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

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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

Documents

mbs slide

rights reserved analog

change slide

rights reserved cw wave

rights reserved fm modulation

dts migration

digital radio

alarms digital loopback