re, multiple access schemes, and baseband processing. Figure 1-4 illustrates a transport and service layered model that is agnostic of the radio access network while ensuring seamless mobility and service/session continuity. The converged system shown in Figure 1-4 comprises an all-IP common core network and application layer that commu- nicates to user terminals through a set of heterogeneous radio access networks. Some variants of this operation model are currently deployed and being used by some network operators. However, the cost and complexity of multi-radio implementations, the coexistence of multiple radio access technologies collocated on the user terminal, and inter-system interference issues adversely impact the long-term viability of this approach. The operators now desire convergence of radio access networks to ensure CHAPTER 1 Introduction to Mobile Broadband Wireless Access Services and Content (e.g., Voice, Data, Video, Internet, Text, E-mail, Mobile-TV, etc.) Common Core All-IP Core Network Network (e.g., 3GPP EPC, 3GPP GPRS Core, mobile WiMAX Core Network) Heterogeneous 3GPP LTE mobile WiMAX 3GPP2 cdma2000 Wi-Fi Radio Access (LTE-Advanced) (IEEE 802.16m) Network (IEEE 802.11) FIGURE 1-4 Example of a RAN-agnostic transport and service layered model lower cost of deployment and simplicity of future upgrades, as well as global roaming and service continuity across different operators' networks. While the market fragmentation may help lower the royalties and foster innovative competing solutions, it does increase the operating cost and system complexity. The use of common functional elements and protocols in the new generation of cellular systems is an indication that these systems are moving toward ultimate convergence, resulting in a unified and scalable radio access technology that can be deployed in various deployment scenarios (e.g., indoor as a femto- cell, outdoor as a micro- or macro-cell, and in high-speed rural environments) by appropriately reconfiguring the system parameters to match the