A probabilistic scheduling algorithm for providing Proportional Delay Differentiation in content-based online charging system

The emergence of new data services in 3G networks is driving the support of advanced content-based billing mechanisms whose unique characteristics require that the OCS (online charging system) provide relative differentiated services based on different contents. The OCS can be modeled by the PDD (proportional delay differentiation) structure and it aims to maintain the prespecified mean system response-time delay ratios between different classes of requests. A novel request scheduling algorithm is proposed in this paper. The basic idea is that one of the requests from all classes of service queues is chosen with some priority probability which is based on the system queue-length, the request arrival rate, and the preassigned delay differentiation parameter. The experimental results show that this new algorithm significantly outperforms some other traditional PDD scheduling ones when request service delays increase and vary greatly from each other. Furthermore, it can efficiently meet 6 QoS requirements proposed in this paper.