Scheduling real-time multi-item requests in on-demand broadcast

On-demand broadcast is an effective wireless data dissemination technique to enhance system scalability and capability to handle dynamic user access patterns. Previous studies on time-critical on-demand data broadcast were under the assumption that each client requests only one data item at a time. With rapid growth of time-critical information dissemination services in emerging applications, there is an increasing need for systems to support efficient processing of real-time multi-item requests. Little work, however, has considered on-demand broadcast environment with time-critical multi-item requests. In this paper, we investigate the scheduling problem arising in this new environment and observe that existing single item request based algorithms are unable to manage multi-item requests efficiently. Thus, an innovative algorithm that combines the strengths of data item scheduling and request scheduling is proposed. The performance results of our simulation show that the proposed algorithm is superior to other classical algorithms under a variety of circumstances. Our algorithm not only reduces deadline miss ratio of requests, but also saves broadcast channel bandwidth.