1) A broadcaster transmits its program over a geosynchronous satellite. The upli
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Question
1) A broadcaster transmits its program over a geosynchronous satellite. The uplink and downlink carrier frequencies are 14 GHz and 12 GHz, respectively. The distance from the satellite to the gateway and the the receiver can both be approximated as 36,000 km. Assume that the uplink (the Gateway) antenna has a gain of 45 dBi, the receiver on the satellite has an antenna with a gain of 40 dBi and a noise temperature of 3500° K. The trnamitter onboard the satellite has a gain of 45 dBi and a power of 100 W Receiver on the ground has an antenna gain of 15 dBi and a nosie temperature of 250 K. Modulation used is QPSK with a roll-off factor of 0.25 (error control coding is not used). a) b) Find the required bandwidth if the bit rate is 3 Mbps. Find the uplink transmitter power if the operator wants to have no more than one packet in error per hour.Explanation / Answer
a)
BandWidth = (1+ roll of factor)*symbol rate
Now,
bit rate = symbols * (numbers of bit/ symbol)
bit rate = 3Mbps = 3x10^6 bps
numbers of bit / symbol = 2 (QPSK Modulation)
symbol rate = (3x10^6 bps ) / 2 = 1.5x10^6 bps/S
Therefore,
BandWidth = ((1 + 0.25) x 1.5x10^6 bps/S) ~ 1.85 x 10^6 bps/S (or 1.85Mbps/S)
---------------------------------------------------------------------------------------------------------------------------------------------------------b)
Effective Isotropic Transmission Power (EIRP) for Uplink:
EIRP = 10 log (Transmitter power /Carrier )-Transmitter Feeder loss + Transmitter Antenna Gain – Antenna Pointing Loss (db W)
Transmitter power /Carrier = 10log10( Pi/1x10^-3) = 50dBm
Transmission Antenaa Gain = 45dbi
EIRP = 50 + 45 = 95dB
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