(a) Describe the four functions of the physical layer in the Internet Model.

(b) (i) With the help of a diagram describe the main stages involved in the digitization of analog signals using Pulse Code Modulation
(PCM).

(ii) The table below shows the amplitude values of five analog signals. Assuming a 0 bit for negative values and a 1 bit for positive values and using an 8-bit signed PCM coding system give their corresponding codeword.

(c) What is the bandwidth of a signal that can be decomposed into five sine waves with frequencies at 0, 40, 70, 110, 150 and 400 Hz?
Assume all peak amplitudes are the same.

Draw the bandwidth.

(d) Name three categories of multiple access protocols.

(e) You are given the following Constellation Diagram. The amplitudes are 2, 4, 6 and 8 volts.

(i) What is the total number of data items that are represented in the diagram?

(ii) What is the minimum number of bits per signal required to code all the data on the constellation diagram?

(iii) Draw and fill the corresponding table for this constellation diagram (Giving all possible combination in the data set, the phase angle and the amplitude).

(iv) Give an appropriate name for this type of Constellation diagram.