Energy efficiency impact of cognitive femtocells in heterogeneous wireless networks

The recent surge in mobile broadband traffic has been accompanied by diminishing revenues per bit and spectral bottleneck for mobile cellular networks. For this purpose, cognitive radio concept embedded in smaller cells, i.e. cognitive femtocell networks (CFNs), is promising as a potential component of future heterogeneous networks. However, the ongoing mobile traffic explosion is also expected to result in higher energy consumption and larger carbon footprint which is a major challenge against green communications objective. Thus, energy efficiency (EE) has become a key research focus for these broadband access systems. In this work, we analyze the introduction of cognitive femtocells into wireless networks from energy efficiency perspective. We propose an analytical model for such CFN-deployed heterogeneous networks and evaluate the impact of CFN proliferation on energy consumption discussing the relevant tradeoffs and practical issues. We observe two fundamental findings: 1- CFN is beneficial for improving EE. 2- The resultant EE gains are dependent on intricate factors entailing fem-tocell deployment density, CFBS proliferation rate, sensing period selection and interference management.