Joint Resource Allocation in SWIPT-Based Multiantenna Decode-and-Forward Relay Networks

In this paper, we consider relay-assisted simultaneous wireless information and power transfer (SWIPT) for two-hop cooperative transmission, where a half-duplex multiantenna relay adopts decode-and-forward relaying strategy for information forwarding. The relay is assumed to be energy-free and needs to harvest energy from the source node. By embedding power splitting (PS) at each relay antenna to coordinate the received energy and information, joint problem of determining PS ratios and power allocation at the multiantenna relay node is formulated to maximize the end-to-end achievable rate. We show that the multiantenna relay is equivalent to a virtual single-antenna relay in such a SWIPT system, and the problem is optimally solved with closed form. To reduce the hardware cost of the PS scheme, we further propose the antenna clustering scheme, where the multiple antennas at the relay are partitioned into two disjoint groups, which are exclusively used for information decoding and energy harvesting, respectively. Optimal clustering algorithm is first proposed but with exponential complexity. Then, a greedy clustering algorithm is introduced with linear complexity and approaches to the optimal performance. Several valuable insights are provided via theoretical analysis and simulation results.