ELEC0020-A5U 2021 List of physical constants:…

ELEC0020-A5U 2021
List of physical constants:
Velocity of propagation of an electromagnetic wave in vacuum: c = 3 x 108 m-s-1 Permittivity of vacuum or air: eo = 8.85 x 10-12 Fm-1 Permeability of vacuum or air: t0 = 47/- x 10-7 I-Im-1 Planck constant: h = 6.63 x 10-34 J.s Charge on an electron: e = 1.60 x 10-19 C Boltzmann constant: k = 1.38 x 10-23 J.K-1
Answer ALL questions
SECTION A Answer BOTH questions from Section A (each question is worth 25 marks) 1. Consider a baseband digital signal given by: x(t) = V:=_00 Xk p(t kTs), (Equation 1.1)
where p(t) is a unit-energy square pulse with

ELEC0020-A5U 2021
List of physical constants:
Velocity of propagation of an electromagnetic wave in vacuum: c = 3 x 108 m-s-1 Permittivity of vacuum or air: eo = 8.85 x 10-12 Fm-1 Permeability of vacuum or air: t0 = 47/- x 10-7 I-Im-1 Planck constant: h = 6.63 x 10-34 J.s Charge on an electron: e = 1.60 x 10-19 C Boltzmann constant: k = 1.38 x 10-23 J.K-1
Answer ALL questions
SECTION A Answer BOTH questions from Section A (each question is worth 25 marks) 1. Consider a baseband digital signal given by: x(t) = V:=_00 Xk p(t kTs), (Equation 1.1)
where p(t) is a unit-energy square pulse with duration Ts, Ts is the symbol period and k is an integer. It is assumed that the sequence of symbols {Xk} is independent. It is also assumed that the symbols Xk are drawn from an alphabet cil = t-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]
(b) Assume that the 8-PAM signal is received using an ideal detector with the received signal y(t) related to the transmitted signal x(t) by:
y(t) = x(t) + n(t) (Equation 1.2)
where n(t) is additive white Gaussian noise. The symbols are equiprobable, and the energy per symbol-to-noise ratio, fs/No = 13 dB.
(i) Using either Q-function or complementary error function (erfc) expressions for symbol error rate for polar baseband signals, find the symbol error rate.
[7 marks]
(ii) Explain how the 3-bit codes can be assigned to the PAM levels to ensure that the bit error rate is not significantly greater than the symbol error rate.
Page 1 of 8
[2 marks]
TURN OVER

Attachments:

12344.pdf