CN113194072A - Intelligent reflecting surface assisted legal monitoring implementation method - Google Patents

Intelligent reflecting surface assisted legal monitoring implementation method Download PDF

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CN113194072A
CN113194072A CN202110362522.6A CN202110362522A CN113194072A CN 113194072 A CN113194072 A CN 113194072A CN 202110362522 A CN202110362522 A CN 202110362522A CN 113194072 A CN113194072 A CN 113194072A
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antenna
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CN113194072B (en
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杜清河
王萌
张睿博
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Xian Jiaotong University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L63/00—Network architectures or network communication protocols for network security
    • H04L63/30—Network architectures or network communication protocols for network security for supporting lawful interception, monitoring or retaining of communications or communication related information
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
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Abstract

The invention discloses an intelligent reflector assisted lawful interception implementation method, which comprises the following steps: in the reverse pilot frequency transmission stage, a legal monitoring end carries out pilot frequency decoy, and reflects a pilot frequency sequence from a single-antenna suspicious receiving end by controlling a phase shift matrix of an intelligent reflecting surface so that channel estimation of a multi-antenna suspicious transmitting end is wrong; in the data transmission stage, the legal monitoring end maximizes the signal-to-noise ratio of the legal monitoring end by controlling the phase shift matrix of the intelligent reflecting surface, and the realization of the intelligent reflecting surface-assisted legal monitoring is completed.

Description

Intelligent reflecting surface assisted legal monitoring implementation method
Technical Field
The invention belongs to the field of wireless information security, and relates to an intelligent reflector assisted lawful interception implementation method.
Background
An Intelligent Reflector (IRS) is a brand new revolutionary technology in recent years, a large number of low-cost passive reflecting elements are integrated on the surface of the IRS, the wireless propagation environment can be configured intelligently, and the performance of a wireless communication network is improved effectively. Each element on the IRS surface can cooperate to achieve directional signal enhancement or null three-dimensional (3D) passive beamforming by independently controlling the amplitude, phase of the incident signal. The intelligent reflecting surface intelligently modifies the wireless channel through controlling signal reflection, and the adaptation of the wireless link of the transmitter and the receiver is in sharp contrast with the adaptation of the wireless link of the existing transmitter and the existing receiver, thereby providing a new degree of freedom for improving the performance of the wireless link and laying a foundation for realizing an intelligent programmable wireless environment. Through intelligent adjustment of passive beam forming, the intelligent reflection surface reflection signal can be constructively added with signals from other paths, the power of a desired signal at a receiving end is enhanced, and undesired signals such as co-channel interference and the like can be destructively eliminated or inhibited. From an implementation point of view, smart emitting surfaces also have great advantages. The surface is made of low profile, light weight, low cost, and conformal geometry, and is easily installed/removed on walls, building facades, ceilings, advertising panels, and the like. The intelligent reflective surface is a complementary device in a wireless network, and deployment in existing wireless systems (e.g., cellular or WiFi) would require no changes to standards and hardware, with only the necessary modifications to the communication protocol. The integration of the intelligent reflective surface into the wireless network is transparent to the user and provides a high degree of flexibility and superior compatibility compared to existing wireless systems. The intelligent reflective surface can be deployed and integrated at low cost. The smart reflective surface does not require the use of a transmit (RF) chain and operates over only a short distance. Therefore, the intelligent reflector can be densely deployed, has the characteristics of expandable cost and low energy consumption, and avoids complex interference management among intelligent reflecting surfaces.
In order to effectively monitor suspicious communication, many lawful interception schemes are applied to wireless suspicious information interception systems. The method can be divided into two categories, namely passive monitoring and active monitoring according to whether a lawful monitoring party participates in communication. Passive interception is the most direct and simple way to implement interception of suspicious information, and it only needs to intercept and decode the suspicious information. However, in a real listening scenario, in order not to be discovered by both of the suspicious communication parties, his location is usually far from the suspicious communication link. In which case the channel state information is worse than for the suspect communication link. However, successful interception can only be achieved if the intercepted link is of better quality than the suspect communication link. A monitor in an active monitoring scheme based on cognitive interference works in a full duplex mode, monitors a suspicious communication link and simultaneously sends artificial noise interference to a suspicious sending end, so that the signal sending speed of the sending end is slowed down, and the monitoring performance is improved. The active listening scheme, although capable of improving listening performance, is still limited to listening for link channel status. When the channel quality of the listening link is worse than the suspect communication link or the listening party is further away from the suspect communication link, it is likely that the listening party cannot receive the signal from the suspect transmitting end. Even if the monitoring party sends interference to the suspicious sender, the monitoring can not be realized. How to improve the monitoring signal strength in the lawful monitoring system is the key to realize successful monitoring and is a difficult problem to be solved in the lawful monitoring field.
The existing work has not considered the application of combining an intelligent reflective surface with a lawful interception technology in the field of information security. The intelligent reflecting surface deployed in large scale in the future can realize the monitoring function after being authorized. Is a potential partner of legal monitoring technology. Therefore, there is a need for research on how to apply the intelligent reflective surface to the field of information security.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides an intelligent reflecting surface assisted lawful interception implementation method, which can combine an intelligent reflecting surface with a lawful interception technology and improve the interception performance of a lawful interception end.
In order to achieve the above purpose, the method for implementing the intelligent reflector assisted lawful interception comprises the following steps:
in the reverse pilot frequency transmission stage, a legal monitoring end carries out pilot frequency decoy, and reflects a pilot frequency sequence from a single-antenna suspicious receiving end by controlling a phase shift matrix of an intelligent reflecting surface so that channel estimation of a multi-antenna suspicious transmitting end is wrong;
in the data transmission stage, the legal monitoring end controls the phase shift matrix of the intelligent reflecting surface to maximize the signal-to-noise ratio of the legal monitoring end and complete the realization of the intelligent reflecting surface-assisted legal monitoring.
The pilot frequency sequence from the single antenna suspicious receiving end is reflected by controlling the phase shift matrix of the intelligent reflecting surface, so that the specific process of the multi-antenna suspicious transmitting end channel estimation error is as follows:
constructing an optimization problem P3:
P3:
Figure BDA0003006136460000031
s.t.
Figure BDA0003006136460000032
wherein h isbAnd HAIRespectively representing fading channels, h, from a single-antenna suspect receiver and an IRS to a multi-antenna suspect transmitterIbRepresenting the channel from the single antenna suspect receiver to the IRS.
Solving an optimization problem P3 to obtain a phase shift matrix phi of the intelligent reflecting surface in the reverse pilot transmission stage0；
Phase shift matrix phi using smart reflective surfaces0And therefore, the multi-antenna suspicious transmitting end channel estimation is wrong.
The optimization problem P3 is equivalent to:
P4:
Figure BDA0003006136460000041
s.t.
Figure BDA0003006136460000042
wherein phi @ [ phi ]1,φ2,..,φN]H，
Figure BDA0003006136460000043
hbAnd HAIRespectively representing fading channels, h, from a single-antenna suspect receiver and an IRS to a multi-antenna suspect transmitterIbRepresenting the channel from the single antenna suspect receiver to the IRS.
Solving an optimization problem P4 by utilizing a minimum maximization algorithm to obtain a phase shift matrix phi of the intelligent reflecting surface in the reverse pilot transmission stage0。
The legal monitoring end controls the phase shift matrix of the intelligent reflection surface, so that the specific process of maximizing the signal-to-noise ratio of the legal monitoring end is as follows:
constructing an optimization problem P6:
P6:
Figure BDA0003006136460000044
s.t.
Figure BDA0003006136460000045
wherein h isIkIs a channel between the intelligent reflecting surface and the legal monitoring end, hekFor the channel between the multi-antenna suspicious transmitting terminal ST and the plurality of legal monitoring terminals LM, HAIA channel between a multi-antenna suspicious transmitting end ST and an intelligent reflecting surface;
solving an optimization problem P6 to obtain a phase shift matrix phi of the intelligent reflective surface in the data transmission phase1Wherein a phase shift matrix phi of the intelligent reflective surface in the data transmission phase is used1The signal-to-noise ratio of the legal monitoring end is maximized.
Solving an optimization problem P6 by using a minimum maximization algorithm to obtain a phase shift matrix phi of the intelligent reflecting surface in the data transmission stage1。
The invention has the following beneficial effects:
in the method for realizing the intelligent reflecting surface assisted legal monitoring, when in specific operation, a legal monitoring end carries out pilot frequency trapping in a reverse pilot frequency transmission stage, and reflects a pilot frequency sequence from a single-antenna suspicious receiving end by controlling a phase shift matrix of an intelligent reflecting surface, so that the channel estimation of a multi-antenna suspicious transmitting end is wrong, namely, the active monitoring is realized by the pilot frequency trapping, the energy consumption and the cost are lower, and in a data transmission stage, the legal monitoring end maximizes the signal-to-noise ratio of the legal monitoring end by controlling the phase shift matrix of the intelligent reflecting surface, so that the monitoring performance is improved. Compared with the traditional active and passive monitoring, the wireless transmission system can intelligently configure a wireless transmission environment, break through the performance bottleneck of the passive monitoring, improve the monitoring performance on the premise of hidden monitoring and realize remote monitoring.
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FIG. 1 is a schematic diagram of the system of the present invention;
FIG. 2 is a practical simulation model of the system of the present invention;
FIG. 3 is a diagram showing the variation of the SNR of the suspicious receiving end and the legal monitoring end with the number N of the intelligent reflection units;
FIG. 4 is a diagram showing the influence of the threshold of the receiving SNR of the suspicious receiving end and the number N of the reflection units on the average and SNR of the legal monitoring end in the present invention;
fig. 5 is a graph showing the variation of the signal-to-noise ratio of the lawful interception end with the distance between the suspected receiving end and the lawful interception end.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
There is shown in the drawings a schematic block diagram of a disclosed embodiment in accordance with the invention. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation. The shapes of various regions, layers and their relative sizes and positional relationships shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and a person skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, according to actual needs.
The invention relates to an intelligent reflector assisted lawful interception implementation method, which comprises the following steps:
referring to fig. 1, the system includes a multiple-antenna suspicious transmitting terminal ST, a single-antenna suspicious receiving terminal SR, and a plurality of remote single-antenna mobilesThe networking device is used as a legal monitoring end LM and an intelligent reflection surface IRS with N independent reflection units, and a channel between a multi-antenna suspicious sending end ST and the intelligent reflection surface is set to be HAIThe channel from the multi-antenna suspicious transmitting terminal ST to the single-antenna suspicious receiving terminal SR is hbThe channel between the multi-antenna suspicious sending terminal ST and the plurality of legal monitoring terminals LM is hekThe channel between the intelligent reflecting surface and the single-antenna suspicious receiving end SR is hIbChannel h between intelligent reflection surface and legal monitoring end LMIk。
In the system, the channels are assumed to be quasi-static fading channels, the channel state does not change in the time block of one-time reverse pilot sequence transmission and data transmission, and the change of the channel parameters of different transmission time blocks is independent and distributed. The system works in a TDD mode, channel reciprocity exists, and in the system, a channel of a legal monitoring end is set to be unknown to both suspicious communication parties. This assumption is true because it is difficult for both suspicious communication parties to detect the existence of the lawful interception end LM, especially under the active interception scheme assisted by the intelligent reflection surface, the single antenna suspicious receiving end SR sends a pilot sequence to the multiple antenna suspicious transmitting end ST for channel estimation, the lawful interception end LM performs pilot spoofing at the reverse pilot transmission stage, controls the intelligent reflection surface phase shift matrix to reflect the pilot sequence from the single antenna suspicious receiving end SR, so that the channel estimation of the multiple antenna suspicious transmitting end ST is wrong, causing information leakage. And the legal monitoring end LM controls the intelligent reflecting surface phase shift matrix in the data transmission stage, so that the average and signal-to-noise ratio of the monitoring end are maximized, and the monitoring capability is improved.
Specifically, a multi-antenna suspicious sending end and a single-antenna suspicious receiving end communicate with each other, the single-antenna suspicious receiving end sends a pilot frequency sequence to the multi-antenna suspicious sending end for channel estimation, a legal monitoring end performs pilot frequency decoy in a reverse pilot frequency transmission stage, and the pilot frequency sequence from the single-antenna suspicious receiving end is reflected by controlling an intelligent reflection surface IRS phase shift matrix, so that the multi-antenna suspicious sending end channel estimation is wrong, and information leakage is caused; in the data transmission stage, the legal monitoring end controls the intelligent reflecting surface phase shift matrix, so that the signal-to-noise ratio of the monitoring end is maximized, and the monitoring capability is improved.
The specific implementation scheme is as follows:
pilot trap stage
In the system, a legal monitoring end keeps silent in a reverse pilot frequency transmission stage, and reflects a pilot frequency sequence u transmitted from a single-antenna suspicious receiving end to a multi-antenna suspicious transmitting end by controlling an IRS (interference rejection service) consisting of N reflecting unitsHThe suspicious receiving end pilot frequency transmitting power of the single antenna is PbIf yes, the signal Y received by the single antenna suspicious receiving end is:
Figure BDA0003006136460000081
wherein h isbAnd HAIRespectively represent fading channels from a single antenna suspicious receiving end and an IRS to a multi-antenna suspicious transmitting end, hIbRepresents the channel from the single antenna suspicious receiver to the IRS, phi0＝diag{φ1,φ2,...,φN}∈￡N×NConsists of IRS reflection coefficient, phi is more than or equal to 0iI is not less than 1 for 1 and not more than N, wherein NaRepresenting additive complex Gaussian white noise received by a multi-antenna suspicious sending end, the mean value is 0, and the variance is
Figure BDA0003006136460000082
Channel estimation phase
The multi-antenna suspicious sending end obtains channel CSI by adopting least square estimation, the multi-antenna suspicious sending end knows pilot frequency sending power and pilot frequency sequences, pilot frequency spoofing causes channel estimation deviation at the multi-antenna suspicious sending end, information is leaked to an IRS surface, wherein the channel h estimated at the multi-antenna suspicious sending end is as follows:
Figure BDA0003006136460000083
data transmission phase
In the pilot frequency trapping scheme, the traditional method can not detect the existence of a legal monitoring end, so that the multi-antenna suspicious sending end adopts Maximum Ratio Transmission (MRT), P and the like under the limitation of the maximum transmitting poweraRepresenting the transmitting power of the multi-antenna suspicious transmitting end, wherein a transmitting beam forming vector w of the multi-antenna suspicious transmitting end is as follows:
Figure BDA0003006136460000091
data receiving phase
Is provided with
Figure BDA0003006136460000092
Representing a direct channel between the multi-antenna suspect transmitter and the single-antenna suspect receiver,
Figure BDA0003006136460000093
representing the reflection channel between a multi-antenna suspect transmitter-an intelligent reflective surface-a single-antenna suspect receiver, x representing a suspect information signal having unity power, nbAnd nekThe average value of additive complex white Gaussian noise signals respectively representing a single-antenna suspicious receiving end and a legal monitoring end is 0, and the variance is respectively
Figure BDA0003006136460000094
And
Figure BDA0003006136460000095
signal y received by single antenna suspicious receiving endbComprises the following steps:
Figure BDA0003006136460000096
and a legal monitoring end:
Figure BDA0003006136460000097
Figure BDA0003006136460000098
Figure BDA0003006136460000099
wherein, ye,1For signals received at the first lawful listener, ye,kFor signals received at the kth lawful interception, yΕFor the signals received by all legal monitoring terminals, k is the number of legal monitoring terminals, the signal-to-noise ratio γ of the single antenna suspicious receiving terminal and the legal monitoring terminalbAnd upsiloneComprises the following steps:
Figure BDA00030061364600000910
Figure BDA00030061364600000911
when gamma ise≥γbAnd if so, the legal monitoring end can successfully decode the suspicious information and can realize successful monitoring, and the monitoring rate is the suspicious communication rate. When gamma ise＜γbIf so, the lawful interception end cannot guarantee error-free decoding of the suspicious information, and cannot realize interception, and the interception rate is 0 at this time, so that the lawful interception event is represented by an indication function as follows:
Figure BDA0003006136460000101
r1 represents that the legal monitoring end successfully monitors suspicious information; and R is 0, which represents that the legal monitoring end fails to monitor the suspicious information.
The system optimization goal is as follows:
according to the above description, in the data transmission stage, not only the lawful interception end can receive the information source signal reflected by the intelligent reflection surface, so as to improve the signal-to-noise ratio, but also the single-antenna suspicious receiving end can receive the information reflected by the intelligent reflection surface, so as to improve the signal strength of the received suspicious information. Therefore, not only should the design of the phase shift matrix of the intelligent reflection surface in the reverse pilot transmission phase be considered to cause information leakage, but also the optimization of the phase shift matrix of the intelligent reflection surface in the data transmission phase should be considered to make the signal concentrate in the direction of the legal monitoring end.
The invention realizes the maximization of the listener and the signal-to-noise ratio by jointly optimizing the intelligent reflecting surface phase shift matrix in the reverse pilot frequency transmission stage and the data transmission stage, wherein,
the optimization problem of the system is as follows:
P1:
Figure BDA0003006136460000102
s.t.γb≥γ0
||w||2≤PT
constraining gammab≥γ0The signal-to-noise ratio of the single-antenna suspicious receiving end is ensured to be higher than a given threshold value, namely, the single-antenna suspicious receiving end is ensured to be capable of correctly decoding information and cannot detect the existence of the legal monitoring end, and the receiving signal-to-noise ratio of the legal monitoring end is larger than that of the suspicious receiving end to ensure successful monitoring. Constraint | | w | | non-conducting phosphor2≤PTThe method is used for power limitation of a multi-antenna suspicious transmitting end, when the total power can not meet the signal-to-noise ratio requirement of a single-antenna suspicious receiving end, the multi-antenna suspicious transmitting end stops transmitting suspicious information, and at the moment, the signal-to-noise ratios of the single-antenna suspicious receiving end and a legal monitoring end are both 0.
The optimization problem P1 is equivalently expressed as:
P2:
Figure BDA0003006136460000111
s.t.
Figure BDA0003006136460000112
||w||2≤PT
wherein, the IRS phase shift matrix phi in the reverse pilot transmission phase0Optimizing:
the lawful interception end controls the IRS phase shift matrix Φ to reflect the pilot sequence from the single antenna suspicious receiving end, so that the channel estimation result of the multi-antenna suspicious receiving end is wrong, and information leakage is caused as much as possible, that is, the optimization problem P3 is:
P3:
Figure BDA0003006136460000113
s.t.
Figure BDA0003006136460000114
the optimization problem P3 is equivalent to:
P4:
Figure BDA0003006136460000115
s.t.
Figure BDA0003006136460000116
wherein phi @ [ phi ]1,φ2,..,φN]H，
Figure BDA0003006136460000117
Because the unit mode is not convex constrained, the optimization problem P4 is still a non-convex problem, the invention adopts a Minimum Maximization (MM) algorithm to solve the optimization problem P4, and the specific solving process is as follows:
the core idea of the minimum maximization algorithm is to first find an approximate upper bound of an objective function, and then iteratively solve an optimal value of the upper bound under a constraint condition, wherein the convergence point is a local optimal point.
Let phikTo satisfy the feasible solution of the optimization problem P4, the next iteration point φk+1The upper bound of the objective function is expressed as:
Figure BDA0003006136460000121
wherein, α @ (λ)max(A)I-A)φk+ n, removing the constant term of the above equation, the optimization problem P4 is equivalent to:
P5:
Figure BDA0003006136460000122
i.e. if and only ifiAnd alphaiWhen the phase difference is equal to each other,
Figure BDA0003006136460000123
maximum, therefore the closed-form optimal solution of the optimization problem P5 is:
Figure BDA0003006136460000124
let k be k +1 and update φkUntil the objective function converges, initializing a feasible point phi0And applying MM algorithm to iteratively solve the optimization problem P3 to obtain the local optimal solution phi of the optimization problem P30。
IRS phase shift matrix phi in data transmission phase1Optimization
The lawful interception end controls the IRS phase shift matrix phi to maximally realize lawful interception and signal-to-noise ratio, namely equivalent to the optimization problem P6:
P6:
Figure BDA0003006136460000125
s.t.
Figure BDA0003006136460000126
and optimizing phi0In the same way, get phi1The local optimal solution, according to the above key steps, is summarized in the following table 1:
TABLE 1
Figure BDA0003006136460000127
Figure BDA0003006136460000131
Simulation experiment
The actual simulation model of the system shown in fig. 2 shows that the number of antennas of the multi-antenna suspicious transmitter ST is 5, which is (0m, 30 m). A plurality of single-antenna legal monitoring end LM mobile Internet of things devices are randomly distributed in an area with the circle center of (160m, 0m) and the radius of 10m for cooperative monitoring. The position of the intelligent reflecting surface is (100m, 30 m). The single antenna suspect receiving end SR is at (100m, 0 m). The intelligent reflection surface is used for reflecting the pilot frequency sequence and enhancing a link between the multi-antenna suspicious sending end ST and the legal monitoring end LM. The noise variance of a multi-antenna suspicious transmitting terminal ST, a single-antenna suspicious receiving terminal SR and a legal monitoring terminal LM is set
Figure BDA0003006136460000132
To cover as many cases as possible, we proceed in total 105And (5) performing secondary simulation. The path loss model is represented by PL ═ PL (PL)0-10ρlog10(d/d0) Given in (c). PL0At a reference distance d of-30 dB0In simulation, suspicious communication two sides, a multi-antenna suspicious transmitting end ST and a legal monitoring end LM, a multi-antenna suspicious transmitting end ST and an intelligent reflecting surface, the intelligent reflecting surface and a single-antenna suspicious receiving end SR respectively are set, and path loss indexes and distances between the legal monitoring ends LM are rho respectivelyb＝ρek＝3，ρAI＝2，ρIb＝ρIk＝2.5。
The simulation verification of the invention is respectively shown as figure 3, figure 4 and figure 5, wherein figure 3 shows the situation that the signal-to-noise ratio of the single-antenna suspicious receiving end SR and the legal monitoring end LM changes along with the number N of the intelligent reflection units under the certain receiving signal-to-noise ratio threshold value of the single-antenna suspicious receiving end SR. Fig. 4 shows the influence of the receiving snr threshold and the number N of reflection units of the single antenna suspect receiving end SR on the average and snr of the lawful interception end LM. Fig. 5 shows that the performance of the present invention is superior to that of the conventional passive listening, and that long-distance listening can be realized.

Claims (6)

1. An intelligent reflector assisted lawful interception implementation method is characterized by comprising the following steps:
in the reverse pilot frequency transmission stage, a legal monitoring end carries out pilot frequency decoy, and reflects a pilot frequency sequence from a single-antenna suspicious receiving end by controlling a phase shift matrix of an intelligent reflecting surface so that channel estimation of a multi-antenna suspicious transmitting end is wrong;
in the data transmission stage, the legal monitoring end controls the phase shift matrix of the intelligent reflecting surface to maximize the signal-to-noise ratio of the legal monitoring end and complete the realization of the intelligent reflecting surface-assisted legal monitoring.
2. The method for implementing intelligent reflector-assisted lawful interception according to claim 1, wherein the pilot sequence from the single-antenna suspicious receiving end is reflected by controlling the phase shift matrix of the intelligent reflector surface, so that the specific process of the multi-antenna suspicious receiving end channel estimation error is as follows:
constructing an optimization problem P3:
Figure FDA0003006136450000011
Figure FDA0003006136450000012
wherein h isbAnd HAIRespectively representing fading channels, h, from a single-antenna suspect receiver and an IRS to a multi-antenna suspect transmitterIbRepresenting the channel from the single antenna suspect receiver to the IRS.
Solving an optimization problem P3 to obtain a phase shift matrix phi of the intelligent reflecting surface in the reverse pilot transmission stage0；
Phase shift matrix phi using smart reflective surfaces0And therefore, the multi-antenna suspicious transmitting end channel estimation is wrong.
3. The method for implementing intelligent reflector-assisted lawful interception according to claim 2, wherein the optimization problem P3 is equivalent to:
Figure FDA0003006136450000021
Figure FDA0003006136450000022
wherein phi @ [ phi ]1,φ2,..,φN]H，
Figure FDA0003006136450000023
hbAnd HAIRespectively representing fading channels, h, from a single-antenna suspect receiver and an IRS to a multi-antenna suspect transmitterIbRepresenting the channel from the single antenna suspect receiver to the IRS.
4. The method of claim 3, wherein the optimization problem P4 is solved by a minimum maximization algorithm to obtain the phase shift matrix Φ of the intelligent reflective surface during the reverse pilot transmission phase0。
5. The method for implementing intelligent reflector-assisted lawful interception according to claim 1, wherein the lawful interception end controls the phase shift matrix of the intelligent reflective surface, so that the specific process of maximizing the signal-to-noise ratio of the lawful interception end is as follows:
constructing an optimization problem P6:
Figure FDA0003006136450000024
Figure FDA0003006136450000025
wherein h isIkIs a channel between the intelligent reflecting surface and the legal monitoring end, hekFor the channel between the multi-antenna suspicious transmitting terminal ST and the plurality of legal monitoring terminals LM, HAIA channel between a multi-antenna suspicious transmitting end ST and an intelligent reflecting surface;
solving an optimization problem P6 to obtain a phase shift matrix phi of the intelligent reflective surface in the data transmission phase1Wherein a phase shift matrix phi of the intelligent reflective surface in the data transmission phase is used1The signal-to-noise ratio of the legal monitoring end is maximized.
6. The method for implementing intelligent reflector assisted lawful interception according to claim 5, wherein the optimization problem P6 is solved by using a minimum maximization algorithm to obtain the phase shift matrix Φ of the intelligent reflector during the data transmission phase1。
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CN113810930A (en) * 2021-08-24 2021-12-17 华北电力大学（保定） Intelligent reflecting surface monitoring optimization method and device and controller

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