Current Cisco Aironet products do not support per-client bandwidth limiting or allocation.
You can select a total bandwidth or associated data rate of 11, 5.5, 2, or 1Mbps. This is a cumulative total, not a per-client datarate.
Access points treat all clients equally in terms of bandwidth, providing "best available" throughput. Much like on an ethernet, the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) scheme allows each client a time slice for the use of the total bandwidth available on the radio link.