Study And Enhancement On Buffer Management For Smooth Handover In Mobile IPv6

Mobile IP technology is the main component of the next generation mobile internet and gains lots of researchers' attention. However packet losses, delay and out-of-sequence transmission during handover are interpreted as a sign of network congestion, which causes TCP to take some unnecessary congestion avoiding measures. Consequently TCP achieves poor performance. For improving TCP performance in mobile environment, Smooth Handover with Buffer Management has been proposed to provide seamless handover, which hopes to shield the influence of handover to TCP. However in our simulation, even if Smooth Handover with Buffer Management in MIPv6 is implemented, TCP can not always achieve better performance due to packets forwarding burst. At the same time, due to insensitiveness with the movement of mobile node (MN), Buffer Management has a serious buffer waste problem.To the question of the packets forwarding burst, an ideal buffer management should have the capability to control the buffered packets to be forwarded smoothly and promptly. From the analysis above, an enhanced buffer forwarding control scheme with probing technology is proposed. In this scheme, a packet-pair probing technology is adopted to estimate the available bandwidth of the new path, which will be used to control the buffered packets forwarding. The simulation results demonstrate that Smooth Handover with this scheme can achieve better TCP performance than that without it.To the question of the buffer waste, a self-adaptive resource management algorism based on handover fuzzy forecast is proposed. This algorism is simple, adaptive and composed of two key technologies. The one is an enhanced buffer control mechanism based on handover fuzzy forecast, which is used to control buffer application and buffer release. Another is a self-adaptive signal threshold algorism, which is used to adjust signal threshold in the enhanced buffer control mechanism dynamically. The simulation results and analysis demonstrate that the self-adaptive resource management algorism can increase buffer utilization without degrading the upper layer performance.