Multi-input multi-output permutation index differential chaos shift keying communication system and method

Abstract

The invention provides a multi-input multi-output permutation index differential chaos shift keying communication system and method, and relates to the technical field of chaos secret communication. Generating two paths of chaotic signals in the modulator, wherein one path is used as a reference signal; delaying the other path, performing mapping permutation by using the index bit, multiplying the modulation bit subjected to space-time coding by a reference signal copy generated by permutation, generating an information signal, combining the information signal with the reference signal, and sending the information signal to a demodulator; and the demodulator is used for respectively delaying and replacing the received transmission signal, carrying out correlation operation on the delayed receiving signal and the replaced receiving signal to obtain an output signal, and carrying out comparative judgment and space-time decoding to recover the index bit and the modulation bit. According to the method disclosed by the invention, the security and the information transmission rate of a communication system are improved through different index bit mapping selection permutation rule methods; and channel fading and noise are suppressed by using multiple antennas, so that the bit error rate performance of a communication system is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chaotic secure communication, and in particular to a multi-input multi-output permutation index differential chaotic shift keying communication system and method. Background Art

[0002] Chaotic communication is a research hotspot in digital communications. However, because carrier synchronization is difficult to implement in practical applications, research on chaotic communication has primarily focused on Differential Chaotic Shift Keying (DCSK) systems, which do not require chaotic synchronization. However, half of the time slots in DCSK systems are used to transmit reference signals that do not modulate data, resulting in low transmission rates.

[0003] To compensate for the low transmission rate of DCSK systems, some researchers have proposed the Permutation Index DCSK (PI-DCSK) system. This system multiplies the reference signal by a permutation matrix, which corresponds one-to-one with the number of mapped bits. This effectively increases the information transmission rate during transmission based on different permutation matrices. However, PI-DCSK systems do not utilize spatial dimensions to expand communication capabilities and enhance communication reliability, leaving significant room for improvement in their error-correction performance. Summary of the Invention

[0004] To address the shortcomings of the above-mentioned existing technologies, the present invention proposes a Multiple-Input Multiple-Output Substitution-Indexed Differential Chaotic Shift Keying (MIMO-PI-DCSK) communication system and method based on chaotic signal substitution, aiming to effectively reduce the bit error rate during the communication process.

[0005] The first aspect of the present invention provides a multi-input multi-output permutation index differential chaotic shift keying communication system, which includes: a modulator and a demodulator; the modulator and the demodulator transmit signals through a channel;

[0006] The modulator is configured to generate a chaotic signal and divide it into two paths, using one chaotic signal as a reference signal; delaying the other chaotic signal, setting data bits in the modulator and converting them into N-bit index bits and 1-bit modulation bit through serial-to-parallel conversion; mapping and permuting the delayed chaotic signal using the N-bit index bits to generate a reference signal replica; space-time encoding the 1-bit modulation bit and multiplying it with the reference signal replica to generate an information signal; combining the generated information signal and the reference signal to obtain a transmission signal, and transmitting the transmission signal to a demodulator using an antenna;

[0007] The demodulator is used to receive the transmission signal sent by the modulator to obtain a received signal, delay and permutate the received signal respectively, and perform correlation operations on the delayed received signal and the permuted received signal to obtain an output signal; perform maximum correlation peak detection and threshold judgment on the output signal to recover N-bit index bits; and then perform space-time decoding on the output signal containing the detected maximum correlation peak to recover 1 modulated bit.

[0008] Furthermore, the modulator further comprises:

[0009] A chaotic signal generator is used to generate a chaotic signal and transmit the generated chaotic signal to the modulator delay unit and the adder in two paths respectively;

[0010] The modulator delay unit delays the received chaotic signal using the spreading factor and transmits the delayed chaotic signal to the modulator replacement module;

[0011] A serial-to-parallel conversion unit is used to perform serial-to-parallel conversion on the preset data bits to obtain N-bit index bits and 1-bit modulation bit for parallel transmission, and transmit the N-bit index bits to the modulator replacement module and transmit the 1-bit modulation bit to the space-time encoder;

[0012] Modulator permutation module, used to map the received N-bit index bits to Among the permuted versions, and ensuring that all permuted versions meet the quasi-orthogonality, the delayed chaotic signal is permuted using the permuted versions to generate a reference signal copy and transmit it to the multiplier;

[0013] A space-time encoder is configured to map the received 1-bit modulation bit into a space-time coding matrix according to the selected space-time coding scheme, obtain the space-time coded modulation bit, and map it to the transmitting antenna; and transmit the space-time coded modulation bit to the multiplier at the same time;

[0014] a multiplier for multiplying the reference signal replica with the modulated bits after space-time coding to obtain an information signal and transmit it to the adder;

[0015] The adder is used to take the received chaotic signal as a reference signal and combine it with the information signal to obtain the transmission signal and select the corresponding transmitting antenna to transmit the transmission signal to the channel according to the mapping relationship between the modulation bits after space-time coding and the transmitting antenna.

[0016] Furthermore, the demodulator further comprises:

[0017] The demodulator delay unit is used to delay the received signal, generate a delayed received signal and transmit it to the correlator unit;

[0018] Demodulator replacement module, used to The received signal is permuted by the same permutation rule as in the modulator permutation module to generate Different received signal permutation versions are used as permuted received signals and transmitted to the correlator unit;

[0019] a correlator unit, configured to perform a correlation operation on the delayed received signal and the permuted received signal, sum the sum, obtain an output signal, and transmit the output signal to the decision comparator;

[0020] A decision comparator is used to compare and decide on the received output signal, determine the permutation index value corresponding to the maximum correlation peak through maximum correlation peak detection and threshold decision, and recover the N-bit index bit, while transmitting the output signal component corresponding to the maximum correlation peak to the space-time decoder;

[0021] The space-time decoder is used to perform space-time decoding on the output signal component corresponding to the maximum correlation peak, and then recover 1 modulated bit through threshold judgment.

[0022] The second aspect of the present invention proposes a multi-input multi-output permutation index differential chaotic shift keying communication method, which includes the following process:

[0023] The generated length is The chaotic signal is divided into two transmission paths, one path of chaotic signal is used as the reference signal, and the other path of chaotic signal is delayed by the spreading factor. , generating a delayed chaotic signal;

[0024] Set the data bits and obtain N index bits and 1 modulation bit for parallel transmission through serial-to-parallel conversion;

[0025] According to the N-bit index bit selection permutation rule, the delayed chaotic signal is permuted to generate a length of A copy of the reference signal;

[0026] Perform space-time coding on one modulated bit, generate space-time coded modulated bits, and map them to the transmit antennas;

[0027] Multiply the reference signal replica with the modulated bits after space-time coding to generate a length of information signal;

[0028] The transmission signal is obtained by concatenating the information signal and the reference signal. According to the mapping relationship between the modulated bits after space-time coding and the transmitting antenna, the corresponding transmitting antenna is selected to transmit the transmission signal from the transmitting end to the receiving end through the signal;

[0029] The receiving end receives the transmission signal from the sending end and generates an initial receiving signal;

[0030] Delay the initial received signal , get the delayed received signal;

[0031] performing substitution on the delayed received signal to generate a substituted received signal;

[0032] The received signal after substitution and the received signal after delay are compared. Second correlation operation, we get Independent correlation values ​​are summed to generate the output signal;

[0033] Perform maximum correlation peak detection and threshold judgment on the output signal, determine the permutation index value and output signal component corresponding to the maximum correlation peak, and restore the N-bit index bit according to the permutation index value corresponding to the maximum correlation peak;

[0034] The output signal component corresponding to the maximum correlation peak is space-time decoded to recover 1 modulated bit, and the demodulation is completed.

[0035] Furthermore, the N-bit index bits are a binary sequence consisting of 0 and 1, and the value of the 1-bit modulation bit is +1 or -1.

[0036] Furthermore, the method for replacing the delayed chaotic signal by selecting a replacement rule according to the N-bit index bit is:

[0037] For N-bit index bits, there is a corresponding permutation rules, each of which is formulated using a random matrix and a shift matrix; wherein the random matrix is ​​randomly transformed The position of the column vector in the unit matrix of order is generated; the shift matrix is ​​generated by The column vector in the identity matrix is ​​generated by shifting it right by one column;

[0038] Different shift matrices are mapped according to different index bits, and the permutation rule is obtained by multiplying the random matrix with the shift matrix;

[0039] according to The permutation rule maps the N-bit index bits to permuted versions and applied separately The delayed chaotic signal is permuted by a permuted version to generate a reference signal copy.

[0040] Furthermore, the specific contents of performing space-time coding on one modulation bit, generating the space-time coded modulation bit, and mapping it to the transmitting antenna are:

[0041] According to the selected space-time coding scheme, one modulation bit is mapped to the space-time coding matrix to obtain the space-time coded modulation bit;

[0042] The modulation bits after space-time coding are expressed as:

[0043]

[0044] in and All are modulation symbols; for The complex conjugate of for The complex conjugate of 、 、 and The value of is +1 or -1;

[0045] The modulated bits after space-time coding are transmitted in two consecutive symbol periods. and The signal is transmitted through two transmitting antennas. In the first symbol period Inside, and Transmitted simultaneously from antenna 1 and antenna 2; in the second symbol period Inside, Transmitted from antenna 1, Transmitted from antenna 2.

[0046] Furthermore, the specific content of replacing the delayed received signal is: obtaining the corresponding N-bit index bit in the process of replacing the delayed chaotic signal. permuted versions, traverse all permuted versions of the received signal, and apply all permuted versions to permute the delayed received signal to generate a permuted received signal.

[0047] The beneficial effects of adopting the above technical solution are:

[0048] Compared to existing technologies, the proposed Multiple-Input Multiple-Output Permutation Indexed Differential Chaotic Shift Keying (MIMO-PI-DCSK) system achieves coordinated optimization in terms of communication system reliability, security, and energy efficiency. By combining multi-antenna space-time coding technology and leveraging spatial diversity to suppress channel fading and noise interference, the proposed system systematically optimizes bit error performance in complex channel environments. By carrying additional information through permutation indexes, the proposed system increases the system's information transmission rate while avoiding the security risks associated with repeated transmission of traditional reference signals. This makes it difficult for non-cooperative parties to decipher the signal content through reverse engineering, thereby improving system security. Furthermore, the proposed method only transmits the reference chaotic signal once, saving transmission and reception costs. Therefore, the proposed system has strong practicality and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 : is a structural diagram of the MIMO-PI-DCSK communication system in this embodiment;

[0050] Figure 2 1 is a modulator structure diagram of the MIMO-PI-DCSK communication system in this embodiment;

[0051] Figure 3 1 is a structural diagram of a demodulator of a MIMO-PI-DCSK communication system in this embodiment;

[0052] Figure 4 Flowchart of the MIMO-PI-DCSK communication method in this embodiment;

[0053] Figure 5 Schematic diagram of the signal frame structure of the MIMO-PI-DCSK communication system in this embodiment;

[0054] Figure 6 This is a safety performance diagram of the MIMO-PI-DCSK communication system in this embodiment;

[0055] Figure 7 This is a diagram showing the impact of different modulation endings on the bit error performance of the MIMO-PI-DCSK communication system in this embodiment;

[0056] Figure 8 FIG. 4 is a diagram showing the impact of different half spreading factors on the bit error performance of the MIMO-PI-DCSK communication system in this embodiment. DETAILED DESCRIPTION

[0057] For ease of understanding of the present application, the specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly and comprehensively understood.

[0058] A multi-input multi-output permutation index differential chaotic shift keying communication system of this embodiment is as follows: Figure 1 As shown, the system includes: a modulator and a demodulator, wherein the modulator and the demodulator transmit signals through a channel;

[0059] The modulator is used to generate a chaotic signal and divide it into two paths, using one chaotic signal as a reference signal; delaying the other chaotic signal, setting data bits in the modulator and obtaining N-bit index bits and 1-bit modulation bit through serial-to-parallel conversion, mapping and permuting the delayed chaotic signal using the N-bit index bits to generate a reference signal replica; multiplying the 1-bit modulation bit with the reference signal replica after space-time coding to generate an information signal; combining the generated information signal and the reference signal to obtain a transmission signal, and sending the transmission signal to a demodulator using an antenna.

[0060] like Figure 1-2 As shown, the modulator in this embodiment includes a chaotic signal generator, a modulator delay unit, a modulator replacement module, a space-time encoder, a multiplier and an adder.

[0061] The chaotic signal generator is used for generating a chaotic signal and transmitting the generated chaotic signal to the modulator delay unit and the adder in two paths respectively.

[0062] In this embodiment, the signal generation principle of the chaotic signal generator includes the selection of a chaotic map and the selection of an initial value of the chaotic map, with the purpose of generating a chaotic signal.

[0063] The modulator delay unit delays the received chaotic signal using the spreading factor and transmits the delayed chaotic signal to the modulator replacement module.

[0064] In this embodiment, the modulator delay unit is used to transform the chaotic signal into a spreading factor. The value of the spreading factor is equal to the length of the generated chaotic signal.

[0065] The serial-to-parallel conversion unit is used to perform serial-to-parallel conversion on the preset data bits to obtain N-bit index bits and 1-bit modulation bit for parallel transmission, and transmit the N-bit index bits to the modulator replacement module and transmit the 1-bit modulation bit to the space-time encoder.

[0066] Modulator permutation module, used to map the received N-bit index bits to The delayed chaotic signal is permuted using the permuted versions, and the reference signal replica is generated and transmitted to the multiplier.

[0067] In this embodiment, the purpose of permutation is to reduce the correlation between the reference signal and the information signal, and at the same time, to use the permutation rule to carry additional information data, thereby improving the security performance and transmission efficiency of the system. The number of permutators in the modulator permutation module is 1, and the number of permutation rules is The number of generated replacement versions is also The corresponding permutation versions generated by the permutator can perform permutation operations on the chaotic signal, and each permutation version satisfies quasi-orthogonality. The permuted reference signal copy generated by the permutator is transmitted to the multiplier.

[0068] The space-time encoder is used to map the received 1-bit modulation bit into the space-time coding matrix according to the selected space-time coding scheme, obtain the space-time coded modulation bit and map it to the transmitting antenna; at the same time, the space-time coded modulation bit is transmitted to the multiplier.

[0069] In this embodiment, the space-time encoder performs coding in both the spatial and time domains to achieve diversity gain and reduce the system's bit error rate. The space-time encoder generates a coding matrix based on the additional symbols selected for coding, maps it to the transmit antennas, and transmits the modulated bits after space-time coding to the multiplier.

[0070] The multiplier is used to multiply the reference signal replica with the modulated bits after space-time coding to obtain an information signal and transmit it to the adder.

[0071] The adder is used to take the received chaotic signal as a reference signal and combine it with the information signal to obtain the transmission signal and select the corresponding transmitting antenna to transmit the transmission signal to the channel according to the mapping relationship between the modulation bits after space-time coding and the transmitting antenna.

[0072] The demodulator is used to receive the transmission signal sent by the modulator to obtain a received signal, delay and permutate the received signal respectively, and perform correlation operations on the delayed received signal and the permuted received signal to obtain an output signal; perform maximum correlation peak detection and threshold judgment on the output signal to recover N-bit index bits; and then perform space-time decoding on the output signal containing the detected maximum correlation peak to recover 1 modulated bit.

[0073] like Figure 1 and Figure 3 As shown, the demodulator of this embodiment includes a demodulator delay unit, a demodulator replacement module, a correlator unit, a decision comparator, and a space-time decoder.

[0074] The demodulator delay unit is used to delay the received signal, generate a delayed received signal and transmit it to the correlator unit.

[0075] Demodulator replacement module, used to The received signal is permuted by the same permutation rule as in the modulator permutation module to generate Different permuted versions of the received signal are used as permuted received signals and transmitted to the correlator unit.

[0076] In this embodiment, the permutation rules in the demodulator permutation module are the same as those in the modulator permutation module. All permutation rules are traversed to generate Different received signal replacement versions are used as the replaced received signals.

[0077] The correlator unit is used to perform correlation operation on the delayed received signal and the replaced received signal and sum them up to obtain an output signal and transmit it to the decision comparator.

[0078] In this embodiment, since all permutation rules are traversed in the permutator unit, Different received signal permutation versions, respectively The permuted received signal and the delayed received signal are correlated and summed to obtain The output signal is transmitted to the decision comparator.

[0079] The decision comparator is used to compare and judge the received output signal, determine the permutation index value corresponding to the maximum correlation peak through maximum correlation peak detection and threshold judgment, and restore the N-bit index bit, while transmitting the output signal component corresponding to the maximum correlation peak to the space-time decoder.

[0080] In this embodiment, if Figure 3 As shown, a threshold decision is performed on the correlation value peak detected by the maximum correlation peak to obtain the replacement index value corresponding to the maximum correlation peak and the output signal component corresponding to the maximum correlation peak, and the index bit is restored according to the replacement index value corresponding to the maximum correlation peak.

[0081] The space-time decoder is used to perform space-time decoding on the output signal component corresponding to the maximum correlation peak, and then recover 1 modulated bit through threshold decision.

[0082] In this embodiment, if Figure 3 As shown, the space-time decoder is responsible for recovering the transmitted 1-bit modulation bit from the received output signal.

[0083] A multi-input multi-output permutation index differential chaotic shift keying communication method of this embodiment is as follows: Figure 4 As shown, the method includes the following processes:

[0084] The generated length is The chaotic signal is divided into two transmission paths, one path of chaotic signal is used as the reference signal, and the other path of chaotic signal is delayed by the spreading factor. , generating a delayed chaotic signal.

[0085] In this embodiment, the generated length is The chaotic signal of the i-th item in the k-th frame chaotic signal is expressed as .

[0086] The data bits are set and serial-to-parallel conversion is performed to obtain N index bits and 1 modulation bit for parallel transmission.

[0087] In this embodiment, if Figure 2 As shown, the data bits are set and two sets of parallel data bits are obtained by serial-to-parallel conversion, namely, N-bit index bits for permutation and 1-bit modulation bits as space-time block codes. The N-bit index bits are binary sequences consisting of 0 and 1, and the N-bit index bits correspond to The substitution method is to transform the position of the chaotic signal according to a certain rule. The value of the 1-bit modulation bit is +1 or -1.

[0088] According to the N-bit index bit selection permutation rule, the delayed chaotic signal is permuted to generate a length of A copy of the reference signal.

[0089] The method for replacing the delayed chaotic signal by selecting a replacement rule according to the N-bit index bit is:

[0090] For N index bits, there is a corresponding permutation rules, each of which is formulated using a random matrix and a shift matrix; wherein the random matrix is ​​randomly transformed The position of the column vector in the unit matrix of order is generated; the shift matrix is ​​generated by The column vector in the identity matrix of order is generated by shifting it right by one column.

[0091] Different shift matrices are mapped according to different index bits, and a permutation rule is obtained by multiplying the random matrix with the shift matrix.

[0092] In this embodiment, the permutation adopts random matrix and shift matrix to formulate rules. By The position of the column vector of the unit matrix of the order is randomly transformed, and the shift matrix is ​​generated for The unit matrix of order is shifted right by one column and is expressed as:

[0093] (1)

[0094] The random matrix With the shift matrix The permutation matrix is ​​obtained by multiplication, and the permutation matrix is ​​used as a permutation rule. Different shift matrices are mapped according to different index bits to achieve quasi-orthogonal permutation rule arrangement.

[0095] according to The permutation rule maps the N-bit index bits to permuted versions and applied separately The delayed chaotic signal is permuted by a permuted version, and the generated length is A copy of the reference signal.

[0096] In this embodiment, the N-bit index bits are transmitted in the chaotic signal after the permutation index, and the generated length is A copy of the reference signal. Figure 5 As shown, taking the i-th chaotic signal of the k-th chaotic signal as an example, the chaotic signal after permutation index is expressed as ,in Indicates that antenna 1 selects the permutation index transformation, Represents the i-th chaotic signal of the k-th frame chaotic signal.

[0097] Perform space-time coding on one modulated bit to generate a space-time coded modulated bit and map it to the transmitting antenna.

[0098] In this embodiment, the modulated bits are input into a space-time encoder for encoding to achieve transmit diversity.

[0099] The specific contents of performing space-time coding on a 1-bit modulation bit, generating a modulation bit after space-time coding, and mapping it to a transmitting antenna are as follows:

[0100] According to the selected space-time coding scheme, one modulation bit is mapped into the space-time coding matrix to obtain the space-time coded modulation bit.

[0101] The modulation bits after space-time coding are expressed as:

[0102] (2)

[0103] in and All are modulation symbols; for The complex conjugate of for The complex conjugate of 、 、 and The value of is +1 or -1.

[0104] The modulated bits after space-time coding are transmitted in two consecutive symbol periods. and The signal is transmitted through two transmitting antennas. In the first symbol period Inside, and Transmitted simultaneously from antenna 1 and antenna 2; in the second symbol period Inside, Transmitted from antenna 1, Transmitted from antenna 2.

[0105] The transmission sequences of antenna 1 and antenna 2 are respectively and Indicates that:

[0106] (3)

[0107] Multiply the reference signal replica with the modulated bits after space-time coding to generate a length of information signal.

[0108] The transmission signal is obtained by splicing the generated information signal and the reference signal. According to the mapping relationship between the modulated bits after space-time coding and the transmitting antenna, the corresponding transmitting antenna is selected to transmit the transmission signal from the transmitting end to the receiving end through the signal.

[0109] In this embodiment, the reference signal and the information signal are combined to generate a transmission signal, wherein the transmission signal sent by antenna 1 is expressed as:

[0110] (4)

[0111] in represents the i-th frame transmission signal; k represents the k-th frame signal; i represents the i-th chaotic signal in the k-th frame signal; , , Respectively represent the i-th delay in the k-th frame signal , delay , delay chaotic signals; represents the permutation matrix corresponding to the j-th permutation rule of the k-th frame; and Indicates the index bit corresponding to the space-time coding of the k-th frame signal, and the value is +1 or -1.

[0112] The receiving end receives the transmission signal from the sending end and generates an initial receiving signal.

[0113] In this embodiment, the signal is transmitted between the transmitting end and the receiving end through the channel. Antenna 1 and antenna 2 respectively pass through the channel gain. The channel model is used Indicates that ,in Indicates the transmit antenna index; Indicates the receiving antenna index; taking receiving antenna 1 in the first symbol period as an example, the initial received signal is expressed as:

[0114] (5)

[0115] in is the kth initial received signal in the i-th frame signal; is the channel gain from transmit antenna 1 to receive antenna 1; is the channel gain from transmit antenna 2 to receive antenna 1; The mean is 0 and the variance is Gaussian white noise.

[0116] Delay the initial received signal , and get the delayed received signal.

[0117] The delayed received signal is permuted to generate a permuted received signal.

[0118] The specific content of replacing the delayed received signal is:

[0119] Obtain the corresponding N-bit index bit in the process of replacing the delayed chaotic signal permuted versions, traverse all permuted versions of the received signal, and apply all permuted versions to permute the delayed received signal to generate a permuted received signal.

[0120] The received signal after substitution and the received signal after delay are compared. Second correlation operation, we get The output signal is generated by summing the independent correlation values.

[0121] In this embodiment, the method of traversing all permutations of the received signal is the same as the method of permuting the chaotic signal. For example, the output signal of the receiving antenna 1 in the first symbol period is expressed as:

[0122] (6)

[0123] in is the output signal of the k-th frame signal after being processed by the permutator and the correlator; The first receiving antenna permutation rule matrices, where ; is the delayed received signal of the i-th frame in the k-th frame signal.

[0124] Perform maximum correlation peak detection and threshold judgment on the output signal, determine the permutation index value and output signal component corresponding to the maximum correlation peak, and restore N index bits according to the permutation index value corresponding to the maximum correlation peak.

[0125] The output signal component corresponding to the maximum correlation peak is space-time decoded to recover 1 modulated bit, and the demodulation is completed.

[0126] In this embodiment, a decision comparator is used to compare and decide the input correlation values, and the replacement index value of the maximum correlation peak is restored to an N-bit index bit; the output signal of the maximum correlation peak is space-time decoded to obtain a restored 1-bit modulation bit, and the demodulation is completed.

[0127] In order to verify the technical effect of the method of the present invention, the present embodiment is tested and verified as follows:

[0128] Since the permutation module is used in the MIMO-PI-DCSK system, the correlation between the reference signal and the information signal of the system is weakened. The MIMO-PI-DCSK system improves the correlation problem of the information signal in the DCSK system by permuting the reference signal to disrupt the order of the reference signal, thereby reducing the correlation between the reference signal and the information signal. The square amplitude spectrum simulation verification is as follows: Figure 6 As shown in the figure, the spectrum value does not have zero points at odd multiples of the bit rate, the energy density of the spectrum is more uniform, and the security performance is greatly improved. The MIMO-PI-DCSK system has a better detection probability and communication confidentiality.

[0129] Analyze the impact of different modulation orders M on system performance: Figure 7 As shown in the figure, the modulation order M is 8, 16, and 32 respectively to better express the effect. When M increases, the transmission energy remains unchanged, and the number of index mapping bits of each data block in MIMO-PI-DCSK increases, thereby achieving good performance and proving the improvement of the system's transmission efficiency.

[0130] Analysis of the impact of half spreading factor on system performance: In order to explore the impact of half spreading factor on system performance, according to the control variable method, the initial value of the chaotic map used is 0.4, and the half spreading factor uses three sets of data of 100, 200, and 300 respectively to verify the impact of half spreading factor on MIMO-PI-DCSK system. Figure 8As shown in the figure, using improved Logistic mapping, for the MIMO-PI-DCSK system, when the selected half spreading factor is small, the bit error rate is better; as the half spreading factor increases, the system's bit error performance is relatively weakened.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the claims of the present invention.

Claims

1. A multi-input multi-output permutation index differential chaotic shift keying communication system, characterized in that: The system includes: a modulator and a demodulator, wherein the modulator and the demodulator transmit signals through a channel; The modulator is configured to generate a chaotic signal and divide it into two paths, using one chaotic signal as a reference signal; delaying the other chaotic signal, setting data bits in the modulator and converting them into N-bit index bits and 1-bit modulation bit through serial-to-parallel conversion; mapping and permuting the delayed chaotic signal using the N-bit index bits to generate a reference signal replica; space-time encoding the 1-bit modulation bit and multiplying it with the reference signal replica to generate an information signal; combining the generated information signal and the reference signal to obtain a transmission signal, and transmitting the transmission signal to a demodulator using an antenna; The demodulator is used to receive the transmission signal sent by the modulator to obtain a received signal, delay and permutate the received signal respectively, and perform correlation operations on the delayed received signal and the permuted received signal to obtain an output signal; perform maximum correlation peak detection and threshold judgment on the output signal to recover N-bit index bits; and then perform space-time decoding on the output signal containing the detected maximum correlation peak to recover 1 modulated bit.

2. The multi-input multi-output permutation index differential chaotic shift keying communication system according to claim 1, characterized in that: The modulator further comprises: A chaotic signal generator is used to generate a chaotic signal and transmit the generated chaotic signal to the modulator delay unit and the adder in two paths respectively; The modulator delay unit delays the received chaotic signal using the spreading factor and transmits the delayed chaotic signal to the modulator replacement module; A serial-to-parallel conversion unit is used to perform serial-to-parallel conversion on the preset data bits to obtain N-bit index bits and 1-bit modulation bit for parallel transmission, and transmit the N-bit index bits to the modulator replacement module and transmit the 1-bit modulation bit to the space-time encoder; Modulator permutation module, used to map the received N-bit index bits to Among the permuted versions, and ensuring that all permuted versions meet the quasi-orthogonality, the delayed chaotic signal is permuted using the permuted versions to generate a reference signal copy and transmit it to the multiplier; A space-time encoder is configured to map the received 1-bit modulation bit into a space-time coding matrix according to the selected space-time coding scheme, obtain the space-time coded modulation bit, and map it to the transmitting antenna; and transmit the space-time coded modulation bit to the multiplier at the same time; a multiplier for multiplying the reference signal replica with the modulated bits after space-time coding to obtain an information signal and transmit it to the adder; The adder is used to take the received chaotic signal as a reference signal and combine it with the information signal to obtain the transmission signal and select the corresponding transmitting antenna to transmit the transmission signal to the channel according to the mapping relationship between the modulation bits after space-time coding and the transmitting antenna.

3. The multi-input multi-output permutation index differential chaotic shift keying communication system according to claim 2, characterized in that: The demodulator further comprises: The demodulator delay unit is used to delay the received signal, generate a delayed received signal and transmit it to the correlator unit; Demodulator replacement module, used to The received signal is permuted by the same permutation rule as in the modulator permutation module to generate Different received signal permutation versions are used as permuted received signals and transmitted to the correlator unit; a correlator unit, configured to perform a correlation operation on the delayed received signal and the permuted received signal, sum the sum, obtain an output signal, and transmit the output signal to the decision comparator; A decision comparator is used to compare and decide on the received output signal, determine the permutation index value corresponding to the maximum correlation peak through maximum correlation peak detection and threshold decision, and recover the N-bit index bit, while transmitting the output signal component corresponding to the maximum correlation peak to the space-time decoder; The space-time decoder is used to perform space-time decoding on the output signal component corresponding to the maximum correlation peak, and then recover 1 modulated bit through threshold judgment.

4. A multi-input multi-output permutation index differential chaotic shift keying communication method, characterized in that: The steps include: The generated length is The chaotic signal is divided into two transmission paths, one path of chaotic signal is used as the reference signal, and the other path of chaotic signal is delayed by the spreading factor. , generating a delayed chaotic signal; Set the data bits and obtain N index bits and 1 modulation bit for parallel transmission through serial-to-parallel conversion; According to the N-bit index bit selection permutation rule, the delayed chaotic signal is permuted to generate a length of A copy of the reference signal; Perform space-time coding on one modulated bit, generate space-time coded modulated bits, and map them to the transmit antennas; Multiply the reference signal replica with the modulated bits after space-time coding to generate a length of information signal; The transmission signal is obtained by concatenating the information signal and the reference signal. According to the mapping relationship between the modulated bits after space-time coding and the transmitting antenna, the corresponding transmitting antenna is selected to transmit the transmission signal from the transmitting end to the receiving end through the signal; The receiving end receives the transmission signal from the sending end and generates an initial receiving signal; Delay the initial received signal , get the delayed received signal; performing substitution on the delayed received signal to generate a substitution received signal; The received signal after substitution and the received signal after delay are compared. Second correlation operation, we get Independent correlation values ​​are summed to generate the output signal; Perform maximum correlation peak detection and threshold judgment on the output signal, determine the permutation index value and output signal component corresponding to the maximum correlation peak, and restore the N-bit index bit according to the permutation index value corresponding to the maximum correlation peak; The output signal component corresponding to the maximum correlation peak is space-time decoded to recover 1 modulated bit, and the demodulation is completed.

5. The multi-input multi-output permutation index differential chaotic shift keying communication method according to claim 4, characterized in that: The N-bit index bits are a binary sequence consisting of 0 and 1, and the value of the 1-bit modulation bit is +1 or -1.

6. The multi-input multi-output permutation index differential chaotic shift keying communication method according to claim 5, characterized in that: The method for replacing the delayed chaotic signal by selecting a replacement rule according to the N-bit index bit is: For N index bits, there is a corresponding permutation rules, each of which is formulated using a random matrix and a shift matrix; wherein the random matrix is ​​randomly transformed The position of the column vector in the unit matrix of order is generated; the shift matrix is ​​generated by The column vector in the identity matrix is ​​generated by shifting it right by one column; Different shift matrices are mapped according to different index bits, and the permutation rule is obtained by multiplying the random matrix with the shift matrix; according to The permutation rule maps the N-bit index bits to permuted versions and applied separately The delayed chaotic signal is permuted by a permuted version to generate a reference signal copy.

7. The multi-input multi-output permutation index differential chaotic shift keying communication method according to claim 6, characterized in that: The specific contents of performing space-time coding on a 1-bit modulation bit, generating a modulation bit after space-time coding, and mapping it to a transmitting antenna are as follows: According to the selected space-time coding scheme, one modulation bit is mapped to the space-time coding matrix to obtain the space-time coded modulation bit; The modulation bits after space-time coding are expressed as: ； in and All are modulation symbols; for The complex conjugate of for The complex conjugate of 、 、 and The value of is +1 or -1; the modulated bits after space-time coding are in two consecutive symbol periods and The signal is transmitted through two transmitting antennas. In the first symbol period Inside, and Transmitted simultaneously from antenna 1 and antenna 2; in the second symbol period Inside, Transmitted from antenna 1, Transmitted from antenna 2.

8. The multi-input multi-output permutation index differential chaotic shift keying communication method according to claim 7, characterized in that: The specific content of replacing the delayed received signal is: obtaining the corresponding N-bit index bit in the process of replacing the delayed chaotic signal. permuted versions, traverse all permuted versions of the received signal, and apply all permuted versions to permute the delayed received signal to generate a permuted received signal.

Images