Secrecy analysis of amplify-and-forward relaying networks with zero forcing

In this study, the ergodic secrecy capacity and the corresponding outage probability of two-hop amplify-and-forward relaying system in the presence of a passive eavesdropper are analysed. In order to improve the security, in this study, zero-forcing (ZF) scheme is implemented at different locations in the system. The effect of the ZF-based scheme on the system security is considered for three different scenarios, based on where the ZF scheme is applied, namely, (i) ZF receivers at the relay and destination nodes, (ii) ZF precoders at the source and relay nodes, and (iii) ZF precoders/receivers at the relay nodes. For each scenario, explicit analytical expressions for the ergodic secrecy capacity and secrecy outage probability are derived. Monte Carlo simulations are also provided to validate the analysis. Results show that increasing the number of source, relay and/or destination nodes can be favourable or unfavourable to the system security and the significance of this enhancement/degradation depends on the particular scenario deployed. In addition, the system security improves with increasing the source and/or relay power.