【作者】 刘婷；

【导师】 张峰；

【作者基本信息】 北京理工大学 ， 信息与通信工程， 2018， 硕士

【摘要】 机器类通信是下一代通信的重要组成部分,也是实现物联网的主要途径,其应用范围广,极大方便了人们的生活。机器类通信设备数量将爆发式增长,然而现有的移动蜂窝通信是为人与人之间的通信设计的,不符合机器类通信的业务特性。本文通过物理信道资源分析、数值推导、系统级仿真等途径,分析了大连接机器类通信和低时延高可靠通信可能存在的问题,并设计相应的技术方案。主要工作和结论如下:首先,对机器类通信进行资源受限分析及传输难点分析。基于LTE的资源配置分析了大连接机器类通信接入过程中的接入资源受限情况,以及接入和调度过程导致的控制信道资源受限情况,并通过系统级仿真验证。同时,针对低时延高可靠通信的小数据包特性,分析小数据包传输的难点和HARQ机制的可行性。其次,为了解决大连接机器类通信接入资源受限问题,设计了一种联合竞争与非竞争的随机接入优化方法和一种分组接入优化方法。在联合竞争与非竞争的接入优化方法中,机器类通信设备在首次接入时采用基于竞争的接入,后续周期性发起非竞争接入。该方法能够避免碰撞、提升接入成功率,所包含的系统帧计数器设计能够在尽少改变信令条件下扩大LTE的系统帧计时范围。分组接入优化方法中基于迭代的分组能够按优先级且无需固定组内用户数情况下分组,该方法能够节省控制信道资源,提升接入成功率。最后,针对低时延高可靠通信,设计了一种小包重复传输方法,以及一种基于组控制信息的下行调度算法。小包重复传输方法减少了HARQ机制的停-等时间,能够在短帧结构下多次重传而不超过时延限制;基于组控制信息的调度算法用一个组控制信息调度多个用户,用户侧采用偏移盲检测解调数据,仿真结果表明该方法大幅降低控制信道资源开销。更多还原

【Abstract】 Machine-type communications is an important component of the next generation communication networks and the main way to enable the Internet of Things.Machine-type communications has great potential in a wide range of applications and brings us great convenience.The number of machine-type communications devices is exploding.However,the current cellular networks are designed for human-to-human communications,which does not match well with the requirements of machine-type communications.This paper analyzes the possible problems of massive machine-type communications and ultra-reliable and low latency communications via physical channel resources analysis,numerical derivation and system level simulation,and proposes corresponding solutions.The main contributions can be summarized as follows:Firstly,we analyze the resource limitation and transmission challenges for machine-type communications.Based on LTE resources assignment,we investigate the level of access resource limitation for massive machine-type communications and the level of control channel resource limitation caused by access and scheduling process.The system level simulator is used for verification.For the transmission of small packets in ultra-reliable and low latency communications,we illustrate the challenges for small-packet transmission and evaluate the feasibility of HARQ.Secondly,to alleviate the access resource limitation,we propose a hybrid contention-based/non-contention-based random access scheme and a group-access optimal scheme.In the hybrid contention-based/non-contentionbased random access scheme,the machine-type communications devices access the network based on contention at the first time.After that,the devices access the network periodically at a non-contention manner.This can avoid contention and increase the access success probability.The counter designed in this scheme expands the range of system frame with less alteration on signaling.The group-access solution provides a grouping way based on iteration process.The grouping way can group the devices in the order of priority without fixing the number of devices.This solution saves the control channel resources and improves the access success probability.Thirdly,for ultra-reliable and low latency communications,we propose a small-packet repetition transmission scheme and a downlink scheduling scheme based on group-DCI.The small-packet repetition transmission approach reduces the stop-wait time in HARQ and supports several repetitions under delay limit with short frame structure.In group-DCI based scheduling algorithm,the base station schedules a group of devices with one group-DCI,the devices recover the data by employing offset blind dection.This scheduling algorithm reduces the control channel overhead obviously.更多还原