Joint Power Allocation and Relay Selection Scheme in Multiple Untrusted Relay Networks

Untrusted relays might decode the information while forwarding it and lead to threaten the security of the system in some realistic scenarios. The aim of the paper is to maximize the secrecy performance, and therefore on the ground of the cooperative jamming, we propose a novel power allocation-relay selection program in a multi-untrusted relay network where numerous antennas are equipped in the source and the destination simultaneously. Besides, we allow an optimal application of the power allocation factor and the proper selection of the relays, which makes the Ergodic Secrecy Rate (ESR) increased directly. Moreover, the closed-form expressions of the ESR in different scenarios to measure the secrecy performance are acquired. It can be known that the simulation results of the ESR are compliant with the theoretical, especially when Signal-to-Noise Ratio (SNR) is low. Apart from this, the ESR in theoretical values are tested to be approximately equal to the simulation. Compared to other relay selection strategies like partial selection strategy and the Max-Min (MM) selection strategy, the scheme proposed here can get the secrecy performance strengthen better.