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Improvement of X-Band Polarization Radar Melting Layer Recognition by the Bayesian Method and ITS Impact on Hydrometeor Classification

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Advances in Atmospheric Sciences 2020年第1期37卷 105-116页

作者： Jianli MA zhiqun hu Meilin YANG Siteng LI Institute of Urban Meteorology China Meteorological AdministrationBeijing 100089China State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081China

Using melting layer(ML)and non-melting layer(NML)data observed with the X-band dual linear polarization Doppler weather radar(X-POL)in Shunyi,Beijing,the reflectivity(ZH),differential reflectivity(ZDR),and correlation coefficient(CC)in the ML and NML are obtained in several stable precipitation *** prior probability density distributions(PDDs)of the ZH,ZDR and CC are calculated first,and then the probabilities of ZH,ZDR and CC at each radar gate are determined(PBB in the ML and PNB in the NML)by the Bayesian *** PBB>PNB the gate belongs to the ML,and when PBBhunyi,Beijing,the reflectivity(ZH),differential reflectivity(ZDR),and correlation coefficient(CC)in the ML and NML are obtained in several stable precipitation *** prior probability density distributions(PDDs)of the ZH,ZDR and CC are calculated first,and then the probabilities of ZH,ZDR and CC at each radar gate are determined(PBB in the ML and PNB in the NML)by the Bayesian *** PBB>PNB the gate belongs to the ML,and when PBB

关键词： X-band polarimetric radar Bayesian method melting layer identification hydrometeor classification

Improving throughput through dynamically tuning contention window size in dense wireless network

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The Journal of China Universities of Posts and Telecommunications 2017年第4期24卷 27-33页

作者： Lin Shangjuan Wen Xiangming hu zhiqun Lu Zhaoming School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications Beijing 100876 China Beijing Laboratory of Advanced Information Networks Beijing University of Posts and Telecommunications Beijing 100876 China

With the boom of wireless devices, the number of wireless users under wireless local area networks （WLANs） has increased dramatically. However, the standard baekoff mechanism in IEEE 802.11 adopts fixed initial contention window （CW） size without considering changes of network load, which leads to a high collision probability and low channel utilization in bursty arrivals. In this paper, a novel CW dynamic adjustment scheme is proposed to achieve high throughput performance in dense user environment. In the proposed scheme, the initial CW size is dynamically adjusted to optimum according to the measured packet collision probability. Simulation results show that the proposed scheme can significantly improve the throughput performance.

关键词： wireless local area network (WLAN) dense user environment contention window (CW) dynamic optimization

QoE based power control scheme for interference mitigation in high-density WLANs

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The Journal of China Universities of Posts and Telecommunications 2016年第2期23卷 24-30页

作者： Wang Yiqing Wen Xiangming hu zhiqun Lu Zhaoming School of Telecommunication Engineering Beijing University of Posts and Telecommunications

Mobile data traffic is going through an explosive growth recently as mobile smart devices become more and more ubiquitous, causing huge pressure on cellular network. Taking advantage of its low cost and easy-to-deploy feature, wireless local-area networks（WLAN） becomes increasingly popular to offload data streams from cellular network, followed by higher and higher density of its deployment. However, the high density of WLAN will cause more interference, which results in degradation of its performance. Therefore, in order to enhance the performance of the network, we aim to minimize the interference caused by high density of WLAN. In this paper, we propose a novel power control scheme to achieve the above aim. We use the quality of experience（QoE） evaluation to coordinate the power of each access point（AP） and finally realize the optimization of the entire network. According to the simulation results, our scheme improves the performance of the network significantly in many aspects, including throughput and QoE.

关键词： power control high-density WLAN interference mitigation QoE

Performance analysis of LTE-U coexistence network with WiFi using queueing model

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The Journal of China Universities of Posts and Telecommunications 2017年第5期24卷 1-7页

作者： hu zhiqun Lu Zhaoming Lin Shangjuan Wen Xiangming Xu Hen School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

The unforeseen mobile data explosion as well as the scarce of spectrum resource pose a major challenge to the performance of today＇s cellular networks which are in urgent need of novel solutions to handle such voluminous mobile data. Long term evolution-unlicensed （LTE-U）, which extends the LTE standard operating on the unlicensed band, has been proposed to improve system throughput. In LTE-U system, arriving users will contend the unlicensed spectrum resource with wireless fidelity （WiFi） users to transmit data information. Nevertheless, there is no clear consensus as to the benefits of transmission using unlicensed bands for LTE users. To this end, in this paper an analytical model is presented based on a queue system to understand the performance achieved by unlicensed based LTE system taking quality of services （QoS） and LTE-U users＇ behaviors into account. To obtain the stead-state solutions of the queue system, a matrix geometric method is used to solve it. Then, the average delay and utilization of unlicensed band for the LTE-U users is derived by using the queuing model. The performance of LTE-U coexistence is evaluated with WiFi using the proposed model and provide some initial insights as to the advantage of LTE-U in practice.

关键词： LTE-U WiFi queueing model matrix geometric method

Study on Quantitative Precipitation Estimation by Polarimetric Radar Using Deep Learning

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Advances in Atmospheric Sciences 2024年第6期41卷 1147-1160页

作者： Jiang huANGFU zhiqun hu Jiafeng ZHENG Lirong WANG Yongjie Zhu State Key Lab of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081China Meteorological observatory of Jiangxi Province Nanchang 330096China Hebei Meteorological Disaster Prevention and Environmental Meteorological Center Shijiazhuang 050021China School of Atmospheric Sciences Chengdu University of Information TechnologyChengdu 610225China

Accurate radar quantitative precipitation estimation(QPE)plays an essential role in disaster prevention and *** this paper,two deep learning-based QPE networks including a single-parameter network and a multi-parameter network are ***,a self-defined loss function(SLF)is proposed during *** dataset includes Shijiazhuang S-band dual polarimetric radar(CINRAD/SAD)data and rain gauge data within the radar’s 100-km detection range during the flood season of 2021 in North *** that the specific propagation phase shift(KDP)has a roughly linear relationship with the precipitation intensity,KDP is set to 0.5°km^(-1 )as a threshold value to divide all the rain data(AR)into a heavy rain(HR)and light rain(LR)***,12 deep learning-based QPE models are trained according to the input radar parameters,the precipitation datasets,and whether an SLF was adopted,*** results suggest that the effects of QPE after distinguishing rainfall intensity are better than those without distinguishing,and the effects of using SLF are better than those that used MSE as a loss function.A Z-R relationship and a ZH-KDP-R synthesis method are compared with deep learning-based *** mean relative errors(MRE)of AR models using SLF are improved by 61.90%,51.21%,and 56.34%compared with the Z-R relational method,and by 38.63%,42.55%,and 47.49%compared with the synthesis ***,the models are further evaluated in three precipitation processes,which manifest that the deep learning-based models have significant advantages over the traditional empirical formula methods.

关键词： polarimetric radar quantitative precipitation estimation deep learning single-parameter network multi-parameter network

Spectrum efficiency maximization with trajectory design in UAV-enabled mobile relaying

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The Journal of China Universities of Posts and Telecommunications 2019年第4期26卷 17-24页

作者： Sun Chuanzhi hu zhiqun Wen Xiangming Lu Zhaoming Qi Hang Beijing Laboratory of Advanced Information Networks Beijing University of Posts and TelecommunicationsBeijing 100876China Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and TelecommunicationsBeijing 100876China School of Computer and Information Engineering Hubei UniversityWuhan 430062China

With the advantages of low cost and high mobility,unmanned aerial vehicles(UAVs)have played an important role in wireless *** investigate a UAV-enabled mobile relaying system,where a UAV is used as a mobile relay to assist in the communication from a ground source to a ground destination since their direct link is *** the conventional mobile relay in which the UAV adopts straight line or circular trajectory,we consider a more general elliptical trajectory and use realistic channel *** assuming that the UAV employs time-division duplexing(TDD)based decode-and-forward(DF)relaying,we jointly optimize the time allocations and the UAV trajectory to formulate the maximization of spectrum efficiency(SE).The simulation results show that the trajectory we designed achieves a higher SE than the optimal circular trajectory and static relaying.

关键词： UAV mobile relay time allocations elliptical trajectory

Adaptive WiFi-offloading algorithm based on attractor selection in heterogeneous wireless networks

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The Journal of China Universities of Posts and Telecommunications 2015年第6期22卷 94-100页

作者： hu zhiqun Wen Xiangming Lu Zhaoming Wang Yiqing Ling Dabing School of Telecommunication Engineering Beijing University of Posts and Telecommunications

The unforeseen mobile data explosion poses a major challenge to the performance of today＇s cellular networks, and cellular networks are in urgent need of novel solutions to handle such voluminous mobile data. Obviously, data offioading through third-party WiFi access points （APs） can effectively alleviate the data load in the cellular networks with a low operational and capital expenditure. In this paper, we propose and analyze an adaptive WiFi-offioading algorithm based on attractor selection in heterogeneous wireless networks. In the proposed WiFi-offloading algorithm, the WiFi system throughput and cellular throughput in the coverage area of WiFi, are mapped into the activity of the attractor, which is the reflector of the current network environment. When the current attractor activity is low, the network is dominated by the noise. Then, the noise triggers the controller to select adaptive attractor, an optimal WiFi-offloading ratio 4, to adapt to the dynamic network environment. And users offload the specific portion of traffic to the WiFi networks with the ratio of φ, which improves the throughput of heterogeneous wireless networks and alleviates the load of cellular networks. Through simulation, we show that the proposed WiFi-offioading algorithm outperforms the existing ones with 21% higher heterogeneous network throughput in a dense traffic environment.

关键词： WiFi-offioading algorithm attractor selection activity heterogeneous w!reless networks

On-line learning algorithm for dynamic sensitivity control in IEEE 802. 11ax network

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The Journal of China Universities of Posts and Telecommunications 2018年第5期25卷 67-74页

作者： Li Qishan hu zhiqun Wen Xiangming Lu Zhaoming Qi Hang School of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications Beijing Laboratory of Advanced Information Networks Beijing University of Posts and Telecommunications

The popularity of IEEE 802. 11 based wireless local area network（ WLAN） increased significantly in recent years and resulted in the dense deployment of WLANs. While densification can contribute to increasing coverage,it could also lead to increasing interference and cannot insure high spatial reuse due to the current physical carrier sensing of IEEE 802. 11. To tackle these challenges,the dynamic sensitivity control（ DSC） is considered in IEEE802. 11 ax,which dynamically selects the appropriate carrier sensing threshold（ CST） to improve spectrum efficiency and enhance spatial reuse in densely deployed network. A dynamic Q-learning based CST selection method is proposed to enable a network to select the optimal CST according to the channel condition. Simulation results show that the proposed scheme provides 40% aggregate throughput gain of a dense network when compared with legacy IEEE 802. 11.

关键词： IEEE 802. llax reinforcement learning dynamic sensitivity control dense network

A Quality Assurance Procedure and Evaluation of Rainfall Estimates for C-Band Polarimetric Radar

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Advances in Atmospheric Sciences 2012年第1期29卷 144-156页

作者： hu zhiqun LIU Liping WANG Lirong State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081 Shijiazhuang Meteorological Observatory Shijiazhuang 050081

A mobile C-band dual polarimetric weather radar J type （PCDJ）, which adopts simultaneous transmission and simultaneous reception （STSR） of horizontally and vertically polarized signals, was first developed in China in 2008. It was deployed in the radar observation plan in the South China Heavy Rainfall Experiment （SCHeREX） in the summer of 2008 and 2009, as well as in Tropical Western Pacific Ocean Observation Experiments and Research on the Predictability of High Impact Weather Events from 2008 to 2010 in China （TWPOR）. Using the observation data collected in these experiments, the radar systematic error and its sources were analyzed in depth. Meanwhile an algorithm that can smooth differential propagation phase （~Dp） for estimating the high-resolution specific differential phase （KDP） was developed. After attenuation correction of reflectivity in horizontal polarization （ZH） and differential reflectivity （ZDR） of PCDJ radar by means of KDP, the data quality was improved significantly. Using quality-controlled radar data, quantitative rainfall estimation was performed, and the resutls were compared with rain-gauge measurements. A synthetic ZH /KDp-based method was analyzed. The results the traditional ZH-based method when the rain suggest that the synthetic method has the advantage over rate is 〉5 mm h^-1. The more intensive the rain rates, the higher accuracy of the estimation.

关键词： quality assurance rainfall estimates C-band polarimetric radar