Delay-aware BS-DTX Control and User Scheduling for Energy Harvesting Downlink Coordinated MIMO Systems

In this paper, we propose a two-timescale delay-optimal base station Discontinuous Transmission (BS-DTX) control and user scheduling for downlink coordinated MIMO systems with energy harvesting capability to reduce the complexity and signaling overhead. We show that the two-timescale delay-optimal control problem can be modeled as an infinite horizon average cost Partially Observed Markov Decision Problem (POMDP), which is well-known to be a difficult problem in general. We first obtain some structural results on the optimal control policy and derive equivalent Bellman equation with reduced state space. To reduce the complexity and facilitate distributed implementation, we obtain a delay-aware distributed solution with the BS-DTX control at the BS controller (BSC) and the user scheduling at each cluster manager (CM). Furthermore, we derive the sufficient condition for the data queues to be stable and discuss various design insights