چکیده (انگلیسی):

The constraint of limited frequency spectrum for wireless
communication is very daunting. The radio spectrum licensed to permanent
users is wasted at times when not used continuously. Cognitive radio
technology involves a change in regulation of radio spectrum. In cognitive
radio networks a secondary user network is designed for efficiently using
gaps in spectrum and not causing at the same time harmful interference to
license holding primary users. Opportunistic spectrum access involves the
sensing of white spaces in the transmissions of Primary Users and their
utilization by Secondary Users. There is a continuous tradeoff between the
opposing goals of Primary User transmission protection and Secondary
User throughput maximization. For a Secondary User, sensing is important
so as to avoid collisions, hence packet loss. At the same time being too
cautious and having long sensing periods can be costly. This paper presents
optimization of Secondary User sensing time in sensing-transmission
scheduling for dynamically accessing the spectrum in cognitive radios. The
need to maximize the Secondary User access is achieved by optimizing its
sensing time with respect to collision cost in a threshold based sensingtransmission
structure using simulations. The results are presented in the
form of traces of thresholds for different sensing times and collision costs.
This scheme optimizes Secondary User throughput while safeguarding
Primary User interests. This defines a standard to give an insight into the
design of sensing-transmission scheduling in cognitive radio networks.