Q.1 (a) With the aid of suitable diagrams, briefly explain the layers in Open Systems Interconnection (OST)-seven layer model (7 marks) (b) A fully connected mesh topology has 6 stations connected to a network, ( (10) Draw the block diagram of this mesh network; How many connection links are used in the network? (4+3 = 7 marks) (c) Use a suitable table to compare the characteristic features of IP addresses and Physical addresses (4 marks) (d) Briefly describe, with the aid of suitable diagrams, the hierarchy in the IPv4 addressing (5 marks) (e) If a classful address is 172.0.0.1, what are the class and the block of this address? (2 marks) Total: (25 marks) Q. 2 (a) A classless address is given as being 136.148.5.67/25. Find its three pieces of information as follows. The number of addresses in a given network, The first address in this network; The last address in the network. (7 marks) (b) Describe with suitable diagrams, Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). Compare the characteristio features of TCP and UDP (10 marks) (c) Explain the flow control and error control in Data Link laver Q.3 (a) What are typical transmission media used in wireline computer networks? Comment on which medium has the largest transmission bandwidth (5 marks) (b) Assume that the channel bandwidth is 2 MHz and its Signal-to-Noise Ratio (SNR) is equal to 70. (i) (ii) What is the upper limit to the channel capacity? Determine the maximum value for the number of signal levels (L). (4+3 = 7 marks) (c) An amplitude-modulated (AM) radio transmitter has a 15V carrier and a modulation index of 80%. (1) (ii) What is the modulating signal voltage? Determine the maximum and minimum voltages of the AM modulated wave. (3+5 = 8 marks) (d) An AM signal is generated by using a 2.5kW carrier with a modulation index of 90%. What is the total power of this AM signal? (5 marks) Total: (25 marks) Q.4 (a) An analogue-to-digital (A/D) converter produces 10 output bits for an analogue input voltage at each sampling point. (1) Determine the number of discrete levels that represent the input voltage, What is the signal-to-quantisation-noise ratio for this 10-bit converter? (ii) (2+3 - 5 marks) (b) The Manchester coding is used in a baseband transmission system. A data stream of 10001010001 is input to the Manchester line-code encoder, and the data rate is 40 Mbit/s. (1) Sketch the waveform of the Manchester-coded signal, What is the symbol rate of the coded signal? Briefly describe the main advantages and disadvantage of the Manchester coding scheme. (iii) (4+2+5 = 11 marks) (c) In a quadriphase-shift keying (QPSK) system, the carrier is transmitted with one of four possible phase values corresponding to a unique pair of binary bits during each signaling interval T, as shown in the following Table 1. The original data signal has a bit rate of 20 Mbit/s. Table 1 Binary Bits Phase 00 0 01 1/2 10 11 31/2 (i) What is the symbol rate of the resulting QPSK signal? (11) Determine the value of I for the QPSK signal: (iii) Draw the QPSK constellation diagram