We propose a scheduling scheme for IEEE 802.16e Broadband Wireless Access (BWA) systems working in TDD mode. The scheduler exploits deficit priority queue scheduling with adaptive deficit calculation to support variable rate realtime traffic in both uplink and downlink directions. Our scheduling scheme makes use of a Minimum Tolerable Traffic Rate, a QoS parameter defined by the standard. The simulation results show that the proposed scheduler can properly serve realtime flows and achieve low delay even in a very high traffic load condition.