Interference communication method based on reflection modulation

Abstract

The invention belongs to the technical field of wireless communication, and particularly relates to an interference communication method based on reflection modulation. The communication system comprises a legal user transmitter, a legal user receiver, a reflection device and an illegal user receiver, and the legal user receiver and the illegal user receiver both receive signals sent by the legal user transmitter and the reflection device. Wherein the legal user receiver can jointly demodulate signals sent by the legal user transmitter and the reflection device, the interference communication method is mainly characterized in that the legal user receiver obtains control information from the legal user transmitter to demodulate the signals sent by the legal user transmitter, and the illegal user receiver obtains the control information from the legal user transmitter to demodulate the signals sent by the legal user transmitter. And control information cannot be acquired, so that interference on demodulation of an illegal user receiver is realized. According to the method, the communication channel of the legal user can be enhanced while the channel of the illegal user is interfered.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless communications, and in particular relates to an interference communication method based on reflection modulation. Background Art

[0002] The electromagnetic wave transmission of wireless communication has a natural broadcasting characteristic, which makes it vulnerable to eavesdropping by illegal users. Therefore, in the context of the widespread application of wireless communication, we need effective technical means to interfere with the eavesdropping behavior of illegal users to ensure the security of communication.

[0003] Interference communication is a technology that uses artificially designed methods to reduce or even destroy the communication link of a specific user. It can be used to interfere with the eavesdropping channel of an illegal user. Traditional interference communication means mainly interfere with eavesdropping users by sending artificial noise. Specifically, the transmitter transmits artificial noise while sending information. Although the receiver can avoid interference through the null space of the channel, this method requires the transmitter to allocate additional power for noise transmission, resulting in high energy consumption and failing to enhance the performance of its own communication link.

[0004] In recent years, reflection modulation has received widespread attention as a new communication method. This method uses a reflection device to modulate the incident signal by changing the reflection coefficient, thereby eliminating the need for high-energy active RF devices and being able to modulate the RF source signal in the environment so that the reflected modulated signal has a certain correlation with the environmental signal. Traditionally, reflection modulation is mainly used to achieve reflection communication, that is, to achieve communication between itself and the receiver through a reflection device. This reflection communication architecture consists of an RF source, a reflection device, and a receiver. The reflection device achieves information transmission by adjusting the amplitude and phase of the incident signal.

[0005] Reflection modulation can also be used to interfere with communications. By cooperating with the ambient RF source, the reflection device can dynamically adjust the reflection coefficient to change the channel characteristics and generate interference signals, making it difficult for illegal users to establish a stable channel model and accurately obtain useful information. In addition, reflection modulation has the characteristics of low power consumption and can use existing communication signals for interference while enhancing the communication performance between legitimate users. Therefore, reflection modulation provides the possibility of achieving low-power interference communication. Summary of the invention

[0006] Based on the prior art, the present invention proposes an interference communication method based on reflection modulation.

[0007] The technical solution adopted by the present invention is:

[0008] An interference communication method based on reflection modulation, establishing a communication system including a legitimate user transmitter, a legitimate user receiver, a reflection device and an illegal user receiver, wherein both the legitimate user receiver and the illegal user receiver receive signals sent by the legitimate user transmitter and the reflection device, wherein the legitimate user receiver can jointly demodulate the signals sent by the legitimate user transmitter and the reflection device; the interference communication method is:

[0009] The reflection coefficient Ψ(n) of the reflection device is set to be controlled by control information, which is sent to the reflection device by a legitimate user transmitter or generated by the reflection device itself;

[0010] At the legitimate user receiver, the signal sent by the legitimate user transmitter is demodulated by acquiring control information from the legitimate user transmitter, or the received signal is jointly demodulated;

[0011] In the illegal user receiver, since the control information cannot be obtained, the demodulation of the illegal user receiver is interfered.

[0012] Furthermore, the control information includes a reflection beamforming pattern Φ and an interference sequence c(n), and the relationship between the reflection coefficient and the control information can be expressed as Ψ(n)=Φc(n), where Φ can be set in the communication process as follows: when the channel information from the legitimate user transmitter to the illegal user receiver is unknown, the diagonal element φ in Φ m , The phase is randomly obtained from the uniform distribution U(0,2π), and its amplitude is fixed to 1; when the channel information is known, the diagonal elements in Φ can be transmitted according to the channel information and the reflection device rate R c The demand is obtained by solving the optimization problem P1. The optimization problem P1 will be described later.

[0013] The interference sequence c(n) is generated by a legitimate user transmitter or a reflection device. When generated by a legitimate user transmitter, the legitimate user receiver directly demodulates the received information by sharing control information with the legitimate user transmitter, and its characteristics are that the amplitude of the sequence symbol c is less than or equal to 1, and the phase obeys the uniform distribution U(0,2π); when generated by a reflection device, the interference sequence includes the transmission information required by the reflection device itself, and its characteristics are that the amplitude of the sequence symbol c is less than or equal to 1. The legitimate user receiver jointly demodulates the signal through the maximum likelihood detection or interference elimination detection method.

[0014] Furthermore, it is assumed that the interference sequence c(n) is generated by the reflection device, and the reflection device modulates the interference sequence c(n) onto the signal s(n) transmitted by the legitimate user transmitter for transmission. c(n) is generated by the transmission information required by the reflection device, and the symbol period is T c ; Define the symbol period of s(n) as Ts ,make s m (n) represents the mth symbol in a c(n) period, M is the multiple of the symbol period sent by the reflection device relative to the symbol sent by the legitimate user transmitter, T c =MT s ; Assuming that the channel information in the communication process has been obtained by the channel estimation method, the signal received by the legitimate user receiver can be obtained as:

[0015]

[0016] Where p is the transmission power, g d represents the equivalent baseband channel from the legitimate user transmitter to the legitimate user receiver, h2 represents the equivalent baseband channel from the reflection device to the legitimate user receiver, h1 represents the equivalent baseband channel from the legitimate user transmitter to the reflection device, n b,m (n) is the receiving noise of the legitimate user receiver, and the noise variance is

[0017] The legitimate user receiver uses joint demodulation to solve the received signal and regards the signal component from the reflection device as s m (n) After the signal has experienced slow fading, the demodulated signal s is obtained m (n) signal-to-noise ratio and corresponding achievable rate:

[0018]

[0019] For signal s m After the demodulation of (n) is completed, c(n) is demodulated using the continuous interference cancellation technique, and the signal-to-noise ratio of the demodulated c(n) is obtained:

[0020]

[0021] Will s m (n) is regarded as a spreading code of length M, and the achievable rate of transmission c(n) of the legitimate user transmitter is obtained:

[0022]

[0023] The signal received by the illegal user's receiver is:

[0024]

[0025] Among them, g1 is the equivalent baseband channel from the reflection device to the illegal user receiver, n e,m (n) is the receiving noise of the illegal user receiver, and the noise variance is

[0026] Since the illegal user receiver cannot obtain the interference sequence, the signal-to-interference-noise ratio and the corresponding achievable rate of the illegal user receiver are:

[0027]

[0028] R e =log2(1+γ e )

[0029] The reflection coefficient of the reflection device is designed by solving the optimization problem P1:

[0030]

[0031] Among them, φ k is the reflection coefficient of the kth antenna of the reflecting device, and K is the number of antennas of the reflecting device.

[0032] The beneficial effect of the present invention is that the present invention can enhance the communication channel of the legal user itself while interfering with the channel of the illegal user. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of the interference communication architecture based on reflection modulation proposed in the present invention;

[0034] Figure 2 Schematic diagram for comparing the security transmission rate performance of the present invention and the traditional method. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with the accompanying drawings:

[0036] The structure of the present invention is as follows Figure 1 As shown, the legitimate user transmitter (Alice) is a single antenna, the receiver (Bob) is a single antenna, the illegal user (Carol) is a single antenna, and the multi-antenna reflection device (Rose) is a multi-antenna K (K≥1). Rose changes the phase of the incident signal by changing its antenna reflection coefficient, and modulates the interference sequence c(n) onto the signal s(n) transmitted by the transmitter. For Bob, it will be designed to jointly demodulate the information from Alice and Rose. In this way, Bob can benefit from the multipath signal provided by Rose, and Rose can complete her communication without generating RF signals. However, since Carol cannot know the interference sequence used by Rose, it cannot identify the signal reflected by Rose, so this part of the signal is natural noise to it and will interfere with its demodulation.

[0037] Consider flat block fading. In each fading block, we use the following symbols and Represents the equivalent baseband channel from the legitimate user's transmitter to its receiver, reflection equipment, and the illegal user's receiver; Represent the equivalent baseband channels from the reflection device to the receiver and the illegal user receiver respectively.

[0038] Let Rose send an interference sequence c(n) in its nth symbol period, c∈{1,-1}, and its symbol period is T c The c(n) sequence may be generated according to the transmission information required for transmission by the reflection device.

[0039] make It represents the signal transmitted by Alice, whose symbol period is T s .in And m (n) represents the mth symbol in a c(n) cycle.

[0040] Since the Rose symbol transmission period is M times the transmitter symbol transmission period (M ≥ 1), we can get T c =MT s . In addition, we assume that all the channel information about Bob and Carol has been obtained by the channel estimation algorithm. Then, we can write the signals received by the legitimate user receiver and the illegal eavesdropping user:

[0041]

[0042] Among them, considering the function mapping of multi-antenna reflection equipment, Φ(c(n))=f(Φ,c(n))=Φc(n), represents the reflected beamforming vector of Rose, represents the AWGN at Bob and Carol, and p represents the transmit power.

[0043] Carol cannot know the interference sequence used by Rose, so when she eavesdrops on the signal transmitted by Alice, the signal reflected by Rose is a kind of interference to her. Therefore, we can get the signal-to-interference-plus-noise ratio (SINR) and the corresponding achievable rate at Carol:

[0044]

[0045] R e =log2(1+γ e ), (4)

[0046] Bob can know the interference sequence used by Rose, so he can use joint demodulation to solve the received signal. Specifically, he will regard the signal component from Rose as s m(n) is the signal after slow fading. So, we can get the demodulated signal s at Bob: m (n) signal-to-noise ratio (SNR) and corresponding achievable rate

[0047]

[0048] In the signal s m After the demodulation of (n) is completed, we can use the successive interference cancellation (SIC) technique to demodulate c(n). We assume that the signal component from Alice's direct link can be perfectly cancelled, so we can get

[0049]

[0050] because When M is large enough, we can get the signal-to-noise ratio of demodulation c(n)

[0051]

[0052] Because a signal transmitted by Rose will cover the signals transmitted by M Alices, s m (n) can be regarded as a spreading code of length M. Thus, we can get the achievable rate of Rose transmission c(n)

[0053]

[0054] Next, the reflection coefficient of the reflective device can be designed by solving the following optimization problem:

[0055]

[0056] The first constraint is the minimum rate required for the reflection device to achieve its own transmission; the second constraint is the modulus constraint of the reflection coefficient of the reflection device.

[0057] In order to illustrate the superiority of this system in interfering with eavesdropping users, we introduced the traditional secure transmission based on multi-antenna reflection equipment as a comparative reference. The specific composition of this reference system is as follows:

[0058] Unlike this design, the multi-antenna reflector in the traditional design does not modulate its own information on the incident signal, so this part of the signal cannot be regarded as interference, but will destroy the channel of the illegal eavesdropping user in a counteracting manner to ensure secure communication. We can derive the signal-to-noise ratio at the legitimate user receiver and the illegal eavesdropping user in this case

[0059]

[0060] Figure 2The security rates of the passive Internet security system combined with symbiotic design and the traditional passive Internet security system under the above scenario are compared for a given transmission power. The simulation parameters are set to path loss L0 = -30dB, and the noise variance at the receiver and the eavesdropping user is The transmission power is p=23dBm.

Claims

1. An interference communication method based on reflection modulation, characterized in that: Establish a communication system including a legitimate user transmitter, a legitimate user receiver, a reflection device and an illegal user receiver, wherein the legitimate user receiver and the illegal user receiver both receive signals sent by the legitimate user transmitter and the reflection device, wherein the legitimate user receiver can jointly demodulate the signals sent by the legitimate user transmitter and the reflection device; the interference communication method is: The reflection coefficient Ψ(n) of the reflection device is set to be controlled by control information, which is sent to the reflection device by a legitimate user transmitter or generated by the reflection device itself; At the legitimate user receiver, the signal sent by the legitimate user transmitter is demodulated by acquiring control information from the legitimate user transmitter, or the received signal is jointly demodulated; In the illegal user receiver, since the control information cannot be obtained, the demodulation of the illegal user receiver is interfered.

2. The interference communication method based on reflection modulation according to claim 1, characterized in that: The control information includes a reflection beamforming pattern Φ and an interference sequence c(n). The relationship between the reflection coefficient and the control information is expressed as Ψ(n)=Φc(n). When the channel information from the legitimate user transmitter to the illegal user receiver is unknown, the diagonal element φ in Φ m , The phase is randomly obtained from the uniform distribution U(0,2π), and its amplitude is fixed to 1; when the channel information from the legitimate user transmitter to the illegal user receiver is known, the diagonal elements in Φ are transmitted according to the channel information and the reflection device rate R c Demand is obtained through; The interference sequence c(n) is generated by the legitimate user transmitter or the reflection device. When it is generated by the legitimate user transmitter, the legitimate user receiver directly demodulates the received information by sharing control information with the legitimate user transmitter; when it is generated by the reflection device, the interference sequence includes the transmission information required by the reflection device itself, and the legitimate user receiver jointly demodulates the signal through maximum likelihood detection or interference elimination detection method.

3. The interference communication method based on reflection modulation according to claim 2, characterized in that: Assume that the interference sequence c(n) is generated by the reflection device. The reflection device modulates the interference sequence c(n) onto the signal s(n) transmitted by the legitimate user transmitter for transmission. c(n) is generated by the transmission information required by the reflection device. The symbol period is T c ; Define the symbol period of s(n) as T s ,make s m (n) represents the mth symbol in a c(n) period, M is the multiple of the symbol period sent by the reflection device relative to the symbol sent by the legitimate user transmitter, T c =MT s ; Assuming that the channel information in the communication process has been obtained by the channel estimation method, the signal received by the legitimate user receiver is: Where p is the transmission power, g d represents the equivalent baseband channel from the legitimate user transmitter to the legitimate user receiver, h2 represents the equivalent baseband channel from the reflection device to the legitimate user receiver, h1 represents the equivalent baseband channel from the legitimate user transmitter to the reflection device, n e,m (n) is the receiving noise of the legitimate user receiver, and the noise variance is The legitimate user receiver uses joint demodulation to solve the received signal and regards the signal component from the reflection device as s m (n) After the signal has experienced slow fading, the demodulated signal s is obtained m (n) signal-to-noise ratio and corresponding achievable rate: For signal s m After the demodulation of (n) is completed, the continuous interference cancellation technology is used to demodulate c(n) and the signal-to-noise ratio of the demodulated c(n) is obtained: Will s m (n) is regarded as a spreading code of length M, and the achievable rate of transmission c(n) of the legitimate user transmitter is obtained: The signal received by the illegal user's receiver is: Among them, g1 is the equivalent baseband channel from the reflection device to the illegal user receiver, n b,m (n) is the receiving noise of the illegal user receiver, and the noise variance is Since the illegal user receiver cannot obtain the interference sequence, the signal to noise ratio and the corresponding achievable rate of the illegal user receiver are: R e =log2(1+γ e ) The reflection coefficient of the reflection device is designed by solving the optimization problem P1: P1: f k |≤1,k=1,…,K Among them, φ k is the reflection coefficient of the kth antenna of the reflecting device, and K is the number of antennas of the reflecting device.

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