COGNITIVE RADIO
Allowing secondary users to choose an available channel from
among a wide spectrum range thus enables reliable communication in this context,
but communication characteristics such as bottleneck bandwidth and RTT will
change with channel switch. In response to this change, TCP has to adaptively
update its congestion window (cwnd) to make an efficient use of the available
resources. For this purpose, TCP CRAHN was proposed for CogMANET. In this
paper, TCP CRAHN is first evaluated in cases where bottleneck bandwidth and RTT
drastically change. Based on these results, TCP CoBA is proposed to further
improve the throughput of the above use cases. TCP CoBA updates the cwnd based
upon the available buffer space in the relay node upon channel switch, as well
as other communication characteristics.
Cognitive radio technology has the potential to ameliorate the
scarcity of wireless resources because unlicensed users (secondary users: SUs)
can use wireless resources only if they have no impact on the operations of licensed
users (primary users: PUs). In the future, cognitive radio mobile ad hoc
networks (CogMANET) will be constructed from many mobile SUs connected to each other
in a distributed manner, which can be deployed for various applications,
including intelligent transport systems (ITS).
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