A Real-time Rate Control Mechanism For Multimedia Transmission Over 3G Wireless Networks

With the rapid development of the wireless networks, more and moreapplications based the on wireless multimedia networks are now emerged. To improvethe overall performance of these wireless networks, lots of researches have been made,and among which the rate control mechanism becomes the popular ones.In this thesis, we first investigate the performance of the 3G WCDMA wirelesschannel, and we find a special character, that sometimes a sudden link blockage/congestion happens and causes heavy throughput drops during a certain time in thegiven 3G channel. After getting the basic characteristics and information about theperformance, a novel transmission control scheme is proposed based on the Gilbertwireless error model by analysis of the characteristics which we notice of the wirelesschannel. The proposed scheme RBRC(Round Trip Time Based Rate Control)takesinto consideration of the link blockage/sudden congestion which last for a short timein the 3G networks, the packet loss rate, and congestion level to increase packetsuccessful delivery rate, reduce congestion and to improve the overall performance inthe 3G networks by a adjustable rate control mechanism.The performance of the proposed rate control mechanism is evaluated by usingNS-2 simulator over a wireless channel. We compare the RBRC mechanism withmechanisms of ZIGZAG and SPLD, from the results we got, they show that theproposed mechanism can detect the nature of the congestion effectively, and take theproper action to adjust the sending rate, improve the throughput and the networkutilization with a lower packet loss probability. The superiority of the RBRC is mainlybecause it can detect the network state better than others when the sudden linkblockage/congestion happens and can adjust the sending rate more reasonably andpromptly.