dvanced technologies. There is a great amount of similarity between the requirements, features, and target performance of the two technologies. As shown in Figure 1-2 and considering the requirements in Table 1-2, the IMT-Advanced systems will provide significant improvements relative to IMT-2000 systems in terms of capacity and performance (user throughputs and access latencies), and variety of unicast and/or multicast based applications and services, as well as more spectrum utilization and deployment flexibility. 1.1.3 Convergence of Mobile Broadband Wireless Access Technologies As is evident from the previous section, the new mobile broadband wireless access systems are being developed based on similar system and service requirements using similar (if not the same at least conceptually) technologies. This would make one believe that a convergence in mobile broadband wireless technology is imminent in the next decade. While the previous attempts to harmonize the 3rd generation of mobile access technologies have failed due to incompatibility of core components, political and regional issues, competition in the industry, etc., the current trend in the prominent standardization organization combined with more pressure from the network operators due to frag- mentation of the market is compelling and/or persuading the major proponents of the existing tech- nologies to converge. The convergence of core network technologies has already been initiated and currently mobile WiMAX radio access technology can interwork with 3GPP core network and vice versa (see the interworking of trusted networks in 3GPP literature [23]). The inter-technology interworking func- tions, handover between heterogeneous technologies, as well as use of unified core network functions such as user authentication, authorization, and accounting for various radio access technologies, are examples of such a convergence trend. However, the convergence of radio interfaces has proved to be more difficult, due to the use of incompatible protocol structu