Performance Evaluation of LAA-LBT Based LTE and WLAN´s Co-Existence in Unlicensed Spectrum

The license assisted access (LAA) along with listen before talk (LBT) mechanism for access of unlicensed spectrum by LTE is a recent study item of the 3rd Generation Partnership Project (3GPP). The LAA-LBT is expected to be a feature in Release 13 of LTE that will allow mobile operators to utilize the unlicensed spectrum as their secondary carrier for data offloading. However, the unlicensed spectrum is primarily occupied by 802.11 based WLAN devices. Hence, to ensure a fair sharing of this spectrum with WLAN devices, LAA should use a channel access scheme that is compatible with WLANs´ distributed coordination function (DCF). Two such channel access schemes for LAA are under consideration with 3GPP. In this work, we thoroughly evaluate these channel access schemes under various traffic scenarios. We show that the fairness of these schemes largely depends on the signal/energy detection threshold used by the LAA-LBT mechanism. Further, through simulation results, we show that there exists a trade off in selection of the detection threshold such that high sensing threshold results in improved overall network throughput at the cost of WLAN´s performance; whereas, low threshold results in improved WLAN´s performance at the cost of the overall network performance.