Exam in TNE066 Telecommunications – Practice Test

g) Quantization is performed to obtain a digital representation of an analog signal
that has been sampled.
h) The strategy of the OOK modulation technique is to represent digital data as the
presence or absence of a carrier wave.
i) Soft decision decoding typically results in greater performance compared to hard
decision decoding.
j) The Go-back-N ARQ technique is restricted to only send one single data packet
at a time, and an acknowledgement needs to be received before the next packet may
be transmitted.
2. A signal x(t) = sin(500πt) is sampled and then reconstructed ideally. Determine the
output y(t) after ideal reconstruction if the sampling frequency f s is:
a) f s = 600 Hz. (2p)
b) f s = 300 Hz. (2p)
3. A step-index fiber is surrounded by air. The cladding has refraction index 1.2 and the
core has refraction index 1.4.
a) Determine the angle of refraction if the light in the core reaches the junction
between the core and the cladding with an angle of incidence that is 40 o . (1p)
b) Determine the critical angle of the core/cladding junction. (1p)
c) Determine the acceptance half angle of the fiber. (1p)
d) Briefly describe two types of losses that are associated with optical fiber. (1p)
4. A memoryless source produces the symbols A, B, C, D, E, F, G, H with the
probabilities P A = 0.28, P B = 0.20, P C = 0.15, P D = 0.06, P E = 0.18, P F = 0.05, P G
= 0.07, P H = 0.01.
a) Determine the average codeword length that can be achieved with a tree code
(Huffman code) which encodes one symbol at a time. (2p)
b) Calculate the compression ratio and the redundancy. (2p)