Impact of changing energy detection thresholds on fair coexistence of Wi-Fi and LTE in the unlicensed spectrum

Abstract

The exponential increase in the number of mobile devices in use today has led to a commensurate increase in the demands on both cellular and Wi-Fi infrastructure, thus requiring that both licensed (cellular) and unlicensed (Wi-Fi) spectrum be utilized as efficiently as possible. One solution being actively pursued by industry is for cellular systems to use the unlicensed spectrum in addition to the licensed spectrum, which would require fair coexistence with Wi-Fi in the unlicensed spectrum. As per the IEEE 802.11 standard, Wi-Fi uses an energy detection (ED) threshold of −62 dBm when Long Term Evolution-Licensed Assisted Access (LTE-LAA) and/or Long Term Evolution Un-Licensed (LTE-U) nodes are deployed close by, whereas the LTE-LAA specification recommends that LTE-LAA detect Wi-Fi at −72 dBm. In our work, we evaluate the effect of this asymmetry in the ED threshold on coexistence between the two systems. We develop a coexistence simulator in ns-3 and vary both the Wi-Fi and LTE energy detection thresholds and demonstrate that lowering the Wi-Fi ED threshold from −62 dBm improves performance for both Wi-Fi and LTE-LAA. Prior work has mostly focused on determining the ED threshold that should be used by LTE-LAA/LTE-U. As far as we are aware, this is the first result that demonstrates that lowering the Wi-Fi ED threshold improves performance for both systems. The conclusion is that if Wi-Fi treats LTE-LAA/LTE-U as it would an overlapping Wi-Fi, coexistence performance improves compared to the current assumption that Wi-Fi treats LTE-LAA/LTE-U as noise.