1. Information Transmission
Course: CIS 3003
Fundamental of
Information Technology

2. This ppt file covers material in Chapter 8 – 10.

3. Objective
How binary streams are physically generated and transmitted with modulation.
Transmission concept including attenuation, bandwidth, channel capacity, and multiplexing
Properties of various transmission media.
Sources of transmission errors. Error detection and correction techniques.

4. Transmission and Electron
Metallic conductor material has loose electron
Copper is a metallic conductors.

5. Ohm’s Law
When a voltage/potential difference from an electrical source, such as a battery, is introduced between the two ends of a conductor, the electrons are stimulated to move within the metal from one atom to another
The relationship between voltage (V), current (I), and resistance (R) is defined by Ohm’s Law: V = IR

6. Transmission over conductors
Analog Binary

7. Transmission rate of M-ary signaling
Transmission rate of a m-ary signaling
D: data rate, R: signals per sec.
Calculate the data rate for a communication system using 8-ary signaling at rate of 1000 signals per second.

8. Transmission over air/vacuum
Electromagnetic (EM) energy
EM waves include radio waves, light waves (infrared, visible, ultraviolet), x-ray, gamma rays. Only radio waves and light wave used in communication
Modulation: varying wave properties to carry information.

9. Transmission over air/vacuum
Electromagnetic (EM) energy
EM waves include radio waves, light waves (infrared, visible, ultraviolet), x-ray, gamma rays. Only radio waves and light wave used in communication.

10. Radio Spectrum
The Federal Communications Commission (FCC) allocates radio frequencies in the United States, and most countries have a corresponding organization that assigns frequencies
Cordless telephones, walkie-talkies, and wireless network adapters are examples of other systems that have designated sets of operating frequencies but do not require permission for channel use

11. EM Wave Characteristics
EM wave is sinusoidal wave
Described by frequency, wavelength (in meters).
λ=c/f where λ is wavelength, c speed of light, and f is frequency.

12. Wavelength of a wave
Calculate the wavelength of a radio wave with 2.5 GHz frequency travelling thru a vacuum.

13. Modulation
Modulation: carry information through changing the properties of a wave.
Amplitude, phase, frequency.
Demodulation: extract information from a modulated wave.

14. Amplitude Modulation
AM radio

15. Frequency Modulation
FM radio

16. Phase Modulation Same frequency as carrier wave.
Shift in phase from carrier wave.
May appear similar to frequency modulation but is not interchangeable; use phase demodulator to interpret a frequency modulated signal creates data error.

17. Amplitude Shift Keying

18. Frequency Shift Keying

19. Phase Shift Keying

20. Exam 1 Held next Wednesday 9/28/2011 in class.
Material in Chapters 1 – 5.
No calculator nor computer. Closed books and notes.
True/False, Multiple Choice, Computation problems.
A problem can involve material from multiple chapters.

21. Multiplexing
Single line transmits multiple information carrying signals. Single copper carries 24 separate voice streams.
TDM, FDM, Statistical multiplexing, wavelength division multiplexing.
MUX and
DEMUX

22. Time Division Multiplexing

23. Attenuation Signals weaken as it travels through medium.
Repeaters amplify signal.

24. Cables
Twisted cable reduces interference but increases the attenuation or weakening of signal.

25. Error in Data Transmission
Error can be caused by attenuation, interference, thermal noise, etc.
Erroneous data can either be resent by the sender or corrected by the receiver.

26. Parity bit Parity bit is added to data for error detection.
Even parity: number of 1’s in the data and parity bit is an even number.
Odd parity: number of 1’s in the data and parity bit is an odd number.
Data:
Even parity: there are 4 1’s
Odd parity: there are 5 1’s

27. Single Parity Checking
Odd parity check: Transmitted Received There are 5 1’s There are 4 1’s; error Receiver detects error but cannot tell where is the error; the data needs to be resent.

28. Limitation in Single Parity Checking
Odd parity check: Transmitted Received There are 5 1’s There are 5 1’s; Receiver does not detect the error and assume the data is received correctly.

29. Rectangular Coding Given two 7-bit data: 1100000 1000101
Represent the data in a block form
Add parity bit to each data or row of the block
Add a parity bit to each column
Transmitted:

30. Correction w/ Rectangular Coding
Transmitted with even parity coding Received: Receiver can locate and correct error.

31. Data Transmission with Light

32. Data Transmission with Light
Visible light over fiber optical cable used for computer network communication.
Infrared used by TV remote controls to communicated with TV.

33. Fiber Optic Cable Refractive index: Speed of light thru vacuum
Speed of light thru a medium

34. Critical Angle Light travels inside Medium 1
Light hits at an angle greater than critical angle reflects.
Total internal reflection.
Critical angle depends on the refractive indices of both mediums.
Medium 1 has a higher RI than Medium 2 to keep light trapped in Medium 1

35. Reflection
Allow fiber optic cable to be bent to a certain degree and routed along structure as needed.

36. Types of Fiber Optic Cables
Single mode
single frequency light such as laser.
Core: 8 –10 µm. Cladding: 125 µm.
14 Tbit/s in a single 160 km (100 miles) line
Transcontinental network.
Uses laser as light source.
Multimode
Core: ’s µm.
10 Mbit/s to 10 Gbit/s over link lengths of up to 600 meters
Used as backbone network in building
Uses low cost LED as light source.
µm: Micrometer or micron equals to 0.001mm or 10^6 meters.

37. Fiber-optic Communication
Light emitting diodes (LED)/laser as transducer.
Lowest attenuation at 1.3 and 1.55 µm.
Coupler connects light source and detector with fiber cable.
Repeaters strength signal.
1.3 and 1.55 µm

38. Wavelength Division Multiplexing (WDM)
Two or more light source, each emits a different wavelength.
10 (coarse) or 100 (dense) channels in one fiber. Mostly used with single mode cable.

39. Compare Optic to Copper
Higher transmission rate.
Lower attenuation
Immune to. electromagnetic interference.
Harder to eavesdrop.
Harder to splicing (joining two cables).
Light weight.
Low power consumption.
Harder to install – fiber optic is delicate and can be damaged by pulling and twisting.

40. Applications of Fiber Optics
Internet backbone; Transcontinental connections.
Research on replace wire with fiber optic on chips to overcome noise and attenuation.
Fiber to connect ISP network to consumers.
Fiber optic provides lights and transmit information in endoscope.

44. Wireless Data Transmission

45. Summary