Primary system interference analysis for cognitive radio transmission power control

Cognitive radio (CR) improves radio spectrum utilization and offers new opportunities for future wireless services. It is designed to operate in frequency bands that are licensed to other primary radio users while ensuring no harmful interference to the licensed users´ operations. By knowing the geo-locations of the CRs and the licensed users, it is possible to allow CR to access licensed bands without causing interference. In this paper, a transmission power control scheme for CRs is proposed to minimise the interference to licensed users. The scheme utilises mainly location information to estimate primary systems service reliability as the main power control indicator to determine the transmission power. Primary system interference analysis has been conducted as a part of the scheme and a model of an exclusion zone centred on a primary transmitter (PT) has been developed. This model is also specified by the Federal Communications Commission (FCC). Interference analysis at the centre and the edge of the exclusion zone has been performed by other researchers. In this paper, an analysis of the interference power level across the entire coverage area has been conducted. The effect of shadowing has also been included in the evaluation. The interference power statistics have been analysed for the entire coverage area. Analytic studies and Monte Carlo simulations are in agreement.