Research On Wireless Security Transmission Based On Antenna Array

With the arrival of 4G era as well as the upcoming 5G, people feel the convenience and efficiency from the development of information technology. At the same time, people pay more and more attention to the security of communication systems. In order to improve the security of wireless communication systems, physical layer security technology was born as a new research area. This article will use the array antenna technology to the study of physical layer security technology, and seeking the specific schemes of solving security transmission in the physical layer transmission systems.In the physical layer security transmission scheme based on directional modulation, the optimal weight of each antenna in the antenna array is obtained by genetic algorithm. The sender can transmit information to the legitimate user in the desired direction safely and successfully, while the illegal eavesdropper in the other direction can not correctly receive useful information. In simulation, the bit error rates of the legitimate user and the illegal eavesdropper are compared in the occasion of different number of sender’s antennas. As a particular unresolved case exists in this scheme, this article proposes an improved scheme by adding a random antenna selection matrix, so that the transmission system can still get transmission security when the sender, illegal eavesdroppers and the legitimate user are collinear. The applicability of the scheme is enhanced. Then, this article proves the feasibility and correctness of the scheme by simulation.In the physical layer security transmission scheme based on random selection of antennas, the sender obtains channel state information by a transmission request transmitted by the legitimate user which contains the training sequence. According to the channel state information, the sender generates the weights of array antennas, and transmits the signals. Signals can be correctly received by the legitimate user, while illegal eavesdropper can’t receive the signals correctly. To improve the bit error rate of the legitimate user and the power efficiency of the system, an antenna selection matrix is added in this article. The article simulates the sender with 8 antennas transmits signals. The bit error rate of the legitimate user and the eavesdroppers are compared in the occasion of the normal scheme and the antenna selection matrix used scheme. It proves the correctness and feasibility of this scheme. To solve the problem of high peak to average power ratio in this scheme, this article presents a suppression algorithms based on portion transmission sequence. The optimal weights are got by rotational transformation of the original weight of the antenna array. We compare the performance of different packets of 8 antennas system and 16 antennas system. Simulation results show that the proposed scheme reduces the peak to average power ratio value.