Research And Implementation Of Self-tune PI Rate Controller Under The Environment Of Wireless Network

Along with rapid development of network techniques and mobile communication techniques, the demand for high wireless data service performance is increasing.The most popular network protocol today is TCP, which is empirical, sender- based, point-to-point and bursty, and assumes that packet losses mean congestion, and that is what makes it work in many contexts. However, in a wireless network, packet losses can be caused not only by network congestion but also by unreliable error- prone wireless links, so TCP is not suitable to wireless network to some extents.Self-tune Proportional-Integral Rate Control Protocol (PIRCP) is an Explicit Congestion Notification method which comprises transmitting, at a source node, data packets to a destination node, via intermediate nodes; with an advertised speed determining by using the instantaneous deviation of the queue length from its target occupancy at the intermediate nodes, if an incipient congestion is encountered, i.e.the intantanous queue length is significantly long than it's hoped, calculating the advertised source transmission rate and asking the source nodes to slow down their sending rate to the very value, and vise versa, alternatively, if the packet loss happens, no matter due to what reasons, retransmitting the lost packets to the destination node.In this paper, PIRCP is implemented and the results of experimental study of this protocol under the environment of wireless network is presented. We first imple- mented PIRCP in the Linux kernel by using kernel module to avoid re-writting codes in the kernel, which would bring us unimaginable large workload, and after solving various system issues, such as data structure of PIRCP, the way to get data packets, mutual exclusion, the using of timer, memery allocation and so on, the PIRCP implimentamtion was running on the test bed we built to validate theoretical deductions and previously reported simulation results, drawing a conclution that PIRCP can be superior to TCP New-Reno, the default network protocol in Linux kernel 2.6.x, under the environment with high loss rate and very unstable systematic parameter at the aspects of queue length in the buffer of router, throughput, fairness, robustness, stability and convergency.Still, more research is needed before we can advocate a wide scale adoption.