Efficient Processing of Real-Time Multi-item Requests with Network Coding in On-demand Broadcast Environments

On-demand broadcast is an effective wireless data dissemination technique to enhance system scalability and capability to handle dynamic user access patterns. Traditional on-demand broadcast is under the assumption that only one data item can be retrieved by mobile clients in each time unit. However, the above constraint limits bandwidth utilization and throughput of broadcast systems. In this paper, we consider data broadcast with network coding in real-time on-demand broadcast environments. We analyze the coding problem in on-demand broadcast and transform it into the problem of finding the maximum clique in graph theory. Based on our analysis, a novel algorithm called ADC is proposed. ADC considers both request overlapping and request timing requirement in request scheduling and fully exploits information about clients' cached and requested data items to implement a flexible coding mechanism. The advantages of our proposed algorithm over other traditional and coding assisted broadcast algorithms are shown through simulation results. Our algorithm not only reduces deadline miss ratio of requests, but also utilizes broadcast channel bandwidth efficiently.