Impact of primary user duty cycle on cognitive secondary user utilization efficiency in a generalized κ-μ fading channel

Efficient spectrum utilization by secondary users (SU) during the inactivity phase of primary users (PU) is of utmost interest for dynamic spectrum access in a cognitive radio environment. In this paper, we investigate the utilization efficiency of cognitive radio users with respect to the realistic estimate of PU duty cycle (DC) in AWGN and generalized κ-μ fading channels for a fixed interference ratio. We have adopted a two-state hidden Markov model (HMM) for capturing PU activity. PU duty cycle is calculated by considering exponentially distributed ON-OFF channel model. Performance evaluation has been done by two approaches: one is the conventional approach which is widely used and the other is based on a-posterior log-likelihood ratio (LLR). As per prior investigations, the LLR approach is found to be very useful in evaluating SU utilization in AWGN channels. In the present work, we have extended similar analysis to generalized fading channel model. Our analytical studies demonstrate a significant decrease in SU utilization efficiency in a fading environment as compare to AWGN while LLR approach still outperforming the results of the conventional scheme.