  This paper proposes a new protocol called Optimal DCF (O-DCF). Inspired by a
sequence of analytic results, O-DCF modifies the rule of adapting CSMA
parameters, such as backoff time and transmission length, based on a function
of the demand-supply differential of link capacity captured by the local queue
length. Unlike clean-slate design, O-DCF is fully compatible with 802.11
hardware, so that it can be easily implemented only with a simple device driver
update. Through extensive simulations and real experiments with a 16-node
wireless network testbed, we evaluate the performance of O-DCF and show that it
achieves near-optimality, and outperforms other competitive ones, such as
802.11 DCF, optimal CSMA, and DiffQ in a wide range of scenarios.
