CN101193398A - An uplink distance measuring method, device and base station - Google Patents

Abstract

The invention discloses an uplink ranging method, a device and a base station. Based on an orthogonal frequency division multiple access (OFDMA) system, the invention comprises the following steps: the base station selects a group of candidate ranging code sequences from the reference ranging sequences and calculates the correlation peak when the non-matching happens according to the time domain peak of a related detectable quantity; the double peaks are detected according to the candidate ranging code sequence and whether the distance between the double peaks is larger than a preset threshold is judged; if the distance between double peaks is larger than the preset threshold, then the ranging code is discarded, otherwise, a frequency offset, a received power and a timing offset are acquired, a decision threshold is calculated and the active ranging code is acquired according to the decision threshold. In the invention, a group of candidate ranging code sequences are selected according to the decreasing sequence of the time domain peak of the related detectable quantity and then the double-peak detection is utilized to ensure the legal availability of the candidate ranging code sequences, and finally the screened ranging codes are utilized to estimate the frequency offset, received power and timing offset, thus enhancing the precision of the detection.

Description

A kind of uplink distance measuring method, device and a kind of base station

Technical field

The present invention relates to OFDM (OFDMA, Orthogonal Frequency DivisionMultiple Access) technology, refer to a kind of uplink distance measuring method, device and a kind of base station especially based on the OFDMA system.

Background technology

The OFDMA technology is a kind of multiuser multiplexing and access technology based on OFDM (OFDM).For the OFDMA system, all subcarriers are divided into a plurality of subchannels, and each subchannel is made up of the experimental process carrier wave, and system can come Resources allocation from subchannel and two dimensions of time slot, so the granularity of resource allocation is less, and flexibility is higher relatively.

Because each mobile subscriber is in the randomness of subdistrict position, the time of each up subscriber signal that the base station receives will be subjected to the influence of trip path time delay (Round Trip Delay), cause each mobile subscriber's OFDMA symbol can't align (misalignment); And because the influence of large scale decline, the path loss that each mobile subscriber's upward signal is subjected to also has nothing in common with each other; In addition, also exist certain deviation between each mobile subscriber's carrier frequency and the base station.If the base station does not overcome the influence of above-mentioned factor, can't recover each mobile subscriber's upstream data, therefore, need before inserting up link, each mobile subscriber realize that each mobile subscriber's uplink distance measuring is handled, to guarantee the uplink synchronisation of OFDMA system.

Usually, the uplink distance measuring processing procedure is a kind of process that is used to adjust mobile subscriber's carrier wave frequency deviation, timing offset and received power in the OFDMA system, and this process is the part of uplink synchronisation.In the uplink distance measuring processing procedure, mobile subscriber (MSS) is also referred to as ranging code (Ranging Codes) to a kind of frequency domain CDMA sign indicating number sequence that base station (BS) sends, and the system parameters that is used for the uplink distance measuring process is estimated and adjustment.The ranging code that each mobile subscriber sends superposes in the base station, also has Frame transmitting in up link simultaneously, and therefore, what the base station received is the composite signal of ranging code and Frame.Because ranging code is a frequency domain CDMA sign indicating number, has good auto-correlation and their cross correlation on time domain, therefore, can utilizes time domain to be correlated with and detect the ranging code signal that arrives the base station.

Pertinent literature has proposed the uplink distance measuring method of a kind of OFDMA system, and this method can solve the timing offset in the uplink distance measuring process and the estimation problem of received power, briefly introduces the method for realization below.

Suppose that there is N in the OFDMA system _dIndividual subcarrier, circulating prefix-length are N _gBecause the time domain sequences of initial ranging sign indicating number comprises two symbols, wherein first symbol adds prefix, second symbol adds suffix, so these two OFDMA symbols have the continuous phase characteristic, supposes that the time domain distance measuring signal of k range finding user transmission is shown in the formula (1):

x _k＝[x _k(0)，…，x _k(2N _d+2N _g-1)] ^T (1)

Average power is: $E\left[{\left|x_k\left(n\right)\right|}^2\right]={\mathrm{\Γ}}_k^2$ (2)

Suppose that this k range finding user selected m ranging code, and hypothesis c _m(i) be i sub-carrier value of m ranging code.

It is N that the watch window width is set _d+ N _g+ d _Max, d wherein _MaxMaximum delay for transmission channel sets in advance according to actual conditions.This watch window comprises a complete OFDMA symbol at least.

The maximum multipath time delay of supposing channel is L, and then the time-domain signal of Jie Shouing can be write as matrix form as shown in Equation (3):

$Y=\mathrm{XH}+\tilde{W}$ (3)

Wherein, Y=[y (0) ..., y (N _d+ N _g+ d _Max-1)] ^T

Known channel impulse H=[h ₁..., h _K] ^T, wherein, h _k=[h _k(0) ..., h _k(L-1)] ^T

X＝[X ₁，…，X _K]，

Wherein, K user's distance measuring signal X _k=[x ' k (d _k) ..., x ' _k(d _k+ L-1)],

$x_k^{\′}\left(d_k\right)={[0_{d_k\×1},x_k\left(0\right),...,x_k(N_d+N_g+d_{\max }-d_k-1)]}^T;$

For comprising the composite signal of uplink synchronous user data and noise, K is the range finding number of users.

The hypothetical reference distance measuring signal is $S_m\left(d\right)=\frac{1}{{\mathrm{\Γ}}_m}{[0_{d\×1},x_m\left(0\right),...,x_m(N_d+N_g-1),...,0_{(d_{\max }-d)\×1}]}^T$ , wherein, 0＜d＜d _Max, m ∈ 1 ..., N _c, N _cBe ranging code collection size, then time domain coherent detection amount is as shown in Equation (4):

${\hat{Y}}_m\left(d\right)=S_m^H\left(d\right)Y=\underset{k=1}{\overset{K}{\mathrm{\Σ}}}{S}_m^H\left(d\right)X_k{h}_k+S_m^H\left(d\right)\tilde{W}$

$=\left\{\begin{array}{c}{S}_m^H{X}_m{h}_m+\underset{k=1,k\≠m}{\overset{K}{\mathrm{\Σ}}}{S}_m^H\left(d\right)X_k{h}_k+S_m^H\left(d\right)\tilde{W},m\∈\left\{C_t\right\}\\ \underset{k=1}{\overset{K}{\mathrm{\Σ}}}{S}_m^H\left(d\right)X_k{h}_k+S_m^H\left(d\right)\tilde{W},\mathrm{others}\end{array}\right.$ (4)

{ C wherein _tBe the ranging code collection of K range finding user current transmission, therefore, with it Dui Ying timing estimation value be timing offset as shown in Equation (5):

${\hat{d}}_m=\arg \underset{d}{\max }\left|{\hat{Y}}_m\left(d\right)\right|,d\∈\{\mathrm{0,1},...,d_{\max }\}$ (5)

Formula (5) expression from

In find out corresponding d _MaxEstimated value.

Time domain coherent detection amount peak value sequence at timing position can be expressed as:

$\left|{\hat{Y}}_m\left({\hat{d}}_m\right)\right|\≈\left\{\begin{array}{c}|S_m+I_m+N_m|=\frac{\left|S_m\right|}{2}\sqrt{2E+2\sqrt{E^2-F^2}},m\∈\left\{C_t\right\}\\ |I_m+N_m|,\mathrm{others}\end{array}\right.$ (6)

Wherein, $E=1+\frac{1}{2}{\left(\frac{|I_m+N_m|}{\left|S_m\right|}\right)}^2,$ $F=\frac{|I_m+N_m|}{\left|S_m\right|},$ S _mThe expression signal, I _mExpression is disturbed, N _mThe expression noise.

| I _m+ N _m| the correlation peak during for non-coupling can be approximately shown in the formula (7):

$|I_m+N_m|\≈|I+N|=\frac{\underset{d=0}{\overset{d_{\max }}{\mathrm{\Σ}}}\left|{\hat{Y}}_i\left(d\right)\right|}{d_{\max }+1}$ (7)

Wherein, $i=\arg \underset{m}{\min }\left|{\hat{Y}}_m\left({\hat{d}}_m\right)\right|,$ M ∈ 1 ..., N _c, the expression ranging code

A sign indicating number of middle i value minimum.

$\left|S_m\right|\&ap;|{\hat{Y}}_m\left({\hat{d}}_m\right)-<I+N>|$ (8)

Wherein,＜I+N〉expression disturb in the mean estimates of noise, its value can approximate shown in the formula (9):

$<I+N>\&ap;\frac{\underset{d=0}{\overset{d_{\max }}{\mathrm{\&Sigma;}}}{\hat{Y}}_i\left(d\right)}{d_{\max }+1}$ (9)

Thereby the power estimated value that draws the ranging code signal is as shown in Equation (10):

${\hat{P}}_m\&ap;\frac{{\left|S_m\right|}^2}{r\left(0\right)(N_d+N_g)},$ m∈{1，…，N _c}(10)

Wherein, $r\left(0\right)=S_m^H\left({\hat{d}}_m\right)x_m^{\&prime;}\left({\hat{d}}_m\right),$ For what estimate in advance.

So decision threshold can be set to shown in the formula (11):

$\mathrm{\&eta;}=|I_m+N_m|+\frac{M}{2}$ (11)

Wherein, $M=\frac{\left|S_m\right|}{2}\sqrt{2E+2\sqrt{E^2-F^2}}-|I_m+N_m|.$

By above-mentioned derivation, prior art uplink distance measuring process is:

1) base station utilizes formula (4) and formula (5) to calculate time domain coherent detection amount and timing offset.

2) base station obtains by comparison formula (6) With decision threshold η size, adjudicate each ranging code and whether enliven, if

Greater than η, represent that this ranging code is active

3) base station utilizes formula (10) to estimate the received power of the ranging code that each is active.

In sum, existing uplink distance measuring method only provides principle, does not provide concrete implementation, and, only provided the algorithm for estimating of timing offset and received power in the document, do not provide the algorithm for estimating of carrier wave frequency deviation.

According to the calculating principle that provides, because in the formula (7) | I _m+ N _m| be made as the time domain average of the corresponding ranging code of minimum peak, caused the error of calculation bigger.In like manner,＜I+N〉calculating also have similar problem, caused decision threshold η and the actual value error set bigger.In addition, the received power of ranging code is calculated in time domain because r (0) and | S _m| be difficult to accurate estimation, reduced the estimated accuracy of received power.

Outside, existing algorithm is only got rid of pseudo-ranging code by single decision threshold η, and false alarm probability is higher, particularly when ranging slot does not contain ranging code, the easier false-alarm that causes.

Summary of the invention

In view of this, the embodiment of the invention provides a kind of uplink distance measuring method, comprises the estimation of timing offset, carrier wave frequency deviation and received power, guarantees the precision of estimating.

The embodiment of the invention provides a kind of uplink distance measuring device, can guarantee the precision that uplink distance measuring is estimated.

The embodiment of the invention provides a kind of base station, can guarantee the precision that uplink distance measuring is estimated.

For achieving the above object, embodiment of the invention technical scheme specifically is achieved in that

A kind of uplink distance measuring method sets in advance with reference to the range finding sequence, and this method comprises:

The base station is according to the peak value of coherent detection amount, from reference to one group of candidate's ranging code of range finding sequence selection sequence, and the correlation peak when calculating non-coupling;

According to candidate's ranging code Sequence Detection bimodal, if the spacing of bimodal then abandons ranging code greater than predetermined threshold value; Otherwise, obtain frequency departure, received power and timing offset, calculate decision threshold and obtain active ranging code according to this decision threshold.

A kind of uplink distance measuring device, this device is arranged in the base station, comprising: memory module, selection module, judge module, computing module, wherein,

Memory module is used to store the reference range finding sequence that sets in advance;

Select module, be used for the peak value according to the coherent detection amount, the reference range finding sequence selection one group of candidate's ranging code sequence from memory module also sends to judge module; Correlation peak when calculating non-the coupling;

Judge module is used to receive from candidate's ranging code sequence of selecting module, detects bimodal, during greater than predetermined threshold value, abandons ranging code in the spacing of bimodal; When the spacing of bimodal is not more than predetermined threshold value, the notice computing module;

Computing module is used to receive the notice from judge module, and calculated rate deviation, received power and timing offset calculate decision threshold and obtain active ranging code according to this decision threshold.

A kind of base station, this base station comprise above-mentioned uplink distance measuring device.

As seen from the above technical solution, this time domain peak value order from big to small that the embodiment of the invention provides according to the coherent detection amount, select one group of candidate's ranging code sequence, and then utilize bimodal to detect, guarantee the legal availability of candidate's ranging code sequence, last, utilize garbled ranging code, frequency departure, received power and timing offset are estimated, improved the precision that detects.

Further, the method that the embodiment of the invention adopts time-frequency to combine, under the bigger situation of ranging code collection, the amount of calculation that the time domain coupling is relevant is big, having reduced the computation complexity of location algorithm, is to determine the Candidate key collection at frequency domain and adopt the method for time-frequency combination, and then is transformed into the coherent detection of time domain coupling, greatly reduced the size of time domain ranging code search set, the effect that time domain detects has been to simplify processing policy regularly.

Description of drawings

Fig. 1 is the flow chart of the method for the embodiment of the invention;

Fig. 2 is the schematic diagram of ranging code;

Fig. 3 is the schematic representation of apparatus of the embodiment of the invention.

Embodiment

The embodiment of the invention mainly comprises: the base station is according to the time domain peak value order from big to small of coherent detection amount, and traversal is with reference to one group of candidate's ranging code of range finding sequence selection sequence, and the correlation peak when calculating non-coupling; According to candidate's ranging code Sequence Detection bimodal, whether the spacing of judging bimodal greater than predetermined threshold value, if greater than, then abandon ranging code, process ends; Otherwise, obtain frequency departure, received power and timing offset, calculate decision threshold and obtain active ranging code according to this decision threshold.

For the purpose, technical scheme and the advantage that make the embodiment of the invention is clearer, below with reference to the accompanying drawing preferred embodiment that develops simultaneously, embodiments of the invention are further described.

Fig. 1 is the flow chart of the method for the embodiment of the invention, and as shown in Figure 1, the method for the embodiment of the invention comprises:

Step 100: the base station is according to the time domain peak value order from big to small of coherent detection amount, and reference the range finding sequence that traversal sets in advance is selected one group of candidate's ranging code sequence, and the correlation peak when calculating non-the coupling.

In this step, the time domain peak value of coherent detection amount obtains by existing method, as shown in Equation (6), and from N _cGroup is with reference to selecting one group of sequence { C in the ranging code sequence _Max, the time domain peak value absolute value of its coherent detection amount

Bigger than other sequence, and $C_t\&Subset;C_{\max }$ 。Need to prove sequence { C _MaxNumber set in advance, its size is closely related with cell load, promptly generally how many possible ranging codes each access slot should have insert from probability simultaneously.This value can set in advance, and also can adopt other to determine as methods such as cluster analyses.

Like this, can remove sequence { C by statistics _MaxOutside other sequence calculate | I _m+ N _m| value, promptly calculate in other sequence except that described candidate's ranging code, the time domain coherent detection amount peak value sum of corresponding range finding user's ranging code is utilized this and the number of value divided by non-candidate ranging code again, this quotient is as the correlation peak in non-when coupling, as shown in Equation (12):

$|I_m+N_m|\&ap;\frac{\underset{m=1,m\&NotElement;C_{\max }}{\overset{N_c}{\mathrm{\&Sigma;}}}\left|{\hat{Y}}_m\left({\hat{d}}_m\right)\right|}{N_c-\left|\right|C_{\max }\left|\right|}$ (12)

Wherein, || C _Max|| be { C _MaxThe element number that comprises, N _cBe ranging code collection size.

Find out the correlation peak during non-the coupling easily | I _m+ N _m| the average of each peak value is calculated during by non-coupling, and relative error is less.

Step 101: according to candidate's ranging code Sequence Detection bimodal, whether the spacing of judging bimodal greater than predetermined threshold value, if greater than, enter step 104; Otherwise, enter step 102.

In this step, be that the pseudo-ranging code that possible exist is picked out, guarantee the availability of ranging code in candidate's ranging code sequence.Here, bimodal is that threshold value is spacing and OFDMA symbol lengths N of bimodal according to the time domain peak value of the coherent detection amount of the adjacent continuous symbol of formula (6) calculating _dDifference, set in advance after can determining by emulation, generally can be taken as 1/8N _d～1/16N _d

If the spacing of the bimodal of certain candidate's ranging code correspondence, judges then that this candidate's ranging code is pseudo-ranging code greater than predetermined threshold value; Otherwise, judge that this ranging code is available ranging code.

Step 102: obtain frequency departure, received power and timing offset.

The power of supposing an effective OFDMA symbol of transmitting terminal candidate ranging code is:

${\left|{\tilde{Y}}_m\right|}^2={\left[\begin{array}{c}{x}_m\left(N_g\right)\\ x_m(N_g+1)\\ ...\\ x_m(N_d+N_g-1)\end{array}\right]}^T\&CenterDot;\left[\begin{array}{c}{x}_m\left(N_g\right)\\ x_m(N_g+1)\\ ...\\ x_m(N_d+N_g-1)\end{array}\right],$ Then the average power of candidate's ranging code sequence correspondence is

And ${\left|{\tilde{Y}}_m\right|}^2=N_d\&CenterDot;{\tilde{P}}_m.$

The base station calculate by Paasche Wa Er theorem on the subcarrier of range finding subchannel correspondence received power as shown in Equation (13):

$P_m=\frac{1}{N_d}\underset{n=N_g}{\overset{N_d+N_g-1}{\mathrm{\&Sigma;}}}{\left|y_m\left(n\right)\right|}^2=\frac{1}{A}\underset{i\&Element;A}{\mathrm{\&Sigma;}}{\left|{\tilde{c}}_m\left(i\right)\right|}^2$ (13)

Wherein, A is the subcarrier of range finding subchannel correspondence, y _m(n) be time domain coherent detection amount, Be frequency domain coherent detection amount.Need to prove that the derivation by Paasche Wa Er theorem belongs to general knowledge as well known to those skilled in the art, repeats no more here.From formula (13) as seen, the embodiment of the invention has been eliminated the interference of uplink transmission data frame to greatest extent by the received power on the Paasche Wa Er theorem calculating range finding subchannel, has improved the precision of estimating.

In this step, promptly according to existing formula (5) ${\hat{d}}_m=\arg \underset{d}{\max }\left|{\hat{Y}}_m\left(d\right)\right|,$ D ∈ 0,1 ..., d _Max, calculate corresponding sequence { C _MaxThe timing estimation value be timing offset, promptly from the coherent detection amount of described candidate's ranging code sequence correspondence

In find out the maximum delay d of corresponding transmission channel _MaxEstimated value, this estimated value is as timing offset.From as can be seen,,, guaranteed the accuracy of estimating here to the estimation that timing offset carries out owing to be corresponding candidate's ranging code sequence through selecting.

Further,, need impose a condition in order to get rid of the too small ranging code of pseudo-ranging code and power, as shown in Equation (14):

$\left|{\tilde{Y}}_{m,\mathrm{thresh}}\right|\&GreaterEqual;|I_m+N_m|\&CenterDot;\mathrm{\&alpha;}$ (14)

Coefficient of reliability α＞1 wherein is for default coefficient of reliability, such as α=1.5.

For the legal ranging code that satisfies condition shown in the formula (14), the front has been calculated its timing offset and received power, the embodiment of the invention to the method for estimation of the carrier wave frequency deviation of ranging code is: do calculus of differences by adjacent two symbols of ranging code on the range finding subchannel and calculate, be specially:

Suppose the subcarrier of A (k) for the range finding subchannel, k=0 wherein, 1 ..., N _r-1, N _rSub-carrier number for the range finding subchannel; Z _{I, A (k)}It is the frequency domain data on the individual subchannel of i symbol A (k).Because the initial ranging signal is connected by two identical useful symbols and forms, therefore, the calculated rate deviation is: respectively the frequency domain data on the adjacent sub-channel in i the symbol is done correlation computations, calculate again each correlation computations value and angle, calculate the merchant of this angle and constant 2 π at last, thereby obtain frequency departure, as shown in Equation (15):

$\widehat{\mathrm{\&Delta;f}}=\frac{\mathrm{angle}(\underset{k=0}{\overset{N_r-1}{\mathrm{\&Sigma;}}}{Z}_{i,A\left(k\right)}^{*}\&CenterDot;Z_{i+1,A\left(k\right)})}{2\mathrm{\&pi;}}$ (15)

Wherein, the estimation range of frequency deviation value is [0.5,0.5], and the frequency deviation surplus of ranging code can not exceed this scope.

Step 103: calculate decision threshold and obtain active ranging code, process ends according to this decision threshold.

Correlation peak in the time of can mating according to formula (13) is as shown in Equation (16):

$|S_m+I_m+N_m|=\left|{\tilde{Y}}_{m,\mathrm{thresh}}\right|=\left|{\tilde{Y}}_m\right|\&CenterDot;\sqrt{\frac{P_m}{{\tilde{P}}_m}}$ (16)

Wherein,

Be the power attenuation factor, the ratio of expression received power and transmitting power, the size of the channel fading of reflection distance measuring signal experience.

Therefore, whether mate corresponding peak value difference as shown in Equation (17):

$M=\left|{\tilde{Y}}_{m,\mathrm{thresh}}\right|-|I_m+N_m|\&CenterDot;\mathrm{\&beta;}$ (17)

So decision threshold can be set to shown in the formula (18):

η＝|I _m+N _m|·β+(M/2)·γ(18)

Consider the influence of channel, the more satisfactory value of correlation peak slightly descends under the fade condition, therefore, default coefficient correlation γ＜1, such as γ=0.8, and default modifying factor β considers that average can be provided with β=1.1 to the modifying factor of peak value under the mismatched condition.

The coherent detection peak value of ranging code correspondence is active ranging code greater than the decision threshold shown in the formula (18), is legal available, otherwise, be pseudo-ranging code.

Correlation peak during coupling | S _m+ I _m+ N _m| directly proofread and correct, not only reduced computation complexity but also improved computational accuracy by the power attenuation factor of estimating; Decision threshold η is dynamically determined with two parameters of peak value difference of whether mating correspondence by the correlation peak of above-mentioned timing, owing to introduced modifying factor β, the more realistic value of the threshold value that calculates simultaneously.

Step 104: abandon ranging code.

From flow process shown in Figure 1, embodiment of the invention method is utilized decision threshold η and bimodal thresholding, has picked out pseudo-ranging code effectively, has reduced the false alarm probability in detecting significantly.

Further, before step 101, this method also comprises: at candidate's ranging code sequence { C _MaxIn, add up this sequence { C _MaxIn the number of candidate's ranging code on each ranging slot, if the number of candidate's ranging code is greater than 1 in the ranging slot, then have several ranging codes and a plurality of different ranging code signals are promptly arranged in identical ranging slot in collision on this ranging slot, also may comprise several pseudo-ranging codes, perhaps be pseudo-ranging code all.Because have this possibility, the value of the ranging code capability correction on this ranging slot need be provided.Here, system's a plurality of ranging slot that have been the ranging code sequence allocation in advance launch in any one that distance measuring signal can be from the ranging slot of these distribution like this, so receiving terminal need be added up in candidate's ranging code sequence to belong to which ranging slot respectively.The method of determining sees exactly which access slot the detected moment belongs to and get final product.

If collision process truly takes place, because correlation peak and power attenuation are proportional, therefore can calculate the capability correction value of each ranging code according to the correlation peak of each the candidate's ranging code on this ranging slot, this capability correction value is the total signal power according to the size distribution of correlation peak;

If having certain ranging code on this ranging slot is pseudo-ranging code, then its correlation peak is very little with respect to true ranging code, causing its capability correction value is the very big negative value of absolute value, the processing of back will be got rid of this pseudo-ranging code situation, abandon promptly that the capability correction value is the pseudo-ranging code of the very big negative value of absolute value on this ranging slot;

If the ranging code on this ranging slot is pseudo-ranging code, the i.e. transmission of no ranging code on this time slot, the absolute value of the capability correction value that calculate this moment is not very big, and the processing of back will be got rid of, and promptly abandon the little pseudo-ranging code of absolute value of capability correction value.

In the embodiment of the invention method shown in Figure 1, timing offset detects and all is based on the time domain related algorithm, handle advantage like this with explicit physical meaning, for the little situation of ranging code collection is more effective, but for the bigger situation of ranging code collection, in order further to reduce amount of calculation, the embodiment of the invention also proposes a kind of ranging code search and detection algorithm of time-frequency combination, thereby reduce computation complexity effectively, further improve and detect performance.

Because the initial ranging sign indicating number has the characteristic of continuous phase, therefore the FFT window (FFT W) that drops in the initial ranging sign indicating number scope can obtain complete ranging code frequency domain information, unique influential be the phase shift that timing offset causes.Fig. 2 is the distance measuring signal schematic diagram, as shown in Figure 2, supposes that having two ascending time slots is ascending time slot 21 and ascending time slot 22, and each ascending time slot accounts for 3 symbols, and these up zones can be divided into 3 initial ranging time slots, and each ranging slot accounts for 2 symbols.If the initial ranging coded signal of different delay is superimposed, and generate and signal with upstream data. signals, choose time-domain signal by the effective FFT window so, convert it to frequency domain, just can extract the frequency domain information relevant, and avoid of the interference of useful data signal the ranging code signal with ranging code.

In order to realize the conversion of time domain to frequency domain, need handle each FFT window, guarantee that the complete information of each ranging code can be intercepted at least by a FFT window complete.

Suppose that x (n) is the time domain samples of ranging code, wherein, n=0,1 ..., N _d-1, x _D(n)=x (n-n ₀) be the cyclic shift value of ranging code time domain sample value, the delay unit is n ₀Individual sampled point (sample).The time domain samples that the FFT window is truncated to also is x _D(n).

In order to estimate n ₀, calculate tolerance as shown in Equation (19):

$M\left(n\right)=\left|\mathrm{IFFT}\left(X_D\left(k\right)X_m^{*}\left(k\right)\right)\right|$ (19)

Wherein, $X_D\left(k\right)=\mathrm{FFT}\left(x_D\left(n\right)\right)=X\left(k\right)e^{-j2\mathrm{\&pi;k}{n}_0/N_d},$ X _m(k) be frequency domain sample value with reference to ranging code, $X\left(k\right)=\mathrm{FFT}\left(x\left(n\right)\right)=\underset{n=0}{\overset{N_d-1}{\mathrm{\&Sigma;}}}x\left(n\right)e^{-j2\mathrm{\&pi;kn}/N_d},$ FFT () operator representation Fourier transform, IFFT () operator representation inverse Fourier transform.

Suppose $x_{\mathrm{corr}}\left(n\right)=\mathrm{IFFT}\left(X\left(k\right)X_m^{*}\left(k\right)\right),$ As X (k) and X _mWhen (k) mating, there is relation as shown in Equation (20):

$\arg \underset{n}{\max }\left|x_{\mathrm{corr}}\left(n\right)\right|=0$ (20)

That is to say X (k) and X _m(k) identically can get maximum, and maximum reaches in 0 delay place.

With formula (20) substitution formula (19), can get formula (21):

$M\left(n\right)=\left|\mathrm{IFFT}\left(X_D\left(k\right)X_m^{*}\left(k\right)\right)\right|.$

$=\left|\mathrm{IFFT}\left(X\left(k\right)X_m^{*}\left(k\right)e^{-j2\mathrm{\&pi;k}{n}_0/N_d}\right)\right|.$

$=\left|x_{\mathrm{corr}}(n-n_0)\right|.$ (21)

Therefore, can get formula (22):

${\hat{n}}_0=\arg \underset{n}{\max }M\left(n\right)$ (22)

The time domain length of delay that utilizes formula (22) to estimate , the FFT window that can determine distance measuring signal is detected time domain length of delay

Deduct a default protection at interval, still, because there is kN in the real original position of FFT window and distance measuring signal _dDeviation, and the randomness that k value and distance measuring signal arrive is relevant.In addition, because the possibility that the ranging code that adjacent FFT window calculation obtains is identical is very big, make frequency domain estimate that the original position of ranging code becomes complicated, therefore, the embodiment of the invention is correlated with in conjunction with time domain and is finished the location of ranging code, the effect of frequency domain detection has been greatly to reduce the size of time domain ranging code search set, and the effect that time domain detects has been to simplify processing policy regularly.

Select the method for candidate's ranging code sequence to be:

For each FFT window, at first, the frequency domain correlation of traversal reference sequences and all ranging code sequences in frequency domain, and from default K ranging code with maximum related value detection limit and the time domain length of delay thereof corresponding with current FFT window of big extremely little selection; Then, for all FFT windows, choose N maximum and unduplicated ranging code sign indicating number as candidate's ranging code.Simultaneously, according to the time domain correlation of existing formula (4), preserve the peak value sequence of its time domain coherent detection amount in calculated in time domain and received signal.

At last, the legitimacy of candidate's ranging code sequence is detected, and obtain frequency departure, received power and timing offset.In the ranging code search and detection algorithm of the combination of embodiment of the invention time-frequency, legitimacy detects the same bimodal that adopts and gets rid of pseudo-ranging code, effectively the situation of no ranging code in the ranging slot has been done and picked out processing, in addition, owing to exist kN between the original position of the distance measuring signal that the FFT window of the distance measuring signal that frequency domain is estimated and time domain are estimated _dDeviation, utilize kN _dCriterion is that the spacing of FFT window and time domain correlation peak is more than or equal to kN _dThe time, can judge fairly simplely that candidate's ranging code is invalid.Also promptly estimate the pseudo-ranging code that obtains, and the pseudo-ranging code that obtains based on the full code information of FFT window intercepting needs to use the bimodal criterion and gets rid of based on the non-full code information of FFT window intercepting.

Here the bimodal criterion is exactly: according to candidate's ranging code Sequence Detection bimodal, if the spacing of bimodal is greater than predetermined threshold value, then this candidate's ranging code is pseudo-ranging code.

If in remaining candidate's ranging code set, exist the time domain correlation peak doubly to be worth ζ candidate's ranging code doubly less than getting rid of pseudo-ranging code correlation peak maximum, also need it is picked out in the lump, wherein doubly be worth ζ＞1, setting here doubly is worth ζ=1.2.

For obtaining of frequency departure, received power and timing offset, frequency departure and received power are estimated at frequency domain, computing formula is formula (13) and (15) realization at frequency domain, the time-frequency conversion belongs to those skilled in the art's known technology, here derive no longer in detail, what emphasize is, by in frequency domain detection, greatly reduce the size of time domain ranging code search set, thereby improved the precision of estimating.The estimation of timing offset is calculated according to existing formula (5).

The ranging code search of time-frequency combination combines search with the time-frequency in the detection algorithm, under the bigger situation of ranging code collection, reduced the computation complexity of location algorithm, frequency domain detection has then greatly reduced the size of time domain ranging code search set, and the effect that time domain detects has been to simplify processing policy regularly.While bimodal criterion, kN _dThe use of uniting of criterion and correlation peak criterion greatly reduces false alarm probability.

Based on the invention described above method, a kind of uplink distance measuring device also is provided, this device is arranged in the base station, and Fig. 3 is the schematic representation of apparatus of the embodiment of the invention, as shown in Figure 3, comprising: memory module, selection module, judge module, computing module, wherein,

Memory module is used to store the reference range finding sequence that sets in advance;

Select module, be used for the peak value according to the coherent detection amount, the reference range finding sequence selection one group of candidate's ranging code sequence from memory module also sends to judge module; Correlation peak when calculating non-the coupling;

Judge module is used to receive from candidate's ranging code sequence of selecting module, detects bimodal, during greater than predetermined threshold value, abandons ranging code in the spacing of bimodal; When the spacing of bimodal is not more than predetermined threshold value, the notice computing module;

Computing module is used to receive the notice from judge module, and calculated rate deviation, received power and timing offset calculate decision threshold and obtain active ranging code according to this decision threshold.

Further, when computing module is used for correlation peak when the coupling of described ranging code correspondence more than or equal to the amassing of the absolute value of the correlation peak in non-when coupling and default coefficient of reliability α, determine that this ranging code is pseudo-ranging code.

Further, judge module is used in described candidate's ranging code sequence, add up the number of the candidate's ranging code on each ranging slot, the number of candidate's ranging code was calculated the capability correction value of each ranging code greater than 1 o'clock according to the correlation peak of each the candidate's ranging code on this ranging slot in described ranging slot; Abandon that the capability correction value is the pseudo-ranging code of the very big negative value of absolute value on this ranging slot; Abandon the little pseudo-ranging code of absolute value of capability correction value.

This device also further comprises: FFT window generation module is used to obtain the time domain length of delay, and determines the FFT window according to this time domain length of delay.At this moment,

The selection module is further used for: the frequency domain correlation of traversal reference sequences and all ranging code sequences in frequency domain, and from one group of little selection greatly extremely and current definite corresponding ranging code with maximum related value detection limit and time domain length of delay thereof of FFT window;

For all FFT windows, choose default N maximum and unduplicated ranging code as candidate's ranging code.

Judge module is further used for:

Deviation between the original position of the distance measuring signal that described FFT window and time domain are estimated is more than or equal to kN _dThe time, judge that candidate's ranging code is invalid, wherein k represents k range finding user, N _dBe the subcarrier number;

Perhaps, according to candidate's ranging code Sequence Detection bimodal, in the spacing of bimodal during greater than predetermined threshold value, to detect this ranging code be pseudo-ranging code and abandon.

Further, judge module also is used for: when getting rid of pseudo-ranging code correlation peak maximum preset value and doubly be worth ζ times, abandon this ranging code at the time domain correlation peak of ranging code correspondence.

Simultaneously, the present invention also provides a kind of base station, and this base station comprises above-mentioned uplink distance measuring device.

The above is preferred embodiment of the present invention only, is not to be used to limit protection scope of the present invention, all any modifications of being made within the spirit and principles in the present invention, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (27)

1. a uplink distance measuring method sets in advance with reference to the range finding sequence, it is characterized in that this method comprises:

The base station is according to the peak value of coherent detection amount, from reference to one group of candidate's ranging code of range finding sequence selection sequence, and the correlation peak when calculating non-coupling;

According to candidate's ranging code Sequence Detection bimodal, if the spacing of bimodal then abandons ranging code greater than predetermined threshold value; Otherwise, obtain frequency departure, received power and timing offset, calculate decision threshold and obtain active ranging code according to this decision threshold.

2. method according to claim 1 is characterized in that the peak value of described coherent detection amount is a time domain.

3. method according to claim 2 is characterized in that, the described method of obtaining received power is: by the received power on the subcarrier of Paasche Wa Er theorem calculating range finding subchannel correspondence.

4. method according to claim 2 is characterized in that, the described method of obtaining frequency departure is: utilize adjacent two symbols of described candidate's ranging code, do calculus of differences and obtain frequency departure on the range finding subchannel.

5. method according to claim 4, it is characterized in that, the described method of obtaining frequency departure is specially: respectively the frequency domain data on the adjacent sub-channel in i the symbol is done correlation computations, calculate again each correlation computations value and angle, calculate the merchant of this angle and constant 2 π at last, obtain frequency departure.

6. method according to claim 1 is characterized in that, the method for described calculating decision threshold is: the correlation peak during according to the received power that obtains, non-coupling, and ${\left|{\tilde{Y}}_m\right|}^2=N_d\&CenterDot;{\tilde{P}}_m$ Relation is calculated decision threshold η, and formula is as follows:

η=| I _M+ N _m| the γ of β+(M/2), wherein, β is a modifying factor, γ is a coefficient correlation;

$M=\left|{\tilde{Y}}_{m,\mathrm{thresh}}\right|-|I_m+N_m|\&CenterDot;\mathrm{\&beta;},$ Wherein $\left|{\tilde{Y}}_{m,\mathrm{thresh}}\right|=|S_m+I_m+N_m|=\left|{\tilde{Y}}_m\right|\&CenterDot;\sqrt{\frac{P_m}{{\tilde{P}}_m}},$

Be the power attenuation factor, be the ratio of received power with transmitting power, N _dBe the subcarrier number.

7. method according to claim 6 is characterized in that, the described method of obtaining active ranging code is: the coherent detection peak value is active ranging code greater than the ranging code of described decision threshold.

8. method according to claim 6, it is characterized in that, this method further comprises: if the absolute value of the correlation peak of the correlation peak in described when coupling of ranging code correspondence during more than or equal to non-coupling amasss with default coefficient of reliability α is, then this ranging code is pseudo-ranging code.

9. method according to claim 1 is characterized in that, described according to before candidate's ranging code Sequence Detection bimodal, this method also comprises:

In described candidate's ranging code sequence, the number of adding up the candidate's ranging code on each ranging slot, if the number of candidate's ranging code is greater than 1 in the ranging slot, then,

Calculate the capability correction value of each ranging code according to the correlation peak of each the candidate's ranging code on this ranging slot;

Abandon that the capability correction value is the pseudo-ranging code of the very big negative value of absolute value on this ranging slot;

Abandon the little pseudo-ranging code of absolute value of capability correction value.

10. method according to claim 1 is characterized in that, also comprises before this method: obtain the time domain length of delay, and determine the FFT window according to this time domain length of delay.

11. method according to claim 10 is characterized in that, the peak value of described coherent detection amount comprise time domain with frequency domain.

12. method according to claim 11 is characterized in that, described selection candidate ranging code sequence is specially:

The frequency domain correlation of traversal reference sequences and all ranging code sequences in frequency domain, and from one group of little selection greatly extremely and current definite corresponding ranging code with maximum related value detection limit and time domain length of delay thereof of FFT window;

For all FFT windows, choose default N maximum and unduplicated ranging code as candidate's ranging code.

13., it is characterized in that the method for the correlation peak in described calculating non-when coupling is according to claim 1,2 or 11 described methods:

Calculate in other sequence except that described candidate's ranging code, the time domain coherent detection amount peak value sum of corresponding range finding user's ranging code utilizes this and value except that in the number of non-candidate ranging code again, the correlation peak of this quotient during as non-the coupling.

14., it is characterized in that the described method of obtaining timing offset is according to claim 1,2 or 12 described methods:

Coherent detection amount from described candidate's ranging code sequence correspondence

In find out the maximum delay d of corresponding transmission channel _MaxEstimated value, this estimated value is as timing offset.

15. method according to claim 12 is characterized in that, described frequency departure and received power are obtained in frequency domain.

16. method according to claim 12 is characterized in that, this method also comprises:

If the deviation between the original position of the distance measuring signal that described FFT window and time domain are estimated is more than or equal to kN _d, judge that then candidate's ranging code is invalid, wherein k represents k range finding user, N _dBe the subcarrier number;

Perhaps, according to candidate's ranging code Sequence Detection bimodal, in the spacing of bimodal during greater than predetermined threshold value, to detect this ranging code be pseudo-ranging code and abandon.

17. method according to claim 16 is characterized in that, this method also comprises:

If the time domain correlation peak of ranging code correspondence doubly is worth ζ doubly less than getting rid of pseudo-ranging code correlation peak maximum preset value, then abandon this ranging code.

18. method according to claim 1 is characterized in that, described threshold value is spacing and OFDMA symbol lengths N of bimodal _dDifference.

19. method according to claim 1 is characterized in that, described base station is according to the peak value order from big to small of coherent detection amount, from one group of candidate's ranging code of reference range finding sequence selection sequence.

20. a uplink distance measuring device is characterized in that, this device is arranged in the base station, comprising: memory module, selection module, judge module, computing module, wherein,

Memory module is used to store the reference range finding sequence that sets in advance;

Select module, be used for the peak value according to the coherent detection amount, the reference range finding sequence selection one group of candidate's ranging code sequence from memory module also sends to judge module; Correlation peak when calculating non-the coupling;

Judge module is used to receive from candidate's ranging code sequence of selecting module, detects bimodal, during greater than predetermined threshold value, abandons ranging code in the spacing of bimodal; When the spacing of bimodal is not more than predetermined threshold value, the notice computing module;

Computing module is used to receive the notice from judge module, and calculated rate deviation, received power and timing offset calculate decision threshold and obtain active ranging code according to this decision threshold.

21. device according to claim 20, it is characterized in that, described computing module is further used for: the correlation peak when the coupling of described ranging code correspondence determines that this ranging code is pseudo-ranging code during more than or equal to the amassing of the absolute value of the correlation peak in non-when coupling and default coefficient of reliability α.

22. device according to claim 20, it is characterized in that described judge module is further used for: in described candidate's ranging code sequence, the number of adding up the candidate's ranging code on each ranging slot, the number of candidate's ranging code was greater than 1 o'clock in described ranging slot

Calculate the capability correction value of each ranging code according to the correlation peak of each the candidate's ranging code on this ranging slot; Abandon that the capability correction value is the pseudo-ranging code of the very big negative value of absolute value on this ranging slot; Abandon the little pseudo-ranging code of absolute value of capability correction value.

23. device according to claim 20 is characterized in that, this device also comprises: FFT window generation module is used to obtain the time domain length of delay, and determines the FFT window according to this time domain length of delay.

24. device according to claim 23 is characterized in that, described selection module is further used for:

The frequency domain correlation of traversal reference sequences and all ranging code sequences in frequency domain, and from one group of little selection greatly extremely and current definite corresponding ranging code with maximum related value detection limit and time domain length of delay thereof of FFT window;

For all FFT windows, choose default N maximum and unduplicated ranging code as candidate's ranging code.

25. device according to claim 24 is characterized in that, described judge module is further used for:

Deviation between the original position of the distance measuring signal that described FFT window and time domain are estimated is more than or equal to kN _dThe time, judge that candidate's ranging code is invalid, wherein k represents k range finding user, N _dBe the subcarrier number;

Perhaps, according to candidate's ranging code Sequence Detection bimodal, in the spacing of bimodal during greater than predetermined threshold value, to detect this ranging code be pseudo-ranging code and abandon.

26. device according to claim 25 is characterized in that, described judge module is further used for: when getting rid of pseudo-ranging code correlation peak maximum preset value and doubly be worth ζ times, abandon this ranging code at the time domain correlation peak of ranging code correspondence.

27. a base station is characterized in that, this base station comprises the described uplink distance measuring device of claim 20～26.

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