Traditional wireless networking solutions are almost all unsuitable for multimedia applications whose QoS requirements may differ from each other diversely. Main inspiration of WATM, promising ideal transmission of different traffics such as voice, data and video together over wireless medium, is to implement high bit rate and QoS guaranteed data transfer, which is already well realized by ATM technology over wired infrastructure. An effective MAC protocol must be employed to provide multimedia applications with QoS guaranteed data transfer over the shared wireless medium that naturally is error-prone and has low bandwidth capacity. In this paper, we propose a new MAC protocol with a QoS guarantee based scheduling algorithm for WATM networks. It fairly maintains QoS requirements of all real-time wireless multimedia applications. Computer modeling and simulation of a WATM network with the proposed approach to provide CBR, VBR, ABR and UBR ATM services are also realized using a commercially available tool named OPNET Modeler. Preliminary simulation results obtained are presented, including comparisons with those of a WATM counterpart employing a well-known MAC protocol.