Planning of Ultra-Dense Wireless Networks

Fifth generation (5G) wireless networks adopt the deployment of ultra-dense small cells for efficient slicing of radio resources. This conceptual change in network structure aims to meet the rapid increase in mobile data traffic and connected devices. However, limited free spectrum and dynamic assignment of resources are main concerns when considering the cognitive small cells solution. Therefore, there is a need to map traffic patterns with the number of cognitive small cells to provide an optimized network architecture operating with adequate spectrum resources. This article investigates the case when network densification exceeds the radio resource capacity, causing a large scale overlapping in cell coverage area and used channels. Taking into consideration cognitive network performance characteristics, we identify two spectrum coexistence frameworks, Space Filling and Time Filling, to improve spectrum utilization and scalability for moderately large networks. Simulations show that there is a turning point when network performance starts to decline as the number of cognitive small cells exceeds the shared resources in a site area, subject to a certain load profile. This optimization of network structure, based on spectrum transmission opportunities, brings about a new topic for operators and research communities considering small cells operating in the unlicensed band.