The satellites that make up the system are
located on a number of orbital planes, which are equally
distributed along a common axis that passes through the centre of
the earth.
Inclination:
It is the angle formed by the intersection of
an orbital plane with the equator. It can vary from zero (equator)
to ninety degrees (polar orbit).
Period:
Time it takes a satellite to travel an entire
orbit.
Average satellite visibility time:
Time in which it is possible to see a satellite
from a fixed point on earth.
Minimum elevation angle of the terminal:
Angle formed by the earth's surface and by the
imaginary conductor that unites the mobile terminal to the
satellite.
Single delay:
Propogation time needed for the radio signal to
reach the satellite from the mobile terminal or vice versa.To
obtain the complete delay (round trip), you must double this
value.
Number of Gateways on Earth:
Number of land radio stations which, through
the satellite links, are responsible of interfacing mobile
terminals with the terrestrial telephone network.
Voice:
Speed used for conversation transmission.
Data:
Speed used for data and fax transmission.
Number of Voice Circuits per satellite:
Number of conversations that a satellite can
maintain simultaneously. (To be evaluated together with the
diametre of the beam).
Dual-Mode Terminals:
Network predisposed to the use of dual-mode
terminals, capable of using a terrestrial cellular network and a
satellite network alternatively based upon the radio coverage and
the roaming agreements.
Beams per satellite:
Number of radio signals transmitted
simultaneously to each satellite of the constellation.
Beams per satellite:
Number of radio signals transmitted through
directional antennas used by every satellite in the constellation.
Diametre of one beam:
Diametre of the radio signal transmitted from
every directional antenna.
Diametre of the footprint:
Diametre of the area on the earth's surface
covered by each satellite.
Types of cells:
Mobiles: Radio cells move together with
the constellation, with respect to the earth's surface. Fixed: Radio cells are fixed on the earth's surface even if
the constellation is rotating.
On Board Processing:
On board the satellite there are computers that
communicate with the other satellites. This makes it possible to
carry on a conversation between two subscribers who find
themselves connected to different satellites, without passing
through the terrestrial gateways.
