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    25 April 2021, Volume 42 Issue 4
    Topics: Strategic Technologies to Massive Connecting for the Future Mobile Networks
    Random access for massive Internet of things:current status, challenges and opportunities
    Pingzhi FAN, Li LI, Huan CHEN, Gaofeng CHENG, Linjie YANG, Xiaobo TANG
    2021, 42(4):  1-21.  doi:10.11959/j.issn.1000-436x.2021098
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    In conventional communication systems, the random access (RA) is a necessary procedure for a user equipment (UE) to establish wireless connection to the network before actual data transmission.Focusing on the massive IoT with large number of nodes, the fundamental characteristics and limitations of conventional grant-based RA were firstly discussed.Then, the grant-free RA, semi-grant-free RA and unsourced RA for massive IoT were addressed in details from multiple perspectives, including their system models, protocol frameworks, algorithm procedures, system performance, related pros and cons, as well as critical challenges and potential opportunities.Finally, some highlights on the related key techniques and common issues in random access for massive IoT were concluded.

    Review on strategic technology of dense connection for the future mobile network
    Zhihong QIAN, Lin XIAO, Xue WANG
    2021, 42(4):  22-43.  doi:10.11959/j.issn.1000-436x.2021094
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    Based on reviews of the work regarding dense connection, the strategic technologies for dense connection in the upcoming future mobile communication were illuminated.The state of the art of dense connection, including network architecture and related technologies, the transmission technology of dense connection, and the access technology of dense connection were analyzed.A flexible access network structure with verity of connection forms coexisting was proposed.Aiming at the asymmetry of uplink and downlink coverage and considering the QoS requirements of users, a dense terminal access scheme based on the uplink-and-downlink-separated network architecture was proposed.The necessity of the three-dimensional network architecture and the integration of communication and computing to meet the needs of large-scale networking and dense connection were illuminated.Based on technologies such as terahertz and block chain, the future strategic exploratory trends such as the upward extension of frequency bands and the sharing of spectrum resources were discussed and prospected.

    Research on mobile edge computing and caching in massive wireless communication network
    Yongming HUANG, Chong ZHENG, Zhengming ZHANG, Xiaohu YOU
    2021, 42(4):  44-61.  doi:10.11959/j.issn.1000-436x.2021096
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    For the large-scale network mobile edge computing and caching technology of future 6G mobile communications, firstly, the architectures and principles of mobile edge computing and caching in large-scale wireless networks were introduced, and the necessity and universality were clarified.Then, from the perspective of the five key issues in the mobile edge computing and caching enabled large-scale wireless network, including computing offloading, edge caching, multi-dimensional resource allocation, user association and privacy protection, the recent researches and further pointed out the future development trends and research directions were reviewed and analyzed.Finally, for the privacy preservation issue, a federated learning based privacy-preserving scheme was proposed.Simulation results show that the proposed scheme can simultaneously preserve user privacy and improve the quality of service.

    Three-three-three network architecture and learning optimization mechanism for B5G/6G
    Jinkang ZHU, Mingyang CHAI, Wuyang ZHOU
    2021, 42(4):  62-75.  doi:10.11959/j.issn.1000-436x.2021095
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    Aiming at the problem that the future B5G/6G network is a complex intelligent network with large connections, coupled with the comprehensive application of 3G, 4G, 5G and even 6G, the future networks will inevitably become extremely complex, a three-three-three network architecture was proposed that was a network that includes three types of networks (core network, access network and terminal network), three resources (frequency band, power and time consumptions) and three requirements (active, work and service), which was a three-dimensional comprehensive optimization system architecture, referred to as the three-three-three network.Furthermore, the mathematical basic formulas of the three-dimensional complex network were analyzed, the knowledge + data-driven learning model and the optimization method of intelligent processing using the knowledge learning mechanism were presented.Finally, the numerical example and reachable performance of the three-three-three network were given.Those results demonstrate that the proposed network architecture and the learning optimization mechanism are beneficial for designing future large-connected complex intelligent networks.

    Joint time and beam domain non-orthogonal multiple access
    Zhaoyang ZHANG, Jiajia WU, Jue WANG, Chu ZHOU
    2021, 42(4):  76-88.  doi:10.11959/j.issn.1000-436x.2021099
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    In order to improve the system’s ability to accommodate connected devices, a joint time and beam domain non-orthogonal multiple access (NOMA) scheme was proposed, which was suitable for millimeter wave massive multiple-input multiple-output (MIMO) systems.The correlation and difference of the users’ channel were utilized to realize beam-domain NOMA, and sparse spreading technology was utilized to realize time-domain NOMA.With the optimization goal of improving the communication reliability of the system, optimization problem of the joint domain sparse access matrix design was constructed and solved.Finally, the access matrix was reconstructed based on the channel quality of the joint domain, and the interference cancellation operation was added to the message passing algorithm (MPA), which reduced the decoding complexity and improves the communication reliability.

    Recovery mechanism of large-scale damaged edge computing network in industrial Internet of things
    Hui TIAN, Hao WU, Yang TIAN, Jianyang REN, Yajuan CUI, Wenbao AI, Jianhua YUAN
    2021, 42(4):  89-99.  doi:10.11959/j.issn.1000-436x.20211100
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    Given the limited resources at early stages for recovery, a failure recovery mechanism of the edge computing network considering both computational demands and repair costs was proposed, which intends to tackle the problem of the high probability of large-scale cascading failure caused by the interdependence between the edge computing network and other subnetworks in industrial Internet of things (IIoT).Considering the network structure (topology and link capacity) and network dynamics (computational demands), a joint link recovery selection and computation migration optimization problem was formulated under the conservation of node computing requirements.By leveraging the Benders decomposition algorithm, the NP-hard problem was transformed into a main problem and a sub-problem, which were interdependent and could be solved in polynomial time through the approximation of cutting planes.A local branching method was further introduced to guarantee the non-increasing nature of the Benders upper bound, thus accelerating the convergence of Benders decomposition.Simulation results demonstrate that the proposed algorithm outperforms the conventional topology-based recovery algorithm in system utility, and can perform well in multiple scenarios.

    Connectivity analysis of IoV based on scale-free network
    Tao HAN, Wei HE, Jun DAI, Yong ZUO, Yang YANG, Xiaohu GE
    2021, 42(4):  100-108.  doi:10.11959/j.issn.1000-436x.2021101
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    The connectivity of moving vehicles is one of the critical metrics in Internet of vehicles (IoV) that critically influence the performance of data transmission.Due to the high-frequency dynamic changes of the network topology of the IoV, which causes the link to be easily disconnected frequently.It is a critical issue to reduce the probability of link disconnection, and reducing the randomness of link establishment improves the overall network connectivity.To solve the above problems, the network’s connectivity was analyzed under the line of sight path loss model and the interference model, and the dynamic growth (DN) algorithm was designed through the characterization of the IoV link in the real world.Moreover, a scale-free VANET was built through the network’s addition and deletion of nodes and link preference connections.Simulation results indicate that the overall connectivity of the network is improved by 16%.

    Resource scheduling algorithm of satellite communication system for future multi-beam dense networking
    Yuanzhi HE, Cong PENG, Jihong YU, Yun LIU
    2021, 42(4):  109-118.  doi:10.11959/j.issn.1000-436x.2021102
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    The resource scheduling problem of satellite communication systems under the condition of high-dynamic and resource limitation was studied.A resource scheduling model for satellite communication systems was established based on time window, energy consumption, number of channels, user priority and task suddenness.Considering the disadvantages of slow initial search speed and weak local search ability, the improved ant colony algorithm based on construction of initial solution set and extra pheromone deposition was proposed to solve the resource scheduling problem.The optimization characteristics of the number of completed tasks, priority and scheduling completion time were simulated and analyzed.The results show that the algorithm has a fast convergence rate.Compared with the same type optimization algorithm, the algorithm has high scheduling efficiency, therefore, it is suitable for scheduling satellite communication system resources for multi-beam dense networking in the future.

    Relay selection algorithm based on selfish behavior analysis in ultra-dense D2D
    Yijun WANG, Youxu ZHANG, Dakun LIU, Guifen CHEN
    2021, 42(4):  119-126.  doi:10.11959/j.issn.1000-436x.2021103
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    In ultra-dense D2D communication, the current relay selection schemes mainly assume that the relay device has the initiative to participate in data forwarding, but some rational relay devices may delay or refuse to forward due to their own considerations, thus affecting the user experience.From the perspective of selfish behavior of relay devices, a method to identify selfish relay devices in D2D communication was proposed, and then an ultra-dense D2D relay selection algorithm based on selfish behavior analysis was proposed.Firstly, three relay identification attribute factors, namely joint interest degree (JID), forwarding history ratio (FHR) and relay physical state (RPS) were defined, and their weights were calculated by triangular fuzzy function to identify relay devices with selfish behavior.Secondly, based on the TOPSIS (technique for order of preference by similarity to ideal solution) method, the final relay equipment selection scheme relay was realized.Simulation results show that the proposed algorithm can identify selfish relay devices more effectively in D2D communication.Compared with other relay selection algorithms, the proposed algorithm has made significant progress in the aspects of D2D communication forwarding success rate, system average throughput and average time delay.

    Papers
    SQLMVED: SQL injection runtime prevention system based on multi-variant execution
    Bolin MA, Zheng ZHANG, Hao LIU, Jiangxing WU
    2021, 42(4):  127-138.  doi:10.11959/j.issn.1000-436x.2021046
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    The effectiveness of combining SQL statement parsing with randomization to defend against SQL injection attack (SQLIA) was based on the fact that attackers did not know about the current method of randomization adopted by system.Therefore, once attackers had mastered the current method of randomization who can launch effective SQLIA.In order to solve this problem, a SQL injection runtime prevention system based on multi-variant execution was designed, the multi-variant apply randomization methods from any other, so that illegal SQL statements could not be parsed successfully by all variants.Even if attackers had mastered the method of randomization, illegal SQL statements could only be parsed successfully by a certain variant at most, meanwhile the parsing results of multiple variants were voted to find the abnormality in time and block attack path.The prototype system SQLMVED is implemented for Web services and experiments show that the prototype can effectively defeat SQLIA.

    Secure and verifiable multi-keyword searchable encryption scheme in cloud
    Jianhong ZHANG, Menglong WU, Jing WANG, Pei LIU, Zhengtao JIANG, Changgen PENG
    2021, 42(4):  139-149.  doi:10.11959/j.issn.1000-436x.2021054
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    Due to the advantages of cloud computing, such as virtualization and high scalability, individuals and enterprises are willing to outsource local data storage and computing to cloud servers.However, encryption breaks the linkability between the data.Although searchable encryption (SE) enables cloud servers to provide retrieval services of the encrypted data for data owners, cloud servers who are untrusted, may tamper and delete data, or learn information of the newly added encrypted files with previous trapdoors.Besides, single-keyword search inevitably incurs many unrelated results, resulting in a waste of bandwidth and computing resources.To address the problems above, an efficient and verifiable multi-keyword search encryption scheme was proposed, which could not only supported multiple-keyword search, but also realized the privacy of search pattern and forward security of the outsourced files.In the meanwhile, it also ensured the integrity check of the outsourced data.Through rigorous security verification, the proposed scheme was proved to be secure under the standard mode, and could resist offline keyword guesswork attack (KGA) on untrusted cloud servers.Finally, by comparing the efficiency and performance with the recent three searchable encryption schemes, the experimental results show that the proposed scheme has the best comprehensive performance in terms of function and efficiency among the four schemes.

    Evidence conflict measurement method based on Pignistic probability transformation and singular value decomposition
    Xinglin GUO, Zhenxiao SUN, Yuyao ZHOU, Lianzhi QI, Yi ZHANG
    2021, 42(4):  150-157.  doi:10.11959/j.issn.1000-436x.2021086
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    In view of the problem of poor adaptability and low accuracy of common evidence conflict measurement method, an evidence conflict measurement method based on Pignistic probability transformation and singular value decomposition was proposed.First, Pignistic probability transformation was used to map the evidence focal element difference to the belief difference, and the evidence composite belief function matrix was constructed.Then, the matrix features were extracted by singular value decomposition, and the matrix feature space was divided into similar subspace and conflict subspace according to singular value characteristics.Considering the similarity and conflict characteristics of the evidence matrix, and the ratio of the singular value of the conflict subspace to the singular value of the similar subspace was taken as the new conflict measure factor.Finally, the proposed method was compared with common methods in various evidence conflict scenarios, such as full conflict scenario, variable reliability scenario, variable focus element scenario, focal element nested scenario, and the results show that the proposed method has wide adaptability, high accuracy and good stability.

    Method for detecting collusion attack node in road condition information sharing based on reputation point
    Shichang XUAN, Hao TANG, Wu YANG
    2021, 42(4):  158-168.  doi:10.11959/j.issn.1000-436x.2021051
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    Aiming at the problem that on occasion of the release of false road condition information by collusion nodes in the Internet of vehicles collaboratively, message authenticity could not be guaranteed in the process of road condition information sharing, a method for detecting collusion attack nodes in road condition information sharing based on reputation points was proposed.In the process of road condition information aggregation, a malicious information detection algorithm was designed to detect false messages issued by colluding nodes, which could ensure the authenticity and accuracy of messages delivered in the system.Experimental results show that the proposed method has higher detection efficiency for collusion nodes and adaption to a proportion of collusion nodes through security evaluation and experiments in comparison with the existing schemes.

    Linear property and optimal design of MARS-like cryptographic structure
    Nianping WANG, Lirong HONG
    2021, 42(4):  169-176.  doi:10.11959/j.issn.1000-436x.2021068
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    A MARS-like cryptographic structure was proposed and some linear properties of this cryptographic structure were given.An optimal design method of linear transformation in MARS-like cryptographic structure was also given.Concretely, by analyzing the transfer law of a class of linear approximation with special structure, regardless of the selected linear bijection, the existence of the linear approximation with 0 active round function in the t(1≤t≤3) round had been demonstrated.Furthermore, there was at least one with no more than 1, ?8t/15? active round function among the 4, t(t>4)-round of linear approximation, respectively.On this basis, an optimal design method was proposed to make the lower bound of the number of active round function closer to the maximum possible value than the MARS cryptographic structure for the linear transformation in the MARS-like cryptographic structure.

    Basis expansion model-based improved regularized orthogonal matching pursuit channel estimation for V2X fast time-varying SC-FDMA
    Yong LIAO, Zhirong CAI
    2021, 42(4):  177-184.  doi:10.11959/j.issn.1000-436x.2021081
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    In order to further improve the vehicle-to-everything (V2X) communication performance of the Internet of vehicles, a basis expansion model (BEM) was adopted and suitable for high-speed mobile scenarios to transform the channel estimation into a sparse signal reconstruction.Furthermore, it was proved that the BEM coefficients were sparse, and an improved regularized orthogonal matching pursuit (iROMP) channel estimation algorithm based on BEM (BEM-iROMP) was proposed.BEM coefficients were acquired by the iROMP, and finally the feedback results were iterated to achieve the optimal channel estimation.Simulation results show that in comparison with the least square (LS), linear minimum mean squared error (LMMSE), and BEM-LS channel estimation algorithms, the proposed algorithm can effectively improve the normalized mean square error (NMSE) and bit error rate (BER) performance.

    Secure beamforming design for IRS-assisted SWIPT Internet of things system
    Zhengyu ZHU, Jinlei XU, Gangcan SUN, Ning WANG, Wanming HAO
    2021, 42(4):  185-193.  doi:10.11959/j.issn.1000-436x.2021060
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    In order to meet the new requirements of intelligent signal processing deployment and physical layer security for green interconnection of things, a design method of secure beamforming was proposed to solve the problem of the shortage of sustainable energy supply in the information and energy transmission at the same time Internet of things (IoT) system assisted by intelligent reflecting surface (IRS).Considering the constraints of secrecy rate, transmit power and IRS reflection phase shift, the optimization problem was modeled as a non-convex quadratic programming problem with quadratic constraints, aiming at maximizing the acquisition power of energy collector, and jointly optimizing the base station transmit beamforming matrix, jammer covariance matrix and IRS phase shift.The non-convex quadratic problem was transformed into an equivalent convex problem by using the relaxation variable, semidefinite relaxation method, auxiliary variable and sequence parameter convex approximation method, and an alternative iterative optimization algorithm was proposed to obtain the feasible solution of the original problem.Simulation results show that the proposed algorithm can converge quickly and improve performance effectively compared with the benchmark scheme.

    Correspondences
    Design of microwave ceramic waveguide filter with high out-of-band suppression characteristics
    Fei LIANG, Shunliang MENG, Wenzhong LYU
    2021, 42(4):  194-201.  doi:10.11959/j.issn.1000-436x.2021029
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    The design theory of ceramic waveguide filter was introduced, and then the combination structure of coupling through slot with shallow or deep coupling blind hole was designed, which could meet the requirements of positive and negative coupling bandwidth.By adjusting the cross coupling between 3~6 cavities, the symmetry of the filter transmis-sion curve was improved, and the near and far end band suppression of the filter was realized.Finally, a six-cavity ce-ramic waveguide filter for 5G base station was designed.In the process of optimizing the filter, the influences of the rela-tive position offset of the cross-coupling through slot and the length of the cross-coupling through slot on the transmis-sion zero position, the near end and far end out of band suppression characteristics of the filter were discussed in detail, and the relevant change rules were given.The performance indexes of the optimized filter were as follows, center fre-quency was 3.5 GHz, working bandwidth was 200 MHz, insertion loss ≤ 1.2 dB, return loss ≥ 17 dB, near end out of band rejection ≥ 25 dB, far end out of band rejection ≥ 51 dB.According to the structural parameters of the simulation model, the performance test results of the samples are in good agreement with the simulation results.

    Research on ionospheric parameters prediction based on deep learning
    Yuntian FENG, Xia WU, Xiong XU, Rongqing ZHANG
    2021, 42(4):  202-206.  doi:10.11959/j.issn.1000-436x.2021097
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    For ionospheric parameter prediction, the short-term and daily mean value prediction of ionospheric parameters was established by long short-term memory (LSTM) predictive neural network modeling.Two methods of point-by-point prediction and sequence prediction were utilized.Furthermore, in order to predict the hourly and daily changes of ionospheric parameters, the proposed scheme was optimized by multidimensional prediction and empirical mode decomposition (EMD) algorithm.Finally, the feasibility of the proposed optimization algorithm in improving the prediction accuracy of ionospheric parameters is verified.

Copyright Information
Authorized by: China Association for Science and Technology
Sponsored by: China Institute of Communications
Editor-in-Chief: Zhang Ping
Associate Editor-in-Chief:
Zhang Yanchuan, Ma Jianfeng, Yang Zhen, Shen Lianfeng, Tao Xiaofeng, Liu Hualu
Editorial Director: Wu Nada, Zhao Li
Address: F2, Beiyang Chenguang Building, Shunbatiao No.1 Courtyard, Fengtai District, Beijing, China
Post: 100079
Tel: 010-53933889、53878169、
53859522、010-53878236
Email: xuebao@ptpress.com.cn
Email: txxb@bjxintong.com.cn
ISSN 1000-436X
CN 11-2102/TN
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