Outage Minimization for Asymmetric Bi-Directional Relaying with Individual Peak-Power Limits

This paper investigates an optimization problem pertaining to the system outage probability minimization for a bi-directional relaying system. Unlike the currently published works, our system has asymmetric traffic demands, and each node in the system is subject to a peak-power limit. By exploiting short-term or long-term channel knowledge at the transmitters and with the support of the traffic knowledge, the optimization problem is solved analytically, resulting in two power allocation strategies, called short-term and long-term policies, with closed-form solutions for individual transmit-powers at the relay and the sources. Simulation results confirmed the effectiveness of the proposed policies. It is shown that the short-term policy can achieve a significant improvement in the performance of the outage probability, irrespective of symmetric or asymmetric traffics and channels, and meanwhile, the long-term policy is more suitable for asymmetric traffic and channel settings.