Abstract
In distributed mobile computing systems, mobility is a vital feature but it also brings about many problems. For example, in the midst of a large file-transfer or mission-critical query processing, the user needs to take the mobile workstation (MW) out of the reach of a local area network (LAN). Due to limited coverage and the lack of interoperability between different networks, application roaming may become extremely difficult. When the MW moves from one network to another, it may have to disconnect from the original network. That means that the entire process may have to be restarted when the MW moves to the new network. This paper addresses issues of supporting seamless roaming of wireless LAN clients when they accidentally or deliberately leave the area covered by this LAN and still wish to continue running the application. When the MW leaves the wireless LAN, the connection is maintained and handed over to the wireless X.25 network. Such kind of seamless roaming is assisted by a proposed software module called a soft-handover agent, which resides on the MW. This virtual handover is implemented at the expense of slower processing and additional equipment. This approach is considered to be efficient for mission-critical applications.