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UBC Theses and Dissertations

Performance evaluation and optimization of MPEG-4 video streaming over CDMA wireless networks Luo, Ying

Abstract

With the advent of next-generation multimedia technologies such as the low bit rate MPEG-4 codec, multimedia streaming over third generation (3G) wireless networks becomes a reality. To deal with the error prone and bandwidth limited nature of wireless networks, this thesis presents a novel error control scheme called Adaptive Delay-constrained Selective Repeat ARQ (ADSR-ARQ) in the radio link layer. ADSR-ARQ is capable of dynamically switching between ARQ and non-ARQ mode and adjusts the retransmission attempts based on the predefined transmission buffer length thresholds to satisfy the overall quality of service (QoS) requirements of video streams. An analytical model is created to analyze the feasibility and efficiency of this measurement-based ARQ scheme. To evaluate the performance of the proposed ADSR-ARQ error control scheme under wireless multimedia environment, as well as to investigate the behavior of video streaming applications under various wireless network conditions, we build a LAN-based real-time wireless video streaming testbed. This testbed includes a wireless emulator, an MPEG-4 streaming server and a client. The wireless emulator implementation is based on the NS2 simulation platform operating in emulation mode to simulate the behavior of CDMA wireless networks, such as packet loss and delay, etc. A two-state Markov chain channel model is implemented in the wireless emulator to model the burst error behavior in wireless networks. In this thesis, end-to-end delay/jitter and throughput of MPEG-4 video transmission are measured under different error conditions over the testbed. The tradeoff between packet loss and delay is evaluated. From the theoretical analysis and experiments results, with an optimal design, our proposed innovative ADSR-ARQ error control scheme can effectively decrease packet losses and improve the channel utilization significantly under specified delay constraints. The ADSR-ARQ scheme outperforms the conventional SR-ARQ scheme with throughput improvement and delay decrease for transmitting MPEG-4 video stream over wireless networks. We also employ a pseudo Robust Header Compression (ROHC) function to demonstrate how the header compression scheme improves the wireless bandwidth efficiency. Furthermore, for future streaming media applications, this wireless emulator is an invaluable tool for the development and verification of new algorithms over wireless networks.

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