Alpha Coverage: Bounding the Interconnection Gap for Vehicular Internet Access

Vehicular Internet access via open WLAN access points (APs) has been demonstrated to be a feasible solution to provide opportunistic data service to moving vehicles. Using an in situ deployment, however, such a solution does not provide worst-case performance guarantees due to unpredictable intermittent connectivity. On the other hand, a solution that tries to cover every point in an entire road network with APs (full coverage) is not very practical due to the prohibitive deployment and operational cost. In this paper, we introduce a new notion of intermittent coverage for mobile users, called a-coverage, which provides worst-case guarantees on the interconnection gap while using significantly fewer APs than needed for full coverage. We propose efficient algorithms to verify whether a given deployment provides alpha-coverage and approximation algorithms for determining a deployment of APs that will provide alpha-coverage. We compare alpha-coverage with opportunistic access of open WLAN APs (modeled as a random deployment) via simulations over a real-world road network and show that using the same number of APs as random deployment, alpha-coverage bounds the interconnection gap to a much smaller distance than that in a random deployment.