Chapter 11: Digital T-Carriers and Multiplexing - Review Notes

Reviewer and summary notes of the important concepts and formulas in Chapter 11 of the book "Introduction to Electronics Communications" by Wayne Tomasi.

Chapter 11: Digital T-Carriers and Multiplexing

This is the summary notes of the important terms and concepts in Chapter 11 of the book "Electronic Communications System" by Wayne Tomasi. The notes are properly synchronized and concise for much better understanding of the book. Make sure to familiarize this review notes to increase the chance of passing the ECE Board Exam.

CHAPTER 11

DIGITAL T-CARRIERS AND MULTIPLEXING

Items

Definitions

Terms

1

Transmission of information from one or more source To one or more destination over the same transmission medium (facility).

Multiplexing

2

Unsophisticated form of multiplexing that simply constitutes propagating signals from different sources of different cables that are contained within the same trench.

Space-Division

Multiplexing

3

Considered as transmission medium.

Trench

4

Form of phase-division multiplexing (PDM) where to date channels (the I and Q) modulate the same carrier frequency that has been shifted 90◦ in phase.

QPSK

5

Modulates a sine wave carrier.

I – Channel Bits

6

Modulates a cosine wave carrier.

Q – Channel Bits

7

Three most predominant methods of multiplexing signals.

Time-Division Multiplexing; Frequency-Division Multiplexing; Wavelength-Division Multiplexing

8

Transmissions from multiple sources occur on the same but not on the same time.

Time-Division Multiplexing

9

Most prevalent encoding technique used for TDM digital signals.

PCM

10

Use an 8-kHz sample rate and an eight-bit PCM code, which produces a 64 kbps PCM line speed.

DS-O Channel

11

Simply an electronically controlled digital switch with two inputs and one outputs.

Multiplexer

12

One eight-bit PCM code from each channel (16 total bits).

TDM Frame

13

Time it takes to transmit one TDM frame.

Frame Time

14

A communications system that uses digital pulses rather than analog signals to encode information.

Digital Carrier System

15

Specifies a digital carrier system using PCM encoded analog signals.

TI or Transmission One

16

Voice band channel bandwidth.

300 Hz to 3000 Hz

17

Special conditioned cables.

TI Lines

18

Used to maintain frame and sample synchronization between TDM transmitter & receiver.

Framing Bit

19

PCM encoders & decoders with a seven-bit magnitude.

Digital Channel Banks

20

Supervision between telephone offices, such as on hook, off hook, dial pulsing, and so forth.

Signaling

21

Only seven-bit resolution.

Signaling Frame

22

Consist of 24 193 bit frames, totaling 4632 bits, of which 24 are framing bits.

Extended Super Frame

Format

23

Used for an error detection code.

CRC-6 ( Cyclic Redundancy Checking )

24

Signaling bit in frame 6.

A Bit

25

Signaling bit in frame 12.

B Bit

26

Signaling bit in frame 18.

C Bit

27

Signaling bit in frame 24.

D Bit

28

Digital interface that provides the physical connection to a digital carrier network.

Data Service Unit / Channel Service Unit

29

Upgrade from one level in the hierarchy to the next higher level.

Multiplexers / Demultiplexers

30

Provides a convenient place to make patchable inter connects and perform routine maintenance & trouble shooting.

Digital Cross Connect

31

Provides frequency shifting for the master group signals.

Signal Processor

32

Low quality video transmission for use between non-dedicated subscribers.

Picturephone

33

Identify when transitions occur in the data and whether that transition is from a 1 to a 0 or vice versa.

Three-Bit Code

34

First bit of the code.

Address Bit

35

Converting standard logic levels.

Digital Line Encoding

36

Involves the transmission of only a single nonzero voltage level.

Unipolar

37

Two nonzero voltages are involved ( a positive voltage for a logic 1 and an equal-magnitude negative voltage for a logic 0 or vice versa).

Bipolar

38

Categorize the type of transmission.

Duty Cycle

39

Maintained the entire bit time.

Non-return to Zero

40

Less than 100% of the bit time.

Return to Zero

41

Produces a condition in which a receive may lose its amplitude reference for optimum discrimination between received 1’s & 0’s.

DC Wandering

42

Popular type of line encoding that produces a strong timing component for clock recovery and does not cause dc wandering.

Digital Biphase

43

Uses one cycle of a square wave at 0◦ phase to represent a logic 1 and one cycle of a square wave at 180◦ phase to represent a logic 0.

Biphase

44

Used for encoding SMPTE(Society of Motion Picture and Tele vision Engineers) time-code data for recording on videotapes.

Biphase M

45

Commonly called the Manchester Code and specified in IEEE standard 802.3 for Ethernet local area networks.

Biphase L

46

Forms of delay-modulated codes where a logic 1 condition produces a transition in the middle of the clock pulse, and a logic 0 produces no transition at the end of the clock intervals unless followed by another logic 0.

Miller Codes

47

Used for the transmission of PCM-encoded time-division multiplexed digital signals.

T Carriers

48

Filters and shapes the incoming digital signal and raise its power level so that the regenerator circuit can make a pulse-no pulse decision.

Amplifier /

Equalizer

49

Recovery circuit reproduces the cocking information from the received data and provides the proper timing information to the regenerator so that samples can be made at the optimum time, minimizing the chance of an error occurring.

Timing Clock

50

A threshold detector that compares the sampled voltage received to a reference level and determines whether the bit is a logic 1 or a logic 0.

Regenerative Repeater

51

Different version of T carriers used in Europe.

E-Lines

52

Used for frame alignment pattern and for an alarm channel.

Time Slot 0

53

Digital carrier frame synchronization.

Added-Digit Framing

Robbed-digit framing

Added-channel framing

Statistical framing

Unique-line code framing

54

Methods of Interleaving PCM transmissions:

Bit Interleaving

Word Interleaving

55

Used more often for the transmission of data when they are called asynchronous TDM, intelligent TDM, or simply stat muxs.

Statistical Time-Division

Multiplexing

56

Large-scale integration (LSI) chip designed for use in the telecommunications industry for private branch exchanges.

CODEC

57

Three functions of codec.

Analog Sampling;

Encoding / Decoding;

Digital Companding

58

Used to gate the PCM word onto the PCM highway when an external buffer is used to drive the line.

Time Slot Strobe Buffer

59

Data are input and output for a single channel in a short burst.

Burst Mode

60

Allows for a flexible data input and output clock frequency.

Variable-Data-Rate

Mode

61

Data from the PCM highway are clock into the codec on the next eight consecutive negative transitions of DCLKR.

Shift Register Mode

62

Multiple sources that originally occupied the same frequency spectrum are each converted to a different frequency.

Frequency Division

Multiplexing

63

Process is accomplished without synchronization between stations.

Stacking

64

AT&T’s communications network is subdivided into 2:

Short Haul;

Long Haul

65

Basic building block of the FDM Hierarchy.

Message Channel

66

Separate signals with different wavelengths in a manner similar to the way filters separate electrical signals of different frequencies.

Demultiplexers /

Splitters

67

Similar to regular multiplexers and demultiplexers except they are located at intermediate points in the system.

Add / Drop Multiplexers / Demultiplexers

68

Direct signals of a particular wavelength to a specific destination while not separating all the wavelengths present on the cable.

WDM Routers

69

Enable more efficient utilization of the transmission capabilities of optical fibers by permitting different wavelengths to be combined and separated.

WDM Couplers

70

Three basic types of WDM couplers:

Diffraction Grating ; Prism ; Dichroic Filter

71

Multiplexing system similar to conventional time division multiplexing.

Synchronous Optical Network

72

Has a 51.84-Mbps synchronous frame structure.

STS-1

73

Second level of SONET multiplexing.

OC-48

Complete List of Reviewers in Electronic Communications System per Chapter

Important List of Communications Engineering Materials


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