Chaotic orthogonal encoding-based encrypted dual-channel spread spectrum communication method and system

Abstract

The application discloses an encryption double-channel spread spectrum communication method based on chaotic orthogonal coding, which comprises the following steps: obtaining information streams of two channels at a transmitting end, encoding the information streams by chaotic base sequences of a chaotic orthogonal encoder group after spread spectrum mapping to obtain output sequences, obtaining an encoded signal after superposition, and transmitting the encoded signal after first preprocessing; obtaining a sampling sequence by second preprocessing of a received signal at a receiving end, and obtaining a down-sampling sequence by decoding and down-sampling processing; constructing a receiving reference sequence and a receiving information sequence, and decoding the information streams of the two channels by using the receiving reference sequence and the receiving information sequence in sequence; wherein, the design method of the chaotic base sequences is as follows: generating chaotic sequences by triggering chaotic mapping by using a preset key at the transmitting end, and obtaining multiple groups of chaotic orthogonal sequences which are mutually orthogonal by Schmidt orthogonalization of the chaotic sequences; and different chaotic orthogonal sequence combinations are used as chaotic base sequences of the chaotic orthogonal encoder group.

Description

Technical Field

[0001] This invention belongs to the field of chaotic spread spectrum communication, and relates to an encrypted dual-channel spread spectrum communication method and system based on chaotic orthogonal coding. Background Technology

[0002] Chaotic communication systems have attracted widespread attention from researchers over the past two decades, especially a series of chaotic spread spectrum communication schemes represented by Differential Chaotic Keying (DCSK) systems, which have gained widespread industry recognition for their high reliability in complex wireless channels. With the development of digitalization and informatization, chaotic communication systems have shown enormous application potential in fields such as the Internet of Things, satellite communication, and underwater communication. In recent years, with in-depth research, the performance of chaotic communication systems has been further improved. The introduction of new chaotic modulation and demodulation techniques and signal processing methods has led to significant improvements in transmission rate, bit error rate, and anti-interference capabilities.

[0003] Existing DCSK-based spread spectrum communication schemes generally use discrete / continuous signals such as Logistic maps or Lorenz systems as communication carriers. Chaotic signals cannot exhibit "ideal" orthogonality, thus introducing intra-symbol interference into the modulation signal. Furthermore, DCSK communication systems significantly reduce communication speeds because they need to transmit reference signals that do not carry information. Summary of the Invention

[0004] The purpose of this invention is to provide an encrypted dual-channel spread spectrum communication method and system based on chaotic orthogonal coding. The method has a chaotic carrier with good orthogonal characteristics, which can effectively improve the chaotic spread spectrum communication rate.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A method for encrypted dual-channel spread spectrum communication based on chaotic orthogonal coding, comprising:

[0007] At the transmitting end, information streams from two channels are acquired; the information streams from the two channels are spread spectrum mapped to obtain multiple spread spectrum sequences; the multiple spread spectrum sequences are sequentially encoded by the chaotic basis sequences of a chaotic orthogonal encoder group to obtain output sequences; the output sequences are superimposed to obtain coded signals; the coded signals are transmitted after the first preprocessing.

[0008] At the receiving end, the received signal is preprocessed to obtain a sampling sequence. The sampling sequence is then processed by a chaotic orthogonal decoder and downsampled to obtain a downsampled sequence. A receiving reference sequence and a receiving information sequence are constructed based on the downsampled sequence, and the information streams of the two channels are decoded sequentially using the receiving reference sequence and the receiving information sequence.

[0009] The design method for the chaotic basis sequence is as follows:

[0010] At the transmitting end, a chaotic sequence is generated by triggering a chaotic mapping using a preset key. The chaotic sequence is then orthogonalized by Schmitt to obtain multiple sets of mutually orthogonal chaotic orthogonal sequences. Different combinations of chaotic orthogonal sequences serve as the chaotic basis sequences of the chaotic orthogonal encoder group.

[0011] Furthermore, the given key is fed into the chaotic system as an initial value to generate a system of length N. p A chaotic sequence C; where N p Indicates the number of sampling points for the chaotic signal;

[0012] Divide the chaotic sequence C into N equal parts. T ×N c The segmented sequence is then subjected to Schmitt orthogonalization to obtain the chaotic orthogonal sequence x corresponding to each segment. i ;where N T N represents a reconstructed signal segment. c Indicates the number of orthogonal sequences;

[0013] All chaotic orthogonal sequences x i Reassemble into N in order. c Group, to obtain N c A chaotic basis sequence.

[0014] Furthermore, the information streams of the two channels are spread spectrum mapped to obtain a multi-path spread spectrum sequence, including:

[0015] The two channels are Channel 1 for sending information stream A and Channel 2 for sending information stream B;

[0016] Information flow A = [A1, A2, ..., A k ,…,A Nc ] Tr B = [b1, b2, ..., b k ,…,b Nc ] Tr ;where A k This represents the k-th information sequence in information flow A, where 1 ≤ k ≤ N. c b k Tr represents the k-th binary bit in information stream B, and is defined as the transpose symbol; N c This refers to the number of bits transmitted in channel two and the number of information sequences transmitted in channel one.

[0017] If information streams A and B are spread spectrum mapped, then the spread spectrum sequence of the k-th transmission can be represented as:

[0018] D k =[A k Ak ×b k ].

[0019] Furthermore, the multi-channel spread spectrum sequences are sequentially encoded using the chaotic basis sequences of a chaotic orthogonal encoder group to obtain the output sequence, which is represented as:

[0020]

[0021] Among them, u k (n) is the output sequence u of the k-th chaotic orthogonal encoder. k The nth value in, 1≤k≤N c , 1≤n≤N;N=n s ×N T +2×L-1;n s d is the oversampling rate of the chaotic signal, L is the system spreading gain; k,m For the k-th spreading sequence D k The m-th symbol in p k (n) represents the k-th chaotic basis sequence p k The nth value in N s For the k-th information sequence A k The number of bits transmitted.

[0022] Furthermore, the first preprocessing consists of SRRC and upcarrier operation; the second preprocessing consists of downloading, matched filtering, and sampling operation.

[0023] Furthermore, the chaotic orthogonal decoder decodes the sampled sequence to obtain the expression for the output sequence:

[0024] The output sequence ξ of the k-th chaotic orthogonal decoder k (1≤k≤N c The o-th (1≤o≤2N) in ) s ×n s ) values ​​ξ k (o) is as follows:

[0025]

[0026] Where r(n) is the nth value in the sampling sequence r, p k (n) is the k-th chaotic basis sequence p in the . k The nth value in the sample, where N is the number of sampling points;

[0027] N c The output sequences of the chaotic orthogonal decoders are ordered at intervals n. s Sampling yields a downsampled sequence y k .

[0028] Furthermore, a received reference sequence and a received information sequence are constructed based on the downsampled sequence, and the information streams of the two channels are decoded sequentially using the received reference sequence and the received information sequence, including:

[0029] The downsampled sequence y k According to N s Each sampling point is split to obtain the received reference sequence and the received information sequence. Symbol decision and information recovery of information stream B in channel two are performed through relevant operations.

[0030] Multiply the received information sequence by the kth information b in information stream B of channel two. k Then, summing the result with the received reference sequence and performing a symbol decision, yields the k-th information sequence A of information stream A. k The decoding result of the q-th information in the sequence.

[0031] Furthermore, the received reference sequence and the received information sequence are as follows:

[0032]

[0033] Where y k (N s ) is a downsampled sequence y k The Nth s One signal;

[0034] The following operations are performed on the received reference sequence and the received information sequence:

[0035]

[0036] Among them, the superscript T r Indicates the transpose operation;

[0037] The kth information b in information flow B of channel two k Decode according to the following formula:

[0038]

[0039] The decoding process for information stream B has ended.

[0040] Furthermore, the decoding process for information stream A in channel one is as follows:

[0041]

[0042] The k-th information sequence A of information flow A k The q-th information in the stream is decoded according to the following formula to obtain the decoding result, thus completing the decoding of information stream A:

[0043]

[0044] in, for The qth piece of information.

[0045] A dual-channel spread spectrum communication system based on chaotic orthogonal coding includes a transmitter and a receiver, wherein:

[0046] The transmitter is used to acquire the information streams of two channels; the information streams of the two channels are spread spectrum mapped to obtain multiple spread spectrum sequences; the multiple spread spectrum sequences are sequentially encoded by the chaotic basis sequences of the chaotic orthogonal encoder group to obtain the output sequence; the output sequences are superimposed to obtain the encoded signal, and the encoded signal is transmitted after the first preprocessing.

[0047] The receiving end is used to obtain a sampling sequence after the received signal undergoes a second preprocessing step. The sampling sequence is then processed by a chaotic orthogonal decoder and downsampled to obtain a downsampled sequence. A receiving reference sequence and a receiving information sequence are constructed based on the downsampled sequence, and the information streams of the two channels are decoded sequentially using the receiving reference sequence and the receiving information sequence.

[0048] The design method for the chaotic basis sequence is as follows:

[0049] At the transmitting end, a chaotic sequence is generated by triggering a chaotic mapping using a preset key. The chaotic sequence is then orthogonalized by Schmitt to obtain multiple sets of mutually orthogonal chaotic orthogonal sequences. Different combinations of chaotic orthogonal sequences serve as the chaotic basis sequences of the chaotic orthogonal encoder group.

[0050] 1. The transmitter of this invention employs a chaotic quadrature encoder to achieve dual-channel information flow transmission. One channel transmits information via a DCSK reference sequence, and the other channel transmits spread spectrum information via a DCSK information sequence. Compared to similar solutions, the above system adds an extra channel for information transmission, improving communication speed while ensuring communication reliability through the additional spread spectrum channel. Both signals can be encrypted and protected using a key.

[0051] 2. The receiver of this invention multiplies the decoded DCSK information with the received information sequence and then sums it with the reference signal, effectively enhancing the signal-to-noise ratio of the received reference signal and reducing the bit error rate of that channel. Compared to traditional DCSK systems that cannot simultaneously transmit information from two channels, this invention cannot achieve similar optimization effects. Through its dual-channel design, this invention not only achieves parallel information transmission but also exhibits extremely low bit error rates on both channels, significantly improving the overall performance and reliability of the communication system. Attached Figure Description

[0052] Figure 1 This is a block diagram of the sending end of the method of the present invention;

[0053] Figure 2This is a block diagram of the receiving end of the method of the present invention;

[0054] Figure 3 It is the output sequence of a chaotic system;

[0055] Figure 4 It is the recombined chaotic basis sequence p1;

[0056] Figure 5 It is the recombined chaotic basis sequence p2;

[0057] Figure 6 It is the recombined chaotic basis sequence p3;

[0058] Figure 7 It is the first output sequence u1 after passing through the chaotic orthogonal encoder;

[0059] Figure 8 It is the first output sequence u2 after passing through the chaotic orthogonal encoder;

[0060] Figure 9 It is the first output sequence u3 after passing through the chaotic orthogonal encoder;

[0061] Figure 10 It is the mixed coded signal s(n);

[0062] Figure 11 It is the output signal after passing through a square root raised cosine filter;

[0063] Figure 12 It is the transmitted signal after being carrier-embedded;

[0064] Figure 13 It consists of the first chaotic decoding signal ξ1 and the downsampled sequence y1;

[0065] Figure 14 It consists of the second chaotic decoding signal ξ2 and the downsampled sequence y2;

[0066] Figure 15 It consists of the third chaotic decoding signal ξ3 and the downsampled sequence y3;

[0067] Figure 16 These are simulation results for different schemes under Gaussian channel wireless multipath attenuation channel;

[0068] Figure 17 These are simulation results for different schemes under wireless multipath attenuation channels. Detailed Implementation

[0069] See Figure 1 This invention first provides an encrypted dual-channel spread spectrum communication method based on chaotic orthogonal coding, comprising:

[0070] At the transmitting end, information streams from two channels are acquired; the information streams from the two channels are spread spectrum mapped to obtain multiple spread spectrum sequences; the multiple spread spectrum sequences are sequentially encoded by the chaotic basis sequences of a chaotic orthogonal encoder group to obtain output sequences; the output sequences are superimposed to obtain coded signals; the coded signals are transmitted after the first preprocessing.

[0071] At the receiving end, the received signal is preprocessed to obtain a sampling sequence. The sampling sequence is then processed by a chaotic orthogonal decoder and downsampled to obtain a downsampled sequence. A receiving reference sequence and a receiving information sequence are constructed based on the downsampled sequence, and the information streams of the two channels are decoded sequentially using the receiving reference sequence and the receiving information sequence.

[0072] The design method for the chaotic basis sequence is as follows:

[0073] At the transmitting end, a chaotic sequence is generated by triggering a chaotic mapping using a preset key. The chaotic sequence is then orthogonalized by Schmitt to obtain multiple sets of mutually orthogonal chaotic orthogonal sequences. Different combinations of chaotic orthogonal sequences serve as the chaotic basis sequences of the chaotic orthogonal encoder group.

[0074] Figure 1 and Figure 2 The diagrams shown are the system block diagrams for the transmitter and receiver of the present invention. The specific method of the present invention, in conjunction with an embodiment, is as follows:

[0075] Step 1: Configure communication system parameters.

[0076] Set the sampling frequency f of the communication system s Oversampling rate n of chaotic signals s Number of chaotic chips N s Number of orthogonal sequences N c Signal Reconstruction Fragment N T carrier frequency f c Then the length N of the chaotic basis sequence b =n s ×N T The number of chaotic signal sampling points N p =n s ×N T ×N c The system spreading gain L = 2 × N s ×n s System communication rate v b =f s / L×N c ×(1+N s );

[0077] In this embodiment, the sampling frequency f is set. s =40MHz, chaotic signal oversampling rate n s =16, Number of orthogonal sequences Nc =3, Signal Reconstruction Fragment N T =4, carrier frequency f c =5MHz, then the number of sampling points N for the chaotic signal p =192, spreading gain L=96, communication system rate v b =5Mbps;

[0078] Step 2: Given a key as an initial value at the transmitting end, a chaotic sequence is generated through a chaotic system; the chaotic sequence is then orthogonalized by Schmitt to obtain multiple sets of chaotic orthogonal sequences.

[0079] The given key c(1) is fed into the chaotic system as an initial value to generate a system of length N. p The chaotic sequence C = [c(1), c(2), ..., c(N)] p )]; where c(N p ) is the Nth digit in the sequence p A chaotic signal; divide the chaotic sequence C into N equal parts. T ×N c Segment, where the i-th segment is denoted as:

[0080] c i =c(j),(i-1)×n s +1≤j≤i×n s (1)

[0081] Where 1≤i≤N T ×N c ; will N T ×N c The chaotic sequence is fed into equation (2) for Schmitt orthogonalization to obtain the chaotic orthogonal sequence x. i , 1≤i≤N T ×N c .

[0082]

[0083] Where x i (n) represents a chaotic orthogonal sequence x i The nth element (scalar) in the sequence; to find all chaotic orthogonal sequences x i (1≤i≤N T ×N c Reassemble into N in sequence c Group, to obtain N c A chaotic basis sequence:

[0084]

[0085] In this embodiment, it is assumed that the chaotic system is a Logistic mapping, i.e., c(l+1) = 1 - μ × (c(l))2 l = 1, 2, ..., N p -1, μ is a coefficient; and it is assumed that the initial value of the key is c(1) = 0.1, and the resulting chaotic sequence is as follows: Figure 3 As shown, a total of N were generated. p = A chaotic sequence C with 192 sampling points.

[0086] The chaotic sequence C is divided into 12 equal segments, denoted as follows:

[0087] c1 = [c(1), c(2), ..., c(16)]

[0088] c2 = [c(17), c(18), ..., c(32)]

[0089] …

[0090] c 12 = [c(177),c(178),…,c(192)]

[0091] Set [c1,c2,…,c 12 Inputting equation (2) into the Schmitt orthogonalization process yields the orthogonal segment [x1, x2, ..., x...]. 12 Then, according to equation (3), the orthogonal segments [x1,x2,…,x] are... 12 Reorganized into N c = 3 chaotic basis sequences, namely:

[0092] p1 = [x1, x2, ..., x4]

[0093] p2 = [x5, x6, ..., x8]

[0094] p3 = [x9, x 10 ,…,x 12 ],

[0095] Among them, the chaotic basis sequence p k (1≤k≤N c There are n s ×N T = 64 sampling points; the generated chaotic basis sequences p1, p2, p3 are respectively as follows Figure 4 , Figure 5 , Figure 6 As shown.

[0096] Step 3: The transmitter prepares two channels (referred to as Channel 1 and Channel 2) for information flow A = [A1, A2, ..., A...]. k ,…,A Nc ] Tr and B = [b1, b2, ..., b k ,…,b Nc ] TrA k =[a k,1 ,a k,2 ,…a k,Ns ] represents the k-th (1≤k≤N) node in information flow A. c ) information sequences, a k,Ns A represents k The Nth s N binary bits; s For the k-th sequence A k The number of bits transmitted (also the number of chaotic chips in step 1); b k N represents the k-th binary bit in information stream B, and the superscript Tr is defined as the transpose symbol; c The number of bits transmitted in channel 2 and the number of information sequences transmitted in channel 1 (also the number of orthogonal sequences mentioned in step 1), where the k-th information sequence A in channel 1... k N were transmitted s 1 binary bit.

[0097] If information streams A and B are spread spectrum mapped, then the k-th (1≤k≤N) c The spread spectrum sequence for 10-way transmission can be represented as:

[0098] D k = [d k,1 , d k,2 , …, d k,m , …, d k,2Ns (4)

[0099] =[A k A k ×b k ]

[0100] =[a k,1 ,a k,2 ,…a k,Ns ,(a k,1 ,a k,2 ,…a k,Ns )×b k ]

[0101] In the embodiment, the k-th information sequence A k Number of bits transmitted N s =3, Number of orthogonal sequences N c =3; Assuming the information to be transmitted:

[0102]

[0103] And B = [b1, b2, b3] = [1 1 -1] Tr .

[0104] By feeding information streams A and B into equation (4) for spread spectrum mapping, we can obtain...

[0105] D1 = [d 1,1 ,d 1,2 ,d 1,3 ,d 1,4 ,d 1,5 ,d 1,6 ] = [a 1,1 ,a 1,2 ,a 1,3 ,(a 1,1 ,a 1,2 ,a 1,3 )×b1]

[0106] =[1 -1 1 1 -1 1]

[0107] D2 = [1 1 -1 1 1 -1]

[0108] D3 = [-1 1 1 1 -1-1].

[0109] Step 4: The spread spectrum mapping sequence is fed into the following Chaotic Orthogonal Encoder (COE) group, and the transmitted signal is obtained by encoding using the chaotic basis sequence. The transmitted signals output by the Chaotic Orthogonal Encoder group are mutually orthogonal, and multiple channels of information can be transmitted simultaneously.

[0110]

[0111] Where u k (n)(1≤k≤N c (1≤n≤N) represents the output sequence u of the k-th chaotic orthogonal encoder. k =[u k (1),u k (2),…,u k The nth value in [(N)], N = n s ×N T +2×L-1;d k,m For the k-th spreading sequence D k The m-th symbol in p k (n) represents the k-th chaotic basis sequence p in step 2. k The nth value in.

[0112] In the embodiment, the spread spectrum mapping sequences D1, D2, and D3 are respectively fed into the chaotic quadrature encoder of equation (5), and the output signals u1, u2, and u3 are respectively as follows: Figure 7 , Figure 8 and Figure 9 As shown.

[0113] Step 5: Prepare the encoded signal and complete the first preprocessing by passing it through a square root raised cosine filter (SRRC) and uploading operation, and then transmit it to the wireless channel via radio frequency.

[0114] N c The encoded signal s(n) is obtained by superimposing the output signals of the chaotic quadrature encoder, as follows:

[0115]

[0116] The encoded signal is then processed by SRRC and upcarrier operations, and transmitted to the wireless channel via an RF antenna. Since the SRRC and upcarrier operations at the transmitter, and the downcarrier and matched filter (MF) operations at the receiver, are fundamental operations in the field of communications, the specific operational procedures will not be elaborated further.

[0117] In the embodiment, Figure 7 , Figure 8 , Figure 9 The superposition of u1(n), u2(n), and u3(n) yields the coded signal as follows: Figure 10 As shown. The encoded signal s(n) is fed into the SRRC to obtain the filtered output signal, as shown. Figure 11 As shown. The filtered output signal uses a frequency of f. c =5MHz upcarrier signal is transmitted into the wireless channel, such as Figure 12 As shown;

[0118] Step 6: The receiver acquires the received signal r(t) from the wireless channel, processes it through a download waveform and a matched filter (corresponding to the transmitter's SRRC), and then samples the filtered output signal at a sampling frequency f. s After sampling, the second preprocessing is completed to obtain the sampled sequence r; a Chaotic Orthogonal Decoder (COD) is constructed to decode the sampled sequence r, and the decoded output sequence is downsampled to obtain the downsampled sequence.

[0119] The expression for the chaotic orthogonal decoder is as follows, where the output sequence ξ of the k-th chaotic orthogonal decoder is... k (1≤k≤N c The o-th (1≤o≤2N) in ) s ×n s ) values ​​ξ k (o) is as follows:

[0120]

[0121] Where r(n) is the nth value in the sampling sequence r, p k(n) represents the k-th chaotic basis sequence p in step 2. k The nth value in the sample, where N is the number of sampling points, N = n s ×N T +2×L-1.

[0122] N c The output sequences of the chaotic orthogonal decoders are ordered at intervals n. s Sampling yields a downsampled sequence y k =[y k (1),y k (2),…,y k (2N s )], where the m-th (1≤m≤2N) s The sample values ​​are:

[0123]

[0124] In this embodiment, to illustrate the details of signal processing at the receiver, it is assumed that the received signal is unaffected by channel interference. The download waveform and matched filtering processes will not be described in detail.

[0125] The output signal, after being processed by the download waveform and passed through a matched filter, is processed according to f. s Sampling yields a sampling sequence r; inputting r into equation (7) yields N. c =The output sequences y1, y2, y3 of the three chaotic orthogonal decoders are respectively as follows Figure 13 , Figure 14 and Figure 15 The "dot + solid line" indicates the sampled output sequences of the three decoders according to equation (8). Based on the parameter configuration in step 1, the sampling point index values ​​and corresponding sampled values ​​are shown in Table 1 and... Figure 13 , Figure 14 , Figure 15 As shown in the Chinese box;

[0126] Table 1 shows the downsampling sequence of the matched filter output signal in the embodiments.

[0127]

[0128]

[0129] A received reference sequence and a received information sequence are constructed based on the downsampled sequence; correlation operations are performed using the received reference sequence and the received information sequence to decode the information of one channel; the decoded information is multiplied by the received information sequence and then added to the received reference sequence to decode the information of another channel; the details are as follows:

[0130] Step 7, downsample the sequence y k According to N sEach sampling point is split to obtain the received reference sequence and the received information sequence. Symbol decision and information recovery of channel two are performed through relevant operations. The received reference sequence and the received information sequence are as follows:

[0131]

[0132] The following operations are performed on the received reference sequence and the received information sequence:

[0133]

[0134] The kth information b in the information flow of channel two k Decode according to the following formula:

[0135]

[0136] The decoding process for information stream B has ended.

[0137] In the embodiment, the downsampling sequence y is processed according to equation (9). k The sequence is divided into a received reference sequence and a received information sequence as follows:

[0138]

[0139] Substituting it into equation (10), we get:

[0140]

[0141] Substituting the decision variable into equation (11) yields the decoded information flow. as follows:

[0142]

[0143] Step 8, the decoding process of information stream A in channel one is as follows: multiply the received information sequence by the decoded information. Then sum it with the received reference sequence, as follows:

[0144]

[0145] The k-th (1≤k≤N)th information flow A c ) Road information sequence A k The qth (1≤q≤N) in s The information is decoded according to the following formula to obtain the decoding result:

[0146]

[0147] The decoding process is now complete.

[0148] In the embodiment, the three information streams A can be obtained according to equation (12). k Decision variables

[0149]

[0150] Substituting it into equation (13) yields the recovered information flow. as follows

[0151]

[0152] The decoding process for information stream A has ended.

[0153] The simulation results of the performance of the proposed scheme and the comparative scheme DCSK in a Gaussian channel are as follows: Figure 16 As shown, the system parameters are set as follows in the simulation: sampling frequency f s =40MHz, chaotic signal oversampling rate n s =16, signal reconstruction fragment N T =4, spreading gain L=96, and the number of orthogonal sequences are N respectively. c =1 and 3. The DCSK system is set with a spreading gain L = 96, meaning the DCSK system communication rate is the same as the information flow B communication rate in this invention. It can be seen that in a Gaussian channel, information flows A and B in this invention are at N... c When the signal-to-noise ratio (SNR) is 1 and 3, the bit error rates are similar. Meanwhile, at high SNR, information stream B exhibits slightly better bit error performance than information stream A; at low SNR, information stream A exhibits slightly better bit error performance than information stream B. Information streams A and B show lower bit error rates compared to the DCSK scheme.

[0154] The simulation results of the performance of the proposed scheme and the comparative scheme DCSK in a multipath attenuation channel are as follows: Figure 17 As shown. The average power gains of the multipath fading channel are E1 = 0.6, E2 = 0.3, and E3 = 0.1, with corresponding delays of τ1 = 0 μs, τ2 = 2.5 μs, and τ3 = 5 μs, respectively. Other system simulation parameters are set consistent with those of the Gaussian channel. Simulation results show that under the multipath fading channel, the bit error rate performance of all schemes deteriorates to varying degrees, N c When the error rate is 4, the bit error rates of information streams A and B are compared to N. c The degradation is more severe when the value is 1, but it is still significantly better than the error rate performance of DCSK.

[0155] In summary, this invention uses an arbitrarily preset trigger signal as the initial value of the chaotic system, and the generated chaotic signal is used to construct a chaotic orthogonal encoder group. This invention enables the simultaneous transmission of two channel information streams. After spreading and mapping, the two channel information streams are fed into the corresponding chaotic orthogonal encoders. The encoder output sequences have orthogonal characteristics, allowing for the orthogonal superposition of multiple encoder output signals. Compared to traditional spread spectrum communication schemes and chaotic differential keying schemes, this invention significantly improves the communication system speed. Simultaneously, the receiver employs a corresponding chaotic decoder and signal accumulation, doubling the signal-to-noise ratio of the received signal from one channel information stream, further reducing the bit error rate of the communication system compared to the DCSK system.

[0156] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for encrypted dual-channel spread spectrum communication based on chaotic orthogonal coding, characterized in that, include: Acquire the information streams from two channels at the transmitting end; The information streams from the two channels are spread spectrum mapped to obtain a multi-channel spread spectrum sequence. The output sequence is obtained by sequentially encoding the multi-channel spread spectrum sequence through the chaotic basis sequence of the chaotic orthogonal encoder group; The output sequences are superimposed to obtain an encoded signal, which is then sent after a first preprocessing step. At the receiving end, the received signal is processed through a second preprocessing step to obtain a sampling sequence. The sampling sequence is then processed through a chaotic orthogonal decoder and downsampled to obtain a downsampled sequence. A receiving reference sequence and a receiving information sequence are constructed based on the downsampling sequence, and the information streams of the two channels are decoded sequentially using the receiving reference sequence and the receiving information sequence. The design method for the chaotic basis sequence is as follows: At the transmitting end, a chaotic sequence is generated by triggering a chaotic mapping using a preset key. The chaotic sequence is then orthogonalized by Schmitt to obtain multiple sets of mutually orthogonal chaotic orthogonal sequences. Different combinations of chaotic orthogonal sequences serve as the chaotic basis sequences of the chaotic orthogonal encoder group.

2. The encrypted dual-channel spread spectrum communication method based on chaotic orthogonal coding according to claim 1, characterized in that, The given key is fed into the chaotic system as an initial value, generating a sequence of length... N p A chaotic sequence C; where N p Indicates the number of sampling points for the chaotic signal; Divide the chaotic sequence C into equal parts N T × N c The segmented sequence is then subjected to Schmitt orthogonalization to obtain the chaotic orthogonal sequence x corresponding to each segment. i ;in N T Indicates a reconstructed signal segment. N c Indicates the number of orthogonal sequences; All chaotic orthogonal sequences x i Reassemble in order N c Group, get N c A chaotic basis sequence.

3. The encrypted dual-channel spread spectrum communication method based on chaotic orthogonal coding according to claim 1, characterized in that, The information streams from the two channels are spread spectrum mapped to obtain a multi-channel spread spectrum sequence, including: The two channels are Channel 1 for sending information stream A and Channel 2 for sending information stream B; Information flow A = [A1, A2, …, A k , …, A Nc ] Tr B = [ b 1, b 2, …, b k ,…, b Nc ] Tr ;where A k Indicates the first in information flow A k A sequence of information, 1≤ k ≤ N c ; b k This indicates the first [item] in information flow B. k One binary bit, Tr Defined as the transpose symbol; N c This refers to the number of bits transmitted in channel two and the number of information sequences transmitted in channel one. If information streams A and B are spread spectrum mapped, then the first... k The spread spectrum sequence for the path transmission is represented as: D k = [A k , A k × b k ]。 4. The encrypted dual-channel spread spectrum communication method based on chaotic orthogonal coding according to claim 1, characterized in that, The output sequence is obtained by sequentially encoding the multi-channel spread spectrum sequences using the chaotic basis sequences of a chaotic orthogonal encoder group, and is represented as follows: in, u k ( n ) is the first k The output sequence u of a chaotic orthogonal encoder k The first in n There are 1 values, 1 ≤ k ≤ N c , 1≤ n ≤ N ; N = n s × N T + 2× L- 1; n s For chaotic signals, the oversampling rate L For system spread spectrum gain; d k,m For the first k Path spread spectrum sequence D k The first in m A symbol, For the first k chaotic basis sequences The first in n One value, N s For the first k Road information sequence A k The number of bits transmitted.

5. The encrypted dual-channel spread spectrum communication method based on chaotic orthogonal coding according to claim 1, characterized in that, The first preprocessing consists of SRRC and upcarrier operation; the second preprocessing consists of downloading, matched filtering, and sampling operation.

6. The encrypted dual-channel spread spectrum communication method based on chaotic orthogonal coding according to claim 1, characterized in that, The chaotic orthogonal decoder decodes the sampled sequence, and the expression for the output sequence is: No. k The output sequence ξ of a chaotic orthogonal decoder k (1≤ k ≤ N c The first in ) o (1≤ o ≤2 N s × n s ) values ξ k ( o )as follows: in For the sampling sequence r, the first... n One value, For the first k chaotic basis sequences The first in n One value, N This represents the number of sampling points; Will N c The output sequences of the chaotic orthogonal decoder are arranged according to intervals. n s Sampling yields a downsampled sequence y k .

7. The encrypted dual-channel spread spectrum communication method based on chaotic orthogonal coding according to claim 1, characterized in that, A receive reference sequence and a receive information sequence are constructed based on the downsampled sequence, and the information streams of the two channels are decoded sequentially using the receive reference sequence and the receive information sequence, including: The downsampled sequence y k according to N s Each sampling point is split to obtain the received reference sequence and the received information sequence. Symbol decision and information recovery of information stream B in channel two are performed through relevant operations. Multiply the received information sequence by the first value of information stream B in channel two. k Information b k Then, sum the result with the received reference sequence and perform a symbol decision to obtain the first symbol of information stream A. k Road information sequence A k The first in q The decoding result of the information.

8. The encrypted dual-channel spread spectrum communication method based on chaotic orthogonal coding according to claim 1, characterized in that, The received reference sequence and received information sequence are as follows: in For downsampled sequence y k The first in One signal; The following operations are performed on the received reference sequence and the received information sequence: Among them, superscript T r Indicates the transpose operation; The first information flow B in channel two k Information b k Decode according to the following formula: The decoding process for information stream B has ended.

9. The encrypted dual-channel spread spectrum communication method based on chaotic orthogonal coding according to claim 1, characterized in that, The decoding process of information stream A in channel one is as follows: Information flow A's k Road information sequence A k The first in q The information is decoded according to the following formula to obtain the decoding result, thus completing the decoding of information stream A: in, for The qth piece of information.

10. A dual-channel spread spectrum communication system based on chaotic orthogonal coding, characterized in that, Includes the transmitter and receiver, wherein: The transmitter is used to acquire the information streams of two channels; the information streams of the two channels are spread spectrum mapped to obtain multiple spread spectrum sequences; the multiple spread spectrum sequences are sequentially encoded by the chaotic basis sequences of the chaotic orthogonal encoder group to obtain the output sequence; the output sequences are superimposed to obtain the encoded signal, and the encoded signal is transmitted after the first preprocessing. The receiving end is used to obtain a sampling sequence after the received signal undergoes a second preprocessing step. The sampling sequence is then processed by a chaotic orthogonal decoder and downsampled to obtain a downsampled sequence. A receiving reference sequence and a receiving information sequence are constructed based on the downsampled sequence, and the information streams of the two channels are decoded sequentially using the receiving reference sequence and the receiving information sequence. The design method for the chaotic basis sequence is as follows: At the transmitting end, a chaotic sequence is generated by triggering a chaotic mapping using a preset key. The chaotic sequence is then orthogonalized by Schmitt to obtain multiple sets of mutually orthogonal chaotic orthogonal sequences. Different combinations of chaotic orthogonal sequences serve as the chaotic basis sequences of the chaotic orthogonal encoder group.

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