Standalone LTE in Unlicensed Spectrum: Radio Challenges, Solutions, and Performance of MulteFire

The deployment of standalone LTE radio technology in unlicensed spectrum can enable new business cases, by leveraging the assets of LTE, to industry players not having access to licensed spectrum. With this objective in mind, the Multe- Fire Alliance has recently finalized the first release of the MulteFire standard specifications. MulteFire makes the deployment of standalone LTE radio technology possible in the 5 GHz unlicensed spectrum. It combines the simplicity of deployment of WiFi with the spectral efficiency and carrier- grade quality of LTE. MulteFire is targeted at enhanced mobile broadband services, but is also suited for IoT applications, as it inherently supports many connected devices. It also offers more reliable communication, as compared to competing technologies working in the unlicensed spectrum. This article provides an overview of the research challenges and solutions of deploying the LTE radio technology in unlicensed spectrum. We summarize the main regulatory requirements in the 5 GHz unlicensed band, and describe the needed modifications to the LTE specifications. We also demonstrate, by means of detailed system- level simulations, how MulteFire can improve the system capacity and coverage, as compared to WiFi, in specific propagation environments and small cell deployments.