Throughput and Delay Analysis on Uncoded and Coded Wireless Broadcast with Hard Deadline Constraints
Abstract
Multimedia streaming applications have stringent QoS requirements. Typically each packet is associated with a packet delivery deadline. This work models and considers realtime streaming broadcast over the downlink of a single cell. The broadcast capacity of the system subject to deadline constraints are studied for both uncoded and coded wireless broadcast schemes. For the uncoded scenario, an optimal transmission policy is devised based on finite-horizon dynamic programming, and a closed-form expression of the optimal throughput is developed in the asymptotic regime, as the size of the file approaches infinity. For the coded scenario, the optimal capacity in the asymptotic regime of large file size is also derived, which is strictly larger than that of the non-coding policies. A simple transmission policy is proposed that can achieve the asymptotic capacity while maintaining finite transmission delay (queueing + decoding dleay). A queue-length-based Lyapunov function is used to show 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.
Date of this Version
5-25-2010