Assignment:
A direct-to-home satellite television system uses a geostationary satellite in orbit above the equator at a longitude of 109 degrees west.
The parameters of the satellite transmission are as follows:
- Transmit power 160 dBW
- Transmit antenna gain (edge of coverage) 31 dB
- Distance to earth 38,500 km
- Transmission frequency 12.5 GHz
- Atmospheric and other losses 1.0 dB
The receiving earth station has the following parameters.
- Receiving antenna gain 34 dB
- Receive system noise bandwidth 30 MHz
- System noise temperature in clear air 90 K
a. Calculate the path loss Lp for the link. Remember to put R into meters.
b. Calculate the power received Pr, by a receiving terminal (earth station) at the edge of the satellite transmit beam (edge of coverage area).
c. Calculate the noise power, N, in the receiver, in dBW.
d. Hence find the CNR in the receiver in clear air conditions.
e. The transmissions from the satellite use QPSK modulation and the earth station receiver has an implementation margin of 0.2 dB. Find the average BER at the receiver output in clear air conditions.
f. Rain causes the CNR to fall by 4 dB. Recalculate the BER. If the BER has risen above 10^-6, suggest one way in which it could be reduced to an acceptable level (say < 10^-8).