Encrypted dual-channel spread spectrum communication method and system based on chaotic orthogonal coding

Abstract

The invention discloses an encrypted dual-channel spread spectrum communication method based on chaotic orthogonal coding, which comprises the following steps of: acquiring information streams of two channels at a transmitting end, after spread spectrum mapping, coding through a chaotic base sequence of a chaotic orthogonal coder group to obtain an output sequence, and superposing to obtain a coded signal, the coded signal is sent after being subjected to first preprocessing; at a receiving end, performing second preprocessing on the received signal to obtain a sampling sequence, and performing decoding and down-sampling processing to obtain a down-sampling sequence; constructing a receiving reference sequence and a receiving information sequence, and decoding the information streams of the two channels in sequence by using the receiving reference sequence and the receiving information sequence; wherein the design method of the chaos base sequence comprises the following steps: triggering chaos mapping at a transmitting end by using a preset key to generate a chaos sequence, and performing Schmidt orthogonalization on the chaos sequence to obtain a plurality of groups of chaos orthogonal sequences which are mutually orthogonal; and different chaotic orthogonal sequence combinations are used as chaotic base sequences of the chaotic orthogonal encoder group.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of chaotic spread spectrum communication, and relates to an encrypted double-channel spread spectrum communication method and system based on chaotic orthogonal coding. BACKGROUND

[0002] In recent two decades, chaotic communication systems have attracted extensive attention from researchers. A series of chaotic spread spectrum communication schemes represented by differential chaos shift keying (DCSK) systems have been widely recognized in the industry for their high reliability in complex wireless channels. With the development of digitization and informatization, chaotic communication systems have shown great application potential in the fields of Internet of Things, satellite communication, underwater communication, etc. In recent years, with the in-depth research, the performance of chaotic communication systems has been further improved. The introduction of new chaotic modulation, demodulation techniques and signal processing methods has significantly improved the transmission rate, bit error rate and anti-interference ability of chaotic communication.

[0003] Existing spread spectrum communication schemes based on DCSK generally use Logistic mapping or Lorenz system as discrete / continuous signals as communication carriers. The chaotic signal cannot exhibit "ideal" orthogonality, and therefore introduces intra-symbol interference in the modulated signal. At the same time, the DCSK communication system greatly reduces the communication rate because it needs to transmit reference signals that do not carry information. SUMMARY

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

[0005] In order to achieve the above-mentioned task, the present application adopts the following technical solutions:

[0006] An encrypted double-channel spread spectrum communication method based on chaotic orthogonal coding, comprising:

[0007] At the transmitting end, the information streams of two channels are obtained; the information streams of the two channels are spread spectrum mapped to obtain multiple spread spectrum sequences; the multiple spread spectrum sequences are sequentially coded by the chaotic base sequences of a chaotic orthogonal encoder group to obtain output sequences; after superposition of each output sequence, a coded signal is obtained, and the coded signal is sent after first preprocessing;

[0008] At the receiving end, after the received signal is secondly preprocessed, a sampling sequence is obtained, and after the sampling sequence is processed by a chaotic orthogonal decoder and down-sampling, a down-sampled sequence is obtained; a received reference sequence and a received information sequence are constructed based on the down-sampled sequence, and the information streams of the two channels are sequentially decoded using the received reference sequence and the received 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] Further, the received reference sequence and the received information sequence are constructed based on the down-sampling sequence, and the information streams of the two channels are decoded in turn using the received reference sequence and the received information sequence, including:

[0029] The down-sampling sequence y k is split into the received reference sequence and the received information sequence according to N s sampling points, and the symbol decision and information recovery of the information stream B in channel two are performed through correlation operation.

[0030] The received information sequence is multiplied by the kth information b k of the information stream B in channel two, and then summed with the received reference sequence and subjected to symbol decision to obtain the decoding result of the qth information in the kth information sequence A k of the information stream A.

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

[0032]

[0033] Where y k (N s ) is the N k th signal in the down-sampling sequence y s .

[0034] The received reference sequence and the received information sequence are subjected to the following correlation operation:

[0035]

[0036] Where the superscript T r represents the transpose operation.

[0037] The kth information b k of the information stream B in channel two is decoded according to the following formula:

[0038]

[0039] The decoding process of the information stream B is completed.

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

[0041]

[0042] The qth information in the kth information sequence A k of the information stream A is decoded according to the following formula to obtain the decoding result and complete the decoding of the information stream A:

[0043]

[0044] Where, For The qth information in the middle.

[0045] A chaotic orthogonal encoding-based encrypted dual-channel spread spectrum communication system, comprising a transmitting end and a receiving end, wherein:

[0046] The transmitting end is configured to obtain two-channel information streams; the two-channel information streams are subjected to spread spectrum mapping to obtain multiple spread spectrum sequences; the multiple spread spectrum sequences are sequentially encoded by chaotic base sequences of a chaotic orthogonal encoder group to obtain output sequences; the output sequences are superimposed to obtain an encoded signal, and the encoded signal is subjected to first preprocessing and then transmitted;

[0047] The receiving end is configured to obtain a sampling sequence by subjecting a received signal to second preprocessing, and obtain a down-sampling sequence by subjecting the sampling sequence to chaotic orthogonal decoding and down-sampling; a receiving reference sequence and a receiving information sequence are constructed based on the down-sampling sequence, and the two-channel information streams are sequentially decoded by using the receiving reference sequence and the receiving information sequence;

[0048] The chaotic base sequences are designed as follows:

[0049] In the transmitting end, a chaotic sequence is generated by triggering chaotic mapping by using a preset key, and the chaotic sequence is subjected to Schmidt orthogonalization to obtain multiple groups of chaotic orthogonal sequences that are mutually orthogonal; different groups of chaotic orthogonal sequences are combined as chaotic base sequences of the chaotic orthogonal encoder group.

[0050] 1. The transmitting end of the present application realizes dual-channel transmission of information streams by using chaotic orthogonal encoders, wherein one channel transmits information by using a DCSK reference sequence, and the other channel transmits spread spectrum information by using a DCSK information sequence. Compared with similar schemes, the above system additionally transmits information by using one channel, thereby improving the communication rate and providing another spread spectrum channel to ensure the communication reliability, and both signals can be encrypted by using a key.

[0051] 2. The receiving end of the present application multiplies the decoded information of DCSK with a receiving information sequence, and then sums the result with a reference signal, thereby effectively enhancing the signal-to-noise ratio of the receiving reference signal and reducing the error rate of the channel. Compared with the conventional DCSK system that cannot simultaneously transmit two-channel information, the present application cannot achieve similar optimization effects. The present application realizes parallel transmission of information by using a dual-channel design, and exhibits extremely low error rates on both channels, thereby greatly improving the overall performance and reliability of the communication system. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 is a transmitting end block diagram of the method of the present application;

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

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

[0055] Figure 4 is a recombined chaotic base sequence p1;

[0056] Figure 5 is a recombined chaotic base sequence p2;

[0057] Figure 6 is a recombined chaotic base sequence p3;

[0058] Figure 7 is a first path output sequence u1 through a chaotic orthogonal encoder;

[0059] Figure 8 is a first path output sequence u2 through a chaotic orthogonal encoder;

[0060] Figure 9 is a first path output sequence u3 through a chaotic orthogonal encoder;

[0061] Figure 10 is a mixed encoded signal s(n);

[0062] Figure 11 is an output signal through a square root raised cosine filter;

[0063] Figure 12 is a transmitted signal after up-conversion;

[0064] Figure 13 is a first path chaotic decoded signal ξ1 and a down-sampled sequence y1;

[0065] Figure 14 is a second path chaotic decoded signal ξ2 and a down-sampled sequence y2;

[0066] Figure 15 is a third path chaotic decoded signal ξ3 and a down-sampled sequence y3;

[0067] Figure 16 is a simulation result of different schemes under a wireless multipath fading channel of a Gaussian channel;

[0068] Figure 17 is a simulation result of different schemes under a wireless multipath fading channel. DETAILED DESCRIPTION

[0069] Referring to Figure 1 , the present application first provides an encrypted dual-channel spread spectrum communication method based on chaotic orthogonal encoding, 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 assuming the initial value c(l) = 0.1 as a key, the generated chaotic sequence is as shown in Figure 3 p = 192 sampling points of chaotic sequence C.

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

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

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

[0089] ...

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

[0091] Send [c1, c2,..., c 12 ] into equation (2) for Schmidt orthogonalization, to obtain the orthogonal segments [x1, x2,..., x 12 ]. Then, according to equation (3), the orthogonal segments [x1, x2,..., x 12 ] are recombined into N c = 3 chaotic base sequences, respectively:

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

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

[0094] p3= [x9, x 10 ,..., x 12 ],

[0095] where the chaotic base sequence p k (1≤k≤N c ) has n s ×N T = 64 sampling points; the generated chaotic base sequences p1, p2, p3 are respectively as shown in Figure 4 、 Figure 5 、 Figure 6 .

[0096] Step 3, the transmitting end prepares two channel (denoted as channel one, channel two) information streams A = [A1, A2,..., A k ,..., A Nc ] Tr and B = [b1, b2,..., b k ,..., b Nc ] Tr ​where A k = [a k,1 ,a k,2 ,…a k,Ns ] represents the kth (1≤k≤N c ) information sequence in information stream A, a k,Ns represents the N k th binary bit in A s ; N s is the number of bits transmitted by the kth sequence A k (in the number of chaotic chips in step 1); b k represents the kth binary bit in information stream B, and the superscript Tr is defined as the transpose symbol; N c is the number of bits transmitted by channel two and the number of information sequences transmitted by channel one (also the number of orthogonal sequences described in step 1), wherein the kth information sequence A k in channel one transmits N s binary bits.

[0097] After spreading mapping of information streams A and B, the kth (1≤k≤N c ) spreading sequence transmitted 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 an embodiment, the number of bits N k transmitted by the kth information sequence A s = 3, the 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] The information streams A and B are sent into equation (4) for spread spectrum mapping, and the following can be obtained

[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 ) x 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 sent into a chaotic orthogonal encoder group (COE) as shown below, and a transmission signal is obtained by encoding using a chaotic base sequence. The transmission signals output by the chaotic orthogonal encoder group are mutually orthogonal, and multiple information streams can be transmitted simultaneously.

[0110]

[0111] where u k (n) (1≤k≤N c , 1≤n≤N) is the nth value in the output sequence u k = [u k (1), u k (2),..., u k (N)] output by the kth chaotic orthogonal encoder, and N = n s x N T + 2 x L - 1; d k,m is the mth symbol in the kth spread spectrum sequence D k , and p k (n) is the nth value in the kth chaotic base sequence p k in step 2.

[0112] In the embodiment, the spread spectrum mapping sequences D1, D2, and D3 are respectively sent into the chaotic orthogonal encoders of equation (5), and the output signals u1, u2, and u3 are respectively as shown in Figure 7 , Figure 8 and Figure 9 .

[0113] Step 5: Prepare the encoded signal and complete the first preprocessing by passing it through a square root raised cosine (SRRC) filter 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 encoded 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 sThe received reference sequence and the received information sequence are obtained by splitting the sampling point, and the symbol decision and information recovery of the second channel are performed through correlation operation. The received reference sequence and the received information sequence are as follows:

[0131]

[0132] The received reference sequence and the received information sequence are subjected to the following correlation operation:

[0133]

[0134] The kth information b k of the information stream in the second channel is decoded according to the following formula:

[0135]

[0136] The information stream B decoding process is completed.

[0137] In an embodiment, the down-sampling sequence y k is split into a received reference sequence and a received information sequence as follows:

[0138]

[0139] The formula (10) is obtained by bringing it into the formula (10):

[0140]

[0141] The decoded information stream b is obtained by bringing the decision variable into the formula (11) as follows:

[0142]

[0143] Step 8, the information stream A decoding process of the first channel is: the received information sequence is multiplied by the decoded information , and then summed with the received reference sequence, as follows:

[0144]

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

[0146]

[0147] Up to now, the decoding process is completed.

[0148] In an embodiment, the decision variable of the 3-way information stream A k is obtained according to the formula (12)

[0149]

[0150] Substitute it into equation (13) to obtain the recovered information stream As follows

[0151]

[0152] The information stream A decoding process ends.

[0153] The performance simulation results of the scheme of the application and the comparative scheme DCSK in a Gaussian channel are as shown in the following table: Figure 16 The system parameters are set as follows in the simulation: the sampling frequency f s = 40 MHz, the oversampling rate n s of the chaotic signal = 16, the signal recombination segment N T = 4, the spreading gain L = 96, and the number of orthogonal sequences N c = 1 and 3. The spreading gain L of the DCSK system is set to 96, i.e., the communication rate of the DCSK system is the same as that of the information stream B in the scheme of the application. It can be seen that in the Gaussian channel, the bit error rates of the information streams A and B in the scheme of the application are similar when N c = 1 and 3. Meanwhile, the bit error performance of the information stream B is slightly better than that of the information stream A at a high signal-to-noise ratio, and the bit error performance of the information stream A is slightly better than that of the information stream B at a low signal-to-noise ratio. The information streams A and B show lower bit error rates than the DCSK scheme.

[0154] The performance simulation results of the scheme of the application and the comparative scheme DCSK in a multipath fading channel are as shown in the following table: Figure 17 The multipath fading channel has an average power gain E1 = 0.6, E2 = 0.3, and E3 = 0.1, and the corresponding time delays are τ1 = 0 μs, τ2 = 2.5 μs, and τ2 = 5 μs, respectively. The other system simulation parameters are set the same as in the Gaussian channel. It can be seen from the simulation results that in the multipath fading channel, the bit error performances of all the schemes deteriorate to different degrees, and the bit error rates of the information streams A and B when N c = 4 are more serious than those when N c = 1, but are obviously better than the bit error performance of the DCSK.

[0155] In summary, the scheme of the present application generates chaotic signals by using any preset trigger signal as the initial value of the chaotic system, and uses the chaotic signals to construct a chaotic orthogonal encoder group. The scheme of the present application realizes the simultaneous transmission of two-channel information streams. After the two-channel information streams are spread and mapped, they are sent to the corresponding chaotic orthogonal encoders. The output sequence of the encoders has orthogonal characteristics, and the orthogonal superposition of multiple encoder output signals can be realized. Compared with the traditional spread spectrum communication scheme and the chaotic differential keying scheme, the scheme of the present application greatly improves the rate of the communication system. At the same time, the receiver uses the corresponding chaotic decoder and signal accumulation, so that the signal-to-noise ratio of the received signal of one of the two-channel information streams is improved by one time, and compared with the DCSK system, the bit error rate of the communication system is further reduced.

[0156] The above examples are only used to illustrate the technical solutions of the present application, but not limit the same; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present 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 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; 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; All chaotic orthogonal sequences x i Reassemble into N in order. c Group, to obtain 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 = [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. If information streams A and B are spread spectrum mapped, then the spread spectrum sequence of the k-th transmission can be 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: 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.

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: 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: 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; N c The output sequences of the chaotic orthogonal decoders are ordered at 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 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.

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: Where y k (N s ) is a downsampled sequence y k The Nth s One signal; The following operations are performed on the received reference sequence and the received information sequence: Among them, the superscript T r Indicates the transpose operation; The kth information b in information flow B of channel two 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: 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: 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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