نتایج جستجو برای: satellite communications
تعداد نتایج: 157046 فیلتر نتایج به سال:
The operation of a ROV requires significant off-shore dedicated manpower to handle and operate the robotic platform. In order to reduce the burden of operations, DexROV proposes to work out more cost effective and time efficient ROV operations, where manned support is in a large extent delocalized onshore (i.e. from a ROV control center), possibly at a large distance from the actual operations,...
New approach for modelling a physical hysteresis damping the flexible spacecraft structure oscillations, is developed. New results on communication satellite attitude guidance and digital robust control with precise pointing the large-scale flexible antennas, are presented.
The possibility of employing the same spacecraft at several orbital locations, changing the coverage region, and compensating for varying weather conditions are the main reasons why reconfigurable antennas for contoured beam generation can provide significant advantages in satellite communications. Though extremely attractive in terms of cost and manufacturing, shaped reflectors lack so far the...
In this paper we propose an elevation-dependent Rice Rayleigh/lognormal channel model for communications of personal and mobile users via non-geostationary satellites (NGSO S-PCNs). Based on this channel model, we discuss the performance of satellite diversity for NGSO SPCNs. The parameters of the channel model are derived from channel measurements, which have been carried out for different ele...
This paper summarizes the the activities carried out by Working Group 4 of COST 271 Action. The structure of this Working Group included four Working packages that were dealing with different aspects of the same overall problem related to space plasma variability and irregularities effects on advanced satellite systems. General comments about the most relevant achievements and possible future l...
By its nature, the satellite sector is the most “pan-European” of all communications infrastructures and services. Unlike any terrestrial network, satellite networks can provide coverage to all parts of Europe. This strength of satellite networks, nonetheless, creates a great regulatory challenge. Due to wide satellite coverage, operators depend on harmonized spectrum allocations. The services ...
In this paper we present a simple model for satellite constellations with polar orbits and inter-satellite links. This model is used to propose and study two algorithms for routing and re-routing communications, which aim at improving the quality of service for long communications. In order to study these algorithms, we have developed a satellite constellation simulator. Some of its results
New approach for modelling a physical hysteresis damping the flexible spacecraft structure oscillations, is developed. New results on communication satellite attitude guidance and digital robust control with precise pointing the large-scale flexible antennas, are presented.
Simulation Study on Performance Evaluation of MF-TDMA-based Military Satellite Communication Systems
The multi-frequency time-division multiple access (MF-TDMA) has become general in satellite communications. In this paper, we developed a simulation model for MF-TDMA-based satellite networks using OPNET simulator. With the simulator, we evaluated the efficient use of DAMA schemes using MF-TDMA compared to PAMA based on FDMA.
Communication satellites have been in commercial use for more than three decades. Driving their early deployment were military communications , international telephony, and broadcast TV. Now these same satellites are being used to transport TCP/IP traffic between distant locations , and to offer Internet access. Satellites have thus become the celestial link of the global Internet, an " instant...
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