A genetic approach in relay-jammer selection and power allocation for physical layer security

Abstract

Node cooperation approaches improve physical layer security in wireless networks without applying data encryption. Selecting the appropriate nodes to cooperate as relays or friendly jammers, to degrade eavesdropper's link, is a challenging problem which has attracted a lot of attention in recent years. Various approaches, based on conventional exhaustive search, have been suggested for optimal relay-jammer selection and power allocation in the literature. The complexity of these methods is proportional to the number of intermediate nodes. As the number of intermediate nodes exceeds a specific bound, conventional exhaustive search appears infeasible due to high computational complexity. In this paper, we propose a novel approach based on genetic algorithm (GA), for relay-jammer selection, power allocation and computational complexity reduction. Our system model consists of a source-destination pair, one eavesdropper and a number of intermediate nodes which cooperate as relays or friendly jammers. Considering the achievable secrecy rate as the cost function for GA optimization, the proposed algorithm is performed in two steps. First, we determine the desired channel gains that maximize the secrecy rate using GA. In the second step, nodes for which the corresponding channel gains have the smallest deviation from the obtained values in the first step, will be chosen as relays or jammers. We compare the proposed method with two kinds of conventional exhaustive search techniques one with fixed and the other with adaptive power allocated to jammers. Simulation results show that the proposed method reduces computational complexity while attaining a secrecy rate close to conventional techniques. Also the power which is allocated to jammers during each phase of transmission will be declined using GA optimization. Despite of conventional exhaustive search, the complexity of the proposed algorithm is almost the same as the number of cooperative nodes increases. So, the proposed method will outperform the previous works in terms of simplicity, efficiency and security.