一种应用于5G非授权频段通信的低时延随机接入机制

针对5G非授权频段通信(NR-U)场景，该文提出一种新型的低时延随机接入机制。该机制分别在随机接入回复窗口(RARW)与竞争窗口中加入了信道空闲计时器，来减少UE因在非授权频段进行竞争接入所引起的时延；此外该机制还加入了请求发送/允许发送机制，来解决隐藏节点对随机接入过程的影响。该机制可降低传统机制中由于未考虑非授权频段特性及隐藏节点问题所引起的随机接入时延问题。该文首先对NR-U场景中的传统随机接入机制进行分析并进行问题定位；其次，提出新型随机接入机制的网络实体交互流程，建立新型机制与传统机制中的网络实体交互时序模型；最后以数学推导和仿真的方法对新型机制与传统机制进行对比评估，相关结果显示出新型机制在平均耗时方面的优势。

A Low Latency Random Access Mechanism for 5G New Radio in Unlicensed Spectrum

For the 5G New Radio in Unlicensed (NR-U) spectrum scenario, a novel random access mechanism is proposed, which first adds the channel idle timer in Random Access Response Window (RARW) and contention resolution window to reduce the accessing delay caused by the contention-based accessing and employs the Request To Send/Clear To Send (RTS /CTS) mechanism to address the hidden node issue. The mechanism can alleviate the latency incurred by the legacy mechanism which did not consider the intrinsic attribute of unlicensed band and the hidden node problem. Specifically, the legacy random access mechanism applied to NR-U is analyzed. Then, the detailed elaboration of the network entity interaction sequence defined in novel mechanism is proposed. Finally, the performance evaluation processes are carried out in the way of mathematical modeling and experimental simulation, and the analysis result demonstrates that the novel scheme outperforms the benchmark one in the respect of the average random access delay.