Optimal power allocation for asymmetric analogue network coding in cognitive radio

In this study, the optimal power allocation (OPA) problem is studied for the two-way relay channel employing the analogue network coding protocol with the asymmetric traffic requirements in a cognitive radio network. The OPA scheme is proposed by maximising the sum-rate of the success delivery bit from the secondary user (SU) perspective subject to the sum-power constraint and the interference power threshold (IPT) constraints to the primary user (PU). In particular, for the purpose of accomplishing the power allocation more realistically, the interference to each other between the PU and the SU and the relay is taken into consideration and by solving the optimisation problem composed for each case, the closed form expressions of each node power are obtained. All the simulation results have demonstrated that the system with the proposed scheme outperforms the equal power allocation (EPA) scheme irrespective of the IPT. When the IPT constraint is introduced, the sum-rate of the success delivery bit of the SU communication converges to a certain level with the increasing total power. Meanwhile, the proposed strategy is superior to the conventional EPA scheme for any relay location, which is more remarkable when the relay is located on either end node regardless of the traffic symmetry or the asymmetry.