Flight ad hoc network airspace anti-interference method based on channel alternating estimation

Abstract

The invention provides a flight ad hoc network airspace anti-interference method based on channel alternating estimation. The quality of wireless communication is limited by a complex environment, a fading effect of a wireless channel, openness and the like, so that a flying ad hoc network system is more easily interfered and attacked. In order to solve the problem, an MIMO-OFDM spatial filtering method based on channel alternating estimation is discussed to be used for resisting strong continuous interference attacks. According to the method, under the interference attack, the required signal can be effectively recovered based on the spatial domain filtering basic principle through the alternative iterative estimation of the sender channel and the interference channel. Simulation results show that the method has excellent anti-interference performance, bit error rate can be greatly reduced under strong interference attack, and transmission reliability is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of intelligent unmanned equipment platform and technology, and relates to communication systems and signal processing. In particular, it relates to a flight ad hoc network airspace anti-interference method based on channel alternate estimation. BACKGROUND

[0002] A flight ad hoc network usually takes a UAV as a network node, and uses dynamic networking and wireless relay technology to realize the interconnection between nodes, with the advantages of low cost, strong mobility and effective deployment. However, the quality of wireless communication is limited by complex environment, fading effect of wireless channel and openness, making the communication system more vulnerable to interference attacks.

[0003] There are three typical interference attack modes: 1) Random interference. This interference mode is more energy-saving, which releases interference signals at random time and for a random duration. However, due to the random interference behavior, the interference ability is limited; 2) Reactive interference. It is more common, characterized by effectiveness, energy saving and stealth, but has a certain reaction time; 3) Normal interference. The jammer continuously sends interference signals to destroy the system packet transmission, has the ability to cover the overall framework structure, but is easy to be discovered, which is the focus of this patent research.

[0004] The flight ad hoc network, like many modern wireless communication networks, uses orthogonal frequency division multiplexing (OFDM) as one of its core technologies. OFDM enhances the robustness of the system in the presence of multipath fading and severe noise. However, it is not ideal when facing strong interference attacks from the enemy.

[0005] With the rapid development and wide application of multiple-input multiple-output (MIMO) technology, new wireless devices are equipped with more and more antennas. MIMO can be used to generate spatial diversity and spatial multiplexing gain to improve channel capacity. More importantly, MIMO-based interference cancellation technology greatly enhances the transmission capacity of MIMO communication systems. Therefore, many researchers consider combining MIMO and OFDM to design MIMO-OFDM-based interference defense mechanisms.

[0006] Spatial anti-interference relies on the spatial diversity of MIMO technology to enhance the received power of useful signals and eliminate adversarial interference. It mainly refers to adaptive antenna beamforming technology in array signal processing, which is currently developing maturely. Some scholars have summarized that the beam generated by adaptive beamforming can achieve high gain in the direction of the desired signal and zero suppression effect for unwanted signals. Its essence is to perform spatial filtering on each array element by a certain receiving criterion to enhance the ability to enhance the desired signal and suppress the interference signal.

[0007] Therefore, how to improve the anti-interference ability of the flight self-organizing network based on the basic principle of spatial filtering is still a research hotspot in the field. SUMMARY

[0008] The application provides a flight self-organizing network spatial anti-interference method based on channel alternate estimation, and solves the problems disclosed in the background art.

[0009] In order to solve the above technical problems, the technical scheme adopted by the application is:

[0010] The flight self-organizing network spatial anti-interference method based on channel alternate estimation comprises:

[0011] A 1*2 MIMO communication model is constructed between a sending party and a receiving party of a transmission OFDM signal;

[0012] The OFDM signal is divided into a plurality of OFDM symbols, and each OFDM symbol is divided into a pilot part and a data part;

[0013] First OFDM symbol processing: the pilot part is pre-filtered, and the sending party channel estimation is performed by using the filtered pilot receiving signal; the data part is subjected to interference party channel ratio estimation;

[0014] Second OFDM symbol processing: the pilot part uses the interference party channel ratio of the first OFDM symbol to derive the sending party channel; the data part uses the ratio of the two smoothed signals to replace the interference party channel ratio, and performs spatial filtering by using the known sending party channel and the interference party channel ratio of the current symbol;

[0015] Third OFDM symbol processing: the pilot part uses the sending party channel of the second OFDM symbol to derive the interference party channel ratio, detects the interference, uses the known pilot signal and the known sending channel to restore the receiving signal of the pilot signal receiving party, subtracts the receiving signal of the receiving party from the mixed signal to obtain the interference receiving signal of the receiving party, and calculates the interference channel ratio; the data part uses the sending party channel of the second OFDM symbol and the interference party channel ratio of the current symbol to perform spatial filtering;

[0016] Fourth OFDM symbol processing: the pilot part uses the interference party channel ratio of the third OFDM symbol to derive the sending party channel; and the pilot part uses the known sending party channel of the current symbol and the interference party channel ratio of the third OFDM symbol to perform spatial filtering;

[0017] The third OFDM symbol processing and the fourth OFDM symbol processing are alternately performed on the remaining OFDM symbols until all the OFDM symbols are processed, and the required signal is restored.

[0018] Further, the 1*2 MIMO communication model is constructed by using The representative sending end signal is represented as: The sending source signal is represented as: The interference signal is represented as: The 2*2 channel matrix includes the source signal channel and the interference channel. The receiving end signal is represented as:

[0019] .

[0020] Further, the method of spatial domain filtering is to transform the receiving signal y to the signal subspace perpendicular to , to obtain the projection signal: ;

[0021] Divide both sides of the equation by to obtain the sending signal:

[0022] .

[0023] Further, the interference party channel ratio estimation method in the first OFDM symbol processing is:

[0024] Replace the interference party channel ratio with , wherein the symbol number is represented as n, and the subcarrier number is represented as k.

[0025] Further, the smoothing processing is performed on :

[0026] ;

[0027] K takes 3 5 subcarriers on the left and right of the subcarrier k, the 3 5 subcarriers on the left and right of the subcarrier k are added and averaged to reduce the error influence in the channel estimation.

[0028] Further, the sending party channel estimation method in the second OFDM symbol processing is to use the interference party channel ratio of the first OFDM symbol:

[0029] ;

[0030] Constraint condition: , ;

[0031] , ​​respectively represent the first and second OFDM source signal channels;

[0032] The method selects the channel of the previous OFDM symbol sent by the sender closest to the .

[0033] Further, the pre-filtering method for the pilot part in the first OFDM symbol processing is as follows:

[0034] The pilot received signal is sparsely decomposed by using a pre-constructed overcomplete dictionary; the absolute values of the decomposed coefficients are threshold processed, and those lower than a threshold Thresh are set to 0, and otherwise, are retained; the processed coefficients are used for inverse transformation to obtain the filtered pilot received signal.

[0035] The second aspect of the application provides a computer readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform any of the methods described above.

[0036] The third aspect of the application provides a computing device, including:

[0037] One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for performing any of the methods described above.

[0038] Compared with the prior art, the application has the following characteristics and advantages:

[0039] The application proposes a channel alternating estimation based airspace anti-interference method for the anti-interference problem of the flight ad hoc network. Based on the basic principle of airspace filtering, the airspace filtering is carried out through the alternating iterative estimation of the sender channel and the interference channel, and the required signal is effectively recovered. The simulation results show that the proposed method has superior anti-interference performance, can greatly reduce the bit error rate under strong interference attack, and guarantees the transmission reliability. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The figure is a flowchart of the application;

[0041] Figure 2 The figure is a basic structure diagram of the OFDM symbol in the application;

[0042] Figure 3 The figure is a spatial interference model diagram of 1*2 MIMO communication. DETAILED DESCRIPTION

[0043] This invention relates to the field of intelligent unmanned equipment platforms and technologies, specifically communication systems and signal processing, and particularly to anti-interference techniques and related algorithms based on spatial filtering in the operation of flight ad hoc network systems. It addresses, to a certain extent, the issues of anti-interference effectiveness and transmission reliability in flight ad hoc networks under interference attacks.

[0044] The following description, in conjunction with the accompanying drawings, further illustrates the anti-interference technology for flight ad hoc networks based on spatial filtering according to the present invention.

[0045] 1. Spatial Domain Filtering Criteria

[0046] 1) OFDM symbol structure

[0047] like Figure 2 As shown, the simplest OFDM symbol structure can be divided into two parts: preamble and data. Since both the preamble transmission and reception are known, it is typically used for channel information estimation. The data part can be recovered using the channel information estimated from the preamble.

[0048] 2) Basic Principles of MIMO Spatial Filtering

[0049] like Figure 3 As shown, consider a 1*2 MIMO communication model between the transmitter and receiver, in order to... Represents the signal transmitted from the sending end, where, Indicates the source signal being sent. The interference signal, after being transmitted through channel H, is represented by the following signal at the receiver:

[0050] (1)

[0051] In order to obtain a pure source signal Spatial filtering technology aims to transform the received signal y into a form perpendicular to the x-axis. In the signal subspace, for example, The following projection signals can be obtained:

[0052] (2)

[0053] Channel coefficients are an indispensable factor in decoding, and the corresponding channel estimation process can be performed using known symbols transmitted by the transmitter. For the channel coefficients of the interference source, since there is no need to decode the interference signal, their precise values ​​are not required; however, understanding the direction of the interference signal is essential.

[0054] Divide both sides of the equation by The estimated transmitted signal can be obtained as follows:

[0055] (3)

[0056] It is obvious that the channel information of both the transmitter and the interferer needs to be estimated and tracked.

[0057] From equation (3), it can be seen that the interference channel estimation is needed. As mentioned above, for the channel coefficients of the interferer, since there is no need to decode the interference signal, the exact value is not needed, only the direction of the interference, that is, the estimation of .

[0058] However, the estimation of the transmitter channel is necessary.

[0059] 2. As shown in FIG. 2, the spatial interference rejection method based on channel alternately estimation Figure 1

[0060] A. The first OFDM symbol processing:

[0061] 1) Pilot processing: pre-filtering + transmitter channel estimation.

[0062] Pre-filtering: using the constructed overcomplete dictionary, the pilot received signal is sparsely decomposed; then the absolute values of the decomposed coefficients are thresholded, those below the threshold Thresh are set to 0, otherwise, they are kept (through a large number of experiments, the threshold Thresh is taken as 0.5); finally, using the processed coefficients, the inverse transform is performed to obtain the filtered pilot received signal.

[0063] Transmitter channel estimation: using the pre-filtered pilot received signal, the input and output are known, and the classic channel estimation method is used for channel estimation, which will not be described here.

[0064] 2) Data processing:

[0065] Interferer channel ratio estimation: here, we choose to use to approximately replace the channel ratio of the interferer , where denotes the symbol number, and denotes the subcarrier number. Here, the main consideration is that the power of the interference signal is usually much larger than that of the transmitter signal, and in this case, a large number of simulations and practices have proved that the influence of the received signal can be ignored to a certain extent, that is, using the ratio of the two signals to approximately replace the channel ratio of the interferer is relatively feasible. However, in order to minimize the estimation error, a certain smoothing processing needs to be performed on , as follows:

[0066]

[0067] Here, K is usually taken as 3 around the subcarrier k ​5 subcarriers. That is, 3 5 subcarriers Adding average, can reduce the error influence in channel estimation.

[0068] Spatial filtering: using the known sender channel estimation and interference channel estimation ratio, according to formula (3) on the received signal filtering processing can be.

[0069] B. The second OFDM symbol processing:

[0070] 1) pilot processing:

[0071] Sender channel estimation: here, using the interference channel ratio of the previous OFDM symbol , known input and output, can be derived according to the following method to estimate the sender channel .

[0072] According to formula (3), at this time, , , are known, but still can not be uniquely determined. This patent is determined according to the following principles , the principle is as follows:

[0073]

[0074] Constraint: , , , , are known

[0075] that is, according to the above principle to select the closest to the previous OFDM symbol sender channel.

[0076] 2) data processing:

[0077] Interference channel ratio estimation: here, still using the method of using the ratio of two smoothed signals to approximate the interference channel ratio.

[0078] Spatial filtering: using the known sender channel estimation and interference channel estimation ratio, according to formula (3) on the received signal filtering processing can be.

[0079] C. The third OFDM symbol processing:

[0080] 1) pilot processing:

[0081] Interference channel ratio estimation: here, using the sender channel , known input and output, the interference channel ratio value can be deduced The specific method is as follows.

[0082] After the interference is detected, the pilot signal receiving end receiving signal is recovered by using the known pilot signal and the known sending channel estimation, and the interference receiving signal of the receiving end is obtained by subtracting the mixed signal, and then the interference channel estimation ratio is calculated.

[0083] 2) Data processing:

[0084] Spatial domain filtering: the receiving signal is filtered according to formula (3) by using the known sending channel estimation of the last symbol and the interference channel estimation ratio of the current symbol.

[0085] D. Fourth OFDM symbol processing:

[0086] 1) Pilot processing:

[0087] Sending channel estimation: here, the interference channel ratio estimation of the last OFDM symbol is used , known input and output, the sending channel can be deduced , the determination principle is still to select the closest to the sending channel of the last OFDM symbol , which will not be repeated here.

[0088] 2) Data processing:

[0089] Spatial domain filtering: the receiving signal is filtered according to formula (3) by using the known sending channel estimation of the current symbol and the interference channel estimation ratio of the last symbol.

[0090] E. Remaining OFDM symbol processing:

[0091] The third and fourth OFDM symbol processing processes are repeated in turn until all OFDM symbols are processed.

[0092] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should be considered as the protection scope of the present application.

[0093] A computer readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to perform a flight ad hoc network spatial domain anti-interference method based on channel alternating estimation.

[0094] A computing device comprising one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, the one or more programs including instructions for performing a channel-alternating-estimation-based flight ad hoc network airspace jamming method.

[0095] Those skilled in the art will appreciate that embodiments of the application can be devised for a method, a system, or a computer program product. Accordingly, the present application can be embodied in the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0096] The present application is described in reference to the flowchart and / or block diagrams of the method, apparatus (system) and computer program product according to embodiments of the application. It is understood that each block of the flowchart and / or block diagrams, and combinations of blocks in the flowchart and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processing system or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 means for performing one or more functions specified in the flowchart and / or block diagram block or blocks.

[0097] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 means for performing one or more functions specified in the flowchart and / or block diagram block or blocks.

[0098] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart and / or block diagram block or blocks. Figure 1 one or more functions specified in the flowchart and / or block diagram block or blocks. Figure 1 means for performing one or more functions specified in the flowchart and / or block diagram block or blocks.

[0099] The above merely illustrates the embodiments of the present application, but should not be taken as limitations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall fall into the protection scope of the present application.

Claims

1. A method for airspace interference mitigation in ad hoc flight networks based on channel alternation estimation, characterized in that, include: A 1x2 MIMO communication model is constructed between the transmitter and receiver transmitting OFDM signals; The OFDM signal is divided into several OFDM symbols, and each OFDM symbol is divided into a pilot part and a data part; The first OFDM symbol processing: the pilot section is pre-filtered, and the filtered pilot received signal is used to estimate the transmitter channel; the data section is used to estimate the interfering channel ratio. The second OFDM symbol processing: The pilot section uses the interfering channel ratio of the first OFDM symbol to derive the transmitting channel; the data section uses the smoothed ratio of the two signals to replace the interfering channel ratio, and performs spatial filtering using the known transmitting and interfering channel ratios of this symbol. The third OFDM symbol processing: The pilot section uses the transmitter channel of the second OFDM symbol to derive the interfering channel ratio. After detecting interference, it uses the known pilot signal and the known transmitter channel to recover the received signal of the pilot signal receiver. The received signal of the receiver is subtracted from the mixed signal to obtain the receiver's interfering received signal, and the interfering channel ratio is calculated. The data section uses the transmitter channel of the second OFDM symbol and the interfering channel ratio of this symbol to perform spatial filtering. The fourth OFDM symbol is processed as follows: the pilot section uses the interfering channel ratio of the third OFDM symbol to deduce the transmitter channel; spatial filtering is performed using the known transmitter channel of this symbol and the interfering channel ratio of the third OFDM symbol. The remaining OFDM symbols are processed alternately for the third and fourth OFDM symbols until all OFDM symbols have been processed and the required signal is recovered.

2. The method for airspace interference mitigation in ad hoc networks based on channel alternation estimation according to claim 1, characterized in that, The 1*2 MIMO communication model is based on Represents the signal transmitted from the sending end, where, Indicates the source signal being sent. Indicates interference signal. It is a 2x2 channel matrix, including the source signal channel and the interference channel. The received signal, after being transmitted through channel H, is represented at the receiver as follows: 。 3. The method for airspace interference mitigation in ad hoc networks based on channel alternation estimation according to claim 2, characterized in that, The spatial filtering method is to transform the received signal y to a state perpendicular to the x-axis. In the signal subspace, The obtained projection signal: ; Divide both sides of the equation by The transmitted signal is: 。 4. The method for airspace interference mitigation in ad hoc networks based on channel alternation estimation according to claim 2, characterized in that, The method for estimating the interfering party's channel ratio in the first OFDM symbol processing is as follows: use Alternate interference channel ratio , Indicates symbol number, Indicates the subcarrier number.

5. The method for airspace interference mitigation in ad hoc networks based on channel alternation estimation according to claim 4, characterized in that, Also includes the Perform smoothing: ； K is approximately 3 times the value of subcarrier k. Five subcarriers, with subcarrier k around 3 The 5 subcarriers correspond to The summation and averaging reduce the impact of errors in channel estimation.

6. The method for airspace anti-interference of ad hoc networks based on channel alternation estimation according to claim 4, characterized in that, The transmitter channel estimation method in the second OFDM symbol processing is as follows: using the interfering channel ratio of the first OFDM symbol. ; ； Constraints: , ; , These represent the source signal channels of the first and second OFDM, respectively; Select the transmitter channel closest to the previous OFDM symbol .

7. The method for airspace anti-interference of ad hoc networks based on channel alternation estimation according to claim 1, characterized in that, The pre-filtering method for the pilot section in the first OFDM symbol processing is as follows: The pilot received signal is sparsely decomposed using a pre-constructed overcomplete dictionary; then the absolute values ​​of the decomposed coefficients are thresholded, with those below the threshold Thresh set to 0, and those above the threshold retained; the processed coefficients are then used for inverse transformation to obtain the filtered pilot received signal.

8. A computer-readable storage medium for storing one or more programs, characterized in that: The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods according to claims 1 to 7.

9. A computing device, characterized in that, include: One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, the one or more programs including instructions for performing any of the methods according to claims 1 to 7.

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