Table of Content

    25 December 2020, Volume 18 Issue 4
    Special Topic
    Editorial: Special Topic on Future Advanced Satellite Communication Systems and Applications
    2020, 18(4):  1-2.  doi:10.12142/ZTECOM.202004001
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    Space‑Terrestrial Integrated Architecture for Internet of Things
    ZHANG Gengxin, DING Xiaojin, QU Zhicheng
    2020, 18(4):  3-9.  doi:10.12142/ZTECOM.202004002
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    To realize the ultimate vision of Internet of Things (IoT), only depending on terrestrial network is far from enough. As a supplement and extension of terrestrial network, satellite network can offer powerful support to realize the depth and breadth of the coverage. However, existing satellite networks are usually designed for particular purposes. Moreover, traditional satellite networks and terrestrial networks are developed and operated separately, consequently they cannot meet the need of network flexibility required by IoT. In this paper, a space-terrestrial architecture is conceived for constructing a space-terrestrial based IoT (ST-IoT) system. Additionally, a reliable identification procedure, an integrated access and communication procedure, as well as a clustering cooperative transmission strategy are also presented.

    Resource Allocation Strategy Based on Matching Game
    DENG Xu, ZHU Lidong
    2020, 18(4):  10-17.  doi:10.12142/ZTECOM.202004003
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    With the development of satellite communication technology, the traditional resource allocation strategies are difficult to meet the requirements of resource utilization efficiency. In order to solve the optimization problem of resource allocation for multi-layer satellite networks in multi-user scenarios, we propose a new resource allocation scheme based on the many-to-many matching game. This scheme is different from the traditional resource allocation strategies that just consider a trade-off between the new call blocking probability and the handover call failure probability. Based on different preference lists among different layers of medium earth orbit (MEO) satellites, low earth orbit (LEO) satellites, base stations and users, we propose the corresponding algorithms from the perspective of quality of experience (QoE). The simulation results show that the many-to-many matching game scheme can effectively improve both the resource utilization efficiency and QoE, compared with the one-to-one and many-to-one matching algorithms.

    DDoS Attack Detection Method for Space-Based Network Based on SDN Architecture
    JIA Min, SHU Yuejie, GUO Qing, GAO Zihe, XIE Suofei
    2020, 18(4):  18-25.  doi:10.12142/ZTECOM.202004004
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    With the development of satellite communications, the number of satellite nodes is constantly increasing, which undoubtedly increases the difficulty of maintaining network security. Combining software defined network (SDN) with traditional space-based networks provides a new class of ideas for solving this problem. However, because of the highly centralized network management of the SDN controller, once the SDN controller is destroyed by network attacks, the network it manages will be paralyzed due to loss of control. One of the main security threats to SDN controllers is Distributed Denial of Service (DDoS) attacks, so how to detect DDoS attacks scientifically has become a hot topic among SDN security management. This paper proposes a DDoS attack detection method for space-based networks based on SDN architecture. This attack detection method combines the optimized Long Short-Term Memory (LSTM) deep learning model and Support Vector Machine (SVM), which can not only make classification judgments on the time series, but also achieve the purpose of detecting and judging through the flow characteristics of a period of time. In addition, it can reduce the detection time as well as the system burden.

    Satellite E2E Network Slicing Based on 5G Technology
    ZHANG Jing, WEI Xiao, CHENG Junfeng, FENG Xu
    2020, 18(4):  26-33.  doi:10.12142/ZTECOM.202004005
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    We investigate the design of satellite network slicing for the first time to provide customized services for the diversified applications, and propose a novel scheme for satellite end-to-end (E2E) network slicing based on 5G technology, which provides a view of common satellite network slicing and supports flexible network deployment between the satellite and the ground. Specifically, considering the limited satellite network resource and the characteristics of the satellite channel, we propose a novel satellite E2E network slicing architecture. Therein, the deployment of the network functions between the satellite and the ground is coordinately considered. Subsequently, the classification and the isolation technologies of satellite network sub-slices are proposed adaptively based on 5G technology to support resource allocation on demand. Then, we develop the management technologies for the satellite E2E network slicing including slicing key performance indicator (KPI) design, slicing deployment, and slicing management. Finally, the analysis of the challenges and future work shows the potential research in the future.

    Adaptability Analysis of IP Routing Protocol in Broadband LEO Constellation Systems
    SUN Chenhua, YIN Bo, LI Xudong, TIAN Xing, PANG Ce
    2020, 18(4):  34-44.  doi:10.12142/ZTECOM.202004006
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    With the inclusion of satellite Internet as the information infrastructure in China’s “new infrastructure” category, relevant domestic industries and scientific research institutes have successively carried out the design of broadband low earth orbit (LEO) constellation systems and key technical research. As the core technology for the satellite-to-ground network communications of a broadband LEO constellation system, routing technology is extremely important for the efficient and reliable transmission of various service data. Focusing on the two important broadband LEO constellation systems in China, in-depth analysis and simulation of the high dynamics of the satellite-to-ground satellites are conducted in this paper to obtain more accurate network topology changes and characteristics; then the adaptability of the ground standard IP routing protocol to the broadband LEO constellation system is analyzed, and an LEO constellation simulation scenario is built with the Opnet software. The simulation results of the convergence performance of the standard IP routing protocol are produced. The results show that the IP protocol does not perform well for LEO satellite constellation networks. Based on the studies, some solutions are proposed to take full advantages of the characteristics of LEO satellite systems. These can also provide a reference for the choice of inter-satellite routing architecture and protocol technology for broadband LEO constellation in the future development.

    Advanced Space Laser Communication Technology on CubeSats
    LI Li, ZHANG Xuejiao, ZHANG Jianhua, XU Changzhi, JIN Yi
    2020, 18(4):  45-54.  doi:10.12142/ZTECOM.202004007
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    The free space optical communication plays an important role in space-terrestrial integrated network due to its advantages including great improvement of data rate performance, low cost, security enhancement when compared with conventional radio frequency (RF) technology. Meanwhile, CubeSats become popular in low earth orbit (LEO) network because of the low cost, fast response and the possibility of constituting constellations and formations to execute missions that a single large satellite cannot do. However, it is a difficult task to build an optical communication link between the CubeSats. In this paper, the cutting-edge laser technology progress on the CubeSats is reviewed. The characters of laser link on the CubeSat and the key techniques in the laser communication terminal (LCT) design are demonstrated.

    Feasibility Study of Decision Making for Terminal Switching Time of LEO Satellite Constellation Based on the SGP4 Model
    ZHOU Ping, ZHANG Yasheng, SUN Chenhua, XIAO Yongwei
    2020, 18(4):  55-61.  doi:10.12142/ZTECOM.202004008
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    The high speed of low earth orbit (LEO) satellites makes the terminals at each beam tend to switch rapidly and frequently. The predictable trajectories of LEO satellites allow for predictable terminal switching, therefore a simple and highly accurate orbit prediction model is required to swiftly obtain accurate switching time. This study utilizes the simplified general perturbations (Version 4) (SGP4) model to predict the LEO satellite trajectory of WT-1, an LEO satellite developed independently by the 54th Research Institute of China Electronics Technology Group Corporation (CETC). The obtained prediction results are compared with the actual telemetry data of the WT-1, which gives the accuracy of the SGP4 predicted satellite trajectory within 1 km. The terminal entry/exit beam timing is simulated by using the SGP4 model-predicted orbit and the satellite’s own telemetry data. The simulation result shows that the error between the SGP4 model-predicted terminal entry/exit beam timing and the actual timing is less than 1 s. The influence of terminal motion on prediction is discussed. The results show that the error caused by the movement of the ground terminal on the prediction is less than 0.687 s, and the SGP4 model has a definitely practical value for terminal switching determination in the LEO constellation.

    M‑IRSA: Multi‑Packets Transmitted Irregular Repetition Slotted Aloha
    SUN Jingyun, LIU Zhen, WU Yang
    2020, 18(4):  62-68.  doi:10.12142/ZTECOM.202004009
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    The design of random media access control (MAC) protocol has been attracting great attention for satellite communication networks, where the propagation delay is long and the traffic load is varying. Advanced coded random access schemes tend to provide resource allocation strategies for massive uncoordinated devices, where multiple packet replicas from each user are transmitted in random slots of the frame and successive interference cancellation (SIC) iterations are tracked to recover collided packets at the receiver. It is assumed that each active user just has a single information packet to be transmitted. In this paper, an MAC layer random access scheme named Multi-Packets Transmitted Irregular Repetition Slotted Aloha (M-IRSA) is proposed. Different from the existing advanced random access schemes, the M-IRSA scheme supports various number of packet transmission per user by using pre-coding procedure. Joint decoding combined with SIC iterations and local decoding is analyzed. The simulation results show that the proposed scheme is more efficient compared with the IRSA scheme without packet loss rate (PLR) loss.

    Research Paper
    Robust Lane Detection and Tracking Based on Machine Vision
    FAN Guotian, LI Bo, HAN Qin, JIAO Rihua, QU Gang
    2020, 18(4):  69-77.  doi:10.12142/ZTECOM.202004010
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    Lane detection based on machine vision, a key application in intelligent transportation, is generally characterized by gradient information of lane edge and plays an important role in advanced driver assistance systems (ADAS). However, gradient information varies with illumination changes. In the complex scenes of urban roads, highlight and shadow have effects on the detection, and non-lane objects also lead to false positives. In order to improve the accuracy of detection and meet the robustness requirement, this paper proposes a method of using top-hat transformation to enhance the contrast and filter out the interference of non-lane objects. And then the threshold segmentation algorithm based on local statistical information and Hough transform algorithm with polar angle and distance constraint are used for lane fitting. Finally, Kalman filter is used to correct lane lines which are wrong detected or missed. The experimental results show that computation times meet the real-time requirements, and the overall detection rate of the proposed method is 95.63%.

    Balanced Discriminative Transfer Feature Learning for Visual Domain Adaptation
    SU Limin, ZHANG Qiang, LI Shuang, LIU Chi Harold
    2020, 18(4):  78-83.  doi:10.12142/ZTECOM.202004011
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    Transfer learning aims to transfer source models to a target domain. Leveraging the feature matching can alleviate the domain shift effectively, but this process ignores the relationship of the marginal distribution matching and the conditional distribution matching. Simultaneously, the discriminative information of both domains is also neglected, which is important for improving the performance on the target domain. In this paper, we propose a novel method called Balanced Discriminative Transfer Feature Learning for Visual Domain Adaptation (BDTFL). The proposed method can adaptively balance the relationship of both distribution matchings and capture the category discriminative information of both domains. Therefore, balanced feature matching can achieve more accurate feature matching and adaptively adjust itself to different scenes. At the same time, discriminative information is exploited to alleviate category confusion during feature matching. And with assistance of the category discriminative information captured from both domains, the source classifier can be transferred to the target domain more accurately and boost the performance of target classification. Extensive experiments show the superiority of BDTFL on popular visual cross-domain benchmarks.

    Table of Contents, Volume 18, 2020
    Table of Contents, Volume 18, 2020
    2020, 18(4):  84-86. 
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    The whole issue of ZTE Communications December 2020, Vol. 18 No. 4
    2020, 18(4):  0. 
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