Efficient hierarchical SIP mobility management for WiMAX networks

By adopting Session Initiation Protocol (SIP) in WiMAX networks, when the mobile node (MN) moves to a foreign network, the MN sends a re-INVITE message to the corresponding node (CN) to re-establish the connection. This re-connection time is the most costly factor for a handoff. To effectively reduce the re-connection latency, a hierarchical SIP (HSIP) mobility management incorporated with MAC layer operations is proposed. As proposed in the HSIP architecture, several Base Stations (BSs) are collectively managed by an HSIP server to form an administration domain. When an MN roams within a domain, which is the most common mobility case, a re-INVITE message is not necessary, hence a significant traffic reduction can result. To demonstrate the applicability of the proposed HSIP mobility mechanism, an evaluation using the NS2 simulator was performed. Handoff delay and signaling overhead are investigated in both single-handoff and multiple-handoff occurrences. When the ratio of intra-domain to inter-domain handoffs is increased from 1 to 14, the proposed HSIP mobility mechanism can improve up to 13% in average handoff delay and 35% in average signaling overhead as compared with traditional SIP mobility management.