Improved Rate-Energy Tradeoff for Energy Harvesting Interference Alignment Networks

Energy harvesting (EH) from RF signals is being investigated to ensure the perpetual operation of energy-constrained wireless devices. Interference alignment (IA) achieves maximum degrees of freedom (DoF) in a K-user interference channel. In this letter, we propose a novel transceiver to improve rate-energy tradeoff for EH in IA networks, the design of which is a non-convex problem. The proposed transceiver, designed using an iterative algorithm and semidefinite relaxation approach, relaxes the perfect IA condition to improve the rate-energy tradeoff. We also analyze the performance of the proposed transceiver for different antennas configurations and show the existence of a diversity-energy tradeoff for the large EH constraint when there are excess antennas. In this antenna regime, this letter shows that the potential diversity gains can be sacrificed to allow the additional DoF provided by excess antennas to be utilized for EH (to satisfy the large EH constraint) without compromising IA.