CN102098266B - Synchronization sequence construction method for multi-input multi-output orthogonal frequency division multiplexing (OFDM) system - Google Patents

Abstract

The invention relates to a synchronization sequence construction method for a multi-input multi-output orthogonal frequency division multiplexing (OFDM) system. The method comprises the following steps of: constructing a chu sequence s with the length of P, wherein P is less than N, (N)P is equal to 0, (g)P is a mold P operator, (N)P represents mold P operation related to N, and N is the length of a synchronization sequence; and circularly shifting the chu sequence s to obtain a shift sequence s (mu M), wherein g(g) is a circular shift operator, s (mu M) represents a vector obtained by circularly shifting the chu sequence s downwards by mu M bits, M is a shift parameter, mu represents an index of a transmitting antenna, M=floor(P/NI), floor() is an integral operator, floor(P/NI) represents rounding of P/NI, the parameter NI is designed as Nt<=NI<=P, and Nt represents the number of transmitting antennas. The synchronization sequence construction method is easy to generate and has a low system load.

Description

Multi-input multi-output orthogonal frequency division multiplexing system synchronous sequence construction method

Technical field

The present invention relates to a kind of synchronous sequence construction method can be applicable in multi-input multi-output orthogonal frequency division multiplexing system, belong to the simultaneous techniques field in mobile communication.

Background technology

Orthogonal frequency division multiplexi (OFDM, orthogonal frequency-division multiplexing) owing to having advantages of that high, the anti-frequency selective fading of spectrum efficiency and arrowband disturb, being highly suitable for radio communication channel transmission, is also the mainstream technology adopting in the current third generation mobile communication system.MIMO technique and OFDM technology combine, and larger spectrum efficiency, higher data rate can be provided; More and more nervous at current frequency spectrum resource, to the more and more higher situation of data rate requirement under, MIMO OFDM technology has more wide application prospect.

But adopt the system of OFDM technology to have a common shortcoming, very responsive to synchronous error especially carrier wave frequency deviation.Because the frequency spectrum between each subchannel of ofdm system covers mutually, this has just proposed strict requirement to the orthogonality between them.Yet, because wireless channel exists time variation, in transmitting procedure, there will be the frequency shift (FS) of wireless signal, the frequency departure for example, existing between Doppler frequency shift, or transmitter carrier frequency and receiver local oscillator.Only account for a fraction of carrier wave frequency deviation of subcarrier spacing and all can make the orthogonality between ofdm system subcarrier be destroyed, and then produce between subcarrier and disturb, thereby cause the remarkable decline of OFDM receiver performance.Therefore, for OFDM receiver, the estimation of carrier wave frequency deviation and the design of training sequence are vital, design suitable training sequence and can obviously improve estimated performance and suitably reduce algorithm complex.

Summary of the invention

Technical problem: the object of the invention is in multi-input multi-output orthogonal frequency division multiplexing system, a kind of synchronous sequence construction method that can effectively estimate frequency deviation is provided.The synchronous sequence construction method proposing generates simply, system load is low; Synchronizing sequence based on proposed can be realized the estimation of environment self-adaption low complex degree frequency deviation, and can realize multiple simplification frequency deviation algorithm for estimating; By design maximizing frequency offset estimation range, the optimization frequency deviation estimated performance of sequential parameter, and guarantee the consistency that frequency deviation is estimated.

Technical scheme: for solving the problems of the technologies described above, the invention provides a kind of synchronous sequence construction method of multi-input multi-output orthogonal frequency division multiplexing system, the method comprises the steps:

1) the chu sequence s that structure length is P, wherein, P < N, and (N) _p=0, (N) _pexpression is done mould P computing about N, and N is the length of synchronizing sequence;

2) chu sequence s is done to circulative shift operation, obtain shift sequence s ^{(μ M)}, wherein, ⁽⁾cyclic shift operator, s ^{(μ M)}expression circulates to moving down the resulting vector that obtains in μ M position to chu sequence s, and M is shift parameters, and μ represents the index of transmitting antenna, to round operator, representative is to P/N _iround design parameter N _imake N _t≤ N _i< P, N _trepresent the number of transmitting antenna;

3) to shift sequence s ^{(μ M)}do discrete Fourier transform (DFT), obtain frequency domain sequence wherein, F _pnormalization discrete Fourier transform (DFT) matrix, Q=N/P, and have Q > N _t, Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and P represents the length of chu sequence s, and N is the length of synchronizing sequence, N _trepresent transmitting antenna number;

4) to frequency domain sequence do matrix operation, obtain the training sequence corresponding to μ root transmitting antenna ${\tilde{t}}_{\mathrm{\&mu;}}={\mathrm{\&Theta;}}_{i_{\mathrm{\&mu;}}}{\tilde{s}}_{\mathrm{\&mu;}},$ Wherein, ${\mathrm{\&Theta;}}_{i_{\mathrm{\&mu;}}}=[e_N^{i_{\mathrm{\&mu;}}},e_N^{i_{\mathrm{\&mu;}}+Q},\&CenterDot;\&CenterDot;\&CenterDot;,e_N^{i_{\mathrm{\&mu;}}+(P-1)Q}],$ representation unit battle array I _ni _μindividual column vector, i _μexpression is corresponding to the index of first nonzero element of the training sequence of μ root transmitting antenna, μ represents the index of transmitting antenna, and Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and P represents the length of chu sequence s, N is the length of synchronizing sequence $0\&le;i_0<i_1<\&CenterDot;\&CenterDot;\&CenterDot;<i_{\mathrm{\&mu;}}<\&CenterDot;\&CenterDot;\&CenterDot;<i_{N_t-1}<Q.$

Obtain the training sequence corresponding to μ root transmitting antenna should satisfied condition be:

A) transmitting antenna energy even allocation criteria: frequency domain sequence n is the length of synchronizing sequence, N _trepresent transmitting antenna number, || || represent 2 norms of respective vectors;

B) frequency deviation is estimated conformance criteria: (N-N _tp)>=N _tp, P>=L, (1 _q-l) ^tl ^(q)> 0, wherein, L represents the maximum multipath time delay of channel, 1 _qcomplete 1 vector that represents Q * 1, the non-zero pilot vector that represents Q * 1; N is the length of synchronizing sequence, N _trepresent transmitting antenna number, P represents the length of chu sequence s, and Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and q representative is corresponding to the index of the zero pilot tone between adjacent non-zero pilot tone in the training sequence on transmitting antenna, ^trepresent transposition computing, i _μexpression is corresponding to the index of first nonzero element of the training sequence of μ root transmitting antenna, and μ represents the index of transmitting antenna;

C) integer frequency bias computed reliability criterion: $\max \underset{\mathrm{\&mu;}\&NotEqual;{\mathrm{\&mu;}}^{\&prime;}}{\min }\left\{{(i_{{\mathrm{\&mu;}}^{\&prime;}}-i_{\mathrm{\&mu;}})}_Q\right\},$ $\max \underset{1\&le;q\&le;Q-1}{\min }\left\{{(1_Q-l)}^T{l}^{\left(q\right)}\right\},$ I _μexpression is corresponding to the index of first nonzero element of the training sequence of μ root transmitting antenna, i _{μ '}expression is corresponding to the index of first nonzero element of the training sequence of the μ ' root transmitting antenna, ^trepresent transposition computing, q representative is corresponding to the index of the zero pilot tone between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna,

D) decimal frequency bias estimates to simplify criterion: N _rp > Q, P represents the length of chu sequence s, Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, N _rrepresent the number of reception antenna.

Beneficial effect: synchronous sequence construction method proposed by the invention, only need chu basis sequence to do circulative shift operation, discrete Fourier transform (DFT) and zero insertion operation, the training sequence that can generate corresponding each transmitting antenna, sequence constructing method is simple and system load is little.

Synchronous sequence construction method proposed by the invention, estimates conformance criteria based on its frequency deviation, can guarantee that the estimation of receiver frequency deviation is in enough large frequency deviation region all consistent, discernible;

Synchronous sequence construction method proposed by the invention, based on its integer frequency bias computed reliability criterion, can realize the simplification of integer frequency bias and calculate, especially, in friendly channel circumstance, by simple two-valued function computing, can realize the low complex degree of integer frequency bias estimation and realize;

Synchronous sequence construction method proposed by the invention, the cyclic attributes based on its decimal frequency bias estimation simplification criterion and institute's tectonic sequence, can adopt accomplished in many ways low complex degree high accuracy decimal frequency bias to estimate according to actual needs flexibly;

Synchronous sequence construction method proposed by the invention, is suitable for the communication system that centralized multiaerial system, distributed multi-antenna system, collaborative many relay systems, collaborative multi-user system etc. meet multiple-input and multiple-output essential characteristic.

Accompanying drawing explanation

Fig. 1 is multi-input multi-output orthogonal frequency division multiplexing system transmitter block diagram;

Fig. 2 is multi-input multi-output orthogonal frequency division multiplexing system synchronizing sequence structural representation;

Fig. 3 is the implementation structure schematic diagram of multi-input multi-output orthogonal frequency division multiplexing system synchronous sequence construction method.

Embodiment

Below in conjunction with accompanying drawing, the present invention will be further described.

The present invention is based on multi-I/O OFDM technology (OFDM, orthogonal frequency-division multiplexing) system, for this problem of the existing frequency shift (FS) of this system, puts forward.

The synchronous sequence construction method of multi-input multi-output orthogonal frequency division multiplexing system, the method comprises the steps:

1) the chu sequence s that structure length is P, wherein, P < N, and (N) _p=0, (N) _pexpression is done mould P computing about N, and N is the length of synchronizing sequence;

2) chu sequence s is done to circulative shift operation, obtain shift sequence s ^{(μ M)}, wherein, ⁽⁾cyclic shift operator, s ^{(μ M)}expression circulates to moving down the resulting vector that obtains in μ M position to chu sequence s, and M is shift parameters, and μ represents the index of transmitting antenna, to round operator, representative is to P/N _iround design parameter N _imake N _t≤ N _i< P, N _trepresent the number of transmitting antenna;

3) to shift sequence s ^{(μ M)}do discrete Fourier transform (DFT), obtain frequency domain sequence wherein, F _pnormalization discrete Fourier transform (DFT) matrix, Q=N/P, and have Q > N _t, Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and P represents the length of chu sequence s, and N is the length of synchronizing sequence, N _trepresent transmitting antenna number;

4) to frequency domain sequence do matrix operation, obtain the training sequence corresponding to μ root transmitting antenna ${\tilde{t}}_{\mathrm{\&mu;}}={\mathrm{\&Theta;}}_{i_{\mathrm{\&mu;}}}{\tilde{s}}_{\mathrm{\&mu;}},$ Wherein, ${\mathrm{\&Theta;}}_{i_{\mathrm{\&mu;}}}=[e_N^{i_{\mathrm{\&mu;}}},e_N^{i_{\mathrm{\&mu;}}+Q},\&CenterDot;\&CenterDot;\&CenterDot;,e_N^{i_{\mathrm{\&mu;}}+(P-1)Q}],$ representation unit battle array I _ni _μindividual column vector, i _μexpression is corresponding to the index of first nonzero element of the training sequence of μ root transmitting antenna, μ represents the index of transmitting antenna, and Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and P represents the length of chu sequence s, N is the length of synchronizing sequence $0\&le;i_0<i_1<\&CenterDot;\&CenterDot;\&CenterDot;<i_{\mathrm{\&mu;}}<\&CenterDot;\&CenterDot;\&CenterDot;<i_{N_t-1}<Q.$

A) transmitting antenna energy even allocation criteria: frequency domain sequence n is the length of synchronizing sequence, N _trepresent transmitting antenna number, || || represent 2 norms of respective vectors;

B) frequency deviation is estimated conformance criteria: (N-N _tp)>=N _tp, P>=L, (1 _q-l) ^tl ^(q)> 0, wherein, L represents the maximum multipath time delay of channel, 1 _qcomplete 1 vector that represents Q * 1, the non-zero pilot vector that represents Q * 1; N is the length of synchronizing sequence, N _trepresent transmitting antenna number, P represents the length of chu sequence s, and Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and q representative is corresponding to the index of the zero pilot tone between adjacent non-zero pilot tone in the training sequence on transmitting antenna, ^trepresent transposition computing, i _μexpression is corresponding to the index of first nonzero element of the training sequence of μ root transmitting antenna, and μ represents the index of transmitting antenna;

C) integer frequency bias computed reliability criterion: $\max \underset{\mathrm{\&mu;}\&NotEqual;{\mathrm{\&mu;}}^{\&prime;}}{\min }\left\{{(i_{{\mathrm{\&mu;}}^{\&prime;}}-i_{\mathrm{\&mu;}})}_Q\right\},$ $\max \underset{1\&le;q\&le;Q-1}{\min }\left\{{(1_Q-l)}^T{l}^{\left(q\right)}\right\},$ I _μexpression is corresponding to the index of first nonzero element of the training sequence of μ root transmitting antenna, i _{μ '}expression is corresponding to the index of first nonzero element of the training sequence of the μ ' root transmitting antenna, ^trepresent transposition computing, q representative is corresponding to the index of the zero pilot tone between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna,

D) decimal frequency bias estimates to simplify criterion: N _rp > Q, P represents the length of chu sequence s, Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, N _rrepresent the number of reception antenna.

The mimo OFDM systems that the present invention considers, its transmitting antenna and reception antenna number are made as respectively N _tand N _r.If the length of OFDM symbol or synchronous training sequence is N, make μ represent the index of transmitting antenna, 0≤μ < N _t.

Based on the above-mentioned definition about system and training sequence, the method for mimo OFDM systems synchronizing sequence structure of the present invention is:

1) the chu sequence s that structure length is P, wherein, P < N, and (N) _p=0, () _pit is mould P operator; Chu sequence is a kind of training sequence that wireless communication field extensively adopts, and corresponding Chinese literature is also all directly called chu sequence;

2) s is done to circulative shift operation, obtain sequence s ^{(μ M)}, wherein, ⁽⁾be cyclic shift operator, M is shift parameters, to round operator, design parameter N _imake N _t≤ N _i< P;

3) to s ^{(μ M)}do discrete Fourier transform (DFT), obtain sequence wherein, F _pnormalization discrete Fourier transform (DFT) matrix, Q=N/P, and have Q > N _t;

4) right do matrix operation, obtain the training sequence corresponding to μ root transmitting antenna ${\tilde{t}}_{\mathrm{\&mu;}}={\mathrm{\&Theta;}}_{i_{\mathrm{\&mu;}}}{\tilde{s}}_{\mathrm{\&mu;}},$ Wherein, ${\mathrm{\&Theta;}}_{i_{\mathrm{\&mu;}}}=[e_N^{i_{\mathrm{\&mu;}}},e_N^{i_{\mathrm{\&mu;}}+Q},\&CenterDot;\&CenterDot;\&CenterDot;,e_N^{i_{\mathrm{\&mu;}}+(P-1)Q}],$ representation unit battle array I _ni _μindividual column vector, i _μexpression is corresponding to the index of first nonzero element of the training sequence of μ root transmitting antenna, $0\&le;i_0<i_1<\&CenterDot;\&CenterDot;\&CenterDot;<i_{\mathrm{\&mu;}}<\&CenterDot;\&CenterDot;\&CenterDot;<i_{N_t-1}<Q.$

Its synchronizing sequence method for designing is as follows:

A) transmitting antenna energy even allocation criteria: frequency domain sequence n is the length of synchronizing sequence, N _trepresent transmitting antenna number, || || represent 2 norms of respective vectors;

B) frequency deviation is estimated conformance criteria: (N-N _tp)>=N _tp, P>=L, (1 _q-l) ^tl ^(q)> 0, wherein, L represents the maximum multipath time delay of channel, 1 _qcomplete 1 vector that represents Q * 1, the non-zero pilot vector that represents Q * 1; N is the length of synchronizing sequence, N _trepresent transmitting antenna number, P represents the length of chu sequence s, and Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and q representative is corresponding to the index of the zero pilot tone between adjacent non-zero pilot tone in the training sequence on transmitting antenna, ^trepresent transposition computing, i _μexpression is corresponding to the index of first nonzero element of the training sequence of μ root transmitting antenna, and μ represents the index of transmitting antenna;

C) integer frequency bias computed reliability criterion: $\max \underset{\mathrm{\&mu;}\&NotEqual;{\mathrm{\&mu;}}^{\&prime;}}{\min }\left\{{(i_{{\mathrm{\&mu;}}^{\&prime;}}-i_{\mathrm{\&mu;}})}_Q\right\},$ $\max \underset{1\&le;q\&le;Q-1}{\min }\left\{{(1_Q-l)}^T{l}^{\left(q\right)}\right\},$ I _μexpression is corresponding to the index of first nonzero element of the training sequence of μ root transmitting antenna, i _{μ '}expression is corresponding to the index of first nonzero element of the training sequence of the μ ' root transmitting antenna, ^trepresent transposition computing, q representative is corresponding to the index of the zero pilot tone between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna,

D) decimal frequency bias estimates to simplify criterion: N _rp > Q, P represents the length of chu sequence s, Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, N _rrepresent the number of reception antenna.

Building method based on above-mentioned synchronizing sequence, according to the implementation structure schematic diagram of the synchronous sequence construction method shown in the synchronizing sequence structural representation shown in Fig. 2 and Fig. 3, the specific implementation step that provides proposed synchronizing sequence is as follows:

1) the chu sequence s that structure length is P;

2) s is done to circulative shift operation, obtain sequence s ^{(μ M)};

3) to s ^{(μ M)}do discrete Fourier transform (DFT), obtain sequence

4) right do zero insertion computing, obtain the training sequence corresponding to μ root transmitting antenna

The above is only preferred implementation of the present utility model; be noted that for those skilled in the art; not departing under the prerequisite of the utility model principle, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (1)

1. a synchronous sequence construction method for multi-input multi-output orthogonal frequency division multiplexing system, is characterized in that: the method comprises the steps:

1) the chu sequence s that structure length is P, P < N, and (N) _p=0, (N) _pexpression is done mould P computing about N, and N is the length of synchronizing sequence;

2) chu sequence s is done to circulative shift operation, obtain shift sequence s ^{(μ M)}, wherein, ⁽⁾cyclic shift operator, s ^{(μ M)}expression circulates to moving down the resulting vector in μ M position to chu sequence s, and M is shift parameters, and μ is relevant to the index value of transmitting antenna, and μ+1 represents the index value of transmitting antenna, to round operator, representative is to P/N _iround design parameter N _imake N _t≤ N _i< P, N _trepresent the number of transmitting antenna;

3) to shift sequence s ^{(μ M)}do discrete Fourier transform (DFT), obtain frequency domain sequence wherein, F _pnormalization discrete Fourier transform (DFT) matrix, Q=N/P, and have Q > N _t, Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and P represents the length of chu sequence s, and N is the length of synchronizing sequence, N _trepresent transmitting antenna number;

4) to frequency domain sequence do matrix operation, obtain the training sequence corresponding to μ+1 transmitting antenna wherein, representation unit battle array I _ni _μindividual column vector, i _μexpression is corresponding to the index of first nonzero element of the training sequence of μ+1 transmitting antenna, μ is relevant to the index value of transmitting antenna, μ+1 represents the index value of transmitting antenna, Q representative is corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, P represents the length of chu sequence s, N is the length of synchronizing sequence n _trepresent transmitting antenna number;

According to above-mentioned synchronous sequence construction method, corresponding to the training sequence of μ+1 transmitting antenna should satisfied condition be:

A) transmitting antenna energy even allocation criteria: frequency domain sequence n is the length of synchronizing sequence, N _trepresent transmitting antenna number, || || ²2 norms that represent respective vectors;

B) frequency deviation is estimated conformance criteria: (N-N _tp)>=N _tp, P>=L, (1 _q-l) ^tl ^(q)> 0, wherein, L represents the maximum multipath time delay of channel, 1 _qcomplete 1 vector that represents Q * 1, the non-zero pilot vector that represents Q * 1; N is the length of synchronizing sequence, N _trepresent transmitting antenna number, P represents the length of chu sequence s, and Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, and q representative is corresponding to the index of the zero pilot tone between adjacent non-zero pilot tone in the training sequence on transmitting antenna, T represents transposition computing, i _μexpression is corresponding to the index of first nonzero element of the training sequence of μ+1 transmitting antenna, and μ is relevant to the index value of transmitting antenna, and μ+1 represents the index value of transmitting antenna;

C) integer frequency bias computed reliability criterion: i _μexpression is corresponding to the index of first nonzero element of the training sequence of μ+1 transmitting antenna, i _{μ '}expression is corresponding to the index of first nonzero element of the training sequence of μ '+1 transmitting antenna, T represents transposition computing, q representative is corresponding to the index of the zero pilot tone between adjacent non-zero pilot tone in the training sequence on transmitting antenna, Q representative is corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna

D) decimal frequency bias estimates to simplify criterion: N _rp > Q, P represents the length of chu sequence s, Q represents corresponding to the spacing between adjacent non-zero pilot tone in the training sequence on transmitting antenna, N _rrepresent the number of reception antenna.