Receiver synchronization of continuous media streams is required to deal with delay differences and variations resulting from delivery over packet networks such as the Internet. This function is commonly provided using per-stream playout buffers which introduce additional delay in order to produce a playout schedule which meets the synchronization requirements. Packets which arrive after their scheduled playout time are considered late and are discarded. In this paper, we present the Concord algorithm, which provides a delay-sensitive solution for playout buffering. It records historical information and uses it to make short-term predictions about network delay with the aim of not reacting too quickly to short-lived delay variations. This allows an application-controlled tradeoff of packet lateness against buffering delay, suitable for applications which demand low delay but can tolerate or conceal a small amount of late packets. We present a selection of results from an extensive evaluation of Concord using Internet traffic traces. We explore the use of aging techniques to improve the effectiveness of the historical information and hence, the delay predictions. The results show that Concord can produce significant reductions in buffering delay and delay variations at the expense of packet lateness values of less than 1%.

We study the performance of a unified power control and forward error correction control algorithm for mobile radio systems that attempts to maximize system capacity and minimize transmitter power utilization while satisfying user defined quality of service constraints. The algorithm is distributed, with each individual transmitter-receiver pair determining its own operating point with respect to power and error control parameters. Simulation results from a cellular system with mobile users show that this unified algorithm outperforms the schemes that use power control alone.

Describes the design and analysis of RobustWeb, a scalable and fault-tolerant World Wide Web server cluster that is based on HTTP redirection. The system consists of a set of N back-end document servers and one or more redirection servers which receive the HTTP requests and redirect them to the document servers. A load distribution algorithm is used for initial distribution of the documents on the servers. Given a specific degree of replication k, the distribution algorithm guarantees that at least k replicas of each document are present after document distribution is complete. The redirection servers redirect requests to one of the replicas with a pre-computed redirection probability. When a server fails, the redirection probabilities are recomputed using a novel algorithm based on network flow. Theis enables the load to be approximately balanced among the remaining servers, allowing for graceful degradation of the service in the event of failures. A preliminary prototype of RobustWeb has been implemented.

Investigates channel allocation policies that choose among incoming handover requests to a particular cell. Within a class of non-reserving policies that efficiently utilize the scarce channel resources, the authors identify a most critical first policy that is optimal with respect to handover failure probability. The proof of optimality is accompanied by the description of two techniques to realize the policy in practice. Simulation results that demonstrate its improvement over previous policies are presented as well.