A two-level frequency hopping method based on message driving

Abstract

The present invention discloses a message-driven two-stage frequency hopping method, which relates to the field of communication technology. It includes: physical layer processing at the transmitting end: channel coding and data segmentation, modulation and serial-to-parallel conversion, subcarrier frequency hopping position sequence generation, subcarrier mapping and OFDM modulation, radio frequency hopping sequence generation, frequency shifting and signal transmission; the receiving end physical layer performs the inverse transformation of the corresponding steps of the transmitting end physical layer to restore the data. The present invention does not transmit all the data through the wireless channel, but hides part of the data in the frequency hopping sequence, and uses the unpredictability of the sent message at the subcarrier level and the radio frequency level to achieve true random frequency hopping. Compared with the traditional pseudo-random sequence-based frequency hopping scheme, it makes it impossible for attackers to predict the communication frequency, nor to obtain all the data from the wireless channel, and can effectively avoid malicious interference and protect user data privacy.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a message-driven two-stage frequency hopping method. Background Art

[0002] Frequency hopping (FH) technology offers outstanding performance in anti-interference, privacy protection, and extended transmission distance, playing a vital role in electronic countermeasures, the Internet of Things, and mobile communications. OFDM leverages the orthogonality between subchannels to prevent inter-carrier interference (ICI) in the presence of overlapping frequency bands, thereby improving bandwidth utilization and reducing transmission latency. Frequency-hopping OFDM technology utilizes OFDM modulation during FH transmission, retaining the high concealment and interference resistance of FH while reducing transmission latency. The concealment and interference resistance of traditional FH OFDM rely on the privacy of the frequency set and pseudo-random sequence. The cyclic prefix causes correlation peaks to appear at regular intervals during autocorrelation calculations of the OFDM signal, making it easy for attackers to analyze the frequency set. Pseudo-random sequences exhibit periodic characteristics, allowing attackers to obtain the pseudo-random sequence through continuous reception and analysis over a long period of time. This makes it difficult to effectively protect the privacy of legitimate users and the reliability of communications.

[0003] Therefore, it is an urgent problem for those skilled in the art to propose a message-driven two-stage frequency hopping method to solve the difficulties in the prior art. Summary of the Invention

[0004] In view of this, the present invention provides a message-driven two-stage frequency hopping method. Compared with the traditional pseudo-random sequence-based frequency hopping scheme, it makes it impossible for attackers to predict the communication frequency and obtain all data from the wireless channel. It can effectively avoid malicious interference and protect user data privacy.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A message-driven two-level frequency hopping method includes the following steps:

[0007] S1. Input the data to be sent D, perform RS-CC channel coding on the data to be sent D, and obtain the coded data D C ;

[0008] S2.D C Perform data segmentation to obtain the modulated data D M , subcarrier frequency hopping data D SC and RF frequency hopping data D RF ;

[0009] S3. Modulate the data D MThe serial input modulation module performs QAM modulation and the parallel output obtains the modulation symbol S M ;

[0010] S4. The pseudo-random sequence PN1 and the subcarrier frequency hopping data D SC Input scrambling module, output scrambled subcarrier frequency hopping data Will Input subcarrier frequency hopping position calculation module, output subcarrier position sequence A SC ;

[0011] S5. Each modulation symbol S M According to the subcarrier position sequence A SC Placed at the corresponding subcarrier position, all unplaced modulation symbols S M Data 0 is placed on all subcarriers, and then OFDM modulation is implemented using IFFT operation, and a cyclic prefix CP is added;

[0012] S6. The pseudo random sequence PN2 and the radio frequency hopping data D RF Input scrambling module, output scrambled RF frequency hopping data

[0013] S7. The transmitter transmits the scrambled RF frequency hopping data Move the DC subcarrier of the OFDM symbol to the final center frequency f c and send it to the receiver;

[0014] S8. The receiver simultaneously monitors the frequency set The signal energy in each frequency band in the frequency set is assuming that the frequency point where the effective signal is detected is in the frequency set The serial number in is k, and the estimated value of the scrambled RF frequency hopping data is obtained from k

[0015] S9. After descrambling, the final RF frequency hopping data estimate is obtained

[0016] S10 removes the cyclic prefix CP from the received signal and then performs FFT operation to achieve OFDM demodulation;

[0017] S11. Perform subcarrier monitoring. During each monitoring process, select the subcarrier with the highest signal power among the four subcarriers. The symbols carried by the four subcarriers with the highest signal power are modulation symbols. The subcarrier mapping data is hidden in the subcarrier sequence number. The modulation symbols and the corresponding subcarrier sequence numbers are recorded in the monitoring order. After N / 4 monitoring times, two sequences of length N / 4 are obtained, which are the modulation symbol sequence and the subcarrier position sequence

[0018] S12. By Get the decimal representation of the estimated value of the scrambled subcarrier frequency hopping data use Calculate the estimated value of the scrambled subcarrier frequency hopping data

[0019] S13. After descrambling, the final RF frequency hopping data estimate is obtained

[0020] S14. Modulate the symbol Demodulate and obtain the estimated value of the modulated data

[0021] S15. Combine them in sequence to get the estimated value of the coded data

[0022] S16.Yes Perform channel decoding to obtain the final output data

[0023] Optionally, the amount of data D to be sent input in S1 is as shown in formula (1):

[0024]

[0025] Among them, R is the coding efficiency of channel coding, N is the number of subcarriers of OFDM, L is the modulation order, and M is the number of frequencies in the frequency set.

[0026] Optionally, in S4, the pseudo-random sequence PN1 and the subcarrier frequency hopping data D SC Input scrambling module, output scrambled subcarrier frequency hopping data The calculation method is shown in formula (2):

[0027]

[0028] in, Represents a bitwise exclusive OR operation;

[0029] Will Input subcarrier frequency hopping position calculation module, output subcarrier position sequence A SC The calculation method is shown in formula (3):

[0030]

[0031] Here, bin2dec(a, b)=2×a+b, where a and b are both binary data.

[0032] Optionally, each modulation symbol S in S5M According to the subcarrier position sequence A SC Placed at the corresponding subcarrier position, the corresponding relationship is shown in equations (4) and (5):

[0033]

[0034]

[0035] Here, dec mod k represents the remainder obtained by dividing dec by k.

[0036] Optionally, in S6, the pseudo-random sequence PN2 and the radio frequency hopping data D RF Input scrambling module, output scrambled RF frequency hopping data The calculation method is shown in formula (6):

[0037]

[0038] Optionally, the transmitter in S7 can be configured to receive the scrambled RF frequency hopping data. Move the DC subcarrier of the OFDM symbol to the final center frequency f c Up, f c and The relationship between is shown in formula (7):

[0039]

[0040] in, Indicates the current frequency set The i-th frequency in

[0041] Optionally, the receiver in S8 monitors the frequency set The signal energy in each frequency band in the frequency set is assuming that the frequency point where the effective signal is detected is in the frequency set The serial number in is k, and the estimated value of the scrambled RF frequency hopping data is obtained from k As shown in formula (8):

[0042]

[0043] Among them, dec2bin(·) means converting a decimal number into a binary sequence.

[0044] Optionally, the final estimated value of the RF frequency hopping data obtained after descrambling in S9 As shown in formula (10):

[0045]

[0046] Optionally, subcarrier monitoring is performed in S11. During each monitoring process, the subcarrier with the highest signal power among the four subcarriers is selected. The symbols carried by the four subcarriers with the highest signal power are modulation symbols. The subcarrier mapping data is hidden in the subcarrier sequence number. The modulation symbols and the corresponding subcarrier sequence numbers are recorded in the monitoring order. After N / 4 monitoring times, two sequences with a length of N / 4 are obtained, which are the modulation symbol sequence and the subcarrier position sequence Then the subcarrier sequence number set S monitored for the i-th time is i As shown in formula (11):

[0047]

[0048] Optional, S12 by Get the decimal representation of the estimated value of the scrambled subcarrier frequency hopping data The calculation method is shown in formulas (12) and (13):

[0049]

[0050] use Calculate the estimated value of the scrambled subcarrier frequency hopping data The calculation method is as shown in formula (14) and (15):

[0051]

[0052] It can be seen from the above technical solution that compared with the prior art, the present invention provides a message-driven two-stage frequency hopping method, which has the following beneficial effects: the present invention does not transmit all data through the wireless channel, but hides part of the data in the frequency hopping sequence, and uses the unpredictability of the sent message at the subcarrier level and the radio frequency level to achieve true random frequency hopping. Compared with the traditional pseudo-random sequence-based frequency hopping scheme, it makes it impossible for attackers to predict the communication frequency or obtain all data from the wireless channel, which can effectively avoid malicious interference and protect user data privacy. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0054] Figure 1 This is a flow chart of a message-driven two-stage frequency hopping method provided by the present invention. DETAILED DESCRIPTION

[0055] 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 creative efforts are within the scope of protection of the present invention.

[0056] Reference Figure 1 As shown, the present invention discloses a two-stage frequency hopping method based on message driving, comprising the following steps:

[0057] S1. Input the data to be sent D, perform RS-CC channel coding on the data to be sent D, and obtain the coded data D C ;

[0058] S2.D C Perform data segmentation to obtain the modulated data D M , subcarrier frequency hopping data D SC and RF frequency hopping data D RF ;

[0059] S3. Modulate the data D M The serial input modulation module performs QAM modulation and the parallel output obtains the modulation symbol S M ;

[0060] S4. The pseudo-random sequence PN1 and the subcarrier frequency hopping data D SC Input scrambling module, output scrambled subcarrier frequency hopping data Will Input subcarrier frequency hopping position calculation module, output subcarrier position sequence A SC ;

[0061] S5. Each modulation symbol S M According to the subcarrier position sequence A SC Placed at the corresponding subcarrier position, all unplaced modulation symbols S M Data 0 is placed on all subcarriers, and then OFDM modulation is implemented using IFFT operation, and a cyclic prefix CP is added;

[0062] S6. The pseudo random sequence PN2 and the radio frequency hopping data D RF Input scrambling module, output scrambled RF frequency hopping data

[0063] S7. The transmitter transmits the scrambled RF frequency hopping data Move the DC subcarrier of the OFDM symbol to the final center frequency f c and send it to the receiver;

[0064] S8. The receiver simultaneously monitors the frequency set The signal energy in each frequency band in the frequency set is assuming that the frequency point where the effective signal is detected is in the frequency set The serial number in is k, and the estimated value of the scrambled RF frequency hopping data is obtained from k

[0065] S9. After descrambling, the final RF frequency hopping data estimate is obtained

[0066] S10 removes the cyclic prefix CP from the received signal and then performs FFT operation to achieve OFDM demodulation;

[0067] S11. Perform subcarrier monitoring. During each monitoring process, select the subcarrier with the highest signal power among the four subcarriers. The symbols carried by the four subcarriers with the highest signal power are modulation symbols. The subcarrier mapping data is hidden in the subcarrier sequence number. The modulation symbols and the corresponding subcarrier sequence numbers are recorded in the monitoring order. After N / 4 monitoring times, two sequences of length N / 4 are obtained, which are the modulation symbol sequence and the subcarrier position sequence

[0068] S12. By Get the decimal representation of the estimated value of the scrambled subcarrier frequency hopping data use Calculate the estimated value of the scrambled subcarrier frequency hopping data

[0069] S13. After descrambling, the final RF frequency hopping data estimate is obtained

[0070] S14. Modulate the symbol Demodulate and obtain the estimated value of the modulated data

[0071] S15. Combine them in sequence to get the estimated value of the coded data

[0072] S16.Yes Perform channel decoding to obtain the final output data

[0073] Furthermore, the amount of data D to be sent in S1 is as shown in formula (1):

[0074]

[0075] Among them, R is the coding efficiency of channel coding, N is the number of subcarriers of OFDM, L is the modulation order, and M is the number of frequencies in the frequency set.

[0076] Furthermore, in S4, the pseudo-random sequence PN1 and the subcarrier frequency hopping data D SC Input scrambling module, output scrambled subcarrier frequency hopping data The calculation method is shown in formula (2):

[0077]

[0078] in, Represents a bitwise exclusive OR operation;

[0079] Will Input subcarrier frequency hopping position calculation module, output subcarrier position sequence A SC The calculation method is shown in formula (3):

[0080]

[0081] Here, bin2dec(a, b)=2×a+b, where a and b are both binary data.

[0082] Furthermore, each modulation symbol S in S5 M According to the subcarrier position sequence A SC Placed at the corresponding subcarrier position, the corresponding relationship is shown in equations (4) and (5):

[0083]

[0084] Here, dec mod k represents the remainder obtained by dividing dec by k.

[0085] Furthermore, in S6, the pseudo random sequence PN2 and the radio frequency hopping data D RF Input scrambling module, output scrambled RF frequency hopping data The calculation method is shown in formula (6):

[0086]

[0087] Furthermore, the transmitter in S7 transmits the scrambled RF frequency hopping data Move the DC subcarrier of the OFDM symbol to the final center frequency f c Up, f c and The relationship between is shown in formula (7):

[0088]

[0089] in, represents the i-th frequency in the current frequency set F,

[0090] Furthermore, the receiver in S8 simultaneously monitors the frequency set The signal energy in each frequency band in the frequency set is assuming that the frequency point where the effective signal is detected is in the frequency set The serial number in is k, and the estimated value of the scrambled RF frequency hopping data is obtained from k As shown in formula (8):

[0091]

[0092] Among them, dec2bin(·) means converting a decimal number into a binary sequence.

[0093] Furthermore, the final RF frequency hopping data estimate obtained after descrambling in S9 is As shown in formula (10):

[0094]

[0095] Furthermore, subcarrier monitoring is performed in S11. During each monitoring process, the subcarrier with the highest signal power among the four subcarriers is selected. The symbols carried by the four subcarriers with the highest signal power are modulation symbols. The subcarrier mapping data is hidden in the subcarrier sequence number. The modulation symbols and the corresponding subcarrier sequence numbers are recorded in the monitoring order. After N / 4 monitorings are completed, two sequences with a length of N / 4 are obtained, which are the modulation symbol sequence and the subcarrier position sequence Then the subcarrier sequence number set S monitored for the i-th time is i As shown in formula (11):

[0096]

[0097] Furthermore, in S12 Get the decimal representation of the estimated value of the scrambled subcarrier frequency hopping data The calculation method is shown in formulas (12) and (13):

[0098]

[0099] use Calculate the estimated value of the scrambled subcarrier frequency hopping data The calculation method is as shown in formula (14) and (15):

[0100]

[0101] Specifically, after descrambling in S13, the final RF frequency hopping data estimation value is obtained. As shown in formula (16):

[0102]

[0103] In a specific embodiment, the following are included:

[0104] The physical layer processing flow at the transmitter is as follows: First, the sender's original data message is channel-coded. The coded data is then divided into three parts: modulation data, subcarrier hopping data, and RF hopping data. The modulation data is then QAM modulated to generate modulation symbols. The subcarrier hopping data is randomly scrambled, and the scrambled data is used to calculate the subcarrier hopping positions. The modulation symbols are mapped to the corresponding subcarrier positions based on the subcarrier hopping positions, with unmapped positions padded with zeros. Then, OFDM modulation is implemented using the IFFT algorithm. The RF hopping data is scrambled and the RF center frequency is calculated. The OFDM signal is shifted to the corresponding center frequency and transmitted. The signal then travels through the wireless channel to the receiver.

[0105] The physical layer processing flow at the receiving end is as follows: All frequency bands are monitored in the frequency set, and the RF frequency hopping sequence is calculated based on the channel of the received signal. After descrambling, the RF frequency hopping data is obtained. The received data is then subjected to an FFT transform to implement OFDM demodulation. Subcarrier monitoring is performed based on the signal power on the subcarrier to obtain the modulation symbols and scrambled subcarrier frequency hopping data. The modulation symbols are demodulated to obtain the modulation data. The scrambled subcarrier frequency hopping data is descrambled to obtain the subcarrier frequency hopping data. The modulation data, subcarrier frequency hopping data, and RF frequency hopping data are combined and channel decoding is performed to recover the original transmitted data. This method utilizes the unpredictability of the original message to achieve secondary random frequency hopping and hides part of the data within the secondary frequency hopping pattern, effectively resisting malicious interference and protecting user data privacy.

[0106] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0107] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A two-level frequency hopping method based on message driving, characterized in that: The following steps are involved: S1. Input the data to be sent D, perform RS-CC channel coding on the data to be sent D, and obtain the coded data D C ; S2.D C Perform data segmentation to obtain the modulated data D M , subcarrier frequency hopping data D SC and RF frequency hopping data D RF ; S3. Modulate the data D M The serial input modulation module performs QAM modulation and the parallel output obtains the modulation symbol S M ; S4. The pseudo-random sequence PN1 and the subcarrier frequency hopping data D SC Input scrambling module, output scrambled subcarrier frequency hopping data Will Input subcarrier frequency hopping position calculation module, output subcarrier position sequence A SC ; S5. Each modulation symbol S M According to the subcarrier position sequence A SC Placed at the corresponding subcarrier position, all unplaced modulation symbols S M Data 0 is placed on all subcarriers, and then OFDM modulation is implemented using IFFT operation, and a cyclic prefix CP is added; S6. The pseudo random sequence PN2 and the radio frequency hopping data D RF Input scrambling module, output scrambled RF frequency hopping data S7. The transmitter transmits the scrambled RF frequency hopping data Move the DC subcarrier of the OFDM symbol to the final center frequency f c and send it to the receiver; S8. The receiver simultaneously monitors the frequency set The signal energy in each frequency band in the frequency set is assuming that the frequency point where the effective signal is detected is in the frequency set The serial number in is k, and the estimated value of the scrambled RF frequency hopping data is obtained from k S9. After descrambling, the final RF frequency hopping data estimate is obtained S10 removes the cyclic prefix CP from the received signal and then performs FFT operation to achieve OFDM demodulation; S11. Perform subcarrier monitoring. During each monitoring process, select the subcarrier with the highest signal power among the four subcarriers. The symbols carried by the four subcarriers with the highest signal power are modulation symbols. The subcarrier mapping data is hidden in the subcarrier sequence number. The modulation symbols and the corresponding subcarrier sequence numbers are recorded in the monitoring order. After N / 4 monitoring times, two sequences of length N / 4 are obtained, which are the modulation symbol sequence and the subcarrier position sequence S12. By Get the decimal representation of the estimated value of the scrambled subcarrier frequency hopping data use Calculate the estimated value of the scrambled subcarrier frequency hopping data S13. After descrambling, the final RF frequency hopping data estimate is obtained S14. Modulate the symbol Demodulate and obtain the estimated value of the modulated data S15. Combine them in sequence to get the estimated value of the coded data S16.Yes Perform channel decoding to obtain the final output data 2. The message-driven two-level frequency hopping method according to claim 1, wherein: The amount of data D to be sent in S1 is shown in formula (1): Among them, R is the coding efficiency of channel coding, N is the number of subcarriers of OFDM, L is the modulation order, and M is the number of frequencies in the frequency set.

3. The message-driven two-level frequency hopping method according to claim 1, wherein: In S4, the pseudo random sequence PN1 and the subcarrier frequency hopping data D SC Input scrambling module, output scrambled subcarrier frequency hopping data The calculation method is shown in formula (2): in, Represents a bitwise exclusive OR operation; Will Input subcarrier frequency hopping position calculation module, output subcarrier position sequence A SC The calculation method is shown in formula (3): Wherein, bin2dec(a,b)=2×a+b, where a and b are both binary data.

4. The message-driven two-level frequency hopping method according to claim 1, wherein: Each modulation symbol S in S5 M According to the subcarrier position sequence A SC Placed at the corresponding subcarrier position, the corresponding relationship is shown in equations (4) and (5): Here, dec mod k represents the remainder obtained by dividing dec by k.

5. The message-driven two-level frequency hopping method according to claim 1, wherein: In S6, the pseudo random sequence PN2 and the radio frequency hopping data D RF Input scrambling module, output scrambled RF frequency hopping data The calculation method is shown in formula (6):

6. The message-driven two-level frequency hopping method according to claim 1, characterized in that: The transmitter in S7 is based on the scrambled RF frequency hopping data Move the DC subcarrier of the OFDM symbol to the final center frequency f c Up, f c and The relationship between is shown in formula (7): in, Indicates the current frequency set The i-th frequency in X=[X0,X1,…,X M-1 ].

7. The message-driven two-level frequency hopping method according to claim 1, characterized in that: The receiver in S8 monitors the frequency set simultaneously The signal energy in each frequency band in the frequency set is assuming that the frequency point where the effective signal is detected is in the frequency set The serial number in is k, and the estimated value of the scrambled RF frequency hopping data is obtained from k As shown in formula (8): Among them, dec2bin(·) means converting a decimal number into a binary sequence.

8. The message-driven two-level frequency hopping method according to claim 1, wherein: The final RF frequency hopping data estimate obtained after descrambling in S9 As shown in formula (10):

9. The message-driven two-level frequency hopping method according to claim 1, wherein: Subcarrier monitoring is performed in S11. During each monitoring process, the subcarrier with the highest signal power among the four subcarriers is selected. The symbols carried by the four subcarriers with the highest signal power are modulation symbols. The subcarrier mapping data is hidden in the subcarrier sequence number. The modulation symbols and the corresponding subcarrier sequence numbers are recorded in the monitoring order. After N / 4 monitorings are completed, two sequences with a length of N / 4 are obtained, which are the modulation symbol sequence and the subcarrier position sequence Then the subcarrier sequence number set S monitored for the i-th time is i As shown in formula (11):

10. The message-driven two-level frequency hopping method according to claim 1, characterized in that: S12 Get the decimal representation of the estimated value of the scrambled subcarrier frequency hopping data The calculation method is shown in formulas (12) and (13): use Calculate the estimated value of the scrambled subcarrier frequency hopping data The calculation method is as shown in formula (14) and (15):

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