On The Performance of Underlay Relay Cognitive Networks

Abstract

The bit error rate (BER) performance of underlay relay cognitive networks in the presence of Rayleigh fading isthoroughly analyzed in this paper. New exact and asymptotic analytic expressions under consideration of both interferencepower constraint and maximum transmit power constraint are derived in closed-form and are extensively corroborated byMonte-Carlo simulations. These expressions facilitate in evaluating effectively the network performance behaviour in keyoperation parameters as well as in optimizing system parameters. A multitude of analytical results expose that underlayrelay cognitive networks experience the performance saturation phenomena while their performance considerably dependson the number of hops for the linear network model. Additionally, optimum relay position is significantly dependent ofmaximum transmit power, maximum interference power, and licensee location. Moreover, the appropriate order of locatingunlicensees with different maximum transmit power levels can dramatically improve the network performance.