An adaptive OFDM frequency hopping system and method based on FPGA

Abstract

The application discloses an FPGA-based adaptive OFDM frequency hopping system and method, and solves the problem of poor anti-interference ability of the current OFDM communication system, which leads to the decline of the system transmission information ability.The application combines the OFDM system with the frequency hopping system, and adds an adaptive control module; the receiver part of the system can detect the quality of the channel in real time, and can change the frequency hopping frequency points and the symbol modulation and demodulation modes of the transmitter and the receiver in real time according to the interference degree, so that the problem of the decline of the transmission information ability is effectively solved, the anti-interference ability of the OFDM communication system is improved, and the transmission reliability is improved.The application can be applied to the field of communication technology.

Description

Technical Field

[0001] This invention belongs to the field of communication technology, and specifically relates to an adaptive OFDM frequency hopping system and method based on FPGA. Background Technology

[0002] Adaptive OFDM frequency hopping system is a wireless communication system that combines orthogonal frequency division multiplexing (OFDM) and frequency hopping spread spectrum (FHSS) technologies, which can improve the anti-interference capability and spectrum utilization of communication in complex electromagnetic environments.

[0003] Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique that divides a high-speed data stream into multiple low-speed subcarriers and transmits them in parallel over orthogonal narrowband channels. It has advantages such as resistance to multipath fading, high-speed transmission, and efficient modulation. OFDM technology has been widely used in wireless standards such as LTE and WLAN.

[0004] Frequency hopping spread spectrum (FHSS) is a spread spectrum technique that hops between available narrowband frequencies within a specified wide channel for data transmission. It offers advantages such as resistance to narrowband interference, anti-interception, and low radiation. FHSS technology has been applied to wireless standards such as Bluetooth and ZigBee.

[0005] Field-Programmable Gate Arrays (FPGAs) are the product of the development of relatively mature programmable devices, following PAL, GAL, and CPLD. Their low latency, high connectivity, and parallel transmission characteristics make FPGAs one of the best platforms for realizing high-speed data transmission.

[0006] In conventional frequency-hopping communication systems, the frequency-hopping signal hops between pre-configured preset frequencies. If the frequency-hopping sub-channels are interfered with or experience frequency-selective fading, it will significantly impact system performance. Furthermore, when multiple frequency-hopping sub-channels are subjected to widespread interference, if the communication system still employs high-order modulation and demodulation methods, the reliability of data transmission cannot be guaranteed. This is especially true for OFDM systems, which have a large number of subcarriers and occupy relatively large bandwidth; the impact of such interference on system transmission performance will be even greater. Summary of the Invention

[0007] In view of the above problems, based on the research and exploration of the anti-interference transmission of OFDM technology, this invention proposes an adaptive OFDM frequency hopping system and method based on FPGA, which combines OFDM technology with frequency hopping technology and adds an adaptive optimization method to meet the transmission reliability of existing OFDM systems under different levels of interference.

[0008] In order to solve the technical problems existing in the prior art, the technical solution of the present invention is as follows:

[0009] An FPGA-based adaptive OFDM frequency hopping system, comprising a transmitter section and a receiver section:

[0010] The transmitter section includes a signal source module, an OFDM modulation module, a DAC, an up-conversion module, and a transmitter adaptive control module;

[0011] The source data is transmitted through the OFDM modulation module to the DAC module for digital-to-analog conversion, and then to the upconversion module to load the received analog signal onto the specified carrier frequency and transmit it into the channel through the antenna. The OFDM modulation module and the upconversion module are controlled by the transmitter adaptive control module, which enables the communication system to form a frequency hopping system and controls the current symbol modulation and demodulation mode and carrier frequency by combining the real-time channel signal-to-noise ratio data in the feedback channel.

[0012] The transmitter section includes a down-conversion module, an ADC, an OFDM demodulation module, and a receiver adaptive control module;

[0013] The downconversion module removes the carrier frequency from the signal received by the antenna to obtain an analog signal, which is then sent to the ADC module and the channel detection module. The ADC performs digital-to-analog conversion and sends the resulting digital signal to the OFDM demodulation module, which finally restores the original source data.

[0014] The OFDM demodulation module and down-conversion module are controlled by the receiver adaptive control module, which enables the communication system to form a frequency hopping system and controls the current symbol modulation and demodulation mode and carrier frequency in conjunction with the real-time channel signal-to-noise ratio data in the channel detection module.

[0015] Regarding the aforementioned receiver adaptive control module and transmitter sub-control module, these two modules can adaptively select the carrier frequency and symbol modulation scheme of the frequency hopping system based on the current channel status. When encountering narrowband channel interference, and the number of interfering channels is less than or equal to four, the adaptive control module will automatically skip the current frequency in the frequency hopping spectrum to avoid the interfered channels. When encountering a larger interference range, with as many as four interfering channels, the adaptive control module will reduce the modulation order to improve communication reliability. Conversely, if the current channel quality is good, the adaptive control module will attempt to increase the modulation order to increase the transmission rate.

[0016] Preferably, the OFDM modulation module includes modules for scrambling, convolutional coding, interleaving, symbol modulation, pilot insertion, IFFT, cyclic prefix and windowing;

[0017] Preferably, the OFDM demodulation module includes modules for channel estimation, synchronization, cyclic prefix removal, FFT, symbol demodulation, deinterleaving, Viterbi decoding, and descrambling.

[0018] Preferably, the symbol modulation module has four symbol modulation methods: BPSK, QPSK, 16QAM, and 64QAM.

[0019] Preferably, the symbol demodulation module has four symbol demodulation modes: BPSK, QPSK, 16QAM, and 64QAM.

[0020] Preferably, the FPGA communicates with the DAC, ADC, upconversion module, and downconversion module via an FMC connection.

[0021] Preferably, the transmitter adaptive control module and the receiver adaptive control module further include a control module, a frequency hopping pattern generator module, a symbol modulation configuration module, and a frequency hopping carrier center frequency configuration module.

[0022] Preferably, the FPGA communicates with the DAC, ADC, upconversion module, and downconversion module via an FMC connection.

[0023] Preferably, the frequency hopping carrier center frequency point configuration module uses the SPI protocol to configure the up-conversion module and the down-conversion module.

[0024] Preferably, the frequency hopping carrier center frequency configuration module has 8 preset carrier center frequency configuration information built in.

[0025] This invention also discloses an FPGA-based adaptive OFDM frequency hopping method, which includes at least the following steps:

[0026] Step S1: The source module sends the initial user-side data information to the OFDM modulation module;

[0027] Step S2: The OFDM modulation module modulates according to the initial symbol modulation mode, and the modulated initial OFDM baseband signal is sent to the DAC;

[0028] Step S3: The DAC converts the received initial OFDM baseband signal into an analog signal and sends it to the upconversion module;

[0029] Step S4: The transmitter-side frequency hopping pattern generator selects the initial frequency hopping carrier information according to the initial frequency hopping pattern and sends the frequency hopping carrier information to the frequency hopping carrier center frequency configuration module. The frequency hopping carrier center frequency configuration module transmits the corresponding frequency hopping carrier center frequency configuration information to the upconversion module according to the received frequency hopping carrier information, and sets the carrier frequency of the upconversion module to the initial frequency.

[0030] Step S5: The upconversion module transmits the analog information from the DAC at the initial frequency;

[0031] Step S6: The receiver-side frequency hopping pattern generator selects the initial frequency hopping carrier information according to the initial frequency hopping pattern, which is the same as the transmitter-side process. Finally, the receiver-side frequency hopping carrier center frequency configuration module generates the corresponding frequency hopping carrier center frequency configuration information and transmits it to the down-conversion module, setting the carrier frequency of the down-conversion module to the initial frequency.

[0032] Step S7: The receiver downconversion module receives and removes the carrier according to the initial frequency, and sends the resulting analog signal to the ADC;

[0033] Step S8: The ADC converts the received analog signal into a digital signal and sends the received digital signal to the OFDM demodulation module and the channel detection module;

[0034] Step S9: The channel detection module calculates the real-time channel signal-to-noise ratio data of the current channel and sends it to the control module in the receiver adaptive control module;

[0035] Step S10: The OFDM demodulation module demodulates the data according to the initial symbol modulation mode and restores the source-side data;

[0036] Step S11: The control module in the receiver adaptive control module synchronizes the timing of the receiver side with that of the transmitter based on the received signal, and determines whether the carrier frequency needs to be skipped in the frequency hopping pattern according to the preset threshold based on the real-time channel signal-to-noise ratio data and the preset threshold. It outputs the frequency hopping pattern control signal to the frequency hopping pattern generator module. If the preset number of carrier frequencies have been skipped, it outputs the symbol modulation step-up / down signal to the symbol modulation configuration module.

[0037] Step S12: The frequency hopping pattern generator module outputs the frequency hopping carrier information to be received next according to the received frequency hopping pattern control signaling. If the signaling requires skipping certain carrier frequencies, when the frequency hopping pattern switches to that frequency, it will automatically skip it, switch to the subsequent carrier frequency, and output the frequency hopping carrier information. The frequency hopping carrier center frequency configuration module sends the frequency hopping carrier center frequency configuration information to the downconversion module according to the received frequency hopping carrier information and the preset carrier frequency configuration, thus completing the carrier frequency setting.

[0038] Step S13: The symbol modulation configuration module selects a suitable symbol modulation mode for the next reception based on the received symbol modulation step-up / down signaling, and sends symbol modulation configuration signaling to the symbol demodulation module in the OFDM demodulation module to complete the symbol demodulation mode configuration for the next reception.

[0039] Step S14: After receiving the real-time channel signal-to-noise ratio data through the feedback channel, the transmitter adaptive control module performs similar operations to steps S11, S12, and S13 to complete the carrier frequency setting of the upconversion module and the symbol modulation mode setting for the next transmission.

[0040] Step S15: Perform subsequent data transmission, and repeat the process from S1 to S14.

[0041] As a further improvement, in step S11, the receiver adaptive control module can adaptively select the carrier frequency and symbol modulation scheme of the frequency hopping system according to the current channel state. When encountering narrowband channel interference, and the range of interfering channels is less than or equal to 4, the adaptive control module will automatically skip the current frequency in the frequency hopping spectrum to avoid the interfered channel. When encountering a large range of channel interference, and the number of interfering channels has reached 4, the adaptive control module will reduce the modulation order to improve communication reliability. Conversely, if the current channel quality is good, the adaptive control module will try to increase the modulation order to increase the transmission rate.

[0042] As a further improvement, the specific control methods for the receiver adaptive control module and the transmitter adaptive control module include the following steps:

[0043] Step D1: The control module determines the current channel quality based on the received channel signal-to-noise ratio data. If the channel quality is good, proceed to step D2; otherwise, proceed to step D3.

[0044] Step D2: The control module determines whether the current modulation scheme is 64QAM. If yes, the carrier frequency and modulation scheme remain unchanged in the next stage; otherwise, the carrier frequency remains unchanged in the next stage, but the modulation scheme is upgraded.

[0045] Step D3: Determine if the number of skipped frequency points has reached 3. If yes, proceed to step D4; otherwise, proceed to step D5.

[0046] Step D4: Determine whether the current modulation scheme is BPSK. If yes, the carrier frequency remains unchanged and the modulation scheme is downgraded in the next stage; otherwise, the carrier frequency and modulation scheme remain unchanged in the next stage.

[0047] Step D5: In the next stage, if the frequency hopping pattern encounters the current carrier frequency, it is skipped, and the modulation method remains unchanged;

[0048] Step D6: The control module outputs corresponding control signaling based on the carrier frequency and modulation scheme selected in D1-D5 for the next stage.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] The receiver section of this invention can detect channel quality in real time. For small-scale channel interference, it can adaptively change the frequency-hopping carrier frequency to avoid interfering channels and increase transmission stability. For large-scale channel interference, it can adaptively change the symbol modulation and demodulation method in OFDM to increase transmission reliability. By combining these two methods, the problem of reduced information transmission capability under channel interference can be effectively solved, thereby improving the anti-interference capability of the frequency-hopping system. Attached Figure Description

[0051] Figure 1 This is a block diagram of the conventional OFDM communication system in the FPGA-based adaptive OFDM frequency hopping system of the present invention.

[0052] Figure 2 This is a block diagram of the overall structure of the FPGA-based adaptive OFDM frequency hopping system of the present invention.

[0053] Figure 3 This is a block diagram of the transmitter structure in the FPGA-based adaptive OFDM frequency hopping system of the present invention;

[0054] Figure 4 This is a block diagram of the receiver structure in the FPGA-based adaptive OFDM frequency hopping system of the present invention;

[0055] Figure 5 This is a flowchart illustrating the workflow of the adaptive control module in the transmitter and receiver of the FPGA-based adaptive OFDM frequency hopping system of this invention. Detailed Implementation

[0056] The present invention will be further described in detail below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solutions of the present invention that do not depart from the spirit and scope of the technical solutions of the present invention should be covered within the protection scope of the present invention.

[0057] First, the composition structure of a conventional OFDM system in the FPGA-based adaptive OFDM frequency hopping system of this invention is introduced. The transmitter source data is scrambled, convolutionally encoded, interleaved, and symbol modulated. Pilot signals are inserted, followed by IFFT. Then, a cyclic prefix is ​​added to the data, and windowing is applied. The modulated baseband signal is converted from digital to analog by a DAC and sent to the upconversion module and transmitted to the channel through the antenna. The receiver works in the opposite way. The analog signal received from the channel by the downconversion module is passed to the ADC for analog-to-digital conversion. After the channel estimation and synchronization modules in the OFDM demodulation module correct the signal amplitude and phase information, the signal undergoes cyclic prefix removal, FFT, symbol demodulation, deinterleaving, Viterbi decoding, and descrambling to restore the original data.

[0058] This invention discloses an FPGA-based adaptive OFDM frequency hopping system, comprising a transmitter section and a receiver section:

[0059] The transmitter section includes a signal source module, an OFDM modulation module, a DAC, an up-conversion module, and a transmitter adaptive control module. The transmitter adaptive control module further includes a control module, a frequency hopping pattern generator module, a symbol modulation configuration module, and a frequency hopping carrier center frequency configuration module.

[0060] The source module is used to generate data information and send the data information to the OFDM modulation module;

[0061] The OFDM modulation module is used to modulate the received data information into an OFDM baseband signal. The OFDM modulation module includes a symbol modulation module, which incorporates four symbol modulation modes: BPSK, QPSK, 16QAM, and 64QAM. Different symbol modulation modes can be selected according to the symbol modulation configuration signaling. The data signal modulated by the OFDM modulation module is then sent to the DAC.

[0062] The DAC converts digital signals into analog signals and sends them to the upconversion module;

[0063] The upconversion module loads the received analog signal onto the specified carrier frequency and transmits it through the antenna;

[0064] The control module in the transmitter adaptive control module parses the data received from the feedback channel to determine the symbol modulation configuration and frequency hopping pattern configuration that need to be set for the next data transmission. It then sends the symbol modulation step-up / down control signaling to the symbol modulation configuration module and the frequency hopping pattern control signaling to the frequency hopping pattern generator module.

[0065] The symbol modulation configuration module outputs the corresponding symbol modulation configuration signaling based on the received symbol modulation step-up / down control signaling and sends it to the symbol modulation module in the OFDM encoding module.

[0066] The frequency hopping pattern generator module has a built-in preset pseudo-random frequency hopping pattern, which is also controlled by the received frequency hopping pattern control signaling. Based on the frequency hopping pattern and following certain timing rules, this module can send the required frequency hopping carrier information to the frequency hopping carrier center frequency configuration module each time data is transmitted.

[0067] The frequency hopping carrier center frequency point configuration module transmits the corresponding frequency hopping carrier center frequency point configuration information to the upconversion module based on the received frequency hopping carrier information, thereby completing the configuration of the upconversion module.

[0068] The receiver section includes a down-conversion module, an ADC, a channel detection module, an OFDM demodulation module, and a receiver adaptive control module. The receiver adaptive control module includes a frequency hopping pattern generator module, a control module, a symbol modulation configuration module, and a frequency hopping carrier center frequency configuration module.

[0069] The downconversion module removes the carrier frequency from the signal received by the antenna to obtain an analog signal;

[0070] The ADC converts the received analog signal into a digital signal and sends it to the OFDM demodulation module and the channel detection module.

[0071] The channel detection module can calculate the real-time channel signal-to-noise ratio data reflected by the currently received data, and send the real-time signal-to-noise ratio data to the receiver adaptive control module, and also send it to the transmitter adaptive control module through the feedback channel;

[0072] The OFDM demodulation module demodulates the received OFDM baseband signal to recover the original transmitted data. It includes a symbol demodulation module with four built-in demodulation modes: BPSK, QPSK, 16QAM, and 64QAM. Different demodulation modes can be selected based on the symbol demodulation configuration signaling. The demodulated data is also sent to the receiver's adaptive control module for frequency hopping timing synchronization between the receiver and transmitter.

[0073] The receiver adaptive control module has a preset timing information corresponding to the control module in the transmitter adaptive control module. This module synchronizes the timing with the transmitter adaptive control module based on the received data, and determines the symbol modulation configuration and frequency hopping pattern configuration to be set for the next data transmission based on the real-time channel signal-to-noise ratio data. It then sends the symbol modulation step-up / down control signaling to the symbol modulation configuration module and the frequency hopping pattern control signaling to the frequency hopping pattern generator module.

[0074] The symbol modulation configuration module on the receiver side is exactly the same as the module on the transmitter side. Based on the received symbol modulation step-up / down control signaling, it outputs the corresponding symbol modulation configuration signaling and sends it to the symbol modulation module in the OFDM decoding module.

[0075] The frequency hopping pattern generator module on the receiver side is exactly the same as the module on the transmitter side, with a built-in preset pseudo-random frequency hopping pattern. This pseudo-random frequency hopping pattern is also controlled by the received frequency hopping pattern control signaling. This module can send the required frequency hopping carrier information to the frequency hopping carrier center frequency configuration module before each data reception according to a certain timing rule based on the frequency hopping pattern.

[0076] The frequency hopping carrier center frequency configuration module on the receiver side is exactly the same as the module on the transmitter side. Based on the received frequency hopping carrier information, it transmits the corresponding frequency hopping carrier center frequency configuration information to the downconversion module to complete the configuration of the downconversion module.

[0077] According to the above-mentioned FPGA-based adaptive OFDM frequency hopping method, its specific working steps are as follows:

[0078] Step S1: The source module sends the initial user-side data information to the OFDM modulation module;

[0079] Step S2: The OFDM modulation module modulates according to the initial symbol modulation mode, and the modulated initial OFDM baseband signal is sent to the DAC;

[0080] Step S3: The DAC converts the received initial OFDM baseband signal into an analog signal and sends it to the upconversion module;

[0081] Step S4: The transmitter-side frequency hopping pattern generator selects the initial frequency hopping carrier information according to the initial frequency hopping pattern and sends the frequency hopping carrier information to the frequency hopping carrier center frequency configuration module. The frequency hopping carrier center frequency configuration module transmits the corresponding frequency hopping carrier center frequency configuration information to the upconversion module according to the received frequency hopping carrier information, and sets the carrier frequency of the upconversion module to the initial frequency.

[0082] Step S5: The upconversion module transmits the analog information from the DAC at the initial frequency;

[0083] Step S6: The receiver-side frequency hopping pattern generator selects the initial frequency hopping carrier information according to the initial frequency hopping pattern, which is the same as the transmitter-side process. Finally, the receiver-side frequency hopping carrier center frequency configuration module generates the corresponding frequency hopping carrier center frequency configuration information and transmits it to the down-conversion module, setting the carrier frequency of the down-conversion module to the initial frequency.

[0084] Step S7: The receiver downconversion module receives and removes the carrier according to the initial frequency, and sends the resulting analog signal to the ADC;

[0085] Step S8: The ADC converts the received analog signal into a digital signal and sends the received digital signal to the OFDM demodulation module and the channel detection module;

[0086] Step S9: The channel detection module calculates the real-time channel signal-to-noise ratio data of the current channel and sends it to the control module in the receiver adaptive control module;

[0087] Step S10: The OFDM demodulation module demodulates the data according to the initial symbol modulation mode and restores the source-side data;

[0088] Step S11: The control module in the receiver adaptive control module synchronizes the timing of the receiver side with that of the transmitter based on the received signal. Combined with real-time channel signal-to-noise ratio data, it determines whether the carrier frequency needs to be skipped in the frequency hopping pattern according to a preset threshold, and outputs a frequency hopping pattern control signal to the frequency hopping pattern generator module. If a preset number of carrier frequencies have already been skipped, it outputs a symbol modulation step-up / down signal to the symbol modulation configuration module.

[0089] Step S12: The frequency hopping pattern generator module outputs the frequency hopping carrier information to be received next according to the received frequency hopping pattern control signaling. If the signaling requires skipping certain carrier frequencies, when the frequency hopping pattern switches to that frequency, it will automatically skip it, switch to the subsequent carrier frequency, and output the frequency hopping carrier information. The frequency hopping carrier center frequency configuration module sends the frequency hopping carrier center frequency configuration information to the downconversion module according to the received frequency hopping carrier information and the preset carrier frequency configuration, thus completing the carrier frequency setting.

[0090] Step S13: The symbol modulation configuration module selects a suitable symbol modulation mode for the next reception based on the received symbol modulation step-up / down signaling, and sends symbol modulation configuration signaling to the symbol demodulation module in the OFDM demodulation module to complete the symbol demodulation mode configuration for the next reception.

[0091] Step S14: After receiving the real-time channel signal-to-noise ratio data through the feedback channel, the transmitter adaptive control module performs similar operations to steps S11, S12, and S13 to complete the carrier frequency setting of the upconversion module and the symbol modulation mode setting for the next transmission.

[0092] Step S15: Perform the second and subsequent data transmissions, repeating the process from S1 to S14.

[0093] Regarding the receiver adaptive control module in step S11 above, this module can adaptively select the carrier frequency and symbol modulation scheme of the frequency hopping system based on the current channel state. When encountering narrowband channel interference, and the range of interfering channels is less than or equal to 4, the adaptive control module will automatically skip the current frequency in the frequency hopping spectrum to avoid the interfered channels. When encountering a large range of channel interference, with as many as 4 interfering channels, the adaptive control module will reduce the modulation order to improve communication reliability. Conversely, if the current channel quality is good, the adaptive control module will attempt to increase the modulation order to increase the transmission rate. Specific control methods are as follows: Figure 3 The steps described:

[0094] Step D1: The control module determines the current channel quality based on the received channel signal-to-noise ratio data. If the channel quality is good, proceed to step D2; otherwise, proceed to step D3.

[0095] Step D2: The control module determines whether the current modulation scheme is 64QAM. If yes, the carrier frequency and modulation scheme remain unchanged in the next stage; otherwise, the carrier frequency remains unchanged in the next stage, but the modulation scheme is upgraded.

[0096] Step D3: Determine if the number of skipped frequency points has reached 3. If yes, proceed to step D4; otherwise, proceed to step D5.

[0097] Step D4: Determine whether the current modulation scheme is BPSK. If yes, the carrier frequency remains unchanged and the modulation scheme is downgraded in the next stage; otherwise, the carrier frequency and modulation scheme remain unchanged in the next stage.

[0098] Step D5: In the next stage, if the frequency hopping pattern encounters the current carrier frequency, it is skipped, and the modulation method remains unchanged;

[0099] Step D6: The control module outputs corresponding control signaling based on the carrier frequency and modulation scheme selected in D1-D5 for the next stage;

[0100] The specific control method for the transmitter adaptive control module in step S14 is the same as that in steps D1-D6.

[0101] The beneficial effects of this invention are as follows: The FPGA-based adaptive OFDM frequency hopping system of this invention allows the receiver section to perform real-time channel quality detection. For small-scale channel interference, it can adaptively change the frequency hopping carrier frequency to avoid interfering channels and increase transmission stability. For large-scale channel interference, it can adaptively change the symbol modulation and demodulation method in OFDM to increase transmission reliability. By combining these two methods, the problem of reduced information transmission capability under channel interference can be effectively solved, thereby improving the anti-interference capability of the frequency hopping system.

[0102] The above description is merely a preferred embodiment of the present invention. Any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments without departing from the scope of the present invention and based on the technical essence of the present invention shall still fall within the scope of the present invention.

Claims

1. An adaptive OFDM frequency hopping method based on FPGA, characterized in that, At least the following steps are included: Step S1: The source module sends the initial user-side data information to the OFDM modulation module; Step S2: The OFDM modulation module modulates according to the initial symbol modulation mode, and the modulated initial OFDM baseband signal is sent to the DAC; Step S3: The DAC converts the received initial OFDM baseband signal into an analog signal and sends it to the upconversion module; Step S4: The transmitter-side frequency hopping pattern generator selects the initial frequency hopping carrier information according to the initial frequency hopping pattern and sends the frequency hopping carrier information to the frequency hopping carrier center frequency configuration module. The frequency hopping carrier center frequency configuration module transmits the corresponding frequency hopping carrier center frequency configuration information to the upconversion module according to the received frequency hopping carrier information, and sets the carrier frequency of the upconversion module to the initial frequency. Step S5: The upconversion module transmits the analog information from the DAC at the initial frequency; Step S6: The receiver-side frequency hopping pattern generator selects the initial frequency hopping carrier information according to the initial frequency hopping pattern, which is the same as the transmitter-side process. Finally, the receiver-side frequency hopping carrier center frequency configuration module generates the corresponding frequency hopping carrier center frequency configuration information and transmits it to the down-conversion module, setting the carrier frequency of the down-conversion module to the initial frequency. Step S7: The receiver downconversion module receives and removes the carrier according to the initial frequency, and sends the resulting analog signal to the ADC; Step S8: The ADC converts the received analog signal into a digital signal and sends the received digital signal to the OFDM demodulation module and the channel detection module; Step S9: The channel detection module calculates the real-time channel signal-to-noise ratio data of the current channel and sends it to the control module in the receiver adaptive control module; Step S10: The OFDM demodulation module demodulates the data according to the initial symbol modulation mode and restores the source-side data; Step S11: The control module in the receiver adaptive control module synchronizes the timing of the receiver side with that of the transmitter based on the received signal, and determines whether the carrier frequency needs to be skipped in the frequency hopping pattern according to the preset threshold based on the real-time channel signal-to-noise ratio data and the preset threshold. It outputs the frequency hopping pattern control signal to the receiver frequency hopping pattern generator module. If the preset number of carrier frequencies have been skipped, it outputs the symbol modulation step-up / down signal to the symbol modulation configuration module of the receiver. Step S12: The receiver frequency hopping pattern generator module outputs the frequency hopping carrier information to be received next according to the received frequency hopping pattern control signal. If the signal requires skipping certain carrier frequencies, when the frequency hopping pattern switches to that frequency, it will automatically skip it, switch to the subsequent carrier frequency, and output the frequency hopping carrier information. The receiver frequency hopping carrier center frequency configuration module sends the frequency hopping carrier center frequency configuration information to the downconversion module according to the received frequency hopping carrier information and the preset carrier frequency configuration, thus completing the carrier frequency setting. Step S13: The symbol modulation configuration module of the receiver selects a suitable symbol modulation mode for the next reception based on the received symbol modulation step-up / down signaling, and sends the symbol modulation configuration signaling to the symbol demodulation module in the OFDM demodulation module to complete the symbol demodulation mode configuration for the next reception. Step S14: The transmitter determines whether the carrier frequency needs to be skipped in the frequency hopping pattern based on the real-time channel signal-to-noise ratio data received from the feedback channel and a preset threshold. It outputs a frequency hopping pattern control signal to the transmitter frequency hopping pattern generator module. If a preset number of carrier frequencies have been skipped, it outputs a symbol modulation step-up / down signal to the transmitter symbol modulation configuration module. Step S15: The transmitter frequency hopping pattern generator module outputs the frequency hopping carrier information for the next transmission based on the received frequency hopping pattern control signal. If the signal requires skipping certain carrier frequencies, it will automatically skip them when the frequency hopping pattern switches to that frequency, switch to the subsequent carrier frequency, and output the frequency hopping carrier information. The transmitter frequency hopping carrier center frequency configuration module sends the frequency hopping carrier center frequency configuration information to the upconverter module based on the received frequency hopping carrier information and the preset carrier frequency configuration, thus completing the carrier frequency setting. Step S16: The symbol modulation configuration module of the transmitter selects a suitable symbol modulation mode for the next transmission based on the received symbol modulation step-up / down signaling, and sends the symbol modulation configuration signaling to the symbol modulation module in the OFDM modulation module to complete the symbol modulation mode configuration for the next transmission. Step S17: Perform subsequent data transmission, and repeat the process from S1 to S16. In step S11, the receiver adaptive control module can adaptively select the carrier frequency and symbol modulation scheme of the frequency hopping system according to the current channel state. When encountering narrowband channel interference, and the number of interfering channels is less than or equal to 4, the adaptive control module will automatically skip the current frequency in the frequency hopping spectrum to avoid the interfered channels. When there are more than 4 interfering channels, the adaptive control module will reduce the modulation order to improve communication reliability. Conversely, if the current channel quality is good, the adaptive control module will try to increase the modulation order to increase the transmission rate.

2. The FPGA-based adaptive OFDM frequency hopping method according to claim 1, characterized in that, The specific control methods for the receiver adaptive control module and the transmitter adaptive control module include the following steps: Step D1: The control module determines the current channel quality based on the received channel signal-to-noise ratio data. If the channel quality is good, proceed to step D2; otherwise, proceed to step D3. Step D2: The control module determines whether the current modulation scheme is 64QAM. If yes, the carrier frequency and modulation scheme remain unchanged in the next stage; otherwise, the carrier frequency remains unchanged in the next stage, but the modulation scheme is upgraded. Step D3: Determine if the number of skipped frequency points has reached 3. If yes, proceed to step D4; otherwise, proceed to step D5. Step D4: Determine whether the current modulation scheme is BPSK. If yes, the carrier frequency remains unchanged and the modulation scheme is downgraded in the next stage; otherwise, the carrier frequency and modulation scheme remain unchanged in the next stage. Step D5: In the next stage, if the frequency hopping pattern encounters the current carrier frequency, it is skipped, and the modulation method remains unchanged; Step D6: The control module outputs corresponding control signaling based on the carrier frequency and modulation scheme selected in D1-D5 for the next stage.

3. The FPGA-based adaptive OFDM frequency hopping system according to claim 1 or 2, characterized in that, The system consists of a transmitter and a receiver: The transmitter section includes a signal source module, an OFDM modulation module, a DAC, an up-conversion module, and a transmitter adaptive control module; The source data is processed by the OFDM modulation module, sent to the DAC module for digital-to-analog conversion, and then sent to the upconversion module to load the received analog signal onto the specified carrier frequency and transmit it into the channel through the antenna. The OFDM modulation module and the upconversion module are controlled by the transmitter adaptive control module, which makes the communication system a frequency hopping system and controls the current symbol modulation and demodulation mode and carrier frequency by combining the real-time channel signal-to-noise ratio data in the feedback channel. The receiver section includes a down-conversion module, an ADC, an OFDM demodulation module, and a receiver adaptive control module; The downconversion module removes the carrier frequency from the signal received by the antenna to obtain an analog signal, which is then sent to the ADC module and the channel detection module. The ADC performs digital-to-analog conversion and sends the resulting digital signal to the OFDM demodulation module, which finally restores the original source data. The OFDM demodulation module and down-conversion module are controlled by the receiver adaptive control module, which makes the communication system a frequency hopping system. Combined with the real-time channel signal-to-noise ratio data in the channel detection module, the current symbol modulation and demodulation mode and carrier frequency are controlled.

4. The FPGA-based adaptive OFDM frequency hopping system according to claim 3, characterized in that, The OFDM modulation module includes at least scrambling, convolutional coding, interleaving, symbol modulation, pilot insertion, IFFT, cyclic prefix and windowing modules; The OFDM demodulation module includes at least channel estimation, synchronization, cyclic prefix removal, FFT, symbol demodulation, deinterleaving, Viterbi decoding, and descrambling modules.

5. The FPGA-based adaptive OFDM frequency hopping system according to claim 4, characterized in that, The symbol modulation module has four symbol modulation methods: BPSK, QPSK, 16QAM, and 64QAM; the symbol demodulation module has four symbol demodulation methods: BPSK, QPSK, 16QAM, and 64QAM.

6. The FPGA-based adaptive OFDM frequency hopping system according to claim 4, characterized in that, The FPGA communicates with the DAC, ADC, upconverter module, and downconverter module via FMC.

7. The FPGA-based adaptive OFDM frequency hopping system according to claim 3, characterized in that, The transmitter adaptive control module and receiver adaptive control module include a control module, a frequency hopping pattern generator module, a symbol modulation configuration module, and a frequency hopping carrier center frequency configuration module.

8. The FPGA-based adaptive OFDM frequency hopping system according to claim 3, characterized in that, The frequency hopping carrier center frequency point configuration module uses the SPI protocol to configure the up-conversion module and the down-conversion module.

9. The FPGA-based adaptive OFDM frequency hopping system according to claim 8, characterized in that, The frequency hopping carrier center frequency configuration module has 8 preset carrier center frequency configuration information built in.

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