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RESEARCH
Cognitive Radio Networks
A cognitive network is an opportunistic network. The basic premise of a cognitive
network is that the owner of a licensed spectrum may not be using the spectrum
always. Hence, this unused and licensed spectrum can be utilized by other users who
have a need for the same. The licensed owner of a frequency band is called a primary
user and the one who utilizes spectrum opportunities for communication is called a
secondary user. Networks built using this concept are called cognitive radio networks.
The part of spectrum, allocated to a user for communication, is referred to as
a channel. A channel is temporarily available to a secondary user when the primary
user of that channel is not using it at that instant of time. Every secondary user is
assumed to have the capability of sensing a channel for the presence of primary user
using a cognitive radio i.e. every secondary user is assumed to have a cognitive PHY
layer. Thus, a secondary user may have a set of free channels (available channels)
for communication. One of the available channels is chosen for communication. An
important constraint on the choice of the channel is that, both the sender and receiver
should be on the same channel for possible communication.
If the receiver is not in communicating range of the sender, the communication has to be set up through
several intermediate nodes. Such types of networks are called Multi-hop Cognitive
Radio Networks(MHCRN).
Vehicular Networks
Vehicular Networks (also known as VANETs) are a cornerstone of the envisioned
Intelligent Transportation Systems (ITS). By enabling vehicles to communicate
with each other via Inter-Vehicle Communication (IVC) as well as with roadside
base stations via Roadside-to-Vehicle Communication (RVC), vehicular networks will
contribute to safer and more efficient roads by providing timely information to drivers
and concerned authorities. The interesting research area of Vehicular Networks is where
ad hoc networks can be brought to their full potential.
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