Research On Switching And User Location Management Tactics In IP Multimedia Subsystem Network

3GPP(3rd Generation Partnership Project) first puts forward IP Multimedia Subsystem in packet domain of Release5's core network, in order to provide abundant mobile multimedia service, including voice, image and video etc. IMS uses SIP as the core multimedia call control protocol because it supports the mobility, but the multimedia terminal delay is a bit longer in the SIP switching process; In addition, IMS adopts the control mode of home domain providing service, so there are multiple signal interaction in register and location addressing between home domain and visit domain, it makes seriously affect to the user on their experiencing of the voice and video multimedia service, and limits the development of IMS, so reducing the multimedia delay , shortening the time in session establishment are urgent matter.This paper adopts the way of adding local and remote address in SOCKET, optimizes the bottom switching process across GGSN in IMS. It makes detailed contrastive analysis on various time and signal cost between the new switching link and the old one, makes emulation on error rate and transmission delay jitter by the dpt_error mode in OPNET, it justified that the new process can effectually shorten the switching delay. Based on the research of the old location management tactics, the paper introduces a new location caching algorithm, emulates the function and various cost between the new caching policies and the old one by OPNET. The simulation result justified than it can shorten the call establish time and saves the register cost, session establish cost and space cost etc. The tactics can play best when the calling and called are both in the visited domain, and the location information is true.Various of multimedia services emerge as the development of the 3rd Generation mobile communication, it has important significance in the mobile multimedia field to get the location fast and shorten the switching delay. The data forwarding process and caching strategy algorithm are based on the precondition that user call can obey the poisson distribution,and then it use concrete data to emulate various of the session cost by OPNET. The flowchart of switching, addressing steps of call establishment and discriminanting algorithm of cached information above are all described and marked in detail.