Optimal Power Allocation for OFDM-Based Two-Way Relaying in Cognitive Radio Networks

Power allocation for orthogonal frequency division multiplexing (OFDM) based two-way relay link in cognitive relay networks is discussed in this paper. Two secondary source nodes exchange their information through a secondary relay node by using amplify-and-forward two-way relaying strategy. The goal of power allocation is to maximize the sum data rate of the secondary system subject to the constraint that the aggregation interference of the secondary system on the primary system does not exceed the given threshold. In addition, individual node power constraint is applied for both secondary source nodes and the secondary relay node. We solve the optimization problem by using dual decomposition approach, and further propose a distributed power allocation algorithm. Numerical results demonstrate the advantage of the proposed algorithm over uniform power allocation. Besides, power-constrained as well as interference-constrained regions are shown in our numerical experiments.