MAC-layer coexistence analysis of LTE and WLAN systems via listen-before-talk

With the congestion and scarcity of available spectrum resources, spectrum sharing between long-term evolution (LTE) and the IEEE 802.11 (aka. WLAN) systems is an ongoing research topic. Considering the LTE license assisted access (LAA) with the listen before talk (LBT) procedure, recent research efforts try to evaluate the performance in several LTE-LBT and WLAN coexistence scenarios. However, the available approaches have not adequately modeled and analyzed general case of LBT (such as Category 4), and the case when there are more than two types of transmissions. In this paper, to fill this technical gap, we implement a systematic modelling and analysis of the media access control (MAC) layer coexisting performance of LTE-LBT and WLAN systems. We consider the coexistence scenario of multiple LTE downlink with multiple WLAN uplink and downlink transmissions. We develop analytical results on time-efficiency throughput, transmission and collision probabilities of LTE and WLAN nodes, and then generalize the result to multiple types of transmissions (e.g., more than three types). To validate the analysis, we implement LBT and WLAN MAC algorithm programming and extensive simulations, which confirm the accuracy of our analysis. Our result shows that replacing WLAN stations with LTE transmitters may, in some cases, significantly degrade the overall throughput, depending on the original efficiencies of WLAN systems and channel access schemes. To address this, we propose a 4-way handshaking channel access scheme for LTE-LBT, which can significantly improve the coexistence performance. These results put new insight into relationship between coexistence performance and MAC parameters of LTE-LBT and WLAN systems, and may aid in the design and optimization of coexistence systems.