Video streaming over wireless LANs using handheld devices.

摘要

In this thesis we propose the design and evaluation of an IEEE 802.11-based network architecture for wireless video streaming to the handheld devices. A multimedia streaming client application is designed for Pocket PC 2002, which is built on the core of window CE platform. The client application works with a QuickTime Darwin streaming server that supports all unicast, multicast and broadcast transport protocols. The client application supports unicast transport and MPEG4 video and MP3 audio decoding, where RTSP (Real Time Streaming Protocol) is used for session initialization and control, SDP (Session Description Protocol) for session description, and RTP/RTCP (Real time Transport Protocol/RTP Control Protocol) for packet transmission. The test bed consists of an IEEE 802.11b-based wireless LAN, a streaming server and a streaming client for wireless video streaming. The streaming performance over wireless links in terms of packet loss ratio, processing time and streaming video quality is compared with that over wired links. In addition, the memory usage in mobile devices has also been analyzed. The experiment results show that the performance bottleneck is at the synchronization and memory copies, which takes up most of the CPU time. The quality of video streaming over the wireless links is not as good as that over the wired links mainly due to the higher packet loss over the wireless links. Finally, the optimization to the current client implementation has been proposed to improve the memory utilization and application portability. The functional extension of the streaming server has also been proposed.