Date Added: Aug 2011
Cognitive Radio (CR) is considered as one of the prominent techniques to improve the spectrum utilization by opportunistically sharing the radio spectrum resources with licensed users. This paper concentrates on characterizing the spectral-energy efficiency tradeoff in low and high Signal-to-Noise Ratio (SNR) regimes for interference-tolerant CR networks under peak interference power constraints and in different fading environments. The analysis has been conducted under an assumption that perfect Channel State Information (CSI) of both primary and secondary receivers is available at the secondary transmitter. The authors' analysis proves that, in the low SNR regime, the minimum energy per bit required for reliable transmission is characterized by the supremum of the CR fading channel.