In the traditional mobile communication networks, the bandwidth of wireless links is too small and the bandwidth difference between wireless links and wireline links is too large. This leads to limiting the application of mobile communication networks to transmit multimedia data and other high-bit rate services, and the problem of lacking bandwidth often occurs to wireless links. But the new generation mobile communication networks, called the third generation mobile communication systems (3G systems), will change this condition. Because the 3G systems will quickly enhance the transmission rate of the wireless links (up to 2Mbps) and provide better quality of transmission, the transmission of multimedia data and other high-bit rate services in the mobile communication networks can be achieved. The 3G systems can support many new services that are never supported before, and these new services always need support the point-to-multipoint transmission. In this thesis, we will discuss the problems of supporting these new services, and then we propose new multimedia multicasting architecture to overcome these problems.