The IEEE 802.11 working group is currently working on the support of quality of service (QoS) in a new standard called IEEE 802.11e which introduces the so-called hybrid coordination function (HCF). A simple admission control unit has already been developed as a reference for HCF controlled channel access (HCCA) in a recent TGe draft . However, this reference scheme is inefficient because it is implemented based on the minimum physical rate from which the mobile stations' actual physical rates deviate greatly at most of the time. In this paper, we propose a physical rate based admission control scheme (PRBAC) which enhances the reference scheme by taking account of both the wireless channel characteristics and the stations' mobility. Numerical analysis and simulation results show the significant improvement of the proposed admission control scheme.