1. Telecommunications & NetworksBy
Umamaheswari.T

2. Communication Model Message is communicated via a signal
Transmission medium (communication channel) “carries” the signal
Feedback
Encode
Decode

3. Telecommunications
Electronic transmission of signals, e.g., telephone, radio, television
Telecommunication medium: Anything that carries an electronic signal & interfaces between a sending device & a receiving device
Data Communications: A subset of telecommunications referring to the sending, transmission, & receiving of data -- typically between computer systems

4. Communications & Telecommunications
In human speech, signals are transmitted through the air; in telecommunications, signals are transmitted through various media

5. Telecommunications Applications (1)
Linking computers & data terminals: Download & upload information
Voice Mail: Enables users to send, receive, & save verbal messages, including sending the same message to a “group”
Enables users to send, receive, & save text messages & attached documents
Telecommuting: Enables employees to work away from the office using PCs & networks to communicate electronically

6. Types of telecommunication Media (1)
Twisted Pair
Insulated copper wire
Electrical signals
Coaxial Cable
Inner wire core surrounded by shielding
Higher transmission speeds than twisted pair
Fiber-optic Cable
Extremely thin strands of glass bound together
Light pulse signals
Very high transmission speeds

7. Types of Telecommunication Media (2)
Microwave
Satellite

8. Types of Telecommunication Media (3)
Cellular transmission signals are transmitted to receivers & integrated into the regular network.
Chapter 6
IS for management

9. Open Wire Transmission Systems

10. Paired Cable Transmission Systems

11. Attenuation Vs Frequency

12. Two Wire Transmission Systems
Fig 1.15 shows the single wire transmission used in the past was too noisy for customer acceptance.
Fig 1.16 used with signals propagating as a voltage difference between two wires.
METALLIC CURRENT The electrical current produced by the difference signal flowing through the wires in opposite direction.
LONGITUDENAL or COMMON-MODE CURRENT Current propagating in same direction in both wires

13. Two Wire to Four Wire Conversion
Two-Wire : One path for both directions
Old analog end offices were used a two-wire transmission system
Four-Wire: Two separate paths for two directions
Interoffice trunks typically use four-wire transmission system
Derived Four-Wire: Separating the B.W. of single pair into two sub bands

14. Loaded Coil
The usual method to reduce amplitude distortion on intermediate length pairs is to insert an artificial inductance into the lines
That
can be done by loaded coils.

15. Frequency Division Multiplexing

16. A5 Channel Bank Multiplexer

17. LMX Group Bank Multiplexer

18. Time Division Multiplexing

19. T-Carrier Systems The functions of regenerative repeaters
1. Equalization
2. Clock Recovery
3. Pulse Detection
4. Transmission

20. REGENERATIVE REPEATER

21. TDM Hierarchy

22. TDM Hierarchy E1 30 VC –-2.048 E5 30-2.048 E4 1920-M34-8.448

23. Digital Pair Gain Systems --- Subscriber loop carrier

24. Subscriber loop multiplexer
Chapter 6

25. Digital Transmission & Multiplexing
Selection of a finite set of discrete electrical waveform for encoding the information
Defines time relationships between the individual transmission signals
The timing information requires channel capacity in terms of B.W. , data rate ,code space.

26. Pulse Transmission

27. Inter Symbol Interference
Small perturbations in the channel response.
Main causes
1. Timing Inaccuracies
2. Insufficient B.W.
3. Amplitude Distortion
4. Phase Distortion

28. Line Coding Line coding considerations
Provides adequate timing information
Line coding considerations
Spectrum of the line code
Available B.W
Noise and interference levels
Performance monitoring
Synchronization acquisition times
Implementation Cost

29. Level Encoding
Level Encoding
UniPolar
Polar
BiPolar

30. Bipolar Coding
Solves the dc wander problem by using 3 levels to encode binary data
A logic “0” is encoded with 0V
A logic “1” is encoded with +ve & -ve voltages
The average level can be maintained at level ‘0’ to eliminate dc components in the spectrum.
Also called as Alternate Mark Inversion(AMI)

31. Code Space Redundancy
Detects the errors depending on the polarity of successive pulses
Same polarity Error
Alternate polarity No Error
The error is called bipolar violation
Inserts bipolar violations to signify TDM Marks, Alarm conditions or Special codes to increase timing information
Chapter 6
IS for management

32. Binary N-Zero Substitution
More number of 0’s in a code leads to timing jitter.
Replace all strings of N 0’s by a special N-length code
BNZS
B3ZS
B6ZS
B8ZS

33. BINARY 3-ZERO SUBSTITUTION:
Each string of 0’s encoded with either 00V or B0V

34. B6ZS

35. B8ZS

36. High Density Bipolar 3 code

37. Examples
B3ZS:
Chapter 6
IS for management

38. Digital Biphase Differential Encoding
Also called as Diphase or Manchester.
Maintains good timing information
No DC wander
Complete square wave
1->+ve &-ve ; 0-> opp. phase
Differential Encoding

39. Time Division Multiplexing
Synchronous
Asynchronous
Time Division Multiplexing
Assigned a time slot corresponding to a single bit
Bit Interleaving
Assigned a longer time slot corresponding to some larger no. of bits
Word Interleaving

40. Framing Added Digit Framing Frame synchronisation
Added Channel Framing
Unique line signal Framing
Statistical Framing

41. Added Channel Framing (DS1)

42. Added Channel Framing (E1)

43. TDM LOOPS & RINGS

44. SONET/SDH

45. SONET MULTIPLEXER

46. SONET Frame Formats
SONET Layers

47. STS-1 FRAME
Line Overhead
Path Overhead
Section Overhead

48. STS-3 Frame Format
Chapter 6
IS for management

49. SONET Overhead Layers

50. Payload Pointers
Chapter 6
IS for management

51. Virtual Tributaries
VT Types