On the Ergodic Capacity in Multicarrier Cognitive Radio Systems under Power Constraints
Abstract
This paper presents an analytical solution for the ergodic capacity of a cognitive radio (CR) link sharing with a primary link the same spectrum in the multicarrier transmission mode. The spectrum sharing (SS) mode of operation for the CR link is considered. Assuming Rayleigh fading channels, the ergodic capacity of the CR link is derived analytically under two joint average power constraints an average interference power (AIP) limit at the primary receiver and an average transmit power (ATP) limit at the CR transmitter. The analytical results of the maximal ergodic capacity of the CR link are derived based on an optimal water-filling power allocation in the CR transmitter. These results are validated with numerical simulations. They are also compared, in the single-carrier mode, with previous results obtained with a peak transmit power (PTP) constraint at the CR transmitter.