Admission Control for Roadside Unit Access in Intelligent Transportation Systems

Roadside units can provide a variety of potential services for passing-by vehicles in future Intelligent Transportation Systems. Since each vehicle has a limited time period when passing by a roadside unit, it is important to predict whether a service can be finished in time. In this paper, we focus on admission control problems, which are important especially when a roadside unit is in or close to overloaded conditions. Traditional admission control schemes mainly concern long-term flows, such as VOIP and multimedia service. They are not applicable to highly mobile vehicular environments. Our analysis finds that it is not necessarily accurate to use deadline to evaluate the risk whether a flow can be finished in time. Instead, we introduce a potential metric to more accurately predict the total data size that can be transmitted to/from a vehicle. Based on this new concept, we formulate the admission control task as a linear programming problem and then propose a lexicographically maxmin algorithm to solve the problem. Simulation results demonstrate that our scheme can efficiently make admission decisions for coming transmission requests and effectively avoid system overload.