The study of optimal transmission

for real-time FGS videos over WLAN

Abstract

With the technology advances in digital compression and wireless networks, real-time streaming of video content over IEEE 802.11 wireless networks is a multimedia application full of potentials. However, transmission over the error-prone channels by using larger packet size results in higher packet error rate, while transmission by using smaller packet size is inefficient because of the fixed overheads. Both of them reduce the utilization of bandwidth. Meanwhile, IEEE 802.11 wireless networks are relatively unreliable due to an error prone physical channel and the lack of QoS guarantee. Therefore, the video quality transmitting over wireless networks will possibly be degraded.

In the thesis, we propose an optimal transmisission mechanism. First, in order to optimize the utilization of bandwidth, the optimal packet size will be decided by using analyses according to the error situation, transmission overheads, scheduling delay, transmission delay, and number of connections. Base on the optimal size of packets, the priority ARQ in the IEEE 802.11 point coordinator adapts the repeat limits depend on the video packet priorities to achieve both high channel utilization and good video quality. Simulation results show that with ten error patterns and three video sequences, the proposed mechanism indeed achieves maxmum utilization of bandwidth over all IPv6/IPv4 IEEE 802.11b/a/g wireless network. Meanwhile, the proposed mechanisms can improve the PSNR by 1 to 2dB on average under wireless channels with the range of mean burst error length from 1 to 10 bits at the range of bit error rate from 2×10-4 to 8×10-5.