Impact of transmit power control on aggregate interference in underlay cognitive radio networks

This paper analyzes how transmit power control affects the aggregate interference arising from a Poisson field of underlay cognitive radio (CR) transmitter nodes distributed in a finite area. We consider three per-user, location dependent power control schemes, when each CR transmitter is associated with the nearest CR receiver, where the CR receivers form a Poisson field in the entire 2-dimensional space. The 3 schemes are based on: 1) CR transmitter-receiver distance r_c 2) r_c and a constant cut-off power level 3) r_c and a random cut-off power level, respectively. For each of these, the exact moment generating function (MGF) and mean of aggregate interference power are derived. We also investigate the primary system outage due to aggregate interference. Rayleigh fading and exponential path loss links are assumed. Monte-Carlo simulation results validate our analysis and also show that the CR power thresholds and node densities significantly affect the aggregate interference.