IP Mobility and the CDMA Radio Access Network: Applicability Statement for Soft Handoff

Recently, there have been a variety of proposals submitted to the Mobile IP Working Group and to other IETF working groups for IP mobility solutions that seek to enhance or replace mobile IP. These proposals, often characterized as micromobility or fast handoff, are addressed primarily at the perceived need of multimedia sessions such as video or voice over IP for faster handoff between radio base stations, and are primarily directed at real time multimedia traffic in 3rd generation cellular access networks. In this paper, we discuss the design of CDMA radio access networks (RANs) and the applicability of IP mobility to soft handoff in a CDMA RAN. We attempt to show that given current IP routing algorithms and the constraints on a CDMA RAN, IP mobility solutions have little, if any, role to play in handoff within the RAN. In contrast, an IP mobility solution is likely to play a big role in fast handoff between RANs, also called hard handoff. While future developments in IP networking may change this situation, IP mobility in CDMA networks currently seems to apply only when the mobile node roams between disconnected RANs rather than between base stations within a RAN or between connected RANs.