Research On Secure Transport Methods At Physical Layer In Energy Harvesting And Cooperation Networks

Due to the openness of wireless transmission medium, secure transmission of confidential information is an important issue in wireless communication networks. Eavesdropping is the main way of threating to information security. With the development of computer technology, traditional encryption algorithm, which used to against eavesdropping, faces increasing challenges. Physical layer security utilizes the physical characteristics of the wireless channel at physical layer to achieve secure transmission. With the rapid development of multi-antenna technology and cooperative communication, secure transmission of information at physical layer becomes achievable. Moreover, energy harvesting and energy cooperation can achieve green communication effectively. This thesis studies the physical layer security issues in the energy harvesting and cooperation networks. Beamforming and cooperative communication are adopted to achieve secure transmission at physical layer. The main work is as follows:1. The issue of achieving secure transmission through cooperation jamming and energy cooperation is studied in the system consisting of one source-destination pair, one eavesdropper and one multi-antenna relay. In this scheme, the multi-antenna relay transmits beamformed jamming signals to disturb the eavesdropper. Considering the relay has no energy to transmit jamming signals, the source needs to transfer a portion of its energy. By theoretical analysis, the optimal solution is derived for the amount of energy needed to transfer, transferring time and the beamforming vector of the jamming signals. In the case of the relay does not consume its energy, the simulation results show that the scheme of energy cooperation and cooperation jamming can significantly improve the secrecy rate compared with direct transmission.2. The transmission issue of confidential information is studied when a single-antenna eavesdropper exists in the wireless network that consisting of a single-antenna source, a single-antenna destination and an energy-limited multi-antenna relay. As the available energy of the relay is limited, the relay needs to harvest energy to improve the power of forwarding confidential information. The antennas of relay are divided into two groups, one receiving and forwarding information, and the other converting the received signal into energy to forward information. Beamforming is used by the relay to prevent the eavesdropper from intercepting the confidential information. For the purpose of maximizing the secrecy rate, the schemes of antenna grouping and beamforming are optimized. The optimal ergodic antenna grouping scheme and the low complexity antenna grouping scheme are proposed. The simulation results show that the secrecy rate of the system can be significantly improved by reasonably arranging part of the relay antenna for energy harvesting and optimizing the beamforming scheme of relay.