 WiMAX Core 3GPP2 HRPD RAN (CSN) A10/A11 AN/PCF LMA/HA A10/A11 MS/AT AN*/PCF Figure 11.11 WiMAX to HRPD handoff. Reproduced with permission from C 2009 3GPP2 [13] Next Generation Mobile Communications Ecosystem IP Services WiMAX ASN WiMAX Core 3GPP2 HRPD RAN (CSN) A10/A11 AN/PCF LMA/HA A10/A11 AN/PCF WiMAX MS/AT Figure 11.12 HRPD to WiMAX handoff. Reproduced with permission from © 2009 3GPP2 [13] 11.8.1 Authentication and Security Each wireless access network has different security mechanisms to mitigate security threats. The compo- sition of several security architectures may produce an insecure outcome. This inefficiency occurs due to possibly conflicting security mechanisms and the processes that are used to apply a specific security pro- cedure. At the same time any delay in authentication will impact the performance of high speed sessions. The long authentication delays during handovers can be perceived as disruption of services by the user. In [14] authors have proposed that if security context5 can be transferred between the EPS and WiMAX, it will not only improve the security exchange mechanism, but also expedite the authentication procedure between the two radio networks. This might not be feasible when there is a handoff need between EV-DO and EPS or between EV-DO and WiMAX. The key reason behind this is the absence of authentication and key exchange method called EAP-AKA (Extensible Authentication Protocol - Authentication and Key Agreement) from EV-DO which is present in both EPS and WiMAX. 11.8.2 End-to-End QoS A key prerequisite in offering session mobility is to offer consistent Quality of Service throughout the session transfer process from one radio network to another. Since each radio technology has defined its unique QoS classes it is necessary to have a mapping or look up table that can map these classes. The mapping between various radio technologies has been defined in the respective standards. Secondly, resource reservation and the type and performance of packet schedulers are also some of 