PRISM: Improving the performance of inverse-multiplexed TCP in wireless networks
Multihomed mobile hosts in physical proximity may spontaneously team up to form a community and run high- bandwidth applications by pooling their low wireless wide- area network ( WWAN) bandwidths together for communication with a remote application server. Utilizing their high- bandwidth wireless local- area network ( WLAN), the thus- teamed mobile hosts can aggregate and distribute the application content among themselves. This paper first justifies the need for such a mobile collaborative community (MC2), or a community, to improve user- perceived network bandwidth and utilization. Then, existing one- to- one communication protocols like TCP are shown to suffer significant performance degradation due to frequent out- of- order packet deliveries. To address this TCP problem, we propose a proxy- based inverse multiplexer, called PRISM, that enables TCP to efficiently utilize the community members' WWAN connections while avoiding the performance degradation. PRISM runs at the proxy's network layer as a routing component and stripes each TCP flow over multiple WWAN links by exploiting the transport- layer feedback information. Moreover, it masks a variety of adverse effects specific to each WWAN link via an intelligent ACK- control mechanism. Finally, PRISM enables TCP to respond correctly to dynamically changing network states through a sender- side enhancement of congestion control. PRISM has been evaluated with experimentation on a testbed as well as in ns- 2- based simulation. Our experimental evaluation has shown PRISM to improve TCP's performance by up to 310 percent, even with two collaborative mobile hosts. Our in- depth simulation study has also shown that PRISM delivers a near- optimal aggregated bandwidth in the community and improves network utilization significantly.
tcp multihoming mobile collaborative community bandwidth aggregation out-of-order packet delivery