Energy efficiency performance of cooperative schemes in cognitive radio networks with secrecy

In this paper we investigate energy-efficient cooperation for secrecy in cognitive radio networks. We consider a four-node cognitive scenario where the secondary receiver is treated as a potential eavesdropper with respect to the primary transmission. In particular we consider three transmission schemes for the secondary transmitter, namely pure cooperative jamming, clean relaying, and interference neutralization. We investigate the optimal power allocation at the secondary transmitter for our cognitive channel model to maximize the secondary energy efficiency (EE) under secrecy constraints. We illustrate our analytical results through numerical simulations using a geometrical model, which allows us to compare the EE performance of the different schemes in important scenarios.