Network-Aware Adaptive LBT (NALT) Coexistence Mechanism

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.