t, and proliferation of broadband wireless systems in the past decade. A number of broadband wireless access standards for fixed, nomadic, and mobile systems have been developed by these standardization groups and deployed by a large number of operators across the globe [9,13,14]. 1.1.1 The 4th Generation of Mobile Broadband Wireless Access Technologies International Mobile Telecommunications-Advanced (IMT-Advanced) or alternatively 4th Genera- tion (4G) cellular systems are mobile systems that extend and improve upon the capabilities of the IMT-2000 family of standards. Such systems are expected to provide users with access to a variety of advanced IP-based services and applications, supported by mobile and fixed broadband networks, which are predominantly packet-based. The IMT-Advanced systems can support a wide range of data rates, with different quality of service requirements, proportional to user mobility conditions in multi-user environments. The key features of IMT-Advanced systems can be summarized as follows [11,15]: Enhanced cell and peak spectral efficiencies, and cell-edge user throughput to support advanced services and applications; Lower airlink access and signaling latencies to support delay sensitive applications; "http://www.3gpp.org "http://www.3gpp2.org "http://standards.ieee.org 1.1 Mobile broadband wireless access technologies High Mobility New Mobile Access (120-500 km/h) IMT-Advanced Enhanced Systems IMT 2000 Systems IMT 2000 Systems Low Mobility/ iNewNomadic/Local Nomadic Wireless Access (0-30 km/h) Layer 2 Data Rate (Throughput at MAC Layer) Mbps FIGURE 1-2 Illustration of the capabilities and evolution of IMT-2000 systems [10] Support of higher user mobility while maintaining session connectivity; Efficient utilization of spectrum; Inter-technology interoperability, allowing worldwide roaming capability; Enhanced air-interface-agnostic applications and services; Lower system complexity and implementation cost; Convergence of fixed and mobile networks; Capability of interworking with ot