  It is known that link throughputs of CSMA wireless networks can be computed
from a time-reversible Markov chain arising from an ideal CSMA network model
(ICN). In particular, this model yields general closed-form equations of link
throughputs. However, an idealized and important assumption made in ICN is that
the backoff countdown process is in "contiuous-time" and carrier sensing is
instantaneous. As a result, there is no collision in ICN. In practical CSMA
protocols such as IEEE 802.11, the stations count down in "mini-timeslot" and
the process is therefore a "discrete-time" process. In particular, two stations
may end their backoff process in the same mini-timeslot and then transmit
simultaneously, resulting in a packet collision. This paper is an attempt to
study how to compute link throughputs after taking such backoff collision
effects into account. We propose a generalized ideal CSMA network model (GICN)
to characterize the collision states as well as the interactions and dependency
among links in the network. We show that link throughputs and collision
probability can be computed from GICN. Simulation results validate GICN's
accuracy. Interestingly, we also find that the original ICN model yields fairly
accurate results despite the fact that collisions are not modeled.
