This paper presents the power allocation solution in single link Multi-Input Multi-Output (MIMO) wireless communication systems powered by harvested energy. We first derive the channel capacity with non-causal full information in a finite time horizon, which is shown to be a convex optimization problem. The optimal power allocation can be obtained through Spatial-Temporal Water-Filling (ST-WF) solution, by which harvested energy is first allocated among antennas and then among time slots. For the causal information condition, we propose three suboptimal policies, namely constant water level policy, capacityaware water level policy and energy-aware water level policy. Their performance is evaluated by numerical simulations, which show that the energy-aware water level policy is the best among them.
Spatial-Temporal Water-Filling Power Allocation in MIMO Systems with Harvested Energy