Monday, July 12, 2010

Handoff Objective and Mobility Management | Protocols for Connection Handoff

As the quality of an established radio link between a Subscriber Station (SS) (or terminal) and its BS deteriorates due to mobility, the objective of handing off the connection to a neighboring BS is to maintain the Internet Protocol (IP) connectivity between the SS and the corresponding host. A major goal is to minimize packet loss and delay induced by the handoff process. As the 802.16-2004 standard defines only the PHY and MAC layers, without loss of generality, suppose that the network under study employs the Hierarchical Mobile IP (HMIP) algorithm for micromobility management. Using the common terminology for mobile networks, Figure 1 shows the architecture of the HMIP for the 802.16 network under consideration. Specifically, one router is designated the Primary Foreign Agent (PFA) and serves as the "anchor point" for each SS (or connection). That is, data from and to a given SS always goes through the corresponding PFA. In addition, the PFA also keeps track of the operational parameters for the 802.16-2004 connections associated with the SS. As shown in the figure, the communication path consists of multiple IP tunnels and packets are forwarded by tunneling.

Figure 1: Hierarchical mobile Internet Protocol for 802.16-2004 network. 
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