Study On The Network Communication Protocol For Interactive Collaboration Environment Of Distance Education

ABSTRACTWith the rapid development of computer, multimedia, network and communication techniques, the research and application of multimedia collaboration on network environments is one of the hottest topics. Distance education ,which characterizes resilient and interactive educational system, provides an important approach to enlarge the scale of education, improve the quality of education and build the lifelong education system in information society by sharing the first-class educational resource without the restriction of time and space, so it attracts more and more attentions and gets very wide application.Distance education presents very high requirement to communication network and protocol. During the living broadcast of teaching, the audio and video of lecture should be delivered to remote students real-timely, data,such as teaching plan, writing on blackboard and courseware and so on, requires the guarantee of reliability of transmission and keep good synchronization with audio/video except for real-time transmission. Interactive collaboration is the basic character of distance education, students can collaborate with other students and lecturer during the procedure of teaching and learning. During the collaboration, the change of status information and collaboration environment should be broadcasted to every participants real-timely and reliably in order to hold the consistency and validity of the collaboration. Traditional communication network and protocols can't meet the requirements of real-time multimedia collaboration. So the research and application of network protocols and techniques for distance education environment is very important and necessary. In the dissertation, we firstly summarize the significance, developing history, research fields, status quo and trends about distance education. We then analyze the characters of distance education and the requirements for multimedia communication network. Based on the techniques of known real-time multimedia communication and computer-supported collaboration ,we present four protocols for distance education environment: sender-initiated grouping and tree based reliable multicast protocols—SITGRMP, receiver-initiated grouping and tree based reliable multicast protocols—RITGRMP, sender-initiated grouping and recovery-group based reliable multicast protocols—SIGRRMP, receiver-initiated grouping and recovery-group based reliable multicast protocols —SIGRRMP.SITGRMP and RITGRMP protocols can recover error locally and balance the load of process among all participants because of grouping and tree model, so it can avoid the process bottleneck caused by centralized error recovery and decrease the number of packets on backbone efficiently. SITGRMP and RITGRMP is designed for one-to-many applications ,such as living broadcast of teaching, exercise distribution, distance examination and so forth.Based on grouping and a novel concept, that is the error-recovery multicast group, we present two protocols: SIGRRMP and SIRIGRRMP.The principle is error-recovery uses another multicast group different from the one for normal data transmission. Once the receiver receives data correctly, it will never receive the retransmission, unnecessary process time is thus avoided. It can improve the throughput and make protocol scalable. SIGRRMP and SIRIGRRMP can support one-to-many and many-to-many application, such as living broadcast of teaching, exercise distribution, distance examination and interactive collaborations based shared environment.We also present the packet buffering, adaptive flow control and congestion control techniques for the reliable multicast protocols. The performance analysis of protocols, including throughput, the number of packets on backbone and routers , packet transmission delay are also given. Finally ,we discuss the implementation of multicast communication, and implement the protocol SIGRRMP.