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    20 June 2021, Volume 37 Issue 6
    Topic: 5G+6G
    Information timeliness metrics and research progress for 6G network
    Jingzhou SUN, Lehan WANG, Yuxuan SUN, Sheng ZHOU, Zhisheng NIU
    2021, 37(6):  3-13.  doi:10.11959/j.issn.1000-0801.2021127
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    In the future 6G network, machine-type communication will dominate the network traffic.Many vertical applications, such as networked autonomous driving and industrial internet of things, will become new growth points.Such applications usually consist of the collection of status information and distribution of control signals, requiring ultra-low latency.However, this requirement is hard to meet with a large number of end nodes and limited communication resources.In view of this confliction, it was pointed out that the freshness of information should be considered in the status update system instead of just latency.Furthermore, according to the degree of utilization of status information, various measures of information freshness were introduced, and related representative work was summarized.Finally, the future research directions of information freshness and key questions that need to be answered were discussed.

    GAN-based channel estimation for massive MIMO system
    Yuxiu HUA, Rongpeng LI, Zhifeng ZHAO, Jianjun WU, Honggang ZHANG
    2021, 37(6):  14-22.  doi:10.11959/j.issn.1000-0801.2021135
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    As a key technology of 5G, massive MIMO system can significantly improve spectrum efficiency and energy efficiency by equipping a large number of antennas in base stations.However, in massive MIMO system, accurate channel estimation faces severe challenges.In order to estimate the channel accurately when the pilot sequence length is smaller than the number of transmitting antennas and the channel noise is strong, the estimation method N2N-GAN was proposed.N2N-GAN firstly denoised the pilot channel at the receiving end, and then used the conditional generative adversarial network to estimate the channel matrix according to the denoised pilot signal.Simulation experiments show that N2N-GAN achieves better robustness against noise compared with traditional channel estimation algorithms and deep learning-based methods.Meanwhile, it can adapt to scenarios with fewer pilot symbols and more antennas.

    Transceiver design and performance analysis for uplink SCMA based on CP-free OFDM
    Li ZHOU, Xiqing LIU
    2021, 37(6):  23-32.  doi:10.11959/j.issn.1000-0801.2021132
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    A typical sparse code multiple access (SCMA) system utilizes orthogonal frequency division multiplexing (OFDM) technology with cyclic prefix (CP) to combat multipath fading in wireless channels.Therefore, its capacity is reduced by the CP-insertion.To address this issue, the SCMA scheme based on CP-free OFDM using the time domain precoding (TDP) algorithm was proposed and the proposed scheme was termed as TDP-OFDM SCMA.The transceiver structure was designed, and the capacity plus the bit error rate (BER) performances under various channels with different overload rates and with channel estimation errors were evaluated via the simulations.Also, the power consumption problem in TDP-OFDM SCMA was discussed.The simulation results show that under the same overload rate, the capacity of TDP-OFDM SCMA can be increased by up to 25% if compared with the SCMA based on CP-OFDM.

    Terahertz wireless networking: principles, status and challenges
    Tianhang ZHOU, Chuang YANG, Zile LIU, Mugen PENG, Li YU
    2021, 37(6):  33-44.  doi:10.11959/j.issn.1000-0801.2021122
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    To achieve huge capacity, terahertz communication has become an important technical option for 6G.Application and performance requirements of terahertz communication in typical indoor and outdoor scenarios were introduced emphatically.Then, based on the requirements of terahertz wireless networking, the research progress of key technologies such as topology design, media access control (MAC) layer protocol and neighbor discovery were summarized in detail.Last but not least, the challenges of terahertz wireless networking were discussed, and the possible future research directions were described.

    Analysis and status of the scattering channel model for ultraviolet communications
    Renzhi YUAN, Zhifeng WANG, Mugen PENG
    2021, 37(6):  45-54.  doi:10.11959/j.issn.1000-0801.2021126
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    Due to its unique features such as high local security, low background noise, and non-light-of-sight communication, the ultraviolet communication, which uses the light wave of “solar blind” wavelength (200~280 nm) as the information carrier, becomes a promising optical communication technique for applications in both secure communications and internet of vehicles and so on.The scattering channel models were classified into analytical channel models and stochastic channel models according to their different computational efficiencies.The research of the first three scattering orders in analytical channel models and the Monte-Carlo simulation model and Monte-Carlo integration model in stochastic channel models were mainly focused on.Some future research directions for the scattering channel model of ultraviolet communications were also provided.

    Resource management in sliced networks with mobile edge computing for B5G and 6G
    Qian SUN, Lin TIAN, Yiqing ZHOU, Chen FENG, Yuanyuan WANG, Jihua ZHOU
    2021, 37(6):  55-65.  doi:10.11959/j.issn.1000-0801.2021128
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    With the time-delay sensitive compute-intensive tasks growing exponentially, 5G and future 6G mobile cellular communication networks will form differentiated network slices with edge computing resource to service the multiple communication services.To achieve this, the wireless frequency and edge computing resources will be shared among the network slices, thus the efficient management of the resources is of great importance.The demands of resources management in the life duration of the network slice was analyzed.Then the research progress of the corresponding technologies for slices, i.e., access control, resources allocation and stimulating cooperation among terminals, were summarized.And the open research issue was given.Thus, the resources are managed efficiently for the slices with edge computing resource.

    Software defined intelligent satellite-terrestrial integrated wireless network
    Shuo YUAN, Yijing REN, Zeyu WANG, Yaohua SUN, Mugen PENG
    2021, 37(6):  66-77.  doi:10.11959/j.issn.1000-0801.2021123
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    With the superiorities of providing network services for all scenarios of three-dimensional space, air, ground, and ocean, and satisfying the future network differential requirements on all services, the satellite-terrestrial integrated network (STIN) has become a hot spot in the development of 6G.Firstly, the current research development of the low-orbit satellite constellation and STIN were reviewed, and the challenges faced by the integrated satellite-terrestrial networking were discussed.Then, the software defined intelligent system architecture of the integrated satellite-terrestrial wireless network based on distributed SDN controllers was proposed to address the characteristics of STIN such as the complex architecture, high dynamic of network topology, the heterogeneity of network devices and protocols, which facilitated efficient satellite-terrestrial collaborative network management and control.In the end, the key techniques of the satellite-terrestrial flexible and reconfigurable collaborative networking were outlined, and the future development were presented.

    Access and mobility management technologies for 6G satellite communications network
    Xiaowen WU, Xiang LING, Lidong ZHU, Zhenfeng JIAO, Jian CHENG, Bo YANG
    2021, 37(6):  78-90.  doi:10.11959/j.issn.1000-0801.2021131
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    Analsisand outlook for satellite communication access and mobility management technology in 6G network was presented.Firstly, the access technology of current global representative satellite mobile communications system was introduced, as well as the international standardization organization research status of 5G NR satellite access technology.According to the challenges for 6G satellite communications network access, some solutions regarding to 6G satellite communications access were proposed respectively from the aspects of extremely simple access, extremely intelligent access.Furthermore, according to the demand of massive terminals handoff in the high dynamic scenario of 6G satellite communications, the flexible handoff scheme based on cloud channel technology, which supported batch massive terminals mobility management for across satellites and beams, was proposed.

    Principle and future trends of indoor positioning in 6G
    Xiaoyang WAN, Yaohua SUN, Zeyu WANG
    2021, 37(6):  91-104.  doi:10.11959/j.issn.1000-0801.2021118
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    For supporting location based differentiated services better, 6G has a more stringent requirement on high-precision positioning.Firstly, the principles, characteristics, advantages and disadvantages of the existing indoor positioning techniques were introduced.Then, indoor positioning systems integrating multiple techniques were discussed to overcome the drawbacks of using only a single technique.Moreover, the advances in cooperative positioning systems involving multi-devices and multi-networks were presented with the summary and analysis of centralized and distributed implementation architectures.Finally, the opportunities and challenges faced by 6G indoor positioning were pointed out.

    Research and Development
    A secure transmission method based on cooperative jamming for correlated main and wiretap channels
    Sai XU, Shuai HAN, Weixiao MENG
    2021, 37(6):  105-114.  doi:10.11959/j.issn.1000-0801.2021121
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    A secure transmission method was proposed based on cooperative jamming to reduce the secrecy loss caused by the correlation between main and wiretap channels and to improve the secrecy.Considering that the existing methods of cooperative jamming focused on the case of independent main and wiretap channels, the achievable secrecy performance was not satisfactory.In view of this, a cooperative jamming method for correlated main and wiretap channels was proposed.Based on the model of cooperative jamming under correlated main and wiretap channels, the secrecy rate maximization under secrecy outage constraint was formulated.Then, the norm bounding approach and the Bernstein-type inequality approach were employed to approximately transform the probabilistic constraint into a deterministic form, and a safe approximate solution of beamforming vector and AN covariance matrix was obtained.Simulation results show that the proposed method can reduce the secrecy loss under high correlation.

    Communication between nodes in backscatter-assisted wireless powered communication network
    Jie TAO, Haijiang GE, Minyuan WU, Qike SHAO, Kaikai CHI
    2021, 37(6):  115-124.  doi:10.11959/j.issn.1000-0801.2021120
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    At present, there is almost no design on information transmission between the nodes in wireless powered communication network.The high-throughput information transmission between the nodes in backscatter assisted wireless powered communication network was studied.A scheme was proposed which consisted of backscattering/energy transmission phase and active communication phase.The maximum throughput was modeled as a convex optimization problem.Then, based on the relationship between the total backscatter communication duration and the threshold of node energy capture duration, the problem was decomposed into several sub problems that only need to optimize two backscatter durations.An efficient two-level golden section search algorithm was designed to solve the sub problems, and the optimal solution of the original problem was obtained from the optimal solutions of the sub problems.Simulation results show that, compared with pure active communication scheme and pure backscatter communication scheme, the proposed scheme can effectively improve the throughput.

    Application on text classification of telecom user complaints based on GRW and FastText model
    Jin ZHAO, Xiaojun YANG
    2021, 37(6):  125-131.  doi:10.11959/j.issn.1000-0801.2021125
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    With the widespread application of neural network, the application of neural network to natural language processing text classification problems has become an effective solution.The customer service center of telecom operator collected user complaint information from multiple channels.In order to automatically classify the complaint text information and assign it to the specific responsible department for processing and reply, enhancing customer perception further, a textclassification method based on GRW and FastTextmodel was proposed.Firstly, the GRW model was used to select the features of the complaint text, extract effective feature words, and then a user complaint text classification method based on FastText model was constructed.Experiments on public datasets and a complaint text data by one of telecom company show that the text classification method based on GRW and FastText model is better than naive Bayes, bidirectional LSTM and Bert pre-trained model in accuracy, Kappa coefficient and Hamming loss.

    Topology design and capacity planning of wide-area network based on delay constraint
    Xiaoqing XU, Hong TANG, Ke RUAN, Juan WU, Xiaojun LIU
    2021, 37(6):  132-141.  doi:10.11959/j.issn.1000-0801.2021137
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    In order to optimize network performance and reduce construction cost, the topology design and dimensioning problems in wide-area network planning were investigated based on delay constraint with the use of linear programming (LP) and heuristic greedy-drop algorithm.Firstly, demands’ weights were considered and LP was exploited with given paths to solve the capacity expansion problems of minimum delay and minimum delay with minimum cost.Secondly, greedy-drop algorithm was applied and candidate edges were removed from full mesh topology according to the global normalized delay increments.Thus, new added edges to satisfy the delay constraint were determined.Moreover, the combination of LP and greedy-drop algorithm was proposed to determine new added edges and capacity expansion of the delay-constraint scenario with minimum cost.The results turn out that the proposed algorithms are effective to solve the problems of topology design and capacity planning in wide-area network planning targeting delay optimization.

    Topic: 5G Network Construction Promotes the Transformation of Digital Intelligence
    Methodology of 5G network planning and design for vertical industry with product solutions
    Ziyu XIAO, Hongwei LV, Cun ZHAO, Yan HAN, Jian SU
    2021, 37(6):  143-149.  doi:10.11959/j.issn.1000-0801.2021136
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    The methodology of 5G toB network planning was discussed.The current situation of 5G network was introduced and the challenges of network planning were analyzed for vertical industry requirements with diversification and customization.Then the methodology of 5G toB scenario-oriented planning and design was put forward, based on the network technology system, oriented the future business layout of the industry, focused on the planning ability of accurate identification, on-demand delivery and network elasticity, so as to achieve the goal of on-demand planning and agile network construction.At the same time, on the basis of methodology, an end-to-end planning and design platform algorithm was proposed to achieve the collaborative planning for toC (public network) and toB (vertical network).

    Key technologies and introduction strategies for 3GPP R16 oriented evolution of 5G core network
    Xu YANG, Ziyu XIAO, Ming ZHANG, Yongping SHAO
    2021, 37(6):  150-159.  doi:10.11959/j.issn.1000-0801.2021133
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    5G core network has been deployed based on 3GPP R15 standard.Firstly, the progress of 3GPP standard and the overall progress of end-to-end industry of 5G core network were reviewed, and the main research directions and contents of R16 based on the evolution of 3GPP R16 standard were summarized, Then, the key technology research and deployment strategy analysis were carried out for some key issues with relatively high priority in the follow-up business.Finally, the overall summary and analysis of the follow-up 5G core network business evolution deployment direction were carried out, and the preliminary deployment strategy suggestions were put forward, so as to provide reference for the follow-up business evolution and construction of 5G SA core network.

    Architecture and key technologies of 5G converged charging system
    Lei QI, Huiqiong GU, Hao ZHU, Xu CHEN
    2021, 37(6):  160-166.  doi:10.11959/j.issn.1000-0801.2021134
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    To satisfy 5G network construction and business development, co-based business operations and support become an important goal of 5G support network, and the deployment strategy need to be planned.The changes in the network were analyzed, the converged charging system framework based on micro servers was designed, and the functional architecture such as billing data services and billing gateway was proposed.The key technologies such as message processing and smart quotas were introduced, multi-dimensional charging capabilities were analyzed, and the network evolution strategy was described.Applications and solutions of charging frameworks for different business scenarios were proved, a blueprint for the evolution of the CCS was provided, and the business innovation and operations were prepared.

    Scheme of 5G message system co-construction and sharing
    Xiaodan NIU, Chen XU, Jingxia CHEN, Xiangfei JIAO
    2021, 37(6):  167-173.  doi:10.11959/j.issn.1000-0801.2021130
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    With the joint release of “5G message white paper” on April 8, 2020, China’s three major telecom operators have reached a consensus that they will comprehensively upgrade the short message service in the 5G era and create a new business form of 5G message.On the basis of emphasizing the construction of 5G message system, the difficulty of 5G message system carrying the message services of three operators was analyzed under different co construction scope from the technical perspectives of network architecture, interface interoperability and security risk, and finally recommends the construction scheme of co-construction of MaaP, so as to meet the 5G message services development demands of three operators with less implementation cost.

    Construction ideas of the middle platform capability operation center of telecom operators
    Xin GU, Xiaorong NI, Zhao LIU, Xiaonan FANG, Yuemeng LI
    2021, 37(6):  174-182.  doi:10.11959/j.issn.1000-0801.2021129
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    The architecture and function of the middle platform capability operation center of telecom operators were analyzed, and the registration, encapsulation, and access control strategy of service and capability were expounded.The construction ideas of the service governance system and the capacity collaboration were discussed,and the evolution path of the middle platform capacity operation center was proposed.The proposed idea provides a valuable reference for telecom operator to build the system of middle platform.

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