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Achievable Sum-Rate Maximizing AF Relay Beamforming Scheme in Two-Way Relay Channels

This paper deals with design of a amplify-and- forward (AF) relay beamforming matrix in a two-way relay protocol when a relay node has multiple antennas. Two-way relaying is a promising protocol since it provides enhanced spectral efficiency compared to one-way relaying protocols. In this paper we derive the achievable sum-rate upper bound of AF beamforming scheme and propose the achievable sum-rate maximizing relay beamforming scheme when the destination and the relay node have perfect knowledge of the channel state information (CSI) for forward and backward channels. The solution of the sum-rate maximizing scheme is obtained by using the proposed algorithm, general power iterative algorithm, which solves a global optimization problem efficiently. Comparing with one-way relaying protocol, the improved sum-rate performance of the proposed scheme is verified by numerical simulation.