20-06-2010, 01:11 AM
Presented By:
Bret Hull, Kyle Jamieson, Hari Balakrishnan
MIT Computer Science and Artiï¬Âcial Intelligence Laboratory
The Stata Center, 32 Vassar St., Cambridge, MA 02139
ABSTRACT
Network congestion occurs when oï¬ered traffic load exceeds available capacity at any point in a network. In wireless sensor networks, congestion causes overall channel quality to degrade and loss rates to rise, leads to buï¬er drops and increased delays (as in wired networks), and tends to be grossly unfair toward nodes whose data has to traverse a larger number of radio hops. Congestion control in wired networks is usually done us- ing end-to-end and network-layer mechanisms acting in con- cert. However, this approach does not solve the problem in wireless networks because concurrent radio transmissions on diï¬erent links interact with and aï¬ect each other, and be- cause radio channel quality shows high variability over mul- tiple time-scales. We examine three techniques that span diï¬erent layers of the traditional protocol stack: hop-by-hop flow control, rate limiting source traffic when transit traffic is present, and a prioritized medium access control (MAC) protocol. We implement these techniques and present ex- perimental results from a 55-node in-building wireless sen- sor network. We demonstrate that the combination of these techniques, Fusion, can improve network efficiency by a fac- tor of three under realistic workloads.
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http://citeseerx.ist.psu.edu/viewdoc/dow...1&type=pdf
