Performance modeling of Pre-authentication and handoff mechanisms in IEEE 802.11 based vehicular networks

The increase in multimedia usage places stringent requirements on wireless network performance in terms of lesser handoff delays. A VOIP client, for example, cannot tolerate a delay larger than 150 ms between the incoming voice packets to ensure a satisfactory interactive service to the user. Of the 150ms, only 50ms is allowed for handoff and the rest should accommodate the transmission delay of the packet over the Internet. Unfortunately, the handoff delay itself in case of robust authentication mechanisms like IEEE 802.1x is so large that the time spent in handoff is more than the time the mobile client remains connected to the Access Point. Pre-authentication therefore is a viable alternative though it causes a considerable increase in the network overload owing to the increase in the number of service requests and thence in the network queue sizes. It becomes imperative to evaluate the network performance in order to know the relevance and advantages of pre-authentication to minimize handoff delay. We study the effect of network overload on handoff delay. Subsequently, we modeled a network in which a mobile VOIP client communicates with the other via a network cloud comprising the access points and authentication servers.