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.

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.

From Earth to Space:A First Deployment of 5G Core Network on Satellite

Recent developments in the aerospace industry have led to a dramatic reduction in the manufacturing and launch costs of low Earth orbit satellites.The new trend enables the paradigm shift of satelliteterrestrial integrated networks with global coverage.In particular,the integration of 5G communication systems and satellites has the potential to restructure nextgeneration mobile networks.By leveraging the network function virtualization and network slicing,the satellite 5G core networks will facilitate the coordination and management of network functions in satellite-terrestrial integrated networks.We are the first to deploy a 5G core network on a real-world satellite to investigate its feasibility.We conducted experiments to validate the satellite 5G core network functions.The validated procedures include registration and session setup procedures.The results show that the satellite 5G core network can function normally and generate correct signaling.

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.

Information acquisition technology for small hydropower stations in remote areas based on high-and low-orbit satellites

With a lack of coverage in private and public power communication networks,especially for collection of information from hydropower stations in remote areas,communication coverage is a significant issue.Satellite communication provides a large coverage area suitable for a variety of services and is less affected by geographical factors;moreover,the costs are independent of the communication distance.This study investigates information acquisition technology for small hydropower stations in remote areas using high-and low-orbit satellites.The information collection needs of small hydropower stations in remote areas are analyzed,and an information acquisition system is designed using high-and low-orbit satellites.For network security protection,network anomaly detection technology based on a support vector machine algorithm is proposed.The effectiveness of information collection was evaluated and verified for small hydropower plants in remote areas.The system provides technical support for“full coverage,full collection,and full monitoring”of the measurement automation information acquisition system.

Non-Orthogonal Multi-Carrier Transmission for Internet via Satellite

As the important complementary to terrestrial mobile communications, Internet via satellite can extend the coverage of communication and improve the continuity of data services. To build a space-terrestrial integrated communication system is the inevitable trend in the future. Taking into account combination of 5th generation(5G) terrestrial mobile communication system and satellite communication system, it is necessary to evaluate the promising 5G air interface waveform which can be adopted by satellite. In this paper, several non-orthogonal multi-carrier transmission schemes are evaluated and generalized frequency division multiplexing(GFDM) is advised as potential scheme of space-terrestrial integrated communication system. After the overview of GFDM, the implementation of GFDM transceiver is discussed respectively in time-domain and in frequency-domain. By deriving and comparing implementation complexity, GFDM modulation in time-domain is more suitable for satellite communication system. Then the properties of demodulation algorithms are specified. Based on designed pilot subcarriers, a new improved receiving algorithm is proposed in the end of the paper. The improved algorithm solves the problem of inter subcarriers interference(ICI) in matched filtering(MF) receiver and improves the re-ceiving symbol error rate(SER) obviously. The simulation and analysis prove that the proposed algorithm is effective.

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.

The Teaching Mode Research of“Internet Plus Flipped Class”——Taking the Course of Satellite Meteorology as Example

Based on the existing disadvantages of traditional teaching mode of Satellite Meteorology course in Chengdu University of Information Technology and the new teaching mode overview of“Internet Plus flipped class”,this paper is mainly to construct flipped class teaching mode of Satellite Meteorology under the background of“Internet Plus”in Chengdu University of Information Technology.Through the Internet,it also tries to integrate this teaching mode into flipped class before class,in class,after class,which means to provide a new thought for the teaching of this course in colleges and universities.

System Integration of Terrestrial Mobile Communication and Satellite Communication——The Trends, Challenges and Key Technologies in B5G and 6G

Mobile communication standards have been developed into a new era of B5G and 6G.In recent years,low earth orbit(LEO)satellites and space Internet have become hot topics.The integrated satellite and terrestrial systems have been widely discussed by industries and academics,and even are expected to be applied in those huge constellations in construction.This paper points out the trends of two stages towards system integration of the terrestrial mobile communication and the satellite communications:to be compatible with 5G,and to be integrated within 6G.Based on analysis of the challenges of both stages,key technologies are thereafter analyzed in detail,covering both air interface currently discussed in 3GPP for B5G and also novel network architecture and related transmission technologies toward future 6G.

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.

Steady-State Performance Evaluation of Linux TCPs versus TCP Wave over Leaky Satellite Links

Internet access is becoming even more heterogeneous, including different wireless backhauling links, with Ka-band satellites as a possible alternative. Since communication path is unknown a priori, adoption of PEP solutions to optimize TCP performance over satellite is discouraged to allow dynamic network reconfigurations. To opposite, an endto-end TCP performance evaluation on such a challenging scenario, with possible large latency and transmission losses, is herein considered of paramount importance. Several TCP variants exist to tackle different aspects of communication networks. In Linux, the different TCP congestion control schemes differ from the theoretical formulations and RFC specifications, introducing a varying set of optimizations and options. This aspect makes difficult to identify a standard/reference TCP version for the proposed scenario, while testing with the real protocol stacks is deemed necessary to obtain consistent results. In addition, an innovative end-to-end TCP, namely TCP Wave, is introduced to replace the traditional window-based transmission with a burst-based strategy, representing a valid alternative to Linux TCP. To offer a fair, realistic and comprehensive evaluation, we configured a simulation setup where different Linux TCPs can be run within ns-3 network simulator and compared with TCP Wave.

The Future of Broadband Connectivity: Terrestrial Networks vs Satellite Constellations

This paper looks at the landscape of broadband connectivity as consumers welcome disruptive newcomers, the satellite service providers, into the telecommunication and internet ecosystem. It highlights the developments that have made it possible for satellites communication to form a competitive alternative for terrestrial broadband internet services. We motivate discussions on ways and approaches to ensure terrestrial mobile operators construct effective strategy in integrating and working with the newcomers for interconnecting their terrestrial nodes with those of the satellite service providers. We discuss some technology and business perspectives for a healthy co-existence, and postulate that customers’ finances (price consideration) and perception of quality of experience and satisfaction may be the battleground for satellites and terrestrial service providers. Finally, it is concluded that, in the history of human endeavor, smart and effective cooperation has always been the best strategy to fight extinction.

Topology and Position Aware Overlay Network Construction Protocol for Augmentation Information of Satellite Navigation System

It is an effective method to broadcast the augmentation information of satellite navigation system using GEO technology.However,it becomes difficult to receive GEO signal in some special situation,for example in cities or canyons,in which the signal will be sheltered by big buildings or mountains.In order to solve this problem,an Internet-based broadcast network has been proposed to utilize the infrastructure of the Internet to broadcast the augmentation information of satellite navigation system,which is based on application-layer multicast protocols.In this paper,a topology and position aware overlay network construction protocol is proposed to build the network for augmentation information of satellite navigation system.Simulation results show that the new algorithm is able to achieve better performance in terms of delay,depth and degree utilization.

卫星互联网支撑跨域无人集群作战

跨域无人集群作为一种颠覆性的未来全新作战模式,其作战效能的发挥极大地受限于通信组网能力。近年来,卫星互联网凭借其广覆盖、低延时、高宽带及低成本等技术优势,在全球快速发展,是进一步发展跨域无人集群作战模式的关键。文中针对未来水下无人系统的发展趋势和现实需求,介绍了卫星互联网的发展、技术优势以及跨域无人集群的作战概念,深入分析了卫星互联网支撑跨域无人集群作战的优势,提出了结合卫星互联网技术与空域、海面、水下作战域无人集群相结合的空海跨域无人集群作战网络,并综合分析给出了技术架构,可为未来跨域无人集群作战研究提供参考。

全球卫星互联网关键技术竞争态势与启示

当前,全球正围绕卫星互联网系统建设开展新一轮太空竞赛,其中低轨卫星通信是继卫星导航之后,世界强国在天基信息系统领域的下一个争夺焦点。研究卫星互联网关键技术在推动卫星和通信技术进步、应对全球挑战、引领未来发展等方面具有重大意义。本文通过构建卫星互联网关键技术体系,检索专利数据,从技术发展趋势、技术竞争主体、技术竞争区域和技术竞争领域等维度综合分析卫星互联网关键技术竞争态势。研究发现,我国卫星互联网发展存在起步较晚、关键技术缺失、产业集群不强、场景应用不足等问题。对此提出发展对策:提前布局未来技术,抢占新兴前沿领域;组建创新联合体,加强关键核心技术攻关;强化产学研深度融合,构建产业生态集群;突出通导遥交叉融合,打造多元化应用场景。

服务天基感知业务的卫星互联网模拟验证系统设计与分析

提出具有遥感、星间星地组网、星载边缘计算功能的低轨卫星与地面云计算中心和天基、临近空间、空中、陆地、海面等各类型终端构成的卫星互联网总体架构,给出包括资源层、虚拟化层、服务层、服务管理层及应用层在内的星载边缘计算功能架构。针对星载计算能力有限、天基网络拓扑高动态等典型特征,在提出星载边缘计算模拟验证系统构建方法的基础上,设计服务天基感知业务的卫星互联网模拟验证系统,开展天基感知信息处理分发试验,并根据不同信息处理与分发方式对网络资源占用和用户服务时延的对比,分析不同能力条件下卫星互联网对天基感知业务服务的能力水平。

基于Logistic模型和SPC算法的关键技术识别与预测——以卫星互联网为例

识别关键技术有助于在制定技术和市场战略布局中获得先发优势,对我国经济发展、国家安全具有重要意义。文中提出一种融合生命周期与主路径分析的关键技术识别方法,是对已有的研究理论和方法的重要补充。首先,检索相关领域专利数据并进行技术划分;然后,综合运用Lo-gistic模型和SPC算法构建技术轨道,识别关键技术;接着,使用显性技术优势指数比较主要国家技术竞争态势;最后,结合关键技术与技术竞争态势绘制技术路线图,识别技术热点与前沿预测。以卫星互联网为例,阐述该方法的应用过程。研究结果表明,该方法能够较为准确识别出该领域关键技术,揭示全球技术竞争态势,有效实现技术热点识别和未来技术预测;识别出的卫星互联网关键技术,能够为国家发展政策制定与相关产业布局提供参考。

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.

面向卫星互联网信号的监测处理平台设计

在低轨卫星互联网迅猛发展的背景下,我国卫星监管机构围绕新型目标开展针对性监测的效果不佳,技术水平亟待提升。基于卫星互联网信号传输架构的研究结果,提出一种面向卫星互联网信号的针对性监测技术框架,设计并实现高速监测处理平台。典型卫星信号经过信号检测、识别、解调译码后,支持比特流级信号分析。实验结果表明,该平台能够实现典型卫星互联网信号监测处理流程并得到相关特征参数,对研制监测设备具有实用意义。