SDR-Based Experiments for LTE-LAA Based Coexistence Systems with Improved Design

To enhance spectrum efficiency in next generation heterogeneous wireless systems, it is important to improve shared spectrum usage between unlicensed long-term evolution (LTE) systems, such as the license-assisted access (LAA), and legacy systems, such as wireless local area networks (WLANs). LTE-LAA uses listen-before-talk (LBT) schemes to enhance coexistence performance. However, available LAA-LBT schemes may incur several problems, such as a slot-jamming effect and a significant slot boundary tracking error, leading to degraded performance. In this paper, we develop an LBT scheme with improved design and software-defined radio (SDR)-based experimental procedure for a performance validation. We program the improved LBT algorithm in the SDR field-programmable gate array (FPGA), and compare the results with the original LBT algorithm. This work also presents an automated testing technique and new SDR functions that modify the LAA parameters in realtime (such as backoff idle slot durations). The experiment results confirm the predicted slot-jamming effect, and show that our improved design enhances LAA throughput. These results provide not only a more robust LAA-LBT design, but also a new method of SDR programming and testing, and insight into the coexistence performance of heterogeneous systems.