Vehicular networks provide Internet services, such as
traffic jam information and locations of gas stations etc., for
car drivers [1]. Vehicles equipped with radio communication
devices can communication with neighbor vehicles or base
stations. Two possible interfaces of communication devices,
WiFi or cognitive radio, are available to vehicles. WiFi uses
unlicensed spectrum band and communicates in a distributed
communication manner, which leads to that vehicles can
access network services in a cheap and scalable manner. Due
to the demand for various network service and limited
spectrum of WiFi, it is unsatisfactory for vehicular networks
with WiFi to provide broadband services. Cognitive radio
provides an opportunity to access additional spectrum bands,
which uses the idle spectrum of licensed spectrum band to
send a message [2]. In practice, multiple radio access
technologies are usually used in existent mobile devices and
are expected in the next generation wireless networks [3].
Therefore, in this paper, we consider the vehicular networks
with the two radio interfaces, cognitive radio and WiFi.