Universal Seamless Handoff Architecture in Wireless Overlay Networks

In view of the proliferation of mobile applications, a universal seamless handoff solution across wireless domains is becoming increasingly important. While wired connections usually provide high speed, reliable access to the Internet, wireless networking technologies enable users to access customized Internet services even when they are moving. A seamless handoff solution with both low latency and low packet loss is mandatory for mobile users who wish to receive continuous, uninterrupted Internet service while frequently switching from one network connection to another. Additionally, the handoff solution should be network-layer-transparent and infrastructure-modification-free so that existing Internet server and client applications can painlessly survive the rapid pace of wireless technology evolution. Seamless handoff aims to provide continuous connection for an end-to-end data transmission in the face of any link outage or handoff event. Low latency and low packet loss are the two most critical design issues. Low latency requires that the switch to the new path be completed almost instantaneously; service interruption should be minimized to provide the illusion of continuous connectivity. In the event of actual connection failure, the architecture should attempt to reconnect as soon as the service becomes available, and the packet loss due to the connection switch should also be minimized. Seamless handoff can happen either horizontally or vertically [1]. A horizontal handoff is a handoff between two network access points that use the same network technology. For example, when a mobile device moves in and out of various 802.11b [2] network domains, the handoff activities would be considered as a horizontal handoff, since the connection is disrupted solely by device mobility. A vertical handoff is a handoff between two network access points using different network connection technologies. For example, when a mobile device moves out an 802.11b network into a GPRS [3] network, the handoff would be considered a vertical handoff. The challenge in vertical handoff is to maintain the application session alive while the physical connection interface is changed. Seamless handoff has been studied extensively [4] [5] [6] [7]. The solutions can be classified into two categories: mobile IP solutions and mobile IP-less solutions. The mobile IP solutions are typically based on IPv6 [8] or Mobile IPv4 [9] standards, requiring the deployment of different agents on the Internet for relaying and/or redirecting the data to the moving mobile host (MH). Most Mobile IP-less solutions implement a new session layer above the transport layer to make the application …