Fahim Khan, Taimour Khan and Muhammad Fahad
Cognitive radio is an emerging radio technology that can improve the efficiency of the radio spectrum utilization. Cognitive radio senses the vacant space in the radio spectrum by changing its operating parameters and uses the vacant spectrum in an opportunistic way and immediately vacates the spectrum bands once the primary user (PU) is detected. The cognitive radio efficiently uses radio spectrum by operating in both licensed and unlicensed bands and avoids the interference with the licensed or unlicensed users. The PU holds the license for a particular band and has the priority to use the channel. The secondary user (SU) can use the vacant bands as long as they do not affect the PU transmission. However, previous research work has ignored the effect of interference from primary networks on the performance of spectrum sharing system. In this paper, the performance of amplify-and-forward relay networks, where the interference from the primary networks is considered, is studied. We considered the impact of the primary transmitter on the spectrum sharing system in the presence of a Nakagami-m fading channel, where the fading parameter m (m is an integer) can be used to deal with a variety of channel scenarios. A closed-form of Nakagami-m fading channel is derived. Derivation is based on the system model composed by secondary users, primary users and amplify-and-forward relay.
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