Transmission rate adaptive dual sequence frequency hopping communication method

Abstract

The invention discloses a dual sequence frequency hopping communication method with a self-adaptive transmission rate, and relates to the technical field of frequency hopping communication, the method maps a transmission signal to a frequency hopping sequence number and an information modulation part, the information modulation part adopts a direct sequence spread spectrum communication mode, and the spread spectrum gain is adjusted based on a variable spread spectrum factor; and thus, information transmission rate self-adaption is realized. When the use environment of a frequency hopping communication system is severe, the signal-to-noise ratio is low, and large-range even full-band communication interference exists. At the moment, the system adjusts a spreading factor of direct sequence spreading according to feedback information of an error rate detection module, and the reliable communication performance of the system is improved by increasing the spreading factor so as to meet the requirement of receiving a signal-to-noise ratio, so that reliable communication between two communication parties is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency hopping communications, and in particular to a dual sequence frequency hopping communication method with adaptive transmission rate. Background Art

[0002] Frequency-hopping communication (FH) is widely used in wireless communications due to its excellent anti-interference capabilities. With the deterioration of the electromagnetic environment and the need for electronic countermeasures, wireless communications are facing higher demands for communication reliability and anti-interference capabilities. However, conventional FH communications use a pre-defined frequency-hopping pattern, allowing interference-prone hopping frequencies to continue participating in the communication process. This ignores the impact of interference on communication quality, making it difficult to cope with channel variations.

[0003] Adaptive communication refers to radio communications that automatically adapt to changing communication conditions. Specifically, it refers to a communication method that can timely monitor the transmission environment and automatically adjust the operating state of system equipment based on the monitoring results. Adaptive communication technology is also a form of anti-interference technology, capable of actively and passively avoiding or minimizing the impact of interference on the communication process. With the development of communication interference and anti-interference technology, adaptive frequency hopping technology, which combines frequency hopping communication with adaptive technology, has emerged.

[0004] Adaptive communication technology encompasses features such as adaptive frequency, adaptive power, adaptive transmission rate, adaptive hopping speed, and adaptive direction, facilitating multi-dimensional interference mitigation. Adaptive rate communication technology adaptively changes the modulation method, information transmission rate, or coding scheme based on channel characteristics, thereby improving channel utilization, reducing the system's bit error rate performance, and increasing system throughput. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to provide a dual sequence frequency hopping communication method that can effectively improve the reliability of communication between two communicating parties.

[0006] To solve the above technical problems, the present invention adopts a technical solution: a dual sequence frequency hopping communication method with adaptive transmission rate, comprising the following steps:

[0007] S1, using channel coding to perform error control coding on the signal to be transmitted provided by the source, and grouping the coded sequence B of length K into L sequences of equal length;

[0008] S2, after performing serial-to-parallel conversion on the above sequence, mapping it to the frequency hopping sequence mapping channel and data modulation channel for processing;

[0009] S3, the frequency hopping sequence mapping channel completes the frequency hopping sequence selection and realizes the dual sequence frequency hopping;

[0010] S4: The data modulation channel implements direct sequence spread spectrum communication, changing the information transmission rate by adjusting the spreading factor. To complete channel quality estimation, channel test data items are inserted into the transmitted data frame. The spread spectrum modulated signal output by the data modulation channel is mixed and, after spectrum shifting, sent to the transmit RF front end.

[0011] S5, after the transmitter completes the bandpass filtering and power amplification of the frequency hopping signal, it is transmitted through the transmitter antenna;

[0012] S6, the receiving end RF front end processes the RF signal received from the transmitting end antenna and sends it to Ns receiving channels; the receiving end has N s The receiving channels work in parallel, corresponding to N s For each channel, the local frequency hopping sequence generated by the receiving end is synchronized with the transmitting end, and the received signal is synchronized with the local frequency hopping sequence to achieve frequency hopping demodulation;

[0013] S7, for each receiving channel, complete the intermediate frequency signal of the frequency hopping demodulation and send it to the energy detection channel and the data demodulation channel respectively;

[0014] S8, in each energy detection channel, the intermediate frequency signal after de-hopping is filtered and then subjected to square-rate non-coherent detection. s The detection results are mapped into binary bit detection results and sent to the comprehensive decision module for judgment;

[0015] S9, in each data demodulation channel, the spread spectrum modulated signal after de-hopping is correlated and de-spread using a pseudo-random code sequence synchronized with the transmitting end, and then demodulated to recover the transmitted information;

[0016] S10, when making a comprehensive judgment, N s The energy detection results of the receiving channels are used to make a decision. s receiving channels, and the result of square-rate incoherent detection of each channel is R i ,i=1,…,N s ;

[0017] S11, the channel quality assessment module uses the energy detection result and the intermediate frequency signal output by the comprehensive judgment to estimate the signal-to-noise ratio, predicts the subsequent state of the channel through the Kalman filter, and then compares the channel quality change value with the threshold to obtain information on whether the channel quality has improved or deteriorated;

[0018] S12: The status information of the channel quality change is fed back to the transmitter via the dual sequence channel. The transmitter modulates the spreading factor based on the change in channel quality. If the channel quality improves, a shorter spreading factor is selected. If the channel quality deteriorates, a longer spreading factor is selected. If the change in channel quality is small, the spreading factor remains unchanged.

[0019] S13, performing parallel-to-serial conversion and combining on the output signals of each hop, performing channel decoding on the combined signals, and then sending the information to the destination.

[0020] The beneficial effects of adopting the above technical solution are: this method effectively utilizes the multi-channel resources in the dual sequence frequency hopping communication system, realizes that the information transmission rate of the multi-even channel frequency hopping communication is adjusted as the channel quality changes; the dual sequence frequency hopping channel is used as a management channel to feed back channel perception results and adjustment control information; the direct sequence spread spectrum communication channel is used to transmit information at a variable rate and perceive the channel quality at the same time, taking into account flexibility and ensuring the reliability of the adaptive feedback control channel; compared with conventional dual sequence frequency hopping, the information rate is effectively improved without increasing the hopping rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1a-Figure 1b is a main flow chart of the method according to an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of transmitter binary sequence modulation mapping in the method according to an embodiment of the present invention;

[0024] Figure 3 is a processing flow chart of the transmitting end in the method according to an embodiment of the present invention;

[0025] Figure 4 is a processing flow chart of the receiving end in the method according to an embodiment of the present invention;

[0026] Figure 5 This is a principle block diagram of the despreading and demodulating unit in the method according to the embodiment of the present invention.

[0027] Figure 6 It is a principle block diagram of the feedback loop of the dual channel frequency hopping communication system in the method described in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0029] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0030] like Figure 1a-Figure 1b As shown, the embodiment of the present invention discloses a dual sequence frequency hopping communication method with adaptive transmission rate, comprising the following steps:

[0031] S1, using channel coding to perform error control coding on the signal to be transmitted provided by the source, and grouping the coded sequence B of length K into L sequences of equal length;

[0032] S2, after performing serial-to-parallel conversion on the above sequence, mapping it to the frequency hopping sequence mapping channel and data modulation channel for processing;

[0033] S3, the frequency hopping sequence mapping channel completes the frequency hopping sequence selection and realizes the dual sequence frequency hopping;

[0034] S4: The data modulation channel implements direct sequence spread spectrum communication, changing the information transmission rate by adjusting the spreading factor. To complete channel quality estimation, channel test data items are inserted into the transmitted data frame. The spread spectrum modulated signal output by the data modulation channel is mixed and, after spectrum shifting, sent to the transmit RF front end.

[0035] S5, after the transmitter completes the bandpass filtering and power amplification of the frequency hopping signal, it is transmitted through the transmitter antenna;

[0036] S6, the receiving end RF front end processes the RF signal received from the transmitting end antenna and sends it to Ns receiving channels; the receiving end has N s The receiving channels work in parallel, corresponding to N s For each channel, the local frequency hopping sequence generated by the receiving end is synchronized with the transmitting end, and the received signal is synchronized with the local frequency hopping sequence to achieve frequency hopping demodulation;

[0037] S7, for each receiving channel, complete the intermediate frequency signal of the frequency hopping demodulation and send it to the energy detection channel and the data demodulation channel respectively;

[0038] S8, in each energy detection channel, the intermediate frequency signal after de-hopping is filtered and then subjected to square-rate non-coherent detection. s The detection results are mapped into binary bit detection results and sent to the comprehensive decision module for judgment;

[0039] S9, in each data demodulation channel, the spread spectrum modulated signal after de-hopping is correlated and de-spread using a pseudo-random code sequence synchronized with the transmitting end, and then demodulated to recover the transmitted information;

[0040] S10, when making a comprehensive judgment, N s The energy detection results of the receiving channels are used to make a decision. s receiving channels, and the result of square-rate incoherent detection of each channel is R i ,i=1,…,N s ;

[0041] S11, the channel quality assessment module uses the energy detection result and the intermediate frequency signal output by the comprehensive judgment to estimate the signal-to-noise ratio, predicts the subsequent state of the channel through the Kalman filter, and then compares the channel quality change value with the threshold to obtain information on whether the channel quality has improved or deteriorated;

[0042] S12: The status information of the channel quality change is fed back to the transmitter via the dual sequence channel. The transmitter modulates the spreading factor based on the change in channel quality. If the channel quality improves, a shorter spreading factor is selected. If the channel quality deteriorates, a longer spreading factor is selected. If the change in channel quality is small, the spreading factor remains unchanged.

[0043] S13, performing parallel-to-serial conversion and combining on the output signals of each hop, performing channel decoding on the combined signals, and then sending the information to the destination.

[0044] The present invention maps the transmission signal into two parts: a frequency hopping sequence number and information modulation. The information modulation part uses direct sequence spread spectrum communication, adjusting the spreading gain based on a variable spreading factor to achieve adaptive information transmission rate. When a frequency hopping communication system is used in a harsh environment with a low signal-to-noise ratio and the presence of wide-range or even full-band communication interference, the system adjusts the direct sequence spread spectrum spreading factor based on feedback from the bit error rate detection module. By increasing the spreading factor, the system reduces the system's requirement for reliable communication, thereby achieving reliable communication between the two communicating parties.

[0045] The process of transmitting and receiving signals:

[0046] At the transmitter, the signal to be transmitted is channel coded and serial-to-parallel converted, and then represented by the frequency hopping sequence number and digital modulation symbol. At the same time, the corresponding frequency hopping sequence is output and used as the current transmission carrier after frequency synthesis. The digital modulation symbol signal is baseband modulated and spread spectrum, and then sent out by the hopping carrier. The transmitter binary sequence modulation mapping principle is as follows: Figure 2 The transmission principle diagram of the rate adaptive dual channel frequency hopping communication system is shown in Figure 3 shown.

[0047] The signal transmission of the transmitter includes the following steps:

[0048] (1) Channel coding is used to perform error control coding on the signal to be transmitted provided by the source, and convolutional coding is selected as the coding method. It should be noted that channel coding methods such as low-density parity check (LDPC), turbo code, and RS code can also be selected.

[0049] (2) Group the encoded sequence B of length K into L sequences of equal length {B1, B2, B3, ..., B L}, where B i , (i=1,…,L) are all of length K1. i ,(i=1,…,L), after serial-to-parallel conversion [b i,1 ,b i,2 ], b i,1 The length is K N， b i,2 The length is K M The number of sequences used for frequency hopping transmission is N s , K N =log2N s .

[0050] (3)B i , (i=1,…,L) After serial-to-parallel conversion, it is divided into b i,1 ,b i,2 Two parts, b i,1 Sent to the sequence mapping channel to select the frequency hopping sequence, b i,2 Sent to the data modulation channel.

[0051] (4) In the sequence mapping channel, the binary b i,1 Convert to N s Base, N s is the number of frequency hopping sequences used for transmission. i,1 The corresponding sequence is selected by the numerical value of , and the frequency point of the sequence is used as the transmitting carrier frequency after frequency synthesis.

[0052] (5) In the data modulation channel, the data is first baseband modulated, and the channel test data item is inserted into the transmission data frame. Then, a spreading code of a certain length is selected from the spreading code set to perform direct sequence spreading to obtain a direct sequence spread spectrum signal.

[0053] (6) The transmit carrier frequency synthesized by the sequence mapping channel is used to mix the spread spectrum modulated signal output by the data modulation channel, and after the spectrum is shifted, it is sent to the RF front end.

[0054] (7) After the RF front end completes the frequency hopping signal bandpass filtering and power amplification, it is transmitted through the transmitting antenna.

[0055] At the receiving end, the signal received by the RF front end is sent to N s Each receiving channel uses a local frequency hopping sequence to synchronize the received signal and realize frequency hopping demodulation. Then, the signal is subjected to square law non-coherent detection and correlation despreading and baseband demodulation respectively. s The energy detection result of the receiving channel is judged and the receiving channel is determined. After parallel-serial conversion, it is sent to the channel decoding unit and the decoding result is sent to the destination. The receiving principle block diagram is shown in the figure. Figure 4 shown.

[0056] The signal reception of the receiver includes the following steps:

[0057] (1) The receiving RF front end receives the RF signal from the antenna, performs low-noise amplification, bandpass filtering, and gain control, and then sends it to the N s receive channels.

[0058] (2) The receiving end is equipped with N s The receiving channels work in parallel, corresponding to N s Each receiving path is narrowband. For each channel, the local frequency hopping sequence generated by the receiver is synchronized with the transmitter. That is, the received signal is synchronized with the local frequency hopping sequence, thereby achieving frequency hopping demodulation.

[0059] (3) For each receiving channel, the intermediate frequency signal after frequency hopping demodulation is sent to the energy detection channel and the data demodulation channel respectively.

[0060] (4) In each energy detection channel, the intermediate frequency signal after de-hopping is narrow-band filtered and then square-rate incoherent detection is performed. s The detection results are mapped into binary bit detection results and sent to the comprehensive decision module for judgment.

[0061] (5) In each data demodulation channel, the spread spectrum modulated signal after de-hopping is correlated and de-spread using a pseudo-random code sequence synchronized with the transmitting end, and then demodulated to recover the transmitted information.

[0062] (6) In making a comprehensive judgment, it is necessary to include N s The decision is made based on the energy detection results of the receiving channel. The decision method can be hard decision or soft decision combined with the decoding method. s receiving channels, and the result of square-rate incoherent detection of each channel is R i ,(i=1,…,N s ).

[0063] If the hard decision method is adopted, let N s The maximum value of the non-coherent detection result of the receiving channel is R max =max{R1,R2,…,R Ns}, using R max For all N s The detection results are normalized, R S1 For all normalized N s The average of the detection results. Set the threshold T R , if 1 / R S1 ≥T R , then R max The corresponding receiving channel i is judged as the current sequence frequency point. The comprehensive judgment unit outputs the sequence number and data demodulation information of the channel where the sequence is located.

[0064] If a soft decision method is used, a large soft decision method is selected to construct the decision variable. Assuming that the decision output is Y, then:

[0065] Y = max {R associated with bit 0 i}-max{R associated with bit 1 i};

[0066] Among them, in N s R i In the example, R related to bits 0 and 1 i Each occupies M / 2, where "related to bit 0 (or 1)" means that when a bit in the binary bit group is 0 or 1, the entire binary bit group can only be mapped to certain specific M-ary symbols, and the final incoherent detection result of these symbols is R i ,Finally, the soft decision output Y is sent to the decoder for Viterbi decoding;

[0067] (7) The channel quality assessment module uses the energy detection results and intermediate frequency signals output by the comprehensive judgment to estimate the signal-to-noise ratio, predicts the subsequent state of the channel through the Kalman filter, and then compares the channel quality change value with the threshold to obtain information on whether the channel quality has improved or deteriorated;

[0068] (8) The status information of the channel quality change is fed back to the transmitter through the dual sequence channel. The transmitter modulates the spreading factor according to the channel quality change. If the channel quality improves, a shorter spreading factor is selected. If the channel quality deteriorates, a longer spreading factor is selected. If the channel quality change is small;

[0069] (9) The output signals of each hop are combined by parallel-to-serial conversion; the combined signals are channel-decoded and then sent to the destination. Here, Viterbi decoding is selected as the convolutional coding method.

[0070] A variable processing gain control circuit is added to the transmitter, and the structural block diagram is shown in the figure. Figure 5 As shown, the crystal oscillator controls n PN code sequence generators after passing through a phase-locked loop, outputting n PN codes of different lengths to the gate. The data rate control information contained in the input compressed image data stream is used as the gate signal of the gate. Based on this information, the PN code is selected to correspond to different processing gains. A higher data rate corresponds to a shorter PN code, and a lower rate corresponds to a longer PN code, so that the system always works in the best state.

[0071] Spread spectrum code selection:

[0072] The processing gain of a DSSS system against interference is approximately equal to its spreading factor. Therefore, increasing the spreading factor can significantly increase the processing gain, thereby improving system performance. Because the autocorrelation of spreading codewords significantly impacts system performance, code patterns of varying lengths and exhibiting good autocorrelation characteristics can be selected as spreading codewords. For example, Barker codes with a spreading factor of 11, Gold codes with a spreading factor of 31, and M-sequence spreading codes with spreading factors of 63, 127, 255, and 511 can be selected.

[0073] Channel quality estimation:

[0074] After demodulation at the receiving end, the signal-to-noise ratio is estimated. The Kalman filter is then used to predict the future state of the channel. Finally, the predicted channel state is compared with a threshold. If the predicted signal-to-noise ratio falls below the threshold, the channel is considered poor quality and requires adjustment. Otherwise, the channel is considered good quality and no adjustment is required.

[0075] The channel quality assessment based on the received signal noise ratio prediction algorithm is performed as follows:

[0076] In each frequency hopping interval, the signal is sampled without distortion to generate a sampling sequence;

[0077] Calculate the autocorrelation matrix of the signal sampling sequence, perform matrix singular value decomposition to obtain the singular value sequence, find the difference of the sequence, determine the signal subspace dimension based on the inflection point, and calculate the signal-to-noise ratio estimate;

[0078] The estimated signal-to-noise ratio value is used as the input of the Kalman filter to predict the signal-to-noise ratio value of the next frequency hopping cycle of the corresponding channel and output the predicted value;

[0079] The predicted value is compared with the threshold value. The comparison result is used to judge whether the channel is good or bad in the adaptive rate control and to select the sequence selection control command to increase or decrease the length of the spreading sequence;

[0080] After a certain step of a channel is completed, the same step of the next channel is started, and the next evaluation step of this channel is entered at the same time.

[0081] Feedback adjustment loop:

[0082] 1) Rate adaptive feedback loop composition:

[0083] Adaptive frequency hopping communication is a closed-loop control system that evaluates the channel quality at the receiving end and transmits the results to the sender via the reverse channel, which is then used as a basis for adaptive frequency and power control. Figure 5 As shown in the figure, take two adaptive dual-channel frequency-hopping transceivers, A and B, as an example. Both ends have the same test data set. End A initiates a test, selects test data from the test data set, and sends it via the DSSS channel. End B receives the test data via the DSSS channel, performs channel quality estimation, and sends the channel quality estimation result to End A via the dual-sequence frequency-hopping channel. Ends A and B then change the spreading sequence based on the channel quality estimation result and continue communication.

[0084] In practice, there are two methods for channel quality estimation. One is to perform channel bit error rate testing by transmitting a consistent set of test data at both ends, and use the bit error rate to estimate channel quality. The other is to estimate the signal-to-noise ratio at the receiving end by sending data, and use the signal-to-noise ratio to estimate channel quality.

[0085] 2) Rate Adaptive Feedback Loop Adjustment Method:

[0086] The core idea of rate adaptive feedback loop adjustment is to use the results of channel quality assessment to adjust the spreading sequence to adapt to different channel conditions.

[0087] The channel quality assessment based on the received signal noise ratio prediction algorithm is performed in the following steps.

[0088] The transmitting end (end A) transmits a frame with inserted channel test data using a direct spread spectrum channel;

[0089] The receiving end (B) samples the signal without distortion within each frequency hopping interval to generate a sampling sequence. The autocorrelation matrix of the signal sampling sequence is calculated, and the matrix singular value decomposition is performed to obtain a singular value sequence. The sequence difference is calculated, and the signal subspace dimension is determined based on the inflection point. The signal-to-noise ratio estimate is calculated.

[0090] The receiving end (B) uses the SNR estimate as the input of the Kalman filter, predicts the SNR value of the next frequency hopping cycle of the corresponding channel, and outputs the predicted value;

[0091] The receiving end (B) feeds back the channel quality estimation result to the transmitting end (A) using the dual sequence frequency hopping channel;

[0092] The transmitter (A) compares the predicted value with the threshold value. The comparison result is used in adaptive rate control to determine whether the channel is good or bad and to select the sequence selection control command to increase or decrease the length of the spreading sequence.

[0093] The transmitter (A) uses a dynamic threshold algorithm to determine the spread spectrum sequence adjustment scheme and sends the adjustment result to the receiver (B) using a dual sequence frequency hopping channel.

[0094] The transmitting end (end A) and the receiving end (end B) perform direct spread spectrum communication according to the updated spreading sequence. After one channel assessment adjustment, the next adjustment assessment step begins.

[0095] The method described in the present invention maps the transmission signal into two components: a frequency hopping sequence number and information modulation. The information modulation component utilizes direct sequence spread spectrum communication, adjusting the spreading gain based on a variable spreading factor to achieve adaptive information transmission rate. When a frequency hopping communication system is used in a harsh environment with a low signal-to-noise ratio and widespread, or even full-band, communication interference, the system adjusts the direct sequence spread spectrum spreading factor based on feedback from the bit error rate detection module. By increasing the spreading factor, the system reduces the system's requirement for reliable communication, thereby achieving reliable communication between the two communicating parties.

Claims

1. A dual sequence frequency hopping communication method with adaptive transmission rate, characterized in that The steps include: S1, using channel coding to perform error control coding on the signal to be transmitted provided by the source, and grouping the coded sequence B of length K into L sequences of equal length; S2, after performing serial-to-parallel conversion on the above sequence, mapping it to the frequency hopping sequence mapping channel and data modulation channel for processing; S3, the frequency hopping sequence mapping channel completes the frequency hopping sequence selection and realizes the dual sequence frequency hopping; S4, the data modulation channel implements direct sequence spread spectrum communication, and the information transmission rate is changed by adjusting the spreading factor; Insert channel test data items into the transmitted data frame to complete channel quality estimation; mix the spread spectrum modulated signal output by the data modulation channel, complete spectrum shifting, and send it to the transmitting RF front end; S5, after the transmitter completes the bandpass filtering and power amplification of the frequency hopping signal, it is transmitted through the transmitter antenna; S6, the receiving end RF front end processes the RF signal received from the transmitting end antenna and sends it to Ns receiving channels; the receiving end has N s The receiving channels work in parallel, corresponding to N s For each channel, the local frequency hopping sequence generated by the receiving end is synchronized with the transmitting end, and the received signal is synchronized with the local frequency hopping sequence to achieve frequency hopping demodulation; S7, for each receiving channel, complete the intermediate frequency signal of the frequency hopping demodulation and send it to the energy detection channel and the data demodulation channel respectively; S8, in each energy detection channel, the intermediate frequency signal after de-hopping is filtered and then subjected to square-rate non-coherent detection. s The detection results are mapped into binary bit detection results and sent to the comprehensive decision module for judgment; S9, in each data demodulation channel, the spread spectrum modulated signal after de-hopping is correlated and de-spread using a pseudo-random code sequence synchronized with the transmitting end, and then demodulated to recover the transmitted information; S10, when making a comprehensive judgment, N s The energy detection results of the receiving channels are used to make a decision. s receiving channels, and the result of square-rate incoherent detection of each channel is R i ,i=1,…,N s ; S11, the channel quality assessment module uses the energy detection result and the intermediate frequency signal output by the comprehensive judgment to estimate the signal-to-noise ratio, predicts the subsequent state of the channel through the Kalman filter, and then compares the channel quality change value with the threshold to obtain information on whether the channel quality has improved or deteriorated; S12: The status information of the channel quality change is fed back to the transmitter via the dual sequence channel. The transmitter modulates the spreading factor based on the change in channel quality. If the channel quality improves, a shorter spreading factor is selected. If the channel quality deteriorates, a longer spreading factor is selected. If the change in channel quality is small, the spreading factor remains unchanged. S13, performing parallel-to-serial conversion and combining on the output signals of each hop, performing channel decoding on the combined signals, and then sending the information to the destination.

2. The dual sequence frequency hopping communication method with adaptive transmission rate according to claim 1, wherein: The step S1 specifically includes the following steps: Channel coding is used to perform error control coding on the signal to be transmitted provided by the source, and a coding method is selected to group the coded sequence B of length K into L sequences of equal length {B1, B2, B3, ..., B L }, where B i ,(i=1,…,L) are all of length K1.

3. The dual sequence frequency hopping communication method with adaptive transmission rate according to claim 2, wherein: The step S2 specifically includes the following steps: Sequence element B i , (i=1,…,L), after serial-to-parallel conversion, it becomes [b i,1 ,b i,2 ], where b i,1 The length is K N , b i,2 The length is K M ; The number of sequences used for frequency hopping transmission is N s , K N =log2N s ; b i,1 Sent to the frequency hopping sequence mapping channel to select the frequency hopping sequence, b i,2 Sent to the data modulation channel.

4. The dual sequence frequency hopping communication method with adaptive transmission rate according to claim 2, wherein: In the step S3: In the sequence mapping channel, the binary b i,1 Convert to N s Base, N s is the frequency hopping sequence number used for transmission; according to the converted b i,1 The corresponding sequence is selected by the numerical value of , and the frequency point of the sequence is used as the transmitting carrier frequency after frequency synthesis.

5. The dual sequence frequency hopping communication method with adaptive transmission rate according to claim 1, wherein: In the step S4: By selecting spreading codes of different lengths, the spreading factor can be changed. At the same time, the channel quality is sensed, and the dual sequence hopping channel is used as a management channel to feed back the channel sensing results and adjustment control information, thereby adjusting the information transmission rate as the channel quality changes.

6. The dual sequence frequency hopping communication method with adaptive transmission rate according to claim 5, wherein: The transmitter initiates a test, selects test data from the test data set, and sends it through the direct-spread channel. The receiver receives the test data through the direct-spread channel, performs channel quality estimation, and sends the channel quality estimation result to the transmitter through the dual sequence hopping channel. The transmitter and receiver change the spreading sequence based on the channel quality estimation result and continue communication.

7. The dual sequence frequency hopping communication method with adaptive transmission rate according to claim 6, wherein: The channel quality assessment method based on the received signal noise ratio prediction algorithm includes the following steps: The transmitting end transmits a frame with inserted channel test data using a direct spread spectrum channel; The receiver samples the signal without distortion within each frequency hopping interval to generate a sampling sequence. The receiver calculates the autocorrelation matrix of the signal sampling sequence, performs matrix singular value decomposition to obtain a singular value sequence, takes the difference of the sequence, determines the signal subspace dimension based on the inflection point, and calculates the signal-to-noise ratio estimate. The receiving end uses the SNR estimate as the input of the Kalman filter, predicts the SNR value of the next frequency hopping cycle of the corresponding channel, and outputs the predicted value; The receiving end feeds back the channel quality estimation result to the transmitting end using the dual sequence frequency hopping channel; The transmitter compares the predicted value with the threshold value. The comparison result is used in adaptive rate control to determine whether the channel is good or bad and to select the sequence selection control command to increase or decrease the length of the spreading sequence. The transmitter uses a dynamic threshold algorithm to determine the spread spectrum sequence adjustment scheme and uses a dual sequence frequency hopping channel to send the adjustment result to the receiver. The transmitting end and the receiving end perform direct spread spectrum communication according to the updated spreading sequence. After one channel assessment and adjustment, the next adjustment and assessment step begins.

8. The dual sequence frequency hopping communication method with adaptive transmission rate according to claim 1, characterized in that Adopting hard decision method in comprehensive decision making: Let N s The maximum value of the non-coherent detection result of the receiving channel is R max =max{R1,R2,…,R Ns }, using R max For all N s The detection results are normalized, R S1 For all normalized N s The mean of the detection results; set the threshold T R , if 1 / R S1 ≥T R , then R max The corresponding receiving channel i is determined to be the frequency point of the current sequence, and the comprehensive decision unit outputs the sequence number and data demodulation information of the channel where the sequence is located.

9. The dual sequence frequency hopping communication method with adaptive transmission rate according to claim 1, characterized in that When using the soft decision method in comprehensive decision making, assuming the decision output is Y, we have: Y = max {R associated with bit 0 i }-max{R associated with bit 1 i } Among them, in N s R i In the example, R related to bits 0 and 1 i Each occupies M / 2, and the bit 0 or 1 is related to the fact that when a certain bit in the binary bit group is 0 or 1, the entire binary bit group can only be mapped to certain specific M-ary symbols. The final incoherent detection result of these symbols is R i ,Finally, the soft decision output Y is sent to the decoder for Viterbi decoding.

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