Performance Analysis of Cognitive Relay Networks With RF Hardware Impairments and CEEs in the Presence of Primary Users’ Interference

Abstract

In this paper, we analyze the performance of a cognitive decode-and-forward multi-relay network (CDFMRN) with a direct link under the joint impact of transceiver hardware impairments (HIs) and channel estimation errors. We consider a practical scenario in which the secondary nodes are confronted with the interference from multiple primary users. Hereby, we take into account the hardware distortions induced by all the non-ideal secondary nodes and residual interferences originating from imperfect channel estimations. Considering these imperfections, we derive an exact closed-form expression for the outage probability of CDFMRN by employing selection cooperation between direct and relaying links over Nakagami- ${m}$ fading channels. We illustrate that HIs may invoke different ceiling effects into the system, namely relay cooperation ceiling (RCC), direct link ceiling (DLC), and overall system ceiling. Importantly, we show the detrimental impact of these prevailing effects on the system’s performance and eventually provide useful insights into the endurable level of HIs for designing the practical systems with a given rate requirement. We manifest analytically that a potential direct link and a relaying link can partially compensate for the incurred performance losses due to RCC and DLC effects, respectively. Moreover, we investigate the robustness of amplify-and-forward and decode-and-forward relaying schemes against the HIs. Finally, numerical and simulation results are presented to validate our theoretical findings.