LTE与Wi-Fi共享频谱中下行链路的CCA自适应阈值调整算法

Adaptive Threshold Adjustment of Clear Channel Assessment for Downlink Transmission in LTE and Wi-Fi Spectrum Sharing

随着4G的后续演进和多载波聚合技术的发展,对频谱资源的诉求会越来越多,3GPP协议也在频谱共享方面做了很多的探索和研究。在未授权的载波上进行无线传输前,首先进行了空闲信道评估(Clean Channel Assessment,CCA),以确保未授权频段内其他无线通信设备的正常工作,从而使LAA(License Assisted Access)与其他无线电接入技术和谐共存。在基站承载海量业务的场景下,不合适的CCA阈值会导致基站缓冲区溢出,因此,提出了一种自适应阈值调整方法。该方法通过分析业务负载和传输机会数量,预估LAA吞吐量随阈值变化的趋势,动态调整CCA阈值。通过系统级仿真,在LAA和Wi-Fi共存的场景中,测试验证了所提出的设计方法的有效性。

With the subsequent evolution of 4G and the development of multi-carrier aggregation technology,there will be more and more demands for spectrum resources.3GPP protocol has also done a lot of exploration and research on spectrum sharing.The channel sensing(Clean Channel Assessment,CCA)is required before any transmission on these unlicensed carriers,in order to make sure the harmony co-existence of LAA(License Assisted Access)with other radio access technology in the unlicensed band.An improper CCA threshold may cause buffer overow of some base stations,if the base stations are heavily loaded with the trafcs.Thus,to solve these problems,we propose an adaptive threshold adjustment method for CCA in the LAA down link.Both the load and transmission opportunities are concerned.The trend of the LAA throughput as the threshold varies is obtained,which guides the threshold adjustment.The co-existing between LAA and Wi-Fi is particularly tested.The results from system level simulation conrm the merits of our design.