Recent Advances of LTE/WiFi Coexistence in Unlicensed Spectrum

U-LTE is a new wireless technology that is currently being developed by industry and academia to offer LTE service in unlicensed spectrum. U-LTE addresses spectrum shortage from 4G LTE cellular networks by allowing them to operate in unlicensed bands. To ensure fair spectrum sharing among different wireless technologies (LTE and WiFi in particular), a number of coexistence mechanisms have been proposed. These mechanisms operate in the time, frequency, or power domains to minimize potential adverse effects from LTE. Based on these mechanisms, a number of U-LTE standards are being developed by industry. In this article, we present recent advances in this exciting area by reviewing the state-of-the-art LTE/WiFi coexistence mechanisms and show how they are incorporated into industry standards. We also point out several key challenges and open problems for future research.