Supporting multi-level quality of services in data broadcast systems

Data broadcasting becomes a popular approach to disseminating information to a large population of mobile clients. Although there are lots of research efforts on addressing the scheduling in data broadcast systems, little attention has been paid to the QoS (Quality of Service) issue, which is crucial to any information dissemination application. To support different levels of QoS, data items could be allocated to multiple logical channels with speeds commensurate with respective QoS levels. Therefore, an online EDF (Earliest Deadline First)-based dispatcher is devised to dispatch data items scheduled in the multi-channel allocation to the single physical channel in data broadcast systems. We prove that no data item dispatched by the dispatcher will be delayed with respect to their subscribed QoS levels. In addition, we prove that, under certain conditions, the EDF-based dispatcher is also applicable in the presence of gaps between data items allocated in a QoS level.