CN104052690A - Frequency synchronization method for cooperative communication system - Google Patents

Abstract

The invention discloses a frequency synchronization method for a cooperative communication system. In the cooperative communication system, frequency synchronization needs to be performed on both of a relay node and an objective node. In a direct link transmission mode, the problem of frequency synchronization between a source node and the objective node belongs to the problems of frequency synchronization of a point-to-point communication system. In a first cooperative stage in a cooperative mode, the relay node and the objective node only receive signals from the source node, and the problem of frequency synchronization of the relay node and the objective node also belongs to the problems of frequency synchronization of the point-to-point communication system. In a second cooperative stage, the objective node simultaneously receives superposed signals from two cooperative nodes. In the cooperative communication system, the two cooperative nodes adopt training sequences with identical structures, the training sequences are used for a frequency estimation part, therefore, superposition of two paths of signals can be regarded as the situation that a prefix passes by an equivalent signal of a multipath channel passes, and the problem of frequency synchronization also belongs to the problems of frequency synchronization of the point-to-point communication system.

Description

For cooperation communication system medium frequency synchronous method

Technical field

The present invention relates to the communications field, more specifically, relate to for cooperation communication system medium frequency synchronous method.

Background technology

In recent years, along with the increase of wireless mobile communications number of users and the raising of people's living standard, to provide speech to be difficult to gradually meet consumers' demand as main traditional GSM and CDMA technology.For meeting people to the ever-increasing needs of wireless multimedia communication business, under the background being becoming tight frequency spectrum resource day, multiaerial system, due to significantly transmission performance and the spectrum efficiency of elevator system, is paid close attention to widely.But, the volume of mobile terminal, the practical application that Power Limitation has restricted multiaerial system greatly.Cooperation communication system is as a kind of expansion of multi-antenna technology, become the focus of communications field research in recent years, utilize mutual cooperation transmission data of node in wireless network or add special relay node cooperation transmission, can, in improving system spectrum utilance, effectively reduce and increase the great amount of cost that bring base station.

In Turbo Detection for Cooperative Communication, due to not mating mutually between different and multiple crystal oscillators of relaying location distribution, between multiple repeated links, have multiple different carrier frequency shifts, this is the most remarkable part that Turbo Detection for Cooperative Communication is different from traditional Point-to-Point Communication System.In academia, there are a lot of large quantity research to frequency deviation problem.According to the difference of frequency deviation algorithm for estimating application scenarios, can be divided into continuous mode algorithm and burst mode algorithm; According to the difference of algorithm applicable elements, can be divided into thick synchronized algorithm and thin synchronized algorithm; The data type difference of utilizing according to algorithm, can be divided into blind algorithm for estimating and training sequence algorithm for estimating.

In actual cooperation communication system, Frequency Synchronization is to realize the prerequisite of reliable reception.In cooperation communication system, information source node and via node all can be to destination node transmitted signals.Due to reasons such as the phase noises of introducing in the crystal oscillator characteristic difference of different nodes or communication process, the frequency of occurrences is asynchronous.Therefore, before channel estimating and data demodulates, need to set up Frequency Synchronization.

Application number is " 201010545376.2 ", and the patent application of " working in coordination with in wireless network for synchronous method and device " by name, is to have provided one for synchronous method and device for collaborative wireless network.This invention propose a kind of in collaborative wireless network for synchronous method, comprise step: A, generation frequency domain training sequence, non-zero training data in this frequency domain training sequence is mapped in the first subcarrier set, the subcarrier in this first subcarrier set taking the first predetermined value subcarrier as interval evenly corresponding on carrier wave; Wherein, the first subcarrier set and other at least one cooperative nodes have spacing bias between corresponding subcarrier set separately, and other at least one cooperative nodes separately corresponding subcarrier set also have between two spacing bias; B, according to frequency domain training sequence, generate corresponding time domain pilot; And C, transmission time domain pilot.The object of this patent is in order to improve the precision that between cooperative nodes and receiver, the time offset estimation in synchronizing process and frequency deviation are estimated.

This application has proposed in a kind of the first cooperative nodes working in coordination with wireless network for working in coordination with other at least one cooperative nodes the method and the device thereof that send pilot tone, its training sequence design is complicated, computation complexity is high, can see that by its simulation result figure the mean square deviation of its Carrier frequency offset estimation is larger, that is to say that the accuracy of its Frequency Synchronization is not too high.

The patent application of " frequency offset estimation method of low-complexity collaborative relay system 201110072457.X " is the frequency deviation estimating method that proposes a kind of low complex degree for collaboration relay system.The method of estimation of its proposition, utilize the periodicity of each via node training sequence, receiving sequence vector is converted to homography, and then utilize the row conjugation symmetric properties of correlation matrix to construct respectively corresponding real number matrix, and do respectively the quick feature decomposition of real number matrix and the quick rooting of real polynomial equation, partially estimate thereby realize quick multifrequency.

Concrete grammar is:

1) convert receiving sequences y, be converted into the matrix Y of Q × P, wherein, the element of matrix Y can be expressed as: [Y] q, p=[y] qP+p, 0≤q < Q, 0≤p < P, P and Q are positive integer, and P × Q=N, N is the length of training sequence, and q represents the line index of matrix Y, and p represents the column index of matrix Y;

2) utilize normalization row conjugation symmetrical matrix, structure real number variance matrix;

3) to step 2) the real number variance matrix that obtains does feature decomposition, obtains the normalization characteristic vector corresponding to signal subspace;

4) according to step 3) the normalization characteristic vector that obtains, the normalization row conjugation symmetrical matrix that utilizes geometric maps relation to obtain, structure real polynomial;

5) to step 4) real polynomial that obtains carries out quick rooting computing, finds out the K of imaginary part absolute value minimum in all paired roots to root, and wherein K is the number of via node in collaboration relay system;

6) calculate the equivalent frequency deviation to root corresponding to this K, and rearrange according to order from small to large;

7) to step 6) K that obtains an equivalent frequency deviation does respectively corresponding add operation, obtains K a to be estimated frequency deviation value.

The method that this patent application proposes need be carried out repeatedly matrix operation, feature decomposition etc., and computation complexity is high.

Summary of the invention

The object of the invention is to propose one for cooperation communication system medium frequency synchronous method, solve the asynchronous problem of communication for coordination medium frequency, algorithm complex is low, easily realizes.

To achieve these goals, technical scheme of the present invention is:

A kind of for cooperation communication system medium frequency synchronous method, this communication system belongs to many relay cooperatives wireless transmitting system, is made up of source node, via node and destination node; Each node configuration individual antenna, all multi-carrier modulation/demodulation modes of the OFDM CP-OFDM of employing with Cyclic Prefix; Frame structure comprises prefix, training sequence and three parts of data sequence;

Frequency Synchronization comprises via node Frequency Synchronization and destination node Frequency Synchronization;

The process of described via node Frequency Synchronization is: while there is frequency error, realizing after sign synchronization, after the OFDM window that the length of training sequence is N removes CP, interior reception signal is

Training sequence is carried out to Frequency Synchronization and comprises frequency error estimation and offset frequency error:

Wherein the frequency error of training sequence estimates it is to utilize the repetitive structure that removes the training sequence after CP, and repetitive structure comprises s ₁, s ₂, s ₁=s ₂;

The observed value of OFDM window is utilize the method for estimation based on auto-correlation second-order statistics to carry out frequency error estimation; Obtain the carrier frequency error Δ f of source node to via node link _srestimated value table be shown

The offset frequency error of training sequence is to utilize training sequence to draw frequency error estimated value afterwards, via node need to carry out frequency compensation to the time-domain signal receiving, the time-domain signal after compensation suc as formula wherein T represents sampling period, and n represents sampling time, n=1 ..., N; Time-domain signal after compensation is for the follow-up channel estimating based on training sequence and the processing to data sequence;

Realizing after Alamouti coding, via node is modulated to time-domain signal the carrier wave identical with source node transmission frequencysend again, compensate again to realize frequency; The time-domain signal that is via node also needs to be multiplied by the carrier frequency error Δ f of the estimated source node arriving to via node link _sr;

Described destination node Frequency Synchronization comprises frequency error estimation and offset frequency error.

In the preferred scheme of one, the detailed process of described via node Frequency Synchronization is:

While there is frequency error, realizing after sign synchronization, after the OFDM window that the length of training sequence is N removes CP, interior reception signal is

$r_n^{\mathrm{sr}}=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}\mathrm{nT}}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}{s}_{n-l}+z_n^{\mathrm{sr}},n=1,...,N$

Wherein the l footpath channel parameter to via node is saved in expression source, l=0 ..., L _sr-1; s _nrepresent the transmitted signal of time domain, corresponding is training sequence part here, and s _-l=s _n-l; Δ f _sr=f _s-f _rrepresent the carrier frequency error of source node to via node link, f _sand f _rthe carrier frequency that represents respectively source node and via node, T represents sampling period;

Training sequence is carried out to Frequency Synchronization and comprises frequency error estimation and offset frequency error:

Wherein the frequency error of training sequence estimates it is to utilize the repetitive structure that removes the training sequence after CP, and repetitive structure comprises s ₁, s ₂, s ₁=s ₂;

The observed value of OFDM window is utilize the method for estimation based on auto-correlation second-order statistics to carry out frequency error estimation;

$\begin{array}{c}{r}_1^{\mathrm{sr}}\left(n\right)=r^{\mathrm{sr}}\left(n\right)=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}\mathrm{nT}}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}s(n-l)+z_n^{\mathrm{sr}}\\ =e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}\mathrm{nT}}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}{s}_1(n-l)+z_n^{\mathrm{sr}},n=1,...,\frac{N_S}{2}\end{array}$

$\begin{array}{c}{r}_2^{\mathrm{sr}}\left(n\right)=r^{\mathrm{sr}}(\frac{N_S}{2}+n)=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}(\frac{N_S}{2}+n)T}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}s((\frac{N_S}{2}+n)-l)+z_{(\frac{N_S}{2}+n)}^{\mathrm{sr}}\\ =e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}\frac{N_S}{2}T}\left(e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}\mathrm{nT}}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}{s}_2(n-l)\right)+z_{(\frac{N_S}{2}+n)}^{\mathrm{sr}},n=1,...,\frac{N_S}{2}\end{array}$

Due to s ₁=s ₂, therefore can obtain

According to law of great number, be approximately white Gaussian noise, obtain frequency error Δ f _srestimated value table be shown;

$\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}=\frac{1}{\mathrm{\&pi;}{N}_{S}T}\arg \left\{{\left(r_1^{\mathrm{sr}}\right)}^H\left(r_2^{\mathrm{sr}}\right)\right\}.$

N _st represents the size of OFDM window, under T mono-stable condition, and N _slonger, OFDM window is just larger, and the precision of estimation is just high;

The offset frequency error of training sequence is to utilize training sequence to draw frequency error estimated value afterwards, via node need to carry out frequency compensation to the time-domain signal receiving, the time-domain signal after compensation suc as formula wherein T represents sampling period, and n represents sampling time, n=1 ..., N; Time-domain signal after compensation is for the follow-up channel estimating based on training sequence and the processing to data sequence;

$\begin{array}{c}{y}_n^{\mathrm{sr}}=e^{-j2\mathrm{\&pi;\&Delta;}{\hat{f}}_{\mathrm{sr}}\mathrm{nT}}{r}_n^{\mathrm{sr}}\\ =e^{j2\mathrm{\&pi;}(\mathrm{\&Delta;}{f}_{\mathrm{sr}}-\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}})\mathrm{nT}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}{s}_{n-l}+e^{-j2\mathrm{\&pi;\&Delta;}{\hat{f}}_{\mathrm{sr}}\mathrm{nT}}{z}_n^{\mathrm{sr}}}\\ =e^{j2\mathrm{\&pi;}(\mathrm{\&Delta;}{f}_{\mathrm{sr}}-\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}})\mathrm{nT}}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}{s}_{n-l}+{\hat{z}}_n^{\mathrm{sr}}\end{array}$

Realizing after Alamouti coding, via node is modulated to time-domain signal the carrier wave identical with source node transmission frequencysend again, compensate again to realize frequency; The time-domain signal that is via node also needs to be multiplied by the frequency error Δ f between estimated via node and the source node arriving _sr, it is the symbol of n sampling time.

In the preferred scheme of one, the detailed process of described destination node Frequency Synchronization is:

Under single or two relay cooperative transmission patterns, establish source node and via node and be respectively H to the frequency domain channel between destination node ^sdand H ^rd, destination node receives from the time-domain signal of source node and via node and is expressed as

$\begin{array}{c}{r}_n^d=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{rd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{\hat{s}}_{n-l}^r+z_n^d\\ =e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{rd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}\left(e^{+j2\mathrm{\&pi;\&Delta;}{\hat{f}}_{\mathrm{sr}}(n-l)T_s}{s}_{n-l}^r\right)+z_n^d\\ \&ap;e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;}(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}+\mathrm{\&Delta;}{f}_{\mathrm{rd}})n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{s}_{n-l}^r+z_n^d\end{array}$

Wherein Δ f _sd=f _s-f _dwith Δ f _rd=f _r-f _drepresent respectively source node and the via node carrier frequency error to destination node link, f _dfor the carrier frequency of destination node, due to estimated value, non-vanishing, therefore can obtain

$\begin{array}{c}\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}+\mathrm{\&Delta;}{f}_{\mathrm{rd}}\\ =(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+\mathrm{\&Delta;}{f}_{\mathrm{sr}}+\mathrm{\&Delta;}{f}_{\mathrm{rd}}\\ =(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+(f_s-f_r)+(f_r-f_d)\\ =(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+f_s-f_d\\ =(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+\mathrm{\&Delta;}{f}_{\mathrm{sd}}\end{array}$

Further try to achieve

$\begin{array}{c}{r}_n^d=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;}[(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+\mathrm{\&Delta;}{f}_{\mathrm{sd}}]n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{s}_{n-l}^r+z_n^d\\ =e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}(\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;}(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{s}_{n-l}^r)+z_n^d\end{array}$

Although $\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}}\&NotEqual;0,$ But due to, $\mathrm{\&Delta;}{f}_{\mathrm{sd}}>>\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}}$ (Δ f _sdmuch larger than $\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}}$ ), therefore ignore, and then can obtain

$\begin{array}{c}{r}_n^d=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;}[(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+\mathrm{\&Delta;}{f}_{\mathrm{sd}}]n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{s}_{n-l}^r+z_n^d\\ =e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}(\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{s}_{n-l}^r)+z_n^d\end{array}$

For the signal of the training sequence part for Frequency Estimation, meet therefore

Its frequency error is estimated Δ f _sdestimated value table be shown wherein with the time domain that is respectively corresponding training sequence part repetitive substructure receives signal; Estimate Δ f according to frequency error _sdestimated value the time-domain signal receiving is carried out to offset frequency error.

In the preferred scheme of one, the prefix part of described communication system adopts [P1, P2]=[A, reverse (A)] structure.The estimation of this structure is than traditional based on the obvious peak point of having of auto-correlation second-order statistics and very steep slope, and it is high that its estimated accuracy is wanted.

In the preferred scheme of one, it is N that described source node adopts length _sreally fixed sequence as training sequence, by 2 identical parts composition; CP part is taken from the last L of s _cPlength part in order to ensure that under multipath interference channel environment training sequence is not subject to the interference of prefix part, the length L of CP part _cPbe greater than the length L of multipath channel _h, meet L _cP>L _h.

Beneficial effect of the present invention is: carry out Frequency Estimation, frequency counteracting at via node place, frequency compensates again, can simplify like this Frequency Synchronization problem of system.Because, cooperation communication system can be regarded virtual many single-input single-output system (SISO system)s as, destination node can be received the signal that comes from source node, via node, and owing to having passed through wireless channel, there is skew in frequency, carry out synchronously multiple frequencies in destination node, algorithm can be very complicated and along with increasing of via node is more complicated.By method of the present invention, can avoid the problem of multiple Frequency Synchronization of destination node, and in the time that via node increases, also can not make the Frequency Synchronization problem of system become more complicated.

In native system, via node and destination node all need to carry out Frequency Synchronization.Under direct link transmission mode, source node belongs to the Frequency Synchronization problem of point-to-point digital communication system to the Frequency Synchronization problem between destination node; In the cooperation stage one under collaboration mode, via node and destination node all receive only the signal from source node, and its Frequency Synchronization problem also belongs to the Frequency Synchronization problem of point-to-point digital communication system; In the cooperation stage two, destination node receives from two cooperative nodes (source node and via nodes simultaneously, or two via nodes) superposed signal, because two cooperative nodes in native system all adopt the training sequence (for Frequency Estimation part) of identical structure, therefore the stack of two paths of signals can be regarded as to the signal of prefix through an equivalent multipath channel, therefore its Frequency Synchronization problem also belongs to the Frequency Synchronization problem of point-to-point digital communication system.

Brief description of the drawings

Fig. 1 is the schematic diagram of many relay cooperative communications system.

Fig. 2 is the schematic diagram of system frame structure.

Fig. 3 is the schematic diagram of prefix structure in system frame structure.

Fig. 4 is the schematic diagram for the structure of the training sequence of Frequency Estimation in system frame structure.

Fig. 5 is the Equivalent Base-Band communication system schematic diagram of point-to-point digital communication system.

Fig. 6 is the Equivalent Base-Band communication system schematic diagram of direct link transmission.

Fig. 7 is that source node transmitting terminal base-band digital is processed block diagram.

Fig. 8 is that the destination node receiving terminal base-band digital under direct transmission mode is processed block diagram.

Fig. 9 is direct link and single relay coordination transmission system schematic diagram.

Figure 10 is that source node transmitting terminal base-band digital is processed block diagram.

Figure 11 is that the base-band digital of AF via node is processed block diagram.

Figure 12 is that the base-band digital of DF via node is processed block diagram.

Figure 13 is that the base-band digital of destination node under tie link and single relay cooperative transmission pattern is processed block diagram (cooperation stage one).

Figure 14 is that the base-band digital of destination node under tie link and single relay cooperative transmission pattern is processed block diagram (cooperation stage two).

Figure 15 is the process schematic diagram of via node Frequency Synchronization of the present invention (estimate and offset).

Figure 16 is the schematic diagram of training sequence of the present invention.

The process schematic diagram that Figure 17 via node frequency of the present invention compensates again.

Figure 18 is the process schematic diagram of the object of the invention nodal frequency synchronous (estimate and offset).

Embodiment

Below in conjunction with accompanying drawing, the present invention will be further described, but embodiments of the present invention are not limited to this.

One, cooperation communication system model

As shown in Figure 1, native system belongs to many relay cooperatives wireless transmitting system, is made up of a source node, multiple via node and a destination node.Each node configuration individual antenna, all multi-carrier modulation/demodulation modes of the OFDM (CP-OFDM) of employing with Cyclic Prefix.

In this system, source node and destination node communicate, and its communication link is that source node is to destination node link, conventionally also referred to as tie link (Direct Link, is abbreviated as DL).Around source node and destination node, there are multiple via nodes, for cooperation transmission.In the time that the channel status of tie link is better, source node can be realized and being communicated by letter by tie link with destination node, without relay node cooperation; In the time that the channel status of tie link is poor, via node can participate in cooperation, and to forwarding the information from source node to destination node, implementation space diversity gain, improves communication quality.This system adopts amplification forwarding (Amplify and Forward, AF) and decoding to forward (Decode and Forward, DF) two kinds of conventional relay cooperative modes.

Two, system frame structure

Frame structure comprises prefix, training sequence and three parts of data sequence: prefix part detects and sign synchronization for frame; Training sequence is made up of two parts, is respectively used to Frequency Synchronization and channel estimating; Data sequence, for transmitting useful information, pilot signal can be interted in centre, for track channel change.

1, the structure of prefix

In the prefix part for carrying out time synchronized, native system adopts [P1, P2]=[A, reverse (A)] structure, the estimation of this structure is than traditional based on the obvious peak point of having of auto-correlation second-order statistics and very steep slope, thereby estimated accuracy wants high.

2, for the structure of the training sequence of Frequency Estimation

In the training sequence part for Frequency Synchronization, native system adopts following structure:

It is NS fixed sequence really that source node adopts length as training sequence, by 2 identical parts composition.CP part is taken from the last L of s _cPlength part in order to ensure that under multipath interference channel environment training sequence is not subject to the interference of prefix part, the length L of CP part _cPshould be greater than the length L of multipath channel _h, meet L _cP>L _h.

The communication process of (1) three kind of transmission mode

In the digital communication system of point-to-point, as communicating by letter between base station of cellular system and certain handheld terminal, its communication process can be divided into digital end and analog end.Digital end completes the Digital Signal Processing task of base band, comprises chnnel coding/decoding, symbol-modulated/demodulation and other processing procedures of bit information; Analog end completes digital signal to the conversion of analog signal and whole processing procedures of analog signal, comprises the transmitting procedure of analog signal in wireless channel.

In the point-to-point digital communication system being illustrated in fig. 5 shown below, it is that transmitting terminal base-band digital is processed block diagram and receiving terminal base-band digital is processed block diagram that the digital end processing procedure of the digital end processing procedure of transmitting terminal and receiving terminal is distinguished abstract; By completing the transmission formed filter of digital signal to analog signal conversion, realize signal by low frequency to the carrier modulation of high frequency conversion, through physical channel, realize signal by high frequency to the carrier wave demodulation of low frequency conversion, to realize a series of procedural abstractions such as matched filter and sampler that analog signal to digital signal changes be the discrete multipath channel of Equivalent Base-Band; And then obtain the Equivalent Base-Band communication system of point-to-point digital communication system.(11) direct link transmission mode

Under direct link transmission mode, its communication process is traditional point-to-point (Point-to-Point) communication process.The Equivalent Base-Band communication system that therefore can draw the direct link transmission system consistent with Fig. 5, is illustrated in fig. 6 shown below.

The transmitting terminal base-band digital of source node is processed block diagram, as shown in Figure 7, mainly comprises the generation of prefix, training sequence and data sequence.Data sequence is made up of information sequence and pilot signal; The production process of information sequence comprises generation, cyclic redundancy check (CRC) coding (Cyclic Redundancy Check, CRC), chnnel coding, the symbol-modulated of information bit; Pilot signal is interted in the middle of information sequence, and through OFDM, modulation becomes the data sequence of time domain.Finally, prefix, training sequence and data sequence are delivered to transmission formed filter in succession.Cyclic redundancy check (CRC) coding object is whether the integrality of check bit data and conduct need one of criterion of relay node cooperation.

At destination node receiving terminal, as shown in Figure 8, carry out the digital signal sequences first elapsed time synchronization module of self-matching filter after sampling, complete frame and detect and sign synchronization; Realizing after sign synchronization, can calculate the initial sample position of training sequence and data sequence, and then extracting training sequence to complete the processing of Frequency Synchronization and channel estimating and data sequence.

The processing of data sequence comprises the processing of information sequence and pilot signal; For information sequence, after OFDM demodulation, first need to carry out the equilibrium of frequency domain channel, wherein channel parameter is provided by the channel estimation module based on training sequence and the tracking module based on pilot signal, then carry out symbol demodulation, modulation symbol is become to binary bit signal, finally enter channel decoding module and complete decoding, if any chnnel coding.Under static channel, channel parameter remains unchanged, and is provided and has been enough to channel equalization by the channel estimation module based on training sequence; If there is Frequency Estimation remainder error, also need to carry out the tracking of phase place; And moving under (time change) channel, channel parameter temporal evolution, the tracking of channel parameter is estimated to be provided by the tracking module based on pilot signal.

(12) tie link and single relay cooperative transmission pattern

Different from the point-to-point communication of direct transmission mode, under tie link and single relay cooperative transmission pattern, as shown in Figure 9, except tie link, also have the repeated link of " source node-via node-destination node " to participate in cooperation.The process of collaboration communication can be divided into cooperation stage one and cooperation stage 2 two processes.In the cooperation stage one, source node, to destination node and via node transmitted signal simultaneously, belongs to the broadcast communication of point-to-multipoint; In the cooperation stage two, source node and via node, simultaneously to destination node transmitted signal, belong to how point-to-point communication.

In the cooperation stage one, the broadcast communication of point-to-multipoint can be divided into multiple independently point-to-point communication processs.For source node, itself and destination node and via node can form respectively independently point-to-point digital communication system, therefore, it is consistent with the transmitting terminal base-band digital processing block diagram under tie link pattern that the transmitting terminal base-band digital of source node is processed block diagram, as shown in figure 10:

Under tie link and single relay cooperative transmission pattern, the main purpose of single via node is that the digital signal from source node is carried out to Alamouti coding, to complete cooperation transmission, for receiving, the signal of destination node brings space diversity gain, improve the signal reception of destination node.Via node can adopt amplification forwarding (AF) and decoding to forward (DF) two kinds of different trunk protocols.Under different trunk protocols, the signal processing difference of via node, therefore the implementation of the coding of the Alamouti under two kinds of protocol modes is also different.

Under amplification forwarding (AF) agreement, the base-band digital processing procedure of via node comprises reception and sends two links, as shown in figure 11, receiving link, via node is synchronous, Frequency Synchronization of deadline and channel estimating successively, channel estimating delivery channel estimates of parameters, the latter is for calculating the required judgement amount of relay selection.After selected participation cooperation, via node first carries out OFDM demodulation (comprise and remove CP and FFT variation) to the data sequence of time domain, draw the data sequence of frequency domain, then complete Alamouti coding (comprising information sequence and pilot signal) according to the Alamouti coded system of ofdm system, carry out OFDM and modulate again (comprising that IFFT changes and add new CP), and pass through together with prefix with training sequence frequency is compensating module againrealize with source node transmission carrier frequency and aliging, finally deliver to transmission formed filter.

Forward under (DF) cooperation mode in decoding, the base-band digital processing procedure of via node also comprises reception and sends two links, as shown in figure 12, receiving link, via node is synchronous, Frequency Synchronization of deadline and channel estimating successively, channel estimating delivery channel estimates of parameters, the latter is for calculating the required judgement amount of relay selection.Different from amplification forwarding (AF) cooperation mode, DF via node also needs the information sequence in data sequence to carry out the channel equalization of frequency, symbol demodulation and channel decoding, and the bit sequence of decoding output carries out cyclic redundancy check (CRC), with the integrality of check bit data, and inspection correctness is informed to relay selection module.For time varying channel, the pilot signal that also needs to shift to an earlier date in data sequence is carried out the tracking estimation of source node to via node channel parameter.After selected participation cooperation, via node re-starts chnnel coding and follow-up symbol-modulated to the bit sequence of channel decoding output, draws the information sequence of frequency domain, and send into Alamouti coding module together with pilot signal; Then carry out OFDM modulation and draw the data sequence of time domain, and deliver to frequency compensating module again with training sequence together with prefix, realize with source node transmission carrier frequency and aliging, finally deliver to transmission formed filter.

In the cooperation stage one, following Figure 13, destination node receiving terminal receives only the signal from source node, consistent with under tie link transmission mode of its base-band digital processing procedure, see Fig. 8, the output of channel estimation module and cyclic redundancy check (CRC) module is used for carrying out relay selection.

In the destination node in cooperation stage two, destination node receives the superposed signal from source node and via node simultaneously, the object of its base-band digital processing procedure is to carry out Alamouti decoding and channel decoding, and its processing procedure forwards under (DF) agreement all the same at amplification forwarding (AF) with decoding.As shown in figure 14, destination node is synchronous, Frequency Synchronization of deadline and channel estimating successively, the channel parameter estimation value of channel estimating output source node to destination node and via node to destination node, for the Alamouti decoding of follow-up data sequence information sequence.For time varying channel, the pilot signal that also needs to extract in data sequence is carried out the tracking estimation of Alamouti decoding desired parameters.

In native system, via node and destination node all need to carry out Frequency Synchronization.Under direct link transmission mode, source node belongs to the Frequency Synchronization problem of point-to-point digital communication system to the Frequency Synchronization problem between destination node; In the cooperation stage one under collaboration mode, via node and destination node all receive only the signal from source node, and its Frequency Synchronization problem also belongs to the Frequency Synchronization problem of point-to-point digital communication system; In the cooperation stage two, destination node receives from two cooperative nodes (source node and via nodes simultaneously, or two via nodes) superposed signal, because two cooperative nodes in native system all adopt the training sequence (for Frequency Estimation part) of identical structure, therefore the stack of two paths of signals can be regarded as to the signal of prefix through an equivalent multipath channel, therefore its Frequency Synchronization problem also belongs to the Frequency Synchronization problem of point-to-point digital communication system.The via node in cooperation stage one and signal system model and the frequency synchronization algorithm of the destination node in cooperation stage two are described below.

Above-described embodiments of the present invention, do not form limiting the scope of the present invention.Any amendment of having done within spiritual principles of the present invention, be equal to and replace and improvement etc., within all should being included in claim protection range of the present invention.

Claims (5)

1. for a cooperation communication system medium frequency synchronous method, this communication system belongs to many relay cooperatives wireless transmitting system, is made up of source node, via node and destination node; Each node configuration individual antenna, all multi-carrier modulation/demodulation modes of the OFDM CP-OFDM of employing with Cyclic Prefix; Frame structure comprises prefix, training sequence and three parts of data sequence;

It is characterized in that, Frequency Synchronization comprises via node Frequency Synchronization and destination node Frequency Synchronization;

The process of described via node Frequency Synchronization is: while there is frequency error, realizing after sign synchronization, after the OFDM window that the length of training sequence is N removes CP, interior reception signal is

Training sequence is carried out to Frequency Synchronization and comprises frequency error estimation and offset frequency error:

Wherein the frequency error of training sequence estimates it is to utilize the repetitive structure that removes the training sequence after CP, and repetitive structure comprises s ₁, s ₂, s ₁=s ₂;

The observed value of OFDM window is utilize the method for estimation based on auto-correlation second-order statistics to carry out frequency error estimation; Obtain the carrier frequency error Δ f of source node to via node link _srestimated value table be shown

The offset frequency error of training sequence is to utilize training sequence to draw frequency error estimated value afterwards, via node need to carry out frequency compensation to the time-domain signal receiving, the time-domain signal after compensation suc as formula wherein T represents sampling period, and n represents sampling time, n=1 ..., N; Time-domain signal after compensation is for the follow-up channel estimating based on training sequence and the processing to data sequence;

Realizing after Alamouti coding, via node is modulated to time-domain signal the carrier wave identical with source node transmission frequencysend again, compensate again to realize frequency; The time-domain signal that is via node also needs to be multiplied by the carrier frequency error Δ f of the estimated source node arriving to via node link _sr;

Described destination node Frequency Synchronization comprises frequency error estimation and offset frequency error.

2. according to claim 1ly it is characterized in that for cooperation communication system medium frequency synchronous method, the detailed process of described via node Frequency Synchronization is:

While there is frequency error, realizing after sign synchronization, after the OFDM window that the length of training sequence is N removes CP, interior reception signal is

$r_n^{\mathrm{sr}}=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}\mathrm{nT}}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}{s}_{n-l}+z_n^{\mathrm{sr}},n=1,...,N$

Wherein the l footpath channel parameter to via node is saved in expression source, l=0 ..., L _sr-1; s _nrepresent the transmitted signal of time domain, corresponding is training sequence part here, and s _-l=s _n-l; Δ f _sr=f _s-f _rrepresent the carrier frequency error of source node to via node link, f _sand f _rthe carrier frequency that represents respectively source node and via node, T represents sampling period;

Training sequence is carried out to Frequency Synchronization and comprises frequency error estimation and offset frequency error:

Wherein the frequency error of training sequence estimates it is to utilize the repetitive structure that removes the training sequence after CP, and repetitive structure comprises s ₁, s ₂, s ₁=s ₂;

The observed value of OFDM window is utilize the method for estimation based on auto-correlation second-order statistics to carry out frequency error estimation;

$\begin{array}{c}{r}_1^{\mathrm{sr}}\left(n\right)=r^{\mathrm{sr}}\left(n\right)=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}\mathrm{nT}}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}s(n-l)+z_n^{\mathrm{sr}}\\ =e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}\mathrm{nT}}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}{s}_1(n-l)+z_n^{\mathrm{sr}},n=1,...,\frac{N_S}{2}\end{array}$

$\begin{array}{c}{r}_2^{\mathrm{sr}}\left(n\right)=r^{\mathrm{sr}}(\frac{N_S}{2}+n)=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}(\frac{N_S}{2}+n)T}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}s((\frac{N_S}{2}+n)-l)+z_{(\frac{N_S}{2}+n)}^{\mathrm{sr}}\\ =e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}\frac{N_S}{2}T}\left(e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sr}}\mathrm{nT}}\underset{0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}{s}_2(n-l)\right)+z_{(\frac{N_S}{2}+n)}^{\mathrm{sr}},n=1,...,\frac{N_S}{2}\end{array}$

Due to s ₁=s ₂, therefore can obtain

According to law of great number, be approximately white Gaussian noise, obtain frequency error Δ f _srestimated value table be shown;

$\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}=\frac{1}{\mathrm{\&pi;}{N}_{S}T}\arg \left\{{\left(r_1^{\mathrm{sr}}\right)}^H\left(r_2^{\mathrm{sr}}\right)\right\}.$

N _st represents the size of OFDM window, under T mono-stable condition, and N _slonger, OFDM window is just larger, and the precision of estimation is just high;

The offset frequency error of training sequence is to utilize training sequence to draw frequency error estimated value afterwards, via node need to carry out frequency compensation to the time-domain signal receiving, the time-domain signal after compensation suc as formula wherein T represents sampling period, and n represents sampling time, n=1 ..., N; Time-domain signal after compensation is for the follow-up channel estimating based on training sequence and the processing to data sequence;

$\begin{array}{c}{y}_n^{\mathrm{sr}}=e^{-j2\mathrm{\&pi;\&Delta;}{\hat{f}}_{\mathrm{sr}}\mathrm{nT}}{r}_n^{\mathrm{sr}}\\ =e^{j2\mathrm{\&pi;}(\mathrm{\&Delta;}{f}_{\mathrm{sr}}-\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}})\mathrm{nT}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}{s}_{n-l}+e^{-j2\mathrm{\&pi;\&Delta;}{\hat{f}}_{\mathrm{sr}}\mathrm{nT}}{z}_n^{\mathrm{sr}}}\\ =e^{j2\mathrm{\&pi;}(\mathrm{\&Delta;}{f}_{\mathrm{sr}}-\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}})\mathrm{nT}}\underset{l=0}{\overset{L_{\mathrm{sr}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sr}}{s}_{n-l}+{\hat{z}}_n^{\mathrm{sr}}\end{array}$

Realizing after Alamouti coding, via node is modulated to time-domain signal the carrier wave identical with source node transmission frequencysend again, compensate again to realize frequency; The time-domain signal that is via node also needs to be multiplied by the frequency error Δ f between estimated via node and the source node arriving _sr, it is the symbol of n sampling time.

3. according to claim 2ly it is characterized in that for cooperation communication system medium frequency synchronous method, the detailed process of described destination node Frequency Synchronization is:

Under single or two relay cooperative transmission patterns, establish source node and via node and be respectively H to the frequency domain channel between destination node ^sdand H ^rd, destination node receives from the time-domain signal of source node and via node and is expressed as

$\begin{array}{c}{r}_n^d=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{rd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{\hat{s}}_{n-l}^r+z_n^d\\ =e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{rd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}\left(e^{+j2\mathrm{\&pi;\&Delta;}{\hat{f}}_{\mathrm{sr}}(n-l)T_s}{s}_{n-l}^r\right)+z_n^d\\ \&ap;e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;}(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}+\mathrm{\&Delta;}{f}_{\mathrm{rd}})n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{s}_{n-l}^r+z_n^d\end{array}$

Wherein Δ f _sd=f _s-f _dwith Δ f _rd=f _r-f _drepresent respectively source node and the via node carrier frequency error to destination node link, f _dfor the carrier frequency of destination node, due to estimated value, non-vanishing, therefore can obtain

$\begin{array}{c}\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}+\mathrm{\&Delta;}{f}_{\mathrm{rd}}\\ =(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+\mathrm{\&Delta;}{f}_{\mathrm{sr}}+\mathrm{\&Delta;}{f}_{\mathrm{rd}}\\ =(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+(f_s-f_r)+(f_r-f_d)\\ =(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+f_s-f_d\\ =(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+\mathrm{\&Delta;}{f}_{\mathrm{sd}}\end{array}$

Further try to achieve

$\begin{array}{c}{r}_n^d=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;}[(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+\mathrm{\&Delta;}{f}_{\mathrm{sd}}]n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{s}_{n-l}^r+z_n^d\\ =e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}(\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;}(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{s}_{n-l}^r)+z_n^d\end{array}$

Although $\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}}\&NotEqual;0,$ But due to $\mathrm{\&Delta;}{f}_{\mathrm{sd}}>>\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}},$ Therefore $\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}}$ Ignore, and then can obtain

$\begin{array}{c}{r}_n^d=e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+e^{j2\mathrm{\&pi;}[(\mathrm{\&Delta;}{\hat{f}}_{\mathrm{sr}}-\mathrm{\&Delta;}{f}_{\mathrm{sr}})+\mathrm{\&Delta;}{f}_{\mathrm{sd}}]n{T}_s}\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{s}_{n-l}^r+z_n^d\\ =e^{j2\mathrm{\&pi;\&Delta;}{f}_{\mathrm{sd}}n{T}_s}(\underset{l=0}{\overset{L_{\mathrm{sd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{sd}}{s}_{n-l}+\underset{l=0}{\overset{L_{\mathrm{rd}}-1}{\mathrm{\&Sigma;}}}{h}_l^{\mathrm{rd}}{s}_{n-l}^r)+z_n^d\end{array}$

For the signal of the training sequence part for Frequency Estimation, meet therefore

Its frequency error is estimated Δ f _sdestimated value table be shown wherein with the time domain that is respectively corresponding training sequence part repetitive substructure receives signal; Estimate Δ f according to frequency error _sdestimated value the time-domain signal receiving is carried out to offset frequency error.

4. according to claim 1ly it is characterized in that for cooperation communication system medium frequency synchronous method, the prefix part of described communication system adopts [P1, P2]=[A, reverse (A)] structure.

5. according to claim 1ly it is characterized in that for cooperation communication system medium frequency synchronous method, it is N that described source node adopts length _sreally fixed sequence as training sequence, by 2 identical parts composition; CP part is taken from the last L of s _cPlength part in order to ensure that under multipath interference channel environment training sequence is not subject to the interference of prefix part, the length L of CP part _cPbe greater than the length L of multipath channel _h, meet L _cP>L _h.