UNII-MAC protocol: Design and evaluation for 5G ultra-dense small cell networks operating in 5 GHz unlicensed spectrum

Ultra-densification and efficient spectrum utilization are key features for the next 5G wireless networks to address the well-known challenges of high capacity demands and mobile data traffic explosion. In this article, a physical layer and a medium access control (MAC) sublayer are presented for small cells to operate in the 5 GHz unlicensed national information infrastructure (UNII) band. The physical layer is based on filter bank multi-carrier modulation able to achieve better spectral efficiency and access flexibility. The MAC protocol is based on beacon-enabled superframe consisting of scheduled and contention access schemes. The proposed UNII-MAC design relies on a listen-before-talk procedure in order to comply with ETSI regulations and to fairly coexist with neighboring systems sharing the same band. The performance of the UNII-MAC is then evaluated in dense indoor/outdoor deployment scenarios under various parameters and traffic patterns. Moreover, the coexistence between UNII-MAC and WiFi systems is reported. Based on the obtained results, we provide recommendations for 5G small cell deployment in dense environments.