ork Controller (RNC) functions have been included in the eNB to reduce the architectural complexity and to further reduce the latency across the network. The eNBs are interconnected with each other through X2 interface [31]. The eNBs are also connected by means of the S1 interface to the EPC, or more specifically to the MME through the S1-MME reference point and to the Serving Gateway (S-GW) via the S1-U interface [32]. The S1 interface supports a multipoint connection among MMEs/S-GWs and eNBs. The E-UTRAN overall architecture is described in references [31-33]. The following functions are typically performed by eNB [31]: Radio resource management that includes radio bearer control, radio admission control, connection management, dynamic allocation of resources to UEs in both uplink and downlink (i.e., scheduling); Header compression and encryption of user payloads; E-UTRAN FIGURE 2-9 E-UTRAN architecture [31] CHAPTER 2 WiMAX Network Architecture Selection of an MME at UE attachment when no routing to an MME can be determined from the information provided by the UE; Routing of U-plane data toward S-GW; Scheduling and transmission of paging messages (originated from the MME); Scheduling and transmission of broadcast information (originated from the MME); Measurement and reporting for support of mobility and scheduling. Figure 2-10 illustrates the functional decomposition of E-UTRAN and EPC [31]. The MME is the main control node for the 3GPP LTE access network. It is responsible for idle-mode UE tracking and paging procedure including re-transmissions. The MME functions include Non-Access Stratum (NAS) signaling and NAS signaling security, inter-core-network signaling for mobility between 3GPP access networks, idle mode UE accessibility (including control and execution of paging re-transmission), tracking area list management (for UE in idle and active mode), Packet Data Network (PDN) gateway and S-GW selection, MME selection for handovers with MME change, roaming, authentication of the users, and bearer managemen