CN107786296A - A kind of reconstructing method for GOLD sequences - Google Patents

Abstract

The invention belongs to blind estimate technical field, particularly relates to a kind of reconstructing method for GOLD sequences.The method of the present invention includes the DSSS signals received carrying out pre- blind despread, obtain the GOLD sequence spread spectrum codes in M cycle, M GOLD sequence is solved generator polynomial and counted respectively again and obtains final correct generator polynomial, check matrix and block code generator matrix are solved again, changed again by Walsh and solve initial state, so as to complete the reconstruct of GOLD sequences.The GOLD series finally obtained using reconstruct completes the blind despread of DSSS signals., can be consistent with despreading performance during cooperative communication so as to strengthen the performance of blind despread because reconstructing obtained GOLD sequences and the GOLD sequences that transmitting terminal is sent being completely the same.

Description

A Reconstruction Method for GOLD Sequences

technical field

The invention belongs to the technical field of blind estimation of DSSS (Direct-Sequence Spread Spectrum, Direct-Sequence Spread Spectrum), and in particular relates to a reconstruction method for GOLD sequences.

Background technique

Direct Sequence Spread Spectrum (DSSS) technology is one of the most commonly used communication technologies in modern communication systems. The feature of this technology is that the information code sequence is multiplied by the spread spectrum sequence at the sending end of the signal. Due to the high code rate of the spread spectrum code, the signal spectrum is expanded, which can reduce the power spectral density of the transmitted signal and has a low intercept probability. characteristic.

The DSSS communication system cooperates with the receiver to use the known spread spectrum sequence to despread the received signal cooperatively, which can suppress interference and recover the transmitted information. But for the non-cooperative receiver, it is necessary to process the received signal, extract the signal spreading code from it, and then use the estimated spreading code to despread to obtain the transmission information code sequence.

The code sequence used to spread the spectrum is a pseudo-random code, usually M sequence and GOLD sequence. And they have fixed generation rules. For the GOLD sequence, it is generated by adding two M sequences modulo two to obtain the required GOLD sequence. In the blind despreading of spread spectrum communication, the non-cooperative receiver usually estimates the spreading code from the received signal first. Due to the influence of noise or channel conditions, the estimated spreading code often contains wrong symbols. Therefore, in blind despreading, the estimated spreading code and the generation rule of spreading code can be used to reconstruct the same pseudo-random sequence as that of the sending end, so that the bit error rate of the information code sequence estimated by blind despreading can be further improved. Reduced, it can even make its performance comparable to that of cooperative communication. Therefore, the research on the reconstruction of DSSS signal spreading code is more meaningful.

Contents of the invention

The object of the present invention is to provide a fast reconstruction method of an error-containing GOLD sequence in order to overcome the above disadvantages.

The technical scheme of the present invention is, a kind of reconstruction method that is used for GOLD sequence, and this method is used for the direct sequence spread spectrum communication that spreading code is GOLD sequence, it is characterized in that, comprises the following steps:

a. It is set that the length and order of the GOLD sequence are known or estimated, and the GOLD sequence of M periods has been roughly estimated through blind despreading, then the BM algorithm is used to solve the generator polynomial for the GOLD sequence of M periods, That is, according to the BM algorithm for each segment of the GOLD sequence Solve the generator polynomial f ^(m) (x): can be written as And inductively by order N Where n=0,1,2,...,N-1; the specific method is:

a1, initialization state, make:

a2. Assumption has been obtained, and l ₀ ≤l ₁ ≤…≤l _n , where: Calculate the nth step difference d _n :

Where mod(A,2) represents the remainder of division by 2;

a3. According to the value of the nth step difference d _n , there are two situations as follows:

(1) When d _n =0, then:

(2) Etc. d _n =1, then:

①When: l ₀ =l ₁ =...=l _n =0, take:

②When there is k (0≤k<n), make: l _k <l _k+1 =l _k+2 =...=l _n , then:

a4, the last obtained is to generate the GOLD sequence The shortest linear shift register of , for The generator polynomial;

b. After obtaining the generator polynomials of the M GOLD codes, obtain the correct generator polynomials of the GOLD sequence c to be reconstructed through statistics;

c. Estimate the check matrix H of the GOLD sequence by using the obtained GOLD sequence, code length N and order r;

d. Estimate the block code generation matrix G by using the parity check matrix H, the code length N and the order r;

e. Known block code generation matrix G, order r and estimated GOLD sequence In the case of , use the Walsh transform to solve the initial state;

f. Using the solved initial state and generating polynomial and the known code length to reconstruct the GOLD sequence used by the transmitting end for spreading.

Finally, the reconstructed GOLD sequence is used to despread the received DSSS signal to obtain the information code sequence at the sending end, thus completing blind despreading.

The beneficial effect of the present invention is that, because the reconstructed GOLD sequence is completely consistent with the GOLD sequence sent by the sending end, the performance of blind despreading can be enhanced so that it can be consistent with the despreading performance during cooperative communication.

Description of drawings

Fig. 1 is a kind of specific implementation flow chart of the GOLD sequence method in the fast reconstruction DSSS communication of the present invention;

Fig. 2 is a performance diagram of the reconstruction algorithm in the specific implementation of the present invention.

Detailed ways

The present invention will be described below in conjunction with the accompanying drawings and embodiments.

Example

In this example, the signal-to-noise ratio is from -12dB to -8dB, and the order of the shift register that generates two m-sequences is 5, and their tap coefficients are: [0 0 1 0 1], [1 1 1 0 1] , the number of information codes is 100, and the number of Monte Carlo simulations is 10. Use the method shown in Figure 1 to reconstruct the GOLD sequence, compare the generated GOLD sequence with the estimated reconstructed GOLD sequence, and find out the number of different symbols between them. The resulting graph is shown in Figure 2. According to Fig. 2, it can be seen that the GOLD sequence constructed by the present invention is completely consistent with the GOLD sequence sent by the sending end.

Claims (1)

1. a kind of reconstruction method for GOLD sequence, the method is used for the direct sequence spread spectrum communication that spreading code is GOLD sequence, it is characterized in that, comprises the following steps: a. It is set that the length and order of the GOLD sequence are known or estimated, and the GOLD sequence of M periods has been roughly estimated through blind despreading, then the BM algorithm is used to solve the generator polynomial for the GOLD sequence of M periods, That is, according to the BM algorithm for each segment of the GOLD sequence Solve the generator polynomial f ^(m) (x): can be written as And inductively by order N Where n=0,1,2,...,N-1; the specific method is: a1, initialization state, make: a2. Assumption 0≤n<N, obtained, and l ₀ ≤l ₁ ≤…≤l _n , where: Calculate the nth step difference d _n : <mrow><msub><mi>d</mi><mi>n</mi></msub><mo>=</mo><mi>mod</mi><mrow><mo>(</mo><msubsup><mi>a</mi><mn>0</mn><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></msubsup><msub><mover><mi>c</mi><mo>~</mo></mover><mi>n</mi></msub><mo>+</mo><msubsup><mi>a</mi><mn>1</mn><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></msubsup><msub><mover><mi>c</mi><mo>~</mo></mover><mrow><mi>n</mi><mo>-</mo><mn>1</mn></mrow></msub><mo>+</mo><mn>...</mn><mo>+</mo><msubsup><mi>a</mi><msub><mi>l</mi><mi>n</mi></msub><mrow><mo>(</mo><mi>n</mi><mo>)</mo></mrow></msubsup><msub><mover><mi>c</mi><mo>~</mo></mover><mrow><mi>n</mi><mo>-</mo><msub><mi>l</mi><mi>n</mi></msub></mrow></msub><mo>,</mo><mn>2</mn><mo>)</mo></mrow></mrow> Where mod(A,2) represents the remainder of division by 2; a3. According to the value of the nth step difference d _n , there are two situations as follows: (1) When d _n =0, then: <mrow><msubsup><mi>f</mi><mrow><mi>n</mi><mo>+</mo><mn>1</mn></mrow><mrow><mo>(</mo><mi>m</mi><mo>)</mo></mrow></msubsup><mrow><mo>(</mo><mi>x</mi><mo>)</mo></mrow><mo>=</mo><msubsup><mi>f</mi><mi>n</mi><mrow><mo>(</mo><mi>m</mi><mo>)</mo></mrow></msubsup><mrow><mo>(</mo><mi>x</mi><mo>)</mo></mrow><mo>,</mo><msub><mi>l</mi><mrow><mi>n</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>=</mo><msub><mi>l</mi><mi>n</mi></msub></mrow> (2) Etc. d _n =1, then: ①When: l ₀ =l ₁ =...=l _n =0, take: <mrow><msubsup><mi>f</mi><mrow><mi>n</mi><mo>+</mo><mn>1</mn></mrow><mrow><mo>(</mo><mi>m</mi><mo>)</mo></mrow></msubsup><mrow><mo>(</mo><mi>x</mi><mo>)</mo></mrow><mo>=</mo><mn>1</mn><mo>+</mo><msup><mi>x</mi><mrow><mi>n</mi><mo>+</mo><mn>1</mn></mrow></msup><mo>,</mo><msub><mi>l</mi><mrow><mi>n</mi><mo>+</mo><mn>1</mn></mrow></msub><mo>=</mo><mi>n</mi><mo>+</mo><mn>1</mn></mrow> ②When there is k (0≤k<n), make: l _k <l _k+1 =l _k+2 =...=l _n , then: l _n+1 ＝max{l _n ,n+1-l _n } a4, the last obtained is to generate the GOLD sequence The shortest linear shift register of , for The generator polynomial; b. After obtaining the generator polynomials of the M GOLD codes, obtain the correct generator polynomials of the GOLD sequence c to be reconstructed through statistics; c. Estimate the check matrix H of the GOLD sequence by using the obtained GOLD sequence, code length N and order r; d. Estimate the block code generation matrix G by using the parity check matrix H, the code length N and the order r; e. Known block code generation matrix G, order r and estimated GOLD sequence In the case of , use the Walsh transform to solve the initial state; f. Using the solved initial state and generating polynomial and the known code length to reconstruct the GOLD sequence used by the transmitting end for spreading.