Power-Domain Collision-Tolerant Random Access Method with Auxiliary Beam for Satellite Internet of Things:A New Solution

There are numerous terminals in the satellite Internet of Things(IoT).To save cost and reduce power consumption,the system needs terminals to catch the characteristics of low power consumption and light control.The regular random access(RA)protocols may generate large amounts of collisions,which degrade the system throughout severally.The near-far effect and power control technologies are not applicable in capture effect to obtain power difference,resulting in the collisions that cannot be separated.In fact,the optimal design at the receiving end can also realize the condition of packet power domain separation,but there are few relevant researches.In this paper,an auxiliary beamforming scheme is proposed for power domain signal separation.It adds an auxiliary reception beam based on the conventional beam,utilizing the correlation of packets in time-frequency domain between the main and auxiliary beam to complete signal separation.The roll-off belt of auxiliary beam is used to create the carrier-to-noise ratio(CNR)difference.This paper uses the genetic algorithm to optimize the auxiliary beam direction.Simulation results show that the proposed scheme outperforms slotted ALOHA(SA)in terms of system throughput per-formance and without bringing terminals additional control burden.

Ultra reliability and massive connectivity provision in integrated internet of military things(IoMT)based on tactical datalink

One of the major challenges arising in internet of military things(IoMT)is accommodating massive connectivity while providing guaranteed quality of service(QoS)in terms of ultra-high reliability.In this regard,this paper presents a class of code-domain nonorthogonal multiple accesses(NOMAs)for uplink ultra reliable networking of massive IoMT based on tactical datalink such as Link-16 and joint tactical information distribution system(JTIDS).In the considered scenario,a satellite equipped with Nr antennas servers K devices including vehicles,drones,ships,sensors,handset radios,etc.Nonorthogonal coded modulation,a special form of multiple input multiple output(MIMO)-NOMA is proposed.The discussion starts with evaluating the output signal to interference-plus-noise(SINR)of receiver filter,leading to the unveiling of a closed-form expression for overloading systems as the number of users is significantly larger than the number of devices admitted such that massive connectivity is rendered.The expression allows for the development of simple yet successful interference suppression based on power allocation and phase shaping techniques that maximizes the sum rate since it is equivalent to fixed-point programming as can be proved.The proposed design is exemplified by nonlinear modulation schemes such as minimum shift keying(MSK)and Gaussian MSK(GMSK),two pivotal modulation formats in IoMT standards such as Link-16 and JITDS.Numerical results show that near capacity performance is offered.Fortunately,the performance is obtained using simple forward error corrections(FECs)of higher coding rate than existing schemes do,while the transmit power is reduced by 6 dB.The proposed design finds wide applications not only in IoMT but also in deep space communications,where ultra reliability and massive connectivity is a keen concern.

Optimization of the Internet of Remote Things Data Acquisition Based on Satellite UAV Integrated Network

In order to achieve dependable and efficient data acquisition and transmission in the Internet of Remote Things(IoRT),we investigate the optimization scheme of IoRT data acquisition under the unmanned aerial vehicle(UAV)-low earth orbit(LEO)satellite integrated space-air-ground network,in which the UAV acquires data from massive Internet of Things(IoT)devices in special scenarios.To combine with the actual scenario,we consider two different data types,that is,delay-sensitive data and delay-tolerant data,the transmission mode is accordingly divided into two types.For delay-sensitive data,the data will be transmitted via the LEO satellite relay to the data center(DC)in real-time.For delay-tolerant data,the UAV will store and carry the data until the acquisition is completed,and then return to DC.Due to nonconvexity and complexity of the formulated problem,a multi-dimensional optimization Rate Demand based Joint Optimization(RDJO)algorithm is proposed.The algorithm first uses successive convex approximation(SCA)technology to solve the non-convexity,and then based on the block coordinate descent(BCD)method,the data acquisition efficiency is maximized by jointly optimizing UAV deployment,the bandwidth allocation of IoRT devices,and the transmission power of the UAV.Finally,the proposed RDJO algorithm is compared with the conventional algorithms.Simulation consequences demonstrate that the efficiency of IoRT data acquisition can be greatly improved by multi-parameter optimization of the bandwidth allocation,UAV deployment and the transmission power.

A Novel Orthogonal LoRa Multiple Access Algorithm for Satellite Internet of Things

In recent years,LoRa has been extensively researched in the satellite Internet of Things(IoT).However,the multiple access technology of LoRa is still one of the bottlenecks of satellite IoT.To improve the multiple access performance of LoRa satellite IoT,based on the orthogonality of LoRa symbols in the fractional domain,this paper proposes a low complexity Orthogonal LoRa Multiple Access(OLMA)algorithm for multiple LoRa users occupying the same frequency bandwidth.The algorithm introduces the address code to divide the fractional bandwidth into multiple parts,and the OLMA users with different address codes occupy different parts to transmit the information code,thus avoiding mutual interference caused by collisions in the same frequency bandwidth.The multiple access capability of OLMA can be flexibly configured only by simply adjusting the length of the address code according to the actual application requirements of data transmission.Theoretical analysis and simulation results show that the OLMA algorithm can greatly improve the multiple access capability and the total transmission bit rate of LoRa IoT without changing the existing LoRa modulation parameters and process.

Application research of narrow band Internet of things buoy and surface hydrodynamics monitoring

This paper applies the narrow band Internet of things communication technology to develop a wireless network equipment and communication system, which can quickly set up a network with a radius of 100 km on water surface. A disposable micro buoy based on narrow-band Internet of things and Beidou positioning function is also developed and used to collect surface hydrodynamic data online. In addition, a web-based public service platform is designed for the analysis and visualization of the data collected by buoys. Combined with the satellite remote sensing data, the study carries a series of marine experiments and studies such as sediment deposition tracking and garbage floating tracking.

Satellite Internet of Things:challenges,solutions,and development trends

Satellite Internet of Things(IoT)is a promising way to provide seamless coverage to a massive number of devices all over the world,especially in remote areas not covered by cellular networks,e.g.,forests,oceans,mountains,and deserts.In general,satellite IoT networks take low Earth orbit(LEO)satellites as access points,which solves the problem of wide coverage,but leads to many challenging issues.We first give an overview of satellite IoT,with an emphasis on revealing the characteristics of IoT services.Then,the challenging issues of satellite IoT,i.e.,massive connectivity,wide coverage,high mobility,low power,and stringent delay,are analyzed in detail.Furthermore,the possible solutions to these challenges are provided.In particular,new massive access protocols and techniques are designed according to the characteristics and requirements of satellite IoT.Finally,we discuss several development trends of satellite IoT to stimulate and encourage further research in such a broad area.

A Query-Based Greedy Approach for Authentic Influencer Discovery in SIoT

The authors propose an informed search greedy approach that efficiently identifies the influencer nodes in the social Internet of Things with the ability to provide legitimate information.Primarily,the proposed approach minimizes the network size and eliminates undesirable connections.For that,the proposed approach ranks each of the nodes and prioritizes them to identify an authentic influencer.Therefore,the proposed approach discards the nodes having a rank(α)lesser than 0.5 to reduce the network complexity.αis the variable value represents the rank of each node that varies between 0 to 1.Node with the higher value ofαgets the higher priority and vice versa.The threshold valueα=0.5 defined by the authors with respect to their network pruning requirements that can be vary with respect to other research problems.Finally,the algorithm in the proposed approach traverses the trimmed network to identify the authentic node to obtain the desired information.The performance of the proposed method is evaluated in terms of time complexity and accuracy by executing the algorithm on both the original and pruned networks.Experimental results show that the approach identifies authentic influencers on a resultant network in significantly less time than in the original network.Moreover,the accuracy of the proposed approach in identifying the influencer node is significantly higher than that of the original network.Furthermore,the comparison of the proposed approach with the existing approaches demonstrates its efficiency in terms of time consumption and network traversal through the minimum number of hops.

业务驱动的低轨卫星物联网终端模态切换方法

针对低轨卫星物联网场景下基于窄带物联网(narrow band Internet of Things,NB-IoT)体制的物联终端大尺度地理范围内多场景应用业务时延和终端功耗需求动态变化问题,提出一种利用马尔可夫链模型评估NB-IoT终端在扩展不连续接收(extended discontinuous reception,eDRX)和节能模式(power saving mode,PSM)下的时延功耗的方法,建立了以下行业务延迟和终端功耗为优化目标的多目标优化问题。在信关站利用终端历史业务数据信息离线训练基于支持向量机(support vector machine,SVM)的时延功耗的回归预测模型,以回归预测模型作为非支配排序遗传算法(non-dominated sorting genetic algorithms-II,NSGA-II)的目标函数,得到多目标优化问题的Pareto前沿解集,进一步从Pareto前沿解集中选择满足当前应用时延功耗需求的工作状态定时器参数值,在线配置终端。仿真结果表明,相比于传统的地面物联网终端固定式定时器参数配置方法,所提出的业务驱动的定时器参数配置方法在终端动态多场景应用下能够更好地满足业务时延和终端功耗需求。

卫星物联网中面向多类型任务的计算卸载策略

边缘计算与卫星物联网相融合,可以将本地物联网设备产生的任务在靠近边缘端进行处理,极大地缓解了本地物联网设备的计算压力。然而,鉴于卫星物联网中计算任务具有多样性,由于任务特性不同需求也不同,针对每一种任务类型部署一套计算卸载策略会导致计算资源的浪费。此外,由于卫星物联网中计算任务产生具有随机性,如果仅考虑系统短期优化会导致计算设备的计算资源利用不足,进一步导致任务处理时延的增加。为解决上述问题,提出了一种基于DQN(deep Q-network)多类型任务计算卸载策略,该策略引入排队论以最小化长期系统任务处理平均时延,并且为提升模型训练结果,在训练阶段重新设计了探索机制。最后,大量仿真结果表明,与其他卸载策略相比,所提策略能有效降低系统任务处理的平均时延。

卫星物联网中联合资源分配的边缘计算卸载策略

卫星物联网通过引入边缘计算技术将计算能力下沉至靠近用户的边缘服务器上,使用户的服务质量得到了提升.然而计算资源有限的边缘服务器在面对大量的突发卸载任务时可能会出现过载的情况,导致任务的处理时延增加.本文将上述问题转化为马尔可夫决策过程下的最优策略问题,提出了一种基于D 3PG(Dueling Double Deterministic Policy Gradients)的联合资源分配的边缘计算卸载算法.该算法利用Double Q-learning思想和Dueling架构重新设计了DDPG(Deep Deterministic Policy Gradients)算法中的价值网络,以提高计算卸载决策的准确性.仿真结果表明,与传统的算法相比,该算法能有效降低系统的平均时延和能量消耗,提高任务的完成率.

卫星物联网中基于能量感知的自适应节能路由策略

随着5G技术的发展和6G技术的研究,低轨卫星网络在卫星物联网中的地位越发重要,而作为网络核心技术的路由策略仍面临一些挑战。本文针对低轨卫星网络拓扑结构动态变化、链路的不连续性、卫星能量供应受限等问题,为了及时感知星间链路状态和卫星的能量并选择正确的路由,将卫星物联网中的路由选择问题转化为马尔可夫决策过程下的最优策略问题,提出一种基于Dueling DQN(Dueling Deep Q Network)的自适应节能路由算法。该算法通过改进DQN中神经网络的架构,大幅度地提升了学习的效果。仿真结果表明,与传统的DQN算法相比,该算法能有效降低系统能耗,均衡网络负载,提高网络吞吐量。

基于SIRM算法的卫星结构板智能化生产管控系统设计

针对物联网技术在智能制造系统中的应用,通过在卫星结构研制设计过程中应用物联网标识和感知技术实现智能化生产管控.分析卫星结构研制流程中实物、信息的操作现状,提出了一种SIMR(Snapshot Integration Multipath Routing)路由算法的卫星研制流程自主感知优化技术,保证流量传输均衡和信息快速回传,解决卫星研制实物流与信息流难以深度融合的问题.围绕卫星零件、装配体、电子标签等实物定义了智能化生产管控系统,将系统分解为实物操作序列与数据操作序列,进而给出了基于物联网的卫星结构智能化生产管控系统架构,明确了本方法在卫星结构板成形生产和装配系统管控环节的应用模式,为提升卫星结构实物状态管控与全流程研制能力提供了一种可行的方法.

面向卫星物联网的柔性多址接入技术

基于时隙ALOHA(S-ALOHA)的免授权上行随机接入能够显著降低卫星物联网(IoT)中的接入时延和复杂度。然而,随着物联网用户数量的增加,S-ALOHA碰撞概率会显著增加,从而影响系统性能。该文针对卫星物联网中存在海量设备上行接入的场景,专注于研究物联网终端的功率资源控制,以实现最大化系统和速率的目标。具体而言,该文提出基于S-ALOHA的柔性多址接入。当系统中存在碰撞时,采用非正交多址技术进行传输,从而避免了用户信息反复重传的问题,降低了传输时延。为了在终端功率受限的情况下实现系统和速率的最大化,该文将序列决策问题建模为马尔可夫决策过程,并采用优势演员-评论家算法(A2C)进行求解。仿真结果表明,所提出的柔性多址接入技术能够在海量物联网终端的场景下有效保证终端的接入成功率。同时,基于A2C的资源分配算法相较于传统的资源分配算法表现更为优越。

卫星物联网中多域联合活跃用户辨识方法

在卫星物联网上行免授权接入场景下,用户直接将数据发送给卫星,不需要进行动态资源分配,这将导致接收端难以事先区分活跃用户。为恢复传输数据,需进行活跃用户检测(AUD)。目前,多使用码域方法进行活跃用户辨识,但物联网密度远超移动通信用户,仅依靠码域辨识会导致地址码维度激增,降低帧效率,并且较多采集类与监测类物联网终端自身能力弱,无法实现自身位置的上报,导致这一维接入辅助信息的缺失,不利于活跃用户检测的性能提升。本文面向未来星载相控阵发展趋势,引入空域辨识思想,通过空域与码域的级联辨识,采用多域联合方法进行活跃用户检测。仿真结果表明,本文方法能够提升地址码冲突时的辨识能力。

面向高吞吐量的NB‒IoT低轨卫星物联网资源调度

窄带物联网(NB-IoT)作为一种低功耗广域网技术,专门设计用于连接大量低功耗设备。基于该技术的低轨卫星物联网有着较低的传输损耗和时延,并且可以通过星座方式对地球实现无缝覆盖。然而,低轨卫星具有高度动态性,并且面临来自不同用户的QoS需求,这些因素使得现有资源调度算法的吞吐量性能受到了极大的影响。针对这些挑战,本文在海量物联网用户请求无线资源且时频资源有限的场景下,综合考虑卫星信道特性、不同用户间的可靠性与时延要求以及卫星高动态性引起的差分多普勒等因素,提出了一种面向高吞吐量的NB-IoT低轨卫星物联网资源调度算法。仿真结果表明,相比现有方法,提出的资源调度算法在系统吞吐量方面表现出显著的性能提升。

一种基于地面和卫星物联网融合的智慧水利系统设计

水利信息化是水利高质量发展的重要途径之一,而通信设备和通信网络是智慧水利中不可缺少部分。通过智慧水利需求分析,文章提出了一种卫星和地面物联网融合的水利监测系统。水利信息通过卫星或地面网络传递到应用中心进行融合处理,然后转入相应的业务系统。文中给出了多模终端的国产化设计方案及优化的节能流程。

Help from space:grant-free massive access for satellite-based IoT in the 6G era

The Sixth-Generation(6G)standard for wireless communications is expected to realize ubiquitous coverage for massive Internet of Things(IoT)networks by 2030.Satellite-based communications are recognized as a highly promising technical enabler to satisfy IoT service requirements in the 6G era.This study analyzes multiple access technologies,which are essential for the effective deployment of satellite-based IoT.First,we thoroughly investigate the existing research related to massive access,including information-theory considerations as well as Non-Orthogonal Multiple Access(NOMA)and Random Access(RA)technologies.Then,we explore the influence of the satellite transmission environment on multiple access technologies.Based on this study,a Non-orthogonal Massive Grant-Free Access(NoMaGFA)scheme,which reaps the joint benefits of RA and NOMA,is proposed for asynchronous transmissions in satellite-based IoT to achieve improved system throughput and enhance the system robustness under varying traffics.Finally,we identify some important and interesting future developments for satellite-based IoT,including waveform design,transceiver design,resource allocation,and artificial intelligence-enhanced design.

Analysis and Suggestions on the Latest Trend of“BDS+”Application Development

The indigenous developed global BeiDou Navigation System(BDS-3)was formally commissioned,marking the completion of the three-step BDS development strategy,and a new era for BDS to better serve people from all walks of life.In this paper,the recent progress and main characteristics of BDS technology fusion and industry integration are analyzed.The discussion on the latest development on"BDS+"application starts from"BDS+Technology"and"BDS+Industry",through to the future prospective BDS applications.

RIS辅助卫星物联网中基于压缩感知的SCMA信号重构

卫星物联网是未来6G网络重要组成部分,在地面部署可重构智能反射面(Reconfigurable Intelligence Surface,RIS)则能进一步增强天地之间信号的传输能力;然而海量设备的接入和检测,以及RIS的引入带来的较高复杂度,给系统设计与实现带来挑战。针对卫星物联网设备和业务稀疏特性,本文提出了一种基于压缩感知的信号重构算法,旨在提高系统的接入用户数和检测成功率,同时降低检测的复杂度。首先,介绍了RIS辅助的卫星物联网系统架构,构建了天地信道模型和星上接收信号模型。然后考虑到卫星物联网地面终端的稀疏性和业务的稀疏性,结合稀疏码分多址(Sparse Code Multiple Access,SCMA)和压缩感知的信号处理方法,通过合理设计SCMA中的稀疏码字,将多用户检测转化为压缩感知理论中的信号重构。最后提出了一种演进的近似消息传播算法(Evolved Approximate Message-Passing,EAMP)来实现压缩感知中的信号重构。仿真结果表明,RIS辅助的SCMA系统与功率域的非正交多址接入技术相比可以提高系统的吞吐量性能,同时EAMP算法相比传统的SIC算法具有更高的正确检测概率和更低的算法复杂度。

卫星物联网混合随机接入技术

在卫星物联网(IoT)场景中,随着终端数量不断增加,频谱资源日益紧张。传统的随机接入技术频谱利用率较低,使得传统随机接入协议不适用于未来卫星IoT的高并发业务需求。同时,卫星通信链路长,开放性强,难以保证特种终端信号的安全性。对此,本文提出一种适用于卫星IoT的混合随机接入方案。该方案引入重叠传输的容量提升与安全性优势,利用扩频码对瞬时功率谱密度的控制能力,构造功率域非正交接入条件,并通过接收端的迭代分离实现稳健接收。对本文所提方案的吞吐量性能进行闭式解推导分析与计算机仿真,结果表明,与传统的随机接入协议相比,所提方案可提高系统吞吐量。同时,相较于常用信号隐藏方法,所提方法利用常规接入数据包的功率优势,强化了波形隐藏效果,提升了特种信息接入的安全性。