  We develop a scalable \textit{cell-level} analytical model for multi-cell
infrastructure IEEE 802.11 WLANs under a so-called Pairwise Binary Dependence
(PBD) condition. The PBD condition is a geometric property under which the
relative locations of the nodes inside a cell do not matter and the network is
free of \textit{hidden nodes}. For the cases of saturated nodes and
TCP-controlled long-file downloads, we provide accurate predictions of cell
throughputs. Similar to Bonald et al (Sigmetrics, 2008), we model a multi-cell
WLAN under short-file downloads as "a network of processor-sharing queues with
state-dependent service rates." Whereas the state-dependent service rates
proposed by Bonald et al are based only on the \textit{number} of contending
neighbors, we employ state-dependent service rates that incorporate the the
impact of the overall \textit{topology} of the network. We propose an
\textit{effective service rate approximation} technique and obtain good
approximations for the \textit{mean flow transfer delay} in each cell. For
TCP-controlled downloads where the APs transmit a large fraction of time, we
show that the throughputs predicted under the PBD condition are very good
approximations in two important scenarios where hidden nodes are indeed present
and the PBD condition does not strictly hold.
