Unsourced Multiple Access for 6G Massive Machine Type Communications

Unsourced multiple access(UMA)is a multi-access technology for massive,low-power,uncoordinated,and unsourced Machine Type Communication(MTC)networks.It ensures transmission reliability under the premise of high energy efficiency.Based on the analysis of the 6G MTC key performance indicators(KPIs)and scenario characteristics,this paper summarizes its requirements for radio access networks.Following this,the existing multiple access models are analyzed under these standards to determine UMA's advantages for 6G MTC according to its design characteristics.The critical technology of UMA is the design of its multiple-access coding scheme.Therefore,the existing UMA coding schemes from different coding paradigms are further summarized and compared.In particular,this paper comprehensively considers the energy efficiency and computational complexity of these schemes,studies the changes of the above two indexes with the increase of access scale,and considers the trade-off between the two.It is revealed by the above analysis that some guiding rules of UMA coding design.Finally,the open problems and potentials in this field are given for future research.

Resource Allocation for Massive Machine Type Communications in the Finite Blocklength Regime

Massive machine type communications(mMTC)have been regarded as promising applications in the future.One main feature of mMTC is short packet communication.Different from traditional long packet communication,short packet communication suffers from transmission rate degradation and a significant error rate is introduced.In this case,traditional resource allocation scheme for mMTC is no longer applicable.In this paper,we explore resource allocation for cellular-based mMTC in the finite blocklength regime.First,to mitigate the load of the base station(BS),we establish a framework for cellularbased mMTC,where MTCGs reuse the resources of cellular users(CUs),aggregate the packets generated by MTCDs,and forward them to the BS.Next,we adopt short packet theory to obtain the minimum required blocklength of a packet that transmits a certain amount of information.Then,by modeling the process of MTCGs-assisted communication as a queuing process,we derive the closed-form expression of the average delay of all MTCDs.Guided by this,we propose a joint power allocation and spectrum sharing scheme to minimize the average delay.Finally,the simulation results verify the correctness of the theoretical results and show that the proposed scheme can reduce the average delay efficiently.

一种固定位置MTC设备的随机接入改进算法

针对海量机器类通信(Massive Machine Type Communications,mMTC)场景下传统随机接入存在大量前导碰撞问题,提出了一种对终端侧和基站侧的接入改进算法,利用前导标记序列和固定位置随机接入终端的定时提前(Timing Advance,TA)信息,使得基站能合理地确定应该向哪些终端回复随机接入响应消息,避免碰撞终端占用资源发送消息3(Message 3,Msg3),实现前导高效利用。仿真表明,该算法在均匀分布和Beta分布接入模型下均能有效降低前导碰撞概率,提高终端的接入成功率,并且拥有合理的平均接入时延。

Hybrid Multiple Access and Service-Oriented Resource Allocation for Heterogeneous QoS Provisioning in Machine Type Communications

Non-orthogonal multiple access(NOMA)has emerged as one important enabling technology for future wireless communications and services,including machine type communication(MTC).Unfortunately,supporting diverse MTC services and massive connectivity is still challenging due to the very different service requirements,scarce radio resources,limited battery capacity of MTC devices,as well as rapidly changing network conditions.In this paper,a hybrid-multipleaccess(HMA)scheme for service-oriented resource allocation scheme is proposed in supporting diverse MTC services for resource constrained devices and networks.In the proposed scheme,HMA allows MTC devices to choose a suitable type of multiple access technique according to their channel conditions,power constraints,and quality of service(QoS)requirements.To support service-oriented resource allocation,the physical network is firstly sliced into several virtualized networks based on QoS requirements and hardware conditions of MTC devices.A novel utility function integrating network performance and the power consumption in MTC devices is proposed.Furthermore,the resource allocation problem is formulated as an optimization problem to maximize the different utility functions under constraints of user QoS requirements and maximum transmitted power.To improve computational capacity as well as reduce the operational latency,a cloud-edge collaborative scheme is further designed to share the computation loads between the cloud and edge.Simulation results demonstrate the proposed service-oriented resource allocation scheme is effective and illustrate that the proposed hybrid multiple access method provides better performance than NOMA in terms of effective energy efficiency.

机器类型通信中随机接入信道的拥塞控制策略

在基于3GPP长期演进技术的机器类型通信(MTC)应用背景下,针对无线接入网络中随机接入信道的拥塞问题,提出一种改进的拥塞控制策略,MTC器件利用基站广播信息自适应调整各自的接入时间,避免由于大量MTC器件同时发起随机接入而引起接入碰撞的问题,实现基站的负载均衡及信道资源的合理分配。基于最大熵原理证明各MTC器件接入时间的均匀分布是最优分布。仿真实验结果表明,与接入类别限制策略相比,该策略可缓解随机接入信道的拥塞状况,提高MTC器件的随机接入成功率,降低接入时延,从而提升网络整体性能及服务质量。

机器类通信中基于NOMA短编码块传输的高可靠低迟延无线资源分配优化方案

针对机器类通信(MTC)应用场景的业务特征和服务质量(QoS)要求,该文考虑基于非正交多址(NOMA)的MTC中短分组/短编码块传输,探讨MTC中基于NOMA的高可靠低迟延无线资源优化问题。首先,上行传输是基于NOMA的MTC通信的瓶颈,考虑无线蜂窝网络中支持NOMA和高可靠低迟延性能要求,该文建立了上行无线资源优化的系统模型;然后,分析上行传输迟延,导出基于距离的链路可靠性函数;进一步,以迟延、可靠性和带宽为约束下条件,提出一种最大化中心用户和速率的无线资源分配算法,并给出算法的收敛性证明和复杂度分析;最后,实验仿真验证了所提算法的性能优势。

一种基于ACB的机器类通信接入拥塞控制方案

机器类通信(或MTC通信)是指在没有人为干预的情况下实现机器间自主数据通信的技术,大量MTC设备直接连接到当前的蜂窝网络将导致随机接入过载,造成低接入效率和不可容忍的延迟。文中针对这些问题,提出一种面向静态MTC场景的随机接入方案。该方案在ACB基础上,根据网络实时的拥塞情况,对前导资源进行动态分配;并利用TAI(定时提前信息)实现对拥塞设备的识别,降低前导冲突率。仿真结果证明:与其他相关方案相比,该方案保持了较高的资源利用率,并有效降低了时延。

4G网络适应物联网应用的增强设计和实现

为了支持物联网应用,在分析安全性、传输时延、移动性和传输有效性的基础上,指出有必要增强现有的网络架构、更新相关信令流程的问题,并给出终端进入网络,发起数据传输以及终结数据传输场景下的具体消息交互过程,通过分析表明这是一个较优的解决方案,能达到预设的各项指标。

LTE-A网络中基于动态组的有效的身份认证和密钥协商方案

机器类通信(MTC)作为未来移动通信中的通信方法之一,在物联网(Io T)中是一种重要的移动通信方法。当大量MTC设备同时想要访问网络时,每个MTC设备需要执行独立的身份认证,而这会导致网络拥塞。为了解决MTC设备在认证时的网络拥塞问题并提高其密钥协商的安全性,在LTE-A网络中提出了一种基于动态组的有效身份认证和密钥协商方案。该方案基于对称二次多项式,可以同时认证大量的MTC设备,并使这些设备分别与网络建立独立的会话密钥。该方案支持多次组认证,并且提供访问策略的更新。带宽分析表明,相较于基于线性多项式的方案,所提方案传输时的带宽消耗得到了优化:在家庭网络(HN)中的MTC设备与服务网络(SN)之间每次组认证传输带宽减少了132 bit,在HN内MTC设备之间的认证传输带宽减少了18.2%。安全性分析和实验结果表明,该方案在实际的身份认证和会话密钥建立中是安全的,能够有效避免网络中的信令拥塞。

机器类设备基于不同时延需求分组的随机接入方法

针对大规模机器类通信中拥塞导致的时延敏感设备时延高和接入成功率低的问题,提出将小区中设备按时延要求分组,对不同组设备引入不同的退避模型,分析时延敏感设备的时延和吞吐量,按照不同组中设备的时延需求动态分配前导数目,同时通过调整接入类限制因子实现吞吐量的优化。仿真结果表明,在给定时延敏感设备的时延限制条件时,与统一退避的机制对比,所提分组机制的时延敏感设备能够满足时延要求,并且提高了接入效率。

一种基于双队列模型的分布式MTD接入方法

机器类型通信(Machine Type Communication,MTC)在5G场景中的应用比例大幅增长。这一类型通信的主要目的是在尽可能减少人工干预的情况下,实现机器类型设备(Machine Type Device,MTD)之间的自主通信。在大规模机器类型通信(massive Machine Type Communication,m MTC)场景中,随机接入(Random Access,RA)冲突是导致网络性能较差的关键因素。为了减轻RA阶段的MTD冲突,提出一种基于双队列分析模型的分布式接入控制方法。相较于中心式控制方法,分布式方法可以明显降低信令开销。此外,仿真表明,提出的方法在系统中设备数量较为稳定时具有更高的吞吐量。