earticle

영어

A cross-layer optimization video transmission scheme, which includes two mechanisms, is proposed in this paper. The first is the encoding adjustment mechanism to handle buffer insufficiency. Large frames are divided into several sub-frames and the maximum number of packets in these sub-frames depends on the minimum buffer size in forwarding path. In addition, sending time of adjacent frames or sub-frames should be separated. And time intervals between adjacent frames or sub-frames are determined by the numbers of packets those frames or sub-frames have. The second is the priority based transmission mechanism to handle bandwidth insufficiency. Different dropping probabilities or scheduling opportunities are assigned to different frame types. Less important frames always have a high dropping probability or a small scheduling opportunity. In performance evaluation, various video sequences, buffer sizes and bandwidth reservations are employed. Simulation results verify that: (1) Cross-layer optimization is adaptive to different video sequences, buffer sizes and bandwidth reservations. That is to say, it is a content and network adaptive scheme. (2) Proposed scheme outperforms existing schemes significantly, especially when buffer size is small or bandwidth reservation is large. (3) A further advantage is that priority based transmission mechanism enhances video decoding quality while receives less packets. Thus it is friendly to other streams.