10) determine actual timing offset hunting zone according to estimating timing offset; (11) isolated two frequency domain sequences in the step (4) are added up obtaining cross-correlation function with local ranging code set carrying out computing cross-correlation and with result of calculation respectively, and cross-correlation function is carried out modulo operation; (12) calculate the second screening thresholding according to the cross-correlation function modulo operation result and the second default thresholding; (13) from the Candidate key set, filter out actual ranging code according to the second screening thresholding; (14) search out actual timing offset according to cross-correlation function modulo operation result and actual timing offset hunting zone.

2, orthogonal frequency division multiple access system distance measuring signal processing method as claimed in claim 1, it is characterized in that, this method between step (9) and step (10), also comprise the Candidate key correspondence that detects in the Candidate key set estimate whether timing offset phasing back takes place and when counter-rotating with its compensation to there not being inverted status.

3, a kind of orthogonal frequency division multiple access system distance measuring signal treatment system, be used for the distance measuring signal of wireless communication system with base station and user side is handled to draw actual ranging code and corresponding actual timing offset thereof in the current ranging slot, this orthogonal frequency division multiple access system is used for the up link of wireless communication system, the corresponding range finding of this wireless communication system is provided with ranging slot, range channel, the local ranging code set and the first and second default thresholdings, this distance measuring signal treatment system comprises and is linked in sequence and is used for successively the received analog signal in base station is carried out analog-to-digital conversion to obtain the analog to digital converter of digital signal, be used for the digital signal of conversion gained is carried out the data in buffer buffer, be used for taking out two fast fourier transform windows time domain sequences of current ranging slot and it being carried out fast fourier transform with fast fourier transformer that obtains two frequency domain sequences and the demultiplexer that is used for isolating from two frequency domain sequences of conversion gained pairing two frequency domain sequences of range channel from data buffer, it is characterized in that, this distance measuring signal treatment system also comprises: be connected behind the demultiplexer and be respectively applied for isolated two frequency domain sequences of institute are carried out the frequency domain differential demodulation computing cross-correlation, the Candidate key detector of timing offset is gathered and estimated to the computing of difference cross-correlation function and the first screening thresholding computing to obtain Candidate key, be used for by the frequency domain computing cross-correlation, the cross-correlation function computing and the second screening thresholding computing and from Candidate key set, detect ranging code and detect the ranging code and the timing offset detector of actual timing offset, wherein, this first screening thresholding is used for screening and draws the Candidate key set, this first screening thresholding computing is carried out according to the difference cross-correlation function and the first default thresholding, this second screening thresholding is used for drawing actual ranging code from Candidate key set screening, and this second screening thresholding computing is carried out according to the cross-correlation function and the second default thresholding.

4, orthogonal frequency division multiple access system distance measuring signal treatment system as claimed in claim 3, it is characterized in that, this orthogonal frequency division multiple access system distance measuring signal treatment system also comprises and being arranged between Candidate key detector and ranging code and timing offset detector, be used for detecting the Candidate key set the Candidate key correspondence estimate whether timing offset phasing back takes place and when counter-rotating with its compensation to the phasing back detection and the compensator that do not have inverted status.

5, orthogonal frequency division multiple access system distance measuring signal treatment system as claimed in claim 3, it is characterized in that, this Candidate key detector comprise be used for demultiplexer isolated two frequency domain sequences respectively with two difference computing cross-correlation devices of local ranging code set carrying out difference computing cross-correlation, be used for two first accumulators that the result with the difference computing cross-correlation adds up respectively, be used for the accumulation result of two first accumulators is carried out modulo operation respectively to obtain two first modulo operation devices of corresponding difference cross correlation measure flow function, be used to store the difference cross correlation measure flow function memory of two first modulo operation device operation results, be used to store the Candidate key set memory of Candidate key set, be used for calculating the first screening thresholding according to the difference cross correlation measure flow function and the first default thresholding, and according to the first screening thresholding difference cross correlation measure flow function is screened, and will be set at Candidate key greater than the pairing ranging code of difference cross correlation measure flow function of the first screening thresholding and it is stored to the Candidate key screening washer of Candidate key set memory, be used for accumulation result according to two first accumulators calculate estimate timing offset estimate the timing offset calculator and be used to store estimate timing offset estimate the timing offset memory.

6, orthogonal frequency division multiple access system distance measuring signal treatment system as claimed in claim 5, it is characterized in that, this ranging code and timing offset detector comprise and being used for according to estimating the hunting zone calculator that timing offset calculates actual timing offset hunting zone, be used for carrying out the compensation branch road selector that the phase compensation branch road is chosen according to the correlation function that difference cross correlation measure flow function memory is stored, be used for demultiplexer isolated two frequency domain sequences respectively with two computing cross-correlation devices of local ranging code set carrying out computing cross-correlation, be used for the result of computing cross-correlation is added up respectively to obtain two second accumulators of correlation function, the correlation function of gained of being used for adding up carries out modulo operation to obtain two second modulo operation devices of corresponding cross correlation measure flow function, be used to store the cross correlation measure flow function memory of the cross correlation measure flow function of two second modulo operation device gained, be used for inquiring the actual timing offset requestor of maximum pairing actual timing offset in actual timing offset hunting zone of cross correlation measure flow function, be used for calculating the second screening thresholding, and two cross correlation measure flow functions screened with ranging code screening washer that obtains actual ranging code and actual timing offset memory and the actual ranging code memory that is respectively applied for actual timing offset of storage and actual ranging code according to the second screening thresholding according to the two cross correlation measure flow functions and the second default thresholding.

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