Throughput and Delay Analysis on Uncoded and Coded Wireless Broadcast with Hard Deadline Constraints

Multimedia streaming applications have stringent QoS requirements. Typically each packet is associated with a packet delivery deadline. This work models and considers real-time streaming broadcast for stored-video over the downlink of a single cell. The broadcast capacity of the system subject to deadline constraints are derived for both uncoded and coded wireless broadcast schemes. Even under the deadline requirements, it is shown in this work that network coding is asymptotically throughput-optimal and can strictly outperform the best non-coding policy by analytically quantifying the optimal capacity when the file size is sufficiently large. A simple network coding policy is also proposed that achieves the asymptotic capacity while maintaining finite transmission delay (queueing + decoding delay). A new temporal-queue-length-based Lyapunov function is used to prove the optimality of this policy. Simulation shows that the simple coding policy outperforms the best non-coding policies even for broadcasting files of small sizes.