Delay Analysis of In-Vehicle Internet Access Via On-Road WiFi Access Points

Providing cost-effective and high throughput WiFi access for vehicle drivers and passengers is a promising solution to support the increasing demand for in-vehicle Internet applications. Prior to accessing Internet services via an on-road WiFi access point (AP), a vehicle user has to wait for a certain duration, referred to as access delay, until the user is authenticated and assigned proper network layer parameters, such as an Internet protocol address. Investigation of the access delay in a vehicular environment is critical, since a large access delay can significantly reduce the duration that a vehicle actually benefits from Internet connectivity during its temporary existence within the coverage area of an on-road WiFi AP, especially with high vehicle moving speeds. In this paper, we propose an analytical model based on a Markov chain to study the dependency of the access delay on different factors, including the wireless channel conditions, the number of vehicles accessing the AP service, and the employed authentication mechanism, such as the WiFi protected access II (WPA2)-pre-shared key and the WPA2-802.1X modes. The accuracy of the analytical model is studied via computer simulations and experimental testing using commercial off-the-shelf WiFi products together with a channel emulator that emulates the wireless channel conditions in a vehicular environment. Simulation and experiment results highlight the accuracy of the proposed analytical model. Results in this paper provide useful guidelines for future selection/development of suitable WiFi network access schemes in a vehicular environment.