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Afnan alfhuid
200800846
College of Computer Engineering and Sciences
ITAP 2431 – Network Management
Assignment # 2
Q1. How does analog data differ from digital data? Give two differences(2 Marks)
•
Analog data
– Produced by telephones
– Sound waves, which vary continuously over time, analogous to one’s voice
– Can take on any value in a wide range of possibilities
– Analog computers process measured data
•
Digital data
– Produced by computers, in binary form
– information is represented as code in a series of ones and zeros
– All digital data is either on or off, 0 or 1
– A digital computer process discrete data (digits)..
Q2. Is the bit rate the same as the symbol rate?(1 Mark)
Each symbol can represent or convey one or several bits of data.
Q3. What are three important characteristics of a sound wave? Show with a clear diagram and example.
(3 Marks)
Amplitude Modulation(AM)
for example .. Amplitude of the waveform for detailed editing,. Amplitude modulated by the sound.
The displacement amplitude at the resonance frequency with increasing applied voltage does not increase linearly.
.
Frequency Modulation (FM)
Foe example ... a buoy because it occur increase and decrees
Phase Modulation (PM)
For example The quantitative aspects of this cross-phase–modulation–induced modulation instability are
discussed and illustrated by use of a realistic experimental example
Q4. Describe three types of guided media.
(3 Marks)
Twisted Pair
The wires in Twisted Pair cabling are twisted together in pairs. Each pair would consist of a wire used for the
+ve data signal and a wire used for the -ve data signal. Any noise that appears on 1 wire of the pair would
occur on the other wire. Because the wires are opposite polarities, they are 180 degrees out of phase (180
degrees - phasor definition of opposite polarity). When the noise appears on both wires, it cancels or nulls itself
out at the receiving end. Twisted Pair cables are most effectively used in systems that use a balanced line
method of transmission: polar line coding (Manchester Encoding) as opposed to unipolar line coding (TTL
logic).
Coaxial Cable
Coaxial Cable consists of 2 conductors. The inner conductor is held inside an insulator with the other
conductor woven around it providing a shield. An insulating protective coating called a jacket covers the outer
conductor.
Optical Fibre
Optical Fibre consists of thin glass fibres that can carry information at frequencies in the visible light
spectrum and beyond. The typical optical fibre consists of a very narrow strand of glass called the Core.
Around the Core is a concentric layer of glass called the Cladding. A typical Core diameter is 62.5 microns (1
micron = 10-6 meters). Typically Cladding has a diameter of 125 microns. Coating the cladding is a
protective coating consisting of plastic, it is called the Jacket.
Q5. Describe three types of wireless media.
(3 Marks)
Broadcast Radio
distributes radio signals through the air over long distances such as between cities, regions and countries
and short distances such as within am office or home. Transfer rate = up to 54 Mbps
Microwaves
radio waves that provide a high- speed signal transmission. Earth-based reflective dish that contains
antenna, transceivers, and other equipment necessary for microwave communications.
Infrared
Wireless transmission media that sends signals using infrared light waves. Requires line-of-sight
transmission. Many computers and devices have an IrDA port that enables transfer of data using infrared
light rays. Transfer rate= 1 Mbps- 4 Mbps
Q6. 1/ How does forward error correction work? 2\How is it different from other error-correction methods?
1/FEC works by adding “check bits” to the outgoing data stream. Adding more check bits
reduces the amount of available bandwidth by increasing the overall block size of the outgoing data, but also
enables the receiver to correct for more errors without receiving any additional transmitted data. 2/ The
maximum fractions of errors or of missing bits that can be corrected is determined by the design of the FEC
code, so different forward error correcting codes are suitable for different conditions
(2 Marks)
Q7. Which is better, controlled access or contention? Explain clearly your answer
The contention approaches work better, because it has Network with high traffic.
(1 Mark)
Q8. What does the data link layer do? Explain at least its three functions.
(3 Marks)
Error checking - all circuits have errors occasionally.
Flow regulation - Line has finite data rate, and machines have finite rate at which they can process
incoming. Regulate flow so that slow receivers are not swamped by fast senders.
1)
Media Access Control:
Important when more than one computer wants to send data at the same time over the same, shared circuit.
2) Error Control:
Error detection techniques allow detecting such errors, while error correction enables reconstruction of the
original data.
3) Message Delineation:
Identifying the beginning and end of a message
Q9. What is transmission efficiency? Explain with the formula for TRIB.
The transmission of data from one computer to the other with minimum or no errors.
TRIB = K (M – C) (1 – P)
(M / R) + T
K= Info bits per character
M= Packet length in characters
C= Average number of non-info characters per block
P= Probability that a block will require retransmission
R= Data xmission rate in char per second
(2 Marks)
T = Time between blocks (in seconds) (propagation time + turnaround time) (a.k.a., reclocking time)
So,
The TRIB= Number of info bits accepted / total time required to get the bits
(number of info bits) (Prob. Of successful xmission)
time it takes to transmit these bits + propagation delay