Simulating LTE and Wi-Fi Coexistence in Unlicensed Spectrum with ns-3

TL;DR

This paper introduces an open-source ns-3 simulation extension for studying LTE and Wi-Fi coexistence in unlicensed spectrum, enabling detailed performance analysis of coexistence techniques like LTE LBT.

Contribution

The paper presents the first open-source ns-3 models for LTE Wi-Fi coexistence, including full system simulations with upper-layer protocols, facilitating reproducible research.

Findings

Successfully reproduced literature performance metrics

Extended simulations with TCP traffic reveal complex coexistence behaviors

Identified open questions on LBT implementation for better coexistence

Abstract

The use of unlicensed spectrum for future LTE systems raises concerns about its impact on co-located Wi-Fi networks. We report herein on extensions to a popular network simulator, known as ns-3, to model such coexistence. To our knowledge, this simulator is novel in two important ways. First, it is presently the only freely available simulator for coexistence studies, and as open source software, it offers new opportunities for reproducible research and collaborative model development. Second, we are not aware of other simulators with similar wireless models that allow full system studies to be conducted, such as performance evaluation of upper-layer protocols in a coexistence environment. We illustrate the value of a system simulator by describing a simulation campaign for the indoor scenario designed by 3GPP RAN1 using new ns-3 models for Release 13 LTE Listen Before Talk (LBT) techniques, intended for fair coexistence with Wi-Fi. LBT models have been widely simulated at the link and physical layer by many companies in 3GPP RAN1. We first show that we are able to tune the scenario to reproduce similar performance metrics to those reported in the literature. We then extend the simulations by adding TCP to the file transfers and explore the different behaviour observed. Our initial study reveals that there remain many open questions about how LBT should be implemented to achieve good coexistence properties, and that a broader scope of implementation issues, traffic models, and fuller system models should be studied further before drawing final conclusions on the LBT coexistence performance.