In this problem we address the uplink power budget of the digital satellite communication system considered in Example 8.2. The parameters of the link are as follows:

Carrier frequency? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?= 14 GHz

Power density at the TWT amplifier in saturation? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? = ? 81dbW/m²

Satellite figure of merit, G/T? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?= 1.9 dB/K

Distance of the satellite from the transmitting earth terminal ? ? ? ? ? ?= 40,000 km

(a) Assuming no power back off of the TWT, calculate the C/N₀ ratio at the satellite.

(b) Given that the data rate in the uplink is the same as that calculated for the downlink in Example 8.2, calculate the probability of symbol error incurred in the uplink allowing for a link margin of 6 dB. Compare your result with that in Example 8.2.

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Carrier frequency Power density at the TWT amplifier in saturation Satellite figure of merit, G/T Distance of the satellite from the transmitting earth terminal = 14 GHz = -81 dBW/m² 1.9 dB/K = 40,000 km