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    20 December 2022, Volume 3 Issue 4
    Special Issue: Satellite Internet User Access Control
    Low Orbit Satellite Internet of Things Transmission Technology Based on LoRa
    Zehao LI, Jianpeng MA, Shun ZHANG, Xiao WEI, Jing ZHANG
    2022, 3(4):  2-11.  doi:10.11959/j.issn.2096-8930.2022038
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    As an emerging wide area network technology, LoRa has the characteristics of low power consumption and wide coverage.It has very broad prospects in the field of internet of things applications.In recent years, it has been deployed in countless objects around the world.The advantages of wide coverage of low-orbit satellite networks make it an inevitable technology to achieve global coverage of massive internet of things.Firstly, the basic principles of LoRa technology were expounded.Then the problems existed after the LoRa technology was directly introduced into the low-orbit satellite IoT were analyzed.Finally, a set of LoRa transmission technology suitable for low-orbit satellite IoT was proposed, focused on solved the problem of LoRa frame synchronization under the condition of low-orbit long-distance low-power transmission, and the problem of LoRa demodulation caused by the high-speed movement of satellites due to the Doppler frequency off set.The simulation results showed that the proposed joint synchronization and frequency off set estimation algorithm could obviously improved the synchronization probability and transmission reliability of LoRa technology under the conditions of extremely low SNR and large Doppler frequency shift.

    Resource Allocation of Multi-Satellite Beam Hopping Technology Based on System Capacity Maximization
    Qing SHU, Xiaoning ZHANG, Zesong FEI
    2022, 3(4):  12-21.  doi:10.11959/j.issn.2096-8930.2022039
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    Unlike medium and high earth orbit satellites, LEO satellites have the characteristics of small path loss, low propagation delay and high deployment fl exibility.LEO satellites are widely used in real time services, global internet of things, emergency communication and other fi elds.In order to solved the problems of large diff erences in service demand distribution of terrestrial users and low resource utilization in LEO satellite communication systems, a resource allocation algorithm of LEO multi-satellite beam hopping technology based on convex optimization was proposed, which aimed to maximized the system capacity.For multisatellite beam hopping scenarios in LEO satellite communication system, the beam-hopping technology could fl exibly allocated system resources accorded to user needs.Considered the factor of co-channel interference, the service region division scheme based on load balancing and the inter-satellite resource allocation priority scheme was proposed.In order to improved system capacity and resource utilization, it jointly designed a time and power resource allocation algorithm based on convex optimization.The simulation results showed that the proposed scheme could eff ectively reduced co-channel interference and realized the ondemand allocation of system capacity without causing waste of resources.

    Beamforming Technology of LEO Satellite in Satellite-Terrestrial Integrated Network
    Zhiyong LUO, Ning XIN, Shaohui SUN
    2022, 3(4):  22-30.  doi:10.11959/j.issn.2096-8930.2022040
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    Because of the difference between satellite-ground link and ground propagation loss characteristics, the spectrum effi ciency index of satellite communication system is far lower than that of terrestrial cellular system in the same period.It is of utility to improve spectral effi ciency by realizing effi cient space division multiplexing with multi-beam antennas.The adaptive beamforming and doppler frequency off set compensation scheme in the LEO multi-beam satellite communication scenario was studied.Firstly, a low-complexity hybrid beamforming scheme was designed.Then, aim at the doppler frequency shifts were diff erent between beams due to their pitch angles, a doppler frequency off set pre-compensation scheme for multi-beam systems was proposed.Finally, the eff ectiveness of the algorithm was verifi ed by MATLAB simulation analysis.

    Design and Implementation of Intelligent Anti-Interference for Data Link
    Zhen WU, Jingyu YANG, Shuo WANG, Zhenghuan WANG, Min JIA
    2022, 3(4):  31-44.  doi:10.11959/j.issn.2096-8930.2022041
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    The application scenarios and problems faced by data link communication on hypersonic unmanned aerial vehicles were introduced, and the mainstream jamming style categories, development trends and anti-jamming methods in current data link communication were listed.The design and technical scheme of the intelligent anti-jamming engine was described in detail, and the design of the intelligent anti-jamming engine was discussed from four aspects: the overall scheme, the broadband spectrum perception module, the interference signal recognition module, and the anti-interference decision-making module.The technical approaches of the main key technologies were introduced, the performance of the adopted methods was simulated and tested.The results of the simulation tests were compared and analyzed, and the simulation tests could proved that the methods used could achieved the expected goals, but there were still certain limitations, and the actual engineering and practical eff ects need to be further verifi ed.

    Resource Scheduling Algorithm Based on DQN in Satellite CDN
    Jiaran ZHANG, Yating YANG, Tian SONG
    2022, 3(4):  45-54.  doi:10.11959/j.issn.2096-8930.2022042
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    With the rapid development of space and information fi eld, hot content distribution intensive scenes will become one of the key directions of satellite network application, and satellite content delivery network (CDN) network is an important means to improve the effi ciency of air and space content distribution.In the architecture of satellite CDN network, due to the uneven time and space of business requirements, the scarcity of satellite resources and the insuffi cient adaptability of existing scheduling algorithms, scheduling algorithms for satellite resources are faced with problems such as high resource dimension, many computing states and large amount of computation, which will reduce the accuracy, response speed and computing performance of scheduling decisions.To solve this problem, a resource scheduling algorithm based on Deep Q-Learning (DQN) algorithm was proposed to improved the effi ciency and accuracy of satellite resource scheduling, and intelligently and quickly perceived the resource situation to make scheduling decisions.Firstly, the user requests were classifi ed, and the shortest path set that the satellite could communicated with was calculated according to the time-varying trajectory of the satellite and the resources of the satellite and the ground.After that, the related information of satellites and users was quantifi ed by Markov model modeling, and the optimal CDN storage node of satellites was calculated by DQN algorithm, which achieved the eff ects of reduced user request delay, reduced satellite-ground resource occupancy rate and improved cache hit rate.

    Review of Slice Resource Management Technology in Space-Integrated-Ground Access Network
    Ning HUI, Qian SUN, Yuanyuan WANG, Zongshuai ZHANG, Lin TIAN, Jing ZHANG, Xiao WEI
    2022, 3(4):  55-64.  doi:10.11959/j.issn.2096-8930.2022043
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    With the explosive growth of diff erentiated services, it is urgent to manage wireless spectrum and computing resources on demand dynamically in the sliced access network (RAN) of the space-integrated-ground network.Resulting from that, refi ned and guaranteed qualities of services are achieved.Thus, it is necessary to study the dynamic management of spectrum and computing resources in the sliced RAN of space-air-ground integrated networks.The resource management technologies in sliced RAN of the space-integrated-ground were discussed.The current research status of resource management in the space-integratedground access network was summarized.The future demands of resource management in sliced RAN of the space-integratedground system were analyzed, included the high isolation of wireless spectrum resource, the collaboration of computing resources among space and ground parts, and the real-time heterogeneous resource management in complex sliced RAN of space-air-ground integrated networks.The corresponding key technologies of the three demands were provided.

    Special Issue: Information Transmission Technology for Satellite-Terrestrial Integration
    Detection of 3D Spatial-Temporal Spectrum Opportunity in Satellite-Terrestrial Integrated Network
    Ning YANG, Daoxing GUO
    2022, 3(4):  67-74.  doi:10.11959/j.issn.2096-8930.2022044
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    The detection of 3D spectrum opportunities in the downlink sharing scenario in satellite-terrestrial integrated networks was investigated.First, defined the 3D space-time spectrum opportunities in the satellite-terrestrial integrated networks, and further divided the opportunities into three areas in the spatial domain: the communication area of primary user, the communication protection belt, and the free access area.Then, based on the proposed 3D opportunity model, derived the closed expressions of the detection and false alarm probability at the user-level and the network-level, respectively.In order to further utilized the spatial spectrum opportunity, a power control scheme of the cognitive user was determined through 3D spectrum sensing, i.e., interference constraint (IC).The simulation results demonstrated that the proposed power control scheme could realized the detection of 3D spectrum opportunity.

    Beamforming for Non-Orthogonal Multicast and Unicast Transmissions Based on Rate Splitting in Satellite-Terrestrial Integrated Network
    Bensi ZHANG, Deyi PENG, Yun LI
    2022, 3(4):  75-82.  doi:10.11959/j.issn.2096-8930.2022045
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    A non-orthogonal multicast and unicast transmission scenarios in the satellite-terrestrial integrated networks (STIN was considered), and a system model of joint multi-group multicast and unicast downlink transmitting was constructed.In order to improved the spectral effi ciency of STIN, a beamforming scheme that non-orthogonal transmission based on rate splitting was proposed, where a max-min fair (MMF) beamforming design problem was established to optimized transmit beamforming vector of base station and satellite respectively.And then, considered non-convex constraint caused by variable coupling in the problem, an iterative algorithm based on successive convex approximation to solved the optimization problem was proposed.Simulation results showed that our proposed scheme could improved eff ectively the MMF transmitting rate of the STIN in contrast with the traditional non-rate splitting and layer division multiplexing schemes.

    Multi-Users Dynamic Bandwidth Allocation Technology of SDTN
    Jianxiang CHU, Yin HUANG, Chong WANG, Yunze CAO
    2022, 3(4):  83-91.  doi:10.11959/j.issn.2096-8930.2022046
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    The TT&C and data transmission of spacecraft are divided into two methods: space-based and ground-based.Among them, space-based method has the advantages of global coverage, access at any time, and real-time information return, and have a wide range of application prospects.But it also puts forward certain requirements for the dynamic bandwidth allocation of its multi-spacecraft.Based on the studied of medium-orbit TT&C, data transmission constellation network architecture and multiple access protocols, a dynamic bandwidth allocation algorithm for on-doard multi-beam, multi-spacecraft users, and multi-task priorities for data transmission tasks was proposed.It was very suitable for the on-demand and real-time resource allocation of data transmission requests of multiple spacecraft in the mid-orbit constellation, and could be used as a multiple access protocol model for space-based measurement and control and data transmission access networks.

    Research on HARQ Technology in Low-Orbit Satellite Communication Network
    Runxin ZHANG, Shun ZHANG, Jianpeng MA, Jing ZHANG, Yunfei WU
    2022, 3(4):  92-100.  doi:10.11959/j.issn.2096-8930.2022047
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    How to extend the HARQ technique to made it suitabled for LEO satellite communication network was explored.First the traditional HARQ technology was expounded.Based on this, the HARQ scheme based on low density parity check code (LDPC) and the HARQ scheme based on message group check code (BCC) were studied respectively, the performance of the schemes was analyzed through simulation.Finally, suitable feedback schemes were analyzed for the retransmission units in the HARQ retransmission mechanism, which provided some reference for the research of HARQ technology in LEO satellite communication networks.

    Overview of OTFS Based Channel Estimation Techniques in LEO Satellite Communication
    Xinjie ZHAO, Ziwei LIU, Gengxin ZHANG
    2022, 3(4):  101-106.  doi:10.11959/j.issn.2096-8930.2022048
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    With the development of science and technology and the continuous improvement of related technologies, low earth orbit (LEO) satellite communication has become a hot technology that countries all over the world are chasing.The advantages of orthogonal time frequency spacetechnology can well solve the signal transmission problem of broadband satellite ground link in high moving speed scenarios, which is conducive to the unifi cation of modulation waveforms between satellites and the ground, and the realization of space-based integrated communication.However, its transmission performance is aff ected by the accuracy of channel estimation, and the special modulation makes its channel estimation method diff erent from the traditional technology, so it needs to be studied.The existing mainstream OTFS channel estimation schemes are introduced, and the advantages and disadvantages of each scheme were analyzed, which laied a foundation for subsequent research.

    Implementation Method of GEO and LEO Satellite Tracking Compatible Flat-Plate Antenna
    Jian CHEN, Zhengqian ZHANG, Xinsheng MA, Ting CHAO, Gangtao GUO
    2022, 3(4):  107-112.  doi:10.11959/j.issn.2096-8930.2022049
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    In order to improve the portability, disassembly and usability of the satellite communication antenna products in the fi eld, a GEO and LEO satellite tracking compatible fl at-plate antenna implementation method was proposed, the micro strip array antenna was integrated with the radio frequency channel, and the radio frequency of the antenna was fl at and integrated, combined with the high density multi-layer vertical interconnection technology, the whole machine was small in size, light in weight and low in power consumption, and the tracking control unit could satisfi ed the requirements of GEO Beacon and carrier tracking, also could satisfi ed the LEO analysis and the program guidance tracking.The antenna did not need manual assembly and disassembly, and could be used for satellite communication with onebutton deployment.high-precision tracking and stable communication could be achieved for GEO, MEO and LEO satellite.

Copyright Information
Competent Unit: Ministry of Industry and Information Technology of the People's Republic of China
Sponsor: Posts & Telecom Press Co., Ltd.
Guiding Unit: China Satellite Network Group Co., Ltd.
Publisher: China InfoCom Media Group
Editor-in-Chief: LU Jun Executive
Editor-in-Chief: WU Wei
Associate Editor-in-Chief: WANG Chunting, LI Jianming, LYU Ziping,ZHU Decheng, SUN Qibin,
LIU Hualu
Director of Editorial Department: NIU Xiaomin
Deputy Director of Editorial Department: ZHAO Lulu
Address: F2, Beiyang Chenguang Building, Shunbatiao No.1 Courtyard, Fengtai District, Beijing, China
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E-mail: sigin@bjxintong.com.cn ISSN 2096-8930
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ISSN 2096-8930
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