A Secure Simultaneous Wireless Information And Power Transmission System Based On CDMA Architecture

Energy harvesting is a promising solution to prolong the operation time of energy-constrained wireless networks. In particular, saving energy from ambient radio signals, namely wireless energy harvesting(WEH), has recently drawn significant attention. Simultaneous information and power transfer(SWIPT) over the wireless channels is a front direction which is the fusion of wireless information transmission technology and wireless energy transmission technology. And SWIPT potentially offers great convenience to mobile users. SWIPT actually refers to the emission of electromagnetic wave transmission using the same energy and information. The receiver harvests energy and decodes information by the electromagnetic wave.We discuss two types of practical receiver architectures, separated versus integrated information and energy receivers. Due to the limitations of hardware, we propose dynamic time switching and dynamic power splitting(DPS) receiver operation. Under dynamic time switching scheme, we discuss the optimal mode switching rule to achieve various trade-offs between information decoding(ID) and energy harvesting(EH) modes at the receiver. Specifically, we study the minimum transmission outage probability for limited delay information transfer and the maximum ergodic capacity for no delay information transfer versus the maximum average energy harvested at the receiver. Under dynamic power splitting(DPS) scheme, we study the optimal power splitting rule at the receiver to achieve various trade-offs between the maximum ergodic capacity for information transfer and the maximum average harvested energy for power transfer. Moreover, we investigate three special cases of DPS.In view of the security issue of the SWIPT system, this paper presents a secrecy SWIPT communication system based on code division multiple access(CDMA) architecture firstly. Based on the CDMA downlink SWIPT system model, we research the composite CDMA signal, the channel state information and the hybridinformation and energy harvesting receiver. Although the eavesdroppers can receive all the information sent by the transmitter, they are unable to correctly despread or decrypt information without spreading polynomials of legitimate users. Secure information transmission is thereby achieved. Our design advocates the dual use of artificial noise and energy signals in providing secure communication and facilitating efficient wireless energy transfer. We formulate resource allocation, system capacity, encryption capacity algorithm design as optimization problems. We research efficient SDP algorithm to obtain the global optimal resource allocation solution. Based on DPS scheme, we formulate a power allocation optimisation problem under the transmit power constraint and the energy harvesting constraint and solve it. It is shown from simulations that the proposed optimal power allocation scheme outperforms the conventional uniform power allocation scheme. Moreover, a modified adaptive allocation algorithm of orthogonal-variable-spreading-factor(OVSF) code is proposed for the new system. The algorithm can effectively improve the system throughput, reduce the blocking probability and waiting time by the user. Simulation also verifies the effectiveness of the improved adaptive OVSF allocation algorithm...