CN103457899A - Method for sensing OFDM frame synchronization in compressed mode - Google Patents

Abstract

The invention discloses a method for sensing OFDM frame synchronization in a compressed mode. The method comprises the steps that a compressed sensing matrix A is constructed; signal frames transmitted by a transmitting end are received by a receiving end, and a received signal vector r is formed; related operation processing is achieved through the compressed sensing matrix A and the received signal vector r to obtain a frame synchronization point d in a compressed domain of the signal frames; a frame synchronization point d0 in an uncompressed domain of the signal frames is determined according to the frame synchronization point d in the compressed domain; the frame synchronization point d0 in the uncompressed domain is used for carrying out the frame synchronization between the receiving end and the transmitting end. The method greatly saves processor resources.

Description

A kind of compressed sensing OFDM frame synchornization method

Technical field

The present invention relates to the frame synchronizing in a kind of TDS-OFDM communication system, be specifically related to a kind of compressed sensing OFDM frame synchornization method.

Background technology

OFDM (Orthogonal Frequency-Division Multiplexing, OFDM) technology has excellent anti-multipath interference performance, thereby is widely used cellular communication, in the wireless communication systems such as digital broadcast television.Filling mode according to OFDM symbol protection interval; mainly contain at present the ofdm system of three types: based on Cyclic Prefix (Cyclic Prefix; CP) CP-OFDM system; zero padding (Zero Padding in the protection interval; ZP) fill the TDS-OFDM system of the Domain Synchronous (Time Domain Synchronous, TDS) of pseudo random sequence in ZP-OFDM system and protection interval.In this three classes ofdm system, the reception & disposal algorithm complexity of ZP-OFDM system.With respect to the CP-OFDM system, the TDS-OFDM system does not need extra pilot signal, can increase the channel capacity of system, thereby be adopted by China Digital TV ground multimedia broadcast (DTMB, Digital Terrestrial Multimedia Broadcast) standard.

Frame synchronization is the requisite key link of TDS-OFDM communication system and top priority, and generally, only, after completing frame synchronization, follow-up processing (as channel estimating, processing such as information detections) just can be carried out.In the TDS-OFDM system, known its transmitting terminal of receiving terminal is filled pseudo random sequence (or being called training sequence) in the protection interval.Therefore, when conducting frame is synchronous, traditional TDS-OFDM system frame synchronizing method utilizes known pseudo random sequence (or being called training sequence) and reception signal to carry out related operation (" related operation " is a kind of method that concrete signal is processed), and finds the propagation delay of the arrival reception antenna that transmits by certain criterion.Although traditional TDS-OFDM frame synchornization method has certain feasibility, the related operation of frame synchronizing process is processed and has been taken more processor resource expense.

The compressive sensing theory occurred is in recent years pointed out, as long as signal is compressible or is sparse at certain transform domain, so just can project on lower dimensional space with a high dimensional signal that with the incoherent observing matrix of transform-based, will convert gained, thereby realize that the compression of signal processes.Then, just can from a small amount of information compression, with high probability, reconstruct original signal by solving an optimization problem.Numerous research shows, can prove so high dimensional signal to the inclusive projection of lower dimensional space the enough information of reconstruction signal.The method is widely used in the aspects such as radio communication, radar and remote sensing image processing.

When the TDS-OFDM system is carried out frame synchronization process, the output signal of processing due to related operation is sparse, and utilizing the compressed sensing technology to carry out frame synchronization process becomes possibility.Therefore, for reducing the resource overhead of TDS-OFDM system in frame synchronizing process, the present invention proposes a kind of compressed sensing OFDM frame synchornization method.

Summary of the invention

Main purpose of the present invention is, a kind of novel compressed sensing OFDM frame synchornization method is provided, technical problem to be solved is based on the compressed sensing technology, related operation number of processes when put forward the methods greatly reduces frame synchronization, thereby reduce the processor resource expense of TDS-OFDM system in frame synchronizing process, thereby more be suitable for practicality.

The object of the invention to solve the technical problems realizes by the following technical solutions.A kind of compressed sensing OFDM frame synchornization method proposed according to the present invention, for time-domain synchronous orthogonal frequency-division multiplexing system, comprising: structure compressed sensing matrix A; Receiving terminal receives the signal frame of transmitting terminal emission, and forms reception signal phasor r; Utilize described compressed sensing matrix A and described reception signal phasor r to complete related operation and process, obtain the frame synchronization point d in the compression domain of described signal frame; According to the synchronous point d in described compression domain, determine the frame synchronization point d in the uncompressed domain in described signal frame ₀; Use the frame synchronization point d in described uncompressed domain ₀, carry out the frame synchronization between described receiving terminal and described transmitting terminal.

Preferably, aforesaid compressed sensing OFDM frame synchornization method, the step of described structure compressed sensing matrix A comprises: according to the upper limit in the distinguishable path of channel between described transmitting terminal and described receiving terminal, set degree of rarefication K; Obtain known training sequence length L, and the length N of obtaining described signal frame, and get M=N-L+1, and according to described training sequence

the correlation matrix of structure M * N

the observing matrix Φ of structure K * M; According to described correlation matrix Ψ and described observing matrix Φ, construct described compressed sensing matrix A=Φ Ψ.

Preferably, aforesaid compressed sensing OFDM frame synchornization method, the step of the observing matrix Φ of described structure K * M comprises: get

if

for integer, get described observing matrix Φ and be

otherwise, get

wherein,

the arithmetic operation that means to round up, get described observing matrix Φ and be

Preferably, aforesaid compressed sensing OFDM frame synchornization method, described receiving terminal receives the signal frame of transmitting terminal emission, and the step of formation reception signal phasor r comprises: described receiving terminal receives N signal frame from described transmitting terminal, and forms the described reception signal phasor of N * 1

Preferably, aforesaid compressed sensing OFDM frame synchornization method, describedly utilize described compressed sensing matrix A and described reception signal phasor r to complete related operation to process, the step that obtains the frame synchronization point d in the compression domain of described signal frame comprises: utilize described compressed sensing matrix A and the described reception signal phasor r processing that carries out related calculation to be gathered

get square formation compression domain inspected number set of each yuan of prime modulus in set y

search for described compression domain inspected number set y _absintermediate value is greater than the first default thresholding T _{h, CS}the minimum index value as the frame synchronization point d in described compression domain.

Preferably, aforesaid compressed sensing OFDM frame synchornization method, described according to the synchronous point d in described compression domain, determine the frame synchronization point d in the uncompressed domain in described signal frame ₀step comprise: according to the frame synchronization point d of described compression domain, construct the indexed set of described uncompressed domain $d=\{\mathrm{dK}+1,\mathrm{dK}+2,\·\·\·,\min ((d+1)K,N)\};$ Extract the row of described indexed set d indication from described correlation matrix Ψ, form the submatrix Ψ of described correlation matrix _d; Utilize described submatrix Ψ _dcomplete the related operation processing with described signal reception vector r and obtain gathering y _d=Ψ _dr, get set y _dsquare formation uncompressed domain inspected number set y of each yuan of prime modulus _{d, abs}; At described uncompressed domain inspected number set y _{d, abs}in, search is greater than the second default thresholding T _hthe minimum index value as described uncompressed domain frame synchronization point d ₀.

Preferably, aforesaid compressed sensing OFDM frame synchornization method, the step of described structure compressed sensing matrix A also comprises: at described receiving terminal, compressed sensing matrix stores zone is set, and described compressed sensing matrix A is stored in to described compressed sensing matrix stores zone; Described described compressed sensing matrix A and the described reception signal phasor r of utilizing completes the related operation processing, the step that obtains the frame synchronization point d in the compression domain of described signal frame also comprises: from described compressed sensing matrix stores zone, extract described compressed sensing matrix A.

By technique scheme, compressed sensing OFDM frame synchornization method of the present invention at least has following advantages:

1) the compressed sensing matrix A was constructed in advance before the frame synchronization process process, without real-time structure.Thereby processing time and the processor that can not take in TDS-OFDM system communication process are processed resource.

2) frame synchronizing process has utilized the compressed sensing technology to be processed, the related operation number of processes while greatly reducing frame synchronization, thus reduce the processor resource expense of TDS-OFDM system in frame synchronizing process.

Above-mentioned explanation is only the general introduction of technical solution of the present invention, in order to better understand technological means of the present invention, and can be implemented according to the content of specification, below with preferred embodiment of the present invention and coordinate accompanying drawing to be described in detail as follows.

The accompanying drawing explanation

Fig. 1 is the signal frame form schematic diagram of TDS-OFDM system;

Fig. 2 is the structure flow chart of the compressed sensing matrix in compressed sensing OFDM frame synchornization method according to an embodiment of the invention;

Fig. 3 is the schematic flow sheet of compressed sensing OFDM frame synchornization method according to an embodiment of the invention;

Fig. 4 is the flow chart of the definite uncompressed domain frame synchronization point in compressed sensing OFDM frame synchornization method according to an embodiment of the invention.

Embodiment

Reach for further setting forth the present invention technological means and the effect that predetermined goal of the invention is taked, below in conjunction with accompanying drawing and preferred embodiment, its embodiment, structure, feature and effect thereof that foundation the present invention is proposed, be described in detail as follows.In following explanation, the not necessarily same embodiment that different " embodiment " or " embodiment " refer to.In addition, special characteristic, structure or the characteristics in one or more embodiment can be by any suitable form combination.

In one embodiment of the present of invention, the signal frame form schematic diagram of TDS-OFDM system as shown in Figure 1.When conducting frame is synchronous, adopts based on training sequence (protection is filled pseudo random sequence in interval) and realize, its training sequence comes from frame head.

The receiving terminal reception antenna receives the Frame of transmitting terminal emission, and the length of establishing training sequence is L, that is to say L sampled point, and the reception signal length is N.Here, N sampled point should be abundant, to guarantee to receive in signal the training sequence that includes emission, and usually get N and be the training sequence length L 2 times, i.e. N=2L, or surpass 2L.

Before the frame synchronization process process, construct in advance the compressed sensing matrix A in the present embodiment and be stored in the perception matrix stores zone of appointment on receiving terminal, thereby the processing time and the processor that do not take in the practical communication process are processed resource.As shown in Figure 2, the construction process of compressed sensing matrix A is as follows:

Step 01, according to wireless channel engineering experience data message, set degree of rarefication K.For example, when signal bandwidth is 8MHz, the distinguishable multipath number of the maximum of communicating by letter with suburban environment in city is 10～20.When signal bandwidth is 20MHz, the distinguishable multipath number of the maximum of communicating by letter with suburban environment in city is 30～40.For digital TV ground multimedia broadcasting (DTMB, Digital Terrestrial Multimedia Broadcast), its transmitted signal bandwidth is 8MHz, and degree of rarefication K=20 can be set.Get M=N-L+1.

Step 02, utilize known training sequence

the correlation matrix Ψ of structure M * N:

Example, establish training sequence for [+1-1+1] ^tbe L=3, get N=8, M=N-L+1=6 is arranged, correlation matrix Ψ is:

$\mathrm{\Ψ}=\left(\begin{array}{cccccccc}+1& -1& +1& 0& 0& 0& 0& 0\\ 0& +1& -1& +1& 0& 0& 0& 0\\ 0& 0& +1& -1& +1& 0& 0& 0\\ 0& 0& 0& +1& -1& +1& 0& 0\\ 0& 0& 0& 0& +1& -1& +1& 0\\ 0& 0& 0& 0& 0& +1& -1& +1\end{array}\right).$

Step 03, get

if

for integer, the observing matrix Φ of K * M can be taken as:

proceed to step 05, otherwise,

Step 04, get

wherein,

mean to round up arithmetic operation.The observing matrix Φ of K * M is

Step 05, correlation matrix Ψ and observing matrix Φ according to structure, construct compressed sensing matrix A=Φ Ψ, and the perception matrix A be stored in to designated storage area, finishes the structure flow process of compressed sensing matrix A.

Below specifically describe the frame synchronization process process, as shown in Figure 3.

Step 1, the receiving terminal reception antenna receives the signal frame of transmitting terminal emission, and the length that receives signal frame is N (being N sampled point), forms the reception signal phasor of N * 1 wherein, subscript T means matrix transpose operation.

Step 2, from compressed sensing matrix stores zone, extract the compressed sensing matrix A.

Step 3, the related operation that utilizes perception matrix A and the reception signal phasor r received to do compression domain is processed:

get square formation compression domain inspected number set y of each yuan of prime modulus of set y _abs, $y_{\mathrm{abs}}=\{{\left|{\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="HDA0000373506380000012.png,HDA0000373506380000021.png"\; state="\{\{state\}\}">y</figure-callout>}}_1\right|}^2,{\left|{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HDA0000373506380000021.png"\; state="\{\{state\}\}">y</figure-callout>}}_2\right|}^2,\&CenterDot;\&CenterDot;\&CenterDot;,{\left|y_k\right|}^2\}.$

It will be appreciated by those skilled in the art that described inspected number selected " mould square ", also can select other modes, as get the mode of the mould of each element, technical scheme of the present invention is not produced to restriction.

Step 4, at compression domain inspected number set y _absin, search is greater than predetermined compression domain threshold value T _{h, CS}minimum index value d (seeking the frame synchronization point of compression domain).

Example, suppose K=6, $y_{\mathrm{bas}}=\{{\left|{\mathrm{<figure-callout\; id="0"\; label="y"\; filenames="HDA0000373506380000012.png"\; state="\{\{state\}\}">y</figure-callout>}}_0\right|}^2,|{{\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="HDA0000373506380000012.png,HDA0000373506380000021.png"\; state="\{\{state\}\}">y</figure-callout>}}_1|}^2,{\left|{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HDA0000373506380000021.png"\; state="\{\{state\}\}">y</figure-callout>}}_2\right|}^2,{\left|{\mathrm{<figure-callout\; id="3"\; label="y"\; filenames="HDA0000373506380000021.png"\; state="\{\{state\}\}">y</figure-callout>}}_3\right|}^2,{\left|{\mathrm{<figure-callout\; id="4"\; label="y"\; filenames="HDA0000373506380000021.png"\; state="\{\{state\}\}">y</figure-callout>}}_4\right|}^2,{\left|{\mathrm{<figure-callout\; id="5"\; label="y"\; filenames="HDA0000373506380000021.png"\; state="\{\{state\}\}">y</figure-callout>}}_5\right|}^2\},$ If | y ₀| ²<T _{h, CS}, | y ₁| ²<T _{h, CS}, | y ₂| ²<T _{h, CS}, | y ₃| ²>=T _{h, CS}, | y ₄| ²<T _{h, CS}, | y ₅| ²>=T _{h, CS}, d=3.It will be appreciated by those skilled in the art that the index value value here selects since 0 counting, also can select, since 1 or other index values countings, technical scheme of the present invention not to be produced to restriction.

Described predetermined compression domain threshold value T _{h, CS}can set according to actual conditions and experience, for example, get P _fAfor predetermined false alarm probability, the predetermined compression domain threshold value T set according to invariable false alerting _{h, CS}according to following rule, arranged:

When during for integer, T _{h, CS}=-2QL σ ²ln (P _fA);

When

during for non-integer,

, have

Step 5, judge that whether the frame synchronization point search of compression domain is successful, if index value d does not exist, that is to say y _absin do not exist and be greater than threshold value T _{h, CS}value, return to step 1, wait for frame synchronization process process next time; Otherwise the index value d searched is the frame synchronization point of compression domain.

Step 6, check and search out uncompressed domain frame synchronization point d according to compression domain synchronous point d ₀(final frame synchronization point), thereby the handling process of end frame synchronizing process.

Check and determine uncompressed domain frame synchronization point d according to compression domain frame synchronization point d ₀the schematic flow sheet of (final frame synchronization point) as shown in Figure 4.Below with regard to final frame synchronization point (uncompressed domain frame synchronization point d ₀) definite process be described:

Step 61, according to compression domain frame synchronization point d, maps out uncompressed domain location index collection d:

d={dK+1,dK+2,…,min((d+1)K,N)}。

Step 62 is extracted the row of indexed set d indication from correlation matrix Ψ, forms the submatrix Ψ of correlation matrix _d.

Example, suppose that correlation matrix Ψ is $\mathrm{\&Psi;}=\left(\begin{array}{cccccccc}+1& -1& +1& 0& 0& 0& 0& 0\\ 0& +1& -1& +1& 0& 0& 0& 0\\ 0& 0& +1& -1& +1& 0& 0& 0\\ 0& 0& 0& +1& -1& +1& 0& 0\\ 0& 0& 0& 0& +1& -1& +1& 0\\ 0& 0& 0& 0& 0& +1& -1& +1\end{array}\right),$ Compression domain frame synchronization point d=1, degree of rarefication is K=2, N=8.Thereby indexed set d is d={3,4}, the submatrix Ψ of correlation matrix _dthe the 3rd and the 4th row element by Ψ forms, ${\mathrm{\&Psi;}}_d=\left(\begin{array}{cccccccc}0& 0& +1& -1& +1& 0& 0& 0\\ 0& 0& 0& +1& -1& +1& 0& 0\end{array}\right).$

Step 63, utilize submatrix Ψ _dcompleting related operation with receiving sequence r processes: y _d=Ψ _dr, get set y _dsquare formation uncompressed domain inspected number set y of each yuan of prime modulus _{d, abs}.

Step 63, at inspected number set y _{d, abs}in, search is greater than predetermined threshold T _hminimum index value d ₀, be uncompressed domain frame synchronization point (that is to say final frame synchronization point), finish final frame synchronization point (uncompressed domain frame synchronization point d ₀) definite process.

Described predetermined threshold T _hcan set according to actual conditions and experience, for example, get P _fAfor predetermined false alarm probability, the predetermined threshold T set according to invariable false alerting _hfor: T _h=-2L σ ²ln (P _fA).

Below just the present invention save on the whole related operation and process resource and do simple examples relatively:

Suppose that the TDS-OFDM system is the DTMB system, get the PN420 pattern, L=255, N=510 (not considering the leading and rear leading code of frame head), M=N-L+1=256.It is M=256 time that thereby traditional frame synchornization method needs the related operation number of times that sequence length is L=255.Get K=20, it is K=20 time that the present invention does in compression domain the related operation number of times that sequence length is L=255; Doing at uncompressed domain the related operation number of times that sequence length is L=255 is not more than

inferior.Therefore, the present invention shares the related operation number of times and is not more than 33 times, is far smaller than the related operation number of times 256 times that conventional method needs.

For another example, consider the PN945 pattern, L=511, N=1022 (not considering the leading and rear leading code of frame head), it is M=N-L+1=512 time that conventional method needs the related operation number of times.Get K=20, the present invention needs the related operation number of times to be not more than 46 times, is far smaller than the related operation number of times 512 times that conventional method needs.

According to above-mentioned concrete example, compressed sensing OFDM frame synchornization method of the present invention has been saved processor resource greatly.

The above, it is only preferred embodiment of the present invention, not the present invention is done to any pro forma restriction, although the present invention discloses as above with preferred embodiment, yet not in order to limit the present invention, any those skilled in the art, within not breaking away from the technical solution of the present invention scope, when the technology contents that can utilize above-mentioned announcement is made a little change or is modified to the equivalent embodiment of equivalent variations, in every case be the content that does not break away from technical solution of the present invention, any simple modification of above embodiment being done according to technical spirit of the present invention, equivalent variations and modification, all still belong in the scope of technical solution of the present invention.

Claims (7)

1. a compressed sensing OFDM frame synchornization method, is characterized in that, comprising:

Structure compressed sensing matrix A;

Receiving terminal receives the signal frame of transmitting terminal emission, and forms reception signal phasor r;

Utilize described compressed sensing matrix A and described reception signal phasor r to complete related operation and process, obtain the frame synchronization point d in the compression domain of described signal frame;

According to the synchronous point d in described compression domain, determine the frame synchronization point d in the uncompressed domain in described signal frame ₀;

Use the frame synchronization point d in described uncompressed domain ₀, carry out the frame synchronization between described receiving terminal and described transmitting terminal.

2. compressed sensing OFDM frame synchornization method according to claim 1, is characterized in that, the step of described structure compressed sensing matrix A comprises:

According to the upper limit in the distinguishable path of channel between described transmitting terminal and described receiving terminal, set degree of rarefication K;

Obtain known training sequence

length L, and the length N of obtaining described signal frame, and get M=N-L+1, and according to described training sequence the correlation matrix of structure M * N

The observing matrix Φ of structure K * M;

According to described correlation matrix Ψ and described observing matrix Φ, construct described compressed sensing matrix A=Φ Ψ.

3. compressed sensing OFDM frame synchornization method according to claim 2, is characterized in that, the step of the observing matrix Φ of described structure K * M comprises:

Get

if

for integer, get described observing matrix Φ and be otherwise, get

wherein,

the arithmetic operation that means to round up, get described observing matrix Φ and be

4. compressed sensing OFDM frame synchornization method according to claim 1, is characterized in that, described receiving terminal receives the signal frame of transmitting terminal emission, and the step of formation reception signal phasor r comprises:

Described receiving terminal receives N signal frame from described transmitting terminal, and forms the described reception signal phasor of N * 1 $r={[r_0,r_1,...,r_{N-1}]}^T.$

5. compressed sensing OFDM frame synchornization method according to claim 1, it is characterized in that, describedly utilize described compressed sensing matrix A and described reception signal phasor r to complete related operation to process, the step that obtains the frame synchronization point d in the compression domain of described signal frame comprises:

Utilizing described compressed sensing matrix A and described reception signal phasor r to complete the related operation processing is gathered

get square formation compression domain inspected number set of each yuan of prime modulus in set y $y_{\mathrm{abs}}=\{{\left|y_1\right|}^2,{\left|y_2\right|}^2,\&CenterDot;\&CenterDot;\&CenterDot;,{\left|y_k\right|}^2\};$

Search for described compression domain inspected number set y _absintermediate value is greater than the first default thresholding T _{h, CS}the minimum index value as the frame synchronization point d in described compression domain.

6. compressed sensing OFDM frame synchornization method according to claim 1, is characterized in that, described according to the synchronous point d in described compression domain, determines the frame synchronization point d in the uncompressed domain in described signal frame ₀step comprise:

According to the frame synchronization point d of described compression domain, construct the indexed set of described uncompressed domain $d=\{\mathrm{dK}+1,\mathrm{dK}+2,\&CenterDot;\&CenterDot;\&CenterDot;,\min ((d+1)K,N)\};$

Extract the row that described indexed set d indicates from described correlation matrix Ψ, form the submatrix Ψ of described correlation matrix _d;

Utilize described submatrix Ψ _dreceive vector r with described signal and complete the related operation processing, obtain gathering y _d=Ψ _dr, get set y _dsquare formation uncompressed domain inspected number set y of each yuan of prime modulus _{d, abs};

At described uncompressed domain inspected number set y _{d, abs}in, search is greater than the second default thresholding T _hthe minimum index value as described uncompressed domain frame synchronization point d ₀.

7. according to the described compressed sensing OFDM frame synchornization method of any one in claim 1 to 6, it is characterized in that, the step of described structure compressed sensing matrix A also comprises:

At described receiving terminal, compressed sensing matrix stores zone is set, and described compressed sensing matrix A is stored in to described compressed sensing matrix stores zone;

Describedly utilize described compressed sensing matrix A and described reception signal phasor r to complete related operation to process, the step that obtains the frame synchronization point d in the compression domain of described signal frame also comprises:

From described compressed sensing matrix stores zone, extract described compressed sensing matrix A.

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