  The effect of the primary traffic on a secondary user's (SU) throughput under
Rayleigh flat fading channel is investigated. For this case, closed form
expressions are derived for the average probability of detection and the
average probability of false alarm. Based on these expressions, the average SU
throughput under the desired signal-to-noise ratio (SNR) constraint in order to
maintain the quality of the secondary link is found analytically considering
the random arrival or departure of the primary user. It is shown that the
spectrum sensing performance and SU throughput degrade with increase in the
primary traffic and the deep fade condition of the channel over which the
detection is performed. The degree of degradation in SU throughput is seen to
be severed further due to the interference link from the primary transmitter to
the secondary receiver. Under these detrimental effects, a sensing-throughput
trade-off for SU is illustrated. Finally, the combined effect of the primary
traffic, fading, imperfect spectrum sensing and the interference link from a
primary transmitter is studied on the outage probability at SU.
