Briefly describe the layers of OSI model.

Match the following to one or more layers of the OSI model:
a. Communicates directly with user's application program
b. Error correction and retransmission
c. Mechanical, electrical, and functional interface
d. Responsibility for carrying frames between adjacent nodes

Define Noise. We have a channel with 4 KHz bandwidth. If we want to send data at 100 Kbps, What is the minimum SNR_dB?

Consider a noiseless channel with a bandwidth of 3000 Hz transmitting a signal with two signal levels. Calculated the maximum bit rate.

What are main causes of transmission impairment? Explain with proper diagram.

What is a composite periodic signal? A periodic composite signal with a bandwidth of 3000Hz is composed of two sine waves. The first one has a frequency of 100 Hz with a maximum amplitude of 30V. The second one has a maximum amplitude of 10V. Draw the Bandwidth.

Draw the graph of the NRZ-L scheme using each of the following data streams, assuming that the last signal level has been positive. From the graphs, guess the bandwidth for this scheme using the average number of changes in the signal level.
a. 00000000
b. 11111111
c. 01010101
d. 00110011

Listed advantages and disadvantages of Delta Modulation and Pulse Code Modulation

Write down basic properties of the following line coding schemes with proper signal schem?
i. Manchester
ii. MLT-3
iii. 2B1Q

Which of the four digital-to-analog conversion techniques (ASK, FSK, PSK or QAM) is the most susceptible to noise? Defend your answer.

Draw the constellation diagram for the following cases. Find the peak amplitude value for each case and define the type of modulation (ASK, FSK, PSK, or QAM). The numbers in parentheses define the values of I and Q respectively.

a. Two points at (2, 0) and (3, 0).
b. Two points at (3, 0) and (-3, 0).
c. Four points at (2, 2), (-2, 2), (-2, -2), and (2, -2).
d. Two points at (0, 2) and (0, -2)

Briefly explain any analog to analog conversion technique including advantages, disadvantages and real application scenarios.

What are the two components of a signal when the signal is represented on a constellation diagram? Which component is shown on the horizontal axis? Which is shown on the vertical axis?

Differences between Synchronous TDM and statistical TDM.

What is multiplexing? Why is it need mentioning real application scenarios?

Define spread spectrum and its goal. List the two spread spectrum techniques.

Briefly describe the multiplexing and de-multiplexing technique of FDM.

What is the Hamming distance for each of the following code words:

a. d (10000, 00000)

b. d (10101, 10000)

c. d (11111,11111)

d. d (000, 000)

Apply the following operations on the corresponding polynomials:

a. (x3+x1+X+1)+(x4+x1+x+1)
b. (x3+x1+x+1)-(x4+x1+x+1)
c. (x3 + x1) X (x4+x2+x+1)
d. (x3+x2+x+1)/(x2+1)

Why Switching is needed? Make comparative analysis among circuit switched, packet switched and message switched networks.

What is DHCP? Briefly explain the basic operation of DHCP

What are basic properties of 1G, 2G, 3G, 4G.

What is NAT? How NAT works? Describe briefly.

Suppose a file of 12800 characters is to be sent over a line at 3600bps.

i. Calculate the overhead in bits and time in asynchronous communication. Assume one start bit, one stop bit, and 8-bits to send the byte itself for each character. Given that the 8-bit character consists of all data bits with no parity bit.

ii. Calculate the overhead in bits and time in synchronous communication. Assume that the data are sent in frames. Each frame consists of 400 characters and an overhead of 36 control bits per frame.

Describe Cellular Telephony system with suitable architecture.

In synchronous TDM, there are three data inputs where the data rate for each connection is 1 Kbps. If 1 bit at a time is multiplexed, what is the

i. Duration of each input slot
ii. Duration of each output slot
iii. Duration of each frame
iv. Output bit rate.