Department of Computer Science and Technology

Technical reports

Application support for mobile computing

Steven Leslie Pope

February 1997, 145 pages

This technical report is based on a dissertation submitted October 1996 by the author for the degree of Doctor of Philosophy to the University of Cambridge, Jesus College.



In recent years small, completely portable computers have become available on the marketplace. There is demand for such computers, termed walkstations, to access network services while retaining their mobility, and to operate effectively in a range of conditions. Future office environments are expected to support wireless networks with bandwidths which are several orders of magnitude greater than are available outdoors. In such environments there will be powerful compute servers available for a walkstation’s use.

This dissertation describes a novel architecture called Notus and its support for applications operating in a mobile environment. The concept of the traded handoff is introduced where applications are able to participate in the handoff process, rebuilding connections to the most appropriate service. This is expected to benefit walkstations which roam over large distances, where connections to servers would otherwise be strained, and also between heterogeneous networks where cooperation between the networks in performing a handoff might be problematic. It is also proposed in this dissertation that applications could benefit from the ability to migrate onto compute servers as a walkstation moves into the office environment. This enables both the walkstation to conserve its own resources, and applications to improve the service provided to the end user. Finally by interleaving a traded handoff with the migration process it is possible for a migrating application to easily rebuild its connections as it moves to a new host.

The Notus architecture has been implemented, including a traded handoff service and a new application migration service. The new application migration service was designed since existing application migration services are unsuited to mobile environments and it enables applications to migrate between heterogeneous hosts with little disruption. Applications which use the service are written in a standard compiled langauge, and normal running applications suffer little overhead. A number of existing applications which are representative of a walkstation’s interactive desk-top environment have been adapted to use the Notus architecture, and are evaluated.

In summary, this work describes how mobility awareness and the support from appropriate tools, can enable walkstation applications to better adapt to a changing mobile environment, particularly when the walkstation is carried between different network types or over great distances.

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BibTeX record

  author =	 {Pope, Steven Leslie},
  title = 	 {{Application support for mobile computing}},
  year = 	 1997,
  month = 	 feb,
  url = 	 {},
  institution =  {University of Cambridge, Computer Laboratory},
  doi = 	 {10.48456/tr-415},
  number = 	 {UCAM-CL-TR-415}