(Chapter 11) Digital T-carriers and Multiplexing (71-77)

BOOK REVIEW IN COMMUNICATIONS

CHAPTER 11 #

Electronic Communications System By Wayne Tomasi

DIGITAL T-CARRIERS AND MULTIPLEXING DEFINITIONS

1)

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

2)

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

3)

Considered as transmission medium.

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.

5)

Modulates a sine wave carrier.

6)

Modulates a cosine wave carrier.

TERMS

Multiplexing

Space-Division Multiplexing

Trench

QPSK

I – Channel Bits

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.

Prepared By : MA. ELAINE L. CORTEZ

PCM

71



10)

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

11)

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

DS-O Channel

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.

17)

Special conditioned cables.

18)

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

19)

PCM encoders & decoders with a seven-bit magnitude.

20)

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

21)

Only seven-bit resolution.

22)

Consist of 24 193 bit frames, totaling 4632 bits, of Prepared By : MA. ELAINE L. CORTEZ

300 Hz to 3000 Hz

TI Lines

Framing Bit

Digital Channel Banks

Signaling

Signaling Frame Extended Super Frame Format 72



which 24 are framing bits. CRC-6 ( Cyclic Redundancy Checking )

23)

Used for an error detection code.

24)

Signaling bit in frame 6.

A Bit

25)


B Bit

26)


C Bit

27)


D Bit

28)

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

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.

32)

Low quality video transmission for use between nondedicated subscribers.

33)

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

34)

First bit of the code. Prepared By : MA. ELAINE L. CORTEZ

Data Service Unit / Channel Service Unit

Signal Processor

Picturephone

Three-Bit Code

Address Bit 73



35)

Converting standard logic levels.

36)

Involves the transmission of only a single nonzero voltage level.

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).

38)

Categorize the type of transmission.

39)

Maintained the entire bit time.

Nonreturn 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 & o’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


Digital Line Encoding

Unipolar

Bipolar

Duty Cycle

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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.

47)

Used for the transmission of PCM-encoded timedivision 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.

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.

51)

Different version of T carriers used in Europe.

52)

Used for frame alignment pattern and for an alarm channel.

53)

54)

Digital carrier frame synchronization.

Methods of Interleaving PCM transmissions:


Miller Codes

Timing Clock

Regenerative Repeater

E-Lines

Time Slot 0

Added-Digit Framing Robbed-digit framing Added-channel framing Statistical framing Unique-line code framing

Bit Interleaving Word Interleaving

75



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.

64)

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

65)

Basic building block of the FDM Heirarchy. Prepared By : MA. ELAINE L. CORTEZ

Stacking

Short Haul; Long Haul Message Channel 76



66)

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

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.


Demultiplexers / Splitters

OC-48

77

(Chapter 11) Digital T-carriers and Multiplexing (71-77)

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