Ghayoor Abbas Jafri; Ateeq Ur Rehman; Muhammad Tariq Sadiq , pp. 89. ING/School of Engineering, 2011.
In the last few years, there has been enormous improvement in mobile communication services. Due to this rapid growth in the field of communications, the demand for wireless spectrum has increased rapidly. In the early days in order to remove the interference problem, the spectrum was assigned statically. To assign the spectrum statically, the fixed spectrum assignment policy was used. Due to the fixed spectrum assignment policy, the spectrum was not efficiently utilized and remained vacant most of the time. The study by Federal Communications Commission (FCC) shows that the spectrum is available but its usage is not efficient. Such kind of spectrum inefficiency can be overcome by the use of Cognitive Radio.
Cognitive Radio is a new technology that allows the secondary users (SUs) to use the spectrum whenever it is available. In this thesis, an Opportunistic Cognitive MAC Protocol (OC-MAC) has been proposed for the Cognitive Radio to access the unoccupied spectrum opportunistically and coexistence with the ad hoc Wireless Local Area Network (WLAN).
OC-MAC is a decentralized MAC protocol over Cognitive Radio network along with WLAN. In the OC-MAC protocol, there is a dedicated control channel over which the cognitive nodes compete with each other for the reservation of the data channel. The handshaking phenomenon for the reservation of data channels is performed on the control channel. After a selection of the appropriate data channel, when a secondary user starts using the data channel and the primary user claims it, the SU leaves the spectrum and moves to another available channel. The transmission of data by the secondary user is confirmed by receiving an acknowledgement. In this way secondary user utilizes the unused frequency spectrum while maintaining acceptable collision rate among secondary users and between secondary users and primary users.
All simulation scenarios are developed in OPNET v14.5 Network simulator and simulation results are collected for different scenarios; under light and heavy traffic to check the performance of the OC-MAC protocol.
+46 760 653865