Data Communication and Networking- chapter 2-Information Encoding
- 1. Data Communications and Networks R.Anushiya Assstiant Professor, P.K.R Arts College for Women, Gobi 1 Information Encoding Author: Achyut S.Godbole, “ Data Communications and Networks”, Tata McGraw-Hill Publishing Company Limited, Ninth reprint, 2007
- 2. • Data Communication • Potocols • Standard Organizations • Signal Popagation • Analog and Digital Signals • Bandwidth 2
- 3. Signal Propagation • Core of data communication is the concept of Signal propagation A B X Steel rod V T R P U S Q A B X 3
- 4. Signal Propagation • When we apply heat at one end of rod (A), initially heat felt and end of A. • After sometime we would feel heat at X point and slowly next at B point finally • This is where the principal of energy transferred, because of heat raise in temperature, atoms at A end start oscillating. • Then after some time point X start oscillating, here the kinetic energy is converted to heat energy 4
- 5. Signal propagation • Now if we put the rod in an ice box, the reverse process will be done after some time (rod gets cool at A,X then to B) • The finite time is called propagation delay V T R P U S Q time temperature V T R P U S Q time temperature 5
- 6. • Instead atoms the electrons transfer electrical energy to the adjacent electrons • Therefore the process signifies that if we apply some kind of signal (heat, voltage or current, etc) at one end of conducting material such as rod or a wire, this signal is propagated to the other end of the material 6
- 7. Analog Signal • Analog is a continuous varying signal (waveform) • It is smooth and continuous in nature 7
- 8. Digital Signal • Digital signal takes of pulse (i.e., 0 and 1) • It represents a sudden jump from one value to another 8
- 9. Bandwidth of a signal Eg: Pipe at home The maximum capacity of the pipe at a given instance is bandwidth In case of data transmission, the amount of data transmitted through the wire is to be measured 9
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- 11. Sinusoidal Signal • Signal simply means the value of any quantity taken over a period of time. • Signals are usually time varying in nature. • Generally a graph is plotted between values at different time instants. This is called graphical representation of signal. 11
- 12. • When Sine wave starts from zero and covers positive values, reaches zero; and again covers negative values, reaches zero, it is said to have completed one cycle or single cycle. • The upper part of sine wave is called positive cycle and the lower part is called negative cycle in a single cycle. 0 + value - value 12
- 13. • For different values of time, the Signal gives the values of quantity at that time. • Therefore Signal is a function of time. • It is therefore written as f(t). The Maximum value of the Sinusoidal Signal is also called its amplitude (A). • Amplitude is measured in volts- voltage amperes-current watts - power 13
- 14. Frequency • The number of cycles of signal that took place in a second. • Frequency is measured in Hertz (Hz). Period • The time taken for the completion of one cycle. 14
- 16. • Encoding is the process of converting the data or a given sequence of characters, symbols, alphabets etc., into a specified format, for the secured transmission of data. • Decoding is the reverse process of encoding which is to extract the information from the converted format. 16
- 17. Data Encoding Encoding is the process of using various patterns of voltage or current levels to represent 1s and 0s of the digital signals on the transmission link. 17
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- 22. 22 EBCDIC
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- 25. Definition - What does Extended Binary Coded Decimal Interchange Code (EBCDIC) mean? Extended binary coded decimal interchange code (EBCDIC) is an 8-bit binary code for numeric and alphanumeric characters. It was developed and used by IBM. It is a coding representation in which symbols, letters and numbers are presented in binary language. 25
- 26. Multimedia The Combinations of multiple media (Text, Image, Audio, video, Graphics, etc.,) 26
- 27. Pictures • A Number of horizontal and vertical lines to form a grid • Each rectangle is called a pixel • As a number of pixel increases, the pixel size decreases 27
- 28. Picture • Scanner throws light on the pixel, the reflection of light from the pixel vary. • This generates electrical signals for black and white as bits 0 & 1 • This means 1->black, 0->white or vise versa 28
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- 30. Video 30
- 31. Video • Group of pictures shown rapidly can be viewed as a video • 24 pictures are shown in one second 31
- 32. Sound • Sound refers to waveforms traveling through a fluid medium such as air • Sound is a mechanical wave and therefore requires a medium in which it can travel. S • Sound travels at 1130 feet per second at normal room temperature • Sound is measured in dB (decibel) 32
- 34. Sound Waves 34
- 35. Analogue audio The name for an electronic signal that carries its information of sound as continuous fluctuating voltage value. Digitizing The process of converting an analog signal to a digital one. A sound is recorded by making a measurement of the amplitude of the sound at regular intervals which are defined by the "sample rate". The act of taking the measurement is often called "sampling" and each measurement is called a "sample point". 35
- 36. Sampling 36