A semi-distributed LTE-WiFi system design for future LTE-unlicensed: Deployments in small-cell environments

In order to accommodate the exponentially-growing data traffic, LTE operators are considering the extension of the LTE operation into the unlicensed bands. In a recent technical report for the third Generation Partnership Project, Licensed-Assisted Access (LAA) to the unlicensed spectrum has been introduced. The report and other works in the literature reveal coexistence challenges that are raised when the LTE system coexists with other technologies such as WiFi, with fairness being the primary challenge. In this work, we propose a preliminary design for a semi-distributed LTE-Unlicensed scheme where the LTE Base Station uses WiFi-like carrier sense, back-off, and Quality of Service facility techniques. We also present a study on LAA-WiFi-coexistence through ns3 simulations. We conclude from our simulations that our preliminary design can achieve fairness in a limited set of scenarios, and we highlight the requirements and challenges that need to be considered in future work for designing a fair scheme for a wider set of scenarios.