Resource Allocation for Secure Communications in Cooperative Cognitive Wireless Powered Communication Networks

Abstract

We consider a cognitive wireless powered communication network (CWPCN)\nsharing the spectrum with a primary network who faces security threats from\neavesdroppers (EAVs). We propose a new cooperative protocol for the wireless\npowered secondary users (SU) to cooperate with the primary user (PU). In the\nprotocol, the SUs first harvest energy from the power signals transmitted by\nthe cognitive hybrid access point during the wireless power transfer (WPT)\nphase, and then use the harvested energy to interfere with the EAVs and gain\ntransmission opportunities at the same time during the wireless information\ntransfer (WIT) phase. Taking the maximization of the SU ergodic rate as the\ndesign objective, resource allocation algorithms based on the dual optimization\nmethod and the block coordinate descent method are proposed for the cases of\nperfect channel state information (CSI) and collusive/non-collusive EAVs under\nthe PU secrecy constraint. More PU favorable greedy algorithms aimed at\nminimizing the PU secrecy outage probability are also proposed. We furthermore\nconsider the unknown EAVs' CSI case and propose an efficient algorithm to\nimprove the PU security performance. Extensive simulations show that our\nproposed protocol and corresponding resource allocation algorithms can not only\nlet the SU gain transmission opportunities but also improve the PU security\nperformance even with unknown EAVs' CSI.\n