MSK Spread Spectrum System Transceiver Processing Method and System

Abstract

This invention discloses a method and system for processing transmit and receive data in an MSK spread spectrum system. The spread spectrum sequence d is obtained through a spread spectrum module. n The modulation sequence b is obtained through the BPSK modulation module. n The MSK modulated signal I-channel SigI is obtained through the MSK modulation module. n and Q road SigQ n The MSK signal demodulation module is used to obtain the demodulated D signal. k The despreading module is used to obtain the despreading soft information Ds. m The method and system described above further simplify the MSK spread spectrum system by obtaining the received information bits through the BPSK demodulation module. While ensuring the performance of the MSK spread spectrum system, the implementation complexity of the MSK spread spectrum system transceiver end is reduced by the phase interleaving change law of the IQ path.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication waveform transmission technology, specifically relating to an MSK spread spectrum system transceiver processing method and system. Background Technology

[0002] Communication systems based on MSK (Minimum Frequency Shift Keying) spread spectrum modulation are widely used in electronic warfare, radar monitoring, data links, and other fields. MSK spread spectrum modulation signals have advantages such as constant envelope, low signal-to-noise ratio, and strong anti-interference capability, and are widely used in various complex communication systems such as burst communication and radar signal detection. Currently, MSK spread spectrum communication systems generally suffer from high despreading and demodulation complexity.

[0003] For example, Chinese invention patent application number CN202010779475.0 discloses a simplified noncoherent despreading and demodulation method for MSK spread spectrum systems. By applying it to a noncoherent receiver of an MSK spread spectrum system, a complex despreading sequence is constructed based on a parallel structure, and correlation peak search is performed.

[0004] This existing technology simplifies the traditional MSK spread spectrum system, but it does not solve the problem of the transmission method of the MSK spread spectrum system. At the same time, its despreading and soft information decision selection are relatively complex.

[0005] For example, Chinese invention patent application CN201510441988.X discloses a fully digital method for receiving direct-sequence MSK signals, characterized by including...

[0006] The direct-sequence MSK signal is constructed into an approximate direct-sequence BPSK signal.

[0007] A two-dimensional joint acquisition algorithm based on pseudocode phase and carrier Doppler frequency offset, using Doppler compensation-FFT, is employed to acquire the constructed approximate direct-sequence BPSK signal.

[0008] Track the pseudocode phase and carrier phase.

[0009] The transmitted data is recovered from the synchronized signal through despreading, demodulation, and detection.

[0010] The approximate direct-sequence BPSK signal is constructed by multiplying the direct-sequence MSK signal (after intermediate frequency sampling, digital down-conversion, and low-pass filtering) with a waveform function, followed by decimation and alternating sampling.

[0011] The two-dimensional joint acquisition algorithm for pseudocode phase and carrier Doppler frequency offset based on Doppler compensation-FFT includes:

[0012] FFT-based Doppler filtering;

[0013] Doppler compensation based on phase compensation factor and cyclic shift local pseudocode;

[0014] Pseudocode phase parallel acquisition based on segmented FFT.

[0015] The existing technology cannot solve the technical problems of MSK spread spectrum system transmission method and simplified implementation of despreading and noncoherent demodulation.

[0016] Based on the aforementioned technical problems in the existing technology, this invention proposes an MSK spread spectrum system transceiver processing method and system. Summary of the Invention

[0017] The purpose of this invention is to address the shortcomings of existing technologies by providing a method and system for transmitting and receiving data in an MSK spread spectrum system.

[0018] The present invention adopts the following technical solution:

[0019] On the one hand, a transceiver processing method for an MSK spread spectrum system is provided, including:

[0020] Step 1, send information bit a k Perform direct sequence spread spectrum to obtain the spread spectrum sequence d. n , n=1,2,...,N*L, where L is the spreading factor, k=0,1,...,N-1, and N is the number of symbols transmitted;

[0021] Step 2: Perform binary phase shift keying (BPSK) modulation to obtain the modulation sequence b. n , where b n =2*d n -1;

[0022] Step 3, based on the modulation sequence b n The MSK modulated signal I channel SigI was obtained respectively. n and Q road SigQ n Where n = 1, 2, ..., N*L+1;

[0023] Step 4: The MSK modulated signal is modulated by a carrier, passes through the transmitting end RF path, and then reaches the receiving end via the wireless channel. After carrier demodulation in the receiving end RF path, the receiving end baseband signal is obtained. The demodulated D of the MSK signal is calculated. k :

[0024] D k =-1,k=1……(1);

[0025]

[0026]

[0027] In the above formula (2), k starts at 3 and takes values ​​at intervals of 2;

[0028] In the above formula (3), k starts at 2 and takes values ​​at intervals of 2;

[0029] Step 5, based on the demodulated MSK signal D k Despreading is performed to obtain the despread soft information Ds. m ;

[0030] Step 6, based on soft information Ds m Received information bits

[0031] Further, step 1 includes:

[0032] Step 1.1, for a k Each bit is repeated L times to obtain the repeating sequence a. n And generate a pseudo-random sequence m of length L. l l = 1, 2, ..., L, and simultaneously obtain the BPSK (Binary Phase Shift Keying) modulation sequence M of the pseudo-random sequence. l,BPSK M l,BPSK =2*m l -1, used for despreading, and for m l The sequence is copied N times to obtain the copied sequence m. n ;

[0033] Step 1.2, for a n Perform a bit XOR operation on the sequence to obtain the spreading sequence d. n =xor(a n ,m n ).

[0034] Furthermore, step 3 includes:

[0035] Step 3.1, calculate the accumulated phase, where For the initial phase, Cumulative phase value at each moment:

[0036]

[0037] Step 3.2, calculate the I-channel and Q-channel modulation signals.

[0038] SigI n =cos(θ) n )……(5);

[0039] SigQ n =sin(θ)n )……(6).

[0040] Furthermore, step 5 includes:

[0041] Step 5.1, delete D k The first invalid point yields valid demodulated data D. t ,t=1,2,...N*L;

[0042] Step 5.2, D t The data is divided into blocks, with each block consisting of L consecutive data points, resulting in a total of N blocks of data D with a length of L. l,m Where, l = 1, 2, ... L, m = 1, 2, ..., N;

[0043] Step 5.3, compare the data of each block with the spreading sequence M l,BPSK By performing relevant summation, the despread soft information Ds is obtained. m Where m = 1, 2, ..., N,

[0044]

[0045] Furthermore, in step 6, the soft information Ds m Make a hard judgment.

[0046]

[0047] Received information bits

[0048] On the other hand, an MSK spread spectrum system transceiver processing system is provided, including:

[0049] The spread spectrum module transmits information bits a. k Perform direct sequence spread spectrum to obtain the spread spectrum sequence d. n ;

[0050] The BPSK modulation module performs binary phase shift keying (BPSK) modulation to obtain the modulation sequence b. n ;

[0051] MSK modulation module, based on modulation sequence b n The MSK modulated signal I-channel SigI is obtained. n and Q road SigQ n ;

[0052] The MSK demodulation module is used to calculate the demodulated D of the MSK signal. k ;

[0053] The despreading module, based on the demodulated MSK signal D k Despreading is performed to obtain the despread soft information Ds.m ;

[0054] The BPSK demodulation module, based on the soft information Ds m Received information bits

[0055] The beneficial effects of this invention are:

[0056] The MSK spread spectrum system transceiver processing method and system described in this invention further simplify the MSK spread spectrum system. While ensuring the performance of the MSK spread spectrum system, it reduces the implementation complexity of the MSK spread spectrum system transceiver end by using the phase interleaving change law of the IQ path. Attached Figure Description

[0057] Figure 1 This is a graph showing the bit error rate performance of the MSK system in an embodiment of the present invention.

[0058] Figure 2 This is a two-dimensional fuzzy function graph of the MSK system in an embodiment of the present invention. Detailed Implementation

[0059] To better understand the above-mentioned objectives, features and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0060] Example

[0061] A transceiver processing method for an MSK spread spectrum system includes:

[0062] Step 1, send information bit a k Perform direct sequence spread spectrum to obtain the spread spectrum sequence d. n , n=1,2,...,N*L, where L is the spreading factor, k=0,1,...,N-1, and N is the number of symbols transmitted;

[0063] Step 1.1, for a k Repeat each bit L times to get a n And generate a pseudo-random sequence m of length L. l l = 1, 2, ..., L, and simultaneously obtain the BPSK (Binary Phase Shift Keying) modulation sequence M of the pseudo-random sequence. l,BPSK Used for despreading, M l,BPSK =2*m l -1, and for m l Repeat N times to obtain sequence m n ;

[0064] Step 1.2: Perform XOR calculation on the sequence bits to obtain the spreading sequence d. n =xor(a n ,m n );

[0065] Step 2: Perform binary phase shift keying (BPSK) modulation to obtain the modulation sequence b. n , where b n =2*d n -1;

[0066] Step 3, based on the modulation sequence b n The MSK modulated signal I channel SigI was obtained respectively. n and Q road SigQ n Where n = 1, 2, ..., N*L+1;

[0067] Step 3.1, calculate the accumulated phase, where For the initial phase, Cumulative phase value at each moment:

[0068]

[0069] Step 3.2, calculate the I-channel and Q-channel modulation signals.

[0070] SigI n =cos(θ) n );

[0071] SigQ n =sin(θ) n );

[0072] Step 4: After the wireless signal passes through the channel and then through the radio frequency path, the receiving baseband signal is obtained. The demodulated D of the MSK signal is calculated. k :

[0073] D k =-1, k=1;

[0074]

[0075]

[0076] In the above formula (2), k starts at 3 and takes values ​​at intervals of 2;

[0077] In the above formula (3), k starts at 2 and takes values ​​at intervals of 2;

[0078] Step 5, based on the demodulated MSK signal D k Despreading is performed to obtain the despread soft information Ds. m ;

[0079] Step 5.1, delete D k The first invalid point yields valid demodulated data D. t ,t=1,2,...N*L;

[0080] Step 5.2, D t The data is divided into blocks, with each block consisting of L consecutive data points, resulting in a total of N blocks of data D with a length of L. l,m Where, l = 1, 2, ... L, m = 1, 2, ..., N;

[0081] Step 5.3, compare the data of each block with the spreading sequence M l,BPSK By performing relevant summation, the despread soft information Ds is obtained. m Where m = 1, 2, ..., N,

[0082]

[0083] Step 6, based on soft information Ds m The received information bits are either hard-determined or sent to a decoder for decoding to obtain the received information bits.

[0084] If a hard decision method is adopted:

[0085]

[0086] Received information bits

[0087] The MSK spread spectrum system transceiver processing system includes:

[0088] The spread spectrum module transmits information bits a. k Perform direct sequence spread spectrum to obtain the spread spectrum sequence d. n ;

[0089] The BPSK modulation module performs binary phase shift keying (BPSK) modulation to obtain the modulation sequence b. n ;

[0090] MSK modulation module, based on modulation sequence b n The MSK modulated signal I-channel SigI is obtained. n and Q road SigQ n ;

[0091] The MSK demodulation module is used to calculate the demodulated D of the MSK signal. k ;

[0092] The despreading module, based on the demodulated MSK signal D k Despreading is performed to obtain the despread soft information Ds. m ;

[0093] The BPSK demodulation module, based on the soft information Ds m Received information bits

[0094] To verify the superiority of the method described in this embodiment, such as Figure 1-2 As shown, a simulation platform was built, assuming that the number of data symbols N to be transmitted is 100, the spreading factor L is 127, the symbol rate is 40KHz, the corresponding chip rate Fc is 5080KHz, the corresponding chip time Tc=1 / Fc, the simulation channel is a white Gaussian noise (AWGN) channel, and the number of simulations is 20000.

[0095] From the simulation performance, the MSK spread spectrum system transceiver processing method described in this embodiment has a bit error rate performance that approximates the theoretical curve. The theory and simulation verify the rationality of the method described in this embodiment.

[0096] Further simulation of the signal using two-dimensional ambiguity functions of velocity and distance shows that when SNR = -5dB, the peak value of the ambiguity function is very obvious, indicating that the signal of this invention has a strong ability to resist Doppler and time delay changes, and can be applied to fields such as radar signal detection.

[0097] This invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims.

Claims

1. A method for processing a MSK spread spectrum system transceiver, characterized in that, include: Step 1, spreading the transmitted information bits by direct sequence spreading to obtain a spread sequence , wherein, is a spreading factor, , is the number of transmitted symbols;​ Step 2: Perform binary phase shift keying (BPSK) modulation to obtain the modulation sequence. ,in, ; Step 3, based on the modulation sequence MSK modulated signal I channels were obtained respectively. and Q Road : Step 3.1, calculate the accumulated phase, where For the initial phase, Cumulative phase value at each moment: ， （4）； Step 3.2, calculate the I-channel and Q-channel modulation signals. （5）； （6）； in, ; Step 4: The MSK modulated signal is modulated by a carrier, passes through the transmitting end RF path, and then reaches the receiving end via the wireless channel. After carrier demodulation in the receiving end RF path, the receiving end baseband signal is obtained. , The demodulated MSK signal was calculated. : （1）； （2）； （3）； In the above formula (2), Starting with 3, and taking values ​​at intervals of 2; In the above formula (3), Starting with 2, and taking values ​​at intervals of 2; Step 5, based on the demodulated MSK signal Despreading is performed to obtain despread soft information. ; Step 6, based on the despreading software information Received information bits .

2. The MSK spread spectrum system transceiver processing method according to claim 1, characterized in that, Step 1 includes: Step 1.1, for Each bit is repeated. This yields a repeating sequence. ; and generate a length of pseudo-random sequence , Simultaneously, the BPSK modulation sequence of the pseudo-random sequence is obtained. , Used for despreading and for Copy This yields the copied sequence. ; Step 1.2, for Perform a bit XOR operation on the sequence to obtain the spreading sequence. .

3. The MSK spread spectrum system transceiver processing method according to claim 1, characterized in that, Step 5 includes: Step 5.1, Delete The first invalid point yields valid demodulated data. ; Step 5.2, will Divide into blocks, each consecutive Each data point is grouped into a block, resulting in a total of [number] data points. The block length is Data ,in, ; Step 5.3: Compare the data and spreading sequence for each block. By performing relevant summation, the despread soft information is obtained. ,in, , （7）。 4. The MSK spread spectrum system transceiver processing method according to claim 1, characterized in that, In step 6, the soft information Make a hard judgment. ， （8）； Received information bits .

5. An MSK spread spectrum system transceiver processing system, used to execute the MSK spread spectrum system transceiver processing method according to claim 1, characterized in that, include: The spread spectrum module transmits information bits. Perform sequence spreading to obtain the spreading sequence. ; The BPSK modulation module performs binary phase shift keying (BPSK) modulation to obtain the modulation sequence. ; MSK modulation module, based on modulation sequence The MSK modulated signal I channel is obtained. and Q Road ; The MSK demodulation module is used to calculate and demodulate the MSK signal. ; The despreading module, based on the demodulated MSK signal... Despreading is performed to obtain despread soft information. ; The BPSK demodulation module, based on soft information Received information bits .

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