School of Computer Science Intranet
Lirong He, Ian Rogers, Lisha He
Real-time multimedia education is becoming an increasingly prevalent part of the Internet with the spread of broadband networks. Via the Internet, users can easily work with other participants by sharing examples, such as in a computer lab. It is convenient for students that they can communicate with teachers at any time and in numerous places. Real-time multimedia systems provide users with a video and audio interface enabling them to see and hear other people. Real-time multimedia facilities for e-learning also can be supplemented by face-to-face teaching in tutorial groups at regular meetings.
Real-time distance learning already makes use of the Internet and network links, but such links can be poor at handling real-time data. Network bottlenecks, variable time delays and network congestion can lead to the multimedia data being severely degraded and ultimately unintelligible. There is a requirement to manage the use of the network traffic so as to maximise the trade-off between multimedia quality and appropriate use of bandwidth.
Techniques exist for the transmission of real-time data over the Internet Protocol (IP), namely the Real-time Transport Protocol (RTP) and the Real-Time Control Protocol (RTCP). We present a new technique for the transmission of real-time data over the transport network layer called the Real-Time Multimedia Transport Control Protocol (RTMTCP). The paper shows the new protocol and control mechanism to be an effective way of improving quality and reducing bandwidth for real-time multimedia distance learning in a way not previously possible.
Building upon the real-time multimedia network protocols, this paper presents a new control method designed for distance learning. This method was developed for application to distance learning specifically over a link between the UK and China. The control method uses feedback and priority weightings to determine whether packets should be sent over the network and if so using which codec. The control method maximizes the quality of the transmitted data in un-congested networks, reduces its bandwidth usage in congested networks and attempts to reduce the chance of making the network congested.
The new RTMTCP method is prototyped and evaluated against the existing RTP/RTCP based schemes. Models of the UK and China network link, the control mechanism, the feedback mechanisms, the means for automatic priority detection and the real-time distance learning system were created. Our evaluation shows RTMTCP to be an improvement over RTCP for real-time distance learning.