Introduction

Abstract

The increasing penetration of mobile-connected devices and the emergence of numerous data-hungry mobile applications have created a wide range of business opportunities for mobile network operators and service providers. Meanwhile, this growth is placing a greater pressure on the capacity that the Radio Access Networks (RANs) have to provide. This chapter begins with a review of technical challenges that motivate developments of cost-effective solutions to improve the capacity of RANs. The technology that utilizes the unlicensed frequency bands in Long-Term Evolution (LTE), namely U-LTE, is singled out as the most promising solution. Benefits and obstacles of this technology are then presented. Next, three typical forms of U-LTE including LTE-U, LAA-LTE, and MulteFire™  are explained. Concerns on the interactions between U-LTE and Wi-Fi in radio channel access and their coexistence are discussed in detail. Finally, key requirements for the coexistence of U-LTE and Wi-Fi are summarized.