Joint Spectrum Sharing and Power Allocation for OFDM-Based Two-Way Relaying

Considering a bidirectional amplify-and-forward based multi-carrier multi-relay network, we formulate two different joint power allocation and network beamforming problems. In the first formulation, we aim to minimize the total transmit power of the network, subject to two constraints on the transceiver rates. In the second problem, our goal is to maximize the sum-rate of the two transceivers subject to a constraint on the total network transmit power. In both problems, the design parameters include the relay beamforming weights and the transceiver power allocations over all subcarriers. We propose a two-step iterative method to tackle each problem and show that each method leads to (at least) a locally optimum solution. Each iterative method alternates between solving the underlying problem for one set of variables while the other set is fixed and vice versa. Each subproblem is shown to be amenable to a computationally efficient solution. Our simulation results show the efficiency of the proposed techniques.