lity across different access technologies. This would be quite attractive for mobile operators operating radio access networks of different types, such as mobile WiMAX or 3GPP Long Term Evolution (LTE), etc. While CMIP ensures seamless mobility for the IP session, it introduces some disadvantages such as signaling overhead over the air interface and additional MS complexity to support the client IP mobility protocols. The Proxy Mobile IP (PMIP) defined by IETF, which is a network-based mobility management scheme, was introduced to eliminate signaling overhead and to reduce complexity/cost, as well as eliminating the requirement for a network ASN-GW V-CSN H-CSN IEEE 802.16 IEEE 802.16 ASN Control ASN Control CSN Control CSN Control Control Control Data Link Layer Data Link Layer Data Link Layer Data Link Layer Physical Layer Physical Layer Physical Layer Physical Layer IP CS IP CS Data Link Layer Data Link Layer Data Link Layer Data Link Layer Physical Layer Physical Layer Data Link Layer Data Link Layer Physical Layer Physical Layer Physical Layer FIGURE 2-5 The protocol stack for the IP convergence sub-layer with routed ASN [14] CHAPTER 2 WiMAX Network Architecture interface to change IP address when the mobile node changes to a new router [28]. The WiMAX network architecture supports both the CMIP and PMIP mobility schemes. 2.5 RADIO RESOURCE MANAGEMENT (RRM) Efficient utilization of radio resources within an access network is performed by the radio resource management entity. The mobile WiMAX RRM is based on a generic architecture. The RRM defines mechanisms and procedures to share radio resource related information between BS and ASN-GW. The RRM procedures allow different BSs to communicate with each other or with a centralized RRM entity residing in the same or a different ASN to exchange information related to measurement and management of radio resources. Each BS performs radio resource measurement locally based on a distributed RRM mechanism. It is also possible to deploy RRM in an ASN using base stations