INTRODUCTION
Recently, the Global Positioning System (GPS) [1]
navigation system has become one of the most lovable
applications for people. However, if information of the
electronic map is out of date or some traffic incident or road
maintenance event occurs in real time, the GPS navigation
system may plan an erroneous route. Though the real-time
online road information supported by the Radio Data
System-Traffic Message Channel (RDS-TMC) [2] has
improved this problem, the on-board GPS navigation system
may not receive useful road information from RDS-TMC to
help route planning. GPS navigation apps such as Garmin
StreetPilot Onboard [3] for Apple iPhone/iPad or
PaPaGo!Mobile [4] for the android platform are more and
more prevalent. If wireless connection is available, these
apps can retrieve real-time traffic information from Internet
to plan a faster route by avoiding roads under construction.
IEEE 802.11p, i.e., the WAVE architecture [5], has been
designed for short-range vehicle-to-vehicle (V2V)
communication. When people drive on the road, these
vehicles can transfer information to each other through a
dynamically formed vehicular ad-hoc network (VANET) [6].
If a vehicle has met a traffic incident, it can send safety
messages to warn its neighboring vehicles of information