International Journal of Satellite Communications and Networking最新文献

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IF 0.9 4区计算机科学

International Journal of Satellite Communications and Networking Pub Date : 2025-04-29 DOI: 10.1002/sat.1566

Davide Orsucci, Philipp Kleinpaß, Jaspar Meister, Innocenzo De Marco, Stefanie Häusler, Thomas Strang, Nino Walenta, Florian Moll

引用次数: 0

Update on the German and Australasian Optical Ground Station Networks 德国和澳大利亚光地面站网络的最新情况

IF 0.9 4区计算机科学

International Journal of Satellite Communications and Networking Pub Date : 2025-03-25 DOI: 10.1002/sat.1564

Nicholas J. Rattenbury, Joseph Ashby, Francis Bennet, Marcus Birch, John E. Cater, Kate Ferguson, Dirk Giggenbach, Ken Grant, Andreas Knopp, Marcus T. Knopp, Ed Kruzins, Andrew Lambert, Kerry Mudge, Catherine Qualtrough, Samuele Raffa, Jonas Rittershofer, Mikhael T. Sayat, Sascha Schediwy, Robert T. Schwarz, Matthew Sellars, Oliver Thearle, Tony Travouillon, Kevin Walker, Shane Walsh, Stephen Weddell

{"title":"Update on the German and Australasian Optical Ground Station Networks","authors":"Nicholas J. Rattenbury, Joseph Ashby, Francis Bennet, Marcus Birch, John E. Cater, Kate Ferguson, Dirk Giggenbach, Ken Grant, Andreas Knopp, Marcus T. Knopp, Ed Kruzins, Andrew Lambert, Kerry Mudge, Catherine Qualtrough, Samuele Raffa, Jonas Rittershofer, Mikhael T. Sayat, Sascha Schediwy, Robert T. Schwarz, Matthew Sellars, Oliver Thearle, Tony Travouillon, Kevin Walker, Shane Walsh, Stephen Weddell","doi":"10.1002/sat.1564","DOIUrl":"https://doi.org/10.1002/sat.1564","url":null,"abstract":"<p>Networks of ground stations designed to transmit and receive at visible and infra-red wavelengths through the atmosphere offer an opportunity to provide on-demand, high-bandwidth, secure communications with spacecraft in Earth orbit and beyond. This work describes the operation and activities of current free space optical communications (FSOC) ground stations in Germany and Australasia. In Germany, FSOC facilities are located at the Oberpfaffenhofen campus of the German Aerospace Center (DLR), the Laser-Bodenstation in Trauen (Responsive Space Cluster Competence Center, DLR), and the Research Center Space of the University of the Bundeswehr Munich in Neubiberg. The DLR also operates a ground station in Almería, Spain, as part of the European Optical Nucleus Network (EONN). The Australasian Optical Ground Station Network (AOGSN) is a proposed network of 0.5–0.7 m class optical telescopes located across Australia and New Zealand. The development and progress for each node of the AOGSN is reported, along with optimization of future site locations based on cloud cover analysis.</p>","PeriodicalId":50289,"journal":{"name":"International Journal of Satellite Communications and Networking","volume":"43 3","pages":"147-163"},"PeriodicalIF":0.9,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/sat.1564","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143889136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A Novel Spaceborne Antenna Repositioning Method for Reliable Communication in Inclined Satellites 面向倾斜卫星可靠通信的星载天线重新定位新方法

IF 0.9 4区计算机科学

International Journal of Satellite Communications and Networking Pub Date : 2025-03-10 DOI: 10.1002/sat.1558

Oz Ibrahim, Yumusak Nejat

{"title":"A Novel Spaceborne Antenna Repositioning Method for Reliable Communication in Inclined Satellites","authors":"Oz Ibrahim, Yumusak Nejat","doi":"10.1002/sat.1558","DOIUrl":"https://doi.org/10.1002/sat.1558","url":null,"abstract":"<div>\u0000 \u0000 <p>This study introduces a novel method for repositioning multi-steerable antennas on inclined geostationary earth orbit (GEO) satellites to enhance signal quality by mitigating signal degradation caused by coverage shifts due to satellite inclination. The innovation of this research lies in the real-time tracking of target ground stations (boresights) by spaceborne satellite antennas to maintain stable coverage footprints, marking a first in inclined geostationary satellite operations. Orbit simulations and analyses were conducted on the operational satellite Sat-A to evaluate the proposed onboard satellite antenna repositioning (OSAR) method. Various inclination angles (1°, 2°, 4°, and 6°) were considered, focusing on two coverage areas, BR1 and BR2. The method was validated through simulations by comparing Sat-A's zero-inclination baseline values with the repositioning results when pointing towards ground stations. The repositioned spaceborne antennas (S1 and S2) achieved remarkable pointing accuracy, with maximum errors of only 0.0165° in latitude and 0.0023° in longitude. Corresponding link performance metrics further confirmed the method's reliability, showing an equivalent isotropically radiated power (EIRP) deviation of 10<sup>−13</sup> dB and an energy per bit to noise density ratio (E<sub>b</sub>/N<sub>0</sub>) variation of just 0.0795 dB. This performance is particularly critical for regions affected by beam shifts due to inclination. The simulation results demonstrate that the OSAR method is both accurate and cost-effective, making it suitable for various satellite services. By ensuring signal quality during inclined operations, the OSAR method offers a robust solution for satellite operators, enabling the delivery of reliable and high-quality services to customers.</p>\u0000 </div>","PeriodicalId":50289,"journal":{"name":"International Journal of Satellite Communications and Networking","volume":"43 4","pages":"318-332"},"PeriodicalIF":0.9,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144299540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Minimum Round-Trip Time Prediction for Low Earth Orbit Satellite Networks 低地球轨道卫星网络最小往返时间预测

IF 0.9 4区计算机科学

International Journal of Satellite Communications and Networking Pub Date : 2025-02-24 DOI: 10.1002/sat.1557

Jiayi Chen, Ye Li, Haoye Chai, Jue Wang, Sheng Wu, Jianping Pan

{"title":"Minimum Round-Trip Time Prediction for Low Earth Orbit Satellite Networks","authors":"Jiayi Chen, Ye Li, Haoye Chai, Jue Wang, Sheng Wu, Jianping Pan","doi":"10.1002/sat.1557","DOIUrl":"https://doi.org/10.1002/sat.1557","url":null,"abstract":"<div>\u0000 \u0000 <p>Low Earth orbit (LEO) satellite networks, characterized by wide coverage, low latency, and high bandwidth, will be a key component of the future 6G mobile communication networks. However, the periodic handover of satellites in LEO networks will lead to dynamic path changes and fluctuations in propagation delay, affecting the end-to-end performance. Establishing a minimum round-trip time (minRTT) prediction model for LEO satellite networks is crucial for optimizing the design of related mechanisms such as routing, congestion control, and loss recovery. To this end, this paper first conducts a Starlink measurement to collect real-life data and then proposes a novel model combining hybrid attention (HA) mechanisms with multiscale convolutional neural networks (MCNN) and long short-term memory networks (LSTM) to explore minRTT prediction. The method utilizes HA to highlight important positional features in the minRTT sequence, while the MCNN and LSTM are exploited to capture the variation patterns of minRTTs, thereby enhancing the prediction accuracy. Experimental results show that the proposed HA-MCNN-LSTM model outperforms existing methods.</p>\u0000 </div>","PeriodicalId":50289,"journal":{"name":"International Journal of Satellite Communications and Networking","volume":"43 4","pages":"309-317"},"PeriodicalIF":0.9,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Extending GEO Satellite Operations: Timing and Challenges of Inclined Orbit Transitions 扩展地球同步轨道卫星运行：倾斜轨道过渡的时机和挑战

IF 0.9 4区计算机科学

International Journal of Satellite Communications and Networking Pub Date : 2025-02-24 DOI: 10.1002/sat.1559

Umit Cezmi Yilmaz

{"title":"Extending GEO Satellite Operations: Timing and Challenges of Inclined Orbit Transitions","authors":"Umit Cezmi Yilmaz","doi":"10.1002/sat.1559","DOIUrl":"https://doi.org/10.1002/sat.1559","url":null,"abstract":"<div>\u0000 \u0000 <p>Maximizing the operational lifespan of Geostationary Earth Orbit (GEO) satellites is a critical objective for satellite operators. Throughout their service life, satellites are maintained within a designated control box through North–South (NS) and East–West (EW) station-keeping maneuvers. NS maneuvers, which adjust the satellite's inclination relative to the equatorial plane, require significantly more propellant than EW maneuvers. As a result, operators often choose to discontinue NS maneuvers, allowing the satellite to transition into an “inclined orbit” while relying on EW maneuvers to manage orbit drift and maintain longitude positioning. This approach is typically adopted when the satellite nears the end of its operational life or when fuel conservation becomes a priority. A critical challenge in this process is determining the optimal timing for initiating inclined orbit, which involves carefully balancing factors such as fuel availability, satellite health, mission requirements, and operational constraints. This study provides a comprehensive analysis of these factors, with a detailed exploration of timing optimization, and concludes with a practical case study to illustrate the findings.</p>\u0000 </div>","PeriodicalId":50289,"journal":{"name":"International Journal of Satellite Communications and Networking","volume":"43 4","pages":"333-341"},"PeriodicalIF":0.9,"publicationDate":"2025-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

An Integrated LEO Communication and PNT System for Beyond 5G NTN 面向超5G NTN的集成LEO通信和PNT系统

IF 0.9 4区计算机科学

International Journal of Satellite Communications and Networking Pub Date : 2025-02-17 DOI: 10.1002/sat.1556

Riccardo De Gaudenzi

{"title":"An Integrated LEO Communication and PNT System for Beyond 5G NTN","authors":"Riccardo De Gaudenzi","doi":"10.1002/sat.1556","DOIUrl":"https://doi.org/10.1002/sat.1556","url":null,"abstract":"<div>\u0000 \u0000 <p>This paper proposes a pragmatic approach to integrate communication (COM) and positioning navigation timing (PNT) services in (beyond) 5G ((B)5G) low Earth orbiting (LEO) satellite nonterrestrial networks (NTN). The goal is to optimize performance and minimize complementary PNT service costs. The current third generation partnership program (3GPP) fifth generation (5G) standard incorporates positioning reference signal (PRS) for enhancing user equipment (UE) positioning accuracy. However, this approach relies on network connectivity and is not suitable for UE standalone PNT service provision. Additionally, PRS exploitation in a NTN satellite constellation shows major issues on top of its know limitations in terrestrial networks (TNs). To address these limitations, we propose a solution inspired by the Chinese multimedia digital broadcasting standard (CMMB) standard, adapted for satellite NTN. This approach involves broadcasting a dedicated direct-sequence spread-spectrum (DS-SS) PNT signal on-top of the primary COM signal. This allows for efficient PNT service provision without compromising the performance of the core COM services. By decoupling PNT and COM services, we can optimize the satellite payload design providing wide area coverage for the PNT signal with reduced interference on the COM narrow beams, thus optimizing overall system performance. The proposed solution offers a promising and cost effective approach to enable accurate and reliable PNT services in satellite NTN, even in challenging environments with limited network connectivity.</p>\u0000 </div>","PeriodicalId":50289,"journal":{"name":"International Journal of Satellite Communications and Networking","volume":"43 4","pages":"293-308"},"PeriodicalIF":0.9,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Statistics of Received Power Time Series for Optical LEO Satellite Uplinks 光学LEO卫星上行链路接收功率时间序列统计

IF 0.9 4区计算机科学

International Journal of Satellite Communications and Networking Pub Date : 2025-02-17 DOI: 10.1002/sat.1554

Andrea Carrillo-Flores, Dirk Giggenbach, Marcus T. Knopp

{"title":"Statistics of Received Power Time Series for Optical LEO Satellite Uplinks","authors":"Andrea Carrillo-Flores, Dirk Giggenbach, Marcus T. Knopp","doi":"10.1002/sat.1554","DOIUrl":"https://doi.org/10.1002/sat.1554","url":null,"abstract":"<p>In free-space optical satellite communications, a transmitted optical signal is perturbed by pointing inaccuracies and through the atmosphere's index-of-refraction turbulence. This leads to signal fluctuations and power fading when detected by a receiver. Knowledge of these signal instability statistics is advantageous for the design of robust ground- and space-based optical communication systems. For example, the development of optimized automatic repeat request (ARQ) and forward error correction (FEC) protocols to compensate these losses is facilitated. The channel characteristics of a ground-to-satellite (uplink) and satellite-to-ground (downlink) transmission change with the elevation angle of the link direction, and consequently, the signal fluctuations and power fading also vary. In this work, numerical time series of received power are generated for uplink scenarios to low Earth orbit (LEO) satellites for different satellite elevations. The time series are generated for two experimental scenarios, considering the effects of a gamma-gamma and lognormal-distributed atmospheric scintillation and the use of transmitter diversity. The generated series of power are compared with analytical results and measurements in terms of the run of statistical parameters, and the results are contrasted. The results can be used for link-budget design, for communications standardization, and for the analysis and design of fading mitigation techniques that prevent signal fading and data loss.</p>","PeriodicalId":50289,"journal":{"name":"International Journal of Satellite Communications and Networking","volume":"43 3","pages":"251-263"},"PeriodicalIF":0.9,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/sat.1554","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143889039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Optimization of a LEO-PNT Constellation: Design Considerations and Open Challenges LEO-PNT星座的优化：设计考虑和开放挑战

IF 0.9 4区计算机科学

International Journal of Satellite Communications and Networking Pub Date : 2025-02-16 DOI: 10.1002/sat.1555

Kaan Çelikbilek, Elena Simona Lohan, Jaan Praks

{"title":"Optimization of a LEO-PNT Constellation: Design Considerations and Open Challenges","authors":"Kaan Çelikbilek, Elena Simona Lohan, Jaan Praks","doi":"10.1002/sat.1555","DOIUrl":"https://doi.org/10.1002/sat.1555","url":null,"abstract":"<div>\u0000 \u0000 <p>As the satellite launch and manufacturing costs have become affordable, the industrial and academic interest in low-Earth orbit (LEO) satellites has increased in recent years. With this interest, the concept of LEO-based positioning, navigation, and timing (LEO-PNT) has also gained popularity as a complementary and/or standalone system in addition to the already existing Global Navigation Satellite Systems (GNSS). This article proposes a LEO constellation optimization methodology from the perspective of a LEO-PNT design, identifies and discusses the state-of-art of the LEO satellite constellation optimization approaches, introduces relevant performance- and feasibility-related metrics and parameters, and addresses key concepts and trade-offs that must be considered for any LEO-PNT constellation design. In addition, a case study for a LEO-PNT constellation optimization is presented, where we showcase the discussed trade-offs. We present optimization results obtained with the adaptive weighting algorithm “ADaW” applied to the Pareto-optimization algorithm nondominated sorting genetic algorithm III (“NSGA-III”). A detailed performance analysis is done for six relevant scenarios with varying receiver location properties, namely, by considering indoor/outdoor, rural/urban and line of sight/non–line of sight (NLOS) cases.</p>\u0000 </div>","PeriodicalId":50289,"journal":{"name":"International Journal of Satellite Communications and Networking","volume":"43 4","pages":"272-292"},"PeriodicalIF":0.9,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144299756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Assessment of Practical Satellite Quantum Key Distribution Architectures for Current and Near-Future Missions 当前和近期任务中实用卫星量子密钥分配架构的评估

IF 0.9 4区计算机科学

International Journal of Satellite Communications and Networking Pub Date : 2025-02-14 DOI: 10.1002/sat.1544

Davide Orsucci, Philipp Kleinpaß, Jaspar Meister, Innocenzo De Marco, Stefanie Häusler, Thomas Strang, Nino Walenta, Florian Moll

{"title":"Assessment of Practical Satellite Quantum Key Distribution Architectures for Current and Near-Future Missions","authors":"Davide Orsucci, Philipp Kleinpaß, Jaspar Meister, Innocenzo De Marco, Stefanie Häusler, Thomas Strang, Nino Walenta, Florian Moll","doi":"10.1002/sat.1544","DOIUrl":"https://doi.org/10.1002/sat.1544","url":null,"abstract":"<p>Quantum key distribution (QKD) allows the generation of cryptographic keys beyond the computational hardness paradigm and is befitting for secure data transmission requiring long-term security. The communication distance of fiber-based QKD, however, is limited to a few hundred kilometers due to the exponential scaling of signal attenuation. Satellite QKD (SatQKD) can instead leverage free-space optical links to establish long-range connections and enable global-scale QKD. In this work, we review the manifold of design choices that concur to form the set of possible SatQKD architectures. These include the choice of the QKD protocol and its physical implementation, but also the satellite orbit, the optical link direction, and whether or not to use trusted-node relays. The possible SatQKD architectures are then evaluated in terms of key generation throughput, latency and maximum reachable communication distance, but also system-level security and implementation complexity. Given the technical challenges of realizing SatQKD systems, it is paramount, for near-future satellite missions, to adhere to the simplest possible architecture that still allows to deliver the QKD service. We thus identify as advisable options the use of low-Earth orbit satellites as trusted nodes for prepare-and-measure discrete-variable QKD downlinks with weak laser pulses. The decoy-state version of BB84 is found to be the most promising QKD protocols due to the maturity of the security proofs, the high key generation rate, and low system complexity. These findings are confirmed by the multitude of current and planned SatQKD missions that are adopting these architectural choices.</p>","PeriodicalId":50289,"journal":{"name":"International Journal of Satellite Communications and Networking","volume":"43 3","pages":"164-192"},"PeriodicalIF":0.9,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/sat.1544","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143889041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Robust Beamforming Design for Achievable Secrecy Rate Maximization in IRS-Aided Satellite Systems irs辅助卫星系统可实现保密率最大化的鲁棒波束形成设计

IF 0.9 4区计算机科学

International Journal of Satellite Communications and Networking Pub Date : 2025-02-14 DOI: 10.1002/sat.1550

Fei Li, Yuting Mi, Zining Wang, Changfeng Ding, Min Lin

{"title":"Robust Beamforming Design for Achievable Secrecy Rate Maximization in IRS-Aided Satellite Systems","authors":"Fei Li, Yuting Mi, Zining Wang, Changfeng Ding, Min Lin","doi":"10.1002/sat.1550","DOIUrl":"https://doi.org/10.1002/sat.1550","url":null,"abstract":"<div>\u0000 \u0000 <p>This paper investigates a robust secure transmission design for enhancing the physical layer security (PLS) in an intelligent reflecting surface (IRS)-aided satellite system. Especially since it is challenging to obtain the perfect channel state information (CSI) related to the IRS links, we consider here two different scenarios. Specifically, (1) perfect legitimate users' CSI (LCSI) and imperfect eavesdroppers' CSI (ECSI) are adopted. (2) the case of imperfect LCSI and imperfect ECSI. Under both scenarios, we formulate an optimization problem aiming to maximize the minimal achievable secrecy rate (ASR) among legitimate users subject to quality-of-service requirements and satellite transmit power budget. In order to tackle this nonconvex optimization problem, we propose a robust beamforming (BF) algorithm combining second-order Taylor series expansion and Bernstein-type inequality to jointly optimize transmit power of satellite and phase shifts of IRS. Finally, numerical results confirm the robustness and superiority of the proposed scheme under different CSI uncertainty scenarios.</p>\u0000 </div>","PeriodicalId":50289,"journal":{"name":"International Journal of Satellite Communications and Networking","volume":"43 4","pages":"265-271"},"PeriodicalIF":0.9,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0