Wireless Packet Scheduling With Soft Deadlines

We address the problem of scheduling multiple traffic streams associated with target profiles on a shared wireless link, arising in real-time applications with soft/flexible deadline constraints (e.g. multimedia streaming). A target profile specifies the inter-packet deadline constraints for a user´s traffic stream, or equivalently, the time instants at which the user should ideally receive packets to ensure uninterrupted multimedia playout. Contention for the shared link and fluctuations in wireless channel quality prevent users from being served in accordance with their desired target profiles. The goal of the scheduler is to dynamically schedule users to ensure that their target profiles are adhered to as closely as possible. We formulate the scheduling problem in a dynamic programming (DP) framework. Leveraging key structural properties of the optimal control to the DP, we propose our heuristic MinProj scheduling policy. We experimentally demonstrate the efficacy of MinProj over benchmark schedulers. The computational complexity of MinProj grows only linearly with the number of users in the system. Further, MinProj is agnostic to statistical assumptions on input traffic or channel behavior. These features make MinProj an attractive policy to implement in real wireless systems.