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20 March 2023, Volume 4 Issue 1

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Special Issue: Key Technologies for Networking and TT＆C in Large Scale Constellations

Multi-Ground Station Collaborative Measurement and Control Technology for Giant Constellation System

Yang LIU, Di ZHOU, Min SHENG, Jiandong LI, Shiguang HAO, Xiaotian ZHENG

2023, 4(1):  2-11.  doi:10.11959/j.issn.2096-8930.2023001

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Measurement and control technology is the key technology to ensure the effi cient operation, maintenance and management of the constellation system.In recent years, with the continuous expansion of the constellation scale, mega-constellation system has gradually formed, which makes the demand for constellation measurement and control show an explosive growth, which puts forward new requirements for the completion of the constellation system measurement and control tasks.Firstly, the constraints of the megaconstellation system measurement and control tasks and the equipment constraints of the ground measurement and control station were analyzed, and the problem modeling was given; Secondly, an interaction method of the ground station agent based on the learning planning segment was proposed, by introduced the constraint penalty operator and the multi-ground station joint the penalty operator was designed to optimized the objective function.Finally, a multi-ground station Agent reinforcement learning algorithm was proposed to solved the multi-ground station cooperative task assignment strategy.Simulation experiments showed that when the task scale was large, the method had a gain of 12%~20% compared with the traditional algorithm in the diff erent scenarios mentioned.

Resource Scheduling Method for Integration of TT＆C and Observation Based on Multi-Agent Deep Reinforcement Learning

Siyue CHENG, Haoran LI, Weigang BAI, Di ZHOU, Yan ZHU

2023, 4(1):  12-22.  doi:10.11959/j.issn.2096-8930.2023002

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With the development of satellite communication technology and the continuous expansion of the constellation scale, the integration of TT＆amp;C and observation technology has become the mainstream trend.The large constellation scale, many scheduling objects and complex operation joint control bring great challenges to the integrated resource scheduling of satellite network TT＆amp;C and observation.Subject to the low solution effi ciency and complex constraints of scheduling algorithms, the traditional TT＆amp;C resource scheduling technology adopts the advance injection TT＆amp;C instructions to perform tasks according to the fi xed deployment, which is diffi cult to meet the scheduling needs of emergencies and emergency tasks.Therefore, a kind of resource scheduling method based on multi-agent actor-Agent Actor-Critic Deterministic Policy Gradient Algorithms (MADDPG) was presented.With centralized training and distributed execution, the multi-agent model of integrated task of TT＆amp;C and observation was established.By analyzed the scheduling strategy of neighbor agent, the response speed of local information was improved.According to the model and constraints in the integrated resource scheduling problem of TT＆amp;C and observation, selected signifi cant and interpretable constraints, then established the multi-agent resource scheduling reinforcement learning model, and carried on the simulation test.The simulation results showed that the task benefi t of this method was 22% higher than the traditional method.

Robust Scheduling Method of TT＆C Resource in Satellite Network

Xiang JI, Runzi LIU, Chenhong YAO, Jianhao CHEN, Tao MU

2023, 4(1):  23-30.  doi:10.11959/j.issn.2096-8930.2023003

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The continuous growth of satellite network scale brings great challenges to the eff ective scheduling of TT＆amp;C resources.Aff ected by weather and other factors, the performance of the satellite-ground link is of high uncertainty.In order to took into both resource utilization and task reliability, a robust scheduling method of TT＆amp;C resources was proposed.This method could arranged the start time and duration of the transmission window for TT＆amp;C tasks by the predicted the channel state distribution of satelliteground link and the task distribution in the planning period, and optimized the resource allocation scheme by backward iteration to maximized the expected profit of the tasks.The experimental results showed that compared with the traditional non-robust scheduling method, the scheduling method proposed could obtain more task profi t under diff erent channel distributions and achieve the improvement of both resource utilization and task reliability.

Design and Verifi cation of Real-Time Simulation System for Protocol Design and Performance Evaluation of Large-Scale Satellite Network

Qixuan CAO, Yan SHI, Lianwei ZHOU, Xinwang DING

2023, 4(1):  31-41.  doi:10.11959/j.issn.2096-8930.2023004

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Aiming at the problems above, a real-time network simulation test system named SiT4NET was studied and developed.Firstly, SiT4NET used container technique to solved the problem of large-scale network node deployment with limited resources on the basis of ensuring nodes’ independence, thus improved the resource utilization of the simulation system.Secondly, the packet transmission between nodes based on data units and the mechanism for requesting/retrieving system-level data units were innovatively proposed to provided a strong foundation for real-time network simulation.And thirdly, through the standard high-level protocol interface, internal packet format and reconfi gurable mechanism of packet processing, SiT4NET reduced the complexity of conversion between the simulation implementation of the protocol and the target platform.Finally, by set up the same satellite network environment on SiT4NET and OPNET platforms, set up multiple groups of simulation scenarios, compared and analyzed the results, it showed that this method could met the performance requirements of large-scale satellite network.

Studies

Research Status of CPM for Satellite-Terrestrial Integrated Network

Zihao PAN, Chen XIE, Heng WANG, Daoxing GUO

2023, 4(1):  42-49.  doi:10.11959/j.issn.2096-8930.2023005

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Around the vision of ＆quot;full coverage＆quot; of the new generation of mobile communication system (6G), satelliteterrestrial integration, as one of the key technologies, is the development direction of the future wireless communication system.The construction of satellite-terrestrial integration network and deep integration need reasonable waveforms at physical layer.In view of the problems of transmission in satellite-terrestrial integration, the signifi cant advantages and practicability of continuous phase modulation (CPM) signal in spectral effi ciency and energy effi ciency were analyzed.The research progress of CPM signal at receiver in mobile communication system from the time and frequency domain were discussed, which provided support for CPM related research in satellite-terrestrial integration in the future.

Development Status and Trends of Space Processor

Zhigang YU, Xu FENG, Zhou LU, Jixing GAO, Wenhui DING

2023, 4(1):  50-58.  doi:10.11959/j.issn.2096-8930.2023006

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Space electronic system is the ＆quot;brain＆quot; of aerospace engineering models and the core fi eld of competitive development of major countries around the world.As the most core device in space electronic system, space processor directly aff ects the performance, reliability and safety of aerospace models.On the basis of brief introduced of space electronic systems, fi rstly, the development status of foreign space processors was analyzed, and then the development roadmap of space processors such as SPARC, PowerPC, ARM, RISC V, etc were combed and formed.The development process was summarized into three stages:initial stage, development stage and new stage, considered architecture and performance parameters.Finally, the development trend of space processors in the future was summarized as ＆quot;fi ve modernizations＆quot;: micro system, commercialization, intelligent, ecological and cloud enabled.

LEO Satellite Internet of Things Access Technology Based on Beamforming

Xuxu XIE, Xiaojin DING, Tao HONG, Gengxin ZHANG

2023, 4(1):  59-65.  doi:10.11959/j.issn.2096-8930.2023007

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The integration of terrestrial communication and satellite communication for internet of things (IoT) is the inevitable trend of the development of wireless communication network, to achieve the vision of the connection of everything.As a supplement to terrestrial IoT, satellite IoT can make up the fl aws of terrestrial IoT.However, with the expansion of IoT scale, it will be diffi cult for satellites to meet the communication needs of increasing number of IoT terminals, because the problem of limited satellite load will become increasingly prominent.Multiple-input multiple-output (MIMO) technology is the key technology of terrestrial 5G, and also an important research direction of satellite communication in the future 6G.The beamforming(BF) technology was introduced in MIMO into the low earth orbit (LEO) satellite based IoT, to made full use of spatial resources and signifi cantly improved system capacity.In view of the implementation conditions of BF technology and the characteristics of satellite IoT, several related issues were discussed, included channel model, BF criterions, load balancing access technology of one satellite and cooperative BF access technology of several satellites.

High-Throughput Satellite Precoding Algorithm Based on Non-Ideal Channel State Information

Yingzhe DOU, Guanchang XUE, Mingchuan YANG

2023, 4(1):  66-72.  doi:10.11959/j.issn.2096-8930.2023008

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In order to suppress co-channel interference caused by frequency reuse, high-throughput satellite communication systems have begun to study ground interference suppression technologies, including multi-user detection technology applied in the reverse link and precoding technology applied in the forward link.A forward link model was established that took into account the eff ects of free space loss, rain attenuation, and beam gain.Based on the non-ideal channel state information model, the minimum mean square error precoding algorithm was improved, and an improved minimum mean square error precoding algorithm suitable for non-ideal channel state information was proposed.The satellite precoding algorithm considered adopted a more accurate channel model with irrational channel information, and incorporated the non-ideal channel state information into the precoding algorithm and eliminated it.The simulation results showed that the high-throughput satellite precoding algorithm could signifi cantly improved the throughput of the system under the condition of non-ideal channel state information, and also improved the robustness of the system.

Studies

Multi-User Detection Algorithm for Asynchronous Non-Orthogonal Multiple Access Based on Gaussian Approximation

Peisen WANG, Yueneng WANG, Boming CHENG, Yue YANG, Neng YE

2023, 4(1):  73-81.  doi:10.11959/j.issn.2096-8930.2023009

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Code domain non-orthogonal multiple access (NOMA) is one of the potential technologies to realize ubiquitous access in the future satellite internet.Considering that satellite-to-ground transmission has the characteristics of large propagation delay and high channel dynamics, strict timing synchronization between ground devices will lead to unbearable time resource overhead.Loosed synchronization relationship are required to achieve multi-user access in satellite internet.However, most of the existing multi-user detection algorithms in code domain NOMA are based on the assumption of synchronous transmission, which cannot accurately model and eff ectively alleviate the complex interference introduced by asynchronous multi-user transmission.Therefore, a novel multi-layer factor graph model by introduced the relative delay among users into the traditional two-part factor graph was constructed, and a low-complexity asynchronous multi-user detection algorithm based on gaussian approximation was proposed.The proposed algorithm iterated between each user's estimates and propagated the estimated information between users to improved the approximation.Simulation results showed that in high SNR region, the performance of the asynchronous code-domain NOMA with the proposed algorithm even outperforms its synchronous counterpart.

SCMA High-Dimensional Codebook Design Based on VBR-GAM

Xu DENG, Ke CHU, Lidong ZHU

2023, 4(1):  82-88.  doi:10.11959/j.issn.2096-8930.2023010

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At the physical layer, sparse code multiple access (SCMA) technology is used to solve the problem of massive user access.In the current research on SCMA, in addition to the research on SCMA multi-user detection technology, more attention will be paid to the design of SCMA system codebooks.SCMA codebook with good performance can not only improve its anti noise performance in the process of multi-user detection, but also reduce the detection complexity.The traditional codebook design scheme is mainly researched on low-dimensional codebooks, and most of the designed codebook schemes are based on QAM, TCM, and Lattice, while few people have set foot in and studied high-dimensional codebooks.A new codebook design - Golden Angle Modulation (GAM) was mainly focused on, and on this basis, proposed a Variable Bit Rate (VBR) GAM codebook design method.The simulation results showed that the VBR-GAM codebook could fl exibly met the needs of diff erent services.With the increased of the modulation order, the VBR-GAM codebook had better performance than the traditional GAM codebook.

Applications

Interleaved-LoRa Transmission Scheme for Satellite IoT

Jin LUO, Jiabao XIA, Yang BAI, Baoming BAI

2023, 4(1):  89-97.  doi:10.11959/j.issn.2096-8930.2023011

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The transmission distance of satellite IoT is much further than terrestrial IoT, resulting in a signifi cant power loss on the transmission link.Thus the received signal power at a receiver will be signifi cantly lower.Combining a high-performance FEC coding and LoRa modulation with a signifi cant spreading factor enables reliable communication at very low signal-to-noise ratios.However, LoRa modulation dramatically decrease spectral effi ciency as the spreading factor increases.An interleaved LoRa transmission scheme that could achieved high spectral effi ciency with a low bit error rate (BER) was proposed.Firstly, a non-coherent soft demodulation algorithm was presented for LoRa and the corresponding performance comparison with the use of Turbo and LDPC codes.Then proposed a soft demodulation algorithm for interleaved-LoRa transmission.Simulation results showed that Turbo coded interleaved-LoRa system outperformed the uncoded system by about 4 dB at a BER=10^-5, which was equivalently to a 55%~57% improvement on communication distance in free space.Furthermore, the spectral effi ciency was improved by approximately 23% compared to the existing Turbo-LoRa scheme.

Adaptive Fuzzy PID Control System for Satellite Earth Station Antenna Group Factor Based on Edge Calculation

Haibin SHAN, Yanjun SHI, Zijing LIU, Yuanhong LI, Wenhua ZHAO, Muquan HE, Chuzhou LI

2023, 4(1):  98-102.  doi:10.11959/j.issn.2096-8930.2023012

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The antenna tracking control system of satellite ground receiving station generally adopts PID control.Due to the infl uence of various uncertain factors, it is diffi cult to obtain the optimal control parameters for this kind of system, resulting in the PID control eff ect is not ideal.An adaptive fuzzy PID antenna tracking control system based on edge computing was designed.The parameters of PID controller were adjusted in time by fuzzy control algorithm, and the optimal calculation of fuzzy control input and output domain was realized in edge computing server.The simulation results showed that the adaptive fuzzy PID antenna tracking control system based on edge calculation could achieve good control eff ect.