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3rd International Conference on Mobile Systems, Applications, and Services — Abstract
Pp. 107–120 of the Proceedings
Improving TCP Performance over Wireless Networks with Collaborative Multi-homed Mobile Hosts
Kyu-Han Kim and Kang G. Shin, University of Michigan
Abstract
Multi-homed mobile hosts situated in physical proximity may spontaneously
team up to run high-bandwidth applications by pooling their
low wireless wide-area network (WWAN) bandwidths together
for communication with a remote application server
and utilizing their high-bandwidth wireless local-area
network (WLAN) in ad-hoc mode for aggregation and distribution of
application contents among the participating mobile hosts.
In this paper, we first describe the need for such a
mobile collaborative community, or a community, in which
multi-homed mobile hosts exploit the diversity of
WWAN connections to improve a user-perceived
bandwidth and network utilization.
Then, we show that existing one-to-one communication protocols
like TCP suffer significant performance degradation due
to frequent packet reordering and heterogeneity
of WWAN links in the community.
To address the above TCP problem, we propose a proxy-based
inverse multiplexer, called PRISM, that enables
TCP to efficiently utilize the community members' WWAN
connections. PRISM runs at a 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 variety of adverse effects specific to
each WWAN link via intelligent ACK-control
mechanism. Finally, PRISM includes a sender-side
enhancement of congestion control, enabling TCP to
respond correctly to dynamically-changing network states.
We have evaluated the PRISM protocol using both
experimentation and ns-2-based simulation.
Our experimental evaluation has shown PRISM to improve
TCP's performance by up to 310% even
with two collaborative mobile hosts.
Our in-depth simulation study also shows that
PRISM delivers a near-optimal aggregated bandwidth
in the community formed by heterogeneous mobile hosts,
and improves network utilization significantly.
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