Performance Issues with Vertical Handovers - Experiences from GPRS Cellular and WLAN Hot-spots Integration

  • Authors:
  • Rajiv Chakravorty;Pablo Vidales;Kavitha Subramanian;Ian Pratt;Jon Crowcroft

  • Affiliations:
  • -;-;-;-;-

  • Venue:
  • PERCOM '04 Proceedings of the Second IEEE International Conference on Pervasive Computing and Communications (PerCom'04)
  • Year:
  • 2004

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Abstract

Interworking heterogeneous wireless access technologiesis an important step towards building the next generation,all-IP wireless access infrastructure. In this paper,we present an experimental study of inter-network mobilitybetween GPRS Cellular and 802.11b-based WLANhot-spots, and deeply analyse its impact on active transportTCP flows. Our experiments were conducted over aloosely-coupled, Mobile IPv6-based, GPRS-WLAN experimentaltestbed. Detailed analysis from packet traces ofinter-network (vertical) handovers reveals a number of performancebottlenecks. In particular, the disparity in theround trip time and bandwidth offered by GPRS and WLANnetworks, and presence of deep buffers in GPRS, can aggravateperformance during vertical handovers. This paper,therefore, summerizes practical experiences and challengesof providing transparent mobility in heterogeneousenvironments.Based on the observations, we propose a number ofnetwork-layer handover optimisation techniques, e.g. FastRouter Advertisements (RA), RA Caching, Binding Update(BU) simulcasting and layer-3 based soft handovers thatimprove performance during vertical handovers. The paperconcludes with our experiences of migrating TCP connections,thereby also improving application e.g. ftp, web performancein this environment.