Design of Multi-Carrier LBT for LAA&WiFi Coexistence in Unlicensed Spectrum

To relieve the shortage problem of licensed spectrum, the aggregation of licensed and unlicensed carriers has emerged as an attractive solution for opportunistically increasing the throughput of LTE systems while enhancing the utilization of unlicensed spectrum. As one of the representative aggregation technologies, LAA is in favor of the harmonious coexistence with WiFi systems by leveraging the LBT mechanism and different pre-defined access priorities. In this article, we present a general overview of the attractive benefits and technical challenges for aggregating licensed carriers with unlicensed carriers. We then introduce some fundamental features of the LBT based LAA, including transmission modes, ED threshold, random backoff within the contention window, and access priority classes. Under multiple unlicensed channels, we propose two novel multi-carrier LBT mechanisms to improve the transmission behavior and coexistence performance of LAA and WiFi. It is verified in terms of successful transmission probability and carrier utilization rate that two proposed multi-carrier LBT mechanisms can achieve much better performance than the conventional counterpart using random carrier selection.