Transmit Power Control for Secure Wireless-Powered Sensor Networks With Malicious Energy Harvester

We consider a wireless-powered sensor network (WPSN) in which multiple transmitting and receiving node pairs communicate with each other, and the nodes not involved in the communication process harvest energy from the transmitted radio signals. These transmitted signals are a source of energy to the harvesting nodes but are exposed to the risk of eavesdropping from them. To prevent this potential eavesdropping from the malicious harvesting nodes while supplying sufficient energy to the legitimate harvesting nodes, this study investigates the transmit power control (TPC) by considering that the transmit power affects the data rates of legitimate and eavesdropping links as well as the amount of harvesting energy. Specifically, we formulate an optimization problem to determine the optimal transmit powers that maximize the sum secrecy rate while ensuring that the minimum required amount of energy is harvested at the harvesting nodes. To solve this problem, we first propose a centralized TPC algorithm based on a dual method considering its nonconvexity. Subsequently, we present a distributed TPC algorithm based on dual decomposition considering limited channel information. Extensive simulations show that both the TPC algorithms achieve a higher sum secrecy rate while ensuring the minimum required harvesting energy compared to conventional schemes that do not adaptively control transmit powers.