Background
As a key technology for solving the problems of channel fading and energy attenuation, the relay technology is particularly suitable for being combined with an energy-limited network. The wireless energy collection technology is a key technology particularly suitable for solving the problem of energy shortage of an energy-limited network. Therefore, the combination of relay technology and energy harvesting technology is of great significance for the research of energy-limited networks.
In recent years, a cooperative transmission mode for improving the physical layer security performance by using a trusted relay attracts more and more attention. There are three main relay protocols for cooperative secure transmission: amplify-and-forward and decode-and-forward. For these protocols, the most common design goal is to maximize the safe rate by properly selecting the beamforming weights of the relay peer. The amplifying and forwarding strategy is simple, and is more generally applicable to relay nodes in various scenes. However, the problem of secure beamforming with an amplify-and-forward strategy is more difficult to solve because the relay end amplifies the noise. To address this problem, a suboptimal and conservative approach is a null-space beamforming approach, i.e., one that places the information beam entirely within the null of the eavesdropper. But the null-space based beamforming schemes are not fully utilized in terms of spectral efficiency and energy efficiency.
Disclosure of Invention
In order to solve the problems of the existing relay transmission technology, the invention aims to provide a wireless energy-carrying relay system for guaranteeing information safety, which can realize that information beams and energy beams of relays are aligned to target users, improve the utilization rate of frequency spectrums and energy resources of a relay wireless communication system, and guarantee the information communication safety of the system.
The invention also provides a wireless energy-carrying relay method for guaranteeing information safety.
The relay system adopts the following technical scheme: a wireless energy-carrying relay system for guaranteeing information security comprises: the system comprises a source end, a plurality of relay ends, a legal receiving end, an energy collecting end and an eavesdropper, wherein the source end is connected with the relay ends; each relay terminal is respectively connected with the source terminal, the legal receiving terminal, the energy collecting terminal and the eavesdropper;
the method comprises the steps of constructing a safe reachable rate maximization problem which guarantees safe communication of a physical layer and meets wireless energy constraint and independent power constraint of each relay end, and obtaining a local optimal safe beam forming matrix on each relay end which guarantees safety of the physical layer through an alternative optimization method.
Preferably, the wireless energy-carrying relay system is a two-hop amplification forwarding multi-relay network, and each relay terminal is provided with N antennas; the energy receiving end is provided with M antennas; the source end, the legal receiving end and the eavesdropper are all provided with single antennas.
Preferably, there is no direct link connection between the source end and the legal receiving end, and in the first time slot, the source end sends a signal to the relay end; in the second time slot, the relay terminal multiplies the received signal by a beam forming matrix and forwards the signal to a legal receiving terminal and an energy receiving terminal, and meanwhile, an eavesdropper eavesdrops.
The relay method adopts the following technical scheme: a wireless energy-carrying relay method for guaranteeing information security comprises the following steps:
s1, in the two-hop amplification multi-relay network, each relay terminal is respectively connected with a source terminal, a legal receiving terminal, an energy collection terminal and an eavesdropper; each relay terminal is provided with N antennae, the energy receiving terminal is provided with M antennae, and the source terminal, the legal receiving terminal and the eavesdropper are provided with single antennae;
order to
Respectively representing channels from a source end to a kth relay end, from the kth relay end to a legal receiving end and from the kth relay end to an eavesdropper;
represents a channel from the kth relay terminal to the energy receiving terminal;
and
are independent identically distributed complex Gaussian random variables with zero mean and unit variance; f
k∈C
N×NA beamforming matrix representing the kth relay peer,
σ
2additive white Gaussian noise Power, P, for a legitimate receiver and an eavesdropper
sFor source side transmit power, F ═ diag (F)
1,F
2,…,F
K),
Let the wireless energy constraint be:
wherein
Representing a channel from the kth relay terminal to an energy receiving terminal, wherein Q is a preset energy collection threshold of the energy receiving terminal;
making the individual power constraint of each relay as:
wherein, PkMaximum allowable transmission power for the kth relay node;
the safe reachable rate for ensuring the safe communication of the physical layer and meeting the wireless energy constraint and the independent power constraint of each relay terminal is as follows:
s2, constructing a safe reachable rate maximization problem which ensures the safe communication of the physical layer and meets the wireless energy constraint and the independent power constraint of each relay end, and comprising the following steps:
wherein the content of the first and second substances,
rank 1 relaxation is performed on the above-mentioned safe achievable rate maximization problem, order
And
solving a local optimal solution of the above rank 1 relaxation problem;
s3, initializing, wherein n is 0, and n is the iteration number;
X
nis KN
2×KN
2Is a positive number, calculating R
s(X
n);
S5, fixing
Solving the following convex optimization problem by using an interior point method to obtain X
n+1:
S6, n ═ n +1, and R is calculated
s(X
n+1) Alternately updating through S2 and S3
And X
n+1Until convergence, i.e. R
s(X
n+1)-R
s(X
n) Is less than an element; obtaining a locally optimal solution X to the
rank 1 relaxation problem
*=X
n+1;
S7, if X*Is a rank 1 solution, and obtains an optimal rank 1 solution f of the safe reachable rate maximization problem through characteristic decomposition*If X is*Instead of a rank 1 solution, a suboptimal rank 1 solution f of the safe reachable rate maximization problem is obtained through Gaussian randomization; finally, the F is matrixed to obtain a beam forming matrix F of each relayk。
The invention can ensure that the frequency spectrum and energy resources are effectively and fully utilized while the relay transmission system ensures the safe communication of the physical layer, and solves the problem of maximizing the safe rate of the multi-relay system by optimally designing the beam forming matrix of each relay terminal. Compared with the prior art, the invention has the following effective effects:
the safe reachable rate maximization problem for guaranteeing the safe communication of the physical layer is constructed, the safe beam forming matrix of each relay end is obtained through an alternative optimization method, and the safe reachable rate of the system is locally optimal while the wireless energy constraint and the independent power constraint of each relay end are met. The invention can realize that the information wave beam and the energy wave beam of the relay aim at the target user, improves the frequency spectrum and the energy resource utilization rate of the relay wireless communication system, and simultaneously ensures the information communication safety of the system.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited to these examples.
Examples
As shown in fig. 1 to 4, the wireless energy-carrying relay system for guaranteeing information security of the present invention includes: the device comprises a source end, a plurality of relay ends, a legal receiving end, an energy collecting end and an eavesdropper, wherein each relay end is respectively connected with the source end, the legal receiving end, the energy collecting end and the eavesdropper. The wireless energy-carrying relay system is a two-hop amplification forwarding multi-relay network, and in the embodiment, the wireless energy-carrying relay system comprises K multi-antenna relay terminals, and each relay terminal is provided with N antennas; the energy receiving end is provided with M antennas; the source end, the legal receiving end and the eavesdropper are all provided with single antennas. Assuming that no direct link connection exists between the source end and the legal receiving end, in a first time slot, the source end sends a signal to the relay end; in the second time slot, the relay terminal multiplies the received signal by a beam forming matrix and forwards the multiplied signal to a legal receiving terminal and an energy receiving terminal, and meanwhile, an eavesdropper eavesdrops. Considering that the relay node knows the channel state information of the whole network, the whole two-hop amplification forwarding multi-relay network works in a time division multiplexing mode.
The invention constructs a safe reachable rate maximization problem of ensuring the safe communication of a physical layer and meeting the wireless energy constraint and the independent power constraint of each relay terminal based on the relay beam forming matrix optimization algorithm of the alternative optimization, and obtains the local optimal safe beam forming matrix on each relay terminal of the wireless energy-carrying relay system for ensuring the safety of the physical layer by the alternative optimization method.
In this embodiment, let
Respectively representing channels from a source end to a kth relay end, from the kth relay end to a legal receiving end and from the kth relay end to an eavesdropper;
representing the channel from the kth relay peer to the energy receiving peer,
P
kmaximum allowable transmission power for the kth relay node; f
k∈C
N×NA beamforming matrix representing the kth relay peer,
σ
2the power of additive white Gaussian noise at a legal receiving end and an eavesdropper is obtained; p
sTransmitting power for the source end; q is a preset energy collection threshold of an energy receiving end; the safe achievable rate is:
the wireless energy constraints are:
the individual power constraint of each relay is as follows:
wherein, PkThe maximum allowable transmission power for the kth relay node.
The safe reachable rate maximization problem of ensuring the safe communication of the physical layer and meeting the wireless energy constraint and the independent power constraint of each relay terminal is constructed as follows:
wherein the content of the first and second substances,
the objective function of the above optimization problem is the safe achievable rate; the first constraint is the independent power constraint of each relay terminal; the second constraint is a wireless energy constraint; the optimization variables are vectorized representations of the beamforming matrices for each relay.
And solving the safety reachable rate maximization problem based on the alternative optimization.
Rank 1 relaxation, i.e., ordering, is first performed on the above-described safe achievable rate maximization problem
Ignoring the non-convex
rank 1 constraint, converting the safe achievable rate maximization problem into the following
rank 1 relaxation problem:
Tr(D6X)≥Q.
wherein:
and:
solving the locally optimal solution of the above rank 1 relaxation problem comprises the following steps:
(1) initializing, wherein n is 0 and n is iteration times;
X
nis KN
2×KN
2Is a very small positive number, calculate R
s(X
n);
(3) Fixing
Solving the following convex optimization problem by using an interior point method to obtain X
n+1:
(4) n is n +1, and R is calculated
s(X
n+1) Alternately updating through the step (2) and the step (3)
And X
n+1Up to R
s(X
n+1) Convergence, i.e. R
s(X
n+1)-R
s(X
n)<∈。
(5) Obtaining a locally optimal solution X of the rank 1 relaxation problem*=Xn+1。
If X is*Is a rank 1 solution, and obtains an optimal rank 1 solution f of the original safe reachable rate maximization problem through characteristic decomposition*If X is*Instead of a rank 1 solution, a suboptimal rank 1 solution f of the original safe reachable rate maximization problem is obtained through Gaussian randomization. Finally, the F is matrixed to obtain a beam forming matrix F of each relayk。
Referring to fig. 4, the wireless energy-carrying relay method for guaranteeing information security of the embodiment specifically includes the following steps:
step 1, in a two-hop amplification multi-relay network, each relay terminal is provided with 2 antennas, an energy receiving terminal is provided with M antennas, and a source terminal, a legal receiving terminal and an eavesdropper are all provided with a single antenna.
If no special statement, P in simulation implementation
s/σ
2=10dB,Q/σ
2=2dB,M=2,
σ 21. Assuming all channel responses
And
are independent identically distributed complex gaussian random variables with zero mean and unit variance. 500 random channel realizations were generated in the simulation to calculate the average achievable security rate. Individual relay power constraint P
kThe settings were as follows: p when k is odd
k=0.5P
rK, P when K is an even number
k=2P
rand/K. Let F
k∈C
N×NA beamforming matrix representing the kth relay peer,
step 2, constructing a safe reachable rate maximization problem which ensures the safe communication of the physical layer and meets the wireless energy constraint and the independent power constraint of each relay end, and comprising the following steps:
wherein the content of the first and second substances,
rank 1 relaxation is performed on the above-mentioned safe achievable rate maximization problem, order
And
the locally optimal solution of the above rank 1 relaxation problem is solved.
Step 3, initializing, wherein n is 0, and n is iteration times;
X
nis KN
2×KN
2Is a very small positive number, calculate R
s(X
n);
Step 4, fixing X
nSolving for
Step 5, fixing
Solving the following convex optimization problem by using an interior point method to obtain X
n+1:
And 6, alternately updating through the step (2) and the step (3)
And X
n+1Until convergence, i.e. R
s(X
n+1)-R
s(X
n) Is < ∈. Obtaining a locally optimal solution X of the
rank 1 relaxation problem
*=X
n+1。
Step 7, if X*Is a rank 1 solution, and obtains an optimal rank 1 solution f of the original safe reachable rate maximization problem through characteristic decomposition*If X is*Instead of a rank 1 solution, a suboptimal rank 1 solution f of the original safe reachable rate maximization problem is obtained through Gaussian randomization. Finally, the F is matrixed to obtain a beam forming matrix F of each relayk。
By the embodiment, the performance effect graph of fig. 2, in which the average achievable safe rate changes with the relay transmission power, and the convergence performance effect graph of fig. 3, in which the alternating iterative algorithm is used, can be obtained. It can be seen from both sets of curves in fig. 3 that when the sum power at the relay is small, the average achievable safe rate without energy constraint is greater than the case where the energy constraint is 6dB, and the average achievable safe rate with 6dB energy constraint is greater than the case where the energy constraint is 10 dB. It can also be seen from fig. 3 that the average achievable safety rate of each energy constraint of the relay number K-4 is greater than the average achievable safety rate of each energy constraint of the relay number K-2. The performance curves of fig. 3 demonstrate the rationality and effectiveness of the system.
It can be seen from fig. 2 that the number of iterations increases with increasing power, and when the transmission sum power of the relay terminal is 20dB, the number of iterations is about 20. The performance curve of fig. 2 shows the fast convergence of the proposed alternate optimization based secure relay beamforming algorithm in the system.
The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be regarded as being equivalent to the scope of the present invention.