| With the development in computer and network technology over the past years, it seems that data transmission alone is not satisfactory, and the multimedia especially video communication has been paid more and more attention. Compared with traditional network application, video streaming consumes larger quantities of network bandwidth, and has rigider delay constraints, but can tolerate some packet losses. Unfortunately, the current best-effort IP network does not offer any QoS guarantee for streaming video. On the other hand, with the dramatic increase in the number of Internet users and diversity means of access, heterogeneous characteristics of networks are becoming increasingly prominent. There is big difference between the processing capacity, link bandwidth, and line reliability and so on for different end-users. The ultimate goal of video transmission is to meet their video quality QoS requirement for these heterogeneous users.Currently some different video transmission scehmes have been proposed, such as source-based adaptive rate control, receiver-based simulcast and layered multicast, but these schemes basically follow the traditional network design principles and take end-to-end congestion control and error control mechanisms without the participation of network intermediate nodes, making a series of problems such as session management difficulty, congestion control blindness, feedback explosion, and the difficulty in achieving fairness among different users.To address these issues, on the basis of discussing the video multicast, IP QoS and active networks in detail, the video coding and transmission over IP network have been conducted research in-depth, and some major issues to network video multicast have been resolved in this paper. The main results of work and research in this paper are as follows:Firstly, in view of the characteristics of MPEG-4 FGS coding and FGS encoder and decoder based on the bit-plane DCT coefficients coding, the impact of FGS characteristics on video multicast is analysed, and then FGS coding scheme is regarded as an approach for obtaining the scalable compressed video. Because the enhancement layer frame of the FGS coding can be truncated at any desired portion, end-users can receive the most appropriate video quality. This makes video multicast in heterogeneous network flexible and also improves the efficiency of the network.Secondly, a novel scalable video multicast using active networks, SVM-AN scheme has been proposed in this paper. Using the processing capacilty of intermediate nodes within the active network, this scheme ensures that the receivers will receive base layer information, filter out part of the lower priority enhancement layer beyond subscribing video qulaity, to adapt the network bandwidth and processing capacity of heterogeneous users, and to meet their different QoS requirement. Meanwhile, through merging video quality subscriptions and feedback information of downstream nodes, this sheme restrains feedback implosion effectively and has improved network throughout capacity also.Thirdly, receiver-driven distributed active congestion control mechanism has been adopted in SVM-AN scheme. It makes heterogeneous network users obtain best possible fair QoS while solving netwok congestion control. Through measuring round trip time and packet loss rate, every video receiver estimates independently TCP friendly available bandwidth of its upstream virtual link, and determines dynamicly its subscribed video quality.Lastly, compared with the traditional end-to-end receiver-driven layered multicast scheme, simulation results show that the SVM-AN scheme proposed in this paper has simplified the management of multicast session, avoided global oscillation induced by blind join and leave session of receivers. Meanwhile, through fine granularity video transmission rate adjustment, SVM-AN scheme has satisfied different video quality reqirements for heterogeneous network users, and improved overall network utilization efficiency.
|
PDF Full Text Request