DRX in New Radio Unlicensed: A Step Beyond 5G Wireless

5G wireless has ushered in new promises of improved performance and ubiquitous connectivity. However, a continuous increase in connected devices and the proliferation of the Internet of Things have already created skepticism about the capacity of 5G wireless to satisfy the huge data requirements across a myriad of devices. This has made wireless researchers, vendors, and standards bodies look beyond 5G wireless by extending 5G New Radio (NR) in unlicensed bands. Operation in unlicensed bands requires additional channel sensing and fairness across different types of networks. This makes power consumption in battery-constrained mobile devices more challenging. In this article, we introduce two different aspects of discontinuous reception (DRX) for energy and resource savings in 5G NR unlicensed networks. As 5G NR is based on directional beams, the proposed solutions are based on beam searching and beam awareness. Beam-aware DRX explores next generation NodeB's assistance to alleviate mobile user equipment's (UE's) beam searching burden and results in more power saving. Simulation experiments using real wireless traces demonstrate that our NR-U DRX solutions significantly improve UE's power saving and network resource utilization over existing 5G NR DRX.

I Introduction

Recent years have witnessed a phenomenal growth in wireless connectivity. Penetration of smartphones, introduction of Internet of Things (IoT) devices, and emerging new multimedia applications have significantly contributed toward this growth. While these smart devices and applications have improved our quality of life and unveiled new industrial opportunities, the resulting growth in traffic and users is burdening the resource-constrained cellular networks. Naturally, wireless operators are looking for more spectrum to cater for this increase in demand. As the scarce licensed spectrum imposes several cost constraints, unlicensed bands are recently being considered as one of the key future technologies [1], [2]. However, allowing cellular networks to operate in the unlicensed spectrum, while maintaining graceful coexistence with other unlicensed technologies like WiFi, is a major challenge. This has led to the evolution of different variants of 4G wireless, like License Assisted Access (LAA) [3] and enhanced LAA (eLAA) in Third Generation Partnership Project (3GPP) Releases 13 and 14, respectively. While LAA introduces an additional unlicensed carrier, assisted by the licensed carrier in the downlink (DL), eLAA extends LAA even in the uplink (UL). Unfortunately, even with the inclusion of unlicensed spectrum, commercial 4G wireless systems cannot satisfy the almost exponential increase in connectivity (IoT devices, smartphones, machine type communications [MTC], etc.).