CN101835167B - Frequency spectrum synchronization method for dynamic frequency spectrum access of discontinuous frequency spectrum OFDM (Orthogonal Frequency Division Multiplexing) - Google Patents

Abstract

The invention discloses a frequency spectrum synchronization method for dynamic frequency spectrum access of a discontinuous frequency spectrum OFDM (Orthogonal Frequency Division Multiplexing), which comprises the processes of: (1) sending data frames, wherein each data frame is formed by sequentially connecting a training symbol, a synchronization symbol and a data symbol back and forth; (2) receiving the data frames; (3) coarsely synchronizing the frequency spectrum; (4) fine synchronizing the frequency spectrum: detecting synchronization words by a receiving end by using a maximum ratio merging method and carrying out frequency spectrum synchronization by using the synchronization words obtained by detection; and (5) receiving data: determining the position of a subband according to the obtained synchronization words, receiving data from subcarriers in the subband, and then demodulating, deinterleaving, correcting errors and decoding to obtain emitted data. The invention belongs to the solutions of signaling in band, saves the frequency spectrum resources, reduces the processing delay time of a system, and ensures the real time of frequency spectrum synchronization.

Description

Be used for the frequency spectrum method for synchronous that discontinuous frequency spectrum OFDM dynamic spectrum inserts

Technical field

The invention belongs to wireless communication technology field; Relate to the dynamic spectrum access method that adopts orthogonal frequency-division multiplex singal (OFDM); Specifically a kind of receiving terminal and synchronous method of transmitting terminal frequency spectrum of keeping, frequency spectrum are meant that synchronously receiving terminal can find out OFDM number of subcarriers and position that transmitting terminal uses.

Background technology

Along with the continuous development of communication requirement becomes increasingly scarce with the frequency spectrum resource that can supply communicate by letter; Dynamic spectrum access technology based on cognitive radio is a kind of promising solution because it can with a kind of opportunistic mode multiplexing with share frequency spectrum resource.That is to say that when authorized user does not use certain section frequency spectrum unauthorized user is allowed to identification and uses this section instantaneous spectrum.

For the broadband unauthorized user, OFDM is a kind of good signal structure, because utilize OFDM transmit communications signals on discrete frequency band effectively.Disturb for fear of the authorized user of working is formed, unauthorized user can only use the subcarrier transmission signals of part of O FDM, and these subcarriers that are used can be discontinuous.

In the spectrum environment of dynamic change, the transmit leg of unauthorized user can change the subcarrier number and the position of its use at any time according to authorized user to the operating position of frequency spectrum.For the recipient of unauthorized user, the problem of a key be keep and transmit leg synchronous, promptly the recipient will understand transmit leg and adopted which subcarrier.If the subcarrier number that the recipient adopts and position are different with transmit leg, obviously will cause the deterioration of the serious error rate and Packet Error Ratio.We are called the frequency spectrum stationary problem with above-mentioned stationary problem.The frequency spectrum stationary problem is a key issue of discontinuous OFDM dynamic spectrum connecting system, and at present, relevant research and technology are also quite few.The prior art relevant with the present invention has:

Part bandwidth mode (FBW Mode) detects and method for synchronous, sees Y.W.Jae, G.K.Hyun; H.K.Yun, S.Iickho, and S.S.Myung; " Fractional Bandwidth Mode Detection and Synchronization for OFDM-Based Cognitive Radio Systems; " In Proc.IEEE Vehicular Technology Conference, May 2008, pp.1599-1603.

Part bandwidth mode method for synchronous is to mate and realize through receiving information and several possible part bandwidth mode.21 kinds of part bandwidth mode of system's predefined, the subcarrier number and the position of every kind of pattern use are fixed.Transmit leg can only use wherein a kind of part bandwidth mode to send signal.The recipient realizes that through detecting the part bandwidth mode that receives in the signal frequency spectrum is synchronous.

The system model of detection of part bandwidth mode and method for synchronous is as shown in Figure 1.Transmit leg is confirmed an only part bandwidth mode (FBW Mode) through frequency spectrum perception (Sensing), and uses the subcarrier of stipulating in this pattern to send signal.The recipient realizes that through detecting the part bandwidth mode that receives in the signal frequency spectrum is synchronous.

The shortcoming of such scheme is that system's part bandwidth mode quantity that can define is very limited, because the part bandwidth mode is many, can influence the accuracy of detection.21 kinds of patterns only can be provided, this 21 pattern even can not support discrete frequency spectrum situation in the above-mentioned paper.Under a limited number of situation of part bandwidth mode, system can't make accurately careful adjustment, thereby cause the spectrum utilization efficiency of system fully not improved to the dynamic change of spectrum environment.

Summary of the invention

The purpose of this invention is to provide a kind of frequency spectrum method for synchronous that discontinuous OFDM dynamic spectrum inserts that is used for, this method can realize being with interior transmitting synchronous information, and does not need the band outer control channel of extra special use.

The frequency spectrum method for synchronous that is used for discontinuous frequency spectrum OFDM dynamic spectrum access provided by the invention is characterized in that this method comprises the steps:

(1) transmit data frames:

Each Frame is connected to form before and after successively by training symbol, synchronizing symbol and data symbol, wherein, training symbol on frequency domain with vector P=[P ₁..., P _k... P _N] expression, P _kAmplitude and the phase place of expression training symbol on the k number of sub-carrier, wherein,

P _k＝P′ _k·T _k

Wherein N representes the sum of subcarrier, and k representes the sequence number of subcarrier, k=1, and 2 ..., N, P ' _kBe vector P '=[P ' ₁, P ' _k..., P ' _N] in element, P ' is illustrated in the training symbol that system under the continuous situation of frequency spectrum uses; T _kThe state of representing the k number of sub-carrier is if this subcarrier can be used T _k=1, otherwise T _k=0;

Synchronizing symbol on frequency domain with vector C=[C ₁..., C _k..., C _N] expression, wherein C _kAmplitude and the phase place of expression synchronizing symbol on the k number of sub-carrier,

C _k＝C′ _k·T _k

C ' wherein _kBe vector C '=[C ' ₁..., C ' _k..., C ' _N] in element, establish the exponent number of M for modulation, C ' repeats M by synchronization character modulation symbol S and doubly obtains, promptly

C′ _k＝S _n；n＝kmod(N/M)

Wherein kmod (N/M) expression k gets surplusly to (N/M), (N/M) is a positive integer; S _nBe vector S=[S ₁..., S _n..., S _(N/M)] in element, wherein n representes the sequence number of element in the vector S, n=1,2 ..., (N/M); Through the error correcting encoder coding, interleaver interweaves S by synchronization character B, and the M contrast makes, and wherein synchronization character B representes the position of available subcarrier;

Data symbol on frequency with vector D=[D ₁..., D _k..., D _N] expression, wherein D _kAmplitude and the phase place of expression data symbol on the k number of sub-carrier;

Data bit is through error correcting encoder coding, and interleaver interweaves, modulation, obtain length and be the modulated data symbol sequence D of V '=[D ' ₁..., D ' _i..., D ' _V], wherein, i representes the sequence number of element in the modulated data symbol sequence, i=1, and 2 ..., V, D ' _iIn V element be mapped to successively among the vector D on V the available subcarrier, all the other unavailable subcarriers are made as 0, obtain data symbol D;

(2) receiving data frames:

The data that receive remove Cyclic Prefix, string and conversion, and FFT is handled, and obtains receiving channel disturbance to produce the frame of distortion;

(3) frequency spectrum is slightly synchronous:

(3.1) calculate reception training symbol and the partial auto-correlation of transmitting training symbol on subcarrier k:

Training symbol on the k number of sub-carrier that receives is expressed as U _k, when L＜k≤N-L, the ρ of partial auto-correlation on the subcarrier k _kFor

${\mathrm{\ρ}}_k=\frac{|\underset{r=k-L}{\overset{k+L}{\mathrm{\Σ}}}{U}_r\·{\left({P_r}^{\′}\right)}^H|}{\sqrt{\underset{r=k-L}{\overset{k+L}{\mathrm{\Σ}}}{U}_r\·{\left(U_r\right)}^H}\sqrt{\underset{r=k-L}{\overset{k+L}{\mathrm{\Σ}}}{P_r}^{\′}\·{\left({P_r}^{\′}\right)}^H}}$

When 1≤k≤L,

${\mathrm{\ρ}}_k=\frac{|\underset{r=1}{\overset{k+L}{\mathrm{\Σ}}}{U}_r\·{\left({P_r}^{\′}\right)}^H|}{\sqrt{\underset{r=1}{\overset{k+L}{\mathrm{\Σ}}}{U}_r\·{\left(U_r\right)}^H}\sqrt{\underset{r=1}{\overset{k+L}{\mathrm{\Σ}}}{P_r}^{\′}\·{\left({P_r}^{\′}\right)}^H}}$

When N-L＜k≤N

${\mathrm{\ρ}}_k=\frac{|\underset{r=k-L}{\overset{N}{\mathrm{\Σ}}}{U}_r\·{\left({P_r}^{\′}\right)}^H|}{\sqrt{\underset{r=k-L}{\overset{N}{\mathrm{\Σ}}}{U}_r\·{\left(U_r\right)}^H}\sqrt{\underset{r=k-L}{\overset{N}{\mathrm{\Σ}}}{P_r}^{\′}\·{\left({P_r}^{\′}\right)}^H}}$

Wherein L has determined to participate in the subcarrier number that local correlation is calculated, and the span of L does

Wherein Right Round downwards; (P _r') ^H(U _r) ^HRepresent P respectively _r' and U _rCarry out the Hermitian transposition;

(3.2) with ρ _kSort by size, receiving terminal is chosen a wherein maximum W pairing subcarrier as the receiving terminal available subcarrier, and all the other subcarriers are unavailable subcarrier; Thick synchronously in parameter W elect half after the minimum available subcarrier number of transmitting terminal and the system maximum sub-carrier number addition as;

(4) frequency spectrum is carefully synchronous:

(4.1) make m=0, Y _n=0;

(4.2) if (n+m (N/M)) number of sub-carrier is the thick available subcarrier of confirming in synchronously, gets into step (4.3), otherwise get into step (4.4);

(4.3) when R＜(n+m (N/M))≤N-R,

does

${\hat{H}}_{(n+m\·(N/M))}=\underset{j=(n+m\·(N/M))-R}{\overset{(n+m\·(N/M))+R}{\mathrm{\Σ}}}\frac{U_j}{(2R+1)\·P_j^{\′}}$

When 1≤(n+m (N/M))≤R

${\hat{H}}_{(n+m\·(N/M))}=\underset{j=1}{\overset{(n+m\·(N/M))+R}{\mathrm{\Σ}}}\frac{U_j}{(2R+1)\·P_j^{\′}}$

When N-R＜(n+m (N/M))≤N

${\hat{H}}_{(n+m\·(N/M))}=\underset{j=(n+m\·(N/M))-R}{\overset{N}{\mathrm{\Σ}}}\frac{U_j}{(2R+1)\·P_j^{\′}}$

Wherein R has determined to participate in the subcarrier number of channel estimation calculation, and the span of R is

Change step (4.5) then over to;

(4.4)

directly is set to 0;

(4.5) obtain corresponding to S through the maximum ratio merge algorithm _nReceiving symbol Y _n, promptly

$Y_n=Y_n+F_{(n+m\·(N/M))}\·{\hat{H}}_{(n+m\·(N/M))}^H$

Wherein, F _{(n+m (N/M))}Synchronizing symbol on (n+m (N/M)) number of sub-carrier that expression receives,

It is right to represent

Carry out the Hermitian transposition,

It is the estimated value of (n+m (N/M)) number of sub-carrier upper signal channel response;

(4.6) make m=m+1, judge m≤M-1, if get into step (4.2), otherwise change step (4.7) over to;

(4.7) with Y _nCarry out demodulation, deinterleaving and decoding and obtain synchronization character.

(5) Data Receiving:

Confirm the position of subband according to the synchronization character that obtains, the subcarrier from subband receives data, carries out demodulation then, deinterleaving, the data that error correction decoding obtains launching.

The present invention sends a synchronizing symbol through transmitting terminal and gives receiving terminal, and synchronizing symbol is formed through convolutional encoding, modulation and repeated encoding by synchronization character.Synchronization character has been described transmitting terminal and has been used which subcarrier.Receiving terminal uses maximum ratio merging method to carry out the detection of synchronization character, and it is synchronous that the synchronization character that utilizes detection to obtain carries out frequency spectrum.The present invention does not need the band outer control channel of extra special use just can realize that the frequency spectrum of receiving-transmitting sides is synchronous, and the technical scheme of being carried belongs to the method for transmitting synchronous information in the band, promptly comes transmitting synchronous information through a synchronizing symbol.This synchronizing symbol is positioned at after the training symbol, before the data symbol.

The invention belongs to the in-band signalling solution, saved frequency spectrum resource, reduced the processing delay of system, guaranteed the frequency spectrum real-time property of synchronizing.

Description of drawings

Fig. 1 is the schematic flow sheet of the inventive method;

Fig. 2 is a discontinuous OFDM dynamic spectrum connecting system block diagram of the present invention;

Fig. 3 is a sub-band division sketch map of the present invention;

Fig. 4 is that synchronizing symbol of the present invention generates the steps flow chart block diagram;

Fig. 5 is frame structure of the present invention and receiver processing procedure.

Embodiment

As shown in Figure 1, embodiment provided by the invention specifically may further comprise the steps:

1, a kind of frequency spectrum method for synchronous that is used for discontinuous frequency spectrum OFDM dynamic spectrum access is characterized in that this method comprises the steps:

(1) transmit data frames:

Each Frame is connected to form before and after successively by training symbol, synchronizing symbol and data symbol, wherein, training symbol on frequency domain with vector P=[P ₁..., P _k... P _N] expression, P _kAmplitude and the phase place of expression training symbol on the k number of sub-carrier,

P _k＝P′ _k·T _k

Wherein N representes the sum of subcarrier, and k representes the sequence number of subcarrier, k=1, and 2 ..., N, P ' _kBe vector P '=[P ' ₁, P ' _k..., P ' _N] in element, P ' is illustrated in the training symbol that system under the continuous situation of frequency spectrum uses.T _kThe state of representing the k number of sub-carrier is if this subcarrier can be used T _k=1, otherwise T _k=0;

Synchronizing symbol on frequency domain with vector C=[C ₁..., C _k..., C _N] expression, wherein C _kAmplitude and the phase place of expression synchronizing symbol on the k number of sub-carrier,

C _k＝C′ _k·T _k

C ' wherein _kBe vector C '=[C ' ₁..., C ' _k..., C ' _N] in element, C ' repeats M by synchronization character modulation symbol S and doubly obtains, promptly

C′ _k＝S _n；n＝kmod(N/M)

Wherein kmod (N/M) expression k gets surplusly to (N/M), and N and M are satisfied divides exactly relation, and promptly (N/M) is a positive integer.S _nBe vector S=[S ₁..., S _n..., S _(N/M)] in element, wherein n representes the sequence number of element in the vector S, n=1,2 ..., (N/M).Through the error correcting encoder coding, interleaver interweaves S by synchronization character B, and M contrast system (like PSK and QAM modulation) obtains, and wherein synchronization character B representes the position of available subcarrier.Represent the available subcarrier position with synchronization character among the present invention, the method that a kind of synchronization character of giving an example below obtains, but the present invention is not limited to this method, also can adopt other mode to obtain synchronization character.

Stipulate that discontinuous frequency spectrum OFDM dynamic spectrum connecting system uses the V number of sub-carrier to communicate, the span of V is [1, N]; Suppose that V discrete available subcarrier can be divided into continuous separately Q section, is called Q subband; Use the beginning subcarrier sequence number of each subband and finish the position that the subcarrier sequence number is represented these subbands; The beginning subcarrier sequence number k of q subband _QsBinary number representation be (k _Qs) 2; Finish subcarrier sequence number k _QeBinary number representation be (k _Qe) 2,1≤q≤Q wherein, (k _Qs) 2 with (k _Qe) 2 each usefulness

Individual bit representes, Expression is to log ₂N rounds up; B=[(k then _1s) 2, (k _1e) 2 ..., (k _Qs) 2, (k _Qe) 2 ... (k _Qs) 2, (k _Qe) 2], total among the B

Individual bit.

Data symbol on frequency with vector D=[D ₁..., D _k..., D _N] expression, wherein D _kAmplitude and the phase place of expression data symbol on the k number of sub-carrier;

Data bit is through error correcting encoder coding, and interleaver interweaves, modulation, obtain length and be the modulated data symbol sequence D of V '=[D ' ₁..., D ' _i..., D ' _V], wherein, i representes the sequence number of element in the modulated data symbol sequence, i=1, and 2 ..., V, D ' _iIn V element be mapped to successively among the vector D on V the available subcarrier, all the other unavailable subcarriers are made as 0, obtain data symbol D.

(2) receiving data frames

The data that receive remove Cyclic Prefix, string and conversion, and FFT is handled, and obtains receiving channel disturbance to produce the frame of distortion.

(3) frequency spectrum is slightly synchronous

It is slightly synchronous that the training symbol that the receiving terminal basis of discontinuous frequency spectrum OFDM dynamic spectrum connecting system receives carries out frequency spectrum.

(3.1) calculate reception training symbol and the partial auto-correlation of transmitting training symbol on subcarrier k:

Training symbol on the k number of sub-carrier that receives is expressed as U _k, when L＜k≤N-L, the ρ of partial auto-correlation on the subcarrier k _kFor

${\mathrm{\ρ}}_k=\frac{|\underset{r=k-L}{\overset{k+L}{\mathrm{\Σ}}}{U}_r\·{\left({P_r}^{\′}\right)}^H|}{\sqrt{\underset{r=k-L}{\overset{k+L}{\mathrm{\Σ}}}{U}_r\·{\left(U_r\right)}^H}\sqrt{\underset{r=k-L}{\overset{k+L}{\mathrm{\Σ}}}{P_r}^{\′}\·{\left({P_r}^{\′}\right)}^H}}$

When 1≤k≤L,

${\mathrm{\ρ}}_k=\frac{|\underset{r=1}{\overset{k+L}{\mathrm{\Σ}}}{U}_r\·{\left({P_r}^{\′}\right)}^H|}{\sqrt{\underset{r=1}{\overset{k+L}{\mathrm{\Σ}}}{U}_r\·{\left(U_r\right)}^H}\sqrt{\underset{r=1}{\overset{k+L}{\mathrm{\Σ}}}{P_r}^{\′}\·{\left({P_r}^{\′}\right)}^H}}$

When N-L＜k≤N

${\mathrm{\ρ}}_k=\frac{|\underset{r=k-L}{\overset{N}{\mathrm{\Σ}}}{U}_r\·{\left({P_r}^{\′}\right)}^H|}{\sqrt{\underset{r=k-L}{\overset{N}{\mathrm{\Σ}}}{U}_r\·{\left(U_r\right)}^H}\sqrt{\underset{r=k-L}{\overset{N}{\mathrm{\Σ}}}{P_r}^{\′}\·{\left({P_r}^{\′}\right)}^H}}$

Wherein L has determined to participate in the subcarrier number that local correlation is calculated, and the span of L does

(P _r') ^H(U _r) ^HRepresent P respectively _r' and U _rCarry out the Hermitian transposition.

(3.2) with ρ _kSort by size, receiving terminal is chosen a wherein maximum W pairing subcarrier as the receiving terminal available subcarrier, and all the other subcarriers are unavailable subcarrier, said process we to be called frequency spectrum slightly synchronous.Under the bigger situation of interference ratio, frequency spectrum slightly exists certain probability the wrongheaded situation of available subcarrier to occur synchronously, utilizes frequency spectrum carefully can obtain synchronously correcting.Thick synchronously in parameter W elect half after the minimum available subcarrier number of transmitting terminal and the system maximum sub-carrier number addition as; Can guarantee that like this available subcarrier of most of transmitting terminal becomes the available subcarrier of receiving terminal; Simultaneously can remove a part of unavailable subcarrier again, guarantee that systematic function is improved to some extent.

(4) frequency spectrum is carefully synchronous

It is carefully synchronous that available subcarrier that slightly obtains synchronously through frequency spectrum and unavailable subcarrier information and the synchronizing symbol that receives are accomplished frequency spectrum.

Specifically be to obtain corresponding to S through the maximum ratio merge algorithm _mReceiving symbol Y _n, promptly

$Y_n=\underset{m=0}{\overset{M-1}{\mathrm{\Σ}}}{F}_{(n+m\·(N/M))}\·{\hat{H}}_{(n+m\·(N/M))}^H$

Wherein, F _{(n+m (N/M))}Synchronizing symbol on (n+m (N/M)) number of sub-carrier that expression receives,

It is right to represent Carry out the Hermitian transposition, It is the estimated value of (n+m (N/M)) number of sub-carrier upper signal channel response.If (n+m (N/M)) number of sub-carrier is the thick available subcarrier of having confirmed in synchronously; When R＜(n+m (N/M))≤N-R,

does

${\hat{H}}_{(n+m\·(N/M))}=\underset{j=(n+m\·(N/M))-R}{\overset{(n+m\·(N/M))+R}{\mathrm{\Σ}}}\frac{U_j}{(2R+1)\·P_j^{\′}}$

When 1≤(n+m (N/M))≤R

${\hat{H}}_{(n+m\·(N/M))}=\underset{j=1}{\overset{(n+m\·(N/M))+R}{\mathrm{\Σ}}}\frac{U_j}{(2R+1)\·P_j^{\′}}$

When N-R＜(n+m (N/M))≤N

${\hat{H}}_{(n+m\·(N/M))}=\underset{j=(n+m\·(N/M))-R}{\overset{N}{\mathrm{\Σ}}}\frac{U_j}{(2R+1)\·P_j^{\′}}$

Wherein R has determined to participate in the subcarrier number of channel estimation calculation; If (n+m (N/M)) number of sub-carrier is the thick unavailable subcarrier of having confirmed in synchronously,

directly is set to 0 to the span of R for

.

With Y _nCarry out demodulation, deinterleaving and decoding and just can obtain synchronization character.

(5) Data Receiving

Through after frequency spectrum carefully obtains correct synchronization character synchronously, the recipient knows which subcarrier transmit leg has used, and receives data symbol and demodulating data from these subcarriers that used only then.Carry out deinterleaving then, the data that error correction decoding obtains launching.

The above; Be merely the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, any technical staff who is familiar with the present technique field is in the technical scope that the present invention discloses; The variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.

Claims (2)

1. one kind is used for the frequency spectrum method for synchronous that discontinuous frequency spectrum OFDM dynamic spectrum inserts, and it is characterized in that this method comprises the steps:

(1) transmit data frames:

Each Frame is connected to form before and after successively by training symbol, synchronizing symbol and data symbol, wherein, training symbol on frequency domain with vector P=[P ₁..., P _k..., P _N] expression, P _kAmplitude and the phase place of expression training symbol on the k number of sub-carrier, wherein,

P _k＝P′ _k·T _k

Wherein N representes the sum of subcarrier, and k representes the sequence number of subcarrier, k=1, and 2 ..., N, P ' _kBe vector P '=[P ' ₁..., P ' _k..., P ' _N] in element, P ' is illustrated in the training symbol that system under the continuous situation of frequency spectrum uses; T _kThe state of representing the k number of sub-carrier is if this subcarrier can be used T _k=1, otherwise T _k=0;

Synchronizing symbol on frequency domain with vector C=[C ₁..., C _k..., C _N] expression, wherein C _kAmplitude and the phase place of expression synchronizing symbol on the k number of sub-carrier,

C _k＝C′ _k·T _k

C ' wherein _kBe vector C '=[C ' ₁..., C ' _k..., C ' _N] in element, establish the exponent number of M for modulation, C ' repeats M by synchronization character modulation symbol S and doubly obtains, promptly

C′ _k＝S _n；n＝kmod(N/M)

Wherein kmod (N/M) expression k gets surplusly to (N/M), (N/M) is a positive integer; S _nBe vector S=[S ₁..., S _n..., S _(N/M)] in element, wherein n representes the sequence number of element in the vector S, n=1,2 ..., (N/M); Through the error correcting encoder coding, interleaver interweaves S by synchronization character B, and the M contrast makes, and wherein synchronization character B representes the position of available subcarrier;

Data symbol on frequency with vector D=[D ₁..., D _k..., D _N] expression, wherein D _kAmplitude and the phase place of expression data symbol on the k number of sub-carrier;

Data bit is through error correcting encoder coding, and interleaver interweaves, modulation, obtain length and be the modulated data symbol sequence D of V '=[D ' ₁..., D ' _i..., D ' _V], wherein, i representes the sequence number of element in the modulated data symbol sequence, i=1, and 2 ..., V, D ' _iIn V element be mapped to successively among the vector D on V the available subcarrier, all the other unavailable subcarriers are made as 0, obtain data symbol D;

(2) receiving data frames:

The data that receive remove Cyclic Prefix, string and conversion, and FFT is handled, and obtains receiving channel disturbance to produce the frame of distortion;

(3) frequency spectrum is slightly synchronous:

(3.1) calculate reception training symbol and the partial auto-correlation of transmitting training symbol on subcarrier k:

Training symbol on the k number of sub-carrier that receives is expressed as U _k, when L＜k≤N-L, the ρ of partial auto-correlation on the subcarrier k _kFor

When 1≤k≤L,

When N-L＜k≤N

Wherein L has determined to participate in the subcarrier number that local correlation is calculated, and the span of L does

(P _r') ^H(U _r) ^HRepresent P respectively _r' and U _rCarry out the Hermitian transposition;

(3.2) with ρ _kSort by size, receiving terminal is chosen a wherein maximum W pairing subcarrier as the receiving terminal available subcarrier, and all the other subcarriers are unavailable subcarrier; Thick synchronously in parameter W elect half after the minimum available subcarrier number of transmitting terminal and the system maximum sub-carrier number addition as;

(4) frequency spectrum is carefully synchronous:

(4.1) make m=0, Y _n=0;

(4.2) if (n+m (N/M)) number of sub-carrier is the thick available subcarrier of confirming in synchronously, gets into step (4.3), otherwise get into step (4.4);

(4.3) when R＜(n+m (N/M))≤N-R, does

When 1≤(n+m (N/M))≤R

When N-R＜(n+m (N/M))≤N

Wherein R has determined to participate in the subcarrier number of channel estimation calculation, and the span of R is

Change step (4.5) then over to;

(4.4)

directly is set to 0;

(4.5) obtain corresponding to S through the maximum ratio merge algorithm _nReceiving symbol Y _n, promptly

Wherein, F _{(n+m (N/M))}Synchronizing symbol on (n+m (N/M)) number of sub-carrier that expression receives, It is right to represent

Carry out the Hermitian transposition,

It is the estimated value of (n+m (N/M)) number of sub-carrier upper signal channel response;

(4.6) make m=m+1, judge m≤M-1, if get into step (4.2), otherwise change step (4.7) over to;

(4.7) with Y _nCarry out demodulation, deinterleaving and decoding and obtain synchronization character;

(5) Data Receiving:

Confirm the position of subband according to the synchronization character that obtains, the subcarrier from subband receives data, carries out demodulation then, deinterleaving, the data that error correction decoding obtains launching.

2. frequency spectrum method for synchronous according to claim 1 is characterized in that, synchronization character B obtains according to following process:

Stipulate that discontinuous frequency spectrum OFDM dynamic spectrum connecting system uses the V number of sub-carrier to communicate, the span of V is [1, N]; Suppose that V discrete available subcarrier can be divided into continuous separately Q section, is called Q subband; Use the beginning subcarrier sequence number of each subband and finish the position that the subcarrier sequence number is represented these subbands; The beginning subcarrier sequence number k of q subband _QsBinary number representation be (k _Qs) 2; Finish subcarrier sequence number k _QeBinary number representation be (k _Qe) 2,1≤q≤Q wherein, (k _Qs) 2 with (k _Qe) 2 each usefulness Individual bit representes,

Expression is to log ₂N rounds up; B=[(k then _1s) 2, (k _1e) 2 ..., (k _Qs) 2, (k _Qe) 2 ..., (k _Qs) 2, (k _Qe) 2], total among the B

Individual bit.

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