DTS
Making the Change
Migration to Digital Microwave
Digital Fundamentals
Testing Applications
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
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DTS
Single VF Channel
U sab le Vo ice
B an dw idth
3.1 K Fla t
3 82 5 H Z
O ut-of-B an d S ig na lin g Ton e
E & M (-20 d B m Ø )
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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
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Analog and Digital Signal
Processing
• An analog baseband is the composite of all
– Voice and HF tones
– Noise in each channel
– Cumulative system noise
• Analog means Amplify
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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
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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
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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 . . .
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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
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DTS
CW Wave
REF
LE VE L
0 DBM
CEN
FREQUENCY
6 .5 3 5 G H z
S PA N /D IV
10 M H z
DBM
0
-1 0
TEK
492PG M
-2 0
-3 0
-4 0
-5 0
-6 0
-7 0
10 DB/
V E R T IC A L
D IS P L AY
30 D B
RF
AT T E N U AT IO N
3 .0 — 7 .1
FREQ
RANGE
-8 0
IN T
1 MHz
R E S O L U T IO N
B A N D W ID T H
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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 . . .
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Bessel Null Plot
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Baseband to RF
• After signal combination the following
occur:
– Passage through Pre-emphasis
– Modulation of RF carrier
• FM Typical
• PM Possible
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Pre-emphasis & De-emphasis
Networks
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Modulator Analog Radio
Composite
TLP
Modulation
Here
-55dBm
Antenna
Monitor
-30dBc
30dB
-20dBm
HF Signal
+30dBm
(+24dBm
Optional)
-25dBm
BB
TEST
IN
75
WG
CMR137
Frequency
Synth sizer
Pre-emphasis
AntennaCouplingUnit
Carrier
Osc.
Antenna
Coupling
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DTS
Digital Microwave
Digital Systems
Digital Transmitters
Digital Receivers
Typical System Configuration
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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
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Digital Transmitter
Block
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QPSK Modulator Diagram
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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
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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
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Signals Change
• Signals are converted to NRZ signals
• Signals are passed thru a LPF
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Simple Digital Modulation
Techniques
0
1
1
0
0
0
1
1
B aseband
ASK
0
=
1
=
+ /- 2 5 0 m V
+ /- 5 0 0 m V
FSK
0
= - 4 .5 K h z
1
= + 4 .5 K h z
PSK
0
=
0°
1
= 180°
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4-Level Digital Modulation
0
1
1
0
0
0
1
1
B aseband
ASK
00 =
01 =
10 =
11 =
-2 .8
+ 2 .8
-4 .5
+ 4 .5
+ /+ /+ /+ /-
125
250
375
500
mV
mV
mV
mV
FSK
0 0 = - 4 .5 K h z
0 1 = -2 .8 K h z
1 0 = + 2 .8 K h z
11 = + 4 .5 K h z
PSK
00 = 45°
01 = 135°
10 = 315°
11 = 2 2 5 °
DTS
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QPSK Pattern
Q
10
00
0
1
0
I
1
11
01
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I & Q Vector Values
Q
Change Amplitude
16 QAM
0 0 11
0111
00 10
0110
11
+2
10
+1
10 11
1111
1 01 0
111 0
Change
Φ
A
00
01
0
10
11
I
-2
-1
00 01
01 0 1
00 00
01 0 0
01
-1
11
-2
+1
+2
1 00 1
11 01
10 0 0
11 00
DTS
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DTS
Phase & Carrier at 64 QAM
57
49
41
33
25
17
9
1
26
18
10
2
27
19
11
3
28
20
12
4
+7L
58
50
42
34
+5L
59
51
43
35
+3L
60
52
44
36
+L
61
-7L
53
-5L
45
-3L
37
-L +L +3L
+5L
+7L
21
13
-L 29
5
62
54
46
38 -3L 30
22
14
6
63
55
47
39 -5L 31
23
15
7
64
56
48
40 -7L 32
24
16
8
I
Q
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128 QAM Phase Amplitude
CARR 1
121
11 3
101
89
77
6 5 -3L 5 3
41
29
17
102
90
78
6 6 -5L 5 4
42
30
18
103
91
79
55
43
31
19
9
1
56
44
32
20
10
2
57
45
33
21
11
3
58
46
34
22
12
4
67
+7L
122
11 4
104
92
80
68
+5L
123
11 5
105
93
81
69
+3L
124
11 6
-11L
106
-9L
94
-7L
82
-5L
70
-3L
125
11 7
107
95
83
71
126
11 8
108
96
84
72
127
11 9
109
97
85
73
128
120
11 0
98
86
74
111
99
87
75
11 2
100
88
76
-L +L
-L +L
-3L
-5L
-7L
+L
+L
+L
+L
13
+L1
CARR 2
59
47
35
23
5
60
4 8 -3L 3 6
24
14
6
61
4 9 -5L 3 7
25
15
7
62
5 0 -7L 3 8
26
16
8
63
51
39
27
64
52
40
28
-9L
-11L
DTS
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Bandwidth Efficiency
128 QAM
DTS
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DTS
Microwave Power
Amplifiers
Amplifier Characteristics
Amplifier Distortion
Amplifiers as Oscillators
Microwave Power Amplifiers
ATPC – Controls the Power output
RSL at Receiver drives ATPC
DTS
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DTS
Microwave Receivers
Receiver Elements
Receiver Process
Receiver Characteristics
•
•
•
•
Receiver Selectivity
Receiver Sensitivity
The RSL Curve
The Digital Carrier
– Carrier Recovery
– Timing Recovery
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Conventional Receiver
Most Receivers use IF sections
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DTS
Direct Conversion Receiver
Typical of MDR 6000 Radio
Bandwidth restricted
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Digital IF Sections
• The digital IF section performs:
– Equalization
– Interference suppression
– Signal stability
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Radio Link Multi-path
Characteristics
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Multi-path Distortion
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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
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Data Recovery
• Receivers detect and reconstruct original
data
– Block Coding
• Reed-Solomon
• Galois
• Hamming
– Convolution Code
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Error Detection
• There is a difference between Detecting an
Error and Correcting an Error
– Common errors detected are:
• CRC
• BCH
• Bit Errors
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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
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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
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The Eye-Pattern
• True status of pulse recovery
• Determines jitter in timing circuit
• Determines Inter-symbol-Interference (ISI)
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Eye Pattern
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Single Sweep of Eye Pattern
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The Terminal ACU
• The Antenna Coupling Unit
– Circulates the TX and RX Signals
– Isolate the TX from the RX
– Protects amplifiers and filters
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Antenna Coupling
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Network Management
• Digital networks are often managed by a
central system
• Internet Management Protocol (SNMP)
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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
432Ω
Isolation
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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
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LBO in Radio
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T1 Configurations
4 – T1 Radio
Each T1
Has LBO
Setting
T1
#1
T1
#2
T1
#3
L
B
O
M12
I/O
T1
#4
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The 28 T1 Radio
Constellation
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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
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DTS
Typical DS3 Interface
M13 Mux
DS3
M13 Mux
DS3
M13 Mux
DS3
Radio optioned for 1 to
3 DS3 Channels
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Constellation DS3
Terminal
DTS
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Digital Overview
•
•
•
•
T1 Framing
T1 Line Codes
T1 Timing
T1 Signal Levels
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Network Elements
• DSX Panels – T1 and DS3 Electrical
• T1 Devices
–
–
–
–
Channel Banks
NIU’s to Telco Network
CSU
FT1
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DS3 Overview
• Channelized Vs Unchannelized
• M13 Mux
– Low Speed
– High Speed
• Electrical Interface – DS3 & STS
• Optical Interface – T1 to OC-192
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Test Equipment
Setup
What to Test
1ST
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Test Signals
Test Pattern
REPLACES Traffic on T1
Span . . . INTRUSIVE
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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
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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
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T1 Alarms
• Core Alarms
– Red Alarm – LOS
– Yellow Alarm – typically remote alarm
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AIS Signals
• Alarm Indication Signal (AIS)
– Unframed All 1’s
– Available in most Terminal Equipment
– Maintains Framing
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T1 Loopbacks
• Available in most Terminal Equipment
–
–
–
–
–
Coastcom Mux
Microwave Radio
Digital Cross-connect (DCS)
CSU
NIU
DTS
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