Analog spatial decoupling for tackling the near-far problem in wirelessly powered communications

Abstract

A practical architecture for wirelessly powered communications (WPC) with dedicated power beacons (PBs) deployed in existing cellular networks, called PB-assisted WPC, is considered in this paper. Assuming those PBs can access to backhaul network and perform simultaneous wireless information and power transfer (SWIPT) to the energy constrained users, the near-far problem in the PB-assisted WPC system is first identified. Specifically, the significant difference of the received power of SWIPT signal (from a PB) and information transfer (IT) signal (from a base station) due to different transmission ranges leads to extremely small signal-to-quantization-noise ratio (SQNR) for the IT signal after quantization of the mixed signals. To retrieve the information carried by the SWIPT and IT signals respectively, it is essential to decouple the strong SWIPT and the weak IT signals in analog domain. To this end, a novel technique called analog spatial decoupling using only simple components such as phase shifters and adders is proposed in this paper. In particular, for the single-PB case, the optimal Fourier based and Hadamard based schemes are proposed for implementing the analog spatial decoupling. For the multiple-PB case, the corresponding design problem is more challenging, making it hard to extend the solution for the single-PB counterpart. To tackle this problem, a systematic solution approach is proposed for analog decoupling with multiple PBs.