Full-Duplex MAC Protocol for Wi-Fi/LTE-U Coexistence Networks

Long-term evolution in unlicensed band (LTE-U) has been an increasing interest for exploiting more spectrum resources. However, the spectrum sharing poses a significant challenge especially regarding the coexistence between LTE-U and Wi-Fi systems. In case of LTE-U acquires the unlicensed spectrum by sharing with the Wi-Fi system, the performance of the Wi-Fi system will be degraded. How to protect Wi-Fi communications and to achieve harmonious coexistence need to be addressed. In this paper, a listen-and-talk access mechanism featuring carrier sensing medium access/collision detection (CSMA/CD) for Wi-Fi is introduced into the LTE-U/Wi-Fi coexistence networks. Specifically, Wi-Fi user can transmit and sense simultaneously by leveraging full-duplex (FD) techniques to avoid long collision and improve spectrum utilization on unlicensed band. In addition, we analyze the system throughput with regard to false alarm and miss detection which are existence due to the residual self-interference (RSI). We further investigate the fairness between Wi-Fi and LTE-U, and for Wi-Fi traffic protection we derive the constriction of false alarm and miss detection. Based on the fairness-throughput trade off, we propose a FD/HD mode switching scheme. Finally, simulation results are conducted using ns-2 simulator, which verify the analysis of throughput in LTE-U/Wi-Fi coexistence networks.