基于重复和重传的窄带物联网覆盖增强分析

Analysis of Narrow-Band IoT Coverage Enhancement Based on Repetition and Retransmission

在窄带物联网(NB-IoT)中,重复和重传能增强覆盖能力.针对随机部署的NB-IoT终端和基站,分析基于重复和重传的覆盖增强性能,导出了基站对前导码的检测概率、终端采用前导码重复传输时的检测概率和基于多频段多信道时隙ALOHA的冲突概率,分析了终端对信道的竞争成功概率、随机接入成功率和平均接入时延,针对NB-IoT划分的3个覆盖类别,对重复和重传的性能进行了仿真分析.结果表明,检测概率随前导码重复次数的增加而增加,但重复次数对随机接入成功率的影响不大;随机接入成功率随重传次数和可用信道数量的增加而增加;即使是在极端恶劣的应用场景,平均接入时延也能满足规定的最大可容忍延迟要求.

In NB-IoT(narrow band Internet of things),repetition and retransmission can enhance its coverage.For the randomly deployed terminals and base stations,a preamble detection probability model based on random geometry and a collision probability model based on multi-band and multi-channel slotted ALOHA are established to study the coverage enhancement of repetition and retransmission.The detection probability of the base station for the preamble and the competing success probability of terminal to channel are analyzed.The random access success rate and average access delay of the terminal are derived.A simulation analysis is carried out based on the 3 coverage categories of NB-IoT,and its results show that the detection probability increases with the repetition times,but the repetition times have no significant effect on the random access success rate.The random access success rate increases with the increase of retransmission times and the available channel numbers.The simulation results for the 3 coverage categories of NB-IoT show that the average access delay can meet the maximum tolerable delay requirement even in extremely severe application scenarios.