Multicarrier hybrid index modulation differential chaos shift keying modulator, demodulator, method and system

Abstract

The invention discloses a multicarrier hybrid index modulation differential chaos shift keying modulator, a demodulator, a method and a system, and relates to the technical field of communication. During modulation, to-be-transmitted information is converted into M groups of information through serial-to-parallel conversion, and each group of information comprises index bits, modulation bits and code index bits; generating a chaotic signal and performing Hilbert transform on the chaotic signal; hybrid index modulation is realized through an index selector and differential chaos shift keying; and selecting a Walsh code according to the code index bit, multiplying the Walsh code by the hybrid index modulation result, and then sending through multiple carriers. During demodulation, performing multi-carrier demodulation on the received signal to obtain a reference signal and M paths of information signals; the information signal is multiplied by a Walsh code and then segmented averaging is carried out, and code index bits are recovered after energy comparison; and determining an energy maximum value based on the recovered code index bit, performing related demodulation by using the chaotic signal and the Hilbert transform signal thereof, and recovering the index bit and the modulation bit. The method is low in bit error rate, better in performance and high in data rate.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and particularly to a multi-carrier hybrid index modulation differential chaos shift keying modulator, demodulator, method and system. Background Art

[0002] Chaotic digital modulation technology can not only retain the characteristics of traditional spread spectrum communication systems such as low probability of intercept and mitigation of multipath effects, but also exhibit unique advantages in many other aspects, including: reducing the hardware cost of the system; enhancing 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 concerned and studied in the fields of nonlinear science and information science.

[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 bit error performance, and shows strong competitiveness in many practical application scenarios (that is, including wireless personal area networks, wireless sensor networks, etc.). However, to ensure orthogonality between the reference signal and the information signal, DCSK transmits these two signals in different time periods, so delay units must be used at both the transmitting end and the receiving end. When transmitting in ultra-wideband, it is almost impossible to integrate analog delay units using existing processes, and the delay units implemented digitally 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 sub-carriers to simultaneously transmit the reference signal and multiple information signals, and distinguishes the reference signal and each information signal through different sub-carriers. Among all the sub-carriers, only 1 sub-carrier is assigned to the reference signal, and the remaining all sub-carriers are assigned to information signals, and each information signal occupies 1 sub-carrier. Although MC-DCSK eliminates the delay unit in the transceiver device, compared with traditional binary phase shift keying (BPSK), the bit error rate of MC-DCSK is still relatively high, and the bit error performance is not ideal. Summary of the Invention

[0005] The present invention aims to provide a multi - carrier hybrid index modulation differential chaos shift keying modulator, demodulator, method and system to solve the problems of high bit error rate, poor bit error performance and low data rate in the existing MC - DCSK modulation and demodulation methods.

[0006] In a first aspect, the present invention provides a multi - carrier hybrid index modulation differential chaos shift keying modulation method, and the modulation method includes the following steps:

[0007] The information to be transmitted is converted from serial to parallel into M groups of information, and each group of information includes index bits, modulation bits and code index bits;

[0008] Generate a chaotic signal and perform Hilbert transform on the chaotic signal;

[0009] Implement hybrid index modulation through an index selector and differential chaos shift keying;

[0010] Select a Walsh code according to the code index bits, multiply it with the result of hybrid index modulation, and then send it through multiple carriers.

[0011] Specifically, the multi - carrier hybrid index modulation differential chaos shift keying modulation method includes the following steps:

[0012] Step 1 - 1: Convert the information signal to be transmitted from serial to parallel, and divide it into M groups of information. Each group of information includes three parts: index bits, modulation bits and code index bits, and each part is N bits;

[0013] Step 1 - 2: Generate a Logistic chaotic signal with a length of θ and repeat it N times;

[0014] Step 1 - 3: Perform Hilbert transform on the chaotic signal generated in Step 1 - 2;

[0015] Step 1 - 4: According to the rules of hybrid index, input the index bit information of each group, and the results of Step 1 - 2 and Step 1 - 3 into an index selector to obtain the hybrid index result;

[0016] Step 1 - 5: Each group of modulation bits in the M groups of modulation bits respectively pass through N polarity converters and then multiply with the hybrid index result obtained in Step 1 - 4 to implement DCSK modulation for M groups;

[0017] Step 1 - 6: Each group of code index bits in the M groups of code index bits respectively pass through M binary - to - decimal converters to obtain code index symbols, and then pass through M Walsh code selectors to select the corresponding Walsh codes;

[0018] Step 1 - 7: Multiply the result of Step 1 - 5 with the result of Step 1 - 6, then pass through a pulse shaping filter and multiply with M carriers to obtain the transmitted information signal;

[0019] Steps 1-8: Multiply the result of Steps 1-2 by the reference Walsh code, then pass it through a pulse shaping filter, and then multiply it by the reference carrier to obtain the transmitted reference signal.

[0020] In a second aspect, the present invention provides a multi-carrier hybrid index modulation differential chaos shift keying demodulation method, and the demodulation method includes the following steps:

[0021] Perform multi-carrier demodulation on the received signal to obtain a reference signal and M-channel information signals;

[0022] Multiply the information signals by the Walsh code and then segment and average them, and restore the code index bits after energy comparison;

[0023] Determine the maximum energy value based on the restored code index bits, and perform correlation demodulation using the chaotic signal and its Hilbert transform signal to restore the index bits and modulation bits;

[0024] Output the original information after serial-to-parallel conversion.

[0025] Specifically, the multi-carrier hybrid index modulation differential chaos shift keying demodulation method includes the following steps:

[0026] Step 2-1: Multiply the received reference signal by the synchronized reference carrier to obtain one product signal, then pass it through a matched filter, and then perform time-domain sampling;

[0027] Step 2-2: Multiply the received information signals by the synchronized M carriers respectively, then pass them through matched filters, and then perform time-domain sampling to obtain M groups of time-domain sampling signals;

[0028] Step 2-3: Multiply the result of Step 2-1 by the reference Walsh code and then segment and average it;

[0029] Step 2-4: Perform Hilbert transform on the result of Step 2-3;

[0030] Step 2-5: Multiply each group of signals in the result of Step 2-2 by the Q-channel Walsh code and then segment and average them;

[0031] Step 2-6: Pass the result of Step 2-5 through an energy comparator, find the maximum energy value in each group, and perform code index detection on it to restore the code index bits;

[0032] Step 2-7: Correlate the maximum energy value found in each group in Step 2-6 with the result of Step 2-3;

[0033] Step 2-8: Correlate the maximum energy value found in each group in Step 2-6 with the result of Step 2-4;

[0034] Step 2-9: Subtract the result of Step 2-7 from the result of Step 2-8, then perform threshold decision to recover the index bits;

[0035] Step 2-10: Subtract the result of Step 2-7 from the result of Step 2-8, then perform threshold decision, and then through DCSK demodulation to recover the modulation bits;

[0036] Step 2-11: Combine the code index bits obtained in Step 2-6, the index bits obtained in Step 2-9, and the modulation bits obtained in Step 2-10, and then perform parallel-to-serial conversion to recover the original information signal.

[0037] In a third aspect, the present invention provides a multi-carrier hybrid index modulation differential chaos shift keying modulator, and this modulator performs signal modulation according to the multi-carrier hybrid index modulation differential chaos shift keying modulation method described above.

[0038] Further, the multi-carrier hybrid index modulation differential chaos shift keying modulator includes:

[0039] A serial-to-parallel conversion circuit, a chaotic signal generator, a Hilbert transform filter, a repetition circuit, M hybrid index selectors, M*N polarity converters, M binary-to-decimal converters, M Walsh code selectors, M DCSK modulators, M+1 Walsh code multipliers, M+1 pulse shaping filters, M+1 carrier multipliers;

[0040] The serial-to-parallel conversion circuit is used to convert the serial information bits to be transmitted within the current symbol time into parallel information bits; the chaotic signal generator is used to generate a discrete chaotic signal sequence; the Hilbert filter is used to implement the Hilbert transform of the chaotic signal; the repetition circuit is used to repeat the chaotic signal; the M hybrid index selectors are used to implement the hybrid index of the index bits; the M*N polarity converters are used to perform polarity conversion on the N-bit modulation bits in each group; the M binary-to-decimal converters are used to implement the conversion of M groups of code index bits to obtain code index symbols; the M Walsh code selectors are used to select a Walsh code according to the code index symbols; the M DCSK modulators are used to multiply the hybrid index result by the polarity conversion result; the M+1 Walsh code multipliers are used to multiply the result of the DCSK modulator by the Walsh code; the M+1 pulse shaping filters are used to perform pulse shaping filtering on the reference signal and M groups of information signals respectively; the M+1 carrier multipliers are used to multiply the results of the M+1 pulse shaping filters by the M+1 carriers.

[0041] Fourthly, the present invention provides a multi-carrier hybrid index modulation differential chaos shift keying demodulator, which demodulates signals according to the multi-carrier hybrid index modulation differential chaos shift keying demodulation method described above.

[0042] Further, the multi-carrier hybrid index modulation differential chaos shift keying demodulator includes:

[0043] M + 1 carrier multipliers, M + 1 matched filters, M + 1 sampling switches, 1 Walsh reference sequence multiplier, 1 reference sequence segmented averaging circuit, MQ Walsh information sequence multipliers, MQ information sequence segmented averaging circuits, 1 Hilbert transform filter, M energy comparators, M decimal-to-binary converters, 2M correlators, M subtraction circuits, M threshold decision circuits, M DCSK demodulators, and a parallel-to-serial conversion circuit;

[0044] The M+1 carrier multipliers are used to multiply the received signal by M+1 synchronized subcarriers respectively to obtain M+1 product signals; the M+1 matched filters are used to perform matched filtering on the M+1 product signals respectively; the M+1 sampling switches are used to perform time-domain sampling on the M+1 product signals after matched filtering to recover 1 discrete reference signal sequence and M discrete information signal sequences; the 1 Walsh reference sequence multiplier is used to multiply the sampled reference signal by the extended reference Walsh sequence; the 1 reference sequence segmented averaging circuit is used to perform segmented averaging on the result of the Walsh reference sequence multiplier; the MQ Walsh information sequence multipliers are used to multiply the M groups of sampled information signals by Q extended Walsh sequences respectively; the MQ information sequence segmented averaging circuits are used to perform segmented averaging on the results of the MQ Walsh information sequence multipliers; the 1 Hilbert transform filter is used to implement the Hilbert transform of the reference signal after segmented averaging; the M energy comparators are used to compare the energies of the Q signals in each of the M groups to find the sequence value where the maximum energy is located; the M decimal-to-binary converters are used to convert the sequence values where the maximum energy in each of the M groups is located into binary, which are the M groups of recovered code index bits; the 2M correlators are used to perform correlation on the maximum energy value in each of the M groups with the reference signal after segmented averaging and the Hilbert transform of the reference signal after segmented averaging respectively; the M subtraction circuits are used to subtract the 2 different correlation values in each of the M groups; the M threshold decision circuits are used to perform threshold decision on the results of the M subtraction circuits to recover M groups of index bits; the M DCSK demodulators are used to perform DCSK demodulation on the results of the M threshold decisions to recover M groups of modulation bits; the serial-to-parallel conversion circuit is used to combine the obtained M groups of code index bits, M groups of index bits and M groups of modulation bits respectively and then merge them into 1 serial data bit for output.

[0045] In a fifth aspect, the present invention provides a multi-carrier hybrid index modulation differential chaos shift keying modulation and demodulation method, and the method includes:

[0046] The steps in the multi-carrier hybrid index modulation differential chaos shift keying modulation method described above;

[0047] The steps in the multi-carrier hybrid index modulation differential chaos shift keying demodulation method described above.

[0048] In a sixth aspect, the present invention provides a multi-carrier hybrid index modulation differential chaos shift keying modulation and demodulation system, and the system includes:

[0049] The multi-carrier hybrid index modulation differential chaos shift keying modulator described above;

[0050] The multi - carrier hybrid index modulation differential chaos shift keying demodulator described above.

[0051] The present invention transmits information through a combination of hybrid index, differential chaos shift keying (DCSK) modulation, and code index, significantly improving the data transmission rate and energy efficiency of the system. At the same time, the present invention adopts multi - carrier technology, greatly improving the spectral efficiency of the system. In addition, the method adopted by the present invention does not require the use of a delay unit, can effectively reduce the noise component in the decision variable, thereby significantly improving the bit error performance of the system, and further achieving a lower bit error rate. Brief Description of the Drawings

[0052] Figure 1 It is a schematic flow chart of the modulation and demodulation method involved in the embodiment;

[0053] Figure 2 It is a schematic structural diagram of the modulator (transmitter) in the embodiment;

[0054] Figure 3 It is a schematic structural diagram of the demodulator (receiver) in the embodiment;

[0055] Figure 4 It is a comparison diagram of the bit error performance between the modulation and demodulation method involved in the embodiment and the existing MC - DCSK method in an additive white Gaussian noise channel. Detailed Embodiment

[0056] For the convenience of those skilled in the art, the present invention will be further described below in conjunction with the embodiments and the drawings.

[0057] Generally speaking, the present invention mainly modulates and demodulates signals in the following manner:

[0058] At the transmitter (modulator), multi - carrier hybrid index modulation differential chaos shift keying modulation is performed on the signal:

[0059] First, the information to be transmitted is converted from serial to parallel into M groups of information. Each group of information includes N bits of index bits, modulation bits, and code index bits. A chaotic signal generator is used to generate a chaotic signal, and it is subjected to Hilbert transform. The hybrid index modulation is realized by using an index selector and differential chaos shift keying modulation. The code index modulation symbol selects one path of Walsh code through a Walsh code selector and then multiplies it with the result of the hybrid index modulation, and then is sent to the channel through multi - carriers;

[0060] At the receiver (demodulator), multi - carrier hybrid index modulation differential chaos shift keying demodulation is performed on the signal:

[0061] First, perform multi - carrier demodulation to obtain 1 reference signal and M information signals. Among them, the M information signals are each multiplied by the Q - channel Walsh code and then segmented and averaged. After comparing the energies of the obtained results, the code index bits can be recovered. Then, according to the recovered code index bits, the maximum energy value is found, and the chaotic signal and its Hilbert transform signal are used to perform correlation demodulation on the maximum energy value to recover the index bits and modulation bits. Finally, after parallel - to - serial conversion, the original information is output.

[0062] Figure 1 The process of the multi - carrier hybrid index modulation differential chaos shift keying modulation and demodulation method is shown, mainly including the following steps:

[0063] At the transmitter (modulator), perform multi - carrier hybrid index modulation differential chaos shift keying modulation on the signal:

[0064] Step 1: Perform serial - to - parallel conversion on the information signal to be transmitted, divide it into M groups of information, and each group of information includes three parts: index bits, modulation bits, and code index bits, and each part is N bits;

[0065] Step 2: Generate a Logistic chaotic signal with a length of θ, c = [c 1 , c 2 , … c θ , and repeat it N times;

[0066] Step 2: Perform Hilbert transform on the chaotic signal generated in Step 2;

[0067] Step 4: According to the rules of hybrid index, input the index bit information of each group, the results of Step 2 and Step 3 into the index selector to obtain the hybrid index result;

[0068] Step 5: Each group of modulation bits in the M groups of modulation bits respectively pass through N polarity converters and then multiply with the hybrid index result obtained in Step 4 to achieve DCSK modulation for M groups;

[0069] Step 6: Each group of code index bits in the M groups of code index bits respectively pass through M binary - to - decimal converters to obtain code index symbols, and then pass through M Walsh code selectors to select the corresponding Walsh codes;

[0070] Step 7: Multiply the result of Step 5 with the result of Step 6, and then multiply with M carriers after passing through a pulse - shaping filter to obtain the information signal transmitted by the transmitter;

[0071] Step 8: Multiply the result of Step 2 with the reference Walsh code, then pass through a pulse - shaping filter, and then multiply with the reference carrier to obtain the reference signal transmitted by the transmitter.

[0072] At the receiving end (demodulator), multi-carrier hybrid index modulation differential chaos shift keying modulation is performed on the signal:

[0073] Step 9: Receive the reference signal sent in Step 8, multiply it with the synchronized reference carrier f 0 to obtain one product signal, then pass it through a matched filter, and then perform time-domain sampling;

[0074] Step 10: Receive the information signal sent in Step 7, multiply it with each of the M synchronized carriers respectively, then pass it through a matched filter, and then perform time-domain sampling to obtain M groups of time-domain sampling signals;

[0075] Step 11: Multiply the result of Step 9 with the reference Walsh code and then perform segmented averaging;

[0076] Step 12: Perform Hilbert transform on the result of Step 11;

[0077] Step 13: Multiply each group of signals in the result of Step 10 with the Q-channel Walsh code and then perform segmented averaging;

[0078] Step 14: Pass the result of Step 13 through an energy comparator, find the maximum energy value in each group, and perform code index detection on it to recover the code index bits;

[0079] Step 15: Correlate the maximum energy value in each group found in Step 14 with the result of Step 11;

[0080] Step 16: Correlate the maximum energy value in each group found in Step 14 with the result of Step 12;

[0081] Step 17: Subtract the result of Step 15 from the result of Step 16, and then perform threshold decision to recover the index bits;

[0082] Step 18: Subtract the result of Step 15 from the result of Step 16, then perform threshold decision, and then perform DCSK demodulation to recover the modulation bits;

[0083] Step 19: Combine the code index bits obtained in Step 14, the index bits obtained in Step 17, and the modulation bits obtained in Step 18, and then perform parallel-to-serial conversion to recover the original information signal.

[0084] Based on the same technical concept as the above modulation and demodulation method, the present invention also proposes a multi-carrier hybrid index modulation differential chaos shift keying modulation and demodulation system, which can modulate and demodulate signals using the above method. Specifically, the modulator (transmitter) is implemented based on hybrid index, DCSK modulation, and code index. Among them, the hybrid index is realized using a chaotic signal and its Hilbert transform. The code index modulation selects one Walsh code according to the code index bits and multiplies it with the result of DCSK modulation. The modulation bits are DCSK modulated with the result of the hybrid index after polarity conversion. The reference signal of the modulator is obtained by multiplying a chaotic generator with a Walsh code reference sequence. The demodulator (receiver) realizes demodulation using an energy comparator, a threshold decision maker, DCSK demodulation, etc.

[0085] Figure 2 Fig. 4 shows the specific structure of the modulator (transmitter) in this system. Generally speaking, it mainly includes: a serial-to-parallel conversion circuit, a chaotic signal generator, a Hilbert transform filter, a repetition circuit, M hybrid index selectors, M*N polarity converters, M binary-to-decimal converters, M Walsh code selectors, M DCSK modulators, M+1 Walsh code multipliers, M+1 pulse shaping filters, and M+1 carrier multipliers. Among them, the serial-to-parallel conversion circuit is used to convert the serial information bits to be transmitted within the current symbol time into parallel information bits; the chaotic signal generator is used to generate a discrete chaotic signal sequence; the Hilbert filter is used to implement the Hilbert transform of the chaotic signal; the repetition circuit is used to repeat the chaotic signal; M hybrid index selectors are used to implement the hybrid index of the index bits; M*N polarity converters are used to perform polarity conversion on the N-bit modulation bits of each group; M binary-to-decimal converters are used to implement the conversion of M groups of code index bits to obtain code index symbols; M Walsh code selectors are used to select a Walsh code according to the code index symbols; M DCSK modulators are used to multiply the result of the hybrid index with the result of polarity conversion; M+1 Walsh code multipliers are used to multiply the result of the DCSK modulator with the Walsh code; M+1 pulse shaping filters are used to perform pulse shaping filtering on the reference signal and M groups of information signals respectively; M+1 carrier multipliers are used to multiply the results of M+1 pulse shaping filters with M+1 carriers.

[0086] Figure 3The specific structure of the demodulator (receiver end) in this system is shown. Generally speaking, it mainly includes: M+1 carrier multipliers, M+1 matched filters, M+1 sampling switches, 1 Walsh reference sequence multiplier, 1 reference sequence segmented averaging circuit, MQ Walsh information sequence multipliers, MQ information sequence segmented averaging circuits, 1 Hilbert transform filter, M energy comparators, M decimal-to-binary converters, 2M correlators, M subtraction circuits, M threshold decision circuits, M DCSK demodulators, and a serial-to-parallel conversion circuit. Among them, the M+1 carrier multipliers are used to multiply the received signal by M+1 synchronized subcarriers respectively to obtain M+1 product signals; the M+1 matched filters are used to perform matched filtering on the M+1 product signals respectively; the M+1 sampling switches are used to perform time-domain sampling on the M+1 product signals after matched filtering to recover 1 discrete reference signal sequence and M discrete information signal sequences; 1 Walsh reference sequence multiplier is used to multiply the sampled reference signal by the extended reference Walsh sequence; 1 reference sequence segmented averaging circuit is used to perform segmented averaging on the result of the Walsh reference sequence multiplier; the MQ Walsh information sequence multipliers are used to multiply the M groups of sampled information signals by Q extended Walsh sequences respectively; the MQ information sequence segmented averaging circuits are used to perform segmented averaging on the results of the MQ Walsh information sequence multipliers; 1 Hilbert transform filter is used to perform the Hilbert transform on the reference signal after segmented averaging; the M energy comparators are used to compare the energies of Q signals in each of the M groups to find the sequence value where the maximum energy is located; the M decimal-to-binary converters are used to convert the sequence values where the maximum energy in each of the M groups is located into binary, which are the M groups of recovered code index bits; the 2M correlators are used to correlate the maximum energy in each of the M groups with the reference signal after segmented averaging and the Hilbert transform of the reference signal after segmented averaging respectively; the M subtraction circuits are used to subtract the 2 different correlation values in the M groups; the M threshold decision circuits are used to perform threshold decision on the results of the M subtraction circuits to recover the M groups of index bits; the M DCSK demodulators are used to perform DCSK demodulation on the results of the M threshold decisions to recover the M groups of modulated bits; the serial-to-parallel conversion circuit is used to combine the obtained M groups of code index bits, M groups of index bits, and M groups of modulated bits respectively and then merge them into 1 serial data bit output.

[0087] In the above multi-carrier hybrid index modulation differential chaos shift keying modulation and demodulation method and system, information is transmitted through hybrid indexing, DCSK modulation, and code indexing, which greatly increases the data transmission rate and energy efficiency of the system. In addition, the multi-carrier technology is adopted at the transmitting end in the present invention, which greatly improves the spectral efficiency of the system. At the same time, the method adopted in the present invention can avoid using delay units at the receiving end and the transmitting end, effectively reducing the noise component in the decision variable at the receiving end, improving the bit error performance of the system, and obtaining a lower bit error rate.

[0088] In order to verify whether the above multi-carrier hybrid index modulation differential chaos shift keying modulation and demodulation method can substantially reduce the bit error rate, verification tests are carried out through the following test cases, and the process design of the verification test is as follows:

[0089] At the transmitting end (modulator), multi-carrier hybrid index modulation differential chaos shift keying modulation is performed on the signal:

[0090] Step 1: When the bit signal-to-noise ratio E b / N 0 = 10 dB in the channel, the method based on the present invention is implemented under the conditions that the length θ of the discrete chaotic signal sequence within one symbol time is 80, the number of available carriers M + 1 = 5, N = 4, and P = 128.

[0091] Step 2: Perform serial-to-parallel conversion on the information signal to be transmitted, divide it into 4 groups of information, and each group of information includes three parts: index bits, modulation bits, and code index bits, and each part is 4 bits;

[0092] Step 3: Generate a Logistic chaotic signal with a length of 80 within 1 symbol period [0, Tb] and repeat it 4 times;

[0093] Step 4: Perform Hilbert transform on the chaotic signal generated in Step 2;

[0094] Step 5: According to the rules of hybrid indexing, input the index bit information of each group, and the results of Steps 2 and 3 into the index selector to obtain the hybrid index result;

[0095] Step 6: Each group of modulation bits in the 4 groups of modulation bits are respectively multiplied by the hybrid index result obtained in Step 4 after passing through N polarity converters to implement 4 groups of DCSK modulation;

[0096] Step 7: The 4 groups of code index bits are respectively passed through 4 binary-to-decimal converters to obtain code index symbols, and then 4 Walsh code selectors are used to select the corresponding Walsh codes; where the Walsh codes are generated by a 128 * 128 Hadamard matrix;

[0097] Step 8: Multiply the result of Step 5 by the result of Step 6, then multiply by 4 carriers after passing through a pulse shaping filter to obtain the information signal transmitted by the transmitter;

[0098] Step 9: Multiply the result of Step 2 by a reference Walsh code, then pass through a pulse shaping filter and multiply by a reference carrier to obtain the reference signal transmitted by the transmitter;

[0099] At the receiver (demodulator), perform multi-carrier hybrid index modulation differential chaos shift keying demodulation on the signal:

[0100] Step 10: Receive the reference signal transmitted in Step 9, multiply it by the synchronized reference carrier f 0 to obtain a product signal, then pass through a matched filter and perform time-domain sampling;

[0101] Step 11: Receive the information signal transmitted in Step 8, multiply it by the 4 synchronized carriers respectively, then pass through a matched filter and perform time-domain sampling to obtain M groups of time-domain sampling signals;

[0102] Step 12: Multiply the result of Step 10 by a reference Walsh code and then perform segmented averaging;

[0103] Step 13: Perform Hilbert transform on the result of Step 12;

[0104] Step 14: Multiply each group of signals in the result of Step 11 by 16 Walsh codes respectively and then perform segmented averaging;

[0105] Step 15: Pass the result of Step 14 through an energy comparator, find the maximum energy value in each group, and perform code index detection on it to recover the code index bits;

[0106] Step 16: Correlate the maximum energy value found in each group in Step 15 with the result of Step 11;

[0107] Step 17: Correlate the maximum energy value found in each group in Step 15 with the result of Step 12;

[0108] Step 18: Subtract the result of Step 16 from the result of Step 17, then perform threshold decision to recover the index bits;

[0109] Step 19: Subtract the result of Step 16 from the result of Step 17, then perform threshold decision and perform DCSK demodulation to recover the modulation bits;

[0110] Step 20: Combine the code index bits obtained in Step 15, the index bits obtained in Step 18, and the modulation bits obtained in Step 19, then perform parallel-to-serial conversion to recover the original information signal.

[0111] The multi - carrier hybrid index modulation differential chaos shift keying modulation and demodulation method designed in the test case is tested using computer simulation. In the test, the number of transmitted data bits is 48 * 200 (average value taken over 200 runs), and the discrete chaotic signal sequence is generated by the Logistic map The chaotic signal sampling frequency is 1 MHz, the symbol duration T = 16 μs, the equivalent number of signal sampling points within each symbol time is 16, the roll - off factor α of the square root raised - cosine roll - off filter is 0.2, and the center frequency interval of all sub - carriers satisfies Δf = 1.25 MHz.

[0112] Figure 4 is the bit error rate of the test case obtained by simulation in an additive white Gaussian noise channel. For comparison, the bit error rate of the existing MC - DCSK method obtained by simulation under the same conditions is also given in the figure. It can be seen from the figure that compared with the existing MC - DCSK method, the above - mentioned multi - carrier hybrid index modulation differential chaos shift keying modulation and demodulation method significantly reduces the bit error rate and shows better bit error performance.

[0113] In summary, compared with the existing multi - carrier differential chaos shift keying (MC - DCSK) modulation and demodulation method, the multi - carrier hybrid index modulation differential chaos shift keying modulation and demodulation method and system provided by the present invention transmit information through hybrid index, DCSK modulation, and code index, greatly increasing the data transmission rate and energy efficiency of the system. In addition, the present invention adopts multi - carrier technology at the sending end, greatly improving the spectral efficiency of the system. At the same time, since the method adopted by the present invention can avoid using delay units at the receiving end and the sending end, effectively reducing the noise component in the decision variable at the receiving end and improving the bit error performance of the system, a lower bit error rate can be obtained compared with the MC - DCSK modulation and demodulation method.

[0114] The above - mentioned embodiments are preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious substitution without departing from the concept of the technical solution of the present invention is within the protection scope of the present invention.

[0115] In order to make it more convenient for those of ordinary skill in the art 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 have also been omitted in this application document. Those of ordinary skill in the art should be aware that these omitted elements can also constitute the content of the present invention.

Claims

1. A multi-carrier hybrid index modulation differential chaotic shift keying modulation method, characterized in that: The following steps are involved: The information to be transmitted is converted into M groups of information by serial-to-parallel conversion, each group of information includes an index bit, a modulation bit and a code index bit; generating a chaotic signal and performing Hilbert transform on the chaotic signal; Hybrid index modulation is achieved through index selector and differential chaotic shift keying; The Walsh code is selected according to the code index bit, multiplied by the mixed index modulation result and then sent via multi-carrier.

2. The multi-carrier hybrid index modulation differential chaotic shift keying modulation method as claimed in claim 1, characterized in that: The following steps are involved: Step 1-1: Perform serial-to-parallel conversion on the information signal to be transmitted and divide it into M groups of information, each group of information includes three parts: index bit, modulation bit and code index bit, and each part is N bits; Step 1-2: Generate a Logistic chaotic signal of length θ and repeat it N times; Step 1-3: The chaotic signal generated in step 1-2 is subjected to Hilbert transform; Step 1-4: According to the mixed index rule, the index bit information of each group and the results of steps 1-2 and 1-3 are input into the index selector to obtain the mixed index result; Step 1-5: The modulation bits of each group of the M groups of modulation bits are respectively passed through N polarity converters and then multiplied with the mixed index result obtained in step 1-4 to realize DCSK modulation of the M groups; Step 1-6: The M groups of code index bits are respectively passed through M binary to decimal converters to obtain code index symbols, and then passed through M Walsh code selectors to select the corresponding Walsh code; Step 1-7: multiply the result of step 1-5 by the result of step 1-6, and then multiply by M carriers after passing through a pulse shaping filter to obtain a transmitted information signal; Step 1-8: Multiply the result of step 1-2 by the reference Walsh code, pass through a pulse shaping filter, and then multiply by the reference carrier to obtain a transmitted reference signal.

3. A multi-carrier hybrid index modulation differential chaotic shift keying demodulation method, characterized in that: The following steps are involved: Perform multi-carrier demodulation on the received signal to obtain a reference signal and M-channel information signals; The information signal is multiplied by the Walsh code and then averaged piecewise, and the code index bit is recovered after energy comparison; The maximum energy value is determined based on the recovered code index bit, and the chaotic signal and its Hilbert transform signal are used for correlation demodulation to recover the index bit and the modulation bit; The original information is output after parallel-to-serial conversion.

4. The multi-carrier hybrid index modulation differential chaotic shift keying demodulation method as claimed in claim 3, characterized in that: The following steps are involved: Step 2-1: Multiply the received reference signal with the synchronized reference carrier to obtain a product signal, which is then passed through a matched filter and then sampled in the time domain; Step 2-2: Multiply the received information signal with the synchronized M carriers respectively, pass through a matched filter, and then perform time domain sampling to obtain M groups of time domain sampling signals; Step 2-3: multiply the result of step 2-1 by the reference Walsh code and then average the result in segments; Step 2-4: The result of step 2-3 is subjected to Hilbert transform; Step 2-5: multiply each group of signals in the result of step 2-2 by the Q-path Walsh code and then perform segment-wise averaging; Step 2-6: Pass the result of step 2-5 through the energy comparator to find the maximum energy in each group, and perform code index detection on it to recover the code index bit; Step 2-7: Correlate the maximum energy values ​​of each group found in step 2-6 with the results of step 2-3; Step 2-8: Correlate the maximum energy value of each group found in step 2-6 with the result of step 2-4; Step 2-9: Subtract the result of step 2-7 from the result of step 2-8, and then perform threshold determination to restore the index bit; Step 2-10: Subtract the result of step 2-7 from the result of step 2-8, perform threshold determination, and then perform DCSK demodulation to recover the modulated bits; Step 2-11: The code index bits obtained in step 2-6, the index bits obtained in step 2-9, and the modulation bits obtained in step 2-10 are combined and then parallel-to-serial converted to restore the original information signal.

5. Multi-carrier hybrid index modulation differential chaotic shift keying modulator, characterized in that: Signal modulation is performed according to the multi-carrier hybrid index modulation differential chaotic shift keying modulation method described in claim 1 or 2.

6. The multi-carrier hybrid index modulation differential chaotic shift keying modulator according to claim 5, characterized in that: include: Serial-to-parallel conversion circuit, chaotic signal generator, Hilbert transform filter, repetitive circuit, M mixed index selectors, M*N polarity converters, M binary to decimal converters, M Walsh code selectors, M DCSK modulators, M+1 Walsh code multipliers, M+1 pulse shaping filters, M+1 carrier multipliers; The serial-to-parallel conversion circuit is used to convert serial information bits to be transmitted within the current symbol time into parallel information bits; the chaotic signal generator is used to generate a discrete chaotic signal sequence; the Hilbert filter is used to implement the Hilbert transform of the chaotic signal; the repetition circuit is used to repeat the chaotic signal; the M mixed index selectors are used to implement mixed indexing of index bits; the M*N polarity converters are used to implement polarity conversion of each group of N-bit modulation bits; the M binary-to-decimal converters are used to implement conversion of M groups of code index bits to obtain code index symbols; the M Walsh code selectors are used to select a Walsh code according to the code index symbol; the M DCSK modulators are used to multiply the mixed index result with the polarity conversion result; the M+1 Walsh code multipliers are used to multiply the result of the DCSK modulator with the Walsh code; the M+1 pulse shaping filters are used to perform pulse shaping filtering on the reference signal and the M groups of information signals respectively; and the M+1 carrier multipliers are used to multiply the results of the M+1 pulse shaping filters with the M+1 carriers.

7. Multi-carrier hybrid index modulation differential chaotic shift keying demodulator, characterized in that: Signal demodulation is performed according to the multi-carrier hybrid index modulation differential chaotic shift keying demodulation method described in claim 3 or 4.

8. The multi-carrier hybrid index modulation differential chaotic shift keying demodulator according to claim 7, characterized in that: include: M+1 carrier multipliers, M+1 matching filters, M+1 sampling switches, 1 Walsh reference sequence multiplier, 1 reference sequence segmented averaging circuit, MQ Walsh information sequence multipliers, MQ information sequence segmented averaging circuits, 1 Hilbert transform filter, M energy comparators, M decimal to binary converters, 2M correlators, M subtraction circuits, M threshold decision circuits, M DCSK demodulators and parallel-to-serial conversion circuits; The M+1 carrier multipliers are used to multiply the received signals with M+1 synchronized subcarriers respectively to obtain M+1 product signals; the M+1 matched filters are used to perform matched filtering on the M+1 product signals respectively; the M+1 sampling switches are used to perform time domain sampling on the M+1 product signals after matched filtering to recover 1 discrete reference signal sequence and M discrete information signal sequences; the 1 Walsh reference sequence multiplier is used to multiply the sampled reference signal with the extended reference Walsh sequence; the 1 reference sequence segmented averaging circuit is used to segmentally average the result of the Walsh reference sequence multiplier; the MQ Walsh information sequence multipliers are used to multiply the sampled M groups of information signals with Q extended Walsh sequences respectively; the MQ information sequence segmented averaging circuits are used to segmentally average the results of the MQ Walsh information sequence multipliers; the 1 Hilbert transform filter is used to implement segmented The M energy comparators are used to compare the energy of each Q-channel signal in the M groups to find the sequence value where the maximum energy is located; the M decimal-to-binary converters are used to convert the sequence value where the maximum energy of each group found in the M groups is located into binary, that is, the recovered M group code index bits; the 2M correlators are used to correlate the maximum energy of each group in the M groups with the reference signal after segmented averaging and the Hilbert transform of the reference signal after segmented averaging respectively; the M subtraction circuits are used to subtract two different correlation values ​​in the M groups; the M threshold decision circuits are used to perform threshold decision on the results of the M groups of subtraction circuits to recover the M groups of index bits; the M DCSK demodulators are used to perform DCSK demodulation on the results of the M threshold decisions to recover the M groups of modulation bits; the parallel-to-serial conversion circuit is used to combine the obtained M groups of code index bits, M groups of index bits and M groups of modulation bits and then merge them into 1 serial data bit output.

9. A multi-carrier hybrid index modulation differential chaotic shift keying modulation and demodulation method, characterized in that: include: The steps in the multi-carrier hybrid index modulation differential chaotic shift keying modulation method according to claim 1 or 2; The steps in the multi-carrier hybrid index modulation differential chaotic shift keying demodulation method described in claim 3 or 4.

10. A multi-carrier hybrid index modulation differential chaotic shift keying modulation and demodulation system, characterized in that: include: The multi-carrier hybrid index modulation differential chaotic shift keying modulator according to claim 5 or 6; The multi-carrier hybrid index modulation differential chaotic shift keying demodulator as described in claim 7 or 8.

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