  We obtain an association policy for STAs in an IEEE 802.11 WLAN by taking
into account explicitly two aspects of practical importance: (a) TCP-controlled
short file downloads interspersed with read times (motivated by web browsing),
and (b) different STAs associated with an AP at possibly different rates
(depending on distance from the AP). Our approach is based on two steps. First,
we consider an analytical model to obtain the aggregate AP throughput for long
TCP-controlled file downloads when STAs are associated at k different rates r1,
r2, : : :, rk; this extends earlier work in the literature. Second, we present
a 2-node closed queueing network model to approximate the expected
average-sized file download time for a user who shares the AP with other users
associated at a multiplicity of rates. These analytical results motivate the
proposed association policy, called the Estimated Delay based Association (EDA)
policy: Associate with the AP at which the expected file download time is the
least. Simulations indicate that for a web-browsing type traffic scenario, EDA
outperforms other policies that have been proposed earlier; the extent of
improvement ranges from 12.8% to 46.4% for a 9-AP network. To the best of our
knowledge, this is the first work that proposes an association policy tailored
specifically for web browsing. Apart from this, our analytical results could be
of independent interest
