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Drive-thru InternetThe Drive-thru Internet project investigates the usability of IEEE 802.11 technology for providing network access to mobile users in moving vehicles. The idea of Drive-thru Internet is to provide hot spots along the road -- within a city, on a highway, or even on high-speed freeways such as autobahns. They need to be placed in a way that a vehicle driving by will obtain WLAN access for some (relatively short) period of time; if located in rest areas, the driver may exit and pass by slowly or even stop to prolong the connectivity period. One or more locally interconnected access points form a so-called connectivity island that may provide local services as well as Internet access. Several of these connectivity islands along a road or in the same geographic area may be interconnected and cooperate to provide network access with intermittent connectivity for a larger area. IEEE 802.11 (WLAN) technology today is mainly applied to stationary networks, e.g., wireless campuses and commercials hot spots, where stations can be mobile but are typically limited to a certain range that is defined by the coverage of a set of co-located access points. The use of unlicensed spectrum, the ease of deployment and the achievable throughput of up to 54 MBit/s (for IEEE 802.11a and 802.11g) are the main factors for an easy and cost-efficient deployment of WLAN technology. The limited transmission power and the limited range of a single access point allow for spontaneous, uncoordinated installations. As a consequence, virtually anybody with WLAN access point hardware can act as an Internet service provider and can offer high-speed, cost-efficient though geographically limited WLAN-based Internet access. In the Drive-thru Internet project, we apply WLAN technology to a rather unusual scenario: providing network access for fast moving vehicles. Based on the previously mentioned properties (high throughput, cost effectiveness, ease of deployment) we develop an architecture that allows for providing useful connectivity considering difficulties such as intermittent coverage. Our approach is that intermittent connectivity is the rule rather than the exception and must be taken into account in general. More information on the motivation for the Drive-thru Internet idea can be found at Motivation. The Drive-thru Internet scenario is an example of a networking environment where fundamental assumptions of Internet protocols do not hold: connectivity is not permanent, link characteristics change dramatically, and the end-to-end paradigm cannot necessarily be applied. Other examples of such extreme networking environments are Delay Tolerant Networking (DTN) and mobile ad-hoc networks. More information on related network architectures and approaches can be found at Links. |
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