An efficient handoff management for terminal mobility support to H.323

Abstract

Handoff is one of the main issues in mobility. A simple solution to handoff transparency in a real-time application is to use mobile IP. However, mobile IP causes delay because of triangular routing. For handoff, existing approaches for H.323 mobility create a new H.323 connection by ad-hoc multipoint conferencing using Multipoint Controller (MC) functionality. However, the participating mobile terminal will experience call disruption due to message losses if the cells do not overlap closely enough to complete a handoff before the old connection is lost. In addition, this approach causes extra bandwidth consumption. If the correspondent terminal does not have MC, handoff cannot be supported. If the handoff occurs during call between mobile terminals, the MC should be modified to support mobility. In this thesis we propose an approach that allows, during handoff, a mobile terminal to simply close an existing logical channel for an old cell and open a logical channel for a new cell without an extra H.323 connection. During handoff, the proposed approach keeps the signaling connection using TCP over mobile IP. The proposed approach needs no modification to the existing H.323 message set and handles environment changes such as bandwidth after handoff. The delay can be reduced and the mobile terminal can handle handoff without MC functionality in the proposed approach. The proposed solution is implemented on mobile IP using a WaveLan local-area wireless network and Linux-based mobile nodes and mobile agents. Analysis is done in terms of total delay of the proposed and existing approach, and in terms of the distance between a home agent and a mobile node. The analysis shows that the proposed approach outperforms the existing approach in most of the cases.