Tracking mobile units for dependable message delivery

A.L. Murphy, G.-C. Roman, G. Varghese
2002 IEEE Transactions on Software Engineering  
AbstractÐAs computing components get smaller and people become accustomed to having computational power at their disposal at any time, mobile computing is developing as an important research area. One of the fundamental problems in mobility is maintaining connectivity through message passing as the user moves through the network. An approach to this is to have a single home node constantly track the current location of the mobile unit and forward messages to this location. One problem with this
more » ... approach is that, during the update to the home agent after movement, messages are often dropped, especially in the case of frequent movement. In this paper, we present a new algorithm which uses a home agent, but maintains information regarding a subnet within which the mobile unit must be present. We also present a reliable message delivery algorithm which is superimposed on the region maintenance algorithm. Our strategy is based on ideas from diffusing computations as first proposed by Dijkstra and Scholten. Finally, we present a second algorithm which limits the size of the subnet by keeping only a path from the home node to the mobile unit. Index TermsÐMobile computing, message delivery, diffusing computations. ae INTRODUCTION M OBILE computing reflects a prevailing societal and technological trend toward ubiquitous access to computational and communication resources. Wireless technology and the decreasing size of computer components allow users to travel within the office building, from office to home, and around the country with the computer at their side. Both location-transparent and context-dependent services are desired. Decoupled computing is becoming the norm. Disconnection is no longer a network fault, but a common event intentionally caused by the user in order to conserve power or as a consequence of movement. Tethered connectivity is making way for opportunistic transient connections via radio or infrared transmitters. The focus of this paper is message delivery to mobile units. In a fixed network, message delivery relies on established routes through the network. Although faults can render parts of the network inoperative or even inaccessible, it is assumed that these faults are infrequent and the system is able to stabilize despite the changes. In mobility, the changing connectivity of the mobile components is not a fault, but rather a feature. As a mobile unit moves through the network, its accessibility point changes.
doi:10.1109/tse.2002.1000448 fatcat:nnuogskvpjdzdmgdg5kvl2tt4y