Handovers in micro mobility protocols for the WLANs

Abstract

The semi-soft handoff scheme for cellular IP is optimized for networks where the mobile host is able to listen/transmit to two or more base stations simultaneously for a short duration - the time that the mobile host spends in the overlap area - as in the case of a waveLAN or code division multiple access (CDMA) network. This scheme improves the network efficiency of handoff in terms of packet loss but with more delay. However not all wireless technologies have simultaneous connection capability as does a time division multiple access (TDMA) network. A new scheme introduced in a cellular IP draft has been implemented in a network simulator and is discussed in this paper. Indirect handoff has been implemented for the networks where the mobile host is able to listen/transmit to only one base station. It is shown in this paper that for the wireless technologies where a semi-soft scheme cannot be used, an indirect handoff scheme is a more efficient alternative to hard handoff in cellular IP micro mobility protocol. The behaviour of TCP and UDP at handoff is then discussed. Finally, the handoff performance for cellular IP, Hawaii and HMIP is compared.