Hybrid Spatial-Modulation Based Virtual MIMO Relaying Protocol with SWIPT

In this paper, we propose a novel hybrid spatial-modulation (SM) based virtual MIMO relaying protocol with simultaneous wireless information and power transfer (SWIPT). The multiple relay nodes (RNs) employ a dualhop half duplex (HD) decode-and-forward (DF) protocol and harvest the radio frequency (RF) energy from the source node (SN) with the power splitting (PS) SWIPT method used. In the first hop, pre-coding aided spatial modulation (PSM) technique is used, where a portion of relay nodes (RNs) are activated to receive the transmitted signals with the zero-forcing (ZF) linear pre-coding employed at the source node (SN). The received signals at the RNs are divided into two parts by the power splitter denoted as energy signals and information signals. In the second hop, the information signals are transmitted from the active RNs to the destination node (DN) with the harvested energy, which makes the information transmission for this link SM-like. With the capacity upper bound (UB), the optimal system throughput can be analyzed and water-filling power allocation method is utilized to further boost the system throughput. With the additional information carried by the indices of the RNs, the proposed protocol can demonstrate better throughput performance against both the best RNs selection (BRS) and fix RNs (FR) virtual MIMO relaying schemes with the similar PS-SWIPT method and computation complexity. The Montecarlo simulations are conducted to verify our theoretical analysis.