Satellite Radio: The Next
Communications
Revolution?
David Bultman
Challenges In Satellite Radio
There are three general problems with
satellite reception:
 Blockages
 Foliage
 Multipath Fading
Blockages
The target of satellite radio is a mobile
platform
 This rules out the use of special high gain
antennas and expensive satellite tracking
systems
 The important factors to think about when
considering blockages are the movement
of the receiver, the movement of the
satellite, and the angle of elevation of the
satellite
Foliage
Foliage is similar to a blockage with a few
exceptions
 Foliage can block or attenuate a signal
 The amount of attenuation can depend on
the type of foliage, the frequency of the
signal, and the incident angle
 Foliage can also reflect a signal with a
random amount of attenuation and phase
shift
Multipath Fading

Multipath Fading occurs multiple forms of the
original signal are received
Solutions – Spatial Diversity
Spatial Diversity = Instead of having a single signal source, use
multiple signal sources spread out
 Spatial Diversity helps fix all three of the problems
Solutions – Frequency Diversity
Frequency Diversity = Sending the same information on two separate
and unrelated frequencies (preferably also spatially diverse)
 Frequency Diversity is aimed at fixing multipath fading
Solutions – Time Diversity
Time Diversity = Delaying one of two spatially diverse signals in time
before its broadcast
 Time Diversity is aimed at eliminating audio outages when both
broadcast signals are blocked simultaneously
Solutions – Repeater Stations
Repeater Stations are used in areas where even the
combination of the other three solutions may not yield a
“good” signal
XM Radio’s System
Two geostationary satellites with a 45
degree angle of elevation
 Each satellite emits about 10MW of signal
energy
 Approximately 1500 low power repeater
stations serving 70 markets

Sirius Radio’s System


Three satellites in an
inclined elliptical orbit
Each satellite spends
about 16 hours over
the US, with two
satellites always
above the equator
Sirius Radio’s System
The satellites are inclined at 60 degrees
 The satellites are of lower power than XM
Radio’s
 105 high power repeaters serving 46
markets

The Future?
From all indications the audio quality is
superb with both providers
 The tests will be subscriber numbers and
the possibility of terrestrial radio adding
digital signals to their broadcasts to
compete
