Exercise 3 (8.-12.2) (Tanenbaum pp. 77 -122)

1.Answer shortly the following questions ("review type" problem: answers are found  in  lecture
     notes or in Tanenbaum's book).
    a) Why is digital data transmission less error prone than analog data transmission?
    b) Why digital signals cannot be carried as such over telephone lines using analog signalling?
    c) The coaxial cable can be used for data transmission in two different ways: Baseband or
         Broadband.  Explain what they mean.
    d) What are attenuation and distortion. Why do they happen?
    e) How are rates in  bps and  in baud related to each other?

2. Copper, fiber or wireless? Who has the future?

3. a) How do the theorems of Nyquist and Shannon relate to each other?
    b) Is the Nyquist theorem true for optical fiber, or only for copper wire?

4. a) A noiseless 4-kHz channel is sampled every 1 msec. What is the maximum data rate?
     b) If a binary signal is sent over a 3-kHz channel whose signal-to-noise ratio is 20dB, what is
         the maximum achievable rate?
     c) What signal-to noise ratio is needed to put a T1 carrier on a 50-kHz line?

5. a) The bandwidth is 6000 Hz. What is the highest theoretical rate, if in amplitude modulation each
         signal component encodes 1, 2 or 4 bits?
     b) How high frequency at least is needed if performance requires 30 000 bps and each signal
           component  carries one bit? What if each signal component encodes four bits?

6. Explain the structure of the constellation pattern diagram. Below there are two diagrams  (x is a
    constellation dot, ....  figures the axis ).  What kind of digital to analog modulation do they specify?

                   x                                                       x       x     .    x        x
                   .                                                                         .
                   .                                                        x       x     .    x        x
      x   .    .    .    .    x                                           .    .    .     .     .    .    .
                   .                                                        x       x     .    x        x
                   .                                                                         .
                  x                                                        x      x      .    x        x

               V.22                                                            V.22 bis

The transmission rate is 600 baud. What is the transmission rate  in  bps?
 

At least three problems should be solved including problem 1.