An interference elimination method assisted by intelligent reflective surface

Abstract

The present invention proposes an interference cancellation method assisted by an intelligent reflective surface, belonging to the technical field of wireless communications. Based on the relative characteristics of direct interference and reflected interference experienced by a desired communication receiver, the present invention first treats the multipath reflected interference components from the intelligent reflective surface as one path of equivalent reflected interference at the desired communication receiver. The desired communication transmitter then uniformly adjusts the reflection coefficients of the multiple reflective units of the intelligent reflective surface so that the equivalent reflected interference experienced by the desired communication receiver can suppress the direct interference experienced directly from the interfering transmitter, thereby improving the spectrum efficiency of the desired communication receiver. The present invention does not require the desired communication pair to collaborate closely with the interfering transmitter to obtain information related to interference. Instead, the intelligent reflective surface can be used to effectively cancel interference, thereby reducing signaling overhead, lowering the complexity of the desired communication pair, and improving the communication quality of the desired communication pair.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communications, and in particular to an interference elimination method assisted by an intelligent reflective surface. Background Art

[0002] With the rapid development of wireless communication technology, the demand for data transmission continues to increase, resulting in a large number of users and data connections within a limited area. While technical personnel strive to find efficient ways to utilize resources, they also recognize that interference has become a major factor in degrading signal reception quality. Therefore, implementing effective interference management (IM) is crucial. Currently, most traditional interference management designs occur at both ends of the wireless link, passively adapting to the random, uncontrollable wireless propagation environment to suppress, eliminate, or modify interference. To overcome this limitation and create a more intelligent wireless signal propagation environment, the emerging intelligent reflecting surface (IRS) technology has emerged. IRS technology generates reflected signals on demand by controlling the amplitude and / or phase of wireless signals in the environment in real time, thereby dynamically configuring the signal propagation environment. The signal reflections from the IRS can achieve transmission enhancement and interference cancellation.

[0003] Currently, the industry's existing interference management technologies include: Existing Technology 1 [Z.Li, Y.Liu, KG Shin, J.Liu and Z.Yan, "Interference Steering to Manage Interference in IoT," IEEE Internet of Things Journal, vol. 6, no. 6, pp. 10458-10471, 2019] (Interference Steering in IoT Interference Management) leverages the interaction between wireless signals to design and send an additional steering signal at the desired transmitter. At the desired receiver, the interference steering signal and the harmful portion of the interference are inversely offset, thereby achieving interference-free reception of the desired signal at the desired receiver. This method consumes a limited amount of desired transmission power to generate the interference steering signal, resulting in a reduction in the power used for desired signal transmission. Furthermore, this method relies on a high degree of collaboration between transmitters, meaning that the desired transmitter needs to accurately obtain channel state information about the interfering transmitter and the data information carried by the interference. Prior Art 2 [P.Gu, C.Hua, W.Xu, R.Khatoun, Y.Wu and A.Serhrouchni, “Control Channel Anti-Jamming in Vehicular Networks via Cooperative Relay Beamforming,” IEEE Internet of Things Journal, vol.7, no.6, pp.5064-5077, 2020] (Anti-interference method for control channels in vehicular networks based on cooperative relay beamforming) In a vehicular network where a jammer equipped with a single antenna continuously interferes with the control channel, a multi-antenna roadside unit (RSU) sends control information to vehicles equipped with a single antenna via the control channel and selects the vehicle that successfully decodes the control information as a relay station. Multiple vehicle relay stations use cooperative beamforming technology to form a virtual antenna array and collaboratively serve the interfered vehicle on an interference-free traffic channel to mitigate the impact of the interference. This method can effectively solve the interference problem in vehicular networks, but the use of multiple active relays for cooperative communication increases hardware cost and system complexity.Prior Art 3 [H. Yang et al., “Intelligent Reflecting Surface Assisted Anti-Jamming Communications: AFast Reinforcement Learning Approach,” IEEE Transactions on Wireless Communications, vol. 20, no. 3, pp. 1963-1974, 2021] maximizes the system’s total transmission rate by jointly optimizing the power allocation of the desired transmitter and the reflected beam of the intelligent reflecting surface under the constraint of minimum signal-to-interference-noise ratio. This can improve the received signal quality of the desired receiver while eliminating the impact of environmental interference. However, this method requires the desired transmitter to be able to obtain the channel state information of the interference experience and the transmission beam of the interfering transmitter. Prior Art 4 [X. Tang, D. Wang, R. Zhang, Z. Chuand Z. Han, “Jamming Mitigation via Aerial Reconfigurable Intelligent Surface: Passive Beamforming and Deployment Optimization,” IEEE Transactions on Vehicular Technology, vol. 70, no. 6, pp. 6232-6237, 2021]: In a communication scenario consisting of a desired transmitter, a desired receiver, and an interfering transmitter each equipped with a single antenna, an intelligent reflecting surface (IRS) carried by a drone and flexibly movable in the air is deployed. By jointly optimizing the IRS’s aerial deployment position and the reflection coefficient of each IRS element, the interference experienced by the desired receiver is mitigated and the desired transmission is enhanced. However, this method assumes that the desired transmitter can obtain the channel state information between the interfering transmitter and each IRS element to design the reflection coefficient of each IRS element.

[0004] In summary, existing interference management technologies face the following challenges: First, their implementation requires consuming limited desired transmit power, compromising the communication quality of either the desired or interfering communication pair, and increasing hardware costs and computational complexity. Furthermore, these technologies rely on collaboration between the interfered communication pair and the interference source to obtain information about the interference-related channel state and the data carried by the interference. This not only increases signaling overhead but also, since the interfering transmitter needs to share its own data information with the desired transmitter, poses a threat to the data transmission privacy of the interfering communication pair. Second, existing IRS-based interference management technologies require knowledge of the channel coefficients between the interference source and each IRS reflection unit in order to design the reflection coefficients for each reflection unit. However, considering factors such as channel estimation overhead and the malicious nature of the interference source, it is difficult to accurately estimate the channel information from the interference source to a large number of reflection units in practice. Furthermore, the interference cancellation method, which estimates the channel coefficients between each IRS reflection unit and the interference source and designs the reflection coefficients for each reflection unit, increases the complexity of designing and adjusting the IRS reflection coefficients. Therefore, the hardware, processing, and other overheads of existing interference management methods will restrict their application. In scenarios where the desired communication pair cannot establish collaboration with the interference source, designing interference cancellation methods with low overhead (including hardware deployment, power consumption, and signaling interaction, etc.) has important practical significance. Summary of the Invention

[0005] In response to the technical problem in the prior art of suppressing the interference suffered by the desired communication receiver when it is difficult for the desired communication pair to establish cooperation with the interference transmitter, the present invention proposes an interference elimination method assisted by an intelligent reflecting surface. The method does not require the desired communication pair to highly cooperate with the interference transmitter to obtain information related to the interference. The intelligent reflecting surface can be used to effectively eliminate the interference, thereby reducing signaling overhead, reducing the complexity of the desired communication pair, and improving the communication quality of the desired communication pair.

[0006] In order to achieve the above object, the technical solution of the present invention is implemented as follows: an interference elimination method assisted by an intelligent reflective surface, the steps of which are as follows:

[0007] Step S101: The desired communication transmitter estimates the channel matrix between itself and the smart reflective surface and notifies the desired communication receiver. The desired communication receiver estimates the channel matrices between itself, the desired communication transmitter and the smart reflective surface and feeds back the estimated channel matrices to the desired communication transmitter.

[0008] Step S102: On the premise of measuring the relative characteristics of direct interference and reflected interference suffered by the desired communication receiver, the desired communication transmitter and the desired communication receiver regard the multipath reflected interference components from the smart reflective surface as one path of equivalent reflected interference at the desired communication receiver;

[0009] S103: The desired communication transmitter uniformly adjusts the reflection coefficients of multiple reflection units of the smart reflection surface so that the equivalent reflection interference received by the desired communication receiver can suppress the direct interference received from the interference transmitter, thereby improving the spectrum efficiency of the desired communication.

[0010] Preferably, the intelligent reflecting surface IRS comprises K reflecting units, and the intelligent reflecting surface is controlled by the desired communication transmitter Tx; the desired communication transmitter Tx and the desired communication receiver Rx are respectively configured with N T Transmitting antennas and N R Root receiving antenna, jammer configuration N J root transmitting antenna; there is no mutual cooperation between the desired communication transmitter Tx and the jammer Jammer, and the desired communication transmitter Tx cannot obtain the interference information; the desired signal transmitted by the desired communication transmitter Tx directly reaches the desired communication receiver Rx through the direct channel on the one hand, and is reflected to the desired communication receiver Rx through the intelligent reflecting surface IRS on the other hand; the desired communication receiver Rx may receive the direct interference transmitted by the jammer Jammer and the reflected interference emitted by the jammer Jammer and reflected to the desired communication receiver Rx through the intelligent reflecting surface IRS.

[0011] Preferably, the desired communication transmitter Tx uses beamforming to send a data path x to the desired communication receiver Rx. T , the jammer sends a precoding vector p J Preprocessing, carrying data x J The interference satisfies E(||x l || 2 )=1, l∈{T,J}, E(·) means finding the mathematical expectation;

[0012] Using the spatially uncorrelated Rayleigh flat fading channel model, the channel matrix between the desired communication transmitter Tx to the desired communication receiver Rx and the intelligent reflecting surface IRS is and Channel matrix between intelligent reflecting surface IRS and desired communication receiver Rx Channel matrix between the jammer, the desired communication receiver Rx, and the intelligent reflecting surface IRS and The elements of are independent of each other and obey the complex Gaussian distribution with zero mean and unit variance;

[0013] All channels have block fading characteristics, that is, the channel parameters remain unchanged within a block containing multiple time slots and vary randomly between adjacent blocks.

[0014] Preferably, the method for the desired communication transmitter Tx to obtain the channel matrix related to the desired communication is as follows: the desired communication transmitter Tx turns off the intelligent reflective surface IRS through the controller and broadcasts the pilot signal, and the desired communication receiver Rx estimates the direct channel matrix between it and the desired communication transmitter Tx based on the received pilot signal. And feed back to the desired communication transmitter Tx, represents the complex space, N T Indicates the number of transmitting antennas of the desired communication transmitter Tx, N R N represents the number of receiving antennas of the desired communication receiver Rx. T >N R = 1; the communication transmitter Tx is expected to turn on the intelligent reflecting surface IRS and broadcast the pilot signal, and the communication transmitter Tx is expected to estimate the channel matrix between it and the intelligent reflecting surface IRS The desired communication receiver Rx is notified, and the desired communication receiver Rx estimates the channel matrix between it and the intelligent reflecting surface IRS And feed back to the desired communication transmitter Tx.

[0015] Preferably, the information related to the interference that the desired communication transmitter Tx cannot obtain includes: the channel matrix between the jammer Jammer and the desired communication receiver Rx Channel matrix from Jammer to Intelligent Reflecting Surface (IRS) Jammer's preprocessing vector p J And the data information x carried by the interference J ; Among them, N J Indicates the number of antennas of the jammer.

[0016] Preferably, the desired communication transmitter Tx uses beamforming to send a beam of light through the precoding vector p to the desired communication receiver Rx. T Preprocessing, carrying data x T The desired signal, the jammer Jammer sends a precoding vector p to the desired communication receiver Rx. J Preprocessing, carrying data x J Interference signal; the signals transmitted by the desired communication transmitter Tx and the jammer Jammer will be reflected by the intelligent reflecting surface IRS to the desired communication receiver Rx, then the mixed signal received at the desired communication receiver Rx is in, represents the direct transmission desired signal from the desired communication transmitter Tx, The second term represents the reflected desired signal emitted from the desired communication transmitter Tx, incident on the smart reflecting surface IRS, and reflected by the IRS to the desired communication receiver Rx. The third item represents the direct interference from the jammer. The fourth term represents the reflected interference emitted from the jammer, incident on the intelligent reflecting surface IRS, and reflected by the IRS, P T and P J They represent the transmission power of the desired communication transmitter Tx and the interference transmitter Jammer respectively, represents the reflection coefficient matrix of the intelligent reflective surface IRS, represents the reflection coefficient of the i-th reflection unit, i∈{1,2,…,K}, β i ∈[0,1] and θ i ∈[0,2π] are the reflection amplitude coefficient and reflection phase coefficient of the i-th reflection unit, diag(·) represents the diagonalization of the vector, n is the additive Gaussian white noise with mean 0 and variance

[0017] Preferably, the implementation method of step 102 is: the communication receiver Rx is expected to measure the direct interference i JR And the reflection coefficient matrix of the intelligent reflective surface IRS is set to E K Reflection interference i JSR The relative characteristic η Δ , and the relative characteristic η Δ Feedback to the desired communication transmitter Tx; the desired communication regards the K-path reflection interference components transmitted by the jammer Jammer and reflected by the K reflection units of the intelligent reflecting surface IRS to the desired communication receiver Rx as one path of equivalent reflection interference The desired communication transmitter Tx is based on the relative characteristic η Δ Uniformly adjust the reflection phase coefficient θ of the K reflection units of the intelligent reflection surface IRS C and the reflection amplitude coefficient β C ;

[0018] The implementation method of step 103 is: the desired communication transmitter Tx sets the reflection coefficient matrix of the intelligent reflection surface IRS Among them, E K Represents the K×K unit matrix, so that the direct interference i JR Interference with equivalent reflection The anti-phase cancellation occurs at the desired communication receiver Rx.

[0019] Preferably, the desired communication receiver Rx measures the direct interference The reflection coefficient matrix of the intelligent reflective surface IRS is set to E K Reflection interference Relative characteristics where αΔ and Represent the relative amplitude characteristics and relative phase characteristics of the two interference components respectively. It is expected that the communication receiver Rx will measure the relative characteristics Feedback to the desired communication transmitter Tx;

[0020] The equivalent reflection interference in, represents the channel fading coefficient between the i-th reflection unit of the intelligent reflecting surface IRS and the desired communication receiver Rx, is the channel matrix H SR The i-th element in represents the equivalent channel fading coefficient between the jammer and the i-th reflection unit of the intelligent reflecting surface IRS, is the equivalent channel matrix H JS,E The i-th element of ;

[0021] The desired communication transmitter Tx is based on the relative characteristic η Δ The reflection coefficients of the K reflection units of the intelligent reflection surface IRS are set to And get the equivalent reflection interference

[0022] Reflection phase coefficient θ of the reflection unit of the intelligent reflecting surface IRS C Need to meet Among them, arg(·) represents the phase of the complex signal. represents the set of integers; according to the equation get The desired communication transmitter Tx calculates the reflection phase coefficient

[0023] Preferably, it is desired that the communication transmitter Tx is based on the measured relative amplitude characteristic α Δ Calculate the reflection amplitude coefficient β of the reflection unit of the intelligent reflecting surface IRS C , there are two cases: 1) When 0<α Δ ≤1, sets the amplitude coefficient β of the intelligent reflecting surface IRS reflection unit C =α Δ , which can make the equivalent reflected interference observed by the desired communication receiver Rx With direct interference i JR The same strength, with i JR Completely canceled at the desired communication receiver Rx; 2) when α Δ > 1, the amplitude coefficients of all reflection units of the intelligent reflecting surface IRS are set to β C=1, at this time, the direct interference intensity observed by the communication receiver Rx is still greater than the equivalent reflected interference, and residual interference will exist at the communication receiver Rx;

[0024] The desired communication transmitter Tx sets the reflection coefficient matrix of the intelligent reflecting surface IRS for Among them, when 0<α Δ ≤1, let The direct interference and the equivalent reflected interference components can be completely offset in anti-phase at the desired communication receiver Rx; when α Δ >1, Residual interference is desired to exist at the communication receiver Rx.

[0025] A wireless communication system using an intelligent reflective surface-assisted interference elimination method includes a desired communication transmitter Tx, a desired communication receiver Rx, a jammer Jammer, and an intelligent reflective surface IRS including K reflective units. The intelligent reflective surface IRS is controlled by the desired communication transmitter Tx.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention utilizes the low power consumption and simple and flexible signal processing characteristics of IRS, and uses IRS reflected interference to suppress the direct interference from the jammer at the desired communication receiver. It does not need to consume the limited desired transmission power, has the characteristics of low overhead, and is easy to deploy and apply in practice.

[0028] 2. The present invention does not require obtaining the spatial characteristics of the interference of the jammer on the desired communication receiver and the channel coefficient from the jammer to each IRS reflection unit. Instead, the reflection coefficients of all IRS units are uniformly adjusted based on the overall relative characteristics of the measured direct interference and equivalent reflected interference, so that the equivalent reflected interference and the direct interference cancel each other out of phase at the desired communication receiver, thereby reducing the channel estimation overhead related to interference and the complexity of IRS coefficient design.

[0029] 3. The present invention is not only applicable to wireless communication systems assisted by intelligent reflective surfaces in the presence of interference from neighboring legitimate communications, but also to communication countermeasure scenarios in the presence of malicious interference. That is, the present invention can effectively eliminate the impact of environmental interference, including malicious interference, on desired communications without relying on the cooperation of jammers and the sharing of interference information. Its application is more universal than existing methods and technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 It is a schematic diagram of the process of the present invention.

[0032] Figure 2 It is a schematic diagram of the system model of the present invention;

[0033] Figure 3 It is a simulation diagram of the spectrum efficiency SE of the expected communication receiver under the condition of interference-to-noise ratio ζ=10dB according to the present invention. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0035] On the premise of measuring the relative characteristics of the direct interference and reflected interference suffered by the desired communication receiver, the present invention first regards the multi-path reflected interference components from the intelligent reflecting surface as one path of equivalent reflected interference at the desired communication receiver, and then the desired communication transmitter uniformly adjusts the reflection coefficients of multiple reflecting units of the intelligent reflecting surface, so that the equivalent reflected interference suffered by the desired communication receiver can suppress the direct interference suffered directly from the interference transmitter, thereby improving the spectrum efficiency of the desired communication receiver.

[0036] Example 1

[0037] like Figure 1 As shown, an intelligent reflective surface-assisted interference elimination method provided by an embodiment of the present invention includes the following steps:

[0038] S101: The desired communication transmitter estimates the channel matrix between itself and the smart reflective surface and notifies the desired communication receiver. The desired communication receiver estimates the channel matrices between itself, the desired communication transmitter and the smart reflective surface and feeds back the estimated channel matrices to the desired communication transmitter.

[0039] S102: On the premise that relative characteristics of direct interference and reflected interference suffered by the desired communication receiver are measured, the desired communication pair, i.e., the desired communication transmitter and the desired communication receiver, regard the multipath reflected interference components from the smart reflective surface as one path of equivalent reflected interference at the desired communication receiver;

[0040] S103: The desired communication transmitter uniformly adjusts the reflection coefficients of multiple reflection units of the smart reflection surface so that the equivalent reflection interference received by the desired communication receiver can suppress the direct interference received from the interference transmitter, thereby improving the spectrum efficiency of the desired communication.

[0041] Figure 1 The flowchart for implementing the present invention illustrates a complete algorithm execution cycle. Specifically, the method of the present invention is executed once within a communication cycle, and communication is then performed based on this execution. During the communication cycle, the channel and interference states remain stable. Over time, the present invention is repeatedly executed at intervals of the communication cycle.

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0043] like Figure 2 As shown in FIG, the system model used in the present invention is a communication system assisted by an intelligent reflective surface. The system includes a desired communication transmitter Tx, a desired communication receiver Rx, a jammer, and an intelligent reflective surface IRS comprising K reflective units. The intelligent reflective surface IRS is controlled by the desired communication transmitter Tx. The transmission power of the desired communication transmitter Tx is P T , the desired communication transmitter Tx and the desired communication receiver Rx are configured with 2 transmitting antennas and 1 receiving antenna respectively, and the transmission power of the jammer Jammer is P J There are two transmitting antennas. There is no cooperation between the desired communication transmitter Tx and the jammer Jammer. Assume that the desired communication transmitter Tx uses beamforming (BF) to send a data path x to the desired communication receiver Rx. T , the jammer sends a signal through vector p J Preprocessing, carrying data x J The interference satisfies E(||x i || 2 )=1,i∈{T,J},E(·)denotes the mathematical expectation. The channel matrices between the desired communication transmitter Tx, the desired communication receiver Rx and the intelligent reflecting surface IRS are respectively expressed as and The channel matrix between the intelligent reflecting surface IRS and the desired communication receiver Rx is represented by The channel matrices between the jammer, the desired communication receiver Rx and the intelligent reflecting surface IRS are and Among them, N R 、N T 、N J Respectively represent the number of antennas of the desired communication receiver Rx, the desired communication transmitter Tx, and the jammer Jammer. The present invention adopts a spatially uncorrelated Rayleigh flat fading channel model, that is, the elements of the above-mentioned channel matrix are independent of each other and all obey a complex Gaussian distribution with zero mean and unit variance. It is assumed that all channels have block fading characteristics, that is, the channel parameters remain unchanged within a block containing multiple time slots and change randomly between adjacent blocks. The desired signal transmitted by the desired communication transmitter Tx, on the one hand, directly reaches the desired communication receiver Rx through the direct channel, and on the other hand, is reflected to the desired communication receiver Rx through the intelligent reflecting surface IRS. In addition, the desired communication receiver Rx may receive direct interference from the jammer Jammer and reflected interference emitted by the jammer Jammer and reflected to the desired communication receiver Rx through the intelligent reflecting surface IRS.

[0044] Example 2

[0045] An intelligent reflective surface-assisted interference elimination method provided in an embodiment of the present invention specifically includes the following steps:

[0046] Step 1: The communication system consists of a desired communication transmitter Tx, a desired communication receiver Rx, an intelligent reflecting surface IRS controlled by the desired communication transmitter Tx, and a jammer. The desired communication transmitter Tx can obtain the channel matrix related to the desired communication. There is no cooperation between the desired communication transmitter Tx and the jammer, and the desired communication transmitter Tx cannot obtain interference information. The implementation steps are as follows:

[0047] Step 1a: The desired communication transmitter Tx can obtain the channel matrix related to the desired communication: the desired communication transmitter Tx turns off the intelligent reflective surface IRS through the controller and broadcasts the pilot signal. The desired communication receiver Rx estimates the direct channel matrix between it and the desired communication transmitter Tx based on the received pilot signal. And feed back to the desired communication transmitter Tx, represents the complex space, N T Indicates the number of transmitting antennas of the desired communication transmitter Tx, N R N represents the number of receiving antennas of the desired communication receiver Rx, T >N R= 1. The desired communication transmitter Tx turns on the intelligent reflecting surface IRS and broadcasts a pilot signal. The desired communication transmitter Tx estimates the channel matrix between it and the intelligent reflecting surface IRS. The desired communication receiver Rx is notified, and the desired communication receiver Rx estimates the channel matrix between it and the intelligent reflecting surface IRS The desired communication transmitter Tx is fed back to the desired communication transmitter. The desired communication transmitter Tx can know the channel matrix related to the desired communication, that is, the channel matrix between Tx and IRS and IRS and Rx. This facilitates the desired communication transmitter Tx to design the desired transmit precoding vector so that the desired signal received by the desired communication receiver Rx is zero, thereby obtaining the relative characteristics of direct interference and reflected interference, and finally achieving the interference cancellation of this patent.

[0048] Step 1b: There is no cooperation between the desired communication transmitter Tx and the jammer Jammer, and the desired communication transmitter Tx cannot obtain information related to the interference, including: the channel matrix between the jammer Jammer and the desired communication receiver Rx Channel matrix from Jammer to Intelligent Reflecting Surface (IRS) Jammer's preprocessing vector p J And the data information x carried by the interference J ; Among them, N J Indicates the number of antennas of the jammer. This can be used to address malicious interference sources, that is, when the desired communication pair and the malicious jammer cannot cooperate, and eliminate interference at the desired communication receiver Rx.

[0049] Step 1c: The desired communication transmitter Tx transmits a beam of light through the precoding vector p to the desired communication receiver Rx using beamforming. T Preprocessing, carrying data x T The desired signal, the jammer Jammer sends a precoding vector p to the desired communication receiver Rx. J Preprocessing, carrying data x J Since beamforming is used, the precoding vector p can be designed by singular value decomposition (SDV decomposition). T So that the expected data transmitted by the expected communication transmitter Tx reaches the expected communication receiver Rx after preprocessing. J Similarly, the signals transmitted by the desired communication transmitter Tx and the jammer Jammer will both be reflected by the intelligent reflecting surface IRS to the desired communication receiver Rx. Then the mixed signal received by the desired communication receiver Rx is The first term on the right side of the equation represents the direct desired signal from the desired communication transmitter Tx, the second term represents the reflected desired signal emitted from the desired communication transmitter Tx, incident on the smart reflective surface IRS, and reflected by the IRS to the desired communication receiver Rx, the third term represents the direct interference from the jammer Jammer, and the fourth term represents the reflected interference emitted from the jammer Jammer, incident on the smart reflective surface IRS, and reflected by the smart reflective surface IRS. T and P J They represent the transmission power of the desired communication transmitter Tx and the interference transmitter Jammer respectively, represents the reflection coefficient matrix of the intelligent reflective surface IRS, represents the reflection coefficient of the i-th reflection unit, i∈{1,2,…,K}, β i ∈[0,1] and θ i ∈[0,2π] are the reflection amplitude coefficient and reflection phase coefficient of the i-th reflection unit respectively, diag(·) represents the diagonal processing of the vector, and each element on the diagonal represents the independent processing of the incident signal by each reflection unit on the intelligent reflection surface IRS. n is an additive Gaussian white noise with a mean of 0 and a variance of In the presence of interference, the mixed signal received at the desired communication receiver Rx includes the direct desired signal and direct interference from the desired communication transmitter Tx and the jammer Jammer, as well as the reflected desired signal and reflected interference reflected by the intelligent reflecting surface IRS.

[0050] Step 2: The desired communication receiver Rx measures the direct interference i it suffers JR And the reflection coefficient matrix of the intelligent reflective surface IRS is set to E K Reflection interference i JSR The relative characteristic η Δ , and the relative characteristic η Δ The desired communication regards the K-path reflected interference components transmitted by the jammer Jammer and reflected by the K reflection units of the intelligent reflecting surface IRS to the desired communication receiver Rx as one path of equivalent reflected interference. The desired communication transmitter Tx is based on the relative characteristic η Δ Uniformly adjust the reflection phase coefficient θ of the K reflection units of the intelligent reflection surface IRS C and the reflection amplitude coefficient β C , the implementation steps are as follows:

[0051] Step 2a, the desired communication receiver Rx measures the direct interference And the reflection coefficient matrix of the intelligent reflective surface IRS is set to E K Reflection interference Relative characteristics of where α Δ and Represent the relative amplitude characteristics and relative phase characteristics of the two interference components respectively. It is expected that the communication receiver Rx will measure the relative characteristics Feedback to the desired communication transmitter Tx.

[0052] Step 2b, define the equivalent channel matrix H between the jammer and the intelligent reflecting surface IRS JS,E =H JS p J The K-path reflection interference components transmitted by the Jammer and reflected by the K reflection units of the intelligent reflector surface IRS to the desired communication receiver Rx are regarded as one path of equivalent reflection interference. in, represents the channel fading coefficient between the i-th reflection unit of the intelligent reflecting surface IRS and the desired communication receiver Rx, is the channel matrix H SR The i-th element in represents the equivalent channel fading coefficient between the jammer and the i-th reflection unit of the intelligent reflecting surface IRS, is the equivalent channel matrix H JS,E The i-th element of H SR It is the channel matrix between the intelligent reflector IRS and the desired receiver Rx, which is actually a vector with 1 row and K columns. The channel coefficients from the i-th reflection unit to the desired communication receiver Rx constitute the channel matrix H between the intelligent reflection surface IRS and the desired communication receiver Rx. SR The expected communication transmitter Tx is based on the relative characteristic η Δ The reflection coefficients of the K reflection units of the intelligent reflection surface IRS are set to And can get

[0053] Step 2c, to make the equivalent reflection interference Direct interference The reflection phase coefficient θ of the intelligent reflecting surface IRS reflection unit is inversely superimposed at the desired communication receiver Rx. C Needs to be satisfied Where arg(·) represents the phase of the complex signal. represents the set of integers. According to the equation Can get It is expected that the communication transmitter Tx can calculate the reflection phase coefficient

[0054] Step 2d, the desired communication transmitter Tx is based on the measured relative amplitude characteristic α Δ Calculate the reflection amplitude coefficient β of the reflection unit of the intelligent reflecting surface IRS C , there are two cases: 1) When 0<α Δ ≤1, sets the amplitude coefficient β of the intelligent reflecting surface IRS reflection unit C =α Δ , which can make the equivalent reflected interference observed by the desired communication receiver Rx With direct interference i JR The same strength, with i JR Completely canceled at the desired communication receiver Rx; 2) when α Δ > 1, the amplitude coefficients of all reflection units of the intelligent reflecting surface IRS are set to β C =1, at this time, the direct interference intensity observed by the communication receiver Rx is still greater than the equivalent reflected interference, so there will be residual interference at the communication receiver Rx.

[0055] Step 3: The desired communication transmitter Tx sets the reflection coefficient matrix of the intelligent reflecting surface IRS E K Represents the K×K unit matrix, so that the direct interference i JR Interference with equivalent reflection The reverse phase cancellation is performed at the desired communication receiver Rx to improve the spectrum efficiency of the desired communication. The specific implementation steps are as follows:

[0056] The desired communication transmitter Tx sets the reflection coefficient matrix of the intelligent reflecting surface IRS for Among them, when 0<α Δ ≤1, let The direct interference and the equivalent reflected interference components can be completely offset in anti-phase at the desired communication receiver Rx; when α Δ >1, Residual interference is desired to exist at the communication receiver Rx.

[0057] The application effect of the present invention is described in detail below in conjunction with simulation experiments.

[0058] 1. Simulation conditions:

[0059] Simulation Objectives: The proposed IRS-aided interference cancellation (IRS-IC) method is compared with the IRS-aided transmission enhancement without reflecting interference (IRS-TE w / o RI), the IRS-aided transmission enhancement with reflecting interference (IRS-TE w / RI), and the transmission without IRS (T w / o IRS). MATLAB simulations are used to obtain the desired receiver spectral efficiency (SE).

[0060] Simulation parameters: Set the desired communication transmitter Tx transmission power to P T , the transmission power of the jammer is P J , define the transmission power ratio of the desired communication transmitter Tx and the jammer Jammer η=P T / P J , and set η∈[1,10], the interference-to-noise ratio Represents the power of additive white Gaussian noise. The desired communication transmitter Tx and the jammer Jammer are each equipped with two transmitting antennas, the desired communication receiver Rx is configured with one receiving antenna, and there are K = 10 reflection units on the intelligent reflecting surface IRS. A spatially uncorrelated Rayleigh flat fading channel model is adopted, that is, the elements of the channel matrix are independent of each other and obey a complex Gaussian distribution with zero mean and unit variance. It is assumed that all channels have block fading characteristics, that is, the channel parameters remain unchanged within a block containing multiple time slots and vary randomly between adjacent blocks. The desired communication transmitter Tx sends a desired signal to the desired communication receiver Rx, and the desired signal will be reflected to the desired communication receiver Rx by the intelligent reflecting surface IRS. The jammer Jammer sends an interference to the desired communication receiver Rx, and the interference will be reflected to the desired communication receiver Rx by the intelligent reflecting surface IRS.

[0061] 2. Simulation content and analysis: The following is combined Figure 3 The simulation diagram of the present invention is further described.

[0062] When N T =N J=2, N R = 1, the spectrum efficiency SE of the desired communication receiver Rx is simulated under the condition of interference-to-noise ratio ζ = 10dB. The simulation results are as follows: Figure 3 As shown, the vertical axis represents the spectrum efficiency SE, and the horizontal axis represents the transmission power ratio η of the desired communication transmitter Tx and the jammer Jammer.

[0063] like Figure 3 As shown in Figure 2, when ζ = 10 dB, the SE performance of IRS-TE w / o RI is the best, followed by IRS-IC, then IRS-TE w / RI, and T w / o IRS is the worst. It should be noted that due to the open nature of intelligent reflective surfaces (IRS), the assumption that reflection interference does not exist is not necessarily true. Therefore, the method of using intelligent reflective surfaces (IRS) to enhance the desired transmission is usually not able to obtain the desired transmission performance. Figure 3 The spectral efficiency (SE) of the IRS-TE with RI (in Figure 2) is significantly lower than that of the IRS-TE with RI. When ζ = 10 dB, the direct and reflected interference from the jammer are strong. When K = 10, the IRS-IC can, with high probability, completely cancel the direct interference at the desired receiver Rx with the reflected interference. Therefore, the IRS-IC effectively eliminates the impact of interference on Rx, significantly improving the SE of the desired communication receiver Rx. For IRS-TE with RI, the desired receiver Rx experiences both strong direct and reflected interference. Since the reflection coefficient matrix of the intelligent reflecting surface (IRS) is designed with the goal of enhancing the desired transmission, the intelligent reflecting surface (IRS) cannot suppress the interference experienced by the desired communication receiver Rx. Therefore, its spectral efficiency (SE) is inferior to that of IRS-IC. In the T with IRS simulation, the desired communication receiver Rx receives only the direct desired signal and direct interference, without any auxiliary desired transmission enhancement or interference cancellation / suppression from the IRS. Consequently, its SE performance is the worst.

[0064] from Figure 3 It can be found that when the interference is strong, the proposed IRS-IC can effectively improve the spectrum efficiency SE of the desired communication receiver Rx compared with other methods.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An interference elimination method assisted by a smart reflective surface, characterized in that: The steps are as follows: Step S101: The desired communication transmitter estimates the channel matrix between itself and the smart reflective surface and notifies the desired communication receiver. The desired communication receiver estimates the channel matrices between itself, the desired communication transmitter, and the smart reflective surface, respectively, and feeds back the channel matrices to the desired communication transmitter. The smart reflective surface includes K reflective units and is controlled by the desired communication transmitter. Step S102: On the premise of measuring the relative characteristics of direct interference and reflected interference suffered by the desired communication receiver, the desired communication transmitter and the desired communication receiver regard the multipath reflected interference components from the smart reflective surface as one path of equivalent reflected interference at the desired communication receiver; The implementation method of step S102 is as follows: the communication receiver Rx is expected to measure the direct interference i JR and the reflection coefficient matrix of the smart reflective surface is set to E K Reflection interference i JSR The relative characteristic η Δ , and the relative characteristic η Δ Feedback to the desired communication transmitter Tx; The desired communication pair considers the K-path reflected interference components transmitted by the jammer and reflected by the K reflection units of the smart reflection surface to the desired communication receiver Rx as one path of equivalent reflected interference. The desired communication transmitter Tx is based on the relative characteristic η Δ Uniformly adjust the reflection phase coefficient θ of the K reflection units of the intelligent reflection surface IRS C and the reflection amplitude coefficient β C ; Step S103: The desired communication transmitter uniformly adjusts the reflection coefficients of the multiple reflection units of the smart reflection surface so that the equivalent reflection interference received by the desired communication receiver can suppress the direct interference received by the interference transmitter, thereby improving the spectrum efficiency of the desired communication; The implementation method of step S103 is: the desired communication transmitter Tx sets the reflection coefficient matrix of the intelligent reflection surface IRS Among them, E K Represents the K×K unit matrix, so that the direct interference i JR Interference with equivalent reflection The anti-phase cancellation occurs at the desired communication receiver Rx.

2. The intelligent reflective surface-assisted interference elimination method according to claim 1, characterized in that: The desired communication transmitter Tx and the desired communication receiver Rx are configured with N T Transmitting antennas and N R Root receiving antenna, jammer configuration N J root transmitting antenna; there is no mutual cooperation between the desired communication transmitter Tx and the jammer Jammer, and the desired communication transmitter Tx cannot obtain the interference information; the desired signal transmitted by the desired communication transmitter Tx directly reaches the desired communication receiver Rx through the direct channel on the one hand, and is reflected to the desired communication receiver Rx through the intelligent reflecting surface IRS on the other hand; the desired communication receiver Rx may receive the direct interference transmitted by the jammer Jammer and the reflected interference emitted by the jammer Jammer and reflected to the desired communication receiver Rx through the intelligent reflecting surface IRS.

3. The intelligent reflective surface-assisted interference elimination method according to claim 2, characterized in that: The desired communication transmitter Tx uses beamforming to send a data path x to the desired communication receiver Rx T , the jammer sends a precoding vector p J Preprocessing, carrying data x J The interference satisfies E(||x l || 2 )=1, l∈{T,J}, E(·) means finding the mathematical expectation; Using the spatially uncorrelated Rayleigh flat fading channel model, the channel matrix between the desired communication transmitter Tx to the desired communication receiver Rx and the intelligent reflecting surface IRS is and Channel matrix between intelligent reflecting surface IRS and desired communication receiver Rx Channel matrix between the jammer, the desired communication receiver Rx, and the intelligent reflecting surface IRS and The elements of are independent of each other and obey the complex Gaussian distribution with zero mean and unit variance; represents complex space; All channels have block fading characteristics, that is, the channel parameters remain unchanged within a block containing multiple time slots and vary randomly between adjacent blocks.

4. The intelligent reflective surface-assisted interference elimination method according to claim 3, characterized in that: The method for the desired communication transmitter Tx to obtain the channel matrix related to the desired communication is as follows: the desired communication transmitter Tx turns off the intelligent reflective surface IRS through the controller and broadcasts the pilot signal, and the desired communication receiver Rx estimates the direct channel matrix between it and the desired communication transmitter Tx based on the received pilot signal And feed back to the desired communication transmitter Tx, represents the complex space, N T Indicates the number of transmitting antennas of the desired communication transmitter Tx, N R N represents the number of receiving antennas of the desired communication receiver Rx. T >N R = 1; the communication transmitter Tx is expected to turn on the intelligent reflecting surface IRS and broadcast the pilot signal, and the communication transmitter Tx is expected to estimate the channel matrix between it and the intelligent reflecting surface IRS The desired communication receiver Rx is notified, and the desired communication receiver Rx estimates the channel matrix between it and the intelligent reflecting surface IRS And feed back to the desired communication transmitter Tx.

5. The intelligent reflective surface-assisted interference elimination method according to claim 3 or 4, characterized in that: The desired communication transmitter Tx cannot obtain the information related to the interference, including: the channel matrix between the jammer Jammer and the desired communication receiver Rx Channel matrix from Jammer to Intelligent Reflecting Surface (IRS) Jammer's preprocessing vector p J And the interference carried by the data x J ; Among them, N J Indicates the number of antennas of the jammer.

6. The intelligent reflective surface-assisted interference elimination method according to claim 5, characterized in that: The desired communication transmitter Tx uses beamforming to send a beam of light through the precoding vector p to the desired communication receiver Rx. T Preprocessing, carrying data x T The desired signal, the jammer Jammer sends a precoding vector p to the desired communication receiver Rx. J Preprocessing, carrying data x J Interference signal; the signals transmitted by the desired communication transmitter Tx and the jammer Jammer will be reflected by the intelligent reflecting surface IRS to the desired communication receiver Rx, then the mixed signal received at the desired communication receiver Rx is in, represents the direct transmission desired signal from the desired communication transmitter Tx, The second term represents the reflected desired signal emitted from the desired communication transmitter Tx, incident on the smart reflecting surface IRS, and reflected by the IRS to the desired communication receiver Rx. The third item represents the direct interference from the jammer. The fourth term represents the reflected interference emitted from the jammer, incident on the intelligent reflecting surface IRS, and reflected by the IRS, P T and P J They represent the transmission power of the desired communication transmitter Tx and the interference transmitter Jammer respectively, represents the reflection coefficient matrix of the intelligent reflective surface IRS, represents the reflection coefficient of the i-th reflection unit, i∈{1,2,…,K}, β i ∈[0,1] and θ i ∈[0,2π] are the reflection amplitude coefficient and reflection phase coefficient of the i-th reflection unit, diag(·) represents the diagonalization of the vector, n is the additive Gaussian white noise with mean 0 and variance 7. The intelligent reflective surface-assisted interference elimination method according to claim 1, characterized in that: The desired communication receiver Rx measures the direct interference The reflection coefficient matrix of the intelligent reflective surface IRS is set to E K Reflection interference Relative characteristics The relative characteristics that the communication receiver Rx is expected to measure Feedback to the desired communication transmitter Tx; where α Δ and Represent the relative amplitude characteristics and relative phase characteristics of the two interference components, P J Indicates the transmission power of the jammer, H JR is the channel matrix between the jammer Jammer and the desired communication receiver Rx, H JS H represents the channel matrix from the jammer to the intelligent reflecting surface IRS. SR represents the channel matrix between the intelligent reflecting surface IRS and the desired communication receiver Rx, x J is the data carried by the interference, p J is the preprocessing vector of the jammer; The equivalent reflection interference in, represents the channel fading coefficient between the i-th reflection unit of the intelligent reflecting surface IRS and the desired communication receiver Rx, is the channel matrix H SR The i-th element in represents the equivalent channel fading coefficient between the jammer and the i-th reflection unit of the intelligent reflecting surface IRS, is the equivalent channel matrix H JS,E The i-th element of β i and θ i are the reflection amplitude coefficient and reflection phase coefficient of the i-th reflection unit respectively; The desired communication transmitter Tx is based on the relative characteristic η Δ The reflection coefficients of the K reflection units of the intelligent reflection surface IRS are set to And get the equivalent reflection interference Reflection phase coefficient θ of the reflection unit of the intelligent reflecting surface IRS C Need to meet Among them, arg(·) represents the phase of the complex signal. represents the set of integers; according to the equation get The desired communication transmitter Tx calculates the reflection phase coefficient 8. The intelligent reflective surface-assisted interference elimination method according to claim 7, characterized in that: The desired communication transmitter Tx is based on the measured relative amplitude characteristic α Δ Calculate the reflection amplitude coefficient β of the reflection unit of the intelligent reflecting surface IRS C , there are two cases: 1) When 0<α Δ ≤1, sets the amplitude coefficient β of the intelligent reflecting surface IRS reflection unit C =α Δ , which can make the equivalent reflected interference observed by the desired communication receiver Rx With direct interference i JR The same strength, with i JR Completely canceled at the desired communication receiver Rx; 2) when α Δ > 1, the amplitude coefficients of all reflection units of the intelligent reflecting surface IRS are set to β C =1, at this time, the direct interference intensity observed by the communication receiver Rx is still greater than the equivalent reflected interference, and residual interference will exist at the communication receiver Rx; The desired communication transmitter Tx sets the reflection coefficient matrix of the intelligent reflecting surface IRS for Among them, when 0<α Δ ≤1, let The direct interference and the equivalent reflected interference components can be completely offset in anti-phase at the desired communication receiver Rx; when α Δ >1, Residual interference is desired to exist at the communication receiver Rx.

9. A wireless communication system using the intelligent reflective surface-assisted interference cancellation method according to any one of claims 1 to 8, comprising a desired communication transmitter Tx, a desired communication receiver Rx, a jammer Jammer, and an intelligent reflective surface IRS comprising K reflective units, wherein the intelligent reflective surface IRS is controlled by the desired communication transmitter Tx.

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