  This paper is focused on the problem of optimizing the aggregate throughput
of the Distributed Coordination Function (DCF) employing the basic access
mechanism at the data link layer of IEEE 802.11 protocols. In order to broaden
the applicability of the proposed analysis, we consider general operating
conditions accounting for both non-saturated and saturated traffic in the
presence of transmission channel errors, as exemplified by the packet error
rate $P_e$.
  The main clue of this work stems from the relation that links the aggregate
throughput of the network to the packet rate $\lambda$ of the contending
stations. In particular, we show that the aggregate throughput $S(\lambda)$
presents two clearly distinct operating regions that depend on the actual value
of the packet rate $\lambda$ with respect to a critical value $\lambda_c$,
theoretically derived in this work.
  The behavior of $S(\lambda)$ paves the way to a cross-layer optimization
algorithm, which proved to be effective for maximizing the aggregate throughput
in a variety of network operating conditions. A nice consequence of the
proposed optimization framework relies on the fact that the aggregate
throughput can be predicted quite accurately with a simple, yet effective,
closed-form expression, which is also derived in the article.
  Finally, theoretical and simulation results are presented throughout the work
in order to unveil, as well as verify, the key ideas.
