3. Multi-Objective Resource Allocation Optimization for SWIPT in Small-Cell Networks

In this chapter we consider time switching (TS) simultaneous wireless information and power transfer (SWIPT) for a small-cell network consisting of multiple multi-antenna access points (APs) that serve multiple single antenna user equipments (UEs). In this scenario, we address the jointly optimized design of spatial precoding and TS ratios under a multi-objective optimization (MOO) framework. Our goal is to maximize a utility vector including the data rates and harvested energies of all UEs simultaneously. This problem is a non-convex rank-constrained MOO problem which is transformed into a non-convex semidefinite program using the weighted Chebyshev method. We propose an algorithm based on majorization–minimization approach to solve this problem. Numerical results are provided to demonstrate the performance of the proposed beamforming and TS algorithm in terms of harvested energy-data rate trade-off. The effect of different parameters on this trade-off is also investigated to get a general overview for the practical design of the network.