Interference-Controlled Transmission Schemes for Cognitive Radio in Frequency-Selective Time-Varying Fading Channels

Interference control is crucial in cognitive radio networks and the existing related works focus on quasi-static channels. The expansion of wireless services and applications in everyday life has necessitated support of higher mobility, as evident from the emerging wireless standards. This results in time-varying fading channels within a transmission frame for which the interference power control schemes and power allocation strategies have not been developed yet. This paper proposes several interference control and power allocation strategies with different criteria for underlay cognitive radios in time-varying frequency-selective fading channels and extend the transmission schemes to multiple secondary systems. The transmission schemes are evaluated in terms of interference statistics at the primary receiver and the ergodic capacity of the secondary user link. Simulation results over the wide Doppler range show how the proposed schemes with different criteria shape the interference at the primary receiver and the capacity of the secondary user. The results also illustrate better interference control capability of the proposed approaches over the existing scheme.