Praise for Fundamentals of WiMAX

10.8 Mobility Management 353• Comply with the security and trust architecture of IEEE 802.16 and IETF EAP RFCs duringmobility events• Supporting macro diversity handover (MOHO) as well as fast base station switching(FBSS) 7• Minimize the number of round-trips of signaling to execute handover• Keep handover control and data path control separate• Support multiple deployment scenarios and be agnostic to ASN decomposition• Support both IPv4- and IPv6-based mobility management and accommodate mobiles withmultiple IP addresses and simultaneous IPv4 and IPv6 connections• Maintain the possibility of vertical or intertechnology handovers and roaming betweenNSPs• Allow a single NAP to serve multiple MSs using different private and public IP domainsowned by different NSPs• Support both static and dynamic home address configuration• Allow for policy-based and dynamic assignment of home agents to facilitate such featuresas route optimization and load balancingThe WiMAX network supports two types of mobility: (1) ASN-anchored mobility and (2)CSN-anchored mobility. ASN-anchored mobility is also referred to as intra-ASN mobility, ormicromobility. In this case, the MS moves between two data paths while maintaining the sameanchor foreign agent at the northbound edge of the ASN network. The handover in this case happensacross the R8 and/or R6 reference points. ASN-anchored handover typically involvesmigration of R6, with R8 used for transferring undelivered packets after handover. It is also possibleto keep the layer 3 connection to the same BS (anchor BS) through the handover and havedata traverse from the anchor BS to the serving BS throughout the session. CSN-anchoredmobility is also referred to as inter-ASN mobility, or macromobility. In this case, the MSchanges to a new anchor FA—this is called FA migration—and the new FA and CSN exchangesignaling messages to establish data-forwarding paths. The handover in this case happens acrossthe R3 reference point, with tunneling over R4 to transfer undelivered packets. Figure 10.10illustrates the various possible handover scenarios supported in WiMAX.Mobility management is typically triggered when the MS moves across base stations basedon radio conditions. It may also be triggered when an MS wakes up from idle mode at a differentASN or when the network decides to transfer R3 end points for an MS from the serving FA to anew FA for resource optimization.In many cases, both ASN- and CSN-anchored mobility may be triggered. When this happens,it is simpler and preferable to initiate the CSN-anchored mobility after successfully completingthe ASN-anchored mobility.7. Note that the initial WiMAX system profiles do not support MDH and FBSS.