  Most of the research in cognitive radio field is primarily focused on finding
and improving secondary user (SU) performance parameters such as bit error
rate, outage probability and capacity etc. Less attention is being paid towards
the other side of the network that is the primary network which is under
interference from SU. Also, it is the primary user (PU) that decides upon the
interference temperature constraint for power adaptation to maintain a certain
level of quality of service while providing access to SUs. However, given the
random nature of wireless communication, interference temperature can be
regulated dynamically to overcome the bottlenecks in entire network
performance. In order to do so, we need to analyze the primary network
carefully. This study tries to fill this gap by analytically finding the closed
form theoretical expressions for signal to interference and noise ratio (SINR),
mean SINR, instantaneous capacity, mean capacity and outage probability of PU,
while taking peak transmit power adaptation at SU into picture. Furthermore,
the expressions generated are validated with the simulation results and it is
found that our theoretical derivations are in perfect accord with the
simulation outcomes
