Robust video communication over wireless packet networks
Abstract (Summary)This thesis is an investigation of a high performance universal video communication system for mobile (indoor or outdoor) environrnent with an ATM backbone network. This work is in h e with the upcoming MPEG-4 proposals which is king planned for future systems. Channel and Bandwidth constraints in mobile environrnent limit the achievable data rate. However, the end users demand good quality video and would prefer gracefdy degrading video quality with decrease in available Bandwidth. The two main issues addresseci arc video compression and channel adaptation of the system. A good source coder is required to provide high compression gain and gracefully degrading video quality with decrease in the available Bandwidth. Also it is known that variable bit rate (VBR) source coders outperfonn constant bit rate source coders under network aansport conditions. Hence investigation of combination of wavelet transform, multi-resolution motion estimation and zero aee coder is a good choice for VBR video compression at low bit rates. Robust design of zero tree coder is proposed to make the source coder error resistant under hostile environment. We suggest two stages of channel coding, with unequal error protection at the inner stage to better protect the data of higher importance. Varying channel conditions demand dynamicdy changing enor protection for better use of bandwidth. A source level rate controlier is proposed to enable adaptation to the channel conditions and to provide VBR video. The rate controller needs to efficiently analyze the channel conditions and adjust the systern parameters for best performance. It is suggested to sense the charme1 at the receiver and send it as feedback. This information is Mer processed and used by the rate controller to dynamically adapt the system. Outer channel cocüng is suggested to be as per the standard air interface specifications such as in CODIT, DECT etc. Another important system requirement fdfilled is the requirernent of low overhead when the source coder robustness or the channel adaptation are not required. This will be the case at low BER (or CLR) environments. The Robust design of source coder and dynamic channel adaptation of the system without much overhead enables its application in a variety of channei conditions Ue narrowband, broadband, indoor and outdoor.
Source Type:Master's Thesis
Date of Publication:01/01/1997