Scheduling Heterogeneous Real-Time Traffic Over Fading Wireless Channels

We develop a general approach for designing scheduling policies for real-time traffic over wireless channels. We extend prior work, which characterizes a real-time flow by its traffic pattern, delay bound, timely throughput requirement, and channel reliability, to allow clients to have different deadlines and allow a variety of channel models. In particular, our extended model consider scenarios where channel qualities are time-varying, the access point may not have explicit information on channel qualities, and the access point may or may not employ rate adaptation. Thus, our model allows the treatment of more realistic fading channels as well as scenarios with mobile nodes and the usage of more general transmission strategies. We derive a sufficient condition for a scheduling policy to be feasibility optimal, and thereby establish a class of feasibility optimal policies. We demonstrate the utility of the identified class by deriving a feasibility optimal policy for the scenario with rate adaptation, time-varying channels, and heterogeneous delay bounds. When rate adaptation is not available, we also derive feasibility optimal policies for both scenarios where the access point may or may not have explicit knowledge on channel qualities. For the scenario where rate adaptation is not available but clients have different delay bounds, we describe a heuristic. Simulation results are also presented, which indicate the usefulness of the scheduling policies for more realistic and complex scenarios.