Difu Su

Investigating factors influencing QoS of Internet phone

An increasing number of applications are using the Internet for voice transmission, and hence there is a growing demand for the Internet phone. However, the Internet was not originally designed for such isochronous traffic, and it is not clear that it is fully capable of providing the desired quality of service (QoS) for this application. We describe a number of QoS parameters to measure the perceptual quality of audio, including measures of delay, rate and loss. We investigate the factors influencing the QoS of Internet voice, such as packet period and packet size, threshold delay, buffer delay, time slots and Internet sites. We present results from our experiments on how these factors influence the QoS of Internet voice. Based on the results of our experiments, we propose a QoS driven dynamic scheduling algorithm for the real-time transmission of Internet voice packets.

QoS-driven networked continuous media server

This paper describes the design, implementation, and evaluation of a Continuous Media (CM) system including a CM server and CM clients. It has been proven that TCP/IP is not suitable for distributed applications that require high network bandwidth and timing-criticality. UDP/IP is one of the alternatives. However, due to the fact that UDP is a lossy protocol, there will be many issues that arise when implementing distributed CM applications, some of which will be discussed in this report. Moreover, the magic word QoS (Quality of Service) causes other difficulties. Most of the QoS metrics known so far assume that the communication channel is lossless. In this paper, since we use UDP for CM data transmission, we adopt a new QoS metric that is applicable to lossy streams to evaluate the performance of our server.

QoS-based evaluation of file systems and distributed system services for continuous media provisioning ☆

Abstract This paper presents a QoS-based performance analysis of file systems and distributed object services for Continuous Media (CM) provisioning, as well as the details and implementation experiences of a continuous media file system and associated CM servers. For this we have implemented QoS-driven CM servers and the Presto continuous media file system (PFS) in the context of a distributed multimedia application development environment, and validate the performance of PFS against that of the conventional Unix file system through an experimental evaluation. Using our CM server prototype, we next examine the effect of continuous media data delivery on the three different kinds of network protocols such as CORBA, UDP/IP, and TCP/IP, with respect to QoS provisioning and throughput.

A multimedia programming toolkit/environment

This paper provides details and implementation experiences of a multimedia programming language and associated toolkits. The language, a data-flow paradigm for multimedia streams, consists of blocks of code that can be connected through their data ports. Continuous media flows through these ports into and out of blocks. The blocks are responsible for the processing of continuous media data. Examples of such processing include capturing, displaying, storing, retrieving and analyzing their contents. The blocks also have parameter ports that specify other pertinent parameters, such as location, and display characteristics such as geometry, etc. The connection topology of blocks is specified using a graphical editor called the Program Development Tool (PDT) and the geometric parameters are specified by using another graphical editor called the User Interface Development Tool (UIDT). Experience with modeling multimedia presentations in our environment and the enhancements provided by the two graphical editors are discussed in detail.