Transmission method based on WFRFT parameter control of multi-sequence spread spectrum

Abstract

The invention relates to a transmission method based on WFRFT parameter control of multi-sequence spread spectrum, which belongs to the field of communication signal processing. The invention solves the problem that the existing multi-base spread spectrum method cannot take into account both transmission efficiency and system complexity. For the transmitter, the method of the invention divides the encoded information into modulation information and mapping information, carries multi-bit binary numbers, and the mapping parameter α input to the transmitter WFRFT module is k The WFRFT parameter identification module determines the demapping parameters for the received signal within the current time period based on the M correlation values ​​corresponding to the bit synchronization moment, thereby improving transmission efficiency. This reduces the complexity of the receiving end. This invention is primarily applicable to high-efficiency, low-interception information transmission and signal processing in the communications field.

Description

Technical Field

[0001] The invention belongs to the field of communication signal processing. Background Art

[0002] Direct Sequence Spread Spectrum (DSSS), a representative technology for third-generation mobile communications, was once widely researched and applied in commercial communications. However, its information modulation principle—where a single information bit is spread by a long sequence (the spreading sequence) into a single spread spectrum symbol for transmission—significantly reduced data transmission rates. Therefore, fourth-generation and later commercial mobile communication systems switched to the more efficient OFDM and single-carrier frequency-domain equalization schemes. Despite this, spread spectrum communication continues to be used as a covert communication system in military communications due to its inherent interference resistance, multipath mitigation, and ability to communicate even at extremely low signal-to-noise ratios.

[0003] Since spread-spectrum transmission systems are used as a covert system in specialized fields, the study of methods for intercepting spread-spectrum signals has naturally become a research area. Currently, relatively comprehensive algorithms and schemes exist for estimating parameters such as the spreading code sequence, spreading period, and chip rate. Most algorithms for estimating spread-spectrum signal parameters exploit the good correlation between the spreading code and itself, as well as the cyclostationary properties of the signal, resulting from the repetitive and periodic appearance of a single sequence within the spread-spectrum signal. To this end, researchers have proposed techniques such as combined hop-spreading and cyclic shift keying (CSK) spread spectrum to further improve the anti-interception performance of spread-spectrum systems.

[0004] Traditional direct sequence spread spectrum systems, due to their symbol extension, suffer from low system support rates and low spectrum utilization. The subsequent emergence of multi-level spread spectrum technology and code domain index modulation (CDIM) has improved the transmission efficiency of spread spectrum systems, but still faces the problem of high receiver complexity. Specifically, in multi-level direct sequence spread spectrum systems and CDIM systems, the spreading code groups used by the transmitter are mutually orthogonal code sequences, meaning that the correlation between different spreading codes is zero. While this choice improves system reliability, the receiver must traverse all codewords in all spreading code groups. This means that the receiver needs to establish L (L is the size of the transmitting end's orthogonal code group) parallel branches to perform correlation operations, which undoubtedly greatly increases system complexity. Therefore, the existing multi-level spread spectrum methods urgently need to address the problem of how to balance transmission efficiency and system complexity. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that the existing multi-level spread spectrum method cannot take into account both transmission efficiency and system complexity. The present invention provides a transmission method based on WFRFT parameter control of multi-sequence spread spectrum.

[0006] A transmission method based on WFRFT parameter control of multi-sequence spread spectrum, the transmission method is implemented based on a multi-sequence spread spectrum system, and the multi-sequence spread spectrum system includes a transmitting end and a receiving end;

[0007] (1) The method for transmitting a signal at the transmitting end includes:

[0008] Step A1: The signal source performs source and / or channel coding on the data to be transmitted in the kth time period to obtain coded information, which includes modulation information p k and mapping information b k ; Modulation information p k It is a 1-bit binary number; mapping information b k is a q-bit binary number, where q is an integer;

[0009] Step A2: Modulate the information p through the encoder k Perform polarity coding to obtain modulation information p k The corresponding polar code d k At the same time, the mapping information b is mapped through the parameter mapper k Perform mapping and generate mapping parameter α k ; The WFRFT module at the transmitting end is based on the mapping parameter α k Perform weighted fractional Fourier transform on the spread spectrum sequence v to obtain the precoded spread spectrum sequence c k ; where v=[v1,v2,…,v N ] T ;v n is the chip corresponding to the nth moment in the kth time period in v; n = 1, 2, 3...N, k is a positive integer;

[0010] Step A3: Polar code d k With the precoded spreading sequence c k Multiply them to get the modulated spread spectrum sequence g k ;

[0011] Step A4: Modulate the spread spectrum sequence g k After up-conversion, the obtained RF signal s k (t) send to the channel;

[0012] (2) The method for receiving a signal at a receiving end includes:

[0013] Step B1: Receive radio frequency signal s k (t) RF signal r after propagation through the channel b (t), and the RF signal r is filtered by a broadband filter b (t) After filtering, the filtered signal r is obtained c (t);

[0014] Step B2: filter the signal r c (t) down-converts to obtain the pre-decoded spread spectrum sequence r k ;

[0015] Step B3: Pre-decode the spread spectrum sequence r k The signals are inputted into M correlators in parallel; at the same time, M given precoded spread spectrum sequences are obtained according to M given mapping parameters, and the M given precoded spread spectrum sequences are respectively sent to M correlators;

[0016] Each correlator will pre-decode the spreading sequence r k The given precoded spread spectrum sequence c′ corresponding to the correlator kj Perform relevant operations and get Among them, c′ kj is the given precoded spreading sequence corresponding to the jth correlator, is the correlated sequence output by the jth correlator; is the jth correlator in the kth time period The correlation value corresponding to the nth moment in ; j = 1, 2, 3 ... M, n = 1, 2, 3 ... N;

[0017] Step B4: Compare the maximum modulus value of the M correlation values ​​corresponding to each moment in the correlation sequence output by the M correlators through a comparator, and use the correlation value of the maximum modulus value corresponding to the moment as the output of the comparator at the moment, thereby outputting the optimal correlation sequence h k ;h k =[h k,1 ,h k,2 ,…,h k,N ], h k,n is h in the kth period k The relevant value corresponding to the nth moment in ;

[0018] Step B5: The bit synchronization module generates the optimal correlation sequence h k , determine the bit synchronization moment;

[0019] Step B6: The polarity judgment module determines the optimal correlation sequence h k and bit synchronization time, determine the received pre-decoded spread spectrum sequence r k The corresponding polar code And through the decoder to polar code Demodulate and obtain demodulation information

[0020] Step B7: The WFRFT parameter identification module identifies and jointly determines the correlation value corresponding to the corresponding bit synchronization moment in the correlation sequence output by the M correlators according to the bit synchronization moment, and obtains the demapping parameter Demapping parameters through parameter demapping module Demodulate and obtain demapping information

[0021] Preferably, in step B3, r b (t)=ψ k (t)*s k (t)+σ(t);

[0022] ψ k (t) is the channel impulse response in the kth time period, σ(t) is the channel noise, t is time, and '*' is the convolution operator symbol.

[0023] Preferably, in step B3, the given precoded spread spectrum sequence c′ corresponding to the jth correlator kj Ways to obtain include:

[0024] The WFRFT module at the receiving end is given a mapping parameter α′ kj Perform weighted fractional Fourier transform on the spread spectrum sequence v to obtain the given precoded spread spectrum sequence c′ kj ;in,

[0025] α′ kj is the given mapping parameter corresponding to the jth correlator, v=[v1,v2,…,v N ] T , and v n is the chip corresponding to the nth moment in the kth time period.

[0026] Preferably, in step B4, the optimal correlation sequence h is output k The implementation methods include:

[0027] The comparator compares the modulus values ​​of the M correlation values ​​corresponding to each moment in the correlation sequence output by the M correlators, obtains the correlation value corresponding to the maximum modulus value among the M correlation values ​​at each moment, and sorts the correlation values ​​corresponding to the maximum modulus value at all moments in chronological order, thereby obtaining the optimal correlation sequence h k .

[0028] Preferably, in step B5, the implementation method of determining the bit synchronization time includes:

[0029] The bit synchronization module determines the optimal correlation sequence h k The time corresponding to the maximum value of the modulus of the correlation value in is used as the bit synchronization time.

[0030] Preferably, in step B6, the polarization code is determined The implementation methods include:

[0031] The polarity decision module selects the optimal correlation sequence h k Find the correlation value corresponding to the bit synchronization moment, determine the positive and negative polarity of the correlation value, and obtain the polarization code according to the corresponding polarity

[0032] Preferably, in step B7, the demapping parameters are obtained The implementation methods include:

[0033] Step B71: The WFRFT parameter identification module identifies the correlation value corresponding to the synchronization moment in the correlation sequence output by M correlators, obtains M correlation values ​​in total, and estimates the received pre-decoding spread spectrum sequence r in the current k-th time period based on the M correlation values. k The mapping parameter difference Δα′ corresponding to different correlators j ;

[0034] Δα′ j is the mapping parameter difference corresponding to the j-th correlator;

[0035] Step B72: The mapping parameter difference Δα′ corresponding to each correlator is used. j , the given mapping parameter α′ corresponding to the correlator kj Make corrections to obtain the corrected mapping parameter α″ corresponding to the current correlator kj ;

[0036] Step B73: average all the corrected mapping parameters to obtain the demapping parameters

[0037] Preferably, in step B71, Δα′ j The method of obtaining is: by solving the function w0(Δα′ of the weighted fractional Fourier transform coefficient j ), thus obtaining Δα′ j ;in,

[0038]

[0039] is the correlation value output by the jth correlator at the synchronization time n′ in the kth time period of the receiving end; P′ is the pre-decoding spread spectrum sequence r k is the total energy of , δ is the interference caused by noise, and i is the imaginary unit.

[0040] Preferably, in step B72, α″ kj =α′ kj +Δα′j .

[0041] Preferably, the mapping rule of the encoder at the transmitting end is inverse to the mapping rule of the decoder at the receiving end, and the mapping rule of the parameter mapper at the transmitting end is inverse to the mapping rule of the parameter demapping module at the receiving end.

[0042] Principle analysis:

[0043] Based on the traditional direct sequence spread spectrum scheme, the present invention combines weighted-type fractional Fourier transform (WFRFT) and proposes an efficient information transmission method combining WFRFT and direct sequence spread spectrum, wherein the precoded spread spectrum sequence at the transmitting end is obtained by WFRFT precoding of the fixed spread spectrum sequence, and the mapping parameter of the WFRFT is driven by the mapping information, and the mapping parameter α input to the WFRFT module at the transmitting end is α. k It has the characteristics of real-time change, which is determined by the input mapping information.

[0044] The method of the present invention carries a modulated spread spectrum sequence for a data to be transmitted, and the coded information corresponding to the data to be transmitted includes multiple binary numbers, and at least two binary numbers (i.e., one modulation information and at least one mapping information) are transmitted at a time. For the precoded spread spectrum sequence, the generation of the precoded spread spectrum sequence in each time period is performed by mapping the mapping information generated by the signal source to generate the corresponding WFRFT mapping parameters, that is, different WFRFT mapping parameters are generated for different mapping information that may exist in different time periods, and multiple precoded sequences can be formed after the same spread spectrum sequence v undergoes WFRFT with different mapping parameters. The set of precoding sequences corresponding to different parameters is called a precoding sequence code group, and its size is called the scale of the precoding spreading sequence, L. The process of generating the WFRFT mapping parameters from a certain mapping information and then forming the precoding spreading sequence by applying the WFRFT of the spreading sequence v to the mapping parameters can also be viewed as the process of selecting a corresponding precoding spreading sequence from the precoding sequence code group based on the mapping information. Compared to the traditional direct sequence spread spectrum single spreading sequence scheme, which can only transmit one binary bit at a time and its encoded information consists only of modulation information, and each precoding spreading sequence is generated based on a fixed WFRFT mapping parameter, the scheme proposed in the present invention has multiple different precoding spreading sequences. Therefore, the present invention improves the system's anti-interception performance. Moreover, because the information mapping method is improved from the traditional single sequence polarity mapping to the selection and polarity mapping of multiple sequences, each precoding spreading sequence carries more information, thereby improving the system's transmission efficiency.

[0045] At the same time, the present invention improves the receiving end, specifically:

[0046] The present invention proposes to use information to control the parameters of WFRFT precoding, that is, to perform WFRFT coding under different parameters on the same spreading sequence to obtain multiple different precoded spreading sequences c′ kj , its different precoding spreading sequence c′ kj Although they do not satisfy orthogonality, the correlation between the precoding sequences generated by the two WFRFT modules under different parameters corresponding to the two WFRFT modules when the spread spectrum sequence v passes through them is certain and can be calculated. Therefore, in theory, by calculating the correlation value between the received precoding sequence and the locally generated precoding sequence, the WFRFT parameter value of the received precoding sequence can be determined by simply using the relationship between the correlation value and the two sequence parameter values. This property can reduce the complexity of the receiving system.

[0047] Therefore, the transmission method based on WFRFT parameter control of multi-sequence spread spectrum proposed in the present invention not only improves the transmission efficiency of the system, but also reduces the complexity of information detection.

[0048] Advantages of the present invention:

[0049] 1. The transmission method based on WFRFT parameter-controlled multi-sequence spread spectrum proposed in the present invention can achieve a balance between transmission capacity and receiver complexity. The number of correlator branches at the receiving end can be changed according to actual needs to improve or reduce the transmission performance of the communication system. The present invention can be applied to scenarios with high-reliability and high-confidentiality communication requirements.

[0050] 2. The present invention uses the WFRFT parameter identification module to jointly determine the demapping parameters of the received signal in the current time period based on the M correlation values ​​corresponding to the bit synchronization moment. A specific identification and judgment method for the WFRFT parameter identification module is provided, and the identification and judgment process is simple and easy to implement.

[0051] 3. Existing multi-level direct sequence spread spectrum and code domain index modulation spread spectrum technologies require M = L, that is, the number of parallel branches M equals the number of all spreading sequences generated by the transmitter. However, the technology proposed in this invention allows M ≤ L, where L is the size of the mappable parameter set in the parameter mapper, reducing the complexity of information detection.

[0052] The WFRFT and direct sequence spread spectrum joint transmission method proposed in the present invention, which is based on the WFRFT parameter-controlled multi-sequence spread spectrum transmission method, differs from the existing basic ideas of multi-ary spread spectrum (MSS) and code index modulation (CIM) in that:

[0053] 1) Compared with the direct sequence spread spectrum system with code domain index modulation, the method proposed in the present invention cannot perform high-order modulation at the transmitting end. In essence, it transmits part of the information by changing the WFRFT parameters. That is, the scheme proposed in the present invention is a new method for jointly transmitting information using WFRFT parameters and spread spectrum sequences.

[0054] 2) Compared with two existing direct sequence spread spectrum systems with similar concepts, the solution proposed in the present invention has lower complexity at the receiving end, and the number of branches required can be smaller than the code group size at the transmitting end.

[0055] 3) The present invention proposes using the spread spectrum sequence generated by WFRFT precoding with different parameters as the spread spectrum code group for multi-sequence spread spectrum at the transmitting end. This operation can reduce the complexity of the receiving end.

[0056] 4) Compared with the multi-level direct sequence spread spectrum system, the solution proposed in the present invention divides information into modulation information and mapping information, and still retains the modulation method of traditional direct sequence spread spectrum on the basis of multi-level direct sequence spread spectrum. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a schematic diagram of the principle of transmitting signals at the transmitting end of a multi-sequence spread spectrum system;

[0058] Figure 2 This is a schematic diagram of the principle of receiving signals at the transmitting and receiving ends of a multi-sequence spread spectrum system;

[0059] Figure 3 This is a comparison chart of the output results of the receiving end multi-channel parallel correlation sequence after passing through the comparator when the signal-to-noise ratio is 0dB;

[0060] Figure 4 This is a simulation diagram of the bit error rate performance of the method of the present invention under different sequence group sizes;

[0061] Figure 5 This is a bit error rate simulation diagram of the method of the present invention under different numbers of related branches at the receiving end.

[0062] In the attached figure, E b is the average bit energy, N0 is the noise power spectral density, E b / N0 is the signal-to-noise ratio per bit, and BER is the bit error rate. DETAILED DESCRIPTION

[0063] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0064] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0065] Specific implementation method 1. Figure 1 and Figure 2 This embodiment describes a transmission method based on WFRFT parameter-controlled multi-sequence spread spectrum, wherein the transmission method is implemented based on a multi-sequence spread spectrum system, and the multi-sequence spread spectrum system includes a transmitting end and a receiving end;

[0066] See also Figure 1 (1) The method for transmitting a signal at a transmitting end includes:

[0067] Step A1: The signal source performs source and / or channel coding on the data to be transmitted in the kth time period to obtain coded information, which includes modulation information p k and mapping information b k ; Modulation information p k It is a 1-bit binary number; mapping information b k is a q-bit binary number, where q is an integer;

[0068] Step A2: Modulate the information p through the encoder k Perform polarity coding to obtain modulation information p k The corresponding polar code d k At the same time, the mapping information b is mapped through the parameter mapper k Perform mapping and generate mapping parameter α k ; The WFRFT module at the transmitting end is based on the mapping parameter α k Perform weighted fractional Fourier transform on the spread spectrum sequence v to obtain the precoded spread spectrum sequence c k ; where v=[v1,v2,…,v N ] T ;v n is the chip corresponding to the nth moment in the kth time period in v; n = 1, 2, 3...N, k is a positive integer;

[0069] Step A3: Polar code d k With the precoded spreading sequence c kMultiply them to get the modulated spread spectrum sequence g k ;

[0070] Step A4: Modulate the spread spectrum sequence g k After up-conversion, the obtained RF signal s k (t) send to the channel;

[0071] See also Figure 2 (2) The method for receiving a signal at a receiving end includes:

[0072] Step B1: Receive radio frequency signal s k (t) RF signal r after propagation through the channel b (t), and the RF signal r is filtered by a broadband filter b (t) After filtering, the filtered signal r is obtained c (t);

[0073] Step B2: filter the signal r c (t) down-converts to obtain the pre-decoded spread spectrum sequence r k ;

[0074] Step B3: Pre-decode the spread spectrum sequence r k The signals are inputted into M correlators in parallel; at the same time, M given precoded spread spectrum sequences are obtained according to M given mapping parameters, and the M given precoded spread spectrum sequences are respectively sent to M correlators;

[0075] Each correlator will pre-decode the spreading sequence r k The given precoded spread spectrum sequence c′ corresponding to the correlator kj Perform relevant operations and get Among them, c′ kj is the given precoded spreading sequence corresponding to the jth correlator, is the correlated sequence output by the jth correlator; is the jth correlator in the kth time period The correlation value corresponding to the nth moment in ; j = 1, 2, 3 ... M, n = 1, 2, 3 ... N;

[0076] Step B4: Compare the maximum modulus value of the M correlation values ​​corresponding to each moment in the correlation sequence output by the M correlators through a comparator, and use the correlation value of the maximum modulus value corresponding to the moment as the output of the comparator at the moment, thereby outputting the optimal correlation sequence h k ;h k =[h k,1 ,h k,2 ,…,h k,N ], h k,n is h in the kth periodk The relevant value corresponding to the nth moment in ;

[0077] Step B5: The bit synchronization module generates the optimal correlation sequence h k , determine the bit synchronization moment;

[0078] Step B6: The polarity judgment module determines the optimal correlation sequence h k and bit synchronization time, determine the received pre-decoded spread spectrum sequence r k The corresponding polar code And through the decoder to polar code Demodulate and obtain demodulation information

[0079] Step B7: The WFRFT parameter identification module identifies and jointly determines the correlation value corresponding to the corresponding bit synchronization moment in the correlation sequence output by the M correlators according to the bit synchronization moment, and obtains the demapping parameter Demapping parameters through parameter demapping module Demodulate and obtain demapping information

[0080] The coded information at the transmitter is divided into modulation information and mapping information. The coded information refers to the data obtained after the 0 and 1 bit data output by the source is coded and channel coded. For modulation information, each spread spectrum symbol transmits 1 bit of modulation information; for mapping information, each symbol transmits 1 bit of modulation information. Mapping information. Where L is the size of the mappable parameter set in the parameter mapper, The symbol represents rounding down. Spread spectrum symbol: In a spread spectrum signal, a spreading sequence constitutes a spread spectrum symbol. Symbol period: The duration of a spread spectrum symbol. Chip period: The duration of each chip of a spread spectrum symbol.

[0081] In specific applications, there is no constraint on the encoder input and output coding rules at the transmitter, but a one-to-one mapping relationship is used. The polarization code d k ∈{-1,1}, if p k =1, then d k =-1, otherwise if p k =0, then d k = 1. Another rule is that if p k =1, then d k =1, otherwise if p k =0, then d k= -1. Both rules should be within the protection range. For the parameter mapper at the transmitter, the mapping relationship is related to the mapper parameter set elements and their size. The main process includes the sampling of the parameter set and the establishment of the mapping rule, including but not limited to the following examples. Taking the parameter mapper L = 8 as an example, the WFRFT module input parameter value range is α k =[-1,1), then the parameter set elements of the parameter mapper can be uniformly sampled within the value range, that is, α k ∈{-1,-0.75,-0.5,-0.25,0,0.25,0.5,0.75}. In this case, the number of bits in the mapping information is 3, and the decimal value of the mapping information corresponds to the order of the parameter sampling values, that is, the mapping rules are 000→-1, 001→-0.75, 010→-0.5, 011→-0.25, 100→0, 101→0.25, 110→0.5, and 111→0.75.

[0082] The present invention does not limit the type of spread spectrum sequence v. The generated spread spectrum sequence v enters the WFRFT module for N-point weighted fractional Fourier transform, and the transformation parameter is the parameter α output by the parameter mapper. k , that is, the transformation parameter α=α k The matrix expression of weighted fractional Fourier transform is as follows:

[0083] c k =w0(α k )v+w1(α k )Fv+w2(α k )Γv+w3(α k )ΓFv (1);

[0084] In formula (1), w l (α k ) is the transformation parameter α=α k The weighted fractional Fourier transform function, l = 0, 1, 2, 3, its w l (α) The expression definition is shown in formula (2):

[0085]

[0086] The matrix F is the matrix form of discrete Fourier transform, and the matrix Γ is the permutation matrix, which is defined as:

[0087]

[0088] c k =[c k,1 ,c k,2 ,…,c k,N ];c k,n c kThe chip corresponding to the nth moment in the kth time period;

[0089] g k =d k c k =[d k c k,1 ,d k c k,2 ,…,d k c k,N ]=[g k,1 ,g k,2 ,…,g k,N ] (4);

[0090] When applied, since the receiving end does not have the same bit synchronization signal as the transmitting end, it is impossible to directly confirm the current pre-decoding spread spectrum sequence r k =[r k,1 ,r k,2 ,…,r k,N ] is a complete spread spectrum sequence or a concatenation of two spread spectrum sequences. Therefore, it is necessary to determine the bit synchronization time; r k,n For r k The code chip corresponding to the nth moment in the kth time period.

[0091] Furthermore, in step B3, r b (t)=ψ k (t)*s k (t)+σ(t);ψ k (t) is the channel impulse response in the kth time period, σ(t) is the channel noise, t is time, and '*' is the convolution operator symbol.

[0092] In step B3, the given precoded spread spectrum sequence c′ corresponding to the jth correlator kj Ways to obtain include:

[0093] The WFRFT module at the transmitter is given a mapping parameter α′ kj Perform weighted fractional Fourier transform on the spread spectrum sequence v to obtain the given precoded spread spectrum sequence c′ kj ; Among them, α′ kj is the given mapping parameter corresponding to the jth correlator, v=[v1,v2,…,v N ] T , and v n is the code chip corresponding to the nth moment in the kth time period, n = 1, 2, 3...N, N is the sequence length.

[0094] Furthermore, in step B4, the optimal correlation sequence h is output k The implementation methods include:

[0095] The comparator compares the modulus values ​​of the M correlation values ​​corresponding to each moment in the correlation sequence output by the M correlators, obtains the correlation value corresponding to the maximum modulus value among the M correlation values ​​at each moment, and sorts the correlation values ​​corresponding to the maximum modulus value at all moments in chronological order, thereby obtaining the optimal correlation sequence h k .

[0096] For further information, see Figure 2 In step B5, the implementation method of determining the bit synchronization time includes:

[0097] The bit synchronization module calculates the optimal correlation sequence h in the kth time period at the receiving end. k The time corresponding to the maximum value of the modulus of the correlation value in is used as the bit synchronization time.

[0098] For further information, see Figure 2 In step B6, determine the polarization code The implementation methods include: k Find the correlation value corresponding to the bit synchronization moment, determine the positive and negative polarity of the correlation value, and obtain the polarization code according to the corresponding polarity

[0099] The polarity judgment module determines the pre-decoding spread spectrum sequence r received in the kth time period by judging the positive or negative correlation value corresponding to the bit synchronization moment. k The polarity of the polar code carried by it, when applied, if the correlation value at the position corresponding to the bit synchronization moment is negative, then the judgment module outputs If the correlation value at the position corresponding to the bit synchronization moment is positive, the output of the decision module is

[0100] For further information, see Figure 2 In step B7, the demapping parameters are obtained The implementation methods include:

[0101] Step B71: The WFRFT parameter identification module identifies the correlation value corresponding to the synchronization moment in the correlation sequence output by M correlators, obtains M correlation values ​​in total, and estimates the received pre-decoding spread spectrum sequence r in the current k-th time period based on the M correlation values. k The mapping parameter difference Δα′ corresponding to different correlators j ; where Δα′ j The method of obtaining is: by solving the function w0(Δα′ of the weighted fractional Fourier transform coefficient j ), thus obtaining Δα′ j ;

[0102]

[0103] Δα′ j is the mapping parameter difference corresponding to the j-th correlator; is the correlation value output by the jth correlator at the synchronization time n′ in the kth time period of the receiving end; α′ kj is the given mapping parameter corresponding to the jth correlator, P′ is the pre-decoding spread spectrum sequence r k The total energy of δ is the interference caused by noise; α′ kj is the given mapping parameter corresponding to the j-th correlator, i is the imaginary unit;

[0104] Step B72: The mapping parameter difference Δα′ corresponding to each correlator is used. j , the given mapping parameter α′ corresponding to the correlator kj Make corrections to obtain the corrected mapping parameter α″ corresponding to the current correlator kj ; Specifically, α″ kj =α′ kj +Δα′ j ;

[0105] Step B73: average all the corrected mapping parameters to obtain the demapping parameters

[0106] In this preferred embodiment, related existing technologies, such as multi-level direct sequence spread spectrum systems and code domain index modulation spread spectrum systems, use mutually orthogonal spreading code groups at the transmitter end, meaning the correlation between different spreading codes is zero. While this improves system reliability, the receiver must traverse all codewords in all spreading code groups. This means the receiver must establish L parallel branches (L is the size of the pre-coded spreading sequence group at the transmitter end) to perform correlation operations, significantly increasing system complexity.

[0107] The present invention proposes to use mapping information to control the parameters of WFRFT precoding. Although the different spreading codes of the precoding spread spectrum sequences generated by different mapping information do not satisfy orthogonality, the correlation between the precoding sequences generated by the spread spectrum sequence v after passing through the two WFRFT modules under the different parameters corresponding to the two WFRFT modules is certain and can be calculated. Therefore, in theory, the correlation value between the received precoding sequence and the locally generated precoding sequence can be calculated. The WFRFT parameter value of the received precoding sequence can be determined by simply using the relationship between the correlation value and the two sequence parameter values. This property can be used to reduce the complexity of the receiving system.

[0108] Furthermore, the mapping rule of the encoder at the transmitting end is inverse to the mapping rule of the decoder at the receiving end, and the mapping rule of the parameter mapper at the transmitting end is inverse to the mapping rule of the parameter demapping module at the receiving end.

[0109] As an example: the mapping rules of the demapping module correspond to the mapping rules of the transmitter. For example, At this point, the number of bits in the mapping information is 3, and the parameter sampling values ​​correspond to the decimal values ​​of the mapping information in sequence. That is, the demapping rules are -1→000, -0.75→001, -0.5→010, -0.25→011, 0→100, 0.25→101, 0.5→110, and 0.75→111. At this point, the mapping information detection is complete.

[0110] Verification test:

[0111] Figure 3 is the output result of the receiving end multi-channel parallel correlation sequence after passing through the comparator in the AWGN channel with a signal-to-noise ratio of 0dB. Figure 3 The position where the peak value (normalized) of the correlation value appears is the bit synchronization position. The simulation results show that the method proposed in the present invention can effectively find the synchronization moment.

[0112] Figure 4 The proposed scheme compares the system bit error rate performance with the theoretical bit error rate performance of PSK modulation when the code group size at the transmitter is 2, 4, and 8, that is, the mapping information is 1 bit, 2 bits, and 3 bits, respectively, and the number of parallel branches at the receiver is the same as the code group size. The bit error rate performance of the curve corresponding to L = M = 2 is between the theoretical values ​​of BPSK and 8PSK. The bit error rate performance of the curve corresponding to L = M = 4 is higher than that of 8PSK at high signal-to-noise ratios, and the bit error rate performance of the curve corresponding to L = M = 8 is higher than that of 16PSK at high signal-to-noise ratios. Further analysis of the figure shows that when the number of branches M is the same as the code group size L, the performance of the proposed system is close to the theoretical transmission performance of a PSK system with the same number of bits transmitted per symbol under the same signal-to-noise ratio per bit, which is of research value.

[0113] Figure 5 The system bit error rate performance of the method of the present invention is shown when the code group size at the transmitting end is 4 and the number of parallel branches at the receiving end is 2 and 4, respectively. When L = 4 and M = 2, that is, when the number of relevant branches at the receiving end is smaller than the scale of the pre-coded spread spectrum sequence at the transmitting end, the bit error rate performance decreases compared to the case of L = M = 4, but the bit error rate performance gradually improves as the signal-to-noise ratio per bit increases. It can be concluded that the detection algorithm proposed in the present invention can perform information detection and demodulation when the number of relevant branches M at the receiving end is smaller than the scale L of the pre-coded spread spectrum sequence at the transmitting end, proving the effectiveness of the algorithm of the present invention.

[0114] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be employed in conjunction with other described embodiments.

Claims

1. A transmission method based on WFRFT parameter control of multi-sequence spread spectrum, wherein the transmission method is implemented based on a multi-sequence spread spectrum system, and the multi-sequence spread spectrum system includes a transmitting end and a receiving end; characterized in that: (1) The method for transmitting a signal at the transmitting end includes: Step A1: The signal source performs source and / or channel coding on the data to be transmitted in the kth time period to obtain coded information, which includes modulation information p k and mapping information b k ; Modulation information p k It is a 1-bit binary number; mapping information b k is a q-bit binary number, where q is an integer; Step A2: Modulate the information p through the encoder k Perform polarity coding to obtain modulation information p k The corresponding polar code d k At the same time, the mapping information b is mapped through the parameter mapper k Perform mapping and generate mapping parameter α k ; The WFRFT module at the transmitting end is based on the mapping parameter α k Perform weighted fractional Fourier transform on the spread spectrum sequence v to obtain the precoded spread spectrum sequence c k ; where v=[v1,v2,…,v N ] T ;v n is the chip corresponding to the nth moment in the kth time period in v; n = 1, 2, 3...N, k is a positive integer; Step A3: Polar code d k With the precoded spreading sequence c k Multiply them to get the modulated spread spectrum sequence g k ; Step A4: Modulate the spread spectrum sequence g k After up-conversion, the obtained RF signal s k (t) send to the channel; (2) The method for receiving a signal at a receiving end includes: Step B1: Receive radio frequency signal s k (t) RF signal r after propagation through the channel b (t), and the RF signal r is filtered by a broadband filter b (t) After filtering, the filtered signal r is obtained c (t); Step B2: filter the signal r c (t) down-converts to obtain the pre-decoded spread spectrum sequence r k ; Step B3: Pre-decode the spread spectrum sequence r k The signals are inputted into M correlators in parallel; at the same time, M given precoded spread spectrum sequences are obtained according to M given mapping parameters, and the M given precoded spread spectrum sequences are respectively sent to M correlators; Each correlator will pre-decode the spreading sequence r k The given precoded spread spectrum sequence c′ corresponding to the correlator kj Perform relevant operations and get Among them, c′ kj is the given precoded spreading sequence corresponding to the jth correlator, is the correlated sequence output by the jth correlator; is the jth correlator in the kth time period The correlation value corresponding to the nth moment in ; j = 1, 2, 3 ... M, n = 1, 2, 3 ... N; Step B4: Compare the maximum modulus value of the M correlation values ​​corresponding to each moment in the correlation sequence output by the M correlators through a comparator, and use the correlation value of the maximum modulus value corresponding to the moment as the output of the comparator at the moment, thereby outputting the optimal correlation sequence h k ;h k =[h k,1 ,h k,2 ,…,h k,N ], h k,n is h in the kth period k The relevant value corresponding to the nth moment in ; Step B5: The bit synchronization module generates the optimal correlation sequence h k , determine the bit synchronization moment; Step B6: The polarity judgment module determines the optimal correlation sequence h k and bit synchronization time, determine the received pre-decoded spread spectrum sequence r k The corresponding polar code And through the decoder to polar code Demodulate and obtain demodulation information Step B7: The WFRFT parameter identification module identifies and jointly determines the correlation value corresponding to the corresponding bit synchronization moment in the correlation sequence output by the M correlators according to the bit synchronization moment, and obtains the demapping parameter Demapping parameters through parameter demapping module Demodulate and obtain demapping information 2. The transmission method based on WFRFT parameter controlled multi-sequence spread spectrum according to claim 1, characterized in that: In step B3, r b (t)=ψ k (t)*s k (t)+σ(t); ψ k (t) is the channel impulse response in the kth time period, σ(t) is the channel noise, t is time, and '*' is the convolution operator symbol.

3. The transmission method based on WFRFT parameter-controlled multi-sequence spread spectrum according to claim 1, characterized in that: In step B3, the given precoded spread spectrum sequence c′ corresponding to the jth correlator kj Ways to obtain include: The WFRFT module at the receiving end is given a mapping parameter α′ kj Perform weighted fractional Fourier transform on the spread spectrum sequence v to obtain the given precoded spread spectrum sequence c′ kj ;in, α′ kj is the given mapping parameter corresponding to the jth correlator, v=[v1,v2,…,v N ] T , and v n is the chip corresponding to the nth moment in the kth time period.

4. The transmission method based on WFRFT parameter controlled multi-sequence spread spectrum according to claim 1, characterized in that: In step B4, the optimal correlation sequence h is output k The implementation methods include: The comparator compares the modulus values ​​of the M correlation values ​​corresponding to each moment in the correlation sequence output by the M correlators, obtains the correlation value corresponding to the maximum modulus value among the M correlation values ​​at each moment, and sorts the correlation values ​​corresponding to the maximum modulus value at all moments in chronological order, thereby obtaining the optimal correlation sequence h k .

5. The transmission method based on WFRFT parameter controlled multi-sequence spread spectrum according to claim 1, characterized in that: In step B5, the implementation method of determining the bit synchronization time includes: The bit synchronization module determines the optimal correlation sequence h k The time corresponding to the maximum value of the modulus of the correlation value in is used as the bit synchronization time.

6. The transmission method based on WFRFT parameter-controlled multi-sequence spread spectrum according to claim 1, characterized in that: In step B6, determine the polarization code The implementation methods include: The polarity decision module selects the optimal correlation sequence h k Find the correlation value corresponding to the bit synchronization moment, determine the positive and negative polarity of the correlation value, and obtain the polarization code according to the corresponding polarity 7. The transmission method based on WFRFT parameter controlled multi-sequence spread spectrum according to claim 1, characterized in that: In step B7, the demapping parameters are obtained The implementation methods include: Step B71: The WFRFT parameter identification module identifies the correlation value corresponding to the synchronization moment in the correlation sequence output by M correlators, obtains M correlation values ​​in total, and estimates the received pre-decoding spread spectrum sequence r in the current k-th time period based on the M correlation values. k The mapping parameter difference Δα′ corresponding to different correlators j ; Δα′ j is the mapping parameter difference corresponding to the j-th correlator; Step B72: The mapping parameter difference Δα′ corresponding to each correlator is used. j , the given mapping parameter α′ corresponding to the correlator kj Make corrections to obtain the corrected mapping parameter α″ corresponding to the current correlator kj ; Step B73: average all the corrected mapping parameters to obtain the demapping parameters 8. The transmission method based on WFRFT parameter-controlled multi-sequence spread spectrum according to claim 7, characterized in that: In step B71, Δα′ j The method of obtaining is: by solving the function w0(Δα′ of the weighted fractional Fourier transform coefficient j ), thus obtaining Δα′ j ; in, is the correlation value output by the jth correlator at the synchronization time n′ in the kth time period at the receiving end; P′ is the pre-decoding spreading sequence r k is the total energy of , δ is the interference caused by noise, and i is the imaginary unit.

9. The transmission method based on WFRFT parameter-controlled multi-sequence spread spectrum according to claim 7, characterized in that: In step B72, α″ kj = α′ kj + Δα′ j .

10. The transmission method based on WFRFT parameter controlled multi-sequence spread spectrum according to claim 1, characterized in that: The mapping rule of the encoder at the transmitting end is inverse to the mapping rule of the decoder at the receiving end, and the mapping rule of the parameter mapper at the transmitting end is inverse to the mapping rule of the parameter demapping module at the receiving end.

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