DTS Migration to Digital Microwave Digital Fundamentals Testing Applications Making the Change.

DTS

Migration to Digital Microwave

Digital Fundamentals

Testing Applications

Making the Change

DTS Dover Telecommunication Services, Inc. © 2002 All rights reserved

Seminar Objectives

• Review Digital Microwave Parameters• Digital Overview• Digital Test Equipment Overview• DSX Panels and Standards• Digital Test Patterns• Digital Errors and Alarms• Digital Loopback


Single VF Channel

3825 HZOut-of-Band Signaling Tone

E & M (-20 dBmØ)

Usable VoiceBandwidth3.1 K Flat


Baseband Elements

• The Analog Basebands consist of – Baseband amplifiers– Baseband bridges– Roofing filters– Group converters– Pilot stop filters– Orderwire and Service Channels– Alarm and control devices


Analog and Digital SignalProcessing

• An analog baseband is the composite of all – Voice and HF tones– Noise in each channel– Cumulative system noise

• Analog means Amplify


Digital Interfaces

• T1 – DS3 Interface– Interconnection into a digital radio– Conform to ANSI standards– Use Standard DSX Panels

• Layout

• Wiring protocol

• Making a cross-connect


North American Digital Hierarchy

DS0 4KHz – 1DS0 64Kb/s

DS1 24 – DS0 1.544Mb/s

DS3

(STS 1)

672 – DS0 45.736Mb/s

(51.840Mb/s)

OC3 - Optical

(STS 3) – Elec.

2016 – DS0 155.220Mb/s

OC12 8064 – DS0 622.08Mb/s

OC 48 32,256 – DS0 2488.32Mb/s

OC192 129,024 – DS0 9953.28Mb/s


RF Carriers

• Radio Frequencies (RF) are defined as:– Periodic waves capable of traveling thru space.– Waveforms that meet the conditions of

Maxwell’s Equations.– Always periodic electro-magnetic wave fronts.– Always consist of three core elements . . .


Modulation

• RF carriers exist as CW with no external modulation – variation.

• To Modulate is to vary, such as:– Change Amplitude –AM– Change Frequency – FM– Change Phase – Ø


CW Wave

TEK492PGM

REFLEVEL 0 DBM

FREQUENCY6.535 GHzCEN DBM

SPAN/DIV 10 MHz

10 DB/VERTICALDISPLAY

30 DBRF

ATTENUATION

3.0 — 7.1FREQ

RANGE

INT 1 MHzRESOLUTIONBANDWIDTH

0

-10

-20

-30

-40

-50

-60

-70

-80


FM Modulation

• When a carrier is frequency modulated the following occur:– The frequency changes – The amplitude in the fundamental carrier

changes.– Multiple sidebands now have carrier power– For Example . . .


Bessel Null Plot


Baseband to RF

• After signal combination the following occur:– Passage through Pre-emphasis– Modulation of RF carrier

• FM Typical

• PM Possible


Pre-emphasis & De-emphasis Networks


Modulator Analog Radio

75

-25 dBm

FrequencySynth sizer

BBTEST

IN

30 dB

-55 dBm

AntennaMonitor-30 dBc

+30 dBm(+24 dBmOptional)

WGCMR 137

Antenna Coupling Unit

-20 dBm

HF Signal

Pre-emphasis

Composite TLP

ModulationHere

AntennaCouplingCarrier

Osc.

DTS

Digital Microwave

Digital Systems

Digital Transmitters

Digital Receivers


Typical System Configuration


Digital Transmitter

• Digital Transmitters contain the following:– Pulse input equipment (I/O Interface)

• Pulse Conversion• TDM Mux for multiple signals • LBO

– Band Pass Filters – BPF– RF Carrier Source Oscillators– I and Q splitters – Summing Amplifiers– Power Amplifiers


Digital TransmitterBlock


QPSK Modulator Diagram


Digital Modulation

• Modulating Steps– AMI/B8ZS to NRZ Conversion

– Data Line Splits• I-- Lines

• Q– Lines (Quadrature 90° phase shift)

– Mixing with Source Oscillator

– Summing Combined RF Signal

– FCC Mask Filter

– Example ..\Microwave Course\QAMGIF.gif


Signal Processing

• DS1 Signals arrive at Modem (I/O) as– AMI– B8ZS– 1.544mb/s / T1

• DS3 Signals arrive at Modem (I/O) as– B3ZS– 44.736mb/s / DS3

• OC3 Signals arrive at HLM on Fiber @– 155.220mb/s


Signals Change

• Signals are converted to NRZ signals

• Signals are passed thru a LPF


Simple Digital Modulation Techniques

0 1 1 0 0 0 1 1 Baseband

ASK0 = +/- 250 mV1 = +/- 500 mV

FSK0 = - 4.5 Khz1 = +4.5 Khz

PSK0 = 0°1 = 180°


4-Level Digital Modulation

0 1 1 0 0 0 1 1 Baseband

ASK00 = +/- 125 mV01 = +/- 250 mV10 = +/- 375 mV11 = +/- 500 mV

FSK00 = - 4.5 Khz01 = -2.8 Khz10 = +2.8 Khz11 = +4.5 Khz

PSK00 = 45°01 = 135°10 = 315°11 = 225°

-2.8 +2.8 -4.5 +4.5


QPSK PatternQ

00100

01

1

0111

I


I & Q Vector ValuesQ

I

0011 0111 1011 1111

0010 0110 1010 1110

0001 0101 1001 1101

0000 0100 1000 1100

00 01 10 11

A

0

-2 -1 +1 +2

11 +2

10 +1

01 -1

11 -2

16 QAM

Change Amplitude

Change Φ


Phase & Carrier at 64 QAM

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

+7L

+5L

+3L

+L

-L

-3L

-5L

-7L

-7L -5L -3L -L +L +3L +5L +7L I

Q


128 QAM Phase AmplitudeCARR 1

CARR 2

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

19

20

21

22

23

24

25

26

31

32

33

34

35

36

37

38

43

44

45

46

47

48

49

50

55

56

57

58

59

60

61

62

67

68

69

70

71

72

73

74

79

80

81

82

83

84

85

86

+7L

+5L

+3L

+L-L

-3L

-5L

-7L

-7L -5L+L +L +L +L1

27

28

39

40

51

52

63

64

75

76

-3L

-5L

17

18

29

30

41

42

53

54

65

66

-3L

-5L

87

88

77

78

99

100

111

112

89

90

101

102

91103113

92104114

93105115

94106116

95107117

96108118

97109119

98110120

121

122

123

124

125

126

127

128-7L

-9L

-11L

-L-3L-9L-11L+L +L


Bandwidth Efficiency

128 QAM

DTS

Microwave PowerAmplifiers

Amplifier Characteristics

Amplifier Distortion

Amplifiers as Oscillators


Microwave Power Amplifiers

ATPC – Controls the Power outputRSL at Receiver drives ATPC

DTS

Microwave Receivers

Receiver Elements

Receiver Process


Receiver Characteristics

• Receiver Selectivity

• Receiver Sensitivity

• The RSL Curve

• The Digital Carrier– Carrier Recovery– Timing Recovery


Conventional Receiver

Most Receivers use IF sections


Direct Conversion Receiver

Typical of MDR 6000 RadioBandwidth restricted


Digital IF Sections

• The digital IF section performs:– Equalization– Interference suppression– Signal stability


Radio Link Multi-path Characteristics


Multi-path Distortion


Carrier Recovery

• Threshold for 10-6 BER Rate

• Ability to detect incoming carrier– Effects of SSBSC Modulation– Local Source Oscillator – Locking signal– Pulse Timing Recovery


Data Recovery

• Receivers detect and reconstruct original data – Block Coding

• Reed-Solomon

• Galois

• Hamming

– Convolution Code


Error Detection

• There is a difference between Detecting an Error and Correcting an Error– Common errors detected are:

• CRC

• BCH

• Bit Errors


Forward Error Correction(FEC)

• Common methods of detecting and Correcting data bit errors are:– BCH used in most SCADA applications– Reed-Solomon

• A Block Code

• Uses Parity checks


Reed-Solomon Codes

• Capable of Correcting a Single Error Symbol.• Similar to BCH Error Codes• Used in Harris Constellation Radio• Is Considered a Block Code


The Eye-Pattern

• True status of pulse recovery

• Determines jitter in timing circuit

• Determines Inter-symbol-Interference (ISI)


Eye Pattern


Single Sweep of Eye Pattern


The Terminal ACU

• The Antenna Coupling Unit – Circulates the TX and RX Signals– Isolate the TX from the RX– Protects amplifiers and filters


Antenna Coupling


Network Management

• Digital networks are often managed by a central system

• Internet Management Protocol (SNMP)

DTS

Testing Applications

Testing T1 Circuits

Test Set Operation

Test Patterns

Error Reporting


DSX1 Panel

• Purpose of the DSX1 Panel– Interconnection

• Terminates a Single Piece of Equipment

• Cross-Connects Two Pieces of Equipment

– Monitor Access• TLP = -20DB

• Level is dBdsx

432ΩIsolation


Terminating T1 Spans

Test Equipment terminates the circuit as follows:

Bridge = > 1000Ω

Term = 100Ω

DSXMON = 100Ω/Gain

Signal Level typically:

6v P-P = 0dBdsx

ZL= 100 Ω


LBO in Radio


T1 Configurations4 – T1 Radio

T1#1

T1#4

LBO

T1#2

T1#3

M12I/O

Each T1Has LBOSetting


The 28 T1 RadioConstellation


DS3 Microwave Interface

• Up to 3 DS3 Signals can be Connected • Data Rate can Interface to OC3• Fiber and Copper make a Connection• DS3-DSX Panel Connections• The DS3 Copper Connection –RG59


Typical DS3 Interface

M13 Mux

M13 Mux

M13 Mux

DS3

DS3

DS3

Radio optioned for 1 to 3 DS3 Channels


Constellation DS3Terminal


Digital Overview

• T1 Framing

• T1 Line Codes

• T1 Timing

• T1 Signal Levels


Network Elements

• DSX Panels – T1 and DS3 Electrical

• T1 Devices– Channel Banks– NIU’s to Telco Network– CSU – FT1


DS3 Overview

• Channelized Vs Unchannelized

• M13 Mux– Low Speed– High Speed

• Electrical Interface – DS3 & STS

• Optical Interface – T1 to OC-192


Test Equipment Setup

1ST

What to Test


Test Signals

Test Pattern REPLACES Traffic on T1Span . . . INTRUSIVE


Common Test Patterns

• All Zeros – AMI/B8ZS Provisioning

• All Ones – Copper – Max 1’s

• 3 in 24 – Stress to AMI Circuits– Minimum 1’s density 1/8– 15 Consecutive 0’s

• QRSS – Voice = average 1’s


T1 Errors

• 4 types of T1 errors:– BPV Errors, always on Copper– CRC Errors, always in ESF Framing– Framing Errors, 100% Accurate– BIT Errors – Out of Service Test


T1 Alarms

• Core Alarms– Red Alarm – LOS– Yellow Alarm – typically remote alarm


AIS Signals

• Alarm Indication Signal (AIS)– Unframed All 1’s– Available in most Terminal Equipment– Maintains Framing


T1 Loopbacks

• Available in most Terminal Equipment– Coastcom Mux– Microwave Radio– Digital Cross-connect (DCS)– CSU– NIU

DTS Migration to Digital Microwave Digital Fundamentals Testing Applications Making the Change.

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Transcript of DTS Migration to Digital Microwave Digital Fundamentals Testing Applications Making the Change.