LAUSR

Faster development of smart electronic devices in recent years along with significant increase in demanding higher data rates has made cognitive radio networks (CRNs) to be taken into consideration as a promising technology. A CRN has the ability to increase spectral efficiency (SE) of communication systems by opportunistically using unused spectrums. Furthermore, Massive multiple-input multiple-output is a major candidate to be used in next generation cellular systems in light of its great capabilities to improve system performance from spectral as well as energy efficiency standpoint. In this paper, we propose a CRN whose base station, as well as the primary base station (PBS) are equipped with large numbers of antennas. We derive closed-form expressions for SE in the uplink of primary users for three different scenarios. In these scenarios perfect and imperfect channel state information are considered separately. In addition, the impact of pilot contamination due to the correlation among users’ pilot signals on sum SE of primary network is examined. For the first two scenarios, minimum number of antennas (MNA) at the PBS to achieve a specified SE is derived in a closed-form expression. MNA is analyzed numerically for the third scenario.