In this paper, an adaptive scalable multiuser-OFDM system was proposed for multimedia transmission over fading channels. The proposed adaptive algorithm can adapt according to the channel status information of each user's channel status. This algorithm dynamically changes according to the user's channel changes; this can keep fixed QoS at the physical layer. Another predefined QoS for different sessions and services to be provided for different users. This QoS can be guaranteed by multimedia scalability. Scalability can adapt to the service requirements, in terms of transmission data rate and bandwidth. As a result, a robust multimedia transmission scheme is achieved by providing fix QoS for the end users in multiuser environment, by fixing QoS in the physical layer by the bit and power adaptation technique and also in service layer by scalability techniques. Furthermore, space diversity techniques are used to decrease the effect of frequency selective multipath effects in broadband wireless channels.