Joint transceiver design for secure communication with power transfer

In the simultaneous wireless information and power transfer (SWIPT) system, the security becomes a major concern. This is because the energy harvesting (EH) operates with much higher received power than conventional information decoding (ID), which leads the environment vulnerable to eavesdropping. In this work, we propose a joint transceiver design to maximize physical-layer security while guaranteeing the required minimum of the harvested energy. The system under consideration consists of a transmitter (Tx), a receiver (Rx), a cooperative jammer (CJ) and a passive eavesdropper (Eve). The Rx is assumed to be energy-constrained in terms of the operation time or the limited power of a battery, where an EH Rx and an ID Rx are co-located. Based on an employment of the CJ, we jointly optimize the beam-forming vector for the CJ and the limited-resource allocation for the Rx to achieve the system objective. For the structure of the co-located EH and ID Rx, two schemes are investigated such as time switching (TS) and power splitting (PS) whose limited resources are the operation time and power, respectively. The algorithmic solutions are proposed for both TS and PS schemes based on rank-relaxation and Minorization-Maximization (MM) approach. Finally, the numerical results show that the secrecy rate in the SWIPT system can be improved by using the proposed algorithm while guaranteeing the requirement of the harvested energy.