Delay minimization in energy constrained wireless communications

In wireless communications and networks, the average delay packets experience is an important quality of service criterion. Therefore, it is imperative to design advanced transmission schemes to jointly address the goals of reliability, high rates and low delay.

I will first talk about the delay-optimal rate allocation in a multiple access wireless communication system. The goal is to allocate rates to users, from the multiple access capacity region, based on their current queue lengths, in order to minimize the average delay of the system. We formulate the problem as a Markov decision problem (MDP) with an average cost criterion. We show that the queue-length balancing policy is delay-optimal. Next, we extend the problem into a communication channel where the underlying rate region is approximated as a general pentagon. We show that the delay-optimal policy has a switch curve structure. For the discounted-cost problem, we prove that the switch curve has a limit along one of the dimensions.

Then, I will introduce the transmission completion time minimization problem in energy harvesting communication systems. Under a deterministic system setting, I develop optimal off-line scheduling policies which minimize the transmission completion time in a single-user channel and an AWGN broadcast channel, under causality constraints on energy arrivals.