Dynamic Reuse of Unlicensed Spectrum: An Inter-Working of LTE and Wi-Fi

The dynamic exploitation of unlicensed spectrum by mobile operators is becoming a trend of future 5G networks, with several efficient solutions being standardized for enabling spectrum sharing. Solutions with various design philosophies diversify the network architectures and protocols. Among them, licensed-assisted access (LAA) aims at the physical-layer coexistence of Long-Term Evolution (LTE) and Wireless Fidelity (Wi-Fi) within the unlicensed spectrum, while LTE-WLAN aggregation (LWA) and LTE-WLAN radio level integration with IPsec tunnel (LWIP) focus on aggregating the link capacity of LTE in the licensed spectrum and Wi-Fi in the unlicensed one. In this article, a comprehensive survey of these three spectrum sharing technologies are provided. Moreover, a novel analytical framework is proposed to evaluate the network performance of these technologies by incorporating both spatial and time domain analyses and integrating different types of cells in one network as a whole. Simulation results are provided to compare the system throughput of these spectrum-reuse technologies.