Important information about Examination of a digital radio link

A. A digital radio link operates at a frequency of 75 MHz and uses ideal RRC filters with nroll off factor r = 0.2 in the transmitter and receiver. The modulation used on the link is BPSK and the bit rate is 100 kbps. The 75 MHz transmitter has an output power of 1.0 W.
Calculate the bandwidth occupied by the transmitted radio signal.

b. At the receiver of the radio link described in part (a) above, the CNR measured in clear air conditions is 15.5 dB. The link has an implementation margin of 0.5 dB. Calculate the approximate BER at the receiver output and choose an appropriate value from the following.

3 × 10-5 2 × 10-7 4 × 10-10 6 × 10-12 0

c. The modulation on the link is changed to Gray coded QPSK and the bit rate is increased to 200 kbps. The output power of the 75 MHz transmitter is increased to 2.0 W. All other parameters of the link are unchanged. Calculate the approximate BER at the receiver output.