n Tracking Area while no NAS (Non Access Stratum) signaling connection exists between UE and network. Normally, the ECM and EMM states are independent of each other; however, some mechanisms do require interaction of these four states. For example, transition from EMM-DREGISTERED to EMM- REGISTERED the UE has to be in the ECM-CONNECTED state. Figure 11.4 shows transitions from one state to other and respective functions. The details of EMM and ECM can be found in [8]. 11.4.2 Mobility Management in WiMAX The end-to-end WiMAX Network Architecture defines the capability to support mobility and handovers. ASN anchored mobility and CSN anchored mobility are the two mobility management scenarios that E2E Network Architecture and Mobility Management Detach, Attach Reject, TAU reject, Detach, E-UTRAN interface switched off due to Non-3GPP handover, Attach Reject, All bearers deactivated TAU reject, All bearers deactivated EMM-DEREGISTERED EMM-REGISTERED EMM-DEREGISTERED EMM-REGISTERED Attach accept Attach accept TAU accept for a UE selecting E-UTRAN from GERAN/UTRAN A) EMM state model in UE B) EMM state model in MME RRC connection S1 connection released released ECM-IDLE ECM-CONNECTED ECM-IDLE ECM-CONNECTED RRC connection S1 connection established established C) ECM state model in UE D) ECM state model in MME Figure 11.4 EPS mobility and connection management state transitions and functions. Reproduced with permission from 2009 3GPP [8] are supported in WiMAX. The intra ASN-Gateway and inter ASN-Gateway mobility scenarios are part of ASN anchored mobility where users' handoffs to base stations may or may not belong to the same ASN-Gateway. The CSN anchored mobility refers to a set of procedures for changing the traffic anchor point for the MS from one anchor point to another one in the ASN without changing the CSN anchor. CSN anchored mobility is independent from the 802.16e handover [4]. The mobile WIMAX architecture needs to accommodate IPv4 or IPv6 based mobility management, terminals with multiple IP addresses and si