Consider an LEO satellite system orbiting 500 km above the earth. Assume that the signal follows a free-space path-loss model with no multipath fading or shadowing. The transmitted signal has a carrier frequency of 900 MHz and a bandwidth of 10 kHz. The handheld receivers have noise power spectral density of 10⁻¹⁶ mW/Hz (total noise power is N0*B) Assume nondirectional antennas (0-dB gain) at both the transmitter and receiver. Suppose the satellite must support users in a circular cell on the earth of radius 100 km at a BER of 10⁻⁶.
(a) For DPSK modulation, find the transmit power needed for all users in the cell to meet the 10⁻⁶ BER target.
(b) Repeat part (a) assuming that the channel also experiences log-normal shadowing with σψdB = 8 dB and that users in a cell must have Pb = 10⁻⁶(for each bit) with probability 0.9.