For a few years, multicarrier modulations have been proposed as valuable alternatives with respect to state-of-the-art single carrier ones due to their resilience against interference and channel distortion effects. In particular, many studies are arising about multicarrier-CDMA (MC-CDMA) techniques that provide improved robustness and flexibility with respect to single-carrier spread-spectrum ...

This paper will present the methods adapted to model low earth orbiting (LEO) spacecraft support and an actual implementation of this approach. The results of a comparison of actual human schedulers' performance and the support schedules developed by using the proposed modeling approach will be presented. Indications based on two years of performance tracking of the new approach are that modeli...

A technique for satellite formation flying modelling in LEO is applied at L2. Analytical solutions to the equations of motion of a hub satellite relative to L2 are used to define a halo reference orbit. An expression for the gravity gradient is obtained at the hub and the linearised equations of motion of the mirror satellites relative to the hub are derived. The relative motion model is implem...

A satellite communications system is based on antennas in a stable orbit above the earth. Satellites serve as relay stations in the sky. The basic idea of satellite communications is that two stations on earth discuss via one or more satellites. So a little bit of satellite-related terminology: 1. Earth station is an antenna on or near the surface of the earth. 2. Uplink is a transmission from ...

The Universal Mobile Telecommunications System (UMTS) will provide multimedia services to users in whatever environment via uniform service access procedures. Efficient Medium Access Control (MAC) protocols are needed to guarantee high capacity. This paper deals with Packet Reservation Multiple Access (PRMA), an efficient MAC protocol that has been widely studied in terrestrial microcellular sy...

We present a spectroscopic study of Leo V, a recently discovered satellite of the Milky Way (MW). From stellar spectra obtained with the MMT/Hectochelle spectrograph we identify seven likely members of Leo V. Five cluster near the Leo V center (R < 3) and have velocity dispersion 2.4 −1.4 km s. The other two likely members lie near each other but far from the center (R ∼ 13 ∼ 700 pc) and inflat...

The GPS meteorology (GPS/MET) experiment, led by the Universities Corporation for Atmospheric Research (UCAR), consists of a GPS receiver aboard a low earth orbit (LEO) satellite which was launched on 3 April 1995. During a radio occultation the LEO satellite rises or sets relative to one of the 24 GPS satellites at the Earth's horizon. Thereby the atmospheric layers are successively sounded by...

This paper presents the evaluation performance of a hybrid satellite constellation network which provides internet access based on various Transport Control Protocol (TCP). Given known constraints on the hybrid satellite constellation resulting from network performance evaluation criteria. The evaluated satellite network uses the COMMStellation constellation topology operating on Low Earth Orbi...

Two different routing algorithm categories are studied in this paper for a typical LEO satellite constellation. Shortest path algorithms and optimal routing. Their performance is investigated through extended real time simulations. In the context of satellite constellations the basic parameters for a typical network such as delay, throughput, link utilization must be supplemented by new factors...