Energy-Efficient Scheduling with Individual Delay Constraints over a Fading Channel

This paper focuses on energy-efficient packet transmission with individual packet delay constraints over a fading channel. The problem of optimal offline scheduling (vis-a-vis total transmission energy), assuming information of all packet arrivals and channel states before scheduling, is formulated as a convex optimization problem with linear constraints. The optimality conditions are analyzed. From the analysis, a recursive algorithm is developed to search for the optimal offline scheduling. The optimal offline scheduler tries to equalize the energy-rate derivative function as much as possible subject to the causality and delay constraints. The properties of the optimal transmission rates are analyzed, from which upper and lower bounds of the average packet delay are derived. In addition, a heuristic online scheduling algorithm, using causal traffic and channel information, is proposed and shown via simulations to achieve comparable energy and delay performance to the optimal offline scheduler in a wide range of scenarios.