Battery state based power and time allocation in wireless powered MIMO uplink transmission

Abstract

In this paper, we study a radio frequency (RF) wireless energy transfer (WET) enabled multiple input multiple output (MIMO) system which consists of a base station (BS) and a user equipment (UE) with a finite capacity battery. A time slotted transmission pattern is considered. Each slot can be divided into two phases, downlink (DL) WET and uplink (UL) wireless information transmission (WIT). The battery State-Of-Charge (SOC) which is defined as the ratio of energy available in the current battery to battery capacity is considered. Given a fixed SOC, the maximum acceptable charging power of the battery is determined, which provides an idea for the BS to reduce energy loss at the UE by adjusting transmission power. The optimization problem is formulated to minimize the transmission energy. The problem is proved convex and a power and time allocation algorithm is proposed to achieve an optimal solution. The numerical results show that our proposed algorithm has better performance than other existing schemes.