LTE-U与WiFi系统在非授权频段共存机制研究

部署长期演进(long-term evolution,LTE)系统到非授权频段,已经被视为一种缓解目前频谱资源短缺的有效方法.当前的主要挑战是LTE与WiFi系统如何在非授权频段和谐共存.为降低系统总冲突概率,提升非授权频谱利用率并保障WiFi系统的传输性能,提出2种接入机制:基于先听后发(listen before talk,LBT)的随机接入机制(LBT-based random access mechanism,LBT-RA)和基于边听边发(listen and talk,LAT)的冲突避免接入机制(LAT-based collisions avoid access mechanism,LAT-CA).LBT-RA机制基于LBT检测发送方式在传输前对信道进行空闲信道评估(clear channel assessment,CCA),如果检测信道空闲,便随机接入可用的非授权频段.LAT-CA机制基于全双工技术的LAT检测发送方式,能实现频谱检测与数据传输的同时进行,降低用户间的冲突概率.仿真结果表明,提出的LBT-RA和LAT-CA机制能有效提升非授权频谱的利用率,并确保非授权频段LTE(LTE-unlicensed,LTE-U)与WiFi系统的和谐共存.

Coexistence mechanism of LTE-U and WiFi systems in the unlicensed spectrum

The deployment of the long-term evolution (LTE) systems in the unlicensed spectrum has been considered as an effective way to alleviate the current shortage problem of spectrum resources. However, the primary challenge is the coexistence between LTE systems and WiFi systems in the unlicensed spectrum. In this paper, we propose two access mechanisms: listening before talking (LBT) based random access mechanism (LBT-RA) and listening and talking (LAT) based collisions avoidance access mechanism (LAT-CA) to reduce the overall collision probabilities and increase the spectrum utilization ratio while ensureing the transmission performance of WiFi systems. LBT-RA is based on LBT detection method, which performs clear channel assessment (CCA) before transmission and could random access the available unlicensed band according to detection results. LAT-CA is based on the LAT detection method of full duplex technology, which could achieve the simultaneous operations of sensing and transmission while reducing the collisions probability of users. Simulation results show that the proposed LBT-RA and LAT-CA mechanism can effectively improve the utilization of the unlicensed spectrum, and ensure the harmonious coexistence of LTE unlicensed (LTE-U) and WiFi systems.