| With the development of wireless communication technology, physical layer security which is based on Shannon theory using channel coding to achieve secure transmission has caused the attention of everybody, therefore we need a reasonable resource allocation scheme to improve transmission rate. Currently, most of the existing resource allocation schemes only focused on system throughput, hence we take the secure relay system as the research carrier, combine with OFDMA and energy harvesting technology, design reasonable and effective resource allocation schemes in order to maximizes the system energy efficiency and the main contents are as follows.Firstly, for multi-user multi-relay secure OFDMA relay system, we propose an efficient resource allocation algorithm with regard to energy efficiency. We formulate the joint optimization problem with the objective to optimize the energy efficiency of the considered system by considering subcarrier pairing, secret data rate and power allocation. In addition, we resolve the problem with dual decomposition method and KKT conditions. The proposed iterative algorithm not only maximizes the system energy efficiency but can guarantee quality-of-service properties.Secondly, in order to prolonging the lifetime of energy constrained relay nodes, we focuses on the resource allocation issue for secure relay system which avail the ambient radio-frequency signal to simultaneously harvest energy and process information. We adopt time switching-based relaying(TSR) protocol to enable energy harvesting and information processing at the relay, and then formulate the joint optimization by considering power allocation and energy harvesting time in order to maximizes the system energy efficiency.Finally, with the advance in antenna technology and signal processing capability, we use full-duplex relaying to recover the spectral loss and improve energy efficiency, where the relay node receives and transmits simultaneously in the same frequency band. |
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