This is the series of network fundamental course for IT learners. The student should follow the course from the first lecture...............................

1. CSC339 – NETWORK
FUNDAMENTAL
Jahan University
Computer Science Department
Lecturer: Islahuddin Jalal
Master in Cyber Security
10/16/2015Jahan University 1

2. Class Policy
 A student must reach the class-room in time. Late comers may join the class
but are not entitled to be marked present.
 Attendance shall be marked at the start of the class and students failing to
secure 75% attendance will not be allowed to sit in final exam.
 The assignment submission deadline must be observed. In case of late
submission, ten percent may be deducted from each day.
 Those who are absent on the announcement date of the assignment/test.
Must get the topic/chapter of test/assignment confirmed through their peers.
 Mobile phones must be switched-off in the class-rooms.
10/16/2015Jahan University 2

3. Grading Evaluation for Network fundamental
Internal Evaluation
Midterm Exam 20%
Attendance 5%
Assignment/Presentations 5%
Quizzes/Tests 10%
Total Internal Evaluation 40%
Final-term Examination
Final-term Exam 60%
Total Marks 100%
10/16/2015Jahan University 3

4. Topics to be discussed
 Baseband transmission
 Broadband transmission
 Modes of channel operation
 Attenuation
10/16/2015Jahan University 4

5. Digital signal vs Analog signal
 Signals can be analog or digital
 Analog signals can have an infinite number of values in a range.
 Digital signals can have only a limited
10/16/2015Jahan University 5

6. Baseband Transmission
 Baseband transmission
 Digital signals are used
 Time Division Multiplexing is possible
 Baseband is bi-directional transmission
 Short distance signal travelling
 Entire bandwidth of the cable is consumed by a single signal in a baseband
transmission.
 Using dedicated medium
10/16/2015Jahan University 6

7. Baseband transmission
 In baseband transmission, the required bandwidth is proportional to the bit
rate; if we need to send bits faster, we need more bandwidth.
 Baseband transmission of a digital signal that preserves the shape of the
digital signal is possible only if we have a low pass channel with an infinite or
very wide bandwidth.
10/16/2015Jahan University 7

8. Baseband transmission

9. Example of Baseband transmission
 LAN uses a dedicated channel for two stations communicating with each
other.
 In a bus topology LAN with multipoint connections, only two stations can
communicate with each other at each moment in time, the other stations need to
avoid from sending data.
 In a star topology LAN, the entire channel between each station and the hub is
used for communication between these two entities.
 Etc.
10/16/2015Jahan University 9

10. Broadband transmission
 Broadband:
 Analog signals are used
 Transmission of data is unidirectional
 Signal travelling distance is long
 Frequency division multiplexing is possible
 The signals are sent on multiple frequencies and allow all the multiple signals are
sent simultaneously in broadband transmission.
 Modulator is used
10/16/2015Jahan University 10

11. Modulation of a digital signal for transmission on a bandpass
channel

12. Example of Broadband Transmission
 Sending computer data over a telephone line
 Digital Cellular telephone.
 The digital cellular phones convert the analog audio signal to digital and then
convert it again to analog for transmission over a bandpass channel.
10/16/2015Jahan University 12

13. Attenuation
 Loss of energy
 When a signal travels through a medium, it loses some of its energy due to the
resistance of the medium.
 Some wire or medium carrying electric signals get warm after some time it is
converted into heat
10/16/2015Jahan University 13

14. Attenuation

15. Data Transmission Rates
 How fast we can send data
 Bit per second over a channel
10/16/2015Jahan University 15

16. Data Transmission rate
 Depends of three factors
 The bandwidth available
 The level of the signals
 The quality of the channel (the level of noise)
10/16/2015Jahan University 16

17. Theoretical formulas for data rate
 There are two formulas for calculating data rate
 Noiseless Channel formula by Nyquist
 BitRate = 2 * bandwidth * log2L
 Noisy Channel formula by Shannon
 Capacity = bandwidth * log2 (1+SNR)
 SNR = signal to noise ratio = average signal power
average noise power
10/16/2015Jahan University 17

18. Example of Noiseless channel formula
 Consider a noiseless channel with a bandwidth of 3000Hz transmitting a signal
with two signal levels. The maximum bit rate can be calculated as:
 BitRate = 2 * 3000 * Log22
= 6000 * Log22
= 6000 * 1
= 6000 bps
10/16/2015Jahan University 18

19. Example of noisy channel formula
 We can calculate the theoretical highest bit rate of a regular telephone line.
A telephone line normally has a bandwidth of 3000 Hz (300 to 3300) assigned
for data communications. The signal-to-noise ration is usually 3162. for this
channel the capacity is calculated as:
 C= B log2 (1+SNR)
= 3000 log2 (1+3162)
=3000 log2 (3163)
=3000 * 11.62
=34860bps
10/16/2015Jahan University 19

20. Modes of Channel Operation
10/16/2015Jahan University 20
 Three types of modes of Channel Operation
 Simplex
 Half duplex
 Full duplex

21. Simplex
 Data in a simplex channel is always one way. Simplex channels are not often
used because it is not possible to send back error or control signals to the
transmit end.
 E.g Television, radio transmission
10/16/2015Jahan University 21

22. Half duplex
 A half-duplex channel can send and receive, but not at the same time.
 E.g one-lane bridge, walkie-talkie
 In some aspects, you can think of Internet surfing as being half-duplex, as a
user issues a request for a web document, then that document is downloaded
and displayed before the user issues another request
 In addition, it is possible to perform error detection and request the sender
to retransmit information that arrived corrupted.
10/16/2015Jahan University 22

23. Half Duplex
10/16/2015Jahan University 23

24. Full duplex
 Data can travel in both directions simultaneously.
 There is no need to switch from transmit to receive mode like in half duplex.
 Its like a two lane bridge on a two-lane highway.
 E.g Mobile
10/16/2015Jahan University 24

25. END
Thanks for
hearing…………………….