A method for eliminating secondary cooperative jamming of a whirling electromagnetic wave mode

Abstract

This invention discloses a method for canceling secondary cooperative interference of vortex electromagnetic wave modes, comprising: the transmitter selecting a primary OAM mode and a secondary OAM mode; based on a set of keys and real-time times defined by the transmitter and receiver respectively, the transmitter generating a secondary cooperative transformation sequence of modes, and based on the secondary cooperative transformation sequence, dividing the input binary information bits into OAM mode index information bits and signal modulation bits, and jointly designing the positional distribution of the two in the information frame structure; after determining the G secondary cooperative transformation OAM modes activated in each hop, the transmitter loading the G secondary cooperative transformation OAM modes carrying constellation point symbols onto each element of the antenna, and transmitting the resulting G mutually orthogonal vortex electromagnetic wave mode secondary cooperative transformation signals to the receiver; the receiver performing detransformation and interference signal cancellation on the received signal, and estimating the signal vector by searching for constellation point symbols, thereby effectively improving spectral efficiency and enhancing anti-interference capability.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, specifically relating to a method for eliminating secondary cooperative interference of vortex electromagnetic wave modes. Background Technology

[0002] Reliable information transmission is a multiplier for improving the efficiency of modern wireless communication. Frequency hopping communication, with its strong anti-interference, low interception, and anti-fading advantages, is widely used in wireless communication. However, with the increasing complexity of interference environments and the diversification and integration of equipment, the currently mature frequency hopping technology faces a severe contradiction between anti-interference capabilities and limited spectrum resources, making it difficult to significantly improve the anti-interference capability of wireless communication. Therefore, it is urgent to delve deeper into the physical characteristics of radio electromagnetic waves and explore new anti-interference technologies to meet the pressing needs of wireless communication for strong information attack and defense.

[0003] Compared to linear angular momentum, which has been extensively explored to describe beam polarization, research on orbital angular momentum (OAM), describing the spiral phase front of electromagnetic waves, is still in its early stages. Electromagnetic waves carrying orbital angular momentum are called vortex electromagnetic waves. The project "Utilization of photon orbital angular momentum in the Low-frequency Radio domain" introduces OAM into the microwave band, and simulations have verified that vortex electromagnetic waves can be generated through phased array antennas, pioneering its application in wireless communication. In ideal line-of-sight wireless communication scenarios, the orthogonality between OAM modes can theoretically provide an infinite number of orthogonal channels for wireless communication. Therefore, vortex electromagnetic waves possess significant potential for anti-interference, low interception, and covert transmission without sacrificing spectrum resources.

[0004] In related technologies, all OAM modes are used for information transmission, and the security rate of a multimode vortex electromagnetic wave wireless communication system is calculated. It is assumed that the eavesdropper uses a uniform circular array with the same number of elements to obtain legitimate information and also uses Fourier transform to solve the information. However, the disadvantage of this method is that the security rate is limited and it does not have anti-interference performance.

[0005] Related technologies also propose a mode-hopping anti-interference method for vortex electromagnetic waves. The main idea is that the transmitting end quickly selects the hopping mode order based on the mode-hopping sequence. Based on the pre-shared key between the cooperating transceivers, and utilizing inter-mode orthogonality, the cooperating receiver can quickly decode the mode, achieving efficient interference suppression. This method extends anti-interference methods from the traditional frequency domain to the two-dimensional mode-frequency domain, enriching the diversity of signal transmission carriers for cooperating parties, significantly reducing the probability of interference, and improving the anti-interference performance of wireless communication.

[0006] Another related technology is an index-modulated vortex electromagnetic wave anti-interference method. This method utilizes index modulation information to select hopping vortex electromagnetic wave mode groups, achieving signal diversity and multiplexing transmission. With highly synchronized cooperative transceivers and shared keys, the receiver can quickly determine the mode group for cooperative communication and suppress interference through Fourier transform. The main innovations of this method are, on the one hand, improving spectral efficiency by utilizing subthreshold capacity to meet the information exchange needs of various devices; and on the other hand, enhancing the anti-interference capability of wireless communication by utilizing fast mode hopping.

[0007] However, the aforementioned vortex wave electromagnetic wave anti-interference method has a drawback: plane wave interference can cause a certain degree of intra-mode crosstalk to the signal received by the cooperative receiver, resulting in a slightly insufficient ability to resist strong interference. Therefore, how to utilize vortex electromagnetic wave modal signals to solve the above problems and achieve high spectral efficiency is an urgent technical challenge to be addressed. Summary of the Invention

[0008] To address the aforementioned problems in the prior art, this invention provides a method for eliminating secondary cooperative interference of vortex electromagnetic wave modes. The technical problem to be solved by this invention is achieved through the following technical solution:

[0009] This invention provides a method for canceling secondary cooperative interference of vortex electromagnetic wave modes, applied to a wireless communication anti-interference system, the wireless communication anti-interference system including a transmitter and a receiver; the method includes:

[0010] For each hop, the transmitter selects a primary OAM mode and a secondary OAM mode from N mutually orthogonal orbital angular momentum (OAM) modes that can be generated simultaneously.

[0011] Based on a set of keys and real-time data defined by the sender and receiver respectively, the sender generates a modal second-order cooperative transformation sequence consisting of a primary mode-hopping basis sequence and a secondary multimodal mode-hopping basis sequence.

[0012] Based on the modal secondary cooperative transform sequence, the transmitting end divides the input binary information bits into OAM modal index information bits and signal modulation bits, and jointly designs the positional distribution of the OAM modal index information bits and the signal modulation bits in the information frame structure;

[0013] After the transmitter determines the G quadratic cooperative transformation OAM modes activated in each hop from multiple OAM mode groups, each quadratic cooperative transformation OAM mode carries a constellation point symbol.

[0014] The transmitting end loads G quadratic cooperative transformation OAM modes carrying constellation point symbols onto each element of the antenna, and transmits the resulting G mutually orthogonal vortex electromagnetic wave mode quadratic cooperative transformation signals to the receiving end.

[0015] The receiver performs demodulation and interference cancellation on the received signal, and estimates the signal vector by searching for constellation point symbols.

[0016] In one embodiment of the present invention, the step of the transmitting end selecting a primary OAM mode and a secondary OAM mode from N mutually orthogonal orbital angular momentum (OAM) modes that can be generated simultaneously per hop includes:

[0017] For each hop, the transmitter selects one OAM mode as the primary OAM mode from N mutually orthogonal OAM modes that can be generated simultaneously, and selects G non-zero OAM modes as secondary OAM modes.

[0018] In one embodiment of the present invention, the step of the transmitter generating a modal secondary cooperative transform sequence composed of a primary mode-hopping base sequence and a secondary multimodal mode-hopping base sequence, based on a set of keys and real-time times defined by the transmitter and receiver respectively, includes:

[0019] Both the sending and receiving ends define their own set of keys and real-time values.

[0020] The sending end uses the key from one of the groups as the encryption key for the primary OAM mode, and encrypts it using the real-time data from that group as plaintext, to obtain the primary hopping mode base sequence Ω1 = {c t ,t=1,2,3,…},c t This represents the primary hopping mode basis sequence generated at time t;

[0021] The sending end uses the key from another set as the encryption key for the secondary OAM mode, and encrypts it using the real-time data from that set as plaintext, to obtain the secondary multimodal hopping mode base sequence Ω2={a t ,t=1,2,3,…},a t This represents the secondary hopping mode basis sequence generated at time t;

[0022] The transmitting end combines the primary mode-hopping base sequence with the secondary multimodal mode-hopping base sequence to obtain the modal second-order cooperative transformation sequence.

[0023] In one embodiment of the present invention, after the transmitting end determines the G quadratic cooperative transform OAM modes activated per hop from a plurality of OAM mode groups, the step of enabling each quadratic cooperative transform OAM mode to carry a constellation point symbol includes:

[0024] The sending end starts from 2 a From a set of OAM modes, the quadratic cooperative transformation combination of each hop activated OAM modes is selected to obtain G quadratic cooperative transformation modes activated at each hop, where, Indicates rounding down. This indicates the selection of G binomial coefficients from N-1;

[0025] The transmitting end uses the signal modulation bits to perform M-order signal modulation, mapping each log2M information bits to a constellation point symbol;

[0026] The transmitter loads each constellation point symbol onto G quadratic cooperative transformation OAM modes, so that each quadratic cooperative transformation OAM mode carries a constellation point symbol.

[0027] In one embodiment of the present invention, the g-th quadratic cooperative transformation OAM mode carrying constellation point symbols is: Among them, s g This represents the constellation point symbol loaded on the g-th quadratic cooperative transformation OAM mode, 1≤g≤G, j represents the imaginary unit, l s Indicates the selected primary OAM mode, l g This indicates the selected g-th secondary OAM mode.

[0028] In one embodiment of the present invention, the step of the transmitting end loading G quadratic cooperative transformation (OAM) modes carrying constellation point symbols onto each element of the antenna, and transmitting the resulting G mutually orthogonal vortex electromagnetic wave mode quadratic cooperative transformation signals to the receiving end includes:

[0029] The transmitting end loads G quadratic cooperative transformation (OAM) modes carrying constellation point symbols onto all elements of the uniform circular array antenna, generating G mutually orthogonal vortex electromagnetic wave mode quadratic cooperative transformation signals, and further transmits the G mutually orthogonal vortex electromagnetic wave mode quadratic cooperative transformation signals to the receiving end.

[0030] In one embodiment of the present invention, the steps of the receiving end performing demodulation and interference cancellation on the received signal, and estimating the signal vector by searching constellation point symbols, include:

[0031] The receiving end performs demodulation and interference cancellation on the received signal y to obtain signal y. l Further, a search is conducted for all constellation point symbols S of the M-order signal modulation to estimate the signal vector.

[0032] In one embodiment of the present invention, the receiving end performs demodulation and interference cancellation on the received signal y according to the following steps:

[0033] The receiving end performs a Fourier transform on the received signal y to obtain the signal.

[0034]

[0035] In the formula, F +This represents the Fourier transform operator, the signal It is an N-dimensional column vector, including the G terms expected by the receiver and the non-expected (NG) terms;

[0036] The receiving end extracts the corresponding signal based on the modal second-order cooperative transform sequence. The G terms yield a signal of dimension G.

[0037] The receiver processes the signal according to the primary OAM mode selected by the transmitter. The gth term Perform primary mode transformation to obtain signal y g :

[0038]

[0039] The receiving end will transmit signal y g The interference signal in the signal approximates zero, resulting in signal y. l =[y1,y2,…y g ,…y G ].

[0040] In one embodiment of the present invention, the signal vector estimated by the receiving end is:

[0041]

[0042] In the formula, f(y) l |H) represents the signal y when the transmission channel matrix is ​​H. l The probability density function is given by s, where s represents the modulated signal vector transmitted by the transmitter.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] Faced with strong, wide-bandgap interference, existing frequency hopping techniques have a very limited range of selectable frequencies, and more likely, all selectable frequencies will be covered by interference, making it difficult to exert anti-interference capabilities and significantly reducing wireless communication quality. In contrast, this invention fully utilizes the orthogonal resource of OAM modes, which is completely independent of the frequency domain, for deliberate interference suppression, allowing inter-frequency interference to be suppressed using conventional methods such as bandpass filters. Simultaneously, this invention constructs a new orthogonal phase factor for signal transmission by performing a second-order co-transformation of modes at the transmitting end, and rapidly hopping to the selected OAM mode group reduces the probability of being tracked by vortex electromagnetic wave interference. After the second-order co-transformation of modes is solved by a two-dimensional Fourier transform at the receiving end, co-frequency interference can be adaptively reduced to zero, achieving deep protection of the cyber-physical layer mode domain.

[0045] Furthermore, this invention introduces OAM mode index information bits to determine the selected mode secondary cooperative transform group for each hop. The number of bits in this information portion determines the increased subthreshold capacity of wireless communication. On the other hand, this invention utilizes the selection of multiple secondary modes for information transmission, achieving signal multiplexing and enabling the transmission of multiple different information streams, thereby improving spectral efficiency. Therefore, the spectral efficiency of this invention is the sum of the subthreshold capacity and the spectral efficiency achievable through signal multiplexing, significantly higher than the spectral efficiency of existing technologies.

[0046] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0047] Figure 1 This is a flowchart illustrating the method for eliminating secondary cooperative interference of vortex electromagnetic wave modes provided in an embodiment of the present invention.

[0048] Figure 2 This is a comparative schematic diagram showing the change in communication capacity with the number of activated OAM modes provided in an embodiment of the present invention;

[0049] Figure 3 This is a schematic diagram of bit error rate comparison provided in an embodiment of the present invention. Detailed Implementation

[0050] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0051] Figure 1 This is a flowchart illustrating the vortex electromagnetic wave mode secondary cooperative interference cancellation method provided in an embodiment of the present invention. Figure 1 As shown, this embodiment of the invention provides a method for eliminating secondary cooperative interference of vortex electromagnetic wave modes, applied to a wireless communication anti-interference system. The wireless communication anti-interference system includes a transmitter and a receiver; the method includes:

[0052] S1. For each hop, the transmitter selects the primary OAM mode and the secondary OAM mode from N mutually orthogonal orbital angular momentum OAM modes that can be generated simultaneously.

[0053] S2. Based on a set of keys and real-time data defined by the sender and receiver respectively, the sender generates a modal second-order cooperative transformation sequence consisting of a primary mode-hopping basis sequence and a secondary multimodal mode-hopping basis sequence.

[0054] S3. Based on the modal secondary cooperative transform sequence, the transmitting end divides the input binary information bits into OAM modal index information bits and signal modulation bits, and jointly designs the positional distribution of OAM modal index information bits and signal modulation bits in the information frame structure; the OAM modal index information bits include primary OAM modal index information and secondary OAM modal index information;

[0055] S4. After the transmitter determines the G quadratic cooperative transformation OAM modes activated in each hop from multiple OAM mode groups, each quadratic cooperative transformation OAM mode carries a constellation point symbol.

[0056] S5. The transmitting end loads G secondary cooperative transformation OAM modes carrying constellation point symbols onto each element of the antenna, and transmits the resulting G mutually orthogonal vortex electromagnetic wave mode secondary cooperative transformation signals to the receiving end.

[0057] S6. The receiving end performs demodulation and interference cancellation on the received signal, and estimates the signal vector by searching for constellation point symbols.

[0058] It should be understood that electromagnetic waves with a spiral phase front are called vortex electromagnetic waves. Because the enemy's jamming transmitting antenna and the cooperative receiving antenna are misaligned, the jamming signal transmitted in the form of a plane electromagnetic wave / vortex electromagnetic wave will disrupt the intermodal orthogonality of the cooperative receiving antenna, causing severe intramodal interference and thus degrading the quality of wireless communication. Therefore, it is necessary to design a secondary cooperative mode transformation method for vortex electromagnetic waves to determine the vortex electromagnetic wave mode at each transition, providing a technical basis for subsequent interference zeroing processing.

[0059] Optionally, in step S1, the step of the transmitting end selecting the primary OAM mode and the secondary OAM mode from N mutually orthogonal orbital angular momentum OAM modes that can be generated simultaneously in each hop includes:

[0060] For each hop, the transmitter selects one OAM mode as the primary OAM mode from N mutually orthogonal OAM modes that can be generated simultaneously, and selects G non-zero OAM modes as secondary OAM modes.

[0061] Since the multiplexing and demultiplexing of vortex electromagnetic wave signals are involved, the cooperative transceiver in this invention can generate multiple mutually orthogonal vortex electromagnetic beams through multiple spiral phase plates, single-antenna fused metasurfaces, uniform circular array cooperative metasurfaces, and multi-concentric circular arrays. Specifically, the cooperative transmitter can generate a maximum of N OAM modes simultaneously. Based on a pre-shared mode-hopping sequence, the cooperative transmitter rapidly switches between OAM modes. In this invention, for each hop, the cooperative transmitter first selects one OAM mode from the N OAM modes as the primary OAM mode for secondary cooperative transformation with the secondary mode. Then, the cooperative transmitter selects G from the N-1 non-zero OAM modes as secondary OAM modes for information multiplexing and transmission. The remaining (NG) OAM modes are defaulted to a non-working state and do not transmit any information.

[0062] It should be noted that in the primary OAM mode selection process, each OAM mode has the same probability of being selected, while in the secondary OAM mode selection process, each non-zero OAM mode has the same probability of being selected.

[0063] Optionally, in step S2, the step of the transmitter generating a modal secondary cooperative transform sequence composed of a primary mode-hopping basis sequence and a secondary multimodal mode-hopping basis sequence, based on a set of keys and real-time times defined by the transmitter and receiver respectively, includes:

[0064] S201. The sending end and the receiving end each define a set of keys and real-time times;

[0065] S202. The sending end uses the key from one of the groups as the encryption key for the primary OAM mode, and encrypts it using the real-time data from that group as plaintext, to obtain the primary hopping mode base sequence Ω1 = {c t ,t=1,2,3,…},c t This represents the primary hopping mode basis sequence generated at time t;

[0066] S203. The sending end uses the key from another group as the encryption key for the secondary OAM mode, and encrypts it using the real-time data from that group as plaintext, to obtain the secondary multimodal mode hopping basis sequence Ω2={a t ,t=1,2,3,…},a t This represents the secondary hopping mode basis sequence generated at time t;

[0067] S204. The transmitting end combines the primary mode-hopping base sequence and the secondary multi-mode mode-hopping base sequence to obtain the mode-secondary cooperative transformation sequence.

[0068] Specifically, in step S2, the two sets of keys and the real-time time defined by the vortex electromagnetic wave cooperating transceiver are used as the encryption key and plaintext, respectively. Based on the "confusion" and "diffusion" criteria proposed in the cryptographic design, one set of keys is used as the encryption key for the primary OAM mode. The plaintext in this set is then subjected to iterative group encryption to generate the secondary mode-hopping base sequence Ω1={c t ,t=1,2,3,…},c t Let c be the primary hopping mode basis sequence generated at time t. t All modes correspond one-to-one with the vortex electromagnetic wave anti-interference communication system.

[0069] Furthermore, another set of keys is used as the encryption key for the secondary OAM mode. The plaintext in this set is then subjected to block encryption iterations to generate the secondary multimodal hopping mode base sequence Ω2={a t,t=1,2,3,…}, where the zero mode is in a non-working state. It should be noted that the keys involved in generating the primary hopping mode basis sequence and the secondary hopping mode basis sequence can be the same or different.

[0070] Finally, the primary hopping mode basis sequence and the secondary hopping mode basis sequence are combined to generate a second-order cooperative transformation sequence of vortex electromagnetic wave modes.

[0071] Optionally, in step S4, after the transmitting end determines the G quadratic cooperative transform OAM modes activated per hop from multiple OAM mode groups, the step of making each quadratic cooperative transform OAM mode carry a constellation point symbol includes:

[0072] S401, the transmitting end starts from 2 a From a set of OAM modes, the quadratic cooperative transformation combination of each hop activated OAM modes is selected to obtain G quadratic cooperative transformation modes activated at each hop, where, Indicates rounding down. This indicates the selection of G binomial coefficients from N-1;

[0073] S402. The transmitting end uses signal modulation bits to perform M-order signal modulation, mapping each log2M information bits to a constellation point symbol.

[0074] S403. The transmitting end loads each constellation point symbol onto the G quadratic cooperative transformation OAM modes respectively, so that each quadratic cooperative transformation OAM mode carries a constellation point symbol.

[0075] In this embodiment, the cooperative sending end first starts from 2 a In a set of OAM modes, a combination of quadratic cooperative transforms (QCTs) of OAM modes activated at each hop is selected, i.e., G quadratic cooperative transform OAM modes. Then, M-order signal modulation is performed using signal modulation bits, mapping each log2M information bits to a constellation point symbol. Based on the multiplexing transmission of the G OAM modes, each quadratic cooperative transform OAM mode carries one constellation point symbol, resulting in an input binary information bit set of Glog2M. For example, the total number of binary information bits η input per hop at the cooperative transmitter is:

[0076]

[0077] Furthermore, mode hopping is achieved through constellation point symbol modal loading: constellation point symbols are loaded onto G quadratic cooperative transform OAM modes respectively to obtain the g-th quadratic cooperative transform OAM mode signal. In this embodiment, the g-th quadratic cooperative transform OAM mode carrying constellation point symbols is... Among them, s gThis represents the constellation point symbol loaded on the g-th quadratic cooperative transformation OAM mode, 1≤g≤G, j represents the imaginary unit, l s Indicates the selected primary OAM mode, l g This indicates the selected g-th secondary OAM mode.

[0078] Optionally, in step S5, the transmitting end loads G quadratic cooperative transformation (OAM) modes carrying constellation point symbols onto each element of the antenna, and transmits the resulting G mutually orthogonal vortex electromagnetic wave mode quadratic cooperative transformation signals to the receiving end, so that the receiving end can estimate the signal vector, including:

[0079] S501. The transmitting end loads G secondary cooperative transformation OAM modes carrying constellation point symbols onto all array elements of the uniform circular array antenna, generating G mutually orthogonal vortex electromagnetic wave mode secondary cooperative transformation signals.

[0080] S502. The transmitting end loads G secondary cooperative transformation OAM modes carrying constellation point symbols onto all array elements of the uniform circular array antenna, generating G mutually orthogonal vortex electromagnetic wave mode secondary cooperative transformation signals, and further transmits G mutually orthogonal vortex electromagnetic wave mode secondary cooperative transformation signals to the receiving end.

[0081] Specifically, the transmitting end loads G quadratic cooperative transformation (OAM) modes carrying constellation point symbols onto all elements of the uniform circular array antenna. The transmitted signal on the nth transmitting element can be expressed as... G mutually orthogonal vortex electromagnetic wave mode secondary cooperative transformation signals are generated to realize the simultaneous transition of G OAM mode secondary cooperative transformation signals, where 1≤g≤G.

[0082] It should be noted that since non-strict alignment at the cooperative transceiver ends will lead to severe inter-mode crosstalk, this invention performs beamforming at the cooperative transceiver ends to construct an approximate cyclic matrix, thereby reducing inter-mode crosstalk and ultimately obtaining the received signal y from the uniform circular array. When G mutually orthogonal vortex electromagnetic wave mode secondary cooperative transformation signals are transmitted through a sparse multipath channel, inter-mode crosstalk caused by sparse multipath transmission can be eliminated by means of phase compensation, ray tracing, or orthogonal frequency division multiplexing, and ultimately obtaining the received signal y from the uniform circular array.

[0083] Therefore, this example adopts, but is not limited to, the scenario of strictly aligned uniform circular arrays for cooperative transceiver transmission and line-of-sight channel transmission.

[0084] Further, in step S6, the receiving end performs demodulation and interference cancellation on the received signal, and estimates the signal vector by searching constellation point symbols, including:

[0085] The receiving end performs demodulation and interference cancellation on the received signal y to obtain signal y. l Further searching for all constellation point symbols S of the M-order signal modulation yields the estimated signal vector.

[0086] Specifically, the receiving end performs demodulation and interference cancellation on the received signal y according to the following steps:

[0087] The receiving end performs a Fourier transform on the received signal y to obtain the signal.

[0088]

[0089] In the formula, F + This represents the Fourier transform operator, signal It is an N-dimensional column vector, including the G terms expected by the receiver and the non-expected (NG) terms;

[0090] The receiver extracts the signal based on the modal second-order cooperative transform sequence. The G terms yield a signal of dimension G.

[0091] The receiver processes the signal according to the primary OAM mode selected by the transmitter. The gth term Perform primary mode transformation to obtain signal y g :

[0092]

[0093] The receiving end will transmit signal y g The interference signal in the signal approximates zero, resulting in signal y. l =[y1,y2,…y g ,…y G ].

[0094] In this embodiment, the receiver first utilizes modal orthogonality to perform a Fourier transform on the received signal y to obtain the signal. It is expressed as follows:

[0095]

[0096] Among them, F + This represents the Fourier transform operator.

[0097] During the Fourier transform process, the receiver converts the received interference signal from a plane electromagnetic wave / vortex electromagnetic wave form into a plane electromagnetic wave. It should be noted that the resulting signal... It is an N-dimensional column vector containing G terms expected by the receiver and non-expected (NG) terms. Based on the explicit transmitter mode quadratic cooperative transform sequence, the receiver extracts the corresponding received signal. The G terms yield a signal of dimension G.

[0098] Next, define the signal. The g-th term is The receiver, based on the primary mode selected by the transmitter, performs... Perform primary mode transform processing to obtain signal y g :

[0099]

[0100] Since the primary mode did not select the zero mode, i.e., l s ≠0, solving the primary mode can adaptively reduce the interference signal to zero, thus obtaining the signal y. l =[y1,y2,…y g ,…y G ].

[0101] Because the transmitting and receiving ends are strictly synchronized, the receiving end can clearly identify the primary and secondary OAM modes activated by the transmitting end. This means it does not need to estimate the input OAM mode index information bits; instead, it can use maximum likelihood detection to estimate the transmitted symbols. By searching all signal constellation points S of the M-order signal modulation, the estimated signal vector can be obtained. as follows:

[0102]

[0103] In the formula, f(y) l |H) represents the signal y when the transmission channel matrix is ​​H. l The probability density function is given by s, where s represents the modulation signal vector transmitted by the transmitter, and S represents all constellation point symbols modulated by the M-order signal.

[0104] Finally, the joint boundary algorithm can be used to obtain P e The average bit error rate is represented as:

[0105]

[0106] In the formula, This indicates that the transmitted signal is s, but the estimated signal vector is... The pairwise error probability, This indicates that the transmitted signal is s, but the estimated signal vector is... The incident The number of bits transmitted incorrectly due to the occurrence, η s =Glog2M is the number of information modulation bits.

[0107] The following simulation experiment further illustrates the vortex electromagnetic wave mode secondary cooperative interference elimination method provided by this invention.

[0108] During the simulation, the signal modulation method is binary phase shift keying, the transmit power on each activated OAM mode is the same, the received interference signal is 2dB, the spacing between adjacent array elements on the cooperative transceiver uniform circular array antenna is the carrier wavelength, and the channel bandwidth is set to 15kHz.

[0109] Under the above conditions, the bit error rate and spectral efficiency of the vortex electromagnetic wave mode secondary cooperative interference cancellation method provided by the present invention, the existing vortex electromagnetic wave mode hopping anti-interference method, and the narrowband multiple-input multiple-output (MIMO) method are simulated.

[0110] Figure 2 This is a comparative schematic diagram showing the change in communication capacity with the number of active OAM modes provided in this embodiment of the invention. The spectral efficiency of the vortex electromagnetic wave mode secondary cooperative interference cancellation method provided by this invention, existing vortex electromagnetic wave mode-hopping anti-interference methods, and existing frequency-hopping anti-interference methods are compared. Spectral efficiency is equal to communication capacity divided by channel bandwidth. In the simulation, the total number of available OAM modes is assumed to be 16. Figure 2 As shown, with the increase of the number of activated OAM modes N, the communication capacity of this invention increases due to the increase in index information. The main reason for this phenomenon is that the vortex electromagnetic wave mode-hopping technology transmits messages only through information modulation. Furthermore, with the increase of the number of activated OAM modes, the communication capacity of this invention first rapidly increases to a maximum value and then decreases. When fewer OAM modes are activated for information transmission, the index information plays a dominant role in the total number of transmitted bits. When the number of OAM modes exceeds the maximum capacity, the increase in information modulation is less than the decrease in index information, resulting in a decrease in communication capacity. Due to the second-order cooperative mode transformation, the communication capacity of this invention is the highest among the three methods.

[0111] Figure 3 This is a schematic diagram comparing the BER (Bit Error Rate) provided in an embodiment of the present invention. The BER of the vortex electromagnetic wave mode secondary cooperative interference cancellation method provided by the present invention is compared with that of the MIMO method. In the simulation, the total number of available OAM modes is set to N = 16, i.e., the number of transmitting antenna array elements is 16. By observing the trend of the BER curve, it can be intuitively seen that the present invention has a lower BER. This is because the present invention not only has the lowest ratio of bit errors to total transmitted bits, but also successfully avoids interference attacks on useful signals.

[0112] The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples" indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0113] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for eliminating secondary cooperative interference of vortex electromagnetic wave modes, characterized in that, The method is applied to a wireless communication anti-interference system, the wireless communication anti-interference system including a transmitter and a receiver; the method includes: Each hop at the sending end can be generated simultaneously N Among the three mutually orthogonal orbital angular momentum (OAM) modes, the primary OAM mode and the secondary OAM mode are selected. Based on a set of keys and real-time data defined by the sender and receiver respectively, the sender generates a modal second-order cooperative transformation sequence consisting of a primary mode-hopping basis sequence and a secondary multimodal mode-hopping basis sequence. Based on the modal secondary cooperative transform sequence, the transmitting end divides the input binary information bits into OAM modal index information bits and signal modulation bits, and jointly designs the positional distribution of the OAM modal index information bits and the signal modulation bits in the information frame structure; The transmitter determines the active mode for each hop from multiple OAM mode groups. G After a quadratic cooperative transformation OAM mode, each quadratic cooperative transformation OAM mode carries a constellation point symbol; The sender will carry constellation dot symbols. G Each quadratic cooperative transformation (OAM) mode is loaded onto the antenna elements, and the resulting... G The mutually orthogonal vortex electromagnetic wave mode secondary cooperative transformation signal is transmitted to the receiving end; The receiving end performs demodulation and interference cancellation on the received signal, and estimates the signal vector by searching for constellation point symbols; Among them, each hop of the sending end can be generated simultaneously. N Among several mutually orthogonal orbital angular momentum (OAM) modes, the steps for selecting the primary and secondary OAM modes include: Each hop at the sending end can be generated simultaneously N From a set of mutually orthogonal OAM modes, select one OAM mode as the primary OAM mode, and then select... G Each non-zero OAM mode is used as a secondary OAM mode; The step of generating a modal secondary cooperative transform sequence composed of a primary mode-hopping basis sequence and a secondary multimodal mode-hopping basis sequence, based on a set of keys and real-time data defined by both the sender and receiver, includes: Both the sending and receiving ends define their own set of keys and real-time values. The sending end uses the key from one of the groups as the encryption key for the primary OAM mode, and encrypts it using the real-time data from that group as plaintext, to obtain the primary hopping mode base sequence Ω1 = { c t , t =1,2,3,…}, c t express t The primary hopping mode basis sequence generated at time t; The sending end uses the key from another set as the encryption key for the secondary OAM mode, and encrypts it using the real-time data from that set as plaintext, to obtain the secondary multimodal hopping mode base sequence Ω2 = { a t , t =1,2,3,…}, a t express t The secondary hopping mode basis sequence generated at time t; The transmitting end combines the primary mode-hopping base sequence with the secondary multimodal mode-hopping base sequence to obtain a second-order modal cooperative transformation sequence; The receiving end performs the following steps to receive the signal. y Perform detransformation and interference signal cancellation: The receiving end receives the signal. y Perform a Fourier transform to obtain the signal. : ； In the formula, This represents the Fourier transform operator, the signal for N A dimensional column vector, including the receiver's expected... G Items and unexpected ( N - G )item; The receiving end extracts the corresponding signal based on the modal second-order cooperative transform sequence. of G The item yields the dimension as G signal ; The receiver processes the signal according to the primary OAM mode selected by the transmitter. The g item Perform primary mode transformation to obtain the signal. y g : ； The receiving end will send the signal y g The interference signal in the signal is approximately zero, and the signal is obtained. y l =[ y 1, y 2,… y g ,… y G ].

2. The method for eliminating secondary cooperative interference of vortex electromagnetic wave modes according to claim 1, characterized in that, The transmitter determines the active mode for each hop from multiple OAM mode groups. G After generating a quadratic cooperative transformation OAM mode, the step of making each quadratic cooperative transformation OAM mode carry a constellation point symbol includes: From the sending end From a set of OAM modes, the quadratic cooperative transformation combination of each hop activated OAM modes is selected to obtain the each hop activated OAM mode. G There are 2 quadratic cooperative transformation modes, where... , Indicates rounding down. Indicates from N Select from -1 G Each binomial coefficient; The transmitting end uses the signal modulation bits to perform M Order-order signal modulation, each log2 M The information bits are mapped to a constellation dot symbol; The sending end loads the symbols of each constellation separately into... G On each of the quadratic cooperative transformation OAM modes, each quadratic cooperative transformation OAM mode carries a constellation point symbol.

3. The method for eliminating secondary cooperative interference of vortex electromagnetic wave modes according to claim 2, characterized in that, No. g The OAM modes of the quadratic cooperative transformation carrying constellation point symbols are: ,in, Indicates loading at the g Constellation point symbols on a quadratic cooperative transformation OAM mode, 1≤ g ≤ G , Represents the imaginary unit. This indicates the selected primary OAM mode. Indicates the selected first g Secondary OAM modes.

4. The method for eliminating secondary cooperative interference of vortex electromagnetic wave modes according to claim 1, characterized in that, The sender will carry constellation dot symbols. G Each quadratic cooperative transformation (OAM) mode is loaded onto the antenna elements, and the resulting... G The steps for transmitting mutually orthogonal vortex electromagnetic wave mode-second cooperative transformation signals to the receiving end include: The sender will carry constellation dot symbols. G A quadratic cooperative transformation OAM mode is applied to all elements of the uniform circular array antenna, generating G The mutually orthogonal vortex electromagnetic wave mode secondary cooperative transformation signal is further transmitted to the aforementioned... G The mutually orthogonal vortex electromagnetic wave modes undergo secondary cooperative transformation to the receiving end.

5. The method for eliminating secondary coordinated interference of vortex electromagnetic wave modes according to claim 4, characterized in that, The steps of the receiving end to perform demodulation and interference cancellation on the received signal, and to estimate the signal vector by searching for constellation point symbols, include: The receiving end receives the signal y After performing detransformation and interference signal cancellation, the signal y is obtained. l Further search M All constellation point symbols of the first-order signal modulation S The signal vector is estimated.

6. The method for eliminating secondary coordinated interference of vortex electromagnetic wave modes according to claim 5, characterized in that, The signal vector estimated by the receiver is: ； In the formula, This indicates that the signal y is in the case of a transmission channel matrix H. l The probability density function is given by s, where s represents the modulated signal vector transmitted by the transmitter.

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