CN101039293B - Apparatus, method and receiver for initial timing synchronization in communication system - Google Patents

Abstract

This invention discloses a device to initialize timing synchronization used in communication system, which comprises a storage unit to storage the received reception sequence samples and to send the storage reception sequence samples to a relativity checking unit, a weighted power computing unit to compute the weighted power of the receipted reception sequence samples and to send the weighted power to a parameter estimation unit, the relativity checking unit to perform the relativity checking of the reception sequence samples sent by the storage unit to generate the relativity coefficient, the parameter estimation unit to estimate the location estimation of the timing synchronization according to the weighted power and the relativity coefficient. This invention also discloses the method and receptor used to initialize timing synchronization in communication system. Very high precision of timing synchronization can be obtained and the errors of the timing synchronization estimation and the frequency deviation estimation can be greatly reduced by the adoption of this invention.

Description

Be used for initial regularly synchronous device, method and receiver in the communication system

Technical field

The present invention relates to the mobile communication technology field, more specifically, relate to and be used for initial regularly synchronous device, method and receiver in the communication system.

Background technology

Current, whole world digital mobile communication system (GSM) and CDMA mobile communication systems (CDMA) have all obtained using very widely in worldwide, and WCDMA mobile communication system (WCDMA) and WCDMA mobile communication system 2000 mobile communication system such as (CDMA2000) have also obtained application to a certain degree within the specific limits.

At present, along with the development of mobile communication system, provide the individual mobile communication terminal that to support various novel business for the user.Because these service needed transmission lot of data are so mobile communication system requires higher Bit Transmission Rate.In the single-carrier system of routine,, can bring difficulty for effective reception of signal because of the degree of depth frequency selective fading of intersymbol interference (ISI) and wireless channel if use higher Bit Transmission Rate.OFDM (OFDM) technology has the ability of antagonism intersymbol interference (ISI), can provide very high spectrum efficiency simultaneously, therefore is regarded as one of most possible transmission technology that adopts of mobile radio system of future generation.The OFDM technology has obtained extensive use at numerous areas such as Digital Subscriber Loop, digital audio/video broadcasting, WLAN (wireless local area network) and wireless MANs.

Simultaneous techniques is one of key technology in the communication system, and regularly simultaneous techniques is very important a kind of in the simultaneous techniques.In ofdm system, regularly synchronous basic principle mainly is based on the correlation of two same sections in the header (Preamble).

In ofdm system, the synchronous method of a kind of initial timing is arranged at present.In this initial time synchronization method, identical and length is the timing synchronizing symbol of 2N the second half section before adopting, and carries out timing synchronously according to the two-part correlation in front and back.

Fig. 1 is for being used for the initial regularly structural representation of synchronous timing synchronizing symbol in the prior art.As shown in Figure 1, this timing synchronizing symbol comprises two sub-synchronizing pilot sequence H1 and H2, and the time domain waveform of H1 and H2 is identical, and wherein the length of H1 and H2 is respectively N.

In the prior art, for initial timing synchronization procedure, transmitting terminal adopts the synchronizing pilot sequence of being made up of two identical sub-synchronizing pilot sequence H1 and H2 shown in Figure 1; At receiving terminal, as shown in Figure 2, successively receive these two sub-synchronizing pilot sequences of H1 and H2, it is synchronous to carry out timing according to the correlation of these two sub-synchronizing pilot sequences then.It is initial in the prior art that regularly synchronous concrete processing procedure can be referring to schematic diagram shown in Figure 2.

In this initial time synchronization method of prior art, because what adopt is the difference relevant treatment of two same sections, therefore when the training symbol of multistage repetition occurring, often the difference of first half of forming by multistage and latter half is relevant similarly handles, so regularly synchronous correlation peak is not obvious, be difficult to find accurately the top, thereby cause the timing synchronization accuracy poor, and make that the error of Frequency offset estimation is bigger.

Summary of the invention

In view of this, main purpose of the present invention is to propose to be used in a kind of communication system initial regularly synchronous device, to reduce the error of regularly estimating synchronously.

Another object of the present invention is to propose to be used in a kind of communication system initial regularly synchronous method, to reduce the error of regularly estimating synchronously.

For achieving the above object, technical scheme of the present invention is achieved in that and is used for initial regularly synchronous device in a kind of communication system that this device comprises:

Memory cell is used to store the receiving sequence sampling that receives, and the receiving sequence sampling of being stored is sent to the correlation detection unit;

The weighted energy computing unit is used to calculate the weighted energy of the receiving sequence sampling that receives, and described weighted energy is sent to parameter estimation unit;

The correlation detection unit, the receiving sequence sampling that is used for that described memory cell is sended over is carried out correlation detection to generate relative coefficient;

Parameter estimation unit is used for estimating regularly sync bit estimation according to described weighted energy and relative coefficient Wherein

Memory cell is connected with the correlation detection unit, and the correlation detection unit is connected with parameter estimation unit, and the weighted energy computing unit is connected with parameter estimation unit;

Described timing sync bit is estimated

For:

${\widehat{\mathrm{\θ}}}_{\mathrm{ML}}=\arg \underset{\mathrm{\θ}}{\max }\{\underset{i=1}{\overset{t-1}{\mathrm{\Σ}}}\left|{\mathrm{\γ}}_i\left(\mathrm{\θ}\right)\right|-\frac{(t-1)\mathrm{\ρ}}{2}\mathrm{\Φ}\left(\mathrm{\θ}\right)\};$

Wherein $\mathrm{\ρ}=\frac{\mathrm{SNR}}{\mathrm{SNR}+1},$ SNR is the signal to noise ratio of receiving sequence; T is the hop count of the subsequence that comprised in the sampling of described synchronizing sequence; Φ (θ) is the energy of t * N receiving sequence sampling sampling point, and θ is regularly a sync bit; γ _i(θ) be the coefficient correlation of correlation detection unit output.

Described parameter estimation unit is further used for estimating the sub-carrier frequencies estimation of deviation according to described weighted energy and relative coefficient.

Described memory cell comprises the delay cell that (t-1) * N connects successively, and wherein N is the length of every cross-talk sequence in the synchronizing sequence, and t is the hop count of the subsequence that comprised in the described synchronizing sequence.

Described correlation detection unit is used for:

With all spacing distances is that two sampling points of N carry out conjugate multiplication, and (t-1) * N numerical value that will obtain adds up, and obtains relative coefficient γ ₁(θ);

Two sampling points that with all spacing distances are 2 * N again carry out conjugate multiplication, and (t-2) * N numerical value that will obtain adds up, and obtain relative coefficient γ ₂(θ);

Go on successively, carry out conjugate multiplication up to two sampling points that with all spacing distances are (t-1) * N, and N the numerical value that obtains is added up, obtain relative coefficient γ _T-1(θ).

Described weighted energy computing unit comprises weight coefficient unit and the accumulator that connects successively, wherein

The weight coefficient unit is used for the sample power of sampling point of receiving sequence be multiply by weight coefficient respectively;

Accumulator is used for the described power that multiply by t * N the receiving sequence sampling sampling point in the nearest moment behind the weight coefficient is added up.

Described weight coefficient is

Wherein $\mathrm{\ρ}=\frac{\mathrm{SNR}}{\mathrm{SNR}+1},$ SNR is the signal to noise ratio of receiving sequence.

Described communication system is an ofdm system.

The value of described N is the arbitrary integer greater than 2.

Be used for initial regularly synchronous method in a kind of communication system, this method comprises:

The receiving sequence sampling that A, storage receive, and calculate the weighted energy of the described receiving sequence sampling that receives;

B, the receiving sequence sampling of storage is carried out correlation detection generating relative coefficient, and estimate regularly sync bit according to described weighted energy and relative coefficient and estimate

Wherein said timing sync bit is estimated

For:

${\widehat{\mathrm{\θ}}}_{\mathrm{ML}}=\arg \underset{\mathrm{\θ}}{\max }\{\underset{i=1}{\overset{t-1}{\mathrm{\Σ}}}\left|{\mathrm{\γ}}_i\left(\mathrm{\θ}\right)\right|-\frac{(t-1)\mathrm{\ρ}}{2}\mathrm{\Φ}\left(\mathrm{\θ}\right)\};$

Wherein $\mathrm{\ρ}=\frac{\mathrm{SNR}}{\mathrm{SNR}+1},$ SNR is the signal to noise ratio of receiving sequence; T is the hop count of the subsequence that comprised in the sampling of described synchronizing sequence; Φ (θ) is the energy of t * N receiving sequence sampling sampling point, and θ is regularly a sync bit; γ _i(θ) be the coefficient correlation of correlation detection unit output.

Further estimate the sub-carrier frequencies estimation of deviation among the step B according to described weighted energy and relative coefficient.

The weighted energy of the receiving sequence sampling that the described calculating of steps A receives comprises:

A1, the power of t * N receiving sequence sampling sampling point be multiply by weight coefficient respectively, wherein the length of synchronizing sequence sampling is t * N, and N is the length of every cross-talk sequence in the synchronizing sequence sampling, and t is the hop count of the subsequence that comprised in the synchronizing sequence sampling;

A2, the described power that multiply by behind the weight coefficient is added up.

Described weight coefficient is

Wherein $\mathrm{\ρ}=\frac{\mathrm{SNR}}{\mathrm{SNR}+1},$ SNR is the signal to noise ratio of receiving sequence.

Described receiving sequence sampling to storage is carried out correlation detection and is comprised to generate relative coefficient:

With all spacing distances is that two sampling points of N carry out conjugate multiplication, and (t-1) * N numerical value that will obtain adds up, and obtains relative coefficient γ ₁(θ);

With all spacing distances is that two sampling points of 2 * N carry out conjugate multiplication, and (t-2) * N numerical value that will obtain adds up, and obtains relative coefficient γ ₂(θ);

Go on successively, carry out conjugate multiplication up to two sampling points that with all spacing distances are (t-1) * N, and N the numerical value that obtains is added up, obtain relative coefficient γ _T-1(θ).

The estimation of described sub-carrier frequencies deviation ε

For:

The value of described N is the arbitrary integer greater than 2.

Described communication system is an ofdm system.

This receiver comprises as above each described synchronous device of initial timing that is used for.

Described communication system is an ofdm system.

As can be seen, initial timing synchronization device proposed by the invention comprises from technique scheme: memory cell is used to store the receiving sequence sampling that receives, and the receiving sequence sampling of being stored is sent to the correlation detection unit; The weighted energy computing unit is used to calculate the weighted energy of the receiving sequence sampling that receives, and weighted energy is sent to parameter estimation unit; The correlation detection unit, the receiving sequence sampling that is used for that memory cell is sended over is carried out correlation detection to generate relative coefficient; Parameter estimation unit is used for estimating regularly sync bit estimation according to weighted energy and relative coefficient.This shows that initial timing synchronization device of the present invention is based on the statistical characteristic analysis of sequential structure to received signal, the detection algorithm of adopt the optimizing time of carrying out estimates, and is not to adopt simple difference relevant treatment, therefore synchronization accuracy height regularly.In addition, based on the statistical characteristic analysis of sequential structure to received signal, and adopt the detection algorithm of the optimizing time of carrying out to estimate that the present invention has also greatly reduced the error of Frequency offset estimation.

Equally, initial time synchronization method proposed by the invention also is based on maximum-likelihood criterion, so timing synchronization accuracy height, and greatly reduces the error of Frequency offset estimation.

Description of drawings

Fig. 1 is for being used for the initial regularly structural representation of synchronous timing synchronizing symbol in the prior art.

Fig. 2 is for being used for initial regularly synchronous processing procedure schematic diagram in the prior art.

Fig. 3 is used for initial regularly synchronous device demonstrative structure schematic diagram for the present invention.

Fig. 4 is for being used for initial regularly synchronous device demonstrative structure schematic diagram according to the embodiment of the invention.

Fig. 5 is used for the exemplary flow schematic diagram of initial time synchronization method for the present invention.

Fig. 6 is for being used for initial regularly synchronous radio frames demonstrative structure schematic diagram according to the present invention.

Fig. 7 for the simulation performance curve ratio of the initial time synchronization method of the present invention and prior art than exemplary schematic representation.

Embodiment

For making the purpose, technical solutions and advantages of the present invention express clearlyer, the present invention is further described in more detail below in conjunction with drawings and the specific embodiments.

Fig. 3 is used for initial regularly synchronous device demonstrative structure schematic diagram for the present invention.As shown in Figure 3, this device comprises:

Memory cell 301 is used to store the receiving sequence sampling that receives, and the receiving sequence sampling of being stored is sent to correlation detection unit 302;

Weighted energy computing unit 304 is used to calculate the weighted energy of the described receiving sequence sampling that receives, and described weighted energy is sent to parameter estimation unit 303;

Correlation detection unit 302, the receiving sequence sampling that is used for that described memory cell 301 is sended over is carried out correlation detection to generate relative coefficient;

Parameter estimation unit 303 is used for estimating regularly sync bit estimation according to described weighted energy and relative coefficient; Wherein

Memory cell 301 is connected with correlation detection unit 302, and correlation detection unit 302 is connected with parameter estimation unit 303, and weighted energy computing unit 304 is connected with parameter estimation unit 303.

Wherein, suppose that the length of receiving sequence sampling is t * N, N is the length of every cross-talk sequence in the described receiving sequence sampling, and t is the hop count of described subsequence.Memory cell 301 can comprise N delay cell that connects successively.

Weighted energy computing unit 304 can comprise weight coefficient unit and the accumulator that connects successively, and wherein the weight coefficient unit is used for the power of t * N receiving sequence sampling sampling point be multiply by weight coefficient respectively; Accumulator is used for the power that multiply by behind the weight coefficient is added up.Preferably, weight coefficient is Wherein $\mathrm{\ρ}=\frac{\mathrm{SNR}}{\mathrm{SNR}+1},$ SNR is the signal to noise ratio of receiving sequence.

Particularly, in Fig. 3,301 pairs of memory cell receive sequential sampling and store, and wherein the size of memory cell 301 is corresponding with the length of the synchronizing signal of inserting at transmitting terminal.Obviously, the present invention there is no further qualification to the size of memory cell 301, as long as be enough to store the receiving sequence sampling.But, suitably reducing the size of memory cell 301 can the control system cost.Be without loss of generality, clear in order to narrate, the length of assumes synchronization signal is t * N sampling point in the narration below, and promptly identical and every segment length is that the sequence of N is formed to synchronizing signal by the t section.Continuous (t-1) * N sampling point that memory cell 301 preferred storages receive recently constantly.Memory cell 301 can be made of the delay cell that connects successively.

Correlation detection unit 302 carries out correlation calculations, and result of calculation is sent into parameter estimation unit 303.Particularly, be the receiving sequence sampling of t * N for length, correlation detection unit 302 at first is that two sampling points of N carry out conjugate multiplication with all spacing distances, and (t-1) * N numerical value that will obtain adds up, and obtains relative coefficient γ ₁(θ); Two sampling points that with all spacing distances are 2 * N then carry out conjugate multiplication, and (t-2) * N numerical value that will obtain adds up, and obtain relative coefficient γ ₂(θ); Go on successively, carry out conjugate multiplication up to two sampling points that with all spacing distances are (t-1) * N, and N the numerical value that obtains is added up, obtain relative coefficient γ _T-1(θ).Here, conjugate multiplication be meant with after the sampling point that receives get conjugation, and and the sampling point that before received multiply each other.

All relative coefficient { γ that correlation detection unit 302 will calculate ₁(θ), γ ₂(θ) ..., γ _T-1(θ) } be sent to parameter estimation unit 303.

Weighted energy computing unit 304 calculates the weighted energy of receiving sequence sampling.Particularly, weighted energy computing unit 304 at first calculates the power of each receiving sequence sampling sampling point, then t * N the about power of sampling point be multiply by weight coefficient respectively Adding up then obtains the energy of sequence, wherein $\mathrm{\ρ}=\frac{\mathrm{SNR}}{\mathrm{SNR}+1},$ SNR is the signal to noise ratio of received signal.

Parameter estimation unit 303 is carried out parameter Estimation according to the weighted energy of weighted energy computing unit 304 outputs and the relative coefficient of correlation detection unit 302 outputs.Particularly, at each constantly, be the sequence of t * N for the length in the memory cell 301, parameter estimation unit 303 is with the relative coefficient delivery of correlation detection unit 302 outputs and add up, deduct then weighted energy and, obtain this cost function constantly; In the time cycle of observing, parameter estimation unit 303 calculates each cost function constantly, selects the location estimation value of the pairing time location of cost function maximum as synchronizing sequence

Further, according to Constantly, the relative coefficient { γ that exported of correlation detection unit 302 ₁(θ), γ ₂(θ) ..., γ _T-1(θ) } can estimate sub-carrier frequencies deviation ε.

Based on structure shown in Figure 3, Fig. 4 is for being used for initial regularly synchronous device demonstrative structure schematic diagram according to the embodiment of the invention.As shown in Figure 4, N delay cell Z wherein ^NConstitute memory cell 301; Weight coefficient unit and accumulator constitute the weighted energy computing unit; This device also comprises the correlation detection unit, and other parts constitute parameter estimation unit then.Be elaborated to being used for initial time synchronization method among the present invention below.

Fig. 5 is used for the exemplary flow schematic diagram of initial time synchronization method for the present invention, and as shown in Figure 5, this method comprises:

Step 501: the receiving sequence sampling that storage receives, and calculate the weighted energy of the receiving sequence sampling that receives;

Here, the weighted energy of the receiving sequence sampling that calculating receives can comprise: the power of t * N receiving sequence sampling sampling point be multiply by weight coefficient respectively, wherein the length of receiving sequence sampling is t * N, N is the length of every cross-talk sequence in the described receiving sequence sampling, and t is the hop count of described subsequence; And then the power that will multiply by behind the weight coefficient adds up, and wherein weight coefficient is preferred

Wherein $\mathrm{\ρ}=\frac{\mathrm{SNR}}{\mathrm{SNR}+1},$ SNR is the signal to noise ratio of receiving sequence.

Step 502: the receiving sequence sampling of storage is carried out correlation detection with the generation relative coefficient, and estimate regularly sync bit estimation according to described weighted energy and relative coefficient.

Here, the estimation of described timing sync bit θ

For

${\widehat{\mathrm{\θ}}}_{\mathrm{ML}}=\arg \underset{\mathrm{\θ}}{\max }\{\underset{i=1}{\overset{t-1}{\mathrm{\Σ}}}\left|{\mathrm{\γ}}_i\left(\mathrm{\θ}\right)\right|-\frac{(t-1)\mathrm{\ρ}}{2}\mathrm{\Φ}\left(\mathrm{\θ}\right)\},$

Wherein r (k) is the continuous sampling point of receiving terminal; θ is time migration; ε is the relative frequency skew; N (k) is a white Gaussian noise; θ and ε are timing synchronization position and the subcarrier frequency offset that will estimate; Φ (θ) be receiving sequence energy and, γ _i(θ) be the coefficient correlation of correlation detection unit output.

Can also further estimate the sub-carrier frequencies estimation of deviation, the estimation of resulting sub-carrier frequencies deviation ε according to described weighted energy and relative coefficient

For:

More than apparatus structure of the present invention and method flow are illustrated.Below algorithm of the present invention is elaborated:

Fig. 6 is for being used for initial regularly synchronous radio frames demonstrative structure schematic diagram according to the present invention.If the frame structure of transmitting terminal signal as shown in Figure 6, wherein the length of 4 sections repetitions is the sequence configuration frame synchronous head of N.Though be that example describes with 4 sections herein, it will be appreciated by those of skill in the art that the present invention to hop count and indefinite, can be for greater than 2 arbitrary integer.

The continuous sampling point r (k) of receiving terminal is formulated as follows:

r(k)＝s(k-θ)exp(j2πkε/N)+n(k) (1)

Wherein s (k) is the time-domain signal after the emission symbol process IFFT conversion; θ is time migration; ε is the relative frequency skew; N (k) is a white Gaussian noise; θ and ε are timing synchronization position and the subcarrier frequency offset that will estimate.

Suppose sequence except the frame synchronization head be independently and average be zero random sequence, in the viewing duration of a frame, there is following correlation in the received signal sequence so:

$E\left\{r\left(k\right)r^{*}(k+l)\right\}=\left\{\begin{array}{ccc}{\mathrm{\σ}}_s^2+{\mathrm{\σ}}_n^2& l=0& \\ {\mathrm{\σ}}_s^2{e}^{-j2\mathrm{\π\ϵt}}& l=\mathrm{tN}& t\∈\left\{\mathrm{1,2,3}\right\}\\ 0& \mathrm{others}& \end{array}\right.---\left(2\right)$

Wherein ${\mathrm{\σ}}_s^2=E\left\{{\left|s\left(k\right)\right|}^2\right\},$ ${\mathrm{\σ}}_n^2=E\{{\left|n\left(k\right)\right|}^2\}.$

Log-likelihood function Λ (θ, ε) be defined as probability density function f (r (k) | θ, logarithm ε), promptly

Λ(θ，ε)＝log f(r(k)|θ，ε) (3)

For simplicity, the back directly use f (r (k)) expression f (r (k) | θ, ε).

Because in the receiving sequence of a frame length, the reception sampling point that only belongs to synchronous head just has correlation, therefore can release from following formula:

$\mathrm{\Λ}(\mathrm{\θ},\mathrm{\ϵ})=\log \left(\underset{k\∈I_1}{\∏}f(r\left(k\right),r(k+N),r(k+2N),r(k+3N))\underset{k\∉I_1\∪\·\·\·\∪I_4}{\∏}f\left(r\left(k\right)\right)\right)$

$=\log \left(\underset{k\∈I_1}{\mathrm{\Π}}\frac{f(r\left(k\right),r(k+N),r(k+2N),r(k+3N))}{f\left(r\left(k\right)\right)f\left(r(k+N)\right)f\left(r(k+2N)\right)f\left(r(k+3N)\right)}\underset{k}{\mathrm{\Π}}f\left(r\left(k\right)\right)\right)---\left(4\right)$

In following formula, f (r (k), r (k+N), r (k+2N), r (k+3N)) obeys the multiple Gaussian Profile of 4 dimensions; F (r (k)), f (r (k+N)), f (r (k+2N)), f (r (k+3N)) all obey the multiple Gaussian Profile of one dimension.Further obtain:

$\mathrm{\Λ}(\mathrm{\θ},\mathrm{\ϵ})=N\log \frac{{({\mathrm{\σ}}_s^2+{\mathrm{\σ}}_n^2)}^4}{\left|R\right|}+\log \left(\underset{k}{\mathrm{\Π}}f\left(r\left(k\right)\right)\right)+$

$\underset{k=\mathrm{\θ}}{\overset{\mathrm{\θ}+N-1}{\mathrm{\Σ}}}(-{\stackrel{\→}{r}}^H{R}^{-1}\stackrel{\→}{r}+\frac{{\left|r\left(k\right)\right|}^2+{\left|r(k+N)\right|}^2+{\left|r(k+2N)\right|}^2+{\left|r(k+3N)\right|}^2}{{\mathrm{\σ}}_s^2+{\mathrm{\σ}}_n^2})---\left(5\right)$

Wherein R represents correlation matrix,

With θ, ε is irrelevant, and

Be constant.By eliminating and the item for the treatment of that estimated parameter is irrelevant, following formula further abbreviation is:

$\widetilde{\mathrm{\Λ}}(\mathrm{\θ},\mathrm{\ϵ})=\underset{k=\mathrm{\θ}}{\overset{\mathrm{\θ}+N-1}{\mathrm{\Σ}}}(-{\stackrel{\→}{r}}^H{R}^{-1}\stackrel{\→}{r}+\frac{{\left|r\left(k\right)\right|}^2+{\left|r(k+N)\right|}^2+{\left|r(k+2N)\right|}^2+{\left|r(k+3N)\right|}^2}{{\mathrm{\σ}}_s^2+{\mathrm{\σ}}_n^2})---\left(6\right)$

Through computing, can obtain:

$\widetilde{\mathrm{\Λ}}(\mathrm{\θ},\mathrm{\ϵ})=\left|{\mathrm{\γ}}_1\left(\mathrm{\θ}\right)\right|\cos (2\mathrm{\π\ϵ}+\∠{\mathrm{\γ}}_1\left(\mathrm{\θ}\right))+\left|{\mathrm{\γ}}_2\left(\mathrm{\θ}\right)\right|\cos (4\mathrm{\π\ϵ}+\∠{\mathrm{\γ}}_2\left(\mathrm{\θ}\right))$

$+\left|{\mathrm{\γ}}_3\left(\mathrm{\θ}\right)\right|\cos (6\mathrm{\π\ϵ}+\∠{\mathrm{\γ}}_3\left(\mathrm{\θ}\right))-\frac{3\mathrm{\ρ}}{2}\mathrm{\Φ}\left(\mathrm{\θ}\right)---\left(7\right)$

Wherein

${\mathrm{\γ}}_1\left(\mathrm{\θ}\right)=\underset{k=\mathrm{\θ}}{\overset{\mathrm{\θ}+N-1}{\mathrm{\Σ}}}\{r\left(k\right)r{(k+N)}^{*}+r(k+N)r{(k+2N)}^{*}+r(k+2N)r{(k+3N)}^{*}\}$

${\mathrm{\γ}}_2\left(\mathrm{\θ}\right)=\underset{k=\mathrm{\θ}}{\overset{\mathrm{\θ}+N-1}{\mathrm{\Σ}}}\{r\left(k\right)r{(k+2N)}^{*}+r(k+N)r{(k+3N)}^{*}\}$

${\mathrm{\γ}}_3\left(\mathrm{\θ}\right)=\underset{k=\mathrm{\θ}}{\overset{\mathrm{\θ}+N-1}{\mathrm{\Σ}}}\left\{r\left(k\right)r{(k+3N)}^{*}\right\}$

$\mathrm{\Φ}\left(\mathrm{\θ}\right)=\underset{k=\mathrm{\θ}}{\overset{\mathrm{\θ}+N-1}{\mathrm{\Σ}}}\{{\left|r\left(k\right)\right|}^2+{\left|r(k+N)\right|}^2+{\left|r(k+2N)\right|}^2+{\left|r(k+3N)\right|}^2\}$

$\mathrm{\ρ}=\frac{{\mathrm{\σ}}_s^2}{{\mathrm{\σ}}_s^2+{\mathrm{\σ}}_n^2}=\frac{\mathrm{SNR}}{\mathrm{SNR}+1}$

Maximum likelihood algorithm is wanted simultaneously estimate symbol regularly synchronization position θ and sub-carrier frequencies deviation ε, so the likelihood function maximization finishes in two steps,

$\underset{(\mathrm{\θ},\mathrm{\ϵ})}{\max }\widetilde{\mathrm{\Λ}}(\mathrm{\θ},\mathrm{\ϵ})=\underset{\mathrm{\θ}}{\max }\underset{\mathrm{\ϵ}}{\max }\widetilde{\mathrm{\Λ}}(\mathrm{\θ},\mathrm{\ϵ})---\left(8\right)$

Making the cos item in (7) is 1, then can get

$\widetilde{\mathrm{\Λ}}(\mathrm{\θ},\mathrm{\ϵ})=\left|{\mathrm{\γ}}_1\left(\mathrm{\θ}\right)\right|+\left|{\mathrm{\γ}}_2\left(\mathrm{\θ}\right)\right|+\left|{\mathrm{\γ}}_3\left(\mathrm{\θ}\right)\right|-\frac{3\mathrm{\ρ}}{2}\mathrm{\Φ}\left(\mathrm{\θ}\right)---\left(9\right)$

Can release being estimated as of θ from following formula

${\widehat{\mathrm{\θ}}}_{\mathrm{ML}}=\arg \underset{\mathrm{\θ}}{\max }\{\left|{\mathrm{\γ}}_1\left(\mathrm{\θ}\right)\right|+\left|{\mathrm{\γ}}_2\left(\mathrm{\θ}\right)\right|+\left|{\mathrm{\γ}}_3\left(\mathrm{\θ}\right)\right|-\frac{3\mathrm{\ρ}}{2}\mathrm{\Φ}\left(\mathrm{\θ}\right)\}---\left(10\right)$

Further, can obtain being estimated as of sub-carrier frequencies deviation ε:

Further, for the synchronizing sequence that the t section repeats, the log-likelihood expression formula of parameter Estimation is:

$\widetilde{\mathrm{\Λ}}(\mathrm{\θ},\mathrm{\ϵ})=\underset{i=1}{\overset{t-1}{\mathrm{\Σ}}}\left|{\mathrm{\γ}}_i\left(\mathrm{\θ}\right)\right|\cos (2\mathrm{\π\ϵ}\×i+\∠{\mathrm{\γ}}_i\left(\mathrm{\θ}\right))-\frac{(t-1)\mathrm{\ρ}}{2}\mathrm{\Φ}\left(\mathrm{\θ}\right)---\left(12\right)$

Wherein

${\mathrm{\γ}}_1\left(\mathrm{\θ}\right)=\underset{k=\mathrm{\θ}}{\overset{\mathrm{\θ}+N-1}{\mathrm{\Σ}}}\{r\left(k\right)r{(k+N)}^{*}+r(k+N)r{(k+2N)}^{*}+\·\·\·+r(k+(t-2)N)r{(k+(t-1)N)}^{*}\}$

${\mathrm{\γ}}_i\left(\mathrm{\θ}\right)=\underset{k=\mathrm{\θ}}{\overset{\mathrm{\θ}+N-1}{\mathrm{\Σ}}}\{r\left(k\right)r{(k+\mathrm{iN})}^{*}+r(k+N)r{(k+(i+1)N)}^{*}+\·\·\·+r(k+(t-1-i)N)r{(k+(t-1)N)}^{*}\}$

${\mathrm{\γ}}_{t-1}\left(\mathrm{\θ}\right)=\underset{k=\mathrm{\θ}}{\overset{\mathrm{\θ}+N-1}{\mathrm{\Σ}}}\left\{r\left(k\right)r{(k+(t-1)N)}^{*}\right\}$

$\mathrm{\Φ}\left(\mathrm{\θ}\right)=\underset{k=\mathrm{\θ}}{\overset{\mathrm{\θ}+\mathrm{tN}-1}{\mathrm{\Σ}}}\left\{{\left|r\left(k\right)\right|}^2\right\}$

Can release being estimated as of θ and ε:

${\widehat{\mathrm{\θ}}}_{\mathrm{ML}}=\arg \underset{\mathrm{\θ}}{\max }\{\underset{i=1}{\overset{t-1}{\mathrm{\Σ}}}\left|{\mathrm{\γ}}_i\left(\mathrm{\θ}\right)\right|-\frac{(t-1)\mathrm{\ρ}}{2}\mathrm{\Φ}\left(\mathrm{\θ}\right)\}---\left(13\right)$

Further, can obtain being estimated as of sub-carrier frequencies deviation ε:

Below performance of the present invention has been carried out simulating, verifying, wherein simulation parameter is specifically referring to table 1.Fig. 7 for the simulation performance curve ratio of the initial time synchronization method of the present invention and prior art than exemplary schematic representation.

Data bandwidth	1.25MHZ
		Synchronization channel bandwidth	1.25MHZ
Channel model	The TU channel, the 3km/h speed of a motor vehicle, the 2GHz carrier frequency, uncorrelated

Data bandwidth	1.25MHZ
		Antenna configurations	Receive antenna for 12
Multi-access mode	Down link OFDMA
		Frame synchronization structure	4 sections are identical, and every segment length is the synchronizing sequence of N=128,

Table 1

As seen from Figure 7, when the synchronous error detection probability of initial timing be 10 ^-2The time, the present invention can obtain the gain about 2dB.

Can recognize that the synchronous device of initial timing proposed by the invention can be applied in the receiver in the communication system, can improve regularly synchronization accuracy equally, and greatly reduce regularly synchronous error.

Equally, apparatus and method proposed by the invention had both gone for ofdm system, also can be applicable to the OFDMA system based on OFDM.More than with the ofdm system be example invention has been described, but it will be appreciated by those of skill in the art that the present invention is suitable equally for other multi-carrier communications systems.With OFDM is that example only describes to exemplary, and is not used in and limits the invention.

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

Claims (18)

1. be used for initial regularly synchronous device in a communication system, it is characterized in that this device comprises:

Memory cell is used to store the receiving sequence sampling that receives, and the receiving sequence sampling of being stored is sent to the correlation detection unit;

The weighted energy computing unit is used to calculate the weighted energy of the receiving sequence sampling that receives, and described weighted energy is sent to parameter estimation unit;

The correlation detection unit, the receiving sequence sampling that is used for that described memory cell is sended over is carried out correlation detection to generate relative coefficient;

Parameter estimation unit is used for estimating regularly sync bit estimation according to described weighted energy and relative coefficient

Wherein

Memory cell is connected with the correlation detection unit, and the correlation detection unit is connected with parameter estimation unit, and the weighted energy computing unit is connected with parameter estimation unit;

Described timing sync bit is estimated

For:

${\widehat{\mathrm{\θ}}}_{\mathrm{ML}}=\arg \underset{\mathrm{\θ}}{\max }\left\{\underset{i=1}{\overset{t-1}{\mathrm{\Σ}}}\right|{\mathrm{\γ}}_i\left(\mathrm{\θ}\right)|-\frac{(t-1)\mathrm{\ρ}}{2}\mathrm{\Φ}\left(\mathrm{\θ}\right)\};$

Wherein

SNR is the signal to noise ratio of receiving sequence; T is the hop count of the subsequence that comprised in the sampling of described synchronizing sequence; Φ (θ) is the energy of t * N receiving sequence sampling sampling point, and θ is regularly a sync bit; γ _i(θ) be the coefficient correlation of correlation detection unit output.

2. be used for initial regularly synchronous device in the communication system according to claim 1, it is characterized in that described parameter estimation unit is further used for estimating the sub-carrier frequencies estimation of deviation according to described weighted energy and relative coefficient.

3. be used for initial regularly synchronous device in the communication system according to claim 1, it is characterized in that, described memory cell comprises (t-1) * N delay cell that connects successively, wherein N is the length of every cross-talk sequence in the synchronizing sequence sampling, and t is the hop count of the subsequence that comprised in the described synchronizing sequence sampling.

4. be used for initial regularly synchronous device in the communication system according to claim 3, it is characterized in that described correlation detection unit is used for:

With all spacing distances is that two sampling points of N carry out conjugate multiplication, and (t-1) * N numerical value that will obtain adds up, and obtains relative coefficient γ ₁(θ);

Two sampling points that with all spacing distances are 2 * N again carry out conjugate multiplication, and (t-2) * N numerical value that will obtain adds up, and obtain relative coefficient γ ₂(θ);

Go on successively, carry out conjugate multiplication up to two sampling points that with all spacing distances are (t-1) * N, and N the numerical value that obtains is added up, obtain relative coefficient γ _T-1(θ), wherein θ is regularly a sync bit.

5. be used for initial regularly synchronous device in the communication system according to claim 3, it is characterized in that described weighted energy computing unit comprises weight coefficient unit and the accumulator that connects successively, wherein:

The weight coefficient unit is used for the sample power of sampling point of receiving sequence be multiply by weight coefficient respectively;

Accumulator is used for the described power that multiply by t * N the receiving sequence sampling sampling point in the nearest moment behind the weight coefficient is added up.

6. be used for initial regularly synchronous device in the communication system according to claim 5, it is characterized in that described weight coefficient is

Wherein

SNR is the signal to noise ratio of receiving sequence.

7. according to being used for initial regularly synchronous device in each described communication system among the claim 1-6, it is characterized in that described communication system is an orthogonal frequency division multiplex OFDM system.

8. according to being used for initial regularly synchronous device in each described communication system among the claim 1-6, it is characterized in that the value of described N is the arbitrary integer greater than 2.

9. be used for initial regularly synchronous method in a communication system, it is characterized in that this method comprises:

The receiving sequence sampling that A, storage receive, and calculate the weighted energy of the described receiving sequence sampling that receives;

B, the receiving sequence sampling of storage is carried out correlation detection generating relative coefficient, and estimate regularly sync bit according to described weighted energy and relative coefficient and estimate

Wherein said timing sync bit is estimated

For:

${\widehat{\mathrm{\θ}}}_{\mathrm{ML}}=\arg \underset{\mathrm{\θ}}{\max }\left\{\underset{i=1}{\overset{t-1}{\mathrm{\Σ}}}\right|{\mathrm{\γ}}_i\left(\mathrm{\θ}\right)|-\frac{(t-1)\mathrm{\ρ}}{2}\mathrm{\Φ}\left(\mathrm{\θ}\right)\};$

Wherein

SNR is the signal to noise ratio of receiving sequence; T is the hop count of the subsequence that comprised in the sampling of described synchronizing sequence; Φ (θ) is the energy of t * N receiving sequence sampling sampling point, and θ is regularly a sync bit; γ _i(θ) be the coefficient correlation of correlation detection unit output.

10. be used for initial regularly synchronous method in the communication system according to claim 9, it is characterized in that,

Further estimate the sub-carrier frequencies estimation of deviation among the step B according to described weighted energy and relative coefficient.

11. be used for initial regularly synchronous method in the communication system according to claim 9, the weighted energy of the receiving sequence sampling that the described calculating of steps A receives comprises:

A1, the power of t * N receiving sequence sampling sampling point be multiply by weight coefficient respectively, wherein the length of synchronizing sequence sampling is t * N, and N is the length of every cross-talk sequence in the synchronizing sequence sampling, and t is the hop count of the subsequence that comprised in the synchronizing sequence sampling;

A2, the described power that multiply by behind the weight coefficient is added up.

12. be used for initial regularly synchronous method in the communication system according to claim 11, it is characterized in that described weight coefficient is

Wherein

SNR is the signal to noise ratio of receiving sequence.

13. be used for initial regularly synchronous method in the communication system according to claim 9, it is characterized in that described receiving sequence sampling to storage is carried out correlation detection and comprised to generate relative coefficient:

With all spacing distances is that two sampling points of N carry out conjugate multiplication, and (t-1) * N numerical value that will obtain adds up, and obtains relative coefficient γ ₁(θ);

With all spacing distances is that two sampling points of 2 * N carry out conjugate multiplication, and (t-2) * N numerical value that will obtain adds up, and obtains relative coefficient γ ₂(θ);

Go on successively, carry out conjugate multiplication up to two sampling points that with all spacing distances are (t-1) * N, and N the numerical value that obtains is added up, obtain relative coefficient γ _T-1(θ), wherein θ is regularly a sync bit.

14. be used for initial regularly synchronous method in the communication system according to claim 10, it is characterized in that the estimation of described sub-carrier frequencies deviation ε

For:

${\widehat{\mathrm{\ϵ}}}_{\mathrm{ML}}\left(\mathrm{\θ}\right)=-\frac{1}{2\mathrm{\π}}\∠{\mathrm{\γ}}_1\left({\widehat{\mathrm{\θ}}}_{\mathrm{ML}}\right).$

15., it is characterized in that the value of described N is the arbitrary integer greater than 2 according to being used for initial regularly synchronous method in each described communication system among the claim 9-14.

16., it is characterized in that described communication system is an ofdm system according to being used for initial regularly synchronous method in each described communication system among the claim 9-14.

17. the receiver in the communication system is characterized in that, this receiver comprises as being used for initial regularly synchronous device as described in each among the claim 1-6.

18. receiver according to claim 17 is characterized in that, described communication system is an ofdm system.

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