Coherent chaotic communication method and system with receiving diversity gain

Abstract

The invention provides a coherent chaotic communication method and system with receiving diversity gain, and relates to the technical field of wireless communication, and the method comprises the steps: presetting Logistic sequence first value vectors at a transmitting end and a receiving end, and respectively generating chaotic sequences; a chaotic sequence generated by a receiving end is subjected to reverse convolution operation to obtain a cross-correlation vector, then the cross-correlation vector is subjected to square detection operation to obtain diversity gain of a received signal multipath channel, and finally a serial number of a selected chaotic initial value in the vector of the chaotic initial value is solved and bit conversion is performed to obtain a corresponding estimation information bit. The system has higher energy efficiency, uses less energy under the condition of realizing the same bit error rate of a multi-carrier differential shift keying communication system, can realize coherent detection without executing chaotic synchronization, and can realize high-performance communication in a multipath Rayleigh fading channel scene.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and more specifically, to a coherent chaotic communication method and system with receiving diversity gain. Background Art

[0002] Chaotic communication is a spread spectrum communication technology that uses the broadband characteristics of chaotic signals to easily build chaotic broadband communication systems. Therefore, chaotic communication technology has received more and more attention. Since the multi-carrier differential shift chaotic keying communication system needs to distribute information on multiple carriers for transmission, multiple matching filters are required in the receiver, making the system more complex. In addition, a carrier is required in the signal of the multi-carrier differential shift chaotic keying communication system to send a reference signal (the reference signal does not carry information), resulting in energy waste.

[0003] The prior art discloses a chaotic communication method and system based on initial value modulation, wherein the initial information bits to be sent are divided into modulation bits and sequence bits in the modulation process, wherein the modulation bits are carried by the polarity of chaotic signals, and the sequence bits are transmitted by the initial value of chaotic sequences; in the demodulation process, the modulation bits and sequence bits are demodulated respectively, and the estimated information bits obtained by demodulating the modulation bits and sequence bits are combined to obtain the estimated information bits of all information bits, so that multiple information bits can be transmitted in parallel without using multiple subcarriers, and the energy efficiency of the system is effectively improved. However, the scheme adopts non-coherent demodulation technology, and uses the reference signal and the information-carrying signal on the remaining carriers for correlation operation to demodulate; since the reference signal and the information-carrying signal on the remaining carriers contain noise at the receiving end, the use of these two signals for demodulation will further lead to the deterioration of the bit error rate performance. Summary of the invention

[0004] In order to solve the problem that the bit error rate performance cannot be guaranteed in the current chaotic communication system, the present invention proposes a coherent chaotic communication method and system with receive diversity gain, which can realize parallel transmission of multiple information bits without using multiple subcarriers, generate a series of chaotic signals using the first value of a preset Logistic sequence, and realize coherent detection using noise-free contaminated chaotic signals combined with a square detection algorithm, thereby improving the bit error rate performance of the system under a multipath Rayleigh fading channel.

[0005] In order to achieve the above technical effects, the technical solution of the present invention is as follows:

[0006] A coherent chaotic communication method with receiving diversity gain includes a modulation process and a demodulation process;

[0007] The modulation process comprises the following steps:

[0008] S1. Send the information bits b1,…,b M Convert to decimal symbol D M ;

[0009] S2. Preset a Logistic sequence first value vector at the transmitting end, wherein the absolute values ​​of all chaotic initial vectors in the Logistic sequence first value vector are less than 1;

[0010] S3. Select the Dth chaotic initial value vector preset at the transmitting end. M +1 Logistic sequence first value, transmitted to the chaotic signal generator to generate the chaotic sequence used by the transmitter;

[0011] The demodulation process comprises the following steps:

[0012] S4. Generate a chaotic sequence used by the receiving end through a preset Logistic sequence first value vector at the receiving end;

[0013] S5. The chaotic sequence is respectively subjected to an inverse convolution operation with a reference signal in a received signal obtained by a receiving end to obtain a cross-correlation vector;

[0014] S6. Perform a square detection operation on the cross-correlation vector to obtain a diversity gain of the multipath channel of the received signal;

[0015] S7. Based on the diversity gain of the multipath channel, solve the sequence number Q of the selected chaotic initial value in the vector of chaotic initial values, perform decimal symbol / binary bit conversion on Q, and obtain the estimated information bit

[0016] This technical solution generates a noise-free chaotic signal and combines it with a square detection algorithm to achieve coherent detection, thereby effectively improving the bit error rate performance under a multipath Rayleigh fading channel.

[0017] Preferably, the preset Logistic sequence first value vector contains 2 M The first value of the Logistic sequence, 0≤D M ≤2 M -1.

[0018] Preferably, in step S3, select the D M +1 Logistic sequence first value Will Transmitted to the chaotic signal generator, the chaotic sequence used by the transmitter is generated using Logistic mapping Where β is the spreading factor and is greater than 2 M A positive integer.

[0019] Preferably, the transmission signal of the transmitting end is s=c select , the received signal obtained by the receiving end is r=[r1,…,r β ].

[0020] Preferably, in step S4, the first value vector of the Logistic sequence is preset Build 2 M chaotic sequences, where j = 1, 2, ..., 2 M ; The 2 M The chaotic sequences are recorded as all the chaotic sequences that may be used by the receiving end.

[0021] Preferably, step S5 comprises the following steps:

[0022] S51. Let the chaotic sequence perform deconvolution operation with the reference signal in the received signal respectively, and obtain Z j ; The reverse convolution operation is as follows:

[0023] Z j =[r1,…,r β ]*[L j,β ,…,L j,β-1 ,…,L j,1 ]=[R j,1 ,…,R j,m ,…,R j,2β-1 ]

[0024] Among them, * is the convolution operator;

[0025] S52.To Z j The elements in are further processed to obtain Among them, l d is the convolution coefficient, l d ≤β-1.

[0026] Preferably, the convolution coefficient l d The calculation method is as follows:

[0027] Every 100 bits, the transmitter sends a L signal before sending the information bit. 1,1 The chaotic sequence L1=[L 1,1 ,…,L 1,2 ,…,L 1,β ], the receiving end generates the same chaotic sequence;

[0028] The chaotic sequence sent by the transmitter is cross-correlated with the chaotic sequence generated locally by the receiver to obtain the vector C = [c1,…,c 2β-1 ];

[0029] Replace c in vector C β ,…,c 2β-1 Item greater than Count the subscripts and derive the largest subscript l max , where E(·) is the mean operation of the vector; let l d = l max .

[0030] Preferably, in step S6, Each term in is squared and summed to obtain the diversity gain of the multipath channel of the received signal. The formula is as follows:

[0031]

[0032] in, is the diversity gain of the multipath channel.

[0033] Preferably, in step S7, the sequence number Q of the selected chaotic initial value in the vector of chaotic initial values ​​is solved, and the formula is as follows:

[0034]

[0035] A coherent chaotic communication system with receiving diversity gain includes a transmitter and a receiver. The transmitter is used to implement the modulation process of the coherent chaotic communication method with receiving diversity gain, and the receiver is used to implement the demodulation process of the coherent chaotic communication method with receiving diversity gain.

[0036] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0037] The present invention proposes a coherent chaotic communication method and system with receiving diversity gain. The method presets a Logistic sequence header value vector at a transmitting end and a receiving end, and generates chaotic sequences respectively; the chaotic sequence generated by the receiving end obtains a cross-correlation vector by performing an inverse convolution operation, and then performs a square detection operation on the cross-correlation vector to obtain a diversity gain of a multipath channel of a received signal, and finally solves the sequence number of a chaotic initial value selected in a vector of chaotic initial values ​​and performs bit conversion to obtain a corresponding estimated information bit; the system has higher energy efficiency, uses less energy while achieving the same bit error rate of a multi-carrier differential shift keying communication system, and can achieve coherent detection without performing chaotic synchronization, and can achieve high-performance communication in a multipath Rayleigh fading channel scenario. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic flow chart of a coherent chaotic communication method with receiving diversity gain proposed in Embodiment 1 of the present invention is shown;

[0039] Figure 2 A schematic diagram showing a comparison of the bit error rate performance of the coherent chaotic communication system with receive diversity gain proposed in embodiments 2 and 3 of the present invention under multipath Rayleigh fading channel conditions and the chaotic communication system based on initial value modulation in the prior art. DETAILED DESCRIPTION

[0040] The drawings are for illustrative purposes only and should not be construed as limiting the present patent;

[0041] In order to better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the actual size;

[0042] It is understandable to those skilled in the art that descriptions of certain well-known contents in the drawings may be omitted.

[0043] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0044] The positional relationships described in the drawings are only for illustrative purposes and should not be construed as limiting the present patent;

[0045] Example 1

[0046] like Figure 1 As shown, this embodiment proposes a coherent chaotic communication method with receiving diversity gain, including a modulation process and a demodulation process;

[0047] The modulation process comprises the following steps:

[0048] S1. Send the information bits b1,…,b M Convert to decimal symbol D M ;

[0049] S2. A Logistic sequence header vector is preset at the transmitter. The preset Logistic sequence header vector contains 2 M The first value of the Logistic sequence, 0≤D M ≤2 M -1; the absolute values ​​of all chaotic initial values ​​in the first value vector of the Logistic sequence are less than 1;

[0050] S3. Select the Dth chaotic initial value vector preset by the transmitter. M +1 Logistic sequence first value Will Transmitted to the chaotic signal generator, the chaotic sequence used by the transmitter is generated using Logistic mapping Where β is the spreading factor and is greater than 2 MA positive integer, the Logistic mapping is:

[0051]

[0052] Here, the transmission signal s = c at the transmitting end is obtained. select .

[0053] The demodulation process comprises the following steps:

[0054] S4. At the receiving end, the first value vector of the preset Logistic sequence is Build 2 M chaotic sequences, where j = 1, 2, ..., 2 T ; The 2 T The chaotic sequences are recorded as all possible chaotic sequences used by the receiving end;

[0055] S5. The chaotic sequence is respectively connected to the receiving signal r = [r1, ..., r β ] performs a reverse convolution operation on the reference signal to obtain a cross-correlation vector; step S5 comprises the following specific steps:

[0056] S51. Let the chaotic sequence perform deconvolution operation with the reference signal in the received signal respectively, and obtain Z j ; The reverse convolution operation is as follows:

[0057] z j =[r1,…,r β ]*[L j,β ,…,L j,β-1 ,…,L j,1 ]=[R j,1 ,…,R j,m ,…,R j,2β-1 ]

[0058] Among them, * is the convolution operator;

[0059] S52.To Z j The elements in are further processed to obtain Among them, l d is the convolution coefficient, l d ≤β-1.

[0060] In this embodiment, the convolution coefficient l d The calculation method is as follows:

[0061] Every 100 bits, the transmitter sends a L signal before sending the information bit. 1,1 The chaotic sequence L1=[L 1,1 ,…,L 1,2,…,L 1,β ], the receiving end generates the same chaotic sequence;

[0062] The chaotic sequence sent by the transmitter is cross-correlated with the chaotic sequence generated locally by the receiver to obtain the vector C = [c1,…,c 2β-1 ];

[0063] Replace c in vector C β ,…,c 2β-1 Item greater than Count the subscripts and derive the largest subscript l max , where E(·) is the mean operation of the vector; let l d = l max .

[0064] S6. Perform a square detection operation on the cross-correlation vector to obtain the diversity gain of the multipath channel of the received signal; specifically, Each term in is squared and summed, and the formula is as follows:

[0065]

[0066] in, is the diversity gain of the multipath channel.

[0067] S7. Based on the diversity gain of the multipath channel, the sequence number Q of the selected chaotic initial value in the vector of chaotic initial values ​​is solved, and the formula is as follows:

[0068]

[0069] Convert Q to decimal symbol / binary bit to get the estimated information bit

[0070] It should be noted that the channel model used in the present invention is a multipath Rayleigh fading channel, and the received signal after the channel demodulator is:

[0071]

[0072] Among them, autocorrelation demodulation is an existing demodulation method widely used in differential shift chaotic keying communication systems. When the system is started, the modulator will modulate the information to be sent, and the transmitted signal s modulated by the modulator becomes the received signal r of the demodulator after passing through the channel. Subsequently, the demodulator performs a correlation integral operation on the received signal and the signal after the delay Td to obtain the decision variable Z. The process can be expressed as:

[0073]

[0074] The decision rule is: if Z is greater than 0, the recovered bit is "1", if Z is less than 0, the recovered information bit is "-1".

[0075] Example 2

[0076] This embodiment provides a coherent chaotic communication system with receiving diversity gain, including a transmitting end and a receiving end.

[0077] Specifically, the transmitting end is used to implement a modulation process, and the modulation process includes the following steps:

[0078] S1. Send the information bits b1,…,b M Convert to decimal symbol D M ;

[0079] S2. Preset a Logistic sequence first value vector at the transmitting end, wherein the absolute values ​​of all chaotic initial vectors in the Logistic sequence first value vector are less than 1;

[0080] S3. Select the Dth chaotic initial value vector preset at the transmitting end. M +1 Logistic sequence first value is transmitted to the chaotic signal generator to generate the chaotic sequence used by the transmitter.

[0081] The receiving end is used to implement a demodulation process, and the demodulation process includes the following steps:

[0082] S4. Generate a chaotic sequence used by the receiving end through a preset Logistic sequence first value vector at the receiving end;

[0083] S5. The chaotic sequence is respectively subjected to an inverse convolution operation with a reference signal in a received signal obtained by a receiving end to obtain a cross-correlation vector;

[0084] S6. Perform a square detection operation on the cross-correlation vector to obtain a diversity gain of the multipath channel of the received signal;

[0085] S7. Based on the diversity gain of the multipath channel, solve the sequence number Q of the selected chaotic initial value in the vector of chaotic initial values, perform decimal symbol / binary bit conversion on Q, and obtain the estimated information bit

[0086] Example 3

[0087] In this embodiment, under a multipath Rayleigh fading channel environment, the coherent chaotic communication system (D M =3, β = 75) is comparable to the chaotic communication system based on initial value modulation in the prior art (D M=3, β=75) for comparison.

[0088] like Figure 2 As shown, under the multipath Rayleigh fading channel condition, the coherent chaotic communication system with receive diversity gain proposed in this embodiment can still have excellent bit error rate performance, while the chaotic communication system based on initial value modulation cannot work normally under the channel condition and a bit error rate plateau occurs.

[0089] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A coherent chaotic communication method with receive diversity gain, characterized in that: Including modulation process and demodulation process; The modulation process comprises the following steps: S1. Send the information bits b1,…,b M Convert to decimal symbol D M ; S2. Preset a Logistic sequence first value vector at the transmitting end, wherein the absolute values ​​of all chaotic initial values ​​in the Logistic sequence first value vector are less than 1; S3. Select the Dth chaotic initial value vector preset at the transmitting end. M +1 Logistic sequence first value, transmitted to the chaotic signal generator to generate the chaotic sequence used by the transmitter; The demodulation process comprises the following steps: S4. Generate a chaotic sequence used by the receiving end through a preset Logistic sequence first value vector at the receiving end; S5. The chaotic sequence is respectively subjected to an inverse convolution operation with a reference signal in a received signal obtained by a receiving end to obtain a cross-correlation vector; S6. Perform a square detection operation on the cross-correlation vector to obtain a diversity gain of the multipath channel of the received signal; S7. Based on the diversity gain of the multipath channel, solve the sequence number Q of the selected chaotic initial value in the vector of chaotic initial values, perform decimal symbol / binary bit conversion on Q, and obtain the estimated information bit 2. The coherent chaotic communication method with receive diversity gain according to claim 1, characterized in that: The default Logistic sequence first value vector contains 2 M The first value of the Logistic sequence, 0≤D M ≤2 M -1.

3. The coherent chaotic communication method with receive diversity gain according to claim 2, characterized in that: In step S3, select the D M +1 Logistic sequence first value Will Transmitted to the chaotic signal generator, the chaotic sequence used by the transmitter is generated using Logistic mapping Where β is the spreading factor and is greater than 2 M A positive integer.

4. The coherent chaotic communication method with receive diversity gain according to claim 3, characterized in that: The transmitting signal of the transmitting end is s=c select , the received signal obtained by the receiving end is r=[r1,…,r β ].

5. The coherent chaotic communication method with receive diversity gain according to claim 4, characterized in that: In step S4, the first value vector of the Logistic sequence is preset Build 2 M chaotic sequences, where j = 1, 2, ..., 2 M ; The 2 M The chaotic sequences are recorded as all the chaotic sequences that may be used by the receiving end.

6. The coherent chaotic communication method with receive diversity gain according to claim 5, characterized in that: Step S5 includes the following steps: S51. Let the chaotic sequence perform deconvolution operation with the reference signal in the received signal respectively, and obtain Z j ; The reverse convolution operation is as follows: Z j =[r1,…,r β ]*[L j,β ,…,L j,β-1 ,…,L j,1 ]=[R j,1 ,…,R j,m ,…,R j,2β-1 ] Among them, * is the convolution operator; S52.To Z j The elements in are further processed to obtain Among them, l d is the convolution coefficient, l d ≤β-1.

7. The coherent chaotic communication method with receive diversity gain according to claim 5, characterized in that: The convolution coefficient l d The calculation method is as follows: Every 100 bits, the transmitter sends a L signal before sending the information bit. 1,1 The chaotic sequence L1=[L 1,1 ,…,L 1,2 ,…,L 1,β ], the receiving end generates the same chaotic sequence; The chaotic sequence sent by the transmitter is cross-correlated with the chaotic sequence generated locally by the receiver to obtain the vector C = [c1,…,c 2β-1 ]; Replace c in vector C β ,…,c 2β-1 Item greater than Count the subscripts and derive the largest subscript l max , where E(·) is the mean operation of the vector; let l d = l max .

8. The coherent chaotic communication method with receive diversity gain according to claim 5, characterized in that: In step S6, Each term in is squared and summed to obtain the diversity gain of the multipath channel of the received signal. The formula is as follows: in, is the diversity gain of the multipath channel.

9. The coherent chaotic communication method with receiving diversity gain according to claim 5, characterized in that: In step S7, the sequence number Q of the selected chaos initial value in the vector of chaos initial values ​​is solved, and the formula is as follows:

10. A coherent chaotic communication system with receiving diversity gain, comprising a transmitting end and a receiving end, characterized in that: The transmitting end is used to implement the modulation process of the coherent chaotic communication method with receiving diversity gain described in any one of claims 1 to 9, and the receiving end is used to implement the demodulation process of the coherent chaotic communication method with receiving diversity gain described in any one of claims 1 to 9.

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