Chaotic communication method and system with noise reduction function

Abstract

The invention provides a chaotic communication method and system with a noise reduction function, and the method comprises the steps: dividing transmitted information bits into two parts for transmission, generating a chaotic sequence used by a transmitting end through the first M information bits, carrying the last N information bits through the polarity of the chaotic sequence, and jointly generating a transmitting signal, a chaos sequence generated by a receiving end is utilized to construct channel quality detection variables of a received signal, channel quality judgment is carried out, a label with the maximum value in the channel quality detection variables is converted into estimated information bits of first M information bits, and judgment variables of remaining N information bits are calculated by utilizing the channel quality detection variables, estimating estimated information bits of the last N information bits; the noise reduction function is integrated in the channel quality detection operation, the complexity of the system is reduced, the first M information bits and the last N information bits have different protection degrees, and more important data can be borne by the last N information bits during information transmission.

Description

Technical Field

[0001] The present invention relates to the field of signal transmission technology, and more specifically, to a chaotic communication method and system with noise reduction function. Background Art

[0002] Chaotic communication technology is a secure communication technology that uses the properties of chaos theory to achieve information transmission. Chaotic phenomena are random-like processes that occur in deterministic nonlinear systems. They are extremely sensitive to initial conditions, which means that even small changes can lead to completely different results, resulting in complex and unpredictable behaviors. This characteristic gives chaotic signals unique advantages in communication, especially in the field of confidential communication. However, in the multipath Rayleigh fading channel scenario, the transmission quality of chaotic communication systems is difficult to guarantee. The multipath Rayleigh fading channel scenario is a common channel model in wireless communications. Especially in urban environments, due to the obstruction and reflection of buildings, wireless signals often reach the receiver through multiple paths. In such an environment, additive white Gaussian noise (AWGN) and other interference sources in the multipath Rayleigh fading channel will affect the transmission quality of the signal, causing the amplitude and phase of the signal to change randomly at the receiver, forming a fading phenomenon, and affecting the reliability of communication. Summary of the invention

[0003] In order to solve the problem of low signal transmission quality in the current chaotic communication system under the multipath Rayleigh fading channel scenario, the present invention proposes a chaotic communication method and system with noise reduction function, which integrates channel quality detection with information bit demodulation and incorporates noise reduction function into the channel quality detection operation.

[0004] In order to achieve the above technical effects, the technical solution of the present invention is as follows:

[0005] A chaotic communication method with noise reduction function, comprising:

[0006] S1. Preset a Logistic sequence header vector at the transmitting end and the receiving end;

[0007] S2. Send the information bit b 1 ,…,b M ,…,b M+N The transmission is divided into two parts, in which the first M information bits and the first value vector of the Logistic sequence are used to generate the chaotic sequence used by the transmitter, and the last N information bits are carried by the polarity of the chaotic sequence to jointly generate the transmission signal;

[0008] S3. The transmitted signal is converted into a received signal after passing through the channel;

[0009] S4. The receiving end generates all possible chaotic sequences that can be used by the receiving end through the preset Logistic sequence first value vector as the receiving end local noise-free reference signal;

[0010] S5. Using the local noise-free reference signal at the receiving end, construct the channel quality detection variable of the received signal and make a channel quality judgment. The largest value of the channel quality detection variable is converted into the estimated information bit of the first M information bits.

[0011] S6. Calculate the decision variables of the remaining N information bits using the channel quality detection variable, and estimate the estimated information bits of the last N information bits using the decision variables

[0012] This technical solution combines the first numerical vector of the Logistic sequence and the polarity of the chaotic signal to carry information, carrying M and N information bits respectively, and the two types of information bits can have different protection levels; in addition, this technical solution cleverly combines channel quality detection with the demodulation of the first M information bits, and incorporates a noise reduction function into the channel quality detection operation, and the demodulation mode of the last N information bits depends on the channel quality.

[0013] Preferably, the preset Logistic sequence first value vector is a vector with 2 M The vector of the first values ​​of the logistic sequence The absolute values ​​of all chaotic initial vectors in the first numerical vector of the Logistic sequence are less than 1.

[0014] Preferably, in step S2, the chaotic sequence used by the transmitting end is generated using the first M information bits, and the process includes:

[0015] The first M information bits that the transmitter needs to transmit are converted into the corresponding decimal symbol D M , select D M +1The first value of the Logistic sequence is

[0016] Will Transmitted to the chaotic signal generator, the Logistic map is used to generate the chaotic sequence used by the transmitter Where β is the spreading factor.

[0017] Preferably, in step S2, the transmitted signal s is expressed as:

[0018]

[0019] Each line is a carrier, and the center frequencies of the first carrier to the N+1th carrier are f 1,…,f N+1 .

[0020] Preferably, in step S3, the transmission signal s is converted into a reception signal r by matched filtering after passing through the channel, and the reception signal r is expressed as:

[0021]

[0022] Preferably, in step S4, the receiving end uses a preset M The vector of the first values ​​of the logistic sequence Build 2 M chaotic sequences, where j = 1, 2, ..., 2 M , the 2 M The chaotic sequences are all possible chaotic sequences used by the receiving end as the local noise-free reference signals of the receiving end.

[0023] Preferably, step S5 lays a foundation for adaptive demodulation by performing channel quality determination, and includes the following steps:

[0024] S51. Construct channel quality detection variables The expression is as follows:

[0025]

[0026] in, is the transposed conjugate symbol, [L j,1 ,…,L j,β ] is a local noise-free reference signal at the receiving end generated according to the first value of the j-th preset Logistic sequence;

[0027] S52. Calculation 2 M The label C with the largest value among the channel quality detection variables is as follows:

[0028]

[0029] S53. Convert C from decimal symbols to binary bits to obtain the estimated information bits of the first M information bits

[0030] Here, the chaotic sequences of all carriers are correlated with the noise-free reference signal generated by the receiving end and summed to achieve noise reduction. Since the useful signal in each carrier is the same and the noise is random, the sum of N+1 items makes the variance of the useful component become (N+1) of the original single-item variance. 2 times, and the variance of the noise component becomes (N+1) times that of the single term.

[0031] Preferably, in step S6, the decision variable of the remaining N information bits is calculated using the channel quality detection variable, and the process is as follows:

[0032] like For information bit b t , the decision variable Φ t The formula is:

[0033]

[0034] like For information bit b t , the decision variable Φ t The formula is:

[0035]

[0036] Wherein, μ is the channel quality decision threshold coefficient, and its value range is (0.1, 0.5); M+1≤t≤M+N.

[0037] Preferably, in step S6, estimating the estimated information bits of the last N information bits by using the decision variable, the process includes:

[0038] If Φ t ≥0, information bit b t Estimated information bits Estimated to be +1, if Φ t <0, then the information bit b t Estimated information bits Estimated to be -1.

[0039] A chaotic communication system with noise reduction function comprises a transmitting end and a receiving end. The system comprises a transmitting end for implementing the chaotic communication method with noise reduction function and a receiving end for implementing the chaotic communication method with noise reduction function.

[0040] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0041] The present invention proposes a chaotic communication method and system with a noise reduction function. First, a Logistic sequence header value vector is preset at a transmitting end and a receiving end, and the information bits to be transmitted are divided into two parts for transmission. The first M information bits are used to generate a chaotic sequence used by the transmitting end, and the second N information bits are carried by the polarity of the chaotic sequence to jointly generate a transmitting signal. The chaotic sequence generated by the receiving end is used to construct a channel quality detection variable of the receiving signal and perform channel quality judgment. A label with the largest value in the channel quality detection variable is converted into an estimated information bit of the first M information bits, and a decision variable of the remaining N information bits is calculated by using the channel quality detection variable. The estimated information bits of the second N information bits are estimated by the decision variable. The present invention integrates a noise reduction function into a channel quality detection operation, thereby reducing the complexity of the system. In addition, the first M information bits and the second N information bits have different protection levels, and more important data can be carried by the second N information bits during information transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic flow chart showing a chaotic communication method with noise reduction function proposed in Embodiment 1 of the present invention;

[0043] Figure 2 A schematic diagram showing a comparison of the bit error rate performance of the chaotic communication method with noise reduction function proposed in Embodiments 2 and 3 of the present invention and the existing multi-carrier differential shift keying communication system. DETAILED DESCRIPTION

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

[0045] 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;

[0046] It is understandable to those skilled in the art that descriptions of certain well-known contents in the drawings may be omitted.

[0047] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0048] The positional relationships described in the drawings are only for illustrative purposes and should not be construed as limiting the present patent;

[0049] Example 1

[0050] like Figure 1 As shown, this embodiment proposes a chaotic communication method with noise reduction function, comprising the following steps:

[0051] S1. A Logistic sequence header value vector is preset at the transmitting end and the receiving end; the preset Logistic sequence header value vector is a vector with 2 M The vector of the first values ​​of the logistic sequence The absolute values ​​of all chaotic initial vectors in the first numerical vector of the Logistic sequence are less than 1.

[0052] Among them, the mapping rule of Logistic mapping is:

[0053] S2. Send the information bit b 1 ,…,b M ,…,b M+N The transmission is divided into two parts;

[0054] In the first part, the first M information bits that the transmitter needs to transmit are converted into the corresponding decimal symbols D M , select D M +1The first value of the Logistic sequence is

[0055] Will Transmitted to the chaotic signal generator, the Logistic map is used to generate the chaotic sequence used by the transmitter Where β is the spreading factor.

[0056] In the second part, the last N information bits are carried using the polarity of the chaotic sequence.

[0057] In this embodiment, the transmission signal s is expressed as:

[0058]

[0059] Each line is a carrier, and the center frequencies of the first carrier to the N+1th carrier are f 1 ,…,f N+1 .

[0060] S3. The transmitted signal s is converted into a received signal r through matched filtering after passing through the channel. The received signal r is expressed as:

[0061]

[0062] S4. The receiving end has 2 preset M The vector of the first values ​​of the logistic sequence Build 2 M chaotic sequences, where j = 1, 2, ..., 2 M , the 2 MThe chaotic sequences are all possible chaotic sequences used by the receiving end as the local noise-free reference signals of the receiving end.

[0063] S5. Using the chaotic sequence generated by the receiving end, construct the channel quality detection variable of the received signal and make a channel quality judgment. The largest value of the channel quality detection variable is converted into the estimated information bit of the first M information bits. The specific process is as follows:

[0064] S51. Construct channel quality detection variables for received signals The expression is as follows:

[0065]

[0066] in, is the transposed conjugate symbol, [L j,1 ,…,L j,β ] is the local noise-free reference signal of the receiving end generated according to the first value of the j-th preset Logistic sequence; it should be noted that step S51 performs correlation operation on the chaotic sequences of all carriers and the noise-free reference signal generated by the receiving end and sums them, which can play a role in noise reduction, because the useful signal in each carrier is the same and the noise is random, so the sum of the (N+1) items makes the variance of the useful component become (N+1) times the original single-item variance 2 times, and the variance of the noise component becomes (N+1) times that of the single term.

[0067] S52. Calculation 2 M The label C with the largest value among the channel quality detection variables is as follows:

[0068]

[0069] S53. Convert C from decimal symbols to binary bits to obtain the estimated information bits of the first M information bits

[0070] S6. Calculate the decision variables of the remaining N information bits using the channel quality detection variable, and estimate the estimated information bits of the last N information bits using the decision variables

[0071] The decision variables of the remaining N information bits are calculated using the channel quality detection variables. The process is as follows:

[0072] like For information bit b t , the decision variable Φ t The formula is:

[0073]

[0074] like For information bit b t , the decision variable Φ t The formula is:

[0075]

[0076] Wherein, μ is the channel quality decision threshold coefficient, and its value range is (0.1, 0.5). In the specific implementation process, μ=0.2; M+1≤t≤M+N.

[0077] Specifically, if Φ t ≥0, information bit b t Estimated information bits Estimated to be +1; if Φ t <0, then the information bit b t Estimated information bits Estimated to be -1; here, the estimated information bits of the last N information bits are obtained

[0078] It should be noted that the Logistic chaotic signal has uniform probability density and ideal correlation characteristics. The Logistic mapping can be expressed as:

[0079]

[0080] In this embodiment, the channel model used is a multipath Rayleigh fading channel, and the received signal after the channel demodulator is:

[0081]

[0082] When the system starts, the modulator will modulate the information to be sent. 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 integration operation on the received signal and the signal after the delay Td to obtain the decision variable Z. The process can be expressed as:

[0083]

[0084] 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".

[0085] Example 2

[0086] This embodiment proposes a chaotic communication system with noise reduction function, including a transmitter and a receiver. The system includes a transmitter for implementing the above-mentioned chaotic communication method with noise reduction function and a receiver for implementing the above-mentioned chaotic communication method with noise reduction function.

[0087] Specifically, the transmitting end and the receiving end are both preset with a Logistic sequence first value vector;

[0088] The transmitting end is used to implement the following steps:

[0089] The information bit b to be sent 1 ,…,b M ,…,b M+N It is divided into two parts for transmission, in which the first M information bits and the first numerical vector of the Logistic sequence are used to generate the chaotic sequence used by the transmitter, and the last N information bits are carried by the polarity of the chaotic sequence to jointly generate the transmission signal.

[0090] Among them, the transmission signal is converted into a reception signal after passing through the channel.

[0091] The receiving end is used to implement the following steps:

[0092] The chaotic sequence generated by the receiving end is used to construct the channel quality detection variable of the received signal and perform channel quality judgment. The largest value in the channel quality detection variable is converted into the estimated information bit of the first M information bits.

[0093] The channel quality detection variable is used to calculate the decision variable of the remaining N information bits, and the estimated information bits of the last N information bits are estimated by the decision variable.

[0094] Example 3

[0095] In this embodiment, in a multipath Rayleigh fading channel environment, the chaotic communication system with noise reduction function based on embodiment 2 (D M =4, β = 75) and the bit error rate performance of the existing multi-carrier differential shift keying communication system (D M =4, β=75) for comparison.

[0096] like Figure 2 As shown in the figure, under the multipath Rayleigh fading channel condition, the bit error rate level is 10 -4 When the chaotic communication with noise reduction function proposed in this embodiment has a gain of 13dB compared with the existing multi-carrier differential shift keying communication system.

[0097] 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 chaotic communication method with noise reduction function, characterized in that: include: S1. Preset a Logistic sequence header vector at the transmitting end and the receiving end; S2. Send the information bits b1,…,b M ,…,b M+N The transmission is divided into two parts, in which the first M information bits and the first value vector of the Logistic sequence are used to generate the chaotic sequence used by the transmitter, and the last N information bits are carried by the polarity of the chaotic sequence to jointly generate the transmission signal; S3. The transmitted signal is converted into a received signal after passing through the channel; S4. The receiving end generates all possible chaotic sequences that can be used by the receiving end through the preset Logistic sequence first value vector as the receiving end local noise-free reference signal; S5. Using the local noise-free reference signal at the receiving end, construct the channel quality detection variable of the received signal and make a channel quality judgment. The largest value of the channel quality detection variable is converted into the estimated information bit of the first M information bits. S6. Calculate the decision variables of the remaining N information bits using the channel quality detection variable, and estimate the estimated information bits of the last N information bits using the decision variables 2. The chaotic communication method with noise reduction function according to claim 1, characterized in that: The preset Logistic sequence first value vector is a vector with 2 M The vector of the first values ​​of the logistic sequence The absolute values ​​of all chaotic initial vectors in the first numerical vector of the Logistic sequence are less than 1.

3. The chaotic communication method with noise reduction function according to claim 2, characterized in that: In step S2, the chaotic sequence used by the transmitter is generated using the first M information bits. The process includes: The first M information bits that the transmitter needs to transmit are converted into the corresponding decimal symbol D M , select D M +1The first value of the Logistic sequence is 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.

4. The chaotic communication method with noise reduction function according to claim 3, characterized in that: In step S2, the transmitted signal s is expressed as: Each line is a carrier wave, and the center frequencies of the first carrier wave to the N+1th carrier wave are f1,…,f N+1 .

5. The chaotic communication method with noise reduction function according to claim 4, characterized in that: In step S3, the transmission signal s is converted into a receiving signal r through matched filtering after passing through the channel. The receiving signal r is expressed as:

6. The chaotic communication method with noise reduction function according to claim 5, characterized in that: In step S4, the receiving end uses a preset M The vector of the first values ​​of the logistic sequence Build 2 M chaotic sequences, where j = 1, 2, ..., 2 M , the 2 M The chaotic sequences are all possible chaotic sequences used by the receiving end as the local noise-free reference signals of the receiving end.

7. The chaotic communication method with noise reduction function according to claim 6, characterized in that: Step S5 includes the following steps: S51. Construct channel quality detection variables for received signals The expression is as follows: in, is the transposed conjugate symbol, [L j,1 ,…,L j,β ] is a local noise-free reference signal at the receiving end generated according to the first value of the j-th preset Logistic sequence; S52. Calculation 2 M The label C with the largest value among the channel quality detection variables is as follows: S53. Convert C from decimal symbols to binary bits to obtain the estimated information bits of the first M information bits 8. The chaotic communication method with noise reduction function according to claim 7, characterized in that: In step S6, the decision variables of the remaining N information bits are calculated using the channel quality detection variables, and the process is as follows: like For information bit b t , the decision variable Φ t The formula is: like For information bit b t , the decision variable Φ t The formula is: Wherein, μ is the channel quality decision threshold coefficient, M+1≤t≤M+N.

9. The chaotic communication method with noise reduction function according to claim 8, characterized in that: In step S6, the estimated information bits of the last N information bits are estimated by using the decision variable, and the process includes: If Φ t ≥0, information bit b t Estimated information bits Estimated to be +1; if Φ t <0, then the information bit b t Estimated information bits Estimated to be -1.

10. A chaotic communication system with noise reduction function, comprising a transmitting end and a receiving end, characterized in that: The system includes a transmitting end for implementing the chaotic communication method with noise reduction function described in claim 1 and a receiving end for implementing the chaotic communication with noise reduction function described in claim 1.

Images