CN117955601A - Symbol-level full-band mapping space-to-ground anti-interference method based on Turbo coding and decoding - Google Patents

Abstract

The invention discloses a symbol-level full-band mapping space-to-ground anti-interference method based on Turbo coding and decoding, and belongs to the field of anti-interference digital signal processing. The implementation method of the invention comprises the following steps: and performing Turbo repetition coding on the original information with the length of K, mapping the code word to a QAM symbol by adopting high-order QAM modulation, uniformly mapping the homologous QAM symbol to each hop by symbol-level full-band mapping, and transmitting a frequency hopping signal to a partial band interference channel or a time domain pulse interference channel. And performing interference detection at a receiving end, performing zero-setting processing on the interfered position, and deleting interference in a received signal. And (3) carrying out de-hopping on the signal after zero setting, merging the homologous QAM symbols of each hop after de-interleaving, and carrying out de-mapping and decoding. The redundancy generated by the same information bit in the sample received by the receiving end is required to have an undisturbed part, and in the iterative decoding process, the undisturbed bit can assist the disturbed bit to converge to a correct value by utilizing the constraint relation between the encoded code words, so that the error rate of the decoding result output by the decoder is reduced, and the anti-interference performance is improved.

Description

Symbol-level full-band mapping space-to-ground anti-interference method based on Turbo coding and decoding

Technical Field

The invention discloses a symbol-level full-band mapping space-to-ground anti-interference method based on Turbo coding, in particular relates to an anti-interference method through channel coding and symbol-level mapping, and belongs to the field of anti-interference digital signal processing.

Background

In an interference-free communication scenario, communication systems face a complex balance between interference-free capability and communication rate. Traditional frequency hopping spread spectrum (frequency hopping spread) and direct sequence spread spectrum (direct spread) technologies encounter a series of challenges in the air-ground cooperative combat scenario, especially under the requirement of realizing real-time intercommunication of the combat units. Frequency hopping spread spectrum communication systems combat interference and eavesdropping by frequently changing the carrier frequency or pattern during transmission, however, conventional frequency hopping systems exhibit relatively low information transmission rates due to limited frequency variation and limited length of the frequency hopping sequence.

Direct sequence spread spectrum spreads the spectrum by multiplying the signal with a high speed pseudo-random code, which results in a relatively large bandwidth per symbol, resulting in a reduction in the transmission rate. In an air-ground cooperative combat scene, the combat units need to communicate in real time and efficiently, so that the traditional anti-interference technology often has difficulty in meeting the high requirement on the communication rate.

In view of the foregoing, current anti-interference communication technologies face a challenge in that it is difficult to maintain a sufficient communication rate while pursuing anti-interference capability. Therefore, new communication technologies or improvements are urgently needed to realize efficient, high-speed, interference-free communication systems in air-ground cooperative combat scenarios.

Disclosure of Invention

In order to solve the problem of lower information transmission rate of a traditional frequency hopping anti-interference communication system under the space-to-ground cooperative scene, the invention aims to provide a symbol-level full-band mapping space-to-ground anti-interference method based on Turbo coding and decoding. Compared with the traditional frequency hopping spread spectrum system, the invention has the advantage of stronger anti-interference capability on the premise of equal information efficiency.

The aim of the invention is achieved by the following technical scheme.

The invention discloses a symbol-level full-band mapping space-earth anti-interference method based on Turbo coding, which is characterized in that original information with the length of K is subjected to Turbo repetition coding to obtain a low-code-rate coded Turbo codeword, the codeword is mapped to a QAM symbol by adopting high-order QAM modulation, the homologous QAM symbol is uniformly mapped to each hop by symbol-level full-band mapping, frequency hopping processing is carried out, a frequency hopping signal is obtained, and the frequency hopping signal is sent to a partial frequency band interference channel or a time domain pulse interference channel. And performing interference detection at a receiving end, performing zero-setting processing on a disturbed position, and reducing the influence of the interference on the subsequent demodulation and decoding performances of the receiver by deleting the interference in a received signal. And (3) carrying out de-hopping on the signal after zero setting, merging the homologous QAM symbols of each hop after de-interleaving, and carrying out de-mapping and decoding. The redundancy generated by the same information bit in the sample received by the receiving end is required to have an undisturbed part, so that in the iterative decoding process, the undisturbed bit can assist the disturbed bit to be converged to a correct value by utilizing the constraint relation between the encoded code words, the error rate of the decoding result output by the decoder is reduced, and the anti-interference performance of the communication system is improved.

The invention discloses a symbol-level full-band mapping space-to-ground anti-interference method based on Turbo coding, which comprises the following steps:

Step one: and determining the original information length K, the Turbo coding rate R _c and the repetition coding frequency R of the anti-interference communication system, wherein the frequency hopping frequency number h and the repetition coding frequency R meet the requirement of h < R.

And step one, determining the original information length K and the Turbo coding code rate R _c according to the channel state and the communication rate requirement of the anti-interference communication system. The repetition coding number r is flexibly set. The code rate of the channel code after repeated coding is as follows:

R＝R_c/r (1)

step two: and performing Turbo repetition coding on the original information with the length of K to obtain a low-code-rate coded Turbo codeword.

Step two the original information is expressed as u= [ u ₁,u₂,…,u_K ]. And (3) performing Turbo repetition coding with the code rate of R _c and the repetition number of R on the original information. Note that R _c =1/l, the codeword after Turbo encoding is expressed as:

c＝[c₁,c₂,…,c_K] (2)

wherein c _j (j=1, 2, …, K) is a matrix of dimension r×l:

Step three: and performing high-order M-QAM mapping on the low-code rate Turbo code word repeatedly coded in the step to map the code word to a QAM symbol.

Performing high-order M-QAM mapping on the low-code rate Turbo codeword repeatedly encoded as in equation (2) (3), where m=log ₂ M, and the mapped symbol is expressed as:

Wherein the method comprises the steps of As a matrix of dimensions r x 1:

all symbols in the same matrix s _i are called as homologous QAM symbols, and are operated Representing an upward integer arithmetic operation on x.

Step four: the symbol-level full-band mapping is used for uniformly mapping the homologous QAM symbols to h frequency hopping frequency points of a frequency hopping system, so that the interference is fully dispersed at a receiving end, and the phenomenon that the homologous QAM symbols are all overlapped and interfered is avoided, and further, the subsequent demodulation and decoding performance is reduced.

The symbol-level full-band mapping in the fourth step is realized by an interleaver pi designed according to parameters (K, l, r, m, h). The length of the interleaver pi is Kxl x r/m, and the method is used for uniformly mapping r homologous QAM symbols onto h frequency hopping frequency points:

s′＝s(π) (6)

Where s' is the frequency hopping module input signal.

Step five: and step four, performing frequency hopping processing on the s' signal and obtaining a frequency hopping signal, and transmitting the frequency hopping signal to a partial frequency band interference channel or a time domain pulse interference channel.

Step six: and step five, receiving the signal transmitted in the step five, performing interference detection, performing zero-setting processing on the interfered position, and reducing the influence of the interference on the subsequent demodulation and decoding performances of the receiver by deleting the interference in the received signal.

And step six, interference detection is carried out, and whether interference exists and the interference position are judged according to the characteristics of the interference signals. Analyzing the received signal from the time-frequency domain, wherein for partial frequency band interference, the frequency domain shows that the amplitude of the received signal in the partial frequency band exceeds a preset interference judgment threshold value; for time domain impulse interference, the time domain is represented as that the amplitude of the received signal exceeds a preset interference judgment threshold value in a part of time period. And judging the interference position according to the judgment criterion, and carrying out zero-setting processing on the interfered position.

Step seven: and (3) de-hopping the signal after zero setting, and merging the receiving end homologous QAM symbols after de-interleaving.

Step eight: and D, demodulating and decoding the combined signals in the step seven, and utilizing the constraint relation among the encoded code words through an iterative decoding process, wherein the undisturbed bits can assist the disturbed bits to converge to a correct value, so that the error rate of a decoder is reduced, and the anti-interference performance of a communication system is improved.

Step eight the demodulator is in a soft input soft output mode. According to the maximum likelihood log ratio LLR algorithm, the demodulator soft output is:

Where r is the combined signal in step seven, b _q is the bits in the corresponding symbol, and LLR (b _q) is the soft information of the bits output by the demodulator.

The decoder adopts iterative decoding, and the iterative decoding criterion is shown in formula (8):

where y refers to the decoder input, and defines the log-likelihood ratio based on the mapping of the transmitting end u=1-2 x:

the above decoding criteria is reduced to a symbol decision form as shown in equation (10):

In the decoding iteration process, the soft information of the log likelihood ratio is interacted in an iteration manner among the component decoders; after the decoding iteration is finished, outputting a judgment result And comparing the error rate with the original information u to obtain the error rate of the anti-interference system.

Step nine: uniformly mapping the homologous QAM symbols to each frequency point to avoid the influence of interference on the homologous symbols; step six, detecting and zeroing the interference, and deleting the interference as much as possible before processing the received signal; and step seven, merging signals, overlapping the disturbed bit and the undisturbed bit, facilitating demodulation and decoding in the step eight, reducing the deterioration influence of residual interference on demodulation and decoding performance, and utilizing the constraint relation between coding code words, wherein the undisturbed bit can assist the disturbed bit to converge to a correct value, thereby reducing the error rate of a decoder and improving the anti-interference performance of a communication system.

The beneficial effects are that:

1. The invention discloses a symbol-level full-band mapping space anti-interference method based on Turbo coding, which adopts a low-code-rate channel coding anti-interference system and a high-order modulation demodulation method to realize decoupling of a frequency hopping frequency conversion rate and an information rate, breaks through the hardware limitation that the existing frequency hopping system is difficult to support the high information rate, and reduces the realization complexity of a radio frequency front end and an analog-digital conversion circuit.

2. The existing low-code-rate channel coding method has the problems of high hardware resource consumption and difficult realization, and cannot be applied to an anti-interference communication system. The symbol-level full-band mapping space-earth anti-interference method based on Turbo coding adopts the repeatedly coded Turbo code word, finishes low-code-rate coding with negligible complexity, realizes time diversity effect, fully breaks up interference to improve the anti-interference performance of a communication system, and can be applied to an anti-interference communication system platform with limited hardware resources.

3. The invention discloses a symbol-level full-band mapping space-earth anti-interference method based on Turbo coding, which adopts a symbol-level full-band mapping frequency hopping method to realize symbol-by-symbol frequency and time dual diversity, wherein the frequency diversity covers the whole frequency hopping bandwidth range, and the time diversity can span hundreds or even tens of thousands of symbol periods, so that the capacity of resisting high-power partial frequency band interference and burst pulse strong interference is improved.

Drawings

In order to more clearly illustrate the technical solution according to the invention, the drawings that are used in the invention will be briefly described below. The drawings in the following description are illustrative of certain embodiments of the invention and other drawings may be made by those skilled in the art without undue burden.

Fig. 1 is a signal processing flow diagram of an anti-interference system.

Fig. 2 is a block diagram of signal processing at the transmitting end and the receiving end.

Fig. 3 shows graphs of original information length k=240, turbo coding rate R _c =1/7, repetition coding frequency r=15, frequency hopping frequency h=5, and decoder iteration frequency 8 times, and error rate under AWGN channel and scrambling condition.

Detailed Description

Example 1:

as shown in fig. 1 and fig. 2, the symbol-level full-band mapping space-to-ground anti-interference method based on Turbo coding disclosed in this embodiment includes the following steps:

Step one: and determining the original information length K, the Turbo coding rate R _c and the repetition coding frequency R of the anti-interference communication system, wherein the frequency hopping frequency number h and the repetition coding frequency R meet the requirement of h < R.

And step one, determining the original information length K and the Turbo coding code rate R _c according to the channel state and the communication rate requirement of the anti-interference communication system. The repetition coding number r is flexibly set. The code rate of the channel code after repeated coding is as follows:

R＝R_c/r (11)

step two: and performing Turbo repetition coding on the original information with the length of K to obtain a low-code-rate coded Turbo codeword.

Step two the original information is expressed as u= [ u ₁,u₂,…,u_K ]. And (3) performing Turbo repetition coding with the code rate of R _c and the repetition number of R on the original information. Note that R _c =1/l, the codeword after Turbo encoding is expressed as:

c＝[c₁,c₂,…,c_K] (12)

wherein c _j (j=1, 2, …, K) is a matrix of dimension r×l:

Step three: and performing high-order M-QAM mapping on the low-code rate Turbo code word repeatedly coded in the step to map the code word to a QAM symbol.

Performing high-order M-QAM mapping on the low-code rate Turbo codeword repeatedly encoded as in equations (12) (13), where m=log ₂ M, and the mapped symbol is expressed as:

Wherein the method comprises the steps of As a matrix of dimensions r x 1:

all symbols in the same matrix s _i are called as homologous QAM symbols, and are operated Representing an upward integer arithmetic operation on x.

Step four: the symbol-level full-band mapping is used for uniformly mapping the homologous QAM symbols to h frequency hopping frequency points of a frequency hopping system, so that the interference is fully dispersed at a receiving end, and the phenomenon that the homologous QAM symbols are all overlapped and interfered is avoided, and further, the subsequent demodulation and decoding performance is reduced.

The symbol-level full-band mapping in the fourth step is realized by an interleaver pi designed according to parameters (K, l, r, m, h). The length of the interleaver pi is Kxl x r/m, and the method is used for uniformly mapping r homologous QAM symbols onto h frequency hopping frequency points:

s′＝s(π) (16)

Where s' is the frequency hopping module input signal.

Step five: and step four, performing frequency hopping processing on the s' signal and obtaining a frequency hopping signal, and transmitting the frequency hopping signal to a partial frequency band interference channel or a time domain pulse interference channel.

Step six: and step five, receiving the signal transmitted in the step five, performing interference detection, performing zero-setting processing on the interfered position, and reducing the influence of the interference on the subsequent demodulation and decoding performances of the receiver by deleting the interference in the received signal.

And step six, interference detection is carried out, and whether interference exists and the interference position are judged according to the characteristics of the interference signals. Analyzing the received signal from the time-frequency domain, wherein for partial frequency band interference, the frequency domain shows that the amplitude of the received signal in the partial frequency band exceeds a preset interference judgment threshold value; for time domain impulse interference, the time domain is represented as that the amplitude of the received signal exceeds a preset interference judgment threshold value in a part of time period. And judging the interference position according to the judgment criterion, and carrying out zero-setting processing on the interfered position.

Step seven: and (3) de-hopping the signal after zero setting, and merging the receiving end homologous QAM symbols after de-interleaving.

Step eight: and D, demodulating and decoding the combined signals in the step seven, and utilizing the constraint relation among the encoded code words through an iterative decoding process, wherein the undisturbed bits can assist the disturbed bits to converge to a correct value, so that the error rate of a decoder is reduced, and the anti-interference performance of a communication system is improved.

Step eight the demodulator is in a soft input soft output mode. According to the maximum likelihood log ratio LLR algorithm, the demodulator soft output is:

Where r is the combined signal in step seven, b _q is the bits in the corresponding symbol, and LLR (b _q) is the soft information of the bits output by the demodulator.

The decoder adopts iterative decoding, and the iterative decoding criterion is shown in formula (18):

where y refers to the decoder input, and defines the log-likelihood ratio based on the mapping of the transmitting end u=1-2 x:

the above decoding criteria is reduced to a symbol decision form as shown in equation (20):

In the decoding iteration process, the soft information of the log likelihood ratio is interacted in an iteration manner among the component decoders; after the decoding iteration is finished, outputting a judgment result And comparing the error rate with the original information u to obtain the error rate of the anti-interference system.

Step nine: uniformly mapping the homologous QAM symbols to each frequency point to avoid the influence of interference on the homologous symbols; step six, detecting and zeroing the interference, and deleting the interference as much as possible before processing the received signal; and step seven, merging signals, overlapping the disturbed bit and the undisturbed bit, facilitating demodulation and decoding in the step eight, reducing the deterioration influence of residual interference on demodulation and decoding performance, and utilizing the constraint relation between coding code words, wherein the undisturbed bit can assist the disturbed bit to converge to a correct value, thereby reducing the error rate of a decoder and improving the anti-interference performance of a communication system.

In the simulation of fig. 2, the set parameters are: original information length k=240, turbo coding rate R _c =1/7, repetition coding number r=15, frequency hopping number h=5, and decoder iteration number 8. As can be seen from the observation image, the invention has stronger strong interference capability.

In the simulation of partial band interference, the interference bandwidth is 40%, the anti-interference system still has stronger error correction capability, and compared with the non-interference condition, the performance is only backed off by 2.4dB (@BER=1E-5). In the simulation of the time domain pulse interference, the interference duty ratio is 0.01, and the system has almost no performance loss.

What has been described above is the main content of the symbol-level full-band mapping space-to-ground anti-interference method based on Turbo coding. Through the simulation experiment, the anti-interference performance of the symbol-level full-band mapping space-to-ground anti-interference method based on the Turbo coding can be evaluated and compared.

Claims (7)

1. A symbol-level full-band mapping space-to-ground anti-interference method based on Turbo coding and decoding is characterized by comprising the following steps of: comprises the following steps of the method,

Step one: determining the original information length K, the Turbo coding rate R _c and the repetition coding frequency R of an anti-interference communication system, wherein the frequency hopping frequency number h and the repetition coding frequency R meet the requirement of h < R;

Step two: performing Turbo repetition coding on original information with the length of K to obtain a low-code-rate coded Turbo codeword;

Step three: performing high-order M-QAM mapping on the low-code rate Turbo code word repeatedly coded in the step to map the code word to a QAM symbol;

step four: uniformly mapping the homologous QAM symbols to h frequency hopping frequency points of a frequency hopping system through symbol-level full-band mapping, and fully scattering interference at a receiving end to avoid overlapping interference of the homologous QAM symbols so as to reduce the subsequent demodulation and decoding performance;

step five: performing frequency hopping processing on the s' signal in the fourth step to obtain a frequency hopping signal, and transmitting the frequency hopping signal to a partial frequency band interference channel or a time domain pulse interference channel;

Step six: receiving the signal transmitted in the fifth step, performing interference detection, performing zero-setting processing on the interfered position, and reducing the influence of the interference on the subsequent demodulation and decoding performances of the receiver by deleting the interference in the received signal;

step seven: the signals after zero setting are subjected to de-hopping, and after de-interleaving, the receiving end homologous QAM symbols are combined;

step eight: demodulating and decoding the signals combined in the step seven, and utilizing the constraint relation between the encoded code words to assist the undisturbed bits to converge to a correct value through an iterative decoding process;

Step nine: uniformly mapping the homologous QAM symbols to each frequency point to avoid the influence of interference on the homologous symbols; step six, detecting and zeroing the interference, and deleting the interference as much as possible before processing the received signal; and step seven, merging signals, superposing disturbed bits and undisturbed bits, reducing the deterioration influence of residual interference on demodulation and decoding performance through demodulation and decoding in the step eight, and utilizing the constraint relation between coding code words, wherein the undisturbed bits can assist the disturbed bits to converge to a correct value, so that the error rate of a decoder is reduced, and the anti-interference performance of a communication system is improved.

2. The symbol-level full-band mapping space-time anti-interference method based on Turbo coding as claimed in claim 1, wherein: step one, the original information length K and the Turbo coding code rate R _c are determined according to the channel state and the communication rate requirement of the anti-interference communication system; flexibly setting the repetition coding frequency r; the code rate of the channel code after repeated coding is as follows:

R＝R_c/r (1)。

3. The symbol-level full-band mapping space-time anti-interference method based on Turbo coding as claimed in claim 2, wherein: step two, the original information is expressed as u= [ u ₁,u₂,…,u_K ]; performing Turbo repetition coding with the code rate of R _c and the repetition number of R on the original information; note that R _c =1/l, the codeword after Turbo encoding is expressed as:

c＝[c₁,c₂,…,c_K] (2)

wherein c _j (j=1, 2, …, K) is a matrix of dimension r×l:

4. The symbol-level full-band mapping space-time anti-interference method based on Turbo coding as claimed in claim 3, wherein: in the third step, the first step is performed,

Performing high-order M-QAM mapping on the low-code rate Turbo codeword repeatedly encoded as in equation (2) (3), where m=log ₂ M, and the mapped symbol is expressed as:

Wherein the method comprises the steps of As a matrix of dimensions r x 1:

all symbols in the same matrix s _i are called as homologous QAM symbols, and are operated Representing an upward integer arithmetic operation on x.

5. The symbol-level full-band mapping space-time anti-interference method based on Turbo coding as claimed in claim 4, wherein: step four, the symbol-level full-band mapping is realized through an interleaver pi designed according to parameters (K, l, r, m, h); the length of the interleaver pi is Kxl x r/m, and the method is used for uniformly mapping r homologous QAM symbols onto h frequency hopping frequency points:

s′＝s(π) (6)

Where s' is the frequency hopping module input signal.

6. The symbol-level full-band mapping space-time anti-interference method based on Turbo coding as claimed in claim 5, wherein: step six, interference detection is carried out, and whether interference exists or not and the interference position are judged according to the characteristics of the interference signals; analyzing the received signal from the time-frequency domain, wherein for partial frequency band interference, the frequency domain shows that the amplitude of the received signal in the partial frequency band exceeds a preset interference judgment threshold value; for time domain pulse interference, the time domain shows that the amplitude of a received signal exceeds a preset interference judgment threshold value in a part of time period; and judging the interference position according to the judgment criterion, and carrying out zero-setting processing on the interfered position.

7. The symbol-level full-band mapping space-time anti-interference method based on Turbo coding as claimed in claim 6, wherein: step eight, the demodulator is in a soft input and soft output mode; according to the maximum likelihood log ratio LLR algorithm, the demodulator soft output is:

wherein r is the combined signal in step seven, b _q is the bit in the corresponding symbol, and LLR (b _q) is the soft information of the bit output by the demodulator;

The decoder adopts iterative decoding, and the iterative decoding criterion is shown in formula (8):

where y refers to the decoder input, and defines the log-likelihood ratio based on the mapping of the transmitting end u=1-2 x:

the above decoding criteria is reduced to a symbol decision form as shown in equation (10):

In the decoding iteration process, the soft information of the log likelihood ratio is interacted in an iteration manner among the component decoders; after the decoding iteration is finished, outputting a judgment result And comparing the error rate with the original information u to obtain the error rate of the anti-interference system.