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  1. Book ; Online: Adapting to Dynamic LEO-B5G Systems

    Yuan, Yaxiong / lei, Lei / Vu, Thang X. / Chang, Zheng / Chatzinotas, Symeon / Sun, Sumei

    Meta-Critic Learning Based Efficient Resource Scheduling

    2021  

    Abstract: Low earth orbit (LEO) satellite-assisted communications have been considered as one of key elements ... we address two practical issues for an over-loaded LEO-terrestrial system. The first challenge is how ...

    Abstract Low earth orbit (LEO) satellite-assisted communications have been considered as one of key elements in beyond 5G systems to provide wide coverage and cost-efficient data services. Such dynamic space-terrestrial topologies impose exponential increase in the degrees of freedom in network management. In this paper, we address two practical issues for an over-loaded LEO-terrestrial system. The first challenge is how to efficiently schedule resources to serve the massive number of connected users, such that more data and users can be delivered/served. The second challenge is how to make the algorithmic solution more resilient in adapting to dynamic wireless environments.To address them, we first propose an iterative suboptimal algorithm to provide an offline benchmark. To adapt to unforeseen variations, we propose an enhanced meta-critic learning algorithm (EMCL), where a hybrid neural network for parameterization and the Wolpertinger policy for action mapping are designed in EMCL. The results demonstrate EMCL's effectiveness and fast-response capabilities in over-loaded systems and in adapting to dynamic environments compare to previous actor-critic and meta-learning methods.

    Comment: 12 pages, 9 figures
    Keywords Electrical Engineering and Systems Science - Signal Processing ; Computer Science - Artificial Intelligence ; Computer Science - Machine Learning
    Subject code 006
    Publishing date 2021-10-13
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Book ; Online: Cox Point Processes for Multi-Altitude LEO Satellite Networks

    Choi, Chang-Sik / Baccelli, François

    2023  

    Abstract: To model existing or future Low Earth Orbit (LEO) satellite networks with multiple constellations ... we propose a simple analytical approach to represent the clustering of LEO satellites on orbits, based ... the evaluation of the performance of LEO satellite communication systems as functions of network parameters ...

    Abstract To model existing or future Low Earth Orbit (LEO) satellite networks with multiple constellations, we propose a simple analytical approach to represent the clustering of LEO satellites on orbits, based on a Cox point process. More precisely, we develop a variable-altitude Poisson orbit process that effectively captures the geometric fact that satellites are always positioned on orbits, and these orbits may vary in altitude. Conditioned on the orbit process, satellites situated on these orbits are modeled as Poisson point processes, thereby forming a Cox point process. For this model, we derive useful statistics, including the distribution of the distance to the nearest visible satellite, the outage probability, the Laplace functional of the proposed Cox satellite point process, and the Laplace transform of the interference from the Cox-distributed satellites under general fading. The derived statistics enable the evaluation of the performance of LEO satellite communication systems as functions of network parameters.

    Comment: Submitted to IEEE Journal
    Keywords Electrical Engineering and Systems Science - Signal Processing ; Computer Science - Information Theory ; Mathematics - Probability
    Publishing date 2023-01-06
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Book ; Online: A Novel Analytical Model for LEO Satellite Constellations Leveraging Cox Point Processes

    Choi, Chang-Sik / Baccelli, François

    2022  

    Abstract: This work develops an analytical framework for downlink Low Earth Orbit (LEO ... incorporate this geometric property of LEO satellite constellations by developing a Cox point process model ... allows one to assess the statistical properties of downlink LEO satellite communications and can thus be ...

    Abstract This work develops an analytical framework for downlink Low Earth Orbit (LEO) satellite communications, leveraging tools from stochastic geometry. We propose a tractable approach to the analysis of such satellite communication systems, accounting for the fact that satellites are located on circular orbits. We accurately incorporate this geometric property of LEO satellite constellations by developing a Cox point process model that jointly produces orbits and satellites on these orbits. Our work contrasts with previous modeling studies that presumed satellite locations to be entirely random, thereby overlooking the fundamental fact that satellites are exclusively positioned on orbits. Employing this new Cox model, we analyze the network performance experienced by users anywhere on Earth. Specifically, we evaluate the no-satellite probability of the proposed network and the signal-to-interference-plus-noise ratio (SINR) distribution, or the coverage probability. By presenting fundamental network performance as functions of network key parameters, this work allows one to assess the statistical properties of downlink LEO satellite communications and can thus be used as a system-level design tool to operate, design, and optimize forthcoming complex LEO satellite networks.

    Comment: Submitted to IEEE Journal
    Keywords Electrical Engineering and Systems Science - Signal Processing ; Computer Science - Information Theory
    Publishing date 2022-12-07
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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    Inter-library loan at ZB MED

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  4. Book ; Audio / Video: Hil leo

    I, Jeong seob / Gim, Jin u / Ji, Chang ug / Bag, Min yeong / Chi, Ch'ang-uk / Kim, Chin-u / Pak, Min-yŏng / Yi, Chŏng-sŏp

    = Healer

    2015  

    Author's details Regie: I Jeong seob
    Language Korean
    Size 7 DVD-Videos
    Publisher Gim Jong hag peu lo deog syeon
    Publishing place s. l.
    Document type Book ; Audio / Video
    Database Former special subject collection: coastal and deep sea fishing

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    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  5. Book ; Audio / Video: Hil leo

    I, Jeong seob / Gim, Jin u / Ji, Chang ug / Bag, Min yeong / Chi, Ch'ang-uk / Kim, Chin-u / Pak, Min-yŏng / Yi, Chŏng-sŏp

    = Healer

    2015  

    Author's details Regie: I Jeong seob
    Language Korean
    Size 6 DVD-Videos
    Publisher Gim Jong hag peu lo deog syeon
    Publishing place s. l.
    Document type Book ; Audio / Video
    Database Former special subject collection: coastal and deep sea fishing

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    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  6. Book ; Audio / Video: Hil leo

    I, Jeong seob / Gim, Jin u / Ji, Chang ug / Bag, Min yeong / Chi, Ch'ang-uk / Kim, Chin-u / Pak, Min-yŏng / Yi, Chŏng-sŏp

    = Healer

    2015  

    Title variant Migonggae OST, kamdokp'an oe puga yŏngsang
    Author's details Regie: I Jeong seob
    Language Korean
    Size 2 DVDs
    Publisher Gim Jong hag peu lo deog syeon
    Publishing place s. l.
    Document type Book ; Audio / Video
    Database Former special subject collection: coastal and deep sea fishing

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    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  7. Book ; Audio / Video: Hil leo

    I, Jeong seob / Gim, Jin u / Ji, Chang ug / Bag, Min yeong / Chi, Ch'ang-uk / Kim, Chin-u / Pak, Min-yŏng / Yi, Chŏng-sŏp

    Healer

    2015  

    Title variant Hillŏ ; Healer
    Author's details Regie: I Jeong seob
    Language Korean
    Size 13 DVD-Videos (Region: 1, 3, 4-6), 1231 + 736 Min.
    Publisher Gim Jong hag peu lo deog syeon
    Publishing place s. l.
    Document type Book ; Audio / Video
    Note Sprache: Koreanisch ; Aufnahmejahr: 2014-2015
    Accompanying material 6 Beihefte
    Database Former special subject collection: coastal and deep sea fishing

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    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  8. Book ; Online: A hybrid beamforming design for massive MIMO LEO satellite communications

    Palacios, Joan / Gonzalez-Prelcic, Nuria / Mosquera, Carlos / Shimizu, Takayuki / Wang, Chang-Heng

    2021  

    Abstract: 5G and future cellular networks intend to incorporate low earth orbit (LEO) satellite communication ... simulate the downlink of a LEO SatCom compatible with 5G NR, with a special focus on the design ... a LEO satellite and a mobile terminal in the Ku band, assuming a realistic channel model and commercial ...

    Abstract 5G and future cellular networks intend to incorporate low earth orbit (LEO) satellite communication systems (SatCom) to solve the coverage and availability problems that cannot be addressed by satellite-based or ground-based infrastructure alone. This integration of terrestrial and non terrestrial networks poses many technical challenges which need to be identified and addressed. To this aim, we design and simulate the downlink of a LEO SatCom compatible with 5G NR, with a special focus on the design of the beamforming codebook at the satellite side. The performance of this approach is evaluated for the link between a LEO satellite and a mobile terminal in the Ku band, assuming a realistic channel model and commercial antenna array designs, both at the satellite and the terminal. Simulation results provide insights on open research challenges related to analog codebook design and hybrid beamforming strategies, requirements of the antenna terminals to provide a given SNR, or required beam reconfiguration capabilities among others.
    Keywords Electrical Engineering and Systems Science - Signal Processing
    Publishing date 2021-04-22
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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    Inter-library loan at ZB MED

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  9. Article: GOES-16/ABI Thermal Emissive Bands Assessments using GEO-LEO-GEO Double Difference.

    Chang, Tiejun / Xiong, Xiaoxiong

    Earth and space science (Hoboken, N.J.)

    2019  Volume 6, Issue 12, Page(s) 2303–2316

    Abstract: Geostationary satellite (GOES)-16/ABI and Himawari-8/AHI represent a significant improvement over the imagers on board previous GOES. Their bands 7-16 are infrared channels covering the 3.9 to 13.3 μm spectral range and with a sub-point spatial ... ...

    Abstract Geostationary satellite (GOES)-16/ABI and Himawari-8/AHI represent a significant improvement over the imagers on board previous GOES. Their bands 7-16 are infrared channels covering the 3.9 to 13.3 μm spectral range and with a sub-point spatial resolution of 2 km. Their spectral coverage of the thermal emissive bands (TEB) are almost identical and both instruments employ similar calibration strategies using an on-board blackbody (BB) and a space look. The inter-comparison between the two instruments will be very helpful for their calibration assessments and their product quality enhancements. GOES-16 was launched on November 19, 2016, initially to a test position at 89.5° West and reached its operational position (longitude of 75.2° West) on December 11, 2017. The Himawari-8 spacecraft was launched on October 7, 2014 and the observation focuses on Asia-Pacific region. In this work, an inter-comparison of their TEB measurement is performed using double difference with Aqua MODIS. The same type of scenes are selected for the two instruments and their measurements with the closest observation times are compared with Aqua MODIS matching bands. The view angle effect is corrected and their spectral mismatching effect is estimated. The dependence on the scene uniformity is analyzed. The ABI-AHI differences are within 0.3K for bands 10 (7.35 μm), 11 (8.44 μm), 12 (9.64 μm), and 14 (11.24 μm), and up to 0.8K difference for bands 15 (12.38 μm) and 16 (13.28 μm). The ABI precision is better than AHI for all TEB and their image navigation and registration (INR) precisions are comparable. In general, the ABI performance before and after re-location is consistent.
    Language English
    Publishing date 2019-11-07
    Publishing country United States
    Document type Journal Article
    ZDB-ID 2807271-6
    ISSN 2333-5084
    ISSN 2333-5084
    DOI 10.1029/2019ea000617
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Impact of GPS receiver antenna GRAPHIC residual variations on single-frequency orbit determination of LEO satellites

    Shao, K. / Gu, D. / Chang, X. / Yi, B. / Wang, Z.

    Advances in Space Research

    2019  

    Publishing country de
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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