Anti-interference wireless communication system

Abstract

The invention relates to the technical field of communication systems, and discloses an anti-interference wireless communication system, which comprises the following modules: a radio frequency front-end processing module used for setting receiving gain of a radio frequency transceiver, a baseband signal preprocessing module used for filtering and amplifying signals, a high-speed sampling and baseband processing module, and a signal processing module. The sampling module is used for sampling through a high-speed ADC, the selective frequency hopping module is used for dividing a working frequency band into fixed channels and numbering the fixed channels, and the variable channel bandwidth module is used for adjusting the channel bandwidth when the SNR is low and the packet loss number is high. Through the radio frequency front-end processing module and the baseband signal preprocessing module, adjacent channel interference can be suppressed, useful signals are ensured to obtain enough gain, the signal-to-noise ratio is improved, the signals are enabled to reach an optimal state before entering the high-speed sampling and baseband processing module, and thus the reliability of the signals is improved; the unmanned aerial vehicle is ensured to accurately receive and process control instructions and data and stably execute tasks.

Description

Technical Field

[0001] The present invention relates to the technical field of communication systems, and in particular to an anti-interference wireless communication system. Background Art

[0002] Wireless communication system is a communication system that uses the propagation of electromagnetic waves in free space to achieve information transmission. It is free from the constraints of cables and has a high degree of flexibility and convenience. In this system, information is first converted into a signal form suitable for transmission through source coding, and then loaded onto a high-frequency carrier through modulation and transmitted into space by an antenna. After the receiving antenna captures the electromagnetic wave, it is demodulated and decoded to restore the original information. Wireless communication systems are widely used, covering mobile phone communications, allowing people to communicate anytime and anywhere; wireless local area networks, achieving high-speed indoor Internet access; and satellite communications, providing communication services for remote areas or at sea.

[0003] In existing drone technologies, drones are mainly remotely sensed and controlled through 802.11-based technology and 4G-based technology, thereby ensuring the stability of drone long-distance flight.

[0004] However, in actual use, these two types of technologies did not consider the need for long-distance reliable communication in complex interference environments during the standard definition stage. Therefore, when there is signal interference between the remote sensing equipment and the drone or the distance is far, the wireless communication between the two will be at risk of interference, causing the drone to lose control and create a safety hazard. In view of this, we propose an anti-interference wireless communication system. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides an anti-interference wireless communication system, which solves the problem that the wireless links used for drones at this stage generally adopt 802.11-based technology and 4G-based technology. These two types of technologies did not consider the need for long-distance reliable communication in complex interference environments during the standard definition stage.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: an anti-interference wireless communication system, comprising the following modules:

[0007] The RF front-end processing module is used to set the RF transceiver receiving gain and control the ADC to be in an unsaturated state. After the processing is completed, the signal is transmitted to the baseband signal pre-processing module;

[0008] The baseband signal preprocessing module includes an independent baseband signal low-pass filter and AGC circuit, which filters and amplifies the signal before transmitting it to the high-speed sampling and baseband processing module;

[0009] High-speed sampling and baseband processing module, used for sampling through high-speed ADC and performing baseband processing using FIR filter;

[0010] Selective frequency hopping module, used to divide the working frequency band into fixed channels and number them, and select the optimal channel according to the channel RSSI situation;

[0011] Variable channel bandwidth module, used to adjust the channel bandwidth when SNR is low and packet loss is high.

[0012] Preferably, in the RF front-end processing module, a suitable value of the RF transceiver receiving gain is dynamically adjusted based on a saturation threshold of an ADC and an actual received signal strength monitored in real time.

[0013] Preferably, the RF transceiver has an automatic gain adjustment circuit, which can monitor the received signal strength in real time and compare it with the saturation threshold of the ADC, and automatically adjust the gain of the RF transceiver according to the comparison result to ensure that the ADC always operates in an unsaturated state.

[0014] Preferably, the independent baseband signal low-pass filter in the baseband signal preprocessing module adopts a reconfigurable filter structure, which can flexibly configure the bandwidth according to the control signal sent by the baseband. The reconfigurable filter structure includes multiple filter branches with different cutoff frequencies, and the switch array is controlled by the baseband control signal to select different filter branch combinations.

[0015] Preferably, the AGC circuit adopts a multi-stage gain control structure to automatically select a suitable gain multiple according to the input signal strength to achieve accurate amplification of the signal. The multi-stage gain control structure includes at least three stages of gain amplifiers, and the gain multiple of each stage of the gain amplifier can be adjusted according to preset rules.

[0016] Preferably, in the high-speed sampling and baseband processing module, the high-speed ADC adopts a pipeline sampling structure, and the pipeline sampling structure is composed of multiple sampling cascades, each sampling stage partially samples and processes the input signal, and sampling is achieved in a cascade manner.

[0017] Preferably, the baseband processing unit adopts a distributed algorithm to implement the FIR filter, completes the filtering operation through a lookup table and adder operation, improves the filtering efficiency and hardware resource utilization, the lookup table is pre-calculated and stored according to the coefficients of the FIR filter, and the adder operation is based on a pipeline structure design.

[0018] Preferably, when selecting the optimal channel, the selective frequency hopping module not only considers the channel RSSI situation, but also comprehensively considers the historical usage of the channel and the interference of adjacent channels. The module is provided with a channel history recording unit for storing the historical usage data of each channel, including usage time, signal quality and other information. At the same time, by monitoring the signal strength and interference characteristics of adjacent channels, the potential interference of adjacent channels to the current channel is evaluated.

[0019] Preferably, the variable channel bandwidth module adopts a smooth transition method when switching the channel bandwidth to improve the stability of the communication link. In addition, the module adopts a gradual bandwidth adjustment algorithm. During the process of adjusting the channel bandwidth, the channel bandwidth gradually transitions from the current value to the target value by gradually changing the cutoff frequency and signal processing parameters of the filter.

[0020] Preferably, the system also includes an interference detection module for monitoring the interference intensity of the current channel in real time, and feeding back the interference intensity information in the form of a digital signal to the RF front-end processing module, the selective frequency hopping module and the variable channel bandwidth module, and each module adjusts relevant parameters according to the interference intensity.

[0021] The present invention provides an anti-interference wireless communication system. It has the following beneficial effects:

[0022] 1. The present invention can suppress adjacent channel interference through the RF front-end processing module and the baseband signal preprocessing module, ensure that the useful signal obtains sufficient gain, and improve the signal-to-noise ratio. For example, in a complex electromagnetic environment, when there is strong adjacent channel interference, the independent baseband signal low-pass filter can filter out the interference signal in a targeted manner, and the AGC circuit amplifies the weak useful signal to a suitable amplitude, so that the signal reaches the optimal state before entering the high-speed sampling and baseband processing module, thereby improving the reliability of the signal, ensuring that the UAV accurately receives and processes control instructions and data, and stably executes tasks.

[0023] 2. The present invention uses selective frequency hopping to dynamically avoid interference channels. It can perform segmented threshold averaging when periodically scanning the RSSI of all defined channels, and accurately sort the channel interference conditions. When the current channel has high noise floor, low SNR, and high packet loss, the optimal channel for the current environment is quickly selected. For example, in an area where there are multiple wireless devices interfering, a certain channel is strongly interfered at a certain moment, causing a sharp drop in signal quality. The selective frequency hopping module can immediately switch to a channel with less interference to ensure that the communication link is continuously stable, so that the drone can flexibly respond to complex and changeable interference environments and avoid interruptions in communication due to interference in fixed channels.

[0024] 3. The present invention flexibly adapts to the interference intensity through variable channel bandwidth. When the SNR is low and the number of packet losses is high, a gradual bandwidth adjustment algorithm is used to gradually reduce the channel bandwidth from 20MHZ to 2.5MHz, so as to avoid instantaneous interruption of the communication link in a smooth transition. This method effectively ensures the reliable connection of the link by sacrificing part of the data throughput. For example, when the drone enters an area with concentrated interference, resulting in poor signal quality, the variable channel bandwidth module automatically reduces the channel bandwidth. Although the data transmission speed is reduced, it can effectively resist interference and maintain the stability of the communication link, so that the drone can continue to communicate with the ground station and receive necessary instructions and feedback information. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the module diagram of the anti-interference wireless communication system;

[0026] Figure 2 This is a schematic diagram of the channel bandwidth adjustment process of the present invention;

[0027] Figure 3 is a circuit structure diagram of the present invention;

[0028] Figure 4 It is a schematic diagram of data communication between the ground link and the airborne link of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0030] Example:

[0031] Please see attached Figure 1 -Attached Figure 4 , an embodiment of the present invention provides an anti-interference wireless communication system, comprising the following modules:

[0032] The RF front-end processing module is used to set the RF transceiver receiving gain and control the ADC to be in an unsaturated state. After the processing is completed, the signal is transmitted to the baseband signal pre-processing module;

[0033] The baseband signal preprocessing module includes an independent baseband signal low-pass filter and AGC circuit, which filters and amplifies the signal before transmitting it to the high-speed sampling and baseband processing module;

[0034] High-speed sampling and baseband processing module, used for sampling through high-speed ADC and performing baseband processing using FIR filter;

[0035] Selective frequency hopping module, used to divide the working frequency band into fixed channels and number them, and select the optimal channel according to the channel RSSI situation;

[0036] Variable channel bandwidth module, used to adjust the channel bandwidth when SNR is low and packet loss is high.

[0037] Analyzing the electromagnetic environment in which drones operate, it is common for multiple types of equipment to coexist in the operating frequency band. After passing through the mixer, stronger adjacent frequency signals will undergo spectrum shifting together with useful signals. If the baseband filtering performance of the RF transceiver is insufficient, two consequences will occur. One is that the useful signal will not obtain effective gain and the signal-to-noise ratio will deteriorate. The other is that sampling will result in aliasing, which will further affect the signal-to-noise ratio and cause a sharp drop in performance.

[0038] The present invention improves the adjacent channel interference suppression capability from the perspective of circuit structure and software algorithm. Figure 3 The circuit structure diagram shown in;

[0039] Generally, the RF transceiver has its own transceiver low-pass filter and transceiver gain function, but the receiving baseband filter generally has poor performance, especially when the useful signal is weak and the adjacent channel interference is strong. At this time, in order to ensure that the ADC is not saturated, the RF transceiver receiving gain cannot run at the maximum state, affecting the reception of useful signals. In view of this situation, the RF transceiver receiving gain is set to an appropriate value to ensure that the ADC is not saturated, and then the baseband signal passes through an independent low-pass filter to effectively filter the adjacent channel signal. At this time, if the signal is weak, it can be amplified by the AGC circuit. Since the signal bandwidth is dynamically adjusted between 2.5MHz, 5MHz, 10MHz, and 20MHz, the baseband can configure the low-pass filter bandwidth through the control signal. This circuit structure can ensure that before entering the high-speed ADC, the useful signal amplitude is adjusted to the optimal state, the adjacent signal amplitude is suppressed to a certain extent, and the high-speed ADC sampling frequency is greater than 2 times the frequency band bandwidth. The useful signal and the adjacent signal are all sampled into the baseband for processing, and the baseband uses the FIR filter to filter out the adjacent band signal sampled by the ADC.

[0040] Due to the randomness of interference, selective frequency hopping is another means to improve the system's anti-interference ability. We divide the working frequency band into fixed channels and number the channels. When the device is working, it periodically scans the RSSI of all defined channels, averages the RSSI values ​​in segments over a period of time, and sorts the channel interference conditions. When the current channel has a high noise floor, low SNR, and a high number of packet losses, the optimal channel for the current environment is selected.

[0041] When the SNR is low and the number of packet losses is high, the channel bandwidth can be switched, for example, from 20 MHz to 2.5 MHz, sacrificing data throughput to ensure reliable link connection. The signal bandwidth switching algorithm is established as follows:

[0042] Algorithm description: When the SNR is detected to be lower than a certain threshold SNR th1 And the number of packet loss is higher than a certain threshold L th1 When the channel bandwidth is reduced from 20MHz to 2.5MHz, the reduction amplitude can be set according to the actual situation. Here, it is assumed that the reduction is carried out in a fixed step size.

[0043] Algorithm formula: Assume that the current channel bandwidth is B current , initial bandwidth B init =20MHz, target minimum bandwidth B m in=2.5MHz, step size is ΔB, then the channel bandwidth adjustment formula is B n ew=B current -ΔB ,当 B new ≤B min When B n ew=B min . At the same time, the SNR condition is met <SNR th1 And L>L th1 Trigger adjustment.

[0044] Example: Let SNR th1 =8dB,L th1 =15, ΔB = 2.5MHz. When a channel SNR = 7dB, L = 18 is detected, the bandwidth adjustment is triggered. current =20MHz, then after the first adjustment, B new =20-2.5=17.5MHz; if the conditions are still met after the second test, B new =17.5-2.5=15MHz, and so on, until B new ≤2.5MHz, at this time B n ew=2.5MHz.

[0045] In the RF front-end processing module, the appropriate value of the RF transceiver receiving gain is dynamically adjusted based on the saturation threshold of the ADC and the actual received signal strength monitored in real time.

[0046] The RF transceiver is provided with an automatic gain adjustment circuit, which can monitor the received signal strength in real time and compare it with the saturation threshold of the ADC, and automatically adjust the gain of the RF transceiver according to the comparison result to ensure that the ADC always works in an unsaturated state.

[0047] The independent baseband signal low-pass filter in the baseband signal preprocessing module adopts a reconfigurable filter structure, which can flexibly configure the bandwidth according to the control signal sent by the baseband. The reconfigurable filter structure includes multiple filter branches with different cutoff frequencies. The switch array is controlled by the baseband control signal to select different filter branch combinations.

[0048] The AGC circuit adopts a multi-stage gain control structure, automatically selects a suitable gain multiple according to the input signal strength, and realizes accurate amplification of the signal. The multi-stage gain control structure includes at least three stages of gain amplifiers, and the gain multiple of each stage of gain amplifier can be adjusted according to preset rules.

[0049] In the high-speed sampling and baseband processing module, the high-speed ADC adopts a pipeline sampling structure, which is composed of multiple sampling cascades. Each sampling stage partially samples and processes the input signal, and sampling is achieved through a multi-stage parallel mode.

[0050] The baseband processing unit adopts a distributed algorithm to implement the FIR filter, completes the filtering operation through a lookup table and an adder operation, improves the filtering efficiency and the utilization rate of hardware resources, the lookup table is pre-calculated and stored according to the coefficients of the FIR filter, and the adder operation is designed based on a pipeline structure.

[0051] When selecting the optimal channel, the selective frequency hopping module not only considers the channel RSSI situation, but also comprehensively considers the historical usage of the channel and the interference of adjacent channels. The module is equipped with a channel history record unit for storing the historical usage data of each channel, including usage time, signal quality and other information. At the same time, by monitoring the signal strength and interference characteristics of adjacent channels, the potential interference of adjacent channels to the current channel is evaluated. In the process, the following algorithm is established for evaluation of channel interference:

[0052] Algorithm description:

[0053] The RSSI value of each channel within a period of time is divided into segments, and then the average value is calculated in each segment to evaluate the interference situation of the channel.

[0054] Algorithm formula:

[0055] Assume that the RSSI value sequence of the channel collected in the time interval [t1, t2] is RSSI = {r1, r2, ..., r n}, the time interval is divided into m segments, and the length of each segment is

[0056] The set of RSSI values ​​in the i-th segment is:

[0057] RSSI i = {r j ,rj+1 ,…,r j+k}

[0058] in Assume that n is divisible by m. If not, use a reasonable method of rounding up or down.

[0059] Then the RSSI average value of the i-th segment is:

[0060]

[0061] Finally, the segment threshold average RSSI value of the channel in [t1, t2] is

[0062] Example:

[0063] 100 RSSI values ​​of a channel are collected within 10 seconds (n=100, t1=0, t2=10), and they are divided into 5 segments (m=5), each segment is Δt=2 seconds long. The RSSI values ​​in the first segment are {-60,-62,-58,-65,-63,-61,-59,-64,-60,-62,-63,-61,-58,-60,-62,-64,-65,-63, (|RSSI1|=20), then

[0064]

[0065] Similarly, calculate the average value of other segments Assuming they are -62.5, -60.8, -63.2, and -61.5 respectively, the average RSSI value of the segment threshold of the channel within these 10 seconds is:

[0066]

[0067] At this time, the obtained segment threshold average RSSI value can be judged by comparing it with a preset threshold and with historical data, and the interference situation of the current channel can be judged.

[0068] Principle: Preset one or more RSSI thresholds based on actual application scenarios and device performance. Compare the average RSSI value of the segmented threshold with these thresholds to determine the degree of channel interference. For example, you can set a high threshold RSSI high and a low threshold RSSI low ;

[0069] Example: Setting RSSI high =-65dBm,RSSI low =-80dBm. When the average RSSl value of the segment threshold is greater than RSSI highWhen the value is less than RSSI, it can be determined that the channel is in a strong interference state; when the value is less than RSSI low When the channel interference is between , the channel interference is considered to be weak; and when it is between the two, the channel interference is moderate. If the calculated segment threshold average RSSI value of a channel is -62dBm, then the channel is in a strong interference state.

[0070] Comparison with historical data

[0071] Principle: Compare the currently calculated average RSSI value of the segment threshold with the average RSSI value of the channel in similar time periods or scenarios in the past. If the current value is significantly higher than the historical average, it means that the channel may be subject to stronger interference; conversely, if the current value is significantly lower than the historical average, it may indicate that the interference has weakened.

[0072] Example: Assume that the average RSSI value of a channel in the same period of time in the past week is stable at around -70dBm, and the current value obtained by the segmented threshold average algorithm is -60dBm. This indicates that the interference to the channel is stronger than before, because the closer the RSSI value is to 0dBm, the greater the signal strength, and the stronger the interference may be (in this channel environment, it is believed that the abnormal increase in signal strength is caused by interference).

[0073] At the same time, for the selection of the optimal channel, we propose the following algorithm:

[0074] Algorithm description: Select the optimal channel based on the channel noise floor, SNR, number of packet losses, and RSSI value after segment threshold average. When the channel noise floor is higher than a certain threshold N th ,SNR is lower than a certain threshold SNR th , the number of packet loss is higher than a certain threshold L th When the average RSSI value of the segment threshold is combined, the channel with the best overall situation is selected.

[0075] Algorithm formula: For each channel c, define an evaluation function Score(c) to measure its quality:

[0076]

[0077] in is the average RSSI value of the segmented threshold of channel c, N(c) is the noise floor of channel c, SNR(c) is the signal-to-noise ratio of channel c, L(c) is the number of packet losses of channel c, w1, w2, w3, w4 are weight coefficients, and w1+w2+w3+w4=1, adjust the weights according to the actual situation to balance the influence of various factors. Select the channel with the largest Score(c) value as the optimal channel;

[0078] Example:

[0079] Assume there are three channels c1, c2, c3, N th =-90dBm,SNR th =10dB,L t h = 10, w1 = 0.3w2 = 0.2, w3 = 0.3, w4 = 0.2;

[0080] Channel c1 N(c1)=-85dBm,SNR(c1)=8dB,L(c1)=12;

[0081] Channel c2 N(c2)=-88dBm,SNR(c2)=9dB,L(c2)=8;

[0082] Channel c3 N(c3)=-80dBm,SNR(c3)=7dB,L(c3)=15;

[0083] Calculate Score(c1):

[0084]

[0085] Calculate Score(c2):

[0086]

[0087] Calculate Score(c3):

[0088]

[0089]

[0090] By comparison, Score(c2) is the largest, so channel c2 is selected as the optimal channel;

[0091] The variable channel bandwidth module adopts a smooth transition method when switching the channel bandwidth to improve the stability of the communication link. In addition, the module adopts a gradual bandwidth adjustment algorithm. During the process of adjusting the channel bandwidth, the channel bandwidth gradually transitions from the current value to the target value by gradually changing the cutoff frequency and signal processing parameters of the filter.

[0092] The system also includes an interference detection module for real-time monitoring of the interference intensity of the current channel and feeding back the interference intensity information in the form of digital signals to the RF front-end processing module, the selective frequency hopping module and the variable channel bandwidth module. Each module adjusts relevant parameters according to the interference intensity.

[0093] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An anti-interference wireless communication system, characterized in that: Includes the following modules: The RF front-end processing module is used to set the RF transceiver receiving gain and control the ADC to be in an unsaturated state. After the processing is completed, the signal is transmitted to the baseband signal pre-processing module; The baseband signal preprocessing module includes an independent baseband signal low-pass filter and AGC circuit, which filters and amplifies the signal before transmitting it to the high-speed sampling and baseband processing module; High-speed sampling and baseband processing module, used for sampling through high-speed ADC and performing baseband processing using FIR filter; Selective frequency hopping module, used to divide the working frequency band into fixed channels and number them, and select the optimal channel according to the channel RSSI situation; Variable channel bandwidth module, used to adjust the channel bandwidth when SNR is low and packet loss is high.

2. The anti-interference wireless communication system according to claim 1, characterized in that: In the RF front-end processing module, the appropriate value of the RF transceiver receiving gain is dynamically adjusted based on the saturation threshold of the ADC and the actual received signal strength monitored in real time.

3. The anti-interference wireless communication system according to claim 2, characterized in that: The RF transceiver is provided with an automatic gain adjustment circuit, which can monitor the received signal strength in real time and compare it with the saturation threshold of the ADC, and automatically adjust the gain of the RF transceiver according to the comparison result to ensure that the ADC always works in an unsaturated state.

4. The anti-interference wireless communication system according to claim 1, characterized in that: The independent baseband signal low-pass filter in the baseband signal preprocessing module adopts a reconfigurable filter structure, which can flexibly configure the bandwidth according to the control signal sent by the baseband. The reconfigurable filter structure includes multiple filter branches with different cutoff frequencies. The switch array is controlled by the baseband control signal to select different filter branch combinations.

5. The anti-interference wireless communication system according to claim 1, characterized in that: The AGC circuit adopts a multi-stage gain control structure, automatically selects a suitable gain multiple according to the input signal strength, and realizes accurate amplification of the signal. The multi-stage gain control structure includes at least three stages of gain amplifiers, and the gain multiple of each stage of gain amplifier can be adjusted according to preset rules.

6. The anti-interference wireless communication system according to claim 1, characterized in that: In the high-speed sampling and baseband processing module, the high-speed ADC adopts a pipeline sampling structure, which is composed of multiple sampling cascades. Each sampling stage partially samples and processes the input signal, and sampling is achieved in a cascade manner.

7. The anti-interference wireless communication system according to claim 5, characterized in that: The baseband processing unit adopts a distributed algorithm to implement the FIR filter, completes the filtering operation through a lookup table and an adder operation, improves the filtering efficiency and the utilization rate of hardware resources, the lookup table is pre-calculated and stored according to the coefficients of the FIR filter, and the adder operation is designed based on a pipeline structure.

8. The anti-interference wireless communication system according to claim 1, characterized in that: When selecting the optimal channel, the selective frequency hopping module not only considers the channel RSSI situation, but also comprehensively considers the historical usage of the channel and the interference of adjacent channels. The module is provided with a channel history record unit for storing the historical usage data of each channel, including the usage time, signal quality and other information. At the same time, by monitoring the signal strength and interference characteristics of adjacent channels, the potential interference of adjacent channels to the current channel is evaluated.

9. The anti-interference wireless communication system according to claim 1, characterized in that: The variable channel bandwidth module adopts a smooth transition method when switching the channel bandwidth to improve the stability of the communication link. In addition, the module adopts a gradual bandwidth adjustment algorithm. During the process of adjusting the channel bandwidth, the channel bandwidth gradually transitions from the current value to the target value by gradually changing the cutoff frequency and signal processing parameters of the filter.

10. The anti-interference wireless communication system according to claim 1, characterized in that: The system also includes an interference detection module for real-time monitoring of the interference intensity of the current channel and feeding back the interference intensity information in the form of digital signals to the RF front-end processing module, the selective frequency hopping module and the variable channel bandwidth module. Each module adjusts relevant parameters according to the interference intensity.

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