Undesirable service differentiation in future WLANs

The IEEE 802.11 distributed coordination function (DCF) offers only best-effort service. The enhanced DCF (EDCF) scheme supports quality of service by establishing a probabilistic priority mechanism to access the shared wireless medium. EDCF defines four access categories, namely, AC.VO, AC-VI, AC-BE and AC-BK to support voice, video, best-effort and background traffic, respectively. Since DCF and AC_BE of EDCF offer best-effort service, it is desirable that applications demanding such a service, experience comparable delay and, throughput whether they are run on a DCF-compliant or an EDCF-compliant wireless station. In this paper, we show through simulation experiments that DCF-and EDCF-compliant stations do not provide comparable support to best-effort applications while operating together. This is due to different parameter settings in DCF and EDCF which leads to an undesirable service differentiation.