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    15 June 2023, Volume 39 Issue 7
    Research and Development
    A low complexity pilot assignment algorithm based on user polar coordinates in CF-mMIMO systems
    Shao GUO, Peng PAN, Yaozong FAN
    2023, 39(7):  1-10.  doi:10.11959/j.issn.1000-0801.2023120
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    Absrtact: In order to reduce the pilot contamination in the cell-free massive multi-input multi-output (MIMO) system, a low complexity pilot assignment algorithm based on user polar coordinates was proposed.Firstly, a Gaussian weighted density algorithm was proposed to determine a centroid as the polar coordinates center point in the system coverage area, then pre-assigned the pilot in order according to the angular coordinates, so that users who reused the same pilot had a greater probability of having a longer distance, and henced reduce the pilot contamination.A low complexity distance detection algorithm was then proposed to ensure that the user spacing between any two users multiplexing the same pilot was greater than the threshold.The simulation results show that the proposed pilot assignment algorithm effectively reduce pilot contamination, improve the uplink throughput of 95% users of the system, and achieve a good compromise between performance and complexity.

    NR-U and Wi-Fi spectrum sharing for quality guaranteeing of power services
    Junpeng LIU, Weiwei XIA, Han LIU, Chenglin XIU, Feng YAN, Lianfeng SHEN
    2023, 39(7):  11-22.  doi:10.11959/j.issn.1000-0801.2023148
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    To alleviate the shortage of 5G licensed spectrum resources, using unlicensed spectrum has become an important solution.With the large-scale access of power terminals, NR-U and Wi-Fi spectrum sharing for power services quality guaranteeing has become an important research hotspot.Firstly, an NR-U uplink transmission mechanism was proposed, which ensured the average throughput of Wi-Fi users and realized the data uplink transmission of power service terminals.In addition, a resource optimization algorithm for joint transmission time and subcarrier allocation (TTSA) was proposed to ensure the quality of service (QoS) of various types of power services and maximize the total throughput of terminals.The optimization problem was decoupled, and proximal policy optimization (PPO) was used to allocate subcarriers to terminals.The simulation results show that compared with the existing algorithms, the proposed resource optimization algorithm for TTSA has superior performance in guaranteeing the service quality of power services and maximizing the total terminals throughput.

    5G beamforming weight optimization method based on particle swarm optimization algorithm
    Jianbin WANG, Hengjun WANG, Song WU, Zhenkai WANG
    2023, 39(7):  23-34.  doi:10.11959/j.issn.1000-0801.2023146
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    In order to solve the problems of insufficient indoor 5G signal coverage and difficulty in optimization of high-rise buildings, the 5G beamforming weight optimization method based on particle swarm optimization (PSO) algorithm was proposed.Decoupling and reducing the network dimension into multiple subnet slices by collecting the data reported by the terminal, and the single cell weight database was planned and simulated to create the multi-cells weights group and fitness function.Finally, the PSO algorithm was adopted to obtain the local optimal weight group of the multi-cells.The test results show that the reference signal receiving power (RSRP) is improved by 8.7%, the signal to interference plus noise ratio (SINR) is improved by 17.5%, the downlink throughput is promoted by 27.3% together.The proposed method has the advantages of low cost, high efficiency and intelligence, and can significantly improve the user perception in high-rise buildings.

    Outage performance of multi-relay collaborative NOMA systems supporting multiple multicast services
    Yifei CHU, Xinjie YANG
    2023, 39(7):  35-45.  doi:10.11959/j.issn.1000-0801.2023135
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    A cooperative non-orthogonal multiple access (NOMA) system was proposed to support unicast primary user and multiple multicast services based on multiple relays strategy.Under the Rayleigh channel, the secondary user with the best channel condition from each multicast group was selected as full-duplex relay to decode and forward the unicast primary user’s signal, and the primary user employed the maximum ratio combining (MRC) technique to improve the signal to interference and noise ratio (SINR).The closed-form expressions for the outage probability of primary user in full-duplex and half-duplex modes with multi-relay simultaneous forwarding (MRSF) and optimal relay forwarding (ORF) were derived and verified by Monte Carlo simulations.The results verify that full-duplex relay outperforms half-duplex relay scheme.Furthermore, with same number of multicast groups, the MRSF strategy effectively improve the unicast primary user outage performance, in comparison with ORF strategy, when the number of multicast groups increases, the improvement becomes more significant.

    Research and Development
    Research on filter-based adversarial feature selection against evasion attacks
    Qimeng HUANG, Miaomiao WU, Yun LI
    2023, 39(7):  46-58.  doi:10.11959/j.issn.1000-0801.2023140
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    With the rapid development and widespread application of machine learning technology, its security has attracted increasing attention, leading to a growing interest in adversarial machine learning.In adversarial scenarios, machine learning techniques are threatened by attacks that manipulate a small number of samples to induce misclassification, resulting in serious consequences in various domains such as spam detection, traffic signal recognition, and network intrusion detection.An evaluation criterion for filter-based adversarial feature selection was proposed, based on the minimum redundancy and maximum relevance (mRMR) method, while considering security metrics against evasion attacks.Additionally, a robust adversarial feature selection algorithm was introduced, named SDPOSS, which was based on the decomposition-based Pareto optimization for subset selection (DPOSS) algorithm.SDPOSS didn’t depend on subsequent models and effectively handles large-scale high-dimensional feature spaces.Experimental results demonstrate that as the number of decompositions increases, the runtime of SDPOSS decreases linearly, while achieving excellent classification performance.Moreover, SDPOSS exhibits strong robustness against evasion attacks, providing new insights for adversarial machine learning.

    Design of OFDM-IM system based on IRS-assisted
    Mengmeng ZHAO, Liming HE, Fangfang LIU
    2023, 39(7):  59-67.  doi:10.11959/j.issn.1000-0801.2023136
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    Index modulation (IM) and intelligent reflecting surface (IRS) are emerging mobile communication technologies.In order to improve the reliability of traditional orthogonal frequency division multiplexing (OFDM) system, an orthogonal frequency division multiplexing with index modulation (OFDM-IM) system based on IRS-assisted was designed.Firstly, the OFDM-IM system was designed by using spatial modulation and frequency domain modulation to increase the Euclidean distance between subcarriers.Then, by establishing an equivalent circuit model, a practical IRS model was obtained.Finally, an alternating optimization algorithm was used to optimize the active transmission power of the access point (AP) and passive beamforming of the IRS jointly.The simulation results show that compared to the benchmark scheme, the symbol error rate (SER) or bit error rate (BER) of the OFDM-IM system based on IRS-assisted can be reduced by 60%~90%.Especially in the case of high signal-to-noise ratio, the SER or BER of the system can reach 1.0×10-6, which indicates that the introduction of IM and IRS technologies has optimized the link transmission quality of end-to-end communication system.In addition, based on the IRS-assisted OFDM-IM system as the standard, simulations are conducted to demonstrate the impact of various parameters from the IRS model and IM.It concludes that the parameters in the system should be selected reasonably according to channel state information (CSI).

    Physical layer security of MIMO wireless systems with adaptive modulation
    Hui LI, Guangqiu LI, Yancui LUO, Huizhi LIU
    2023, 39(7):  68-79.  doi:10.11959/j.issn.1000-0801.2023141
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    To solve the problems of low spectral efficiency and poor performance of physical layer security (PLS) in single-input single-output (SISO) wireless systems with adaptive modulation in the presence of an active eavesdropper, multiple-input multiple-output (MIMO) wireless systems with secure adaptive modulation (SAM) were proposed.The design idea was to improve the spectral efficiency of the main channel by antenna diversity technology, which used the transmit antenna selection (TAS) at the transmitter and the maximal ratio combining (MRC) at the legitimate receiver to improve the signal-to-noise ratio.Simultaneously, the PLS of the legitimate receiver was guaranteed by limiting the bit error rate of the active eavesdropper so that it could not demodulate the confidential information from the main channel.With the joint constraints of the average transmission power and PLS, the optimal switching thresholds and the analytical expressions of spectral efficiency and the eavesdropper’s average bit error rate of the SAM-MIMO systems were derived.Numerical and simulation results show that SAM systems using TAS/MRC technology can not only improve the spectral efficiency of the main channel, but also ensure the PLS against the active eavesdropper, compared with the SAM-SISO systems.

    A network traffic classification method based on random forest and improved convolutional neural network
    Bensheng YUN, Xiaoya GAN, Yaguan QIAN
    2023, 39(7):  80-89.  doi:10.11959/j.issn.1000-0801.2023138
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    In order to improve the efficiency and reduce the complexity of network traffic classification model, a classification method based on random forest and improved convolutional neural network was proposed.Firstly, the random forest was used to evaluate the importance of each feature of network traffic, and the feature was selected according to the importance ranking.Secondly, AdamW optimizer and triangular cyclic learning rate were adopted to optimize the convolutional neural network classification model.Then, the model was built on Spark cluster to realize the parallelization of model training.Adopting triangular cyclic learning rate with constant cycle amplitude, the experimental results of selecting 1 024, 400, 256 and 100 most important features as input show that the model accuracy is improved to 97.68%, 95.84%, 95.03% and 94.22%, respectively.The 256 most important features were selected and the experimental results based on adopting different learning rates show that the learning rate with half the cycle amplitude works best, the accuracy of the model is improved to 95.25%, and training time of the model is reduced by nearly half.

    Cloud architecture data center network abnormal traffic filtering algorithm based on improved grey clustering algorithm
    Xuefeng ZHOU, Qiang XU, Yanting TAN, Jiayi LANG, Hang JING, Zhiqiang ZHAO
    2023, 39(7):  90-98.  doi:10.11959/j.issn.1000-0801.2023137
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    To avoid abnormal traffic affecting the safe operation of the cloud architecture data center network, it was necessary to filter the abnormal traffic of the cloud architecture data center network.The difficulty of filtering abnormal traffic varies under different signal-to-noise ratios and channel conditions.In order to ensure the filtering effect of abnormal traffic under different filtering conditions, a cloud architecture data center network abnormal traffic filtering algorithm based on improved grey clustering algorithm was proposed.A network traffic transmission model was built for cloud architecture data centers through time-frequency analysis, and network traffic sequences were collected.Weighted generalized distance was introduced to improve the grey clustering algorithm, and the improved grey clustering algorithm was used to calculate the optimal clustering results of network traffic sequence features, achieving traffic sequence feature extraction.The principal component eigenvalues of traffic sequence features were obtained through principal component analysis, two subspaces were constructed, and traffic features were mapped in a matrix manner to the two subspaces.Abnormal traffic was filtered based on the square prediction error of the mapping period vector and the threshold calculation results.The experimental results show that this algorithm can achieve feature extraction of data center network traffic sequences through clustering, effectively filtering abnormal traffic under different signal-to-noise ratios and channel conditions.When the signal-to-noise ratio of the network was 25 dB and the traffic was transmitted in a Gaussian channel, the filtering effect of abnormal traffic was more prominent.

    A fast block partitioning algorithm for VVC intra coding based on depthwise separable convolution
    Zhen YE, Guoxiang WANG, Junfeng SONG, Haokun LIU, Tiansong LI
    2023, 39(7):  99-108.  doi:10.11959/j.issn.1000-0801.2023132
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    The joint video exploration team (JVET) proposed versatile video coding (VVC) as a new video coding standard, and its quadtree plus multi-type tree (QTMTT) partition structure brings effective coding performance improvements.However, it brings about a sharp increase in encoding complexity, which greatly increases the encoding time.In order to solve the above problems, a fast block partitioning algorithm for VVC intra coding based on depthwise separable convolution was proposed.The pixel of coding unit (CU) was used as input, and the texture information feature of CU was extracted through depth-separable convolution.Therefore, accurate partition mode prediction was realized in the QTMT structure in VVC, and the complexity of the encoder was reduced by skipping low-probability partition modes.Experimental results show that the proposed algorithm saves 18% to 48% of encoding time on the VTM 15.2, and only brings an average performance loss of 0.15%.And the additional complexity brought by the lightweight depthwise separable convolution calculation is also negligible.

    Gesture recognition based on flexible solar cells and ultrathin hydrogel film
    Rucheng WU, Wenbo DING, Xiaomin XU, Linqi SONG, Weitao XU
    2023, 39(7):  109-115.  doi:10.11959/j.issn.1000-0801.2023143
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    Daily life involves various gestures, and combining these with smart wearable devices is crucial for improving quality of life.One effective solution to the challenges of gesture recognition and device energy consumption isutilizing the photoelectric conversion characteristics of solar energy-related devices.The data of five commonly used gestures were collected in the research of the combination of flexible solar cells and gesture recognition.Z-Score, low-pass filter, sliding window techniques for signal processing were applied, and successfully achieved 100% predicted accuracy using random forest, support vector machine and neural network algorithms even with small samples which showed that this method had significant advantages in the application of gesture recognition.

    Blockchain and credibility function based chain storage method of electronic encrypted information
    Ting ZHOU
    2023, 39(7):  116-123.  doi:10.11959/j.issn.1000-0801.2023147
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    To optimize the proportion of encrypted information storage space in the blockchain and improve the speed of online storage, a design method for electronic encrypted information online storage based on blockchain and credibility function was proposed.An information encryption classification model based on blockchain and credibility function was established, and a traceability voucher judgment function was obtained.Proxy re-encryption was performed on electronic information.The storage capacity of the cluster was calculated, and encrypted ciphertext was used to directly match the access structure tree.Subject credibility and object credibility were distinguished, electronic encrypted information was classified based on the credibility function, and an electronic encrypted information uplink storage method was designed.The experimental results show that after applying the proposed method, when the number of files is between 1 000 and 10 000, the data storage speed is the fastest, and the storage space proportion and storage speed are greatly optimized.

    Review
    Review of optimal resource allocation scheme for 5G Internet of vehicles
    Chengyu ZHENG, Yiting YAO, Hongbin LIANG, Lei WANG
    2023, 39(7):  124-138.  doi:10.11959/j.issn.1000-0801.2023139
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    As a necessary part of the development of intelligent transportation, the Internet of vehicles (IoV) accelerates the construction of intelligent transportation infrastructure in China, which plays an important practical significance to the construction of smart city.The number of vehicles and the massive data generated by them make the transmission conflict rate between communication vehicle nodes rise significantly, and communication resources and computing resources are in short supply.Therefore, the effective resource allocation scheme can ensure the communication quality of vehicle networking, thereby improving the reliability of vehicle communication and reducing the time delay.Firstly, the influence of IoV on the development status of intelligent transportation at home and abroad and the bottlenecks of the development of IoV were analyzed.Secondly, in terms of the efficiency and safety of smart transportation, the resource allocation problem of IoV was analyzed.Thirdly, by summarizing the advantages of 5G technology, the contribution of 5G in the optimization allocation and management of vehicle networking resources was analyzed.Finally, combined with the application of artificial intelligence technology in the context of Internet of vehicles communication, computing and storage resource optimization allocation and management, the development prospect of intelligent transportation based on 5G+V2X was proposed.

    Engineering and Application
    Optimization model of random load balancing of heterogeneous nodes in complex buildings
    Wenlei GUO
    2023, 39(7):  139-148.  doi:10.11959/j.issn.1000-0801.2023145
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    In order to improve the load balancing of a complex building complex IoT and maintain its stable operation, a random load balance optimization model for non-uniformly distributed nodes in a complex building complex IoT was proposed.Sensor devices were deployed and wireless networks were accessed in complex building clusters to build the Internet of things for complex building clusters.The distribution location of each node in the Internet of things environment was determined, and random load data of non-uniformly distributed nodes was collected and integrated.The priority of non-uniformly distributed nodes was calculated using the IALBR routing protocol.By generating scheduling links and calculating the scheduling amount, the node load balancing scheduling task of the model was completed, and the load balancing of the Internet of things was optimized.The experimental results show that compared with traditional models, the average value of the load balance index of nodes under the design model is 0.002.The application of the design model effectively reduces the congestion probability of the Internet of things and improved network throughput.

    A cost-effective and miniaturized SPN deployment strategy for group customer dedicated lines
    Cheng CHEN, Han WANG, Shuchong NAN
    2023, 39(7):  149-155.  doi:10.11959/j.issn.1000-0801.2023142
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    With the change of networking mode in the evolution of 5G network, SPN is faced with the limitations of ubiquitous coverage, which leads to the long access distance of the passenger dedicated line customers.Based on the operator's benefit-oriented construction idea, in order to solve the network benefit problem in the process of further deepening SPN coverage.Three sink deployment strategies were proposed for different scenarios, taking the empirical value cost of typical configurations as an example.By building a simulation environment, Gaussian mixture model was used to simulate the distribution characteristics of group customers, and the relationship between the total number of customers, the number of sinking SPN devices and customer coverage in sparse, common and dense scenarios were analyzed, and the network benefits of different sinking strategies were tested.The simulation results show that strategy 3 only faces the area coverage with high sinking efficiency when the total number of customers is 600, and the maximum coverage rate can only reach 55.27%.However, with the increase of customer points, the maximum coverage rate of strategy 3 can reach 82.71%, which has obvious coverage advantages.At the same time, the average number of sunk equipment can cover the highest number of customers, realizing the high coverage ability under the condition of ensuring high efficiency.

    Super-resolution reconstruction technology and its application on intelligent terminal device
    Guqiao ZHU, Chao JIANG, Yuye XU
    2023, 39(7):  156-165.  doi:10.11959/j.issn.1000-0801.2023150
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    The development history of super-resolution reconstruction technology and its typical approaches were briefly introduced.An implementation solution of super-resolution reconstruction was proposed on one kind of intelligent terminal device.The image super-resolution approaches implemented by interpolation algorithms and deep learning algorithms were experimented and simulated, and their results on terminal’s processing performance and images’ quality of experience were evaluated and analyzed.The suggestions on appropriate scenarios of super-resolution implemented by the intelligent terminal device were proposed.Furthermore, some typical cases of super-resolution reconstruction technology in the fields of entertainment video services and home surveillance services were discussed.The possible research direction and the trend of convergence of this technology and relevant image processing technologies were also prospected.

Copyright Information
Authorized by: China Association for Science and Technology
Sponsored by: China Institute of Communications
Posts and Telecom Press Co., Ltd.
Publisher: Beijing Xintong Media Co., Ltd.
Editor-in-Chief: Chen Shanzhi
Editorial Director: Li Caishan
Address: F2, Beiyang Chenguang Building, Shunbatiao No.1 Courtyard, Fengtai District, Beijing, China
Postal Code: 100079
Tel: 010-53879277
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E-mail: dxkx@ptpress.com.cn
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ISSN 1000-0801
CN 11-2103/TN
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