Real-time Communication in Vehicular Ad Hoc Networks (VANETs)

messages, with varying transmission powers for each. For example, in [8] the
authors use a combination of low-frequency long-range infrastructure-based
communications and high-frequency vehicle–to-vehicle communication in
order to accommodate the varying delivery requirements for each message
type.
FCC ruling defines DSRC have six service channels and one control channel.
The control channel is to be regularly monitored by all vehicles. Safety
message is denoted to highest priority. [3]
In mobile Ad Hoc network, there are two kinds of nodes – exposed nodes
which are within the interference range of each other, and hidden nodes
which are out of interference range. The number of exposed nodes impacts
network throughput. We can increase the network throughput not only by
incrementing the number of nodes, but also enlarging the network size while
keeping traffic load constant [1].
However, the number of exposed nodes is related with radio range. Since the
interference radius is proportional to the radio range, increasing the radio
range to increase link stability, path life, or network connectivity will decrease
the network throughput. On the other hand, directional antennae could be
used to reduce the interference range. In this way, a transmission interferes
only with nodes in the direction of the transmission. However, directional
antennas increase the number of hidden nodes and have an adverse affect on
intrusion-detection systems. [9]
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