Impact of LTE Operating in Unlicensed Spectrum on Wi-Fi Using Real Equipment

The proliferation of mobile devices and the exponential growth of data transmitted over the air pushed the wireless community to find solutions in order to increase network capacity and fully exploit the available spectrum. Recently, 3GPP announced the operation of LTE in the unlicensed spectrum in order to offload the limited and expensive licensed spectrum. Concurrently, leading parties of the wireless community examine standalone operation of LTE in unlicensed spectrum. LTE was initially designed to operate in licensed spectrum and does not use any channel estimation mechanism to determine ongoing transmissions by other co-located networks. This introduces important coexistence challenges in unlicensed spectrum between LTE deployments and the current, well-established technologies, such as IEEE 802.11 (a.k.a. Wi-Fi). In this paper, we discuss the core differences between LTE and Wi-Fi, which lead to significant coexistence issues. We verify and showcase the problem by analyzing the performance degradation of Wi-Fi, when a traditional LTE network is co-located and operates in the same unlicensed frequency without any coexistence mechanism. The experiments are performed using open- source LTE and Wi-Fi implementations on real equipment in a fully controlled wireless environment. We conclude with showing the need for coexistence mechanisms, following the work that is being done within the standardization activities.