Low Earth Orbit (LEO) satellites are an essential complement of the cellular radio infrastructure, especially the Universal Mobile Telecommunications System (UMTS), for mobile (pedestrian and, more important, vehicular) access to the Internet in sparsely populated areas, where high bandwidth UMTS cells cannot be economically deployed. LEO users would eventually switch between the satellite segm...

Notwithstanding the limited commercial success of the first narrowband Low Earth Orbit (LEO) satellite systems, the interest of the scientific community in this type of systems has been revived on the basis of the current trend toward the migration to all IP-based services. LEO systems can play a pivotal role in providing services to areas where there is no substantial terrestrial infrastructur...

We have obtained spectra of three QSO/AGNs with the GHRS aboard the Hubble Space Telescope to search for absorption from low column density gas in the halo of the dwarf spheroidal (dSph) galaxy Leo I. The probe sightlines pass 2.1, 3.7, and 8.1 kpc from the center of the galaxy, but no C IV, Si II, or Si IV absorption is found at the velocity of Leo I. The absence of low ionization species sugg...

Low earth orbit (LEO) satellite systems allow a broad range of services to be provided using small, lightweight, cellular-like portable telephones. Exploiting LEO satellites to support distress signals for aircrafts, ships and international travelers is explored in the current paper. A multi-service priority-oriented algorithm is proposed for handling voice, data and emergency signals over LEO ...

14-3-3 proteins have been shown to interact with Raf-1 and cause its activation when overexpressed. However, their precise role in Raf-1 activation is still enigmatic, as they are ubiquitously present in cells and found to associate with Raf-1 in vivo regardless of its activation state. We have analyzed the function of the Drosophila 14-3-3 gene leonardo (leo) in the Torso (Tor) receptor tyrosi...

Among satellite systems, low earth orbit (LEO) satellite system will make an important role in new fiture communication services, because of its less propagation delay, less power consumption in the user terminal and the satellites, and efficient spectrum utilization using smaller coverage area for each satellite than geostationa y (GEO) counterpart. However, a number of mobility problems that ...

Low Earth Orbit Satellite Networks can augment terrestrial wireless networks to provide global broadband services to users regardless of the users’ locations. Delivering QoS guarantees to the users of LEO satellite networks is complicated since footprints of LEO satellites move as the satellites traverse their orbits, and thus, causing frequent user handovers between the satellites. Traffic on ...

We present Giant Meterwave Radio Telescope (GMRT) and Westerbork Synthesis Radio Telescope (WSRT) observations of the recently discovered Local Group dwarf galaxy, Leo T. The peak H I column density is measured to be 7× 10 cm, and the total H I mass is 2.8× 10 M⊙, based on a distance of 420 kpc. Leo T has both cold (∼ 500 K) and warm (∼ 6000 K) H I at its core, with a global velocity dispersion...

Mobility management is an important aspect in LEO (low earth orbit) systems. In terrestrial wireless networks, the movement of the user triggers location updating and determines the paging scheme, while in LEO satellite systems, the location updating and paging is mainly based on the movement of satellite. Terrestrial location management techniques must be altered to fit the LEO systems. This p...

Free space optical communication provides a very important method for the satellites orbiting around the earth to communication with each other. In this paper , optical intersatellite link is modelled using optisystem software and then the effect of varying the transmitter power and aperture diameter of transmitter and receiver telescopes is analysed. The results shows that large transmitter po...