Satellite communication interference detection method based on power joint signal-to-noise ratio estimation

Abstract

The invention discloses a satellite communication interference detection method based on power joint signal-to-noise ratio estimation, and belongs to the technical field of satellite communication countermeasure. The interference detection method comprises the following steps: carrying out power estimation on a received signal by virtue of digital processing of a satellite communication receiving end, and counting an estimated value within average observation time; performing signal-to-noise ratio estimation on a received signal based on conventional processing such as sampling rate conversion, automatic gain control, matched filtering and synchronous timing, and calculating a mean value of a plurality of symbols in observation time; and finally judging whether interference exists in a transmission link or not by combining the estimated received signal power and the estimated signal-to-noise ratio on the basis of comprehensively judging the state of the satellite communication link according to the current climate, weather change and working frequency band. The method is insensitive to interference pattern changes, can obtain a relatively high detection probability when the interference intensity of the satellite communication link is relatively low, can powerfully support the optimization and adjustment of anti-interference measures of the satellite communication link, and improves the transmission performance of a system.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite communication countermeasures, and in particular relates to a satellite communication interference detection method based on power joint signal-to-noise ratio estimation, which can be used for space-based electromagnetic situation awareness and satellite communication physical layer transmission link interference detection and cognition. Background Art

[0002] In the face of the increasingly prominent long-distance, large-capacity information transmission guarantee needs in future joint operations, satellite communications have become the core mode of information transmission in joint operations battlefields due to their wide coverage, little impact from terrain and landforms, and wide available frequency bands. It is a key factor affecting the success of operations. However, in complex electromagnetic environments, satellite communications are often subject to interference from the enemy, so accurately detecting and judging whether there is interference in the transmission link has become the first problem that needs to be solved to further take effective anti-interference measures and improve the reliability of satellite communications.

[0003] In the confrontation process, artificial interference on satellite communication links is the most effective means to reduce its transmission performance. Among them, suppression interference such as single tone, multi-tone, frequency modulation, partial band noise, phase modulation and full band noise are the main ones. The intensity of interference reaching the receiving end of the satellite communication link is affected by factors such as the distance from the interference transmitter and the transmission power. For the problem of interference detection, the common detection methods currently include two categories: energy detection and signal feature analysis detection. For non-direct multipath fading channels, the performance change of time domain energy interference detection can be measured by effective detection and false alarm probability. For details, please refer to the literature: Atapattu S, Tellambura C, Jiang H "Performance of an energy detector over channels with both multipath fading and shadowing", IEEE Transactions On Wireless Communications, 2010, Vol. 9, No. 12, Pages: 3662-3670. The energy detection method can also flexibly and adaptively adjust the decision threshold according to the estimation of the noise intensity of the transmission channel and the frequency domain narrowband characteristics of some interference signals, thereby improving the interference detection performance to a certain extent. For details, see the following literature: Wang Shuo, Chen Zeyi, "An Adaptive Interference Energy Detection Algorithm", Journal of Anhui University (Natural Science Edition), 2016, Vol. 40, No. 1, pp. 59-63; Vartiainen J, Lehtomaki JJ, Saamisari H, "Double-Threshold Based NarrowbandSignal Extraction", Proceedings of 61st IEEE Vehicle Technology Conference (VTC), 2005, Stockholm Sweden, pp. 2394-2398. In addition to the time-frequency domain energy of the interference signal, the envelope change and cyclostationary characteristics of the received signal can also be fully utilized to determine whether there is interference, such as interference detection algorithm based on forward continuous variance removal (FCVE) and narrowband interference detection based on cyclic Wiener filtering. For details, please refer to the literature: Li Guo, Wen Ni, Gong Fengkui "Interference detection and diversity suppression algorithm for OFDM system under partial frequency band interference", Journal of Communications, 2021, Vol. 42, No. 9, pp. 194-204; Chen Xiaowei, Yang Wenge "Blind interference detection of DSSS system based on time-varying whitening filter", Systems Engineering and Electronics, 2021, Vol. 43, No. 7, pp. 1981-1988.Without considering the computational complexity, the interference detection problem of the global navigation satellite (GNSS) system can be solved to a certain extent by using the high-order cumulant analysis of the signal. For details, see the literature: Fan Guangwei, Lu Yuliang, Chao Lei, "Research on Interference Detection Technology of Diagonal Slice High-Order Cumulant", Radio Engineering, 2014, Vol. 44, No. 1, pp. 16-19.

[0004] The interference detection method based on interference signal feature analysis is limited to a certain extent by the relative strength of the interference, communication signal, and channel noise. When the strength of the interference signal is not much different from that of the communication signal, or the channel noise is strong, it will be impossible to accurately detect whether there is interference. Summary of the invention

[0005] The present invention aims to improve the transmission reliability of satellite communication links under space-based electromagnetic situational awareness and confrontation, to accurately detect and judge whether there is interference in the transmission link, and to support subsequent interference recognition and suppression, and provides a satellite communication interference detection method based on power joint signal-to-noise ratio estimation.

[0006] In order to achieve the above-mentioned purpose of accurate detection of satellite communication link interference, the technical solution adopted by the present invention is:

[0007] A satellite communication interference detection method based on power combined signal-to-noise ratio estimation is used to determine whether there is interference in a satellite communication link, and includes the following steps:

[0008] Step 1, performing gain normalization on the receiving end radio frequency channel, the satellite communication receiving end performs analog-to-digital conversion on the received signal, and uses a statistical averaging method to estimate the power of the received signal in the digital domain; the satellite communication receiving end includes an onboard payload and a ground station end;

[0009] Step 2: Perform maximum likelihood estimation on the signal-to-noise ratio of the received signal by using a decision feedback method, and calculate the average signal-to-noise ratio estimation value of multiple symbols;

[0010] Step 3: Using climate, weather changes and the operating frequency of the satellite communication link as reference conditions, estimate the interference-free state of the satellite communication link, and make a comprehensive comparison with the received signal power and signal-to-noise ratio estimates to determine whether there is interference in the transmission link.

[0011] Further, step 1 includes the following steps:

[0012] Step 1-1, keeping the RF channel gain of the satellite communication receiving end unchanged, and performing analog-to-digital conversion on the received signal;

[0013] Step 1-2: Determine the pre-selection filter bandwidth B according to the frequency band range of the interference signal detection Δ , perform pre-selection filtering on the received signal;

[0014] Step 1-3, perform time domain power estimation on the pre-selected filtered signal sequence of length N to obtain a power estimation value

[0015]

[0016] Wherein, x(n) is the received signal in the digital domain.

[0017] Further, step 2 includes the following steps:

[0018] Step 2-1, according to the system parameters, the receiving end of the satellite communication link performs sampling rate conversion, matched filtering, symbol timing and carrier recovery processing to obtain the symbol to be demodulated s(n);

[0019] Step 2-2, for the orthogonal components s of s(n) i (n) and s q (n) Make a decision and obtain two orthogonal corresponding decision outputs and Use L symbols to estimate the signal-to-noise ratio and get the estimated signal-to-noise ratio for:

[0020]

[0021] Further, step 3 includes the following steps:

[0022] Step 3-1, calculating the spatial transmission path loss corresponding to the working frequency band according to the climate and weather conditions of the satellite communication link during interference detection;

[0023] Step 3-2, based on the link parameters of path loss, transmission power, transmission link bandwidth, transmit and receive antenna gain, and G / T value at the receiving end, calculate the received signal power range (P min ,P max ) and symbol signal-to-noise ratio range (SNR min ,SNR max );

[0024] Step 3-3: convert the power estimate and the signal-to-noise ratio estimate Make a joint decision to determine whether there is interference in the transmission link:

[0025]

[0026] Wherein, λ>1, which indicates the interference detection decision adjustment coefficient.

[0027] The beneficial effects of the present invention are:

[0028] 1. The present invention can accurately determine whether interference exists in the system's physical layer transmission link without changing the original hardware structure of the satellite communication system receiving end (on-board payload and ground station and end).

[0029] 2. The present invention can be applied to interference detection of various signal types, has no restrictions on interference patterns, and has good universality.

[0030] 3. Compared with energy detection and feature analysis detection, the present invention still has good detection performance when the interference signal strength is weak or is greatly affected by the communication signal and channel noise. It can realize accurate detection of satellite communication link interference under complex conditions and has strong adaptability.

[0031] 4. The present invention does not need to calculate and analyze characteristic parameters such as the cyclic spectrum and high-order cumulants of the received signal, but makes full use of the characteristics of line-of-sight transmission of satellite communication links, can achieve accurate detection of weak interference, and is insensitive to the interference signal pattern, which can significantly improve the satellite communication interference detection performance under complex conditions such as relatively weak interference intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a principle block diagram of an embodiment of the present invention;

[0033] Figure 2 Detection performance diagram of different types of interference according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0035] Satellite communication interference detection method based on power combined with signal-to-noise ratio estimation, this method is based on power combined with signal-to-noise ratio estimation, and accurately determines whether there is interference in the satellite communication link, including:

[0036] (1) Estimating the power of the received signal in the digital domain and statistically averaging the estimated value over the observation time;

[0037] (2) Use decision feedback to estimate the symbol signal-to-noise ratio and calculate the mean of multiple symbols within the observation time;

[0038] (3) Based on the current climate, weather changes, operating frequency band, and other parameters of the communication link, the signal power range and symbol signal-to-noise ratio range of the satellite communication receiving end when there is no interference are calculated, and the estimated received signal power and signal-to-noise ratio are combined to finally determine whether there is interference in the transmission link.

[0039] like Figure 1 As shown, the specific method is as follows:

[0040] First, the gain of the receiving end RF channel is normalized. The satellite communication receiving end (including the on-board processing payload and the ground station) converts the received signal into a digital signal, and the power of the received signal is estimated in the digital domain using statistical averaging.

[0041] For the RF channel gain control, it is necessary to ensure that it has a large dynamic range and can normally receive strong and weak signals. The analog-to-digital conversion of the received signal can be configured according to the conventional receiving end without special processing.

[0042] Based on the frequency band range of interference detection B Δ , pre-select and filter the received signal in the digital domain to reduce the impact of signals outside the detection bandwidth on power estimation.

[0043] After pre-selection filtering, the received signal x(n) is obtained. Since x(n) is usually sampled at multiple times the symbol rate, the time domain power estimation is performed on the pre-selection filtered signal sequence of length N to obtain the power estimation value As shown below:

[0044]

[0045] Secondly, the symbol signal-to-noise ratio of the received signal is estimated. The sampling rate conversion, automatic gain control, matched filtering and synchronous timing front-end processing of the signal-to-noise ratio estimation are the same as those of the satellite communication receiving end without interference.

[0046] According to the modulation method adopted by the satellite communication link, the received symbol s(n) after timing and carrier recovery is orthogonally demodulated, that is, the orthogonal components s of s(n) are i (n) and s q (n) decision, and obtain two orthogonal corresponding decision outputs and Use L symbols to estimate the signal-to-noise ratio, corresponding to the signal-to-noise ratio estimate It can be expressed as:

[0047]

[0048] Finally, the combined received signal power estimate and the signal-to-noise ratio estimate Determine whether there is interference in the transmission link; specifically:

[0049] According to the climate and weather conditions of the satellite communication link during interference detection, the spatial transmission path loss γ corresponding to the working frequency band is calculated;

[0050] According to the path loss γ, the transmission power P t , transmission link bandwidth B, transmitting antenna gain G t , the ratio of the receiving antenna gain to the thermal noise (i.e. G / T value) GTr , calculate the received signal power value P r =P t -g+G t +G Tr , set the signal power fluctuation range to P Δ , then the received signal power range without interference is (P min ,P max ), where P min =P r -P D / 2,P max =P r +P D / 2, assuming that the noise density at the receiving end is n0, the received symbol signal-to-noise ratio range is (SNR min ,SNR max ), where SNR min =P min / (n0×B), SNRmax=Pmax / (n0×B);

[0051] Based on the setting of the interference detection decision adjustment coefficient λ, the actual received signal power estimation value is analyzed Sum symbol signal-to-noise ratio estimate Whether the following conditions are met, and then determine whether there is interference:

[0052]

[0053] The principle of this method is as follows:

[0054] First, the gain of the RF channel at the receiving end is kept unchanged so that strong and weak signals with a large dynamic range can be received. A digital pre-selection filter corresponding to the interference detection frequency band is designed in the digital domain to filter the received signal.

[0055] The signal is divided into two paths. One path intercepts the pre-selected filtered signal sequence of length N, and calculates the mean of the square of the modulus value of the signal sequence as the received signal power estimation result.

[0056] The other path first performs sampling rate conversion, automatic gain control, matched filtering, synchronous timing and carrier recovery, then intercepts L symbols for orthogonal demodulation and decision, obtains the symbols after demodulation decision, and uses the L symbols before and after demodulation decision to calculate the estimated value of the received signal-to-noise ratio

[0057]

[0058] According to the climate and weather conditions of the satellite communication link during interference detection, the spatial transmission path loss corresponding to the working frequency band is calculated, and then the signal power range (Pmin ,P max ) and signal-to-noise ratio range (SNR min ,SNR max ), set the interference detection decision adjustment coefficient λ.

[0059] Analyze the received signal power estimate Sum symbol signal-to-noise ratio estimate Whether the following conditions are met is used to determine whether interference exists.

[0060] This method can take advantage of the fact that satellite communication is line-of-sight transmission and the link status is relatively stable. By analyzing the changes in the signal power and symbol signal-to-noise ratio at the receiving end, it can determine whether there is interference in the link. It can significantly improve the performance of satellite communication links under complex conditions in detecting various types of interference.

[0061] Here is a more specific example:

[0062] The satellite communication link adopts QPSK modulation, and the corresponding symbol rate is 1.28Msps. The signal-to-noise ratio of the signal arriving at the receiving end is set to 5dB and 10dB. The corresponding interference is set to four styles: single tone, multi-tone, frequency modulation and partial band noise. The frequency interval between the single tone interference and the center frequency is -0.1088MHz. The multi-tone interference consists of four single tones, which are -0.2944MHz, -0.0448MHz, 0.1408MHz and 0.2624MHz from the center frequency. The starting and ending frequencies of the frequency modulation interference relative to the center frequency are -0.128MHz and 0.192MHz, respectively, and the frequency modulation period is 0.4ms. The bandwidth of the partial band noise interference is 0.128MHz, which is 0.0128MHz away from the center frequency. In addition, the sequence length N and symbol length L used for power and SNR estimation at the receiving end are set to 4096 and 1024 respectively. Considering that the satellite communication link state remains basically constant in a short period of time when the weather remains unchanged, and the thermal noise intensity of the antenna and RF channel also fluctuates slightly, the simulation sets the accuracy of link state estimation to 4 dB, that is, 10×log 10 (Pmax / Pmin) = 4dB. Set the interference detection decision adjustment coefficient λ to 1.75.

[0063] Through the statistics of 10,000 independent simulation results, the accurate detection probability of the four types of interference under different interference intensities is as follows: Figure 2As shown. It can be seen that the interference detection method based on power joint signal-to-noise ratio estimation has basically the same accurate detection probability for the four types of interference, indicating that this method is insensitive to the interference pattern. When the signal-to-noise ratio SNR is 5dB, the required interference-to-signal ratio JSR is -7dB when the probability of accurate detection of the four types of interference reaches 98%. When the signal-to-noise ratio SNR is increased to 10dB, the required interference-to-signal ratio JSR is reduced to -13dB when the probability of accurate detection of the four types of interference reaches 98%. It can be seen that this method performs detection based on the changes in signal power and signal-to-noise ratio at the receiving end of the satellite communication link, which can improve the detection performance in complex situations such as weak interference intensity.

[0064] In summary, the method of the present invention aims at the problem of whether the satellite communication link is interfered, makes full use of the characteristics of satellite communication line-of-sight transmission and relatively stable link status, combines the signal power and signal-to-noise ratio estimation at the receiving end, and realizes accurate detection of different parameters and different types of interference under complex conditions through comprehensive analysis and judgment. Compared with the energy detection and signal feature analysis detection methods, it has more superior performance and can be applied to complex scenarios such as low interference-to-signal ratio and low interference-to-noise ratio. The method of the present invention can be applied to satellite communication systems with different transmission systems, can accurately detect interference of different styles and parameters, and provide strong support for interference recognition and suppression of space-based electromagnetic situational awareness and satellite communication transmission links.

Claims

1. A satellite communication interference detection method based on power combined signal-to-noise ratio estimation, characterized in that: The method is used to determine whether there is interference in a satellite communication link, and includes the following steps: Step 1, performing gain normalization on the receiving end radio frequency channel, the satellite communication receiving end performs analog-to-digital conversion on the received signal, and uses a statistical average method to estimate the power of the received signal in the digital domain; the satellite communication receiving end includes an onboard payload and a ground station end; Step 2: Perform maximum likelihood estimation on the signal-to-noise ratio of the received signal by using a decision feedback method, and calculate the average signal-to-noise ratio estimation value of multiple symbols; Step 3: Using climate, weather changes and the operating frequency of the satellite communication link as reference conditions, estimate the interference-free state of the satellite communication link, and make a comprehensive comparison with the received signal power and signal-to-noise ratio estimates to determine whether there is interference in the transmission link.

2. The satellite communication interference detection method based on power combined signal-to-noise ratio estimation according to claim 1 is characterized in that: Step 1 includes the following steps: Step 1-1, keeping the RF channel gain of the satellite communication receiving end unchanged, and performing analog-to-digital conversion on the received signal; Step 1-2: Determine the pre-selected filter bandwidth B according to the frequency band range of the interference signal detection Δ , perform pre-selection filtering on the received signal; Step 1-3, perform time domain power estimation on the pre-selected filtered signal sequence of length N to obtain a power estimation value Wherein, x(n) is the received signal in the digital domain.

3. The satellite communication interference detection method based on power combined signal-to-noise ratio estimation according to claim 1, characterized in that: Step 2 includes the following steps: Step 2-1, according to the system parameters, the receiving end of the satellite communication link performs sampling rate conversion, matched filtering, symbol timing and carrier recovery processing to obtain the symbol to be demodulated s(n); Step 2-2, for the orthogonal components s of s(n) i (n) and s q (n) Make a decision and obtain two orthogonal corresponding decision outputs and Use L symbols to estimate the signal-to-noise ratio and get the estimated signal-to-noise ratio for:

4. The satellite communication interference detection method based on power combined signal-to-noise ratio estimation according to claim 3 is characterized in that: Step 3 includes the following steps: Step 3-1, calculating the spatial transmission path loss corresponding to the working frequency band according to the climate and weather conditions of the satellite communication link during interference detection; Step 3-2, based on the link parameters of path loss, transmission power, transmission link bandwidth, transmit and receive antenna gain, and G / T value at the receiving end, calculate the received signal power range (P min ,P max ) and symbol signal-to-noise ratio range (SNR min ,SNR max ); Step 3-3: convert the power estimate and the signal-to-noise ratio estimate Make a joint decision to determine whether there is interference in the transmission link: Wherein, λ>1, which indicates the interference detection decision adjustment coefficient.

Images