1. Consider a baseband digital signal given by: x(t) = k=-o Xkp(t - kTs), (Equation 1.1) where p(t) is a unit-energy square pulse with duration T, T, is the symbol period and k is an integer. It is assumed that the sequence of symbols {X} is independent. It is also assumed that the symbols X are drawn from an alphabet A = {-7A, -5A, -3A, -A, A, 3A, 5A, 7A) of equal probability for 8-ary Pulse Amplitude Modulation (8-PAM) transmission. (a) For such a transmitted signal with symbol period of 10 ns: (i) Find its power spectral density. [5 marks] (ii) State its bandwidth and spectral efficiency, and the (average) energy per symbol. [5 marks]