Network-Coded Two-Way Relaying in Spectrum-Sharing Systems With Quality-of-Service Requirements

摘要

We investigate the performance of a dual-hop two-way cognitive radio system, where the secondary users (SUs) exchange information in an underlay mode with the assistance of a half-duplex relay utilizing physical-layer network coding over finite GF(2). Moreover, we consider a practical scenario of interference from the primary users (PUs) affecting the relay and source nodes. The analysis provides a generalization of previous works as it considers an extended transmission system where the channels can consist of a combination of independent and identically distributed (i.i.d.) and independent but non-identically distributed (i.n.i.d.) Nakagami- m fading models. In addition, unlike prior works, this paper focuses on the performance of both the PUs and the SUs. Closed-form expressions for the symbol error probability (SEP) and the outage probability of the intended PU are obtained. In addition, we derive exact closed-form expressions for the SEP with consideration of special cases of practical interest (e.g., no interference power, interference limited, and single dominant interference cases) for the SUs. Furthermore, an upper bound on the achievable rate of the secondary system is provided. Subsequently, a closed-form approximating expression for the SEP of the secondary system at high signal-to-noise ratios (SNRs) is obtained. Simulation results are provided and attest to the accuracy of the analytical results.