We consider the problem of determining optimal appointment schedule for a given sequence of jobs (e.g., medical procedures) on a single processor (e.g., operating room, examination facility), to minimize the expected total underage and overage costs when each job has a random processing duration given by a joint discrete probability distribution. Simple conditions on the cost rates imply that the objective function is submodular and L-convex. Then there exists an optimal appointment schedule which is integer and can be found in polynomial time. Our model can handle a given due date for the total processing (e.g., end of day for an operating room) after which overtime is incurred and, no-shows and emergencies.

Transmission of time-critical video traffic over the networks with large end-to-end delays poses two main difficulties: slow adaptation to changing network conditions and inability of timely recovery from lost packets. Previously, we proposed a proxy-based solution that enabled us to cope with these problems. Our Internet experiments with a single proxy system showed that the QoS delivered by interactive video applications could be greatly improved by the Intermediate-Proxy approach. In multi-proxy systems, however, the availability of a large number of proxies throughout the Internet will bring the proxy selection problem to the fore. This is an important problem since the benefits of the intermediate-proxy approach can be best exploited with a proper proxy selection. In this study, our goal is to model the dynamics involved in the networks with proxies, and investigate mathematical and practical proxy selection methods.

This paper studies linear prediction algorithms for packet-delay modeling. A detailed examination of the delay traces collected from video streams encoded at different bitrates, suggests that autoregressive (AR) models can exploit the correlation among the delay samples and produce the best estimates in terms of the mean-squared error criterion. Simulation results show that AR prediction can reduce the average prediction-error power significantly as compared to the exponentially-weighted moving average prediction as well as the recursive weighted median filtering. This is a promising result since many layers in the multimedia communication protocol stack, e.g., rate control, error control and network adaptation, can greatly benefit from accurate packet-delay prediction.

This paper studies the streaming of packetized media from multiple servers to a client over a lossy network. In particular, we propose a client-driven rate-distortion optimal packet scheduling algorithm that decides which packet(s) to be requested from which server(s) at a given request opportunity. In doing so, the proposed scheduling algorithm not only attains the maximal presentation quality but also conforms to the rate constraints dictated by the flow, window and congestion control mechanisms. The simulation results clearly demonstrate the efficacy of the proposed algorithm over the single-server rate-distortion optimized streaming.

Multiple description (MD) and layered coding (LC) are two source-coding approaches proposed for adaptive and robust video streaming over lossy networks. Both streaming methods aim to improve the streaming quality by transmitting the generated multiple sub-bitstreams over partially link-disjoint paths. However, the achieved qualities heavily depend on the media characteristics, path conditions and application requirements. In order to attain the highest quality, we study optimal multi-path selection methods for both MD and LC streaming. The simulations run over an overlay infrastructure show 9.0 - 12.5 dB peak signal-to-noise ratio (PSNR) improvement when the video is streamed over intelligently selected multiple paths instead of the shortest path or maximally link-disjoint paths. By the help of the proposed path selection methods, the end users estimate the expected qualities of MD and LC streaming for the given network conditions and application requirements prior to the streaming, which allows the users to make a choice accordingly.