阅读说明：本技术 直扩信号的调制、解调方法及终端设备 (Modulation and demodulation method of direct sequence spread spectrum signal and terminal equipment ) 是由 袁国刚 陈自力 高喜俊 王永川 李永科 马晓琳 闫云斌 贾红霞 苏立军 于 2019-10-31 设计创作，主要内容包括：本发明适用于通信技术领域,特别涉及一种直扩信号的调制方法,该方法包括：获取信息码序列和混沌扩频初始值；基于所述混沌扩频初始值,通过至少两级混沌映射为每个信息码生成预设位数的发送混沌扩频码；根据所述信息码序列和所述信息码序列中每个信息码对应的发送混沌扩频码生成待发送的直扩信号。采用上述方法调制的直扩信号,抗干扰能力强,保密性能高。(The invention is suitable for the technical field of communication, and particularly relates to a modulation method of a direct sequence spread spectrum signal, which comprises the following steps: acquiring an information code sequence and a chaotic spread spectrum initial value; generating a preset-bit-number transmission chaotic spread spectrum code for each information code through at least two-stage chaotic mapping based on the chaotic spread spectrum initial value; and generating a direct spread spectrum signal to be transmitted according to the information code sequence and the transmitted chaotic spread spectrum code corresponding to each information code in the information code sequence. The direct-sequence spread spectrum signal modulated by the method has strong anti-interference capability and high confidentiality.)

1. A method for modulating a direct sequence spread spectrum signal, comprising:

acquiring an information code sequence and a chaotic spread spectrum initial value;

generating a preset-bit-number transmission chaotic spread spectrum code for each information code through at least two-stage chaotic mapping based on the chaotic spread spectrum initial value;

and generating a direct spread spectrum signal to be transmitted according to the information code sequence and the transmitted chaotic spread spectrum code corresponding to each information code in the information code sequence.

2. The method for modulating the direct sequence spread spectrum signal according to claim 1, wherein the generating a transmission chaotic spread spectrum code of a preset number of bits for each information code by at least two-stage chaotic mapping based on the chaotic spread spectrum initial value comprises:

generating a first chaotic spread spectrum code corresponding to a first bit information code in the information code sequence based on the chaotic spread spectrum initial value and a first chaotic mapping, and generating a second chaotic spread spectrum code corresponding to the first bit information code in the information code sequence through a second chaotic mapping;

generating a first chaotic spread spectrum code corresponding to an ith bit information code in the information code sequence based on a first chaotic spread spectrum code corresponding to an ith-1 bit information code in the information code sequence and a first chaotic mapping, and generating a second chaotic spread spectrum code corresponding to the ith bit information code in the information code sequence through a second chaotic mapping, wherein i belongs to [2, N ]; wherein N represents the number of bits of the information code sequence; the sending chaotic spread spectrum code corresponding to each information code in the information code sequence comprises the first chaotic spread spectrum code and the second chaotic spread spectrum code.

3. The method of modulating the direct sequence spread signal according to claim 2, wherein the second chaotic map comprises:

generating a first bit in the second chaotic spread spectrum code based on the first chaotic spread spectrum code;

generating a kth bit in a second chaotic spread spectrum code based on the kth-1 bit in the second chaotic spread spectrum code, wherein K belongs to [2, K ]; wherein K represents a spreading factor and has a value equal to the predetermined number of bits.

4. The method for modulating the direct-spread signal according to any one of claims 1 to 3, wherein the generating the direct-spread signal to be transmitted according to the information code sequence and the transmission chaotic spreading code corresponding to each information code in the information code sequence comprises:

through s_i,k＝b_ix_i,kGenerating a direct sequence spread spectrum signal;

wherein, { s }_i,kDenotes the direct sequence signal to be transmitted, b_iRepresenting the ith bit of the information code sequence, x_i,kAnd K is 1,2, …, and K is a spreading factor and is equal to the preset digit.

5. A method for demodulating a direct sequence spread spectrum signal, comprising:

generating a capture signal with a preset digit number based on the received direct sequence spread spectrum signal, and generating a receiving chaotic spread spectrum code according to the capture signal;

acquiring a local chaotic spread spectrum initial value, and generating a local chaotic spread spectrum code with a preset bit number at a first preset rate based on the local chaotic spread spectrum initial value;

judging whether the received chaotic spread spectrum code and the local chaotic spread spectrum code are synchronous or not;

if the received chaotic spread spectrum code leads the local chaotic spread spectrum code, generating a local chaotic spread spectrum code with a preset digit at a second preset rate; until the received chaotic spread spectrum code is synchronous with the newly generated local chaotic spread spectrum code; wherein the second preset rate is greater than the first preset rate;

if the received chaotic spread spectrum code lags behind the local chaotic spread spectrum code, stopping generating the local chaotic spread spectrum code until the received chaotic spread spectrum code newly generated based on the newly received direct spread spectrum signal is synchronous with the local chaotic spread spectrum code;

and if the receiving chaotic spread spectrum code is synchronous with the local chaotic spread spectrum code, demodulating a direct spread spectrum signal corresponding to the synchronous receiving chaotic spread spectrum code.

6. The method for demodulating direct sequence spread spectrum signals according to claim 5, wherein said determining whether said received chaotic spreading code and said local chaotic spreading code are synchronized comprises:

when the correlation values of the local chaotic spread spectrum code and the received chaotic spread spectrum code meet a preset condition, determining that the local chaotic spread spectrum code and the received chaotic spread spectrum code are synchronous;

wherein, the IFFT [ C (n) ]]＝IFFT{[FFT(x′_i,k)]^*FFT(y_i,k) Calculating a correlation value of the local chaotic spread spectrum code and the received chaotic spread spectrum code; wherein c (k) represents a correlation value, y_i,kRepresenting the received chaotic spreading code, x'_i,kRepresents the local chaotic spreading code, and C (n) represents the discrete Fourier transform value of c (k).

7. The method for demodulating direct sequence spread spectrum signals according to claim 5, wherein the generating the local chaotic spreading code of the preset number of bits at the second preset rate comprises:

judging whether the received chaotic spread spectrum code and the local chaotic spread spectrum code are synchronized;

if the received chaotic spread spectrum code is synchronized, acquiring a first code of the local chaotic spread spectrum code synchronized with the received chaotic spread spectrum code at the latest time as an initial value of the local chaotic spread spectrum code to be generated;

if not, taking the initial value of the local chaotic spread spectrum as an initial value of a local chaotic spread spectrum code to be generated;

based on the initial value of the local chaotic spread spectrum code to be generated, generating a plurality of adjacent local chaotic spread spectrum codes with preset digits through at least two-stage chaotic mapping at a second preset rate:

{x′_am-a+1,k|k＝1,2,…,K}，{x′_am-a+2,k|k＝1,2,…,K}…{x′_am,k|k＝1,2,…,K}

wherein a represents a preset rate, and m represents the number of times of re-receiving the K-bit signal in the direct sequence spread spectrum signal after the last synchronization.

8. The method for demodulating direct-spread signals according to claim 5, wherein the demodulating the direct-spread signals corresponding to the synchronized received chaotic spreading codes comprises:

after the synchronization is judged, calculating the peak value of the correlation value of the local chaotic spread spectrum code and the received chaotic spread spectrum code through frequency domain matched filtering, and taking the sign of the peak value of the correlation value as the demodulation value of the direct spread spectrum signal corresponding to the received chaotic spread spectrum code.

9. The method for demodulating direct-spread signals according to claim 8, wherein after demodulating the direct-spread signal corresponding to the synchronized received chaotic spreading code, the method further comprises:

generating a position index of a peak of the correlation value;

and controlling the relative phase of the received chaotic spread spectrum code and the local chaotic spread spectrum code in real time according to the position index to realize synchronous tracking.

10. A terminal device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that the processor implements the steps of the method for modulating a direct spread signal according to any one of claims 1 to 4 when executing the computer program or implements the steps of the method for demodulating a direct spread signal according to any one of claims 5 to 9 when executing the computer program.

Technical Field

The present invention is applicable to the field of communications technologies, and in particular, to a method for modulating and demodulating a direct sequence spread spectrum signal and a terminal device.

Background

The application range of unmanned aerial vehicles in present and future war is continuously expanded, and the status and the effect in war are also continuously improved. However, the unmanned aerial vehicle measurement and control link is exposed in the air and is very easy to be attacked by electromagnetic attacks of enemies, and the interception resistance, the interference resistance and the confidentiality of the unmanned aerial vehicle measurement and control link must be improved to ensure the flight safety of the unmanned aerial vehicle and the combat efficiency of the unmanned aerial vehicle.

The signal direct sequence spread spectrum technology has certain physical layer confidentiality performance and anti-interference performance, and is widely applied to unmanned aerial vehicle measurement and control links at present. But the electromagnetic environment of the battlefield is increasingly complex at present, and the interference of the enemy to the direct spread signal is more intelligent. In an unmanned aerial vehicle measurement and control link, when a traditional direct sequence spread spectrum method is used for modulating signals to resist intelligent interference in modern wars, the anti-interference capability is insufficient; and as the deciphering technology is improved, the anti-deciphering capability of the signal modulated by the conventional direct sequence spread spectrum method is also insufficient.

Disclosure of Invention

In view of this, embodiments of the present invention provide a method for modulating and demodulating a direct sequence spread spectrum signal and a terminal device, so as to solve the problems of low interference resistance and insufficient decoding resistance of a signal modulated by the existing signal direct sequence spread spectrum method.

A first aspect of an embodiment of the present invention provides a method for modulating a direct sequence spread spectrum signal, including:

acquiring an information code sequence and a chaotic spread spectrum initial value;

generating a preset-bit-number transmission chaotic spread spectrum code for each information code through at least two-stage chaotic mapping based on the chaotic spread spectrum initial value;

and generating a direct spread spectrum signal to be transmitted according to the information code sequence and the transmitted chaotic spread spectrum code corresponding to each information code in the information code sequence.

Optionally, the generating a transmission chaotic spread spectrum code with a preset bit number for each information code through at least two-stage chaotic mapping based on the chaotic spread spectrum initial value includes:

generating a first chaotic spread spectrum code corresponding to a first bit information code in the information code sequence based on the chaotic spread spectrum initial value and a first chaotic mapping, and generating a second chaotic spread spectrum code corresponding to the first bit information code in the information code sequence through a second chaotic mapping;

generating a first chaotic spread spectrum code corresponding to an ith bit information code in the information code sequence based on a first chaotic spread spectrum code corresponding to an ith-1 bit information code in the information code sequence and a first chaotic mapping, and generating a second chaotic spread spectrum code corresponding to the ith bit information code in the information code sequence through a second chaotic mapping, wherein i belongs to [2, N ]; wherein N represents the number of bits of the information code sequence; the sending chaotic spread spectrum code corresponding to each information code in the information code sequence comprises the first chaotic spread spectrum code and the second chaotic spread spectrum code.

Optionally, the second chaotic map includes:

generating a first bit in the second chaotic spread spectrum code based on the first chaotic spread spectrum code;

generating a kth bit in a second chaotic spread spectrum code based on the kth-1 bit in the second chaotic spread spectrum code, wherein K belongs to [2, K ]; wherein K represents a spreading factor and has a value equal to the predetermined number of bits.

Optionally, the generating a direct sequence spread spectrum signal to be transmitted according to the information code sequence and the transmission chaotic spread spectrum code corresponding to each information code in the information code sequence includes:

through s_i,k＝b_ix_i,kGenerating a direct sequence spread spectrum signal;

wherein, { s }_i,kDenotes the direct sequence signal to be transmitted, b_iRepresenting the ith bit of the information code sequence, x_i,kAnd K is 1,2, …, and K is a spreading factor and is equal to the preset digit.

A second aspect of the embodiments of the present invention provides a method for demodulating a direct sequence spread spectrum signal, including:

generating a capture signal with a preset digit number based on the received direct sequence spread spectrum signal, and generating a receiving chaotic spread spectrum code according to the capture signal;

acquiring a local chaotic spread spectrum initial value, and generating a local chaotic spread spectrum code with a preset bit number at a first preset rate based on the local chaotic spread spectrum initial value;

judging whether the received chaotic spread spectrum code and the local chaotic spread spectrum code are synchronous or not;

if the received chaotic spread spectrum code leads the local chaotic spread spectrum code, generating a local chaotic spread spectrum code with a preset digit at a second preset rate; until the received chaotic spread spectrum code is synchronous with the newly generated local chaotic spread spectrum code; wherein the second preset rate is greater than the first preset rate;

if the received chaotic spread spectrum code lags behind the local chaotic spread spectrum code, stopping generating the local chaotic spread spectrum code until the received chaotic spread spectrum code newly generated based on the newly received direct spread spectrum signal is synchronous with the local chaotic spread spectrum code;

and if the receiving chaotic spread spectrum code is synchronous with the local chaotic spread spectrum code, demodulating a direct spread spectrum signal corresponding to the synchronous receiving chaotic spread spectrum code.

Optionally, the determining whether the received chaotic spreading code and the local chaotic spreading code are synchronous includes:

when the correlation values of the local chaotic spread spectrum code and the received chaotic spread spectrum code meet a preset condition, determining that the local chaotic spread spectrum code and the received chaotic spread spectrum code are synchronous;

wherein, the IFFT [ C (n) ]]＝IFFT{[FFT(x′_i,k)]^*FFT(y_i,k) Calculating a correlation value of the local chaotic spread spectrum code and the received chaotic spread spectrum code; wherein c (k) represents a correlation value, y_i,kRepresenting the received chaotic spreading code, x'_i,kRepresents the local chaotic spreading code, and C (n) represents the discrete Fourier transform value of c (k).

Optionally, the generating the local chaotic spreading code with the preset number of bits at the second preset rate includes:

judging whether the received chaotic spread spectrum code and the local chaotic spread spectrum code are synchronized;

if the received chaotic spread spectrum code is synchronized, acquiring a first code of the local chaotic spread spectrum code synchronized with the received chaotic spread spectrum code at the latest time as an initial value of the local chaotic spread spectrum code to be generated;

if not, taking the initial value of the local chaotic spread spectrum as an initial value of a local chaotic spread spectrum code to be generated;

based on the initial value of the local chaotic spread spectrum code to be generated, generating a plurality of adjacent local chaotic spread spectrum codes with preset digits through at least two-stage chaotic mapping at a second preset rate:

{x′_am-a+1,k|k＝1,2,…,K}，{x′_am-a+2,k|k＝1,2,…,K}…{x′_am,k|k＝1,2,…,K}

wherein a represents a preset rate, and m represents the number of times of re-receiving the K-bit signal in the direct sequence spread spectrum signal after the last synchronization.

Optionally, the demodulating the direct spread spectrum signal corresponding to the synchronized received chaotic spreading code includes:

after the synchronization is judged, calculating the peak value of the correlation value of the local chaotic spread spectrum code and the received chaotic spread spectrum code through frequency domain matched filtering, and taking the sign of the peak value of the correlation value as the demodulation value of the direct spread spectrum signal corresponding to the received chaotic spread spectrum code.

Optionally, after the demodulating the direct-spread signal corresponding to the synchronized received chaotic spreading code, the method for demodulating the direct-spread signal further includes:

generating a position index of a peak of the correlation value;

and controlling the relative phase of the received chaotic spread spectrum code and the local chaotic spread spectrum code in real time according to the position index to realize synchronous tracking.

A third aspect of the embodiments of the present invention provides a terminal device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, where the processor implements the steps of the method for modulating a direct spread signal according to the first aspect of the embodiments of the present invention when executing the computer program, or implements the steps of the method for demodulating a direct spread signal according to the second aspect of the embodiments of the present invention when executing the computer program.

The method comprises the steps of acquiring an information code sequence and a chaotic spread spectrum initial value, generating a transmission chaotic spread spectrum code with a preset bit number for each information code through at least two-stage chaotic mapping based on the chaotic spread spectrum initial value, and generating a direct spread spectrum signal to be transmitted according to the information code sequence and the transmission chaotic spread spectrum code corresponding to each information code in the information code sequence. The chaotic spread spectrum code correspondingly generated according to the chaotic mapping has the non-periodic characteristic, and the spectrum of the information code is expanded by using the chaotic spread spectrum code, so that the difficulty of implementing intelligent interference by an enemy can be effectively increased; the chaotic spread spectrum codes are generated and transmitted based on at least two-stage chaotic mapping, for one bit of information codes, each chaotic spread spectrum code in the chaotic spread spectrum codes corresponding to the information codes is different, and for any two bit of information codes, the first bit of the chaotic spread spectrum codes corresponding to the two bit of information codes is also different, so that the anti-decoding capability can be effectively improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

FIG. 1 is a schematic diagram of a scenario application provided by an embodiment of the present invention;

fig. 2 is a schematic flow chart of a modulation method of a direct sequence spread spectrum signal according to an embodiment of the present invention;

fig. 3 is a schematic flow chart of generating a chaotic spreading code based on two-stage chaotic mapping according to an embodiment of the present invention;

FIG. 4 is a diagram of a data processing model of a spread spectrum process provided by an embodiment of the invention;

fig. 5 is a flowchart illustrating a method for demodulating a direct sequence spread spectrum signal according to an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a dual channel capture system provided by an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a post-acquisition direct sequence spread spectrum signal demodulation system according to an embodiment of the present invention;

fig. 8 is a schematic diagram of a terminal device according to an embodiment of the present invention.

Detailed Description

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system architectures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.