Network-Aware Adaptive LBT (NALT) Coexistence Mechanism

Abstract

In the absence of coordination between radio access technologies (RATs), and with the goal of deploying unlicensed LTE without requiring changes to the Wi-Fi MAC layer, it falls to the LTE base stations to ensure fair coexistence. The multiple access method used in Wi-Fi is designed for fair sharing of the channel with devices operating toward the same goal. Following this paradigm, if LAA-LTE is not carefully designed to ensure fairness, it can easily lead to Wi-Fi stations being barred from the channel. The greatest gains in fair coexistence are achieved when LAA-LTE behaves in as Wi-Fi-like a manner as possible; however, this may not allow LTE to make the best use of the channel. In this chapter, a Network-aware Adaptive LBT mechanism (NALT) is presented which passively monitors both channel conditions and usage activity to maximize transmission opportunities while respecting fair sharing of the channel, all in a way that is transparent to incumbent Wi-Fi devices. Simulation results are presented demonstrating the effectiveness of NALT in providing proportional fair sharing among LAA-LTE and Wi-Fi devices.