Multi-carrier multi-system differential chaos shift keying modulation and demodulation method and system based on improved code index modulation

Abstract

The invention discloses a multi-carrier multi-system differential chaos shift keying modulation and demodulation method and system based on improved code index modulation, and relates to the technical field of communication signal processing. The method comprises the following steps: at a sending end, converting information to be transmitted into N groups of parallel information, dividing each group into index bits and modulation bits, converting each group of index bits into decimal numbers, and modulating the modulation bits; acquiring a reference signal; the reference signal and the information signal are multiplied by a carrier and transmitted into a channel. At a receiving end, the reference signal and the information signal are recovered through multi-carrier demodulation; the method comprises the following steps: multiplying an information signal by a Walsh code, performing related demodulation on a sequence of a reference signal and the information signal, obtaining a sequence number with maximum energy in the information signal, recovering a code index value, converting the code index value into a binary number, recovering an index bit, obtaining a related demodulation result, demodulating and recovering a modulation bit, and outputting original information after conversion. According to the invention, the problems of high bit error rate, poor bit error rate performance and low data rate of the existing MC-DCSK modulation and demodulation method can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of communication signal processing, and in particular to a multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method and system based on improved code index modulation. Background Art

[0002] Chaotic digital modulation technology can not only retain the low intercept probability and multipath effect mitigation characteristics of traditional spread spectrum communication systems, but also show unique advantages in many other aspects, including: reducing the hardware cost of the system; improving communication security; being suitable for effectively distinguishing different users in a multi-user environment; improving the performance of spread spectrum communication systems, etc. Therefore, chaotic digital modulation technology has become one of the hot issues of concern and research in the nonlinear science and information science community.

[0003] Due to the lack of reliable and effective methods to achieve chaotic synchronization at the receiving end, most of the existing chaotic digital modulation and demodulation methods are based on the transmission reference method, that is, both the carrier signal and the signal carrying information are sent to the receiving end. Among them, the differential chaos shift keying (DCSK) modulation and demodulation method does not need to complete channel estimation, and can obtain good error performance. It has shown strong competitiveness in many practical applications (including wireless personal area networks, wireless sensor networks, etc.). However, in order to ensure the orthogonality between the reference signal and the information signal, DCSK transmits these two signals in different time periods, so both the transmitter and the receiver must use delay units. In ultra-wideband transmission, it is almost impossible to integrate analog delay units using existing processes, and delay units implemented in digital mode will consume huge power.

[0004] To address the above problems, the Multi-Carrier Differential Chaos Shift Keying (MC-DCSK) modulation and demodulation method uses multiple subcarriers to simultaneously transmit reference signals and multiple information signals, and uses different subcarriers to distinguish the reference signal from each information signal. Among all the subcarriers, only one subcarrier is allocated to the reference signal, and all the remaining subcarriers are allocated to the information signal, and each information signal occupies one subcarrier. Although MC-DCSK eliminates the delay unit in the transceiver, compared with the traditional Binary Phase Shift Keying (BPSK), the bit error rate of MC-DCSK is still high, and the bit error performance is not ideal. Summary of the invention

[0005] One of the purposes of the present invention is to provide a multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method based on improved code index modulation to solve the problems of high bit error rate, poor bit error performance and low data rate of the existing MC-DCSK modulation and demodulation method.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: a multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method based on improved code index modulation,

[0007] On the sending side:

[0008] The information to be transmitted is converted into N groups of parallel information through serial-to-parallel conversion, and each group of information is divided into p1 index bits and p2 modulation bits; each group of index bits is converted into a decimal number Q through a binary-to-decimal converter n , and then this decimal number Q n Enter the Walsh code selector and select the 2D n +1 and 2D n +2 Walsh codes, using W xn and W yn Indicates that, reuse W xn and W yn The chaotic signal is generated by the chaotic generator and combined with the Walsh code W R (R≠xn, and R≠yn) is Krone product multiplied to obtain a reference signal; 1 reference signal and N information signals are both passed through a pulse shaping filter, and then multiplied with N+1 carriers respectively, and then sent to the channel;

[0009] On the receiving end:

[0010] After multi-carrier demodulation, the reference signal and N information signals are recovered respectively; each information signal is multiplied with Q Walsh codes, and the averaged reference signal sequence is correlated and demodulated with the averaged N information signal sequences respectively. Each information signal then passes through an energy comparator to find the sequence number with the largest energy, and the code index value is recovered based on this sequence number. The decimal to binary converter is then used to obtain the recovered index bit, and the corresponding correlation demodulation result is selected based on the code index value with the largest energy. This result is demodulated by multi-base DCSK to recover the modulated bits, and finally the original information is output through parallel-to-serial conversion.

[0011] Among them, at the transmitting end, signal modulation includes the following steps:

[0012] Step 1: Perform serial-to-parallel conversion on the input information signal and divide it into N groups of information, each group of information includes two parts: p1 index bits and p2 modulation bits;

[0013] Step 2: Pass the N groups of index bits through the binary to decimal converter to obtain Q n ;

[0014] Step 3: Convert the decimal number Q n Enter into the Walsh code selector and select 2 different Walsh codes, one of which uses W xn Indicates that the other one is W yn Indicates; where xn = 2D n +1,yn=2D n +2;

[0015] Step 4: Pass the N groups of modulated bits through the bit-to-symbol converter to obtain the corresponding constellation symbol S n , where S n =a n +jb n ;

[0016] Step 5: Generate a Logistic chaotic signal of length θ: c = [c1, c2, …c θ ];

[0017] Step 6: Compare the result of step 5 with the Walsh code W R Perform Kronecker product multiplication;

[0018] Step 7: Combine each group of two different Walsh codes obtained in step 3 with the chaotic signal c = [c1, c2, ... c θ ] are multiplied, here it is the Kronecker product;

[0019] Step 8: Multiply the result of step 7 by the result of step 4, that is

[0020] Step 9: Pass the results of step 6 and step 8 through the pulse shaping filter to obtain c R (t) and m n (t), where

[0021] Step 10: Place c R (t) is multiplied by the reference carrier f0 to obtain the reference signal at the transmitter: c R (t)cos(2πf0t), send it to the channel;

[0022] Step 11: Place m n (t) respectively with N carriers (f1, f2…f N ) to obtain the information signal sent by the transmitter: Send it to the channel.

[0023] Among them, at the receiving end, signal demodulation includes the following steps:

[0024] Step 12: Multiply the received reference signal with the synchronized reference carrier f0 to obtain a product signal, which is then passed through a matched filter and then sampled in the time domain;

[0025] Step 13: The received information signal is respectively synchronized with the N carriers (f1, f2…f N ) are multiplied, then pass through a matched filter, and then perform time domain sampling to obtain N groups of sampling signals;

[0026] Step 14: Combine the result of step 12 with the expanded Walsh sequence W R Multiply and average them piecewise to get the restored reference signal r R ;

[0027] Step 15: Compare each group of signals in the result of step 13 with the extended Walsh sequence W1, W2, ..., W Q Multiply them, and then average them in sections to get the signal

[0028]

[0029] Step 16: Correlate the result of step 14 with the result of step 15, and then take the absolute value;

[0030] Step 17: Compare the energy of each group of results obtained in step 16 to find the sequence value with the maximum energy;

[0031] Step 18: Input the result of step 17 into the code index detector to obtain the decimal number of the sequence, and then pass it through a decimal to binary converter to obtain the recovered index bit;

[0032] Step 19: According to the result of step 17, find the correlation result corresponding to the sequence with the maximum energy, and perform multi-level DCSK demodulation on the correlation result;

[0033] Step 20: Convert the result of step 19 from symbol to bit to obtain the restored modulated bits;

[0034] Step 21: Combine the index bit obtained in step 18 and the modulation bit obtained in step 20 and then perform parallel-to-serial conversion to restore the original information signal.

[0035] On the other hand, the present invention also relates to a multi-carrier multi-ary differential chaotic shift keying modulation and demodulation system based on improved code index modulation, which includes a transmitting end (modulator) and a receiving end (demodulator), and the transmitting end and the receiving end adopt the above-mentioned method to modulate and demodulate the signal.

[0036] The transmitting end modulates the input information signal according to the method of steps 1 to 11 above.

[0037] The receiving end demodulates the received signal according to the method from step 12 to step 21 above.

[0038] In one embodiment of the present invention, the transmitting end includes:

[0039] Serial-to-parallel conversion circuit, chaotic signal generator, N binary to decimal converters, N Walsh sequence selectors, 2N+1 Walsh sequence multipliers, N bit to symbol converters, N multi-base DCSK modulators, N+1 pulse shaping filters, and N+1 carrier multipliers.

[0040] The serial-to-parallel conversion circuit is used to convert the serial data bits to be transmitted within the current symbol time into parallel data bits; the chaotic signal generator is used to generate a discrete chaotic signal sequence; the N binary-to-decimal converters are used to convert the binary of the index bit into a decimal number; the N Walsh sequence selectors are used to select 2 Walsh sequences according to the results of the binary-to-decimal converters; the 2N+1 Walsh sequence multipliers are used to perform Kronecker product multiplication on the selected Walsh sequence and the discrete chaotic signal; the N bit-to-symbol converters are used to convert the modulated bits into constellation symbols; the N multi-level DCSK modulators are used to implement multi-level DCSK modulation; the N+1 pulse shaping filters are used to perform pulse shaping filtering on the reference signal and the N groups of information signals respectively; and the N+1 carrier multipliers are used to multiply the results of the N+1 pulse shaping filters by the N+1 carriers.

[0041] In one embodiment of the present invention, the receiving end includes:

[0042] N+1 carrier multipliers, N+1 matching filters, N+1 sampling switches, 1 Walsh reference sequence multiplier, NQ Walsh information sequence multipliers, NQ correlators, N energy comparators, N code index detectors, N decimal to binary converters, N selectors, N multi-base DCSK demodulators, N symbol bit conversion circuits and parallel-to-serial conversion circuits.

[0043] The N+1 carrier multipliers are used to multiply the received signals with the N+1 synchronized subcarriers respectively to obtain N+1 product signals; the N+1 matched filters are used to perform matched filtering on the N+1 product signals respectively; the N+1 sampling switches are used to perform time domain sampling on the N+1 product signals after the matched filtering to recover 1 discrete reference signal sequence and N discrete information signal sequences; the 1 Walsh reference sequence multiplier is used to multiply the result of the reference signal after the sampling switch with the extended Walsh reference sequence, and then average it in sections to obtain the recovered reference signal; the NQ Walsh information sequence multipliers are used to multiply the N groups of information signals with the Q extended Walsh sequences respectively, and then average it in sections; the NQ correlators are used to average the recovered reference signal with each group of information signals. The N energy comparators are used to compare the energies of the N signals and find the sequence value with the maximum energy; the N code index detectors are used to save the sequence value with the maximum energy; the N decimal-to-binary converters are used to convert the sequence value with the maximum energy into a binary number, so as to demodulate the index bit; the N selectors are used to select the correlation value of the corresponding sequence according to the result of the code index detector; the N multi-base DCSK demodulators are used to perform multi-base DCSK demodulation on the N correlation values; the N symbol bit conversion circuits are used to convert the results of the N multi-base DCSK demodulators into modulation bits; the parallel-to-serial conversion circuit is used to combine the obtained N index bits and modulation bits respectively and then merge them into 1 serial demodulation data bit and output it.

[0044] The multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method based on improved code index modulation provided by the present invention transmits information through the MDCSK constellation and the carrier number, which greatly improves the data transmission rate and energy efficiency of the system. In addition, the present invention adopts improved code index modulation at the transmitting end and improved code index demodulation at the receiving end, which greatly improves the data rate and reduces energy consumption. At the same time, the method adopted by the present invention can avoid the use of delay units in the receiving end and the transmitting end, effectively reduce the noise component in the decision variable of the receiving end, improve the bit error performance of the system, and thus obtain a lower bit error rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A schematic diagram of a flow chart of a modulation and demodulation method according to an embodiment;

[0046] Figure 2 Schematic diagram of the structure of the transmitting end (modulator) in the embodiment;

[0047] Figure 3 Schematic diagram of the structure of a receiving end (demodulator) in an embodiment;

[0048] Figure 4 The figure is a comparison diagram of the bit error performance of the modulation and demodulation method involved in the embodiment and the existing HDR-CI-DCSK method in an additive white Gaussian noise channel. DETAILED DESCRIPTION

[0049] To facilitate understanding by those skilled in the art, the present invention is further described below in conjunction with embodiments and drawings.

[0050] In general, the present invention first converts the information to be transmitted into N groups of parallel information through serial-to-parallel conversion, and divides each group of information into p1 index bits and p2 modulation bits, wherein each group of index bits is converted into a decimal number Q through a binary-to-decimal converter n , and then this decimal number Q n Enter the Walsh code selector and select the 2D n +1 and 2D n +2 Walsh codes, using W xn and W yn Indicates that, reuse W xn and W yn The chaotic signal is generated by the chaotic generator and combined with the Walsh code W R (R≠xn, and R≠yn) is Kronen product multiplied to obtain the reference signal; the 1-way reference signal and the N-way information signal are respectively multiplied with N+1 carriers after passing through the pulse shaping filter and then sent to the channel. At the receiving end, after multi-carrier demodulation, the reference signal and the N-way information signal are respectively recovered; each information signal is multiplied with Q Walsh codes, and the averaged reference signal sequence is correlated demodulated with the averaged N-way information signal sequence. Each information signal is then passed through an energy comparator to find the sequence number with the largest energy, and the code index value is recovered based on this sequence number. Then, a decimal to binary converter is used to obtain the recovered index bit, and the corresponding correlation demodulation result is selected based on the code index value with the largest energy. This result is demodulated by multi-base DCSK to recover the modulation bit, and finally the original information is output through parallel-to-serial conversion.

[0051] Figure 1 The process of a multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method based on improved code index modulation is shown, which mainly includes the following steps:

[0052] On the sending side:

[0053] Step 1: Perform serial-to-parallel conversion on the input information signal and divide it into N groups of information, each group of information includes two parts: p1 index bits and p2 modulation bits;

[0054] Step 2: Pass the N groups of index bits through the binary to decimal converter to obtain Q n ;

[0055] Step 3: Convert the decimal number Q n Enter into the Walsh code selector and select 2 different Walsh codes, one of which uses W xn Indicates that the other one is W yn Indicates; where xn = 2D n +1,yn=2D n +2;

[0056] Step 4: Pass the N groups of modulated bits through the bit-to-symbol converter to obtain the constellation symbol S corresponding to each group n =a n +jb n ;

[0057] Step 5: Generate a Logistic chaotic signal of length θ, c = [c1, c2, …c θ ];

[0058] Step 6: Compare the result of step 5 with the Walsh code W R Perform Kronecker product multiplication, where the Walsh code is generated by a 64*64 Hadamard matrix;

[0059] Step 7: Combine each group of two different Walsh codes obtained in step 3 with the chaotic signal c = [c1, c2, ... c θ ] are multiplied, here it is the Kronecker product;

[0060] Step 8: Multiply the result of step 7 by the result of step 4, that is

[0061] Step 9: Pass the results of step 6 and step 8 through the pulse shaping filter to obtain c R (t) and m n (t); of which:

[0062] Step 10: Place c R (t) is multiplied by the reference carrier f0 to obtain the reference signal at the transmitter: c R (t)cos(2πf0t);

[0063] Step 11: Place m n (t) respectively with N carriers (f1, f2…f N ) to obtain the information signal sent by the transmitter:

[0064] On the receiving end:

[0065] Step 12: Receive the reference signal sent in step 10, multiply it with the synchronized reference carrier f0 to obtain a product signal, pass it through a matched filter, and then perform time domain sampling;

[0066] Step 13: Receive the information signal sent in step 11 and synchronize it with the N synchronized carriers (f1, f2…f N ) are multiplied, then pass through a matched filter, and then perform time domain sampling to obtain N groups of sampling signals;

[0067] Step 14: Combine the result of step 12 with the expanded Walsh sequence W R Multiply and average them piecewise to get the restored reference signal r R ;

[0068] Step 15: Compare each group of signals in the result of step 13 with the extended Walsh sequence W1, W2, ..., W Q Multiply them, and then average them in sections to get the signal

[0069]

[0070] Step 16: Correlate the result of step 14 with the result of step 15, and then take the absolute value;

[0071] Step 17: Compare the energy of each group of results obtained in step 16 to find the sequence value with the maximum energy;

[0072] Step 18: Input the result of step 17 into the code index detector to obtain the decimal number of the sequence, and then pass it through a decimal to binary converter to obtain the recovered index bit;

[0073] Step 19: According to the result of step 17, find the correlation result corresponding to the sequence with the maximum energy, and perform multi-level DCSK demodulation on the correlation result;

[0074] Step 20: Convert the result of step 19 from symbol to bit to obtain the restored modulated bits;

[0075] Step 21: Combine the index bit obtained in step 18 and the modulation bit obtained in step 20 and then perform parallel-to-serial conversion to restore the original information signal.

[0076] Based on the same technical concept as the above modulation and demodulation method, the present invention also proposes a multi-carrier multi-level differential chaotic shift keying modulation and demodulation system based on improved code index modulation, which can use the above method to modulate and demodulate signals. Specifically, the transmitting end (modulator) is implemented based on improved code index modulation and multi-level DCSK modulation based on Walsh code, wherein the improved code index modulation selects two different Walsh codes according to the index bit, and the modulation bit is converted into a corresponding constellation symbol by a bit symbol converter, and the multi-level DCSK modulation based on the Walsh code then multiplies the selected two different Walsh codes with the real and imaginary parts of the constellation symbol to obtain the information signal of the transmitting end, and the reference signal of the transmitting end is obtained by multiplying the Walsh code reference sequence using a chaotic generator. The receiving end (demodulator) uses an energy comparator, a multi-level threshold decision device, etc. to realize demodulation.

[0077] Figure 2 The specific structure of the transmitting end (modulator) in the system is shown. Generally speaking, it mainly includes: a serial-to-parallel conversion circuit, a chaotic signal generator, N binary-to-decimal converters, N Walsh sequence selectors, 2N+1 Walsh sequence multipliers, N bit-to-symbol converters, N multi-base DCSK modulators, N+1 pulse shaping filters, and N+1 carrier multipliers; the serial-to-parallel conversion circuit converts the serial data bits to be transmitted in the current symbol time into parallel data bits; the chaotic signal generator generates a discrete chaotic signal sequence; the N binary-to-decimal converters convert the binary of the index bit into a is a decimal number; the N Walsh sequence selectors select 2 Walsh sequences according to the result of the binary-to-decimal converter; the 2N+1 Walsh sequence multipliers perform Kronecker product multiplication on the selected Walsh sequence and the discrete chaotic signal; the N bit-to-symbol converters convert the modulated bits into constellation symbols; the N multi-level DCSK modulators implement multi-level DCSK modulation; the N+1 pulse shaping filters respectively perform pulse shaping filtering on the reference signal and the N groups of information signals; the N+1 carrier multipliers multiply the results of the N+1 pulse shaping filters by the N+1 carriers.

[0078] Figure 3The specific structure of the receiving end (demodulator) in the system is shown. Generally speaking, it mainly includes: N+1 carrier multipliers, N+1 matched filters, N+1 sampling switches, 1 Walsh reference sequence multiplier, NQ Walsh information sequence multipliers, NQ correlators, N energy comparators, N code index detectors, N decimal to binary converters, N selectors, N multi-base DCSK demodulators, N symbol bit conversion circuits and parallel-to-serial conversion circuits; the N+1 carrier The wave multiplier uses N+1 synchronized subcarriers to multiply the received signal respectively to obtain N+1 product signals; the N+1 matched filters perform matched filtering on the N+1 product signals respectively; the N+1 sampling switches perform time domain sampling on the N+1 product signals after matched filtering respectively to recover 1 discrete reference signal sequence and N discrete information signal sequences; the 1 Walsh reference sequence multiplier multiplies the result of the reference signal after the sampling switch with the expanded Walsh reference sequence, and then The recovered reference signal is obtained by averaging in sections; the NQ Walsh information sequence multipliers are to multiply N groups of information signals with Q extended Walsh sequences respectively, and then average in sections; the NQ correlators correlate the recovered reference signal with the Q averaged information signals in each group of information signals; the N energy comparators compare the energies of the N signals respectively to find the sequence value where the maximum energy is located; the N code index detectors save the sequence value where the maximum energy is located; the N decimal to binary converters convert the sequence value where the maximum energy is located into a binary number, so that the index bit can be demodulated; the N selectors select the correlation value of the corresponding sequence according to the result of the code index detector; the N multi-base DCSK demodulators perform multi-base DCSK demodulation on the N correlation values; the N symbol bit conversion circuits convert the results of the N multi-base DCSK demodulators into modulation bits; the parallel-to-serial conversion circuit combines the obtained N index bits and modulation bits respectively, and then merges them into 1 serial demodulation data bit and outputs it.

[0079] In the above-mentioned multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method based on improved code index modulation, information is transmitted through the MDCSK constellation and carrier label, which greatly improves the data transmission rate and energy efficiency of the system. In addition, the system adopts improved code index modulation at the transmitting end and improved code index demodulation at the receiving end, which greatly improves the data rate and reduces energy consumption. At the same time, the above-mentioned method can avoid the use of delay units in the receiving end and the transmitting end, effectively reduce the noise component in the decision variable of the receiving end, and improve the bit error performance of the system, so as to obtain a lower bit error rate.

[0080] In order to verify whether the above multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method based on improved code index modulation can substantially reduce the bit error rate, a verification test is performed through the following test case. The verification test process is designed as follows:

[0081] At the transmitting end, the signal is modulated by multi-carrier multi-ary differential chaotic shift keying based on improved code index modulation:

[0082] Step 1: Select the bit signal-to-noise ratio E in the channel b When / N0=10dB, the method according to the present invention is implemented under the conditions that the length θ of the discrete chaotic signal sequence within one symbol time is 100, the number of available carriers N+1=11, and P=16.

[0083] Step 2: Within one symbol period [0, Tb], the chaotic signal generator outputs a discrete chaotic signal sequence {c1, c2, ..., c 100}.

[0084] Step 3: Combine the discrete chaotic signal sequence generated in step 2 with the Walsh code W R Perform Kronecker product multiplication, where the Walsh code is generated by a 64*64 Hadamard matrix;

[0085] Step 4: Use the serial-to-parallel conversion circuit to convert the 40 serial data bits to be transmitted in the current symbol period into 10 parallel low-speed data bits. Each group of information includes two parts: 2 index bits and 2 modulation bits;

[0086] Step 5: Pass the 10 groups of index bits through the binary to decimal converter to obtain Q1, Q2, ..., Q 10 ;

[0087] Step 6: Convert the decimal number Q n Enter into the Walsh code selector and select 2 different Walsh codes, one of which uses W xn Indicates that the other one is W yn Indicates; where xn = 2D n +1,yn=2D n +2;

[0088] Step 7: Pass the 10 groups of modulated bits through the bit-to-symbol converter to obtain the constellation symbol S corresponding to each group n =a n +jb n ;

[0089] Step 8: Combine each group of two different Walsh codes obtained in step 6 with the chaotic signal c = [c1, c2, ... cθ ] are multiplied, here it is the Kronecker product;

[0090] Step 9: Multiply the result of step 6 by the result of step 7, that is

[0091] Step 10: Pass the results of step 3 and step 9 through the pulse shaping filter to obtain c R (t) and m n (t); of which:

[0092] Step 11: Place c R (t) is multiplied by the reference carrier f0 to obtain the reference signal at the transmitter: c R (t)cos(2πf0t);

[0093] Step 12: Place m n (t) respectively with 10 carriers (f1, f2…f N ) to obtain the information signal sent by the transmitter:

[0094] At the receiving end, the signal is demodulated by multi-carrier multi-ary differential chaotic shift keying based on improved code index modulation:

[0095] Step 13: Receive the reference signal sent in step 11, multiply it with the synchronized reference carrier f0, obtain a product signal, pass it through a matched filter, and then perform time domain sampling;

[0096] Step 14: Receive the information signal sent in step 12 and synchronize it with the N synchronized carriers (f1, f2…f N ) are multiplied, then pass through a matched filter, and then perform time domain sampling to obtain N groups of sampling signals;

[0097] Step 15: Combine the result of step 13 with the expanded Walsh sequence W R Multiply and average them piecewise to get the restored reference signal r R ;

[0098] Step 16: Compare each signal group in the result of step 14 with the extended Walsh sequence W1, W2, ..., W Q Multiply them, and then average them in sections to get the signal

[0099]

[0100] Step 17: Correlate the result of step 15 with the result of step 16, and then take the absolute value;

[0101] Step 18: Compare the energy of each group of results obtained in step 17 to find the sequence value with the maximum energy;

[0102] Step 19: Input the result of step 18 into the code index detector to obtain the decimal number of the sequence, and then pass it through a decimal to binary converter to obtain the recovered index bit;

[0103] Step 20: According to the result of step 19, find the correlation result corresponding to the sequence with the maximum energy, and perform multi-base DCSK demodulation on the correlation result;

[0104] Step 21: Convert the result of step 20 from symbol to bit to obtain the restored modulated bits;

[0105] Step 22: Combine the index bit obtained in step 19 and the modulation bit obtained in step 21 and then perform parallel-to-serial conversion to restore the original information signal.

[0106] The multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method based on improved code index modulation designed in the test case is tested by computer simulation. In the test, the number of transmitted data bits is 40*500 (average of 500 runs), and the discrete chaotic signal sequence is mapped by Logistic The chaotic signal sampling frequency is 1MHz, the symbol duration T=16μs, the equivalent number of signal sampling points in each symbol time is 16, the square raised cosine roll-off filter roll-off coefficient α=0.25, and the center frequency interval of all subcarriers satisfies Δf=1.25MHz.

[0107] Figure 4 is the bit error rate of the test case simulated in the additive white Gaussian noise channel. As a comparison, the figure also shows the bit error rate of the existing HDR-CI-DCSK method simulated under the same conditions. It can be seen from the figure that compared with the existing HDR-CI-DCSK (high-rate carrier index differential chaotic shift keying) method, the above-mentioned multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method based on improved code index modulation significantly reduces the bit error rate and shows better bit error performance.

[0108] In summary, the present invention can greatly reduce the noise component in the decision variable, thereby significantly improving the bit error performance of the system. At the same time, the method described in the present invention can avoid using a delay unit in the receiving end and the transmitting end, effectively reducing the noise component in the decision variable of the receiving end, improving the bit error performance of the system, and obtaining a lower bit error rate.

[0109] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present technical solution is within the protection scope of the present invention.

[0110] In order to make it easier for ordinary technicians in the field to understand the improvements of the present invention over the prior art, some drawings and descriptions of the present invention have been simplified, and for the sake of clarity, some other elements are omitted in this application document. Ordinary technicians in the field should realize that these omitted elements may also constitute the content of the present invention.

Claims

1. A multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method based on improved code index modulation, characterized in that: On the sending side: The information to be transmitted is converted from serial to parallel into N groups of parallel information, and each group of information is divided into p1 index bits and p2 modulation bits; each group of index bits is converted into a decimal number Q through a binary to decimal converter n , and then this decimal number Q n Enter the Walsh code selector and select the 2D n +1 and 2d n +2 Walsh codes, using W xn and W yn Indicates that, reuse W xn and W yn Realize the multi-level differential chaotic keying modulation of the modulation bit; the chaotic signal is generated by the chaos generator and combined with the Walsh code W R Perform Krone product multiplication to obtain a reference signal, where R≠xn, R≠yn; the 1-way reference signal and the N-way information signal are both passed through a pulse shaping filter, and then multiplied with N+1 carriers respectively, and then sent to the channel; On the receiving end: After multi-carrier demodulation, the reference signal and N information signals are recovered respectively; each information signal is multiplied with Q Walsh codes, and the averaged reference signal sequence is correlated and demodulated with the averaged N information signal sequences respectively. Each information signal then passes through an energy comparator to find the sequence number with the largest energy, and the code index value is recovered based on this sequence number. The decimal to binary converter is then used to obtain the recovered index bit, and the corresponding correlation demodulation result is selected based on the code index value with the largest energy. This result is demodulated by multi-base DCSK to recover the modulated bits, and finally the original information is output through parallel-to-serial conversion.

2. The multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method based on improved code index modulation as claimed in claim 1, characterized in that: At the transmitting end, signal modulation includes the following steps: Step 1: Perform serial-to-parallel conversion on the input information signal and divide it into N groups of information, each group of information includes two parts: p1 index bits and p2 modulation bits; Step 2: Pass the N groups of index bits through the binary to decimal converter to obtain Q n ; Step 3: Convert the decimal number Q n Enter into the Walsh code selector and select 2 different Walsh codes, one of which uses W xn Indicates that the other one is W yn Indicates; where xn = 2D n +1,yn=2D n +2; Step 4: Pass the N groups of modulated bits through the bit-to-symbol converter to obtain the corresponding constellation symbol S n , where S n =a n +jb n ; Step 5: Generate a Logistic chaotic signal of length θ: c = [c1, c2, …c θ ]; Step 6: Compare the result of step 5 with the Walsh code W R Perform Kronecker product multiplication; Step 7: Combine each group of two different Walsh codes obtained in step 3 with the chaotic signal c = [c1, c2, ... c θ ] are multiplied, here it is the Kronecker product; Step 8: Multiply the result of step 7 by the result of step 4, that is Step 9: Pass the results of step 6 and step 8 through the pulse shaping filter to obtain c R (t) and m n (t), where Step 10: Place c R (t) is multiplied by the reference carrier f0 to obtain the reference signal at the transmitter: c R (t)cos(2πf0t), send it to the channel; Step 11: Place m n (t) respectively with N carriers (f1, f2…f N ) to obtain the information signal sent by the transmitter: Send it to the channel.

3. The multi-carrier multi-ary differential chaotic shift keying modulation and demodulation method based on improved code index modulation as claimed in claim 1 or 2, characterized in that: At the receiving end, signal demodulation includes the following steps: Step 12: Multiply the received reference signal with the synchronized reference carrier f0 to obtain a product signal, which is then passed through a matched filter and then sampled in the time domain; Step 13: The received information signal is respectively synchronized with the N carriers (f1, f2…f N ) are multiplied, then pass through a matched filter, and then perform time domain sampling to obtain N groups of sampling signals; Step 14: Combine the result of step 12 with the expanded Walsh sequence W R Multiply and average them piecewise to get the restored reference signal r R ; Step 15: Compare each signal group in the result of step 13 with the extended Walsh sequence W 1， W2,…,W Q Multiply them, and then average them in sections to get the signal Step 16: Correlate the result of step 14 with the result of step 15, and then take the absolute value; Step 17: Compare the energy of each group of results obtained in step 16 to find the sequence value with the maximum energy; Step 18: Input the result of step 17 into the code index detector to obtain the decimal number of the sequence, and then pass it through a decimal to binary converter to obtain the recovered index bit; Step 19: According to the result of step 17, find the correlation result corresponding to the sequence with the maximum energy, and perform multi-level DCSK demodulation on the correlation result; Step 20: Convert the result of step 19 from symbol to bit to obtain the restored modulated bits; Step 21: Combine the index bit obtained in step 18 and the modulation bit obtained in step 20 and then perform parallel-to-serial conversion to restore the original information signal.

4. A multi-carrier multi-ary differential chaotic shift keying modulation and demodulation system based on improved code index modulation, comprising a transmitting end and a receiving end, characterized in that: The transmitting end and the receiving end adopt the method described in claim 1 to modulate and demodulate the signal.

5. The multi-carrier multi-ary differential chaotic shift keying modulation and demodulation system based on improved code index modulation as claimed in claim 4, characterized in that: The transmitting end modulates the input information signal according to the method of steps 1 to 11 in claim 2.

6. The multi-carrier multi-ary differential chaotic shift keying modulation and demodulation system based on improved code index modulation as claimed in claim 4 or 5, characterized in that: The receiving end demodulates the received signal according to the method of steps 12 to 21 in claim 3.

7. The multi-carrier multi-ary differential chaotic shift keying modulation and demodulation system based on improved code index modulation as claimed in claim 4 or 5, characterized in that: The transmitting end includes a serial-to-parallel conversion circuit, a chaotic signal generator, N binary-to-decimal converters, N Walsh sequence selectors, 2N+1 Walsh sequence multipliers, N bit-to-symbol converters, N multi-base DCSK modulators, N+1 pulse shaping filters, and N+1 carrier multipliers; The serial-to-parallel conversion circuit is used to convert the serial data bits to be transmitted within the current symbol time into parallel data bits; the chaotic signal generator is used to generate a discrete chaotic signal sequence; the N binary-to-decimal converters are used to convert the binary of the index bit into a decimal number; the N Walsh sequence selectors are used to select 2 Walsh sequences according to the results of the binary-to-decimal converters; the 2N+1 Walsh sequence multipliers are used to perform Kronecker product multiplication on the selected Walsh sequence and the discrete chaotic signal; the N bit-to-symbol converters are used to convert the modulated bits into constellation symbols; the N multi-level DCSK modulators are used to implement multi-level DCSK modulation; the N+1 pulse shaping filters are used to perform pulse shaping filtering on the reference signal and the N groups of information signals respectively; and the N+1 carrier multipliers are used to multiply the results of the N+1 pulse shaping filters by the N+1 carriers.

8. The multi-carrier multi-ary differential chaotic shift keying modulation and demodulation system based on improved code index modulation as claimed in claim 6, characterized in that: The receiving end includes N+1 carrier multipliers, N+1 matching filters, N+1 sampling switches, 1 Walsh reference sequence multiplier, NQ Walsh information sequence multipliers, NQ correlators, N energy comparators, N code index detectors, N decimal to binary converters, N selectors, N multi-base DCSK demodulators, N symbol bit conversion circuits and parallel-to-serial conversion circuits; The N+1 carrier multipliers are used to use N+1 synchronized subcarriers to multiply the received signals respectively to obtain N+1 product signals; the N+1 matched filters are used to perform matched filtering on the N+1 product signals respectively; the N+1 sampling switches are used to perform time domain sampling on the N+1 product signals after matched filtering to recover 1 discrete reference signal sequence and N discrete information signal sequences; the 1 Walsh reference sequence multiplier is used to multiply the result of the reference signal after the sampling switch with the extended Walsh reference sequence, and then average the results in segments to obtain the recovered reference signal; the NQ Walsh information sequence The column multiplier is used to multiply N groups of information signals with Q extended Walsh sequences respectively, and then average them in sections; the NQ correlators are used to correlate the recovered reference signal with the Q averaged information signals in each group of information signals; the N energy comparators are used to compare the energy of the N signals respectively to find the sequence value where the maximum energy is located; the N code index detectors are used to save the sequence value where the maximum energy is located; the N decimal to binary converters are used to convert the sequence value where the maximum energy is located into a binary number, so as to demodulate the index bit; the N selectors are used to select the correlation value of the corresponding sequence according to the result of the code index detector; The N multi-level DCSK demodulators are used to perform multi-level DCSK demodulation on the N correlation values; the N symbol bit conversion circuits are used to convert the results of the N multi-level DCSK demodulators into modulation bits; the parallel-to-serial conversion circuit is used to combine the obtained N index bits and modulation bits respectively and then merge them into one serial demodulation data bit and output it.

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