The Distributed Coordination Function (DCF) is the mandatory, and most
widely used, access scheme in the IEEE 802.11 standard. Efficiency in
utilizing wireless medium and fairness in respect to wireless stations
and the traffic generated by them, have always been considered two of
DCF's main features. In this paper, we examine the fairness of DCF in
allocation of bandwidth to heterogeneous multimedia traffic,
especially for overloaded systems.  Results show that applications
with certain traffic patterns, and queuing effects on heavily loaded
stations, could disrupt fair allocation of bandwidth among different
multimedia streams sharing the same station, as well as among
stations. Among many others, one serious consequence of this can be
significant asymmetry in quality of service between downlink and
uplink directions in bidirectional multimedia sessions.