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Differential Quasi-Yagi Antenna and Array ZHU Zhihao, ZHANG Yueping ZTE Communications    2023, 21 (3): 37-44.   DOI: 10.12142/ZTECOM.202303006 Abstract （216）   HTML （12）    PDF （2723KB）（174）       Knowledge map    Save A novel differential quasi-Yagi antenna is first presented and compared with a normal single-ended counterpart. The simulated and measured results show that the differential quasi-Yagi antenna outperforms the conventional single-ended one. The differential quasi-Yagi antenna is then used as an element for linear arrays. A study of the coupling mechanism between the two differential and the two single-ended quasi-Yagi antennas is conducted, which reveals that the TE0 mode is the dominant mode, and the driver is the decisive part to account for the mutual coupling. Next, the effects of four decoupling structures are respectively evaluated between the two differential quasi-Yagi antennas. Finally, the arrays with simple but effective decoupling structures are fabricated and measured. The measured results demonstrate that the simple slit or air-hole decoupling structure can reduce the coupling level from -18 dB to -25 dB and meanwhile maintain the impedance matching and radiation patterns of the array over the broad bandwidth. The differential quasi-Yagi antenna should be a promising antenna candidate for many applications. Table and Figures | Reference | Related Articles | Metrics

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Boundary Data Augmentation for Offline Reinforcement Learning SHEN Jiahao, JIANG Ke, TAN Xiaoyang ZTE Communications    2023, 21 (3): 29-36.   DOI: 10.12142/ZTECOM.202303005 Abstract （192）   HTML （20）    PDF （1865KB）（363）       Knowledge map    Save Offline reinforcement learning (ORL) aims to learn a rational agent purely from behavior data without any online interaction. One of the major challenges encountered in ORL is the problem of distribution shift, i.e., the mismatch between the knowledge of the learned policy and the reality of the underlying environment. Recent works usually handle this in a too pessimistic manner to avoid out-of-distribution (OOD) queries as much as possible, but this can influence the robustness of the agents at unseen states. In this paper, we propose a simple but effective method to address this issue. The key idea of our method is to enhance the robustness of the new policy learned offline by weakening its confidence in highly uncertain regions, and we propose to find those regions by simulating them with modified Generative Adversarial Nets (GAN) such that the generated data not only follow the same distribution with the old experience but are very difficult to deal with by themselves, with regard to the behavior policy or some other reference policy. We then use this information to regularize the ORL algorithm to penalize the overconfidence behavior in these regions. Extensive experiments on several publicly available offline RL benchmarks demonstrate the feasibility and effectiveness of the proposed method. Table and Figures | Reference | Related Articles | Metrics

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Double Deep Q-Network Decoder Based on EEG Brain-Computer Interface REN Min, XU Renyu, ZHU Ting ZTE Communications    2023, 21 (3): 3-10.   DOI: 10.12142/ZTECOM.202303002 Abstract （150）   HTML （14）    PDF （1551KB）（200）       Knowledge map    Save Brain-computer interfaces (BCI) use neural activity as a control signal to enable direct communication between the human brain and external devices. The electrical signals generated by the brain are captured through electroencephalogram (EEG) and translated into neural intentions reflecting the user's behavior. Correct decoding of the neural intentions then facilitates the control of external devices. Reinforcement learning-based BCIs enhance decoders to complete tasks based only on feedback signals (rewards) from the environment, building a general framework for dynamic mapping from neural intentions to actions that adapt to changing environments. However, using traditional reinforcement learning methods can have challenges such as the curse of dimensionality and poor generalization. Therefore, in this paper, we use deep reinforcement learning to construct decoders for the correct decoding of EEG signals, demonstrate its feasibility through experiments, and demonstrate its stronger generalization on motion imaging (MI) EEG data signals with high dynamic characteristics. Table and Figures | Reference | Related Articles | Metrics

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Towards Near-Field Communications for 6G: Challenges and Opportunities LIU Mengyu, ZHANG Yang, JIN Yasheng, ZHI Kangda, PAN Cunhua ZTE Communications    2024, 22 (1): 3-15.   DOI: 10.12142/ZTECOM.202401002 Abstract （129）   HTML （13）    PDF （2702KB）（284）       Knowledge map    Save Extremely large-scale multiple-input multiple-output (XL-MIMO) and terahertz (THz) communications are pivotal candidate technologies for supporting the development of 6G mobile networks. However, these techniques invalidate the common assumptions of far-field plane waves and introduce many new properties. To accurately understand the performance of these new techniques, spherical wave modeling of near-field communications needs to be applied for future research. Hence, the investigation of near-field communication holds significant importance for the advancement of 6G, which brings many new and open research challenges in contrast to conventional far-field communication. In this paper, we first formulate a general model of the near-field channel and discuss the influence of spatial nonstationary properties on the near-field channel modeling. Subsequently, we discuss the challenges encountered in the near field in terms of beam training, localization, and transmission scheme design, respectively. Finally, we point out some promising research directions for near-field communications. Table and Figures | Reference | Related Articles | Metrics

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Log Anomaly Detection Through GPT-2 for Large Scale Systems JI Yuhe, HAN Jing, ZHAO Yongxin, ZHANG Shenglin, GONG Zican ZTE Communications    2023, 21 (3): 70-76.   DOI: 10.12142/ZTECOM.202303010 Abstract （115）   HTML （9）    PDF （537KB）（226）       Knowledge map    Save As the scale of software systems expands, maintaining their stable operation has become an extraordinary challenge. System logs are semi-structured text generated by the recording function in the source code and have important research significance in software service anomaly detection. Existing log anomaly detection methods mainly focus on the statistical characteristics of logs, making it difficult to distinguish the semantic differences between normal and abnormal logs, and performing poorly on real-world industrial log data. In this paper, we propose an unsupervised framework for log anomaly detection based on generative pre-training-2 (GPT-2). We apply our approach to two industrial systems. The experimental results on two datasets show that our approach outperforms state-of-the-art approaches for log anomaly detection. Table and Figures | Reference | Related Articles | Metrics

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Robust Beamforming Under Channel Prediction Errors for Time-Varying MIMO System ZHU Yuting, LI Zeng, ZHANG Hongtao ZTE Communications    2023, 21 (3): 77-85.   DOI: 10.12142/ZTECOM.202303011 Abstract （114）   HTML （9）    PDF （1578KB）（86）       Knowledge map    Save The accuracy of acquired channel state information (CSI) for beamforming design is essential for achievable performance in multiple-input multiple-output (MIMO) systems. However, in a high-speed moving scene with time-division duplex (TDD) mode, the acquired CSI depending on the channel reciprocity is inevitably outdated, leading to outdated beamforming design and then performance degradation. In this paper, a robust beamforming design under channel prediction errors is proposed for a time-varying MIMO system to combat the degradation further, based on the channel prediction technique. Specifically, the statistical characteristics of historical channel prediction errors are exploited and modeled. Moreover, to deal with random error terms, deterministic equivalents are adopted to further explore potential beamforming gain through the statistical information and ultimately derive the robust design aiming at maximizing weighted sum-rate performance. Simulation results show that the proposed beamforming design can maintain outperformance during the downlink transmission time even when channels vary fast, compared with the traditional beamforming design. Table and Figures | Reference | Related Articles | Metrics

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Statistical Model of Path Loss for Railway 5G Marshalling Yard Scenario DING Jianwen, LIU Yao, LIAO Hongjian, SUN Bin, WANG Wei ZTE Communications    2023, 21 (3): 117-122.   DOI: 10.12142/ZTECOM.202303015 Abstract （112）   HTML （13）    PDF （1448KB）（57）       Knowledge map    Save The railway mobile communication system is undergoing a smooth transition from the Global System for Mobile Communications-Railway (GSM-R) to the Railway 5G. In this paper, an empirical path loss model based on a large amount of measured data is established to predict the path loss in the Railway 5G marshalling yard scenario. According to the different characteristics of base station directional antennas, the antenna gain is verified. Then we propose the position of the breakpoint in the antenna propagation area, and based on the breakpoint segmentation, a large-scale statistical model for marshalling yards is established. Table and Figures | Reference | Related Articles | Metrics

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Link Budget and Enhanced Communication Distance for Ambient Internet of Things YANG Yibing, LIU Ming, XU Rongtao, WANG Gongpu, GONG Wei ZTE Communications    2024, 22 (1): 16-23.   DOI: 10.12142/ZTECOM.202401003 Abstract （91）   HTML （3）    PDF （1976KB）（132）       Knowledge map    Save Backscatter communications will play an important role in connecting everything for beyond 5G (B5G) and 6G systems. One open challenge for backscatter communications is that the signals suffer a round-trip path loss so that the communication distance is short. In this paper, we first calculate the communication distance upper bounds for both uplink and downlink by measuring the tag sensitivity and reflection coefficient. It is found that the activation voltage of the envelope detection diode of the downlink tag is the main factor limiting the backscatter communication distance. Based on this analysis, we then propose to implement a low-noise amplifier (LNA) module before the envelope detection at the tag to enhance the incident signal strength. Our experimental results on the hardware platform show that our method can increase the downlink communication range by nearly 20 m. Table and Figures | Reference | Related Articles | Metrics

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Learning-Based Admission Control for Low-Earth-Orbit Satellite Communication Networks CHENG Lei, QIN Shuang, FENG Gang ZTE Communications    2023, 21 (3): 54-62.   DOI: 10.12142/ZTECOM.202303008 Abstract （90）   HTML （14）    PDF （1188KB）（252）       Knowledge map    Save Satellite communications has been regarded as an indispensable technology for future mobile networks to provide extremely high data rates, ultra-reliability, and ubiquitous coverage. However, the high dynamics caused by the fast movement of low-earth-orbit (LEO) satellites bring huge challenges in designing and optimizing satellite communication systems. Especially, admission control, deciding which users with diversified service requirements are allowed to access the network with limited resources, is of paramount importance to improve network resource utilization and meet the service quality requirements of users. In this paper, we propose a dynamic channel reservation strategy based on the Actor-Critic algorithm (AC-DCRS) to perform intelligent admission control in satellite networks. By carefully designing the long-term reward function and dynamically adjusting the reserved channel threshold, AC-DCRS reaches a long-run optimal access policy for both new calls and handover calls with different service priorities. Numerical results show that our proposed AC-DCRS outperforms traditional channel reservation strategies in terms of overall access failure probability, the average call success rate, and channel utilization under various dynamic traffic conditions. Table and Figures | Reference | Related Articles | Metrics

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Multi-Agent Hierarchical Graph Attention Reinforcement Learning for Grid-Aware Energy Management FENG Bingyi, FENG Mingxiao, WANG Minrui, ZHOU Wengang, LI Houqiang ZTE Communications    2023, 21 (3): 11-21.   DOI: 10.12142/ZTECOM.202303003 Abstract （86）   HTML （14）    PDF （1238KB）（209）       Knowledge map    Save The increasing adoption of renewable energy has posed challenges for voltage regulation in power distribution networks. Grid-aware energy management, which includes the control of smart inverters and energy management systems, is a trending way to mitigate this problem. However, existing multi-agent reinforcement learning methods for grid-aware energy management have not sufficiently considered the importance of agent cooperation and the unique characteristics of the grid, which leads to limited performance. In this study, we propose a new approach named multi-agent hierarchical graph attention reinforcement learning framework (MAHGA) to stabilize the voltage. Specifically, under the paradigm of centralized training and decentralized execution, we model the power distribution network as a novel hierarchical graph containing the agent-level topology and the bus-level topology. Then a hierarchical graph attention model is devised to capture the complex correlation between agents. Moreover, we incorporate graph contrastive learning as an auxiliary task in the reinforcement learning process to improve representation learning from graphs. Experiments on several real-world scenarios reveal that our approach achieves the best performance and can reduce the number of voltage violations remarkably. Table and Figures | Reference | Related Articles | Metrics

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Impacts of Model Mismatch and Array Scale on Channel Estimation for XL-HRIS-Aided Systems LU Zhizheng, HAN Yu, JIN Shi ZTE Communications    2024, 22 (1): 24-33.   DOI: 10.12142/ZTECOM.202401004 Abstract （75）   HTML （4）    PDF （1234KB）（155）       Knowledge map    Save Extremely large-scale hybrid reconfigurable intelligence surface (XL-HRIS), an improved version of the RIS, can receive the incident signal and enhance communication performance. However, as the RIS size increases, the phase variations of the received signal across the whole array are nonnegligible in the near-field region, and the channel model mismatch, which will decrease the estimation accuracy, must be considered. In this paper, the lower bound (LB) of the estimated parameter is studied and the impacts of the distance and signal-to-noise ratio (SNR) on LB are then evaluated. Moreover, the impacts of the array scale on LB and spectral efficiency (SE) are also studied. Simulation results verify that even in extremely large-scale array systems with infinite SNR, channel model mismatch can still limit estimation accuracy. However, this impact decreases with increasing distance. Table and Figures | Reference | Related Articles | Metrics

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Near-Field Wireless Power Transfer, Sensing and Communication with Bessel Beams CAO Xinghan, YIN Huarui, YOU Changsheng ZTE Communications    2024, 22 (1): 53-61.   DOI: 10.12142/ZTECOM.202401007 Abstract （71）   HTML （3）    PDF （1747KB）（188）       Knowledge map    Save The Bessel beam, characterized by its unique non-diffracting properties, holds promising applications. In this paper, we provide a detailed introduction and investigation into the theory and research of the Bessel beam, with a special focus on its generation and applications in the near-field region. We provide an introduction to the concepts, properties, and foundational theories of the Bessel beam. Additionally, the current study on generating Bessel beams and their applications is categorized and discussed, and potential research challenges are proposed in this paper. This review serves as a solid foundation for researchers to understand the concept of the Bessel beam and explore its potential applications. Table and Figures | Reference | Related Articles | Metrics

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Degree of Freedom Analysis for Holographic MIMO Based on a Mutual-Coupling-Compliant Channel Model SUN Yunqi, JIAN Mengnan, YANG Jun, ZHAO Yajun, CHEN Yijian ZTE Communications    2024, 22 (1): 34-40.   DOI: 10.12142/ZTECOM.202401005 Abstract （68）   HTML （7）    PDF （1783KB）（187）       Knowledge map    Save Degree of freedom (DOF) is a key indicator for spatial multiplexing layers of a wireless channel. Traditionally, the channel of a multiple-input multiple-output (MIMO) half-wavelength dipole array has a DOF that equals the antenna number. However, recent studies suggest that the DOF could be less than the antenna number when strong mutual coupling is considered. We utilize a mutual-coupling-compliant channel model to investigate the DOF of the holographic MIMO (HMIMO) channel and give a upper bound of the DOF with strong mutual coupling. Our numerical simulations demonstrate that a dense array can support more DOF per unit aperture as compared with a half-wavelength MIMO system. Table and Figures | Reference | Related Articles | Metrics

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Near-Field Beam Training for Holographic MIMO Communications: Typical Methods, Challenges and Future Directions SHEN Jiayu, YANG Jun, ZHU Chen, DENG Zhiji, HUANG Chongwen ZTE Communications    2024, 22 (1): 41-52.   DOI: 10.12142/ZTECOM.202401006 Abstract （68）   HTML （3）    PDF （3394KB）（250）       Knowledge map    Save Holographic multiple-input multiple-output (HMIMO) has become an emerging technology for achieving ultra-high frequency spectral efficiency and spatial resolution in future wireless systems. The increasing antenna aperture leads to a more significant characterization of the spherical wavefront in near-field communications in HMIMO scenarios. Beam training as a key technique for wireless communication is worth exploring in this near-field scenario. Compared with the widely researched far-field beam training, the increased dimensionality of the search space for near-field beam training poses a challenge to the complexity and accuracy of the proposed algorithm. In this paper, we introduce several typical near-field beam training methods: exhaustive beam training, hierarchical beam training, and multi-beam training that includes equal interval multi-beam training and hash multi-beam training. The performances of these methods are compared through simulation analysis, and their effectiveness is verified on the hardware testbed as well. Additionally, we provide application scenarios, research challenges, and potential future research directions for near-field beam training. Table and Figures | Reference | Related Articles | Metrics

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A Hybrid Five-Level Single-Phase Rectifier with Low Common-Mode Voltage TIAN Ruihan, WU Xuezhi, XU Wenzheng, ZUO Zhiling, CHEN Changqing ZTE Communications    2023, 21 (4): 78-84.   DOI: 10.12142/ZTECOM.202304010 Abstract （67）   HTML （5）    PDF （2986KB）（31）       Knowledge map    Save Rectifiers with high efficiency and high power density are crucial to the stable and efficient power supply of 5G communication base stations, which deserves in-depth investigation. In general, there are two key problems to be addressed: supporting both alternating current (AC) and direct current (DC) input, and minimizing the common-mode voltage as well as leakage current for safety reasons. In this paper, a hybrid five-level single-phase rectifier is proposed. A five-level topology is adopted in the upper arm, and a half-bridge diode topology is adopted in the lower arm. A dual closed-loop control strategy and a flying capacitor voltage regulation method are designed accordingly so that the compatibility of both AC and DC input is realized with low common voltage and small passive devices. Simulation and experimental results demonstrate the effectiveness and performance of the proposed rectifier. Table and Figures | Reference | Related Articles | Metrics

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Massive Unsourced Random Access Under Carrier Frequency Offset XIE Xinyu, WU Yongpeng, YUAN Zhifeng, MA Yihua ZTE Communications    2023, 21 (3): 45-53.   DOI: 10.12142/ZTECOM.202303007 Abstract （67）   HTML （8）    PDF （1438KB）（155）       Knowledge map    Save Unsourced random access (URA) is a new perspective of massive access which aims at supporting numerous machine-type users. With the appearance of carrier frequency offset (CFO), joint activity detection and channel estimation, which is vital for multiple-input and multiple-output URA, is a challenging task. To handle the phase corruption of channel measurements under CFO, a novel compressed sensing algorithm is proposed, leveraging the parametric bilinear generalized approximate message passing framework with a Markov chain support model that captures the block sparsity structure of the considered angular domain channel. An uncoupled transmission scheme is proposed to reduce system complexity, where slot-emitted messages are reorganized relying on clustering unique user channels. Simulation results reveal that the proposed transmission design for URA under CFO outperforms other potential methods. Table and Figures | Reference | Related Articles | Metrics

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RIS-Assisted Cell-Free MIMO: A Survey ZHAO Yaqiong, KE Hongqin, XU Wei, YE Xinquan, CHEN Yijian ZTE Communications    2024, 22 (1): 77-86.   DOI: 10.12142/ZTECOM.202401009 Abstract （63）   HTML （6）    PDF （1473KB）（121）       Knowledge map    Save Cell-free (CF) multiple-input multiple-output (MIMO) is a promising technique to enable the vision of ubiquitous wireless connectivity for next-generation network communications. Compared to traditional co-located massive MIMO, CF MIMO allows geographically distributed access points (APs) to serve all users on the same time-frequency resource with spatial multiplexing techniques, resulting in better performance in terms of both spectral efficiency and coverage enhancement. However, the performance gain is achieved at the expense of deploying more APs with high cost and power consumption. To address this issue, the recently proposed reconfigurable intelligent surface (RIS) technique stands out with its unique advantages of low cost, low energy consumption and programmability. In this paper, we provide an overview of RIS-assisted CF MIMO and its interaction with advanced optimization designs and novel applications. Particularly, recent studies on typical performance metrics such as energy efficiency (EE) and spectral efficiency (SE) are surveyed. Besides, the application of RIS-assisted CF MIMO techniques in various future communication systems is also envisioned. Additionally, we briefly discuss the technical challenges and open problems for this area to inspire research direction and fully exploit its potential in meeting the demands of future wireless communication systems. Table and Figures | Reference | Related Articles | Metrics

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A 220 GHz Frequency-Division Multiplexing Wireless Link with High Data Rate ZHANG Bo, WANG Yihui, FENG Yinian, YANG Yonghui, PENG Lin ZTE Communications    2023, 21 (3): 63-69.   DOI: 10.12142/ZTECOM.202303009 Abstract （59）   HTML （3）    PDF （2704KB）（137）       Knowledge map    Save With the development of wireless communication, the 6G mobile communication technology has received wide attention. As one of the key technologies of 6G, terahertz （THz） communication technology has the characteristics of ultra-high bandwidth, high security and low environmental noise. In this paper, a THz duplexer with a half-wavelength coupling structure and a sub-harmonic mixer operating at 216 GHz and 204 GHz are designed and measured. Based on these key devices, a 220 GHz frequency-division multiplexing communication system is proposed, with a real-time data rate of 10.4 Gbit/s for one channel and a transmission distance of 15 m. The measured constellation diagram of two receivers is clearly visible, the signal-to-noise ratio (SNR) is higher than 22 dB, and the bit error ratio (BER) is less than 10-8. Furthermore, the high definition (HD) 4K video can also be transmitted in real time without stutter. Table and Figures | Reference | Related Articles | Metrics

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Recent Advances in Video Coding for Machines Standard and Technologies ZHANG Qiang, MEI Junjun, GUAN Tao, SUN Zhewen, ZHANG Zixiang, YU Li ZTE Communications    2024, 22 (1): 62-76.   DOI: 10.12142/ZTECOM.202401008 Abstract （58）   HTML （3）    PDF （1394KB）（127）       Knowledge map    Save To improve the performance of video compression for machine vision analysis tasks, a video coding for machines (VCM) standard working group was established to promote standardization procedures. In this paper, recent advances in video coding for machine standards are presented and comprehensive introductions to the use cases, requirements, evaluation frameworks and corresponding metrics of the VCM standard are given. Then the existing methods are presented, introducing the existing proposals by category and the research progress of the latest VCM conference. Finally, we give conclusions. Table and Figures | Reference | Related Articles | Metrics

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Special Topic on Reinforcement Learning and Intelligent Decision GAO Yang ZTE Communications    2023, 21 (3): 1-2.   DOI: 10.12142/ZTECOM.202303001 Abstract （55）   HTML （11）    PDF （334KB）（111）       Knowledge map    Save Reference | Related Articles | Metrics

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Special Topic on Near-Field Communication and Sensing Towards 6G WEI Guo, ZHAO Yajun, CHEN Li ZTE Communications    2024, 22 (1): 1-2.   DOI: 10.12142/ZTECOM.202401001 Abstract （53）   HTML （12）    PDF （366KB）（215）       Knowledge map    Save Reference | Related Articles | Metrics

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Special Topic on 3D Point Cloud Processing and Applications SUN Huifang, LI Ge, CHEN Siheng, LI Li, GAO Wei ZTE Communications    2023, 21 (4): 1-2.   DOI: 10.12142/ZTECOM.202304001 Abstract （51）   HTML （7）    PDF （624KB）（62）       Knowledge map    Save Reference | Related Articles | Metrics

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A Practical Reinforcement Learning Framework for Automatic Radar Detection YU Junpeng, CHEN Yiyu ZTE Communications    2023, 21 (3): 22-28.   DOI: 10.12142/ZTECOM.202303004 Abstract （49）   HTML （6）    PDF （456KB）（114）       Knowledge map    Save At present, the parameters of radar detection rely heavily on manual adjustment and empirical knowledge, resulting in low automation. Traditional manual adjustment methods cannot meet the requirements of modern radars for high efficiency, high precision, and high automation. Therefore, it is necessary to explore a new intelligent radar control learning framework and technology to improve the capability and automation of radar detection. Reinforcement learning is popular in decision task learning, but the shortage of samples in radar control tasks makes it difficult to meet the requirements of reinforcement learning. To address the above issues, we propose a practical radar operation reinforcement learning framework, and integrate offline reinforcement learning and meta-reinforcement learning methods to alleviate the sample requirements of reinforcement learning. Experimental results show that our method can automatically perform as humans in radar detection with real-world settings, thereby promoting the practical application of reinforcement learning in radar operation. Table and Figures | Reference | Related Articles | Metrics

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Perceptual Quality Assessment for Point Clouds : A Survey ZHOU Yingjie, ZHANG Zicheng, SUN Wei, MIN Xiongkuo, ZHAI Guangtao ZTE Communications    2023, 21 (4): 3-16.   DOI: 10.12142/ZTECOM.202304002 Abstract （44）   HTML （2）    PDF （1376KB）（67）       Knowledge map    Save A point cloud is considered a promising 3D representation that has achieved wide applications in several fields. However, quality degradation inevitably occurs during its acquisition and generation, communication and transmission, and rendering and display. Therefore, how to accurately perceive the visual quality of point clouds is a meaningful topic. In this survey, we first introduce the point cloud to emphasize the importance of point cloud quality assessment (PCQA). A review of subjective PCQA is followed, including common point cloud distortions, subjective experimental setups and subjective databases. Then we review and compare objective PCQA methods in terms of model-based and projection-based. Finally, we provide evaluation criteria for objective PCQA methods and compare the performances of various methods across multiple databases. This survey provides an overview of classical methods and recent advances in PCQA. Table and Figures | Reference | Related Articles | Metrics

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Design of Raptor-Like LDPC Codes and High Throughput Decoder Towards 100 Gbit/s Throughput LI Hanwen, BI Ningjing, SHA Jin ZTE Communications    2023, 21 (3): 86-92.   DOI: 10.12142/ZTECOM.202303012 Abstract （38）   HTML （2）    PDF （2033KB）（67）       Knowledge map    Save This paper proposes a raptor-like low-density parity-check (RL-LDPC) code design together with the corresponding decoder hardware architecture aiming at next-generation mobile communication. A new kind of protograph different from the 5G new radio (NR) LDPC basic matrix is presented, and a code construction algorithm is proposed to improve the error-correcting performance. A multi-core layered decoder architecture that supports up to 100 Gbit/s throughput is designed based on the special protograph structure. Table and Figures | Reference | Related Articles | Metrics

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Beyond Video Quality: Evaluation of Spatial Presence in 360-Degree Videos ZOU Wenjie, GU Chengming, FAN Jiawei, HUANG Cheng, BAI Yaxian ZTE Communications    2023, 21 (4): 91-103.   DOI: 10.12142/ZTECOM.202304012 Abstract （37）   HTML （4）    PDF （1676KB）（44）       Knowledge map    Save With the rapid development of immersive multimedia technologies, 360-degree video services have quickly gained popularity and how to ensure sufficient spatial presence of end users when viewing 360-degree videos becomes a new challenge. In this regard, accurately acquiring users’ sense of spatial presence is of fundamental importance for video service providers to improve their service quality. Unfortunately, there is no efficient evaluation model so far for measuring the sense of spatial presence for 360-degree videos. In this paper, we first design an assessment framework to clarify the influencing factors of spatial presence. Related parameters of 360-degree videos and head-mounted display devices are both considered in this framework. Well-designed subjective experiments are then conducted to investigate the impact of various influencing factors on the sense of presence. Based on the subjective ratings, we propose a spatial presence assessment model that can be easily deployed in 360-degree video applications. To the best of our knowledge, this is the first attempt in literature to establish a quantitative spatial presence assessment model by using technical parameters that are easily extracted. Experimental results demonstrate that the proposed model can reliably predict the sense of spatial presence. Table and Figures | Reference | Related Articles | Metrics

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Lossy Point Cloud Attribute Compression with Subnode-Based Prediction YIN Qian, ZHANG Xinfeng, HUANG Hongyue, WANG Shanshe, MA Siwei ZTE Communications    2023, 21 (4): 29-37.   DOI: 10.12142/ZTECOM.202304004 Abstract （37）   HTML （4）    PDF （905KB）（52）       Knowledge map    Save Recent years have witnessed that 3D point cloud compression (PCC) has become a research hotspot both in academia and industry. Especially in industry, the Moving Picture Expert Group (MPEG) has actively initiated the development of PCC standards. One of the adopted frameworks called geometry-based PCC (G-PCC) follows the architecture of coding geometry first and then coding attributes, where the region adaptive hierarchical transform (RAHT) method is introduced for the lossy attribute compression. The upsampled transform domain prediction in RAHT does not sufficiently explore the attribute correlations between neighbor nodes and thus fails to further reduce the attribute redundancy between neighbor nodes. In this paper, we propose a subnode-based prediction method, where the spatial position relationship between neighbor nodes is fully considered and prediction precision is further promoted. We utilize some already-encoded neighbor nodes to facilitate the upsampled transform domain prediction in RAHT by means of a weighted average strategy. Experimental results have illustrated that our proposed attribute compression method shows better rate-distortion (R-D) performance than the latest MPEG G-PCC (both on reference software TMC13-v22.0 and GeS-TM-v2.0). Table and Figures | Reference | Related Articles | Metrics

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Real-Time 4-Mode MDM Transmission Using Commercial 400G OTN Transceivers and All-Fiber Mode Multiplexers REN Fang, LI Yidan, YE Bing, LIU Jianguo, CHEN Weizhang ZTE Communications    2024, 22 (1): 106-110.   DOI: 10.12142/ZTECOM.202401012 Abstract （36）   HTML （1）    PDF （1154KB）（80）       Knowledge map    Save Weakly-coupled mode division multiplexing (MDM) technique is considered a promising candidate to enhance the capacity of an optical transmission system, in which mode multiplexers/demultiplexers (MMUX/MDEMUX) with low insertion loss and modal crosstalk are the key components. In this paper, a low-modal-crosstalk 4-mode MMUX/MDEMUX for the weakly-coupled triple-ring-core few-mode fiber (TRC-FMF) is designed and fabricated with side-polishing processing. The measurement results show that a pair of MMUX/MDEMUX and 25 km weakly-coupled TRC-FMF MDM link achieve low modal crosstalk of lower than -17.5 dB and insertion loss of lower than 11.56 dB for all the four modes. Based on the TRC-FMF and all-fiber MMUX/MDEMUX, an experiment for 25 km real-time 4-mode 3-λ wavelength division multiplexing (WDM)-MDM transmission is conducted using commercial 400G optical transport network (OTN) transceivers. The experimental results prove weakly-coupled MDM techniques facilitate a smooth upgrade of the optical transmission system. Table and Figures | Reference | Related Articles | Metrics

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Research on Multi-Core Processor Analysis for WCET Estimation LUO Haoran, HU Shuisong, WANG Wenyong, TANG Yuke, ZHOU Junwei ZTE Communications    2024, 22 (1): 87-94.   DOI: 10.12142/ZTECOM.202401010 Abstract （33）   HTML （3）    PDF （432KB）（27）       Knowledge map    Save Real-time system timing analysis is crucial for estimating the worst-case execution time (WCET) of a program. To achieve this, static or dynamic analysis methods are used, along with targeted modeling of the actual hardware system. This literature review focuses on calculating WCET for multi-core processors, providing a survey of traditional methods used for static and dynamic analysis and highlighting the major challenges that arise from different program execution scenarios on multi-core platforms. This paper outlines the strengths and weaknesses of current methodologies and offers insights into prospective areas of research on multi-core analysis. By presenting a comprehensive analysis of the current state of research on multi-core processor analysis for WCET estimation, this review aims to serve as a valuable resource for researchers and practitioners in the field. Table and Figures | Reference | Related Articles | Metrics

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Perceptual Optimization for Point-Based Point Cloud Rendering YIN Yujie, CHEN Zhang ZTE Communications    2023, 21 (4): 47-53.   DOI: 10.12142/ZTECOM.202304006 Abstract （32）   HTML （2）    PDF （1647KB）（52）       Knowledge map    Save Point-based rendering is a common method widely used in point cloud rendering. It realizes rendering by turning the points into the base geometry. The critical step in point-based rendering is to set an appropriate rendering radius for the base geometry, usually calculated using the average Euclidean distance of the N nearest neighboring points to the rendered point. This method effectively reduces the appearance of empty spaces between points in rendering. However, it also causes the problem that the rendering radius of outlier points far away from the central region of the point cloud sequence could be large, which impacts the perceptual quality. To solve the above problem, we propose an algorithm for point-based point cloud rendering through outlier detection to optimize the perceptual quality of rendering. The algorithm determines whether the detected points are outliers using a combination of local and global geometric features. For the detected outliers, the minimum radius is used for rendering. We examine the performance of the proposed method in terms of both objective quality and perceptual quality. The experimental results show that the peak signal-to-noise ratio (PSNR) of the point cloud sequences is improved under all geometric quantization, and the PSNR improvement ratio is more evident in dense point clouds. Specifically, the PSNR of the point cloud sequences is improved by 3.6% on average compared with the original algorithm. The proposed method significantly improves the perceptual quality of the rendered point clouds and the results of ablation studies prove the feasibility and effectiveness of the proposed method. Table and Figures | Reference | Related Articles | Metrics

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Simulation and Modeling of Common Mode EMI Noise in Planar Transformers LI Wei, JI Jingkang, LIU Yuanlong, SUN Jiawei, LIN Subin ZTE Communications    2023, 21 (3): 105-116.   DOI: 10.12142/ZTECOM.202303014 Abstract （32）   HTML （2）    PDF （3135KB）（34）       Knowledge map    Save The transformer is the key circuit component of the common-mode noise current when an isolated converter is working. The high-frequency characteristics of the transformer have an important influence on the common-mode noise of the converter. Traditionally, the measurement method is used for transformer modeling, and a single lumped device is used to establish the transformer model, which cannot be predicted in the transformer design stage. Based on the transformer common-mode noise transmission mechanism, this paper derives the transformer common-mode equivalent capacitance under ideal conditions. According to the principle of experimental measurement of the network analyzer, the electromagnetic field finite element simulation software three-dimensional (3D) modeling and simulation method is used to obtain the two-port parameters of the transformer, extract the high-frequency parameters of the transformer, and establish its electromagnetic compatibility equivalent circuit model. Finally, an experimental prototype is used to verify the correctness of the model by comparing the experimental measurement results with the simulation prediction results. Table and Figures | Reference | Related Articles | Metrics

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Hybrid Architecture and Beamforming Optimization for Millimeter Wave Systems TANG Yuanqi, ZHANG Huimin, ZHENG Zheng, LI Ping, ZHU Yu ZTE Communications    2023, 21 (3): 93-104.   DOI: 10.12142/ZTECOM.202303013 Abstract （31）   HTML （1）    PDF （4586KB）（68）       Knowledge map    Save Hybrid beamforming (HBF) has become an attractive and important technology in massive multiple-input multiple-output (MIMO) millimeter-wave (mmWave) systems. There are different hybrid architectures in HBF depending on different connection strategies of the phase shifter network between antennas and radio frequency chains. This paper investigates HBF optimization with different hybrid architectures in broadband point-to-point mmWave MIMO systems. The joint hybrid architecture and beamforming optimization problem is divided into two sub-problems. First, we transform the spectral efficiency maximization problem into an equivalent weighted mean squared error minimization problem, and propose an algorithm based on the manifold optimization method for the hybrid beamformer with a fixed hybrid architecture. The overlapped subarray architecture which balances well between hardware costs and system performance is investigated. We further propose an algorithm to dynamically partition antenna subarrays and combine it with the HBF optimization algorithm. Simulation results are presented to demonstrate the performance improvement of our proposed algorithms. Table and Figures | Reference | Related Articles | Metrics

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Research on Fall Detection System Based on Commercial Wi-Fi Devices GONG Panyin, ZHANG Guidong, ZHANG Zhigang, CHEN Xiao, DING Xuan ZTE Communications    2023, 21 (4): 60-68.   DOI: 10.12142/ZTECOM.202304008 Abstract （30）   HTML （3）    PDF （1651KB）（38）       Knowledge map    Save Falls are a major cause of disability and even death in the elderly, and fall detection can effectively reduce the damage. Compared with cameras and wearable sensors, Wi-Fi devices can protect user privacy and are inexpensive and easy to deploy. Wi-Fi devices sense user activity by analyzing the channel state information (CSI) of the received signal, which makes fall detection possible. We propose a fall detection system based on commercial Wi-Fi devices which achieves good performance. In the feature extraction stage, we select the discrete wavelet transform (DWT) spectrum as the feature for activity classification, which can balance the temporal and spatial resolution. In the feature classification stage, we design a deep learning model based on convolutional neural networks, which has better performance compared with other traditional machine learning models. Experimental results show our work achieves a false alarm rate of 4.8% and a missed alarm rate of 1.9%. Table and Figures | Reference | Related Articles | Metrics

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Building a Stronger Foundation for Web3: Advantages of 5G Infrastructure FENG Jianxin, PAN Yi, WU Xiao ZTE Communications    2024, 22 (2): 3-10.   DOI: 10.12142/ZTECOM.202402002 Abstract （28）   HTML （3）    PDF （1211KB）（5）       Knowledge map    Save The emergence of Web3 technologies promises to revolutionize the Internet and redefine our interactions with digital assets and applications. This essay explores the pivotal role of 5G infrastructure in bolstering the growth and potential of Web3. By focusing on several crucial aspects—network speed, edge computing, network capacity, security and power consumption—we shed light on how 5G technology offers a robust and transformative foundation for the decentralized future of the Internet. Prior to delving into the specifics, we undertake a technical review of the historical progression and development of Internet and telecommunication technologies. Table and Figures | Reference | Related Articles | Metrics

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Mixed Electric and Magnetic Coupling Design Based on Coupling Matrix Extraction XIONG Zhiang, ZHAO Ping, FAN Jiyuan, WU Zengqiang, GONG Hongwei ZTE Communications    2023, 21 (4): 85-90.   DOI: 10.12142/ZTECOM.202304011 Abstract （27）   HTML （2）    PDF （1412KB）（18）       Knowledge map    Save This paper proposes a design and fine-tuning method for mixed electric and magnetic coupling filters. It derives the quantitative relationship between the coupling coefficients (electric and magnetic coupling, i.e., EC and MC) and the linear coefficients of frequency-dependent coupling for the first time. Different from the parameter extraction technique using the bandpass circuit model, the proposed approach explicitly relatesEC and MC to the coupling matrix model. This paper provides a general theoretic framework for computer-aided design and tuning of a mixed electric and magnetic coupling filter based on coupling matrices. An example of a 7th-order coaxial combline filter design is given in the paper, verifying the practical value of the approach. Table and Figures | Reference | Related Articles | Metrics

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Point Cloud Processing Methods for 3D Point Cloud Detection Tasks WANG Chongchong, LI Yao, WANG Beibei, CAO Hong, ZHANG Yanyong ZTE Communications    2023, 21 (4): 38-46.   DOI: 10.12142/ZTECOM.202304005 Abstract （27）   HTML （5）    PDF （787KB）（54）       Knowledge map    Save Light detection and ranging (LiDAR) sensors play a vital role in acquiring 3D point cloud data and extracting valuable information about objects for tasks such as autonomous driving, robotics, and virtual reality (VR). However, the sparse and disordered nature of the 3D point cloud poses significant challenges to feature extraction. Overcoming limitations is critical for 3D point cloud processing. 3D point cloud object detection is a very challenging and crucial task, in which point cloud processing and feature extraction methods play a crucial role and have a significant impact on subsequent object detection performance. In this overview of outstanding work in object detection from the 3D point cloud, we specifically focus on summarizing methods employed in 3D point cloud processing. We introduce the way point clouds are processed in classical 3D object detection algorithms, and their improvements to solve the problems existing in point cloud processing. Different voxelization methods and point cloud sampling strategies will influence the extracted features, thereby impacting the final detection performance. Table and Figures | Reference | Related Articles | Metrics

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Spatio-Temporal Context-Guided Algorithm for Lossless Point Cloud Geometry Compression ZHANG Huiran, DONG Zhen, WANG Mingsheng ZTE Communications    2023, 21 (4): 17-28.   DOI: 10.12142/ZTECOM.202304003 Abstract （27）   HTML （3）    PDF （2655KB）（55）       Knowledge map    Save Point cloud compression is critical to deploy 3D representation of the physical world such as 3D immersive telepresence, autonomous driving, and cultural heritage preservation. However, point cloud data are distributed irregularly and discontinuously in spatial and temporal domains, where redundant unoccupied voxels and weak correlations in 3D space make achieving efficient compression a challenging problem. In this paper, we propose a spatio-temporal context-guided algorithm for lossless point cloud geometry compression. The proposed scheme starts with dividing the point cloud into sliced layers of unit thickness along the longest axis. Then, it introduces a prediction method where both intra-frame and inter-frame point clouds are available, by determining correspondences between adjacent layers and estimating the shortest path using the travelling salesman algorithm. Finally, the few prediction residual is efficiently compressed with optimal context-guided and adaptive fast-mode arithmetic coding techniques. Experiments prove that the proposed method can effectively achieve low bit rate lossless compression of point cloud geometric information, and is suitable for 3D point cloud compression applicable to various types of scenes. Table and Figures | Reference | Related Articles | Metrics

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Local Scenario Perception and Web AR Navigation SHI Wenzhe, LIU Yanbin, ZHOU Qinfen ZTE Communications    2023, 21 (4): 54-59.   DOI: 10.12142/ZTECOM.202304007 Abstract （26）   HTML （1）    PDF （1324KB）（43）       Knowledge map    Save This paper proposes a local point cloud map-based Web augmented reality (AR) indoor navigation system solution. By delivering the local point cloud map to the web front end for positioning, the real-time positioning can be implemented only with the help of the computing power of the web front end. In addition, with the characteristics of short time consumption and accurate positioning, an optimization solution to the local point cloud map is proposed, which includes specific measures such as descriptor de-duplicating and outlier removal, thus improving the quality of the point cloud. In this document, interpolation and smoothing effects are introduced for local map positioning, enhancing the anchoring effect and improving the smoothness and appearance of user experience. In small-scale indoor scenarios, the positioning frequency on an iPhone 13 can reach 30 fps, and the positioning precision is within 50 cm. Compared with an existing mainstream visual-based positioning manner for AR navigation, this specification does not rely on any additional sensor or cloud computing device, thereby greatly saving computing resources. It takes a very short time to meet the real-time requirements and provide users with a smooth positioning effect. Table and Figures | Reference | Related Articles | Metrics

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Incident and Problem Ticket Clustering and Classification Using Deep Learning FENG Hailin, HAN Jing, HUANG Leijun, SHENG Ziwei, GONG Zican ZTE Communications    2023, 21 (4): 69-77.   DOI: 10.12142/ZTECOM.202304009 Abstract （23）   HTML （5）    PDF （726KB）（17）       Knowledge map    Save A holistic analysis of problem and incident tickets in a real production cloud service environment is presented in this paper. By extracting different bags of words, we use principal component analysis (PCA) to examine the clustering characteristics of these tickets. Then K-means and latent Dirichlet allocation (LDA) are applied to show the potential clusters within this Cloud environment. The second part of our study uses a pre-trained bidirectional encoder representation from transformers (BERT) model to classify the tickets, with the goal of predicting the optimal dispatching department for a given ticket. Experimental results show that due to the unique characteristics of ticket description, pre-processing with domain knowledge turns out to be critical in both clustering and classification. Our classification model yields 86% accuracy when predicting the target dispatching department. Table and Figures | Reference | Related Articles | Metrics

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Special Topic onAdvancements in Web3 Infrastructure for the Metaverse Victor C. M. LEUNG, CAI Wei ZTE Communications    2024, 22 (2): 1-2.   DOI: 10.12142/ZTECOM.202402001 Abstract （23）   HTML （0）    PDF （411KB）（7）       Knowledge map    Save Reference | Related Articles | Metrics