NSDI '08 – Abstract
Pp. 59–72 of the Proceedings
Harnessing Exposed Terminals in Wireless Networks
Mythili Vutukuru, Kyle Jamieson, and Hari Balakrishnan, MIT Computer Science and Artificial Intelligence Laboratory
Abstract
This paper presents the design, implementation, and experimental
evaluation of CMAP (Conflict Maps), a system that increases the
number of successful concurrent transmissions in a wireless network,
achieving higher aggregate throughput compared to networks that use
carrier sense multiple access (CSMA).
CMAP correctly identifies and exploits exposed terminals in
which two senders are within range of one another, but each intended
receiver is far enough from the other sender that the two
transmissions can succeed even if done concurrently. CMAP includes
a reactive channel access scheme in which nodes transmit
concurrently (even if there's the possibility of a collision), then
observe the loss probability to determine whether they are better
off transmitting concurrently or not. Experimental results from a
50-node 802.11a testbed show that CMAP improves throughput by
2× over CSMA with exposed terminals, while converging to the
performance of CSMA when the senders and receivers are all close to
each other. CMAP also improves throughput by up to 47% over CSMA
in realistic access point-based networks by exploiting concurrent
transmission opportunities.
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