Effects of Heterogeneous Frequency Changes in Cognitive Radio Femtocell Networks
Wahida Nasrin, Jiang Linda Xie · 2016
Recently, cognitive radio (CR) technology is proposed to be combined with femtocell networks, which enables femtocells to access the available spectrum bands in an opportunistic manner. In practice, the available spectrums in CR femtocell networks are heterogeneous and range from hundreds of megahertz to several gigahertz. These heterogeneous spectrums have very different path- losses which may result in significantly different transmission and sensing ranges. Therefore, the change of operating frequency in CR femtocell networks introduces unique challenges. Although the effects of operating frequency are studied in pure CR networks, issues related to the femtocell network and impacts on the sensing range are never addressed. In this paper, we introduce some unique challenges resulting from frequency changes in CR femtocell networks, such as femtocell under-utilization and interference due to the change of the transmission range, and detection error and false alarm to the change of the sensing range. In addition, we propose a power control scheme to address the issue of the transmission range change. We also propose a detection sensitivity selection scheme to reduce the effect of the sensing range change. Simulation results show significant performance improvement of our propose schemes. To the best of our knowledge, this is the first paper that investigates the impact of frequency changes on both transmission range and sensing range in CR femtocell networks.