阅读说明：本技术 基于方向调制的无线网络最大化安全速率功率分配方法 (Wireless network maximum safe rate power distribution method based on direction modulation ) 是由 李镇洋 张宇萌 李嘉钰 束锋 李灏宸 王天云 王宇 黄悦丰 桂林卿 钱玉文 于 2019-08-26 设计创作，主要内容包括：本发明公开了一种基于方向调制的无线网络最大化安全速率功率分配方法,包括以下内容：建立方向调制基本模型；根据方向调制基本模型获取信道的安全速率；采用零空间投影构建人工噪声投影矩阵和有用信息波束成型向量；结合前述的安全速率以及人工噪声投影矩阵和有用信息波束成型向量获取关于功率分配因子的最大化安全速率函数；根据最大化安全速率函数求取使得安全速率最大的最佳功率分配因子,即完成最大化安全速率功率分配。本发明利用最大化安全速率准则求得最佳功率分配因子,求解方法更加简洁,能达到期望方向信噪比最大化、非期望方向信噪比较小的效果,且方法适用于任意人工噪声投影矩阵和有用信息波束成型向量给定的情形,适用范围比较广。(The invention discloses a wireless network maximum safe speed power distribution method based on direction modulation, which comprises the following steps: establishing a direction modulation basic model; acquiring the safety rate of a channel according to a direction modulation basic model; adopting null space projection to construct an artificial noise projection matrix and a useful information beam forming vector; acquiring a maximum safe rate function related to the power distribution factor by combining the safe rate, the artificial noise projection matrix and the useful information beam forming vector; and solving the optimal power allocation factor which enables the safe speed to be maximum according to the maximum safe speed function, namely completing the maximum safe speed power allocation. The method utilizes the maximum safe rate criterion to obtain the optimal power distribution factor, has more concise solving method, can achieve the effects of maximum signal-to-noise ratio in the expected direction and small signal-to-noise ratio in the non-expected direction, is suitable for the conditions of any artificial noise projection matrix and given useful information beam forming vector, and has wider application range.)

1. The wireless network maximum safe speed power distribution method based on the direction modulation is characterized by comprising the following steps:

step 1, establishing a direction modulation basic model;

step 2, obtaining the safe speed of the channel according to the direction modulation basic model;

step 3, adopting null space projection to construct artificial noise projection matrix P_ANAnd useful information beamforming vector v_b；

Step 4, combining the safety rate of step 2 and P of step 3_ANAnd v_bObtaining maximization with respect to power allocation factor betaSafe rate function R_s(β)；

Step 5, according to the maximized safe rate function R_s(beta) finding the optimal power allocation factor beta that maximizes the safe rate^*I.e. to achieve maximum safe rate power allocation.

2. The method for maximizing safe rate power distribution of a wireless network based on directional modulation according to claim 1, wherein the formula of the basic model of directional modulation in step 1 is as follows:

in the formula, P_sFor the total antenna transmitter power, z is the artificial noise vector, s is the digital baseband signal, and x is the desired signal.

3. The method for maximizing safe rate power distribution of a wireless network based on directional modulation according to claim 1 or 2, wherein the step 2 of obtaining the safe rate of the channel according to the basic model of directional modulation specifically comprises:

step 2-1, the received signals in the expected direction and the undesired direction of the constructed channel are respectively as follows:

desired direction reception signal y (theta)_b) Comprises the following steps:

in the formula, the superscript H represents the conjugate transpose of the matrix, n_bIs Gaussian noise in the desired direction, θ_bThe direction angle of the expected direction is defined, and h is a channel normalized guide vector;

receiving signal y (theta) in undesired direction_e) Comprises the following steps:

in the formula, n_eIs out of phaseGaussian noise in the look direction, θ_eAn undesired directional angle;

step 2-2, combining the received signals in the expected direction and the undesired direction, and obtaining the safety rates of the expected direction and the undesired direction of the channel according to the direction modulation basic model, wherein the safety rates are respectively as follows:

safe rate R (theta) of desired direction_b) Comprises the following steps:

wherein σ is a gaussian distribution standard deviation of gaussian noise;

safe rate R (theta) of undesired direction_e) Comprises the following steps:

step 2-3, on the basis of the step 2-1 and the step 2-2, combining the definition of the channel safety rate to obtain a channel safety rate R (beta, P)_AN,v_b) Comprises the following steps:

in the formula, P_sTransmitting total power for the antenna array, SNR is signal to noise ratio, h (theta)_b) A steering vector of a desired direction, h (θ)_e) Is a steering vector of an undesired direction, beta is a power allocation factor, sigma²Is the variance of the noise gaussian distribution.

4. The method for maximizing safe rate power distribution of wireless network based on directional modulation as claimed in claim 3, wherein said step 3 employs null space projection to construct artificial noise projection matrix P_ANAnd useful information beamforming vector v_bThe method specifically comprises the following steps:

step 3-1, projecting the artificial noise vector z to a zero space of the conjugate transpose of the guide vector in the expected direction:

h^H(θ_b)(z-ζh(θ_b))＝0

and solving for ζ as:

step 3-2, substituting the solved zeta into z-zeta h (theta)_b) Constructing an expression of an artificial noise projection matrix:

z-ζh(θ_b)＝(I_N-h(θ_b)h^H(θ_b))z

P_AN＝I_N-h(θ_b)h^H(θ_b)

in the formula I_NAn identity matrix of NxN;

step 3-3, taking the guide vector in the expected direction as a useful information beam forming vector:

v_b＝h(θ_b)。

5. the method of claim 4, wherein the step 4 combines the safe rate of step 2 and the P of step 3_ANAnd v_bObtaining a maximum safe rate function R with respect to a power allocation factor beta_s(β) is:

s.t.0≤β≤1

wherein the content of the first and second substances,

order:

a(β)＝Iβ²+Jβ+K

b(β)＝Mβ+K

then the above-mentioned R_sThe formula for (β) is simplified as:

6. the method of claim 5, wherein the step 5 is based on a function of maximizing safe rate R_s(beta) finding the optimal power allocation factor beta that maximizes the safe rate^*The method specifically comprises the following steps:

step 5-1, maximizing safe rate function R_s(beta) carrying out derivation, and obtaining a derivative expression under the condition of an extreme value by simplifying:

IMβ²+2KIβ+K(J-M)＝0.

then solving the stagnation point of the one-dimensional quadratic equation according to different values of the coefficient IM as follows:

when IM is not equal to 0 and Delta is not less than 0, the stationary point beta₁,β₂Comprises the following steps:

when IM is equal to 0, the stationary point beta₃Comprises the following steps:

and step 5-2, determining the value of the optimal power distribution factor according to the value of the coefficient IM and the stationing point, specifically:

A. when IM is equal to 0, the stagnation point is beta₃The method comprises the following steps:

(1) when beta is₃Belongs to (0,1), and takes max [ phi (0), phi (beta)₃),φ(1)]The corresponding power distribution factor is the optimal power distribution factor;

(2) when in use

B. when IM is not equal to 0, finding out Delta K²I²-KIM(J-M)：

(1) When Δ ≧ 0:

if beta₁E (0,1) and beta₂Belongs to (0,1), and takes max [ phi (0), phi (beta)₁),φ(β₂),φ(1)]The corresponding power distribution factor is the optimal power distribution factor;

if beta₁Is epsilon (0,1) andtake max [ phi (0), phi (beta) ]₁),φ(1)]The corresponding power distribution factor is the optimal power distribution factor;

③ if

fourthly if

(2) when Δ < 0:

if IM is greater than 0, the function phi (beta) is monotonously increased to obtain the optimal power distribution factor beta for maximizing the function value^*＝1；

If IM is less than 0, the function phi (beta) is monotonously decreased to obtain the optimal power distribution factor beta which can make the function value maximum^*＝0。

Technical Field

The invention belongs to the technical field of wireless communication, and particularly relates to a wireless network maximum safe rate power distribution method based on directional modulation.

Background

The security of wireless networks has a wide range of implications, including confidentiality, integrity, identity authentication, access control, availability, and the like. From the perspective of information theory, which follows the information encryption and decryption techniques in traditional wired communications, e.g., data encryption standards and advanced encryption standards, the above-mentioned wireless security problem has been addressed at the level of the upper layer protocol stack. However, the secure channel and its security protocol required by the encryption system are still difficult to guarantee, and the distribution and management of its keys may also generate security holes of the system. On the other hand, since such techniques mainly depend on the complexity of the key algorithm, with the continuous improvement of computing power and deciphering means, such as the development of quantum computers, the classical encryption system no longer meets the current requirement for improving the security performance. Due to the nature of broadcast in wireless transmission, how to ensure the security of private information is becoming a very important issue in wireless networks. As an emerging wireless network physical layer security technology, directional modulation has received close attention from both academic and industrial fields.

The principle of the directional modulation is that by adding a correct phase deviation value to a transmitting array element, amplitude and phase of a required symbol can be generated in an expected direction after digital modulation, and the amplitude and the phase are distorted in other directions, so that the transmission of information is safely guaranteed. The signal modulated by continuously applying the phase shift to the radio frequency end can generate different constellations in different directions, realizes encryption effect on physical waveforms, and is called a direction modulation signal.

After the basic model principle of directional modulation is clear, the power allocation is considered as the key technology of directional modulation in the paper "basic principle, key technology and future prospect of wireless safe transmission based on directional modulation", and due to the limited transmitter power of the communication system, the reasonable allocation of power to useful signals and artificial noise is crucial to the safety performance of the communication system. In order to more strictly derive a Power Allocation method by using AN algorithmic manner, AN OPA Strategy for Maximizing a safe Rate (Max-SR) is proposed in a later paper "Power Allocation Strategy of maximum reliable Rate for a Power Allocation network", and AN analytic expression of the PA Strategy can be derived by using a lagrange multiplier method given AN arbitrary beamforming vector and AN projection matrix at a DM transmitter. After a strict method for deriving Power Allocation is provided, in order to enable an algorithm to optimize performance indexes of a communication system, an article "Alternating objective Secure Structure between beam forming and Power Allocation for UAV-aided direct modulation networks" proposes an OPA strategy based on SLNR, designs a beam forming vector and an artificial noise projection matrix by using a Max-SLNR method, and calculates an optimal Power Allocation factor through AIS.

But the existing method still has the defects of the design aspects of useful information beam forming vectors and artificial noise projection matrixes of a directional modulation model, and firstly, the beam forming vectors at the end of a given DM transmitter and the AN projection matrixes have randomness; secondly, the conditions of a non-conspiracy eavesdropper and a conspiracy eavesdropper are not discussed at the same time; thirdly, there is a certain randomness to the power allocation, and the optimization problem is often a multivariable problem, and the obtained result is not necessarily accurate.

Disclosure of Invention

The invention aims to provide a method for obtaining a power distribution factor which enables the system safety rate and the signal-to-noise ratio to be maximum by comparing the power distribution factor typical value with the safety rate and the signal-to-noise ratio under an optimization scheme by utilizing the specific change rule relation that the safety rate and the signal-to-noise ratio change along with the power distribution factor.

The technical solution for realizing the purpose of the invention is as follows: the wireless network maximum safe speed power distribution method based on the direction modulation comprises the following steps:

step 1, establishing a direction modulation basic model;

step 2, obtaining the safe speed of the channel according to the direction modulation basic model;

step 3, adopting null space projection to construct artificial noise projection matrix P_ANAnd useful information beamforming vector v_b；

Step 4, combining the safety rate of step 2 and P of step 3_ANAnd v_bObtaining a maximum safe rate function R with respect to a power allocation factor beta_s(β)；

Step 5, according to the maximized safe rate function R_s(beta) finding the optimal power allocation factor beta that maximizes the safe rate^*I.e. to achieve maximum safe rate power allocation.

Compared with the prior art, the invention has the following remarkable advantages: 1) Max-SR is taken as a target through a maximum safe rate power distribution strategy, a beam forming vector is designed by using a matched filtering method, and an artificial noise projection matrix is designed by adopting a null space projection method, so that the effects of maximization of the signal-to-noise ratio in an expected direction and small signal-to-noise ratio in an unexpected direction can be achieved; 2) the problem of the maximum safe speed is converted into a univariate optimization problem, and then the expression of the optimal power distribution factor is solved, so that the solving method is simpler; 3) the method is suitable for the situation that any artificial noise projection matrix and useful information beam forming vector are given by adopting null space projection, and has wider application range.

The present invention is described in further detail below with reference to the attached drawing figures.

Drawings

FIG. 1 is a schematic diagram of power allocation according to the present invention.

Fig. 2 is a graph of bit error rate as a function of steering angle in an embodiment of the present invention.

Fig. 3 is a graph of the safe rate as a function of the power allocation factor β (SNR 10dB) in an embodiment of the present invention.

Fig. 4 is a graph of safe rate as a function of power allocation factor β (SNR 15dB) in an embodiment of the present invention.

Fig. 5 is a graph of safe rate as a function of power allocation factor β (SNR 20dB) in an embodiment of the present invention.

Fig. 6 is a histogram of the safe rate as a function of the number of antennas N in an embodiment of the present invention (β is 0.5, SNR is 5 dB).

Fig. 7 is a histogram of the safe rate as a function of the number of antennas N in an embodiment of the present invention (β ═ 0.5, SNR ═ 15 dB).

Fig. 8 is a histogram of the safe rate as a function of the number of antennas N in an embodiment of the present invention (β is 0.5, SNR is 25 dB).

Fig. 9 is a graph of the optimum power allocation factor β as a function of SNR for different numbers of antennas in the embodiment of the present invention.

Detailed Description

With reference to fig. 1, the method for maximizing safe rate power allocation of a wireless network based on directional modulation according to the present invention includes the following steps:

step 1, establishing a direction modulation basic model;

step 2, obtaining the safe speed of the channel according to the direction modulation basic model;

step 3, adopting null space projection to construct artificial noise projection matrix P_ANAnd useful information beamforming vector v_b；

Step 4, combining the safety rate of step 2 and P of step 3_ANAnd v_bObtaining a maximum safe rate function R with respect to a power allocation factor beta_s(β)；

Step 5, according to the maximized safe rate function R_s(beta) is found so that safety is goodOptimal power allocation factor beta for maximum rate^*I.e. to achieve maximum safe rate power allocation.

Further, the formula of the basic model of the direction modulation in step 1 is as follows:

in the formula, P_sThe total power of an antenna transmitter is represented, z is an artificial noise vector, s is a digital baseband signal, and x is a useful signal;

further, in step 2, the secure rate of the channel is obtained according to the direction modulation basic model, which specifically includes:

step 2-1, the received signals in the expected direction and the undesired direction of the constructed channel are respectively as follows:

desired direction reception signal y (theta)_b) Comprises the following steps:

in the formula, the superscript H represents the conjugate transpose of the matrix, n_bIs Gaussian noise in the desired direction, θ_bThe direction angle of the expected direction is defined, and h is a channel normalized guide vector;

receiving signal y (theta) in undesired direction_e) Comprises the following steps:

in the formula, n_eIs Gaussian noise in an undesired direction, θ_eAn undesired directional angle;

step 2-2, combining the received signals in the expected direction and the undesired direction, and obtaining the safety rates of the expected direction and the undesired direction of the channel according to the direction modulation basic model, wherein the safety rates are respectively as follows:

safe rate R (theta) of desired direction_b) Comprises the following steps:

wherein σ is a gaussian distribution standard deviation of gaussian noise;

safe rate R (theta) of undesired direction_e) Comprises the following steps:

step 2-3, on the basis of the step 2-1 and the step 2-2, combining the definition of the channel safety rate to obtain a channel safety rate R (beta, P)_AN,v_b) Comprises the following steps:

in the formula, P_sTransmitting total power for the antenna array, SNR is signal to noise ratio, h (theta)_b) A steering vector of a desired direction, h (θ)_e) Is a steering vector of an undesired direction, beta is a power allocation factor, sigma²Is the variance of the noise gaussian distribution.

Further, in step 3, a null space projection is adopted to construct an artificial noise projection matrix P_ANAnd useful information beamforming vector v_bThe method specifically comprises the following steps:

step 3-1, projecting the artificial noise vector z to a zero space of the conjugate transpose of the guide vector in the expected direction:

h^H(θ_b)(z-ζh(θ_b))＝0

and solving for ζ as:

step 3-2, substituting the solved zeta into z-zeta h (theta)_b) Constructing an expression of an artificial noise projection matrix:

z-ζh(θ_b)＝(I_N-h(θ_b)h^H(θ_b))z

P_AN＝I_N-h(θ_b)h^H(θ_b)

in the formula I_NAn identity matrix of NxN;

step 3-3, taking the guide vector in the expected direction as a useful information beam forming vector:

v_b＝h(θ_b)。

further, step 4 combines the safety rate of step 2 with the P of step 3_ANAnd v_bObtaining a maximum safe rate function R with respect to a power allocation factor beta_s(β) is:

s.t.0≤β≤1

wherein the content of the first and second substances,

order:

a(β)＝Iβ²+Jβ+K

b(β)＝Mβ+K

then the above-mentioned R_sThe formula for (β) is simplified as:

further, step 5 is based on maximizing the safe rate function R_s(beta) finding the optimal power allocation factor beta that maximizes the safe rate^*The method specifically comprises the following steps:

step 5-1, maximizing safe rate function R_s(beta) carrying out derivation, and obtaining a derivative expression under the condition of an extreme value by simplifying:

IMβ²+2KIβ+K(J-M)＝0.

then solving the stagnation point of the one-dimensional quadratic equation according to different values of the coefficient IM as follows:

when IM is not equal to 0 and Delta is not less than 0, the stationary point beta₁,β₂Comprises the following steps:

when IM is equal to 0, the stationary point beta₃Comprises the following steps:

and step 5-2, determining the value of the optimal power distribution factor according to the value of the coefficient IM and the stationing point, specifically:

A. when IM is equal to 0, the stagnation point is beta₃The method comprises the following steps:

(1) when beta is₃Belongs to (0,1), and takes max [ phi (0), phi (beta)₃),φ(1)]The corresponding power distribution factor is the optimal power distribution factor;

(2) when in useTake max [ phi (0), phi (1)]The corresponding power distribution factor is the optimal power distribution factor;

B. when IM is not equal to 0, finding out Delta K²I²-KIM(J-M)：

(1) When Δ ≧ 0:

if beta₁E (0,1) and beta₂Belongs to (0,1), and takes max [ phi (0), phi (beta)₁),φ(β₂),φ(1)]The corresponding power distribution factor is the optimal power distribution factor;

if beta₁Is epsilon (0,1) andtake max [ phi (0), phi (beta) ]₁),φ(1)]The corresponding power distribution factor is the optimal power distribution factor;

③ if

And beta is₂Belongs to (0,1), and takes max [ phi (0), phi (beta)₂),φ(1)]The corresponding power distribution factor is the optimal power distribution factor;

fourthly if

And is

Take max [ phi (0), phi (1)]The corresponding power distribution factor is the optimal power distribution factor;

(2) when Δ < 0:

if IM is greater than 0, the function phi (beta) is monotonously increased to obtain the optimal power distribution factor beta for maximizing the function value^*＝1；

If IM is less than 0, the function phi (beta) is monotonously decreased to obtain the optimal power distribution factor beta which can make the function value maximum^*＝0。

The present invention will be described in further detail with reference to examples.