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(1)

Characterizing Signal Leakage

from an All-Digital

Cable Network

Presenter: Mario Sebastiani

for

CCTA Technical Training Sessions August 14, 2012 - San Juan, PR

(2)

Seminar Summary

Topics review for

all-digital

HFC network:

Is it necessary to patrol for leakage?

Is the leakage spec the same as for analog?

Can QAM signals cause harmful interference?

Can off-air digital ATSC impair QAM signals?

Is CW/Video carrier necessary for patrolling?

What frequency should I troubleshoot egress?

Are vendors providing digital leakage gear ?

(3)

Technical Training Outline

 Examine reasons for a patrolling leakage program

 Demystify leakage characteristics & requirements

 Analyze leakage symptoms & measurements

 Concerns of leakage in an all-digital network?

 Characterising Signal Leakage in an All-Digital Cable Network (Courtesy of SCTE live learning, 2010)

http://www.myeventpartner.com/WebConference/RecordingDefault.aspx?c_psrid=ED50D98486

 Demonstration of QAM carrier impaired by analog or digital signals with MER/BER measurements

(4)

What is Leakage/Egress?

Definition:

- Undesired emission of RF energy generated by the coaxial plant

- Modulated RF signals radiating or leaking out of the cable network

(5)

Leakage & Ingress

Leakage

-

RF energy leaking out of the

coaxial environment

Ingress

-

RF or electrical

energy that enters the coaxial environment

(6)
(7)

Reason #1

to

Monitor

for Leakage

(8)

Off-Air Interference

Broadcast TV signals

Radio Mobile Communications

Public Services

Emergency Services

(9)

NCTA/EIA Spectrum Plan

Bande de retour Bande FM Bande moyenne

Bande Hyper Bande supérieure

Fréquences aéronautiques (restrictions d’utilisation) Fréquences Hertzienne (TV)

(usage limité) Fréquences Hertzienne (TV) (usage limité)

(10)

Frequency Allocation-Cable & Off-Air

EIA/NCTA Traditionnel Standard Terrestre EIA/NC Traditionnel Standard Terrestre T-7 7 98 A-2 109.275 Bande T 99 A-1 115.275 T-13 43 14 * A 121.25 471.25 1 45.75 15 * B 127.25 477.25 2 2 55.25 55.25 16 * C 133.25 483.25 3 3 61.25 61.25 17 D 139.25 489.25 4 4 67.25 67.25 18 E 145.25 495.25 4 MHz 19 F 151.25 501.25 5 5 77.25 77.25 20 G 157.25 507.25 6 6 83.25 83.25 21 H 163.25 513.25 201 XX 88.1 22 I 169.25 519.25 95 A-5 91.25 7 7 175.25 175.25 217 91.3 8 8 181.25 181.25 96 A-4 97.25 9 9 187.25 187.25 247 97.3 10 10 193.25 193.25 97 A-3 103.25 11 11 199.25 199.25 299 107.7 12 12 205.25 205.25 300 XX 107.9 13 13 211.25 211.25 Bande moyenne Bande haute Bande FM radio et télévison par câble Bande basse Bande basse

(11)

Frequency Allocation-Cable & Off-Air

EIA/NCTA Traditionnel Standard Terrestre EIA/NCTA Traditionnel Standard Terrestre 98 A-2 109.275 23 J 217.25 525.25 99 A-1 115.275 24 K 223.25 531.25 14 * A 121.25 471.25 36 W 295.262 603.25 15 * B 127.25 477.25 37 AA 301.262 Radio Astronomie 16 * C 133.25 483.25 38 BB 307.263 615.25 17 D 139.25 489.25 41 * EE 325.262 633.25 18 E 145.25 495.25 42 * FF 331.262 639.25 19 F 151.25 501.25 43 GG 337.262 645.25 20 G 157.25 507.25 44 HH 343.262 651.25 21 H 163.25 513.25 65 471Q 471 777.25 22 I 169.25 519.25 69 495Q 495 801.25 7 7 175.25 175.25 70 501Q 501 8 8 181.25 181.25 71 507Q 507 9 9 187.25 187.25 100 651Q 651 10 10 193.25 193.25 101 657Q 657 11 11 199.25 199.25 157 993Q 993 12 12 205.25 205.25 158 999Q 999 13 13 211.25 211.25 Bande haute

Désignation du canal Porteuse audio (MHz) FRÉQUENCE DE CABLODISTRIBUTION ET DE RADIODIFFUSION (NTSC)

Bande moyenne

* fréquences aéronautiques

FRÉQUENCE DE CABLODISTRIBUTION ET DE RADIODIFFUSION (NTSC) Désignation du canal Porteuse audio (MHz) Bande

super

Bande hyper

(12)

Reason # 2

to

Monitor

for Leakage

Regulatory compliance requirements

for spectrum management, public

interest and public safety

(13)

Frequency Allocation-Cable & Off-Air

EIA/NCTA Traditionnel Standard Terrestre EIA/NCTA Traditionnel Standard Terrestre 98 A-2 109.275 23 J 217.25 525.25 99 A-1 115.275 24 K 223.25 531.25 14 * A 121.25 471.25 36 W 295.262 603.25 15 * B 127.25 477.25 37 AA 301.262 Radio Astronomie 16 * C 133.25 483.25 38 BB 307.263 615.25 17 D 139.25 489.25 41 * EE 325.262 633.25 18 E 145.25 495.25 42 * FF 331.262 639.25 19 F 151.25 501.25 43 GG 337.262 645.25 20 G 157.25 507.25 44 HH 343.262 651.25 21 H 163.25 513.25 65 471Q 471 777.25 22 I 169.25 519.25 69 495Q 495 801.25 7 7 175.25 175.25 70 501Q 501 8 8 181.25 181.25 71 507Q 507 9 9 187.25 187.25 100 651Q 651 10 10 193.25 193.25 101 657Q 657 11 11 199.25 199.25 157 993Q 993 12 12 205.25 205.25 158 999Q 999 13 13 211.25 211.25 Bande haute

Désignation du canal Porteuse audio (MHz) FRÉQUENCE DE CABLODISTRIBUTION ET DE RADIODIFFUSION (NTSC)

Bande moyenne

* fréquences aéronautiques

FRÉQUENCE DE CABLODISTRIBUTION ET DE RADIODIFFUSION (NTSC) Désignation du canal Porteuse audio (MHz) Bande

super

Bande hyper

(14)

Spectrum Chart

Aircraft Radio & Navigation

CH

98

CH

99

CH

14

CH

15

CH

16

108MHz

139MHz

Cable

Off-Air

123MHz 129MHz 135MHz

Aeronautical Service Bands

111MHz 117MHz

(15)

Spectrum Chart (cont’d)

CH 41

Aircraft Radio & Navigation

CH 42

324MHz

336MHz

Cable

Off-Air

327MHz 333MHz __

Aeronautical Service Bands

(16)

FCC/IC Regulations & Procedures

for Leakage Measurement

< 54 MHz & > 216 MHz = 15µV/m @ 30m

> 54 MHz & < 216 MHz = 20µV/m @ 3m

Use a calibrated half-wave dipole antenna

Antenna must be elevated 3 meters off the

ground and positioned 3 meters from the

leakage source

(17)

Patrolling for Leakage

30 meters

3

meters

2

µVm

(18)

µV/M

Standard unit of measure for Leakage

50 Ohm off air measurement

Voltage developed in 1 meter of

infinitely thin section of wire submerged

in a leakage field, produces 1µV of

(19)

Polarization Angle

Dipole

Monopole

(20)
(21)

Cumulative Leakage Index (CLI)

CLI is the net effect of the combination of all

the leaks in the system added together

These cumulative leaks form an invisible

cloud of unwanted RF energy over the cable

system

(22)

Required Actions

All leaks 20 µV/m must be logged and

fixed

Only leaks above 50 µV/m are used in CLI

calculation

All measurements taken outside 108-139

MHz must be converted as if they were

taken within the band

(23)

Reason #3

to

Monitor

for Leakage

Improves System Performance

Reduces Repeat Service Calls

(24)

Common Causes

70% of all leakage is caused by problems

between the tap and entry to the house

– Aging and environmental stress

– Physical trauma to cables or connectors – Loose drop connectors

– Inferior quality coaxial cable, passives, or connectors

(25)

Other Causes of Leakage

Improperly installed connectors

Cracks in the distribution and feeder cable

Animal chews

Poorly-shielded drop cable

Bad connectors at the tap

Bad/loose port terminators

(26)

Other Causes (Cont’d)

Customer installed equipment

Damaged amplifier housing or loose lids

Loose tap plates

Broken tap ports

Poor installation of splices and connectors

(27)

Tools

Dipole

(28)
(29)

Standing Waves

(30)

Electrical Noise

(31)

Characterizing Signal Leakage

from an All-Digital Cable Network

• Ron Hranac and Ray Thomas (Comcast)

have conducted field tests on the subject a

couple of years ago

• SCTE live Learning presentation on the

subject

• http://www.myeventpartner.com/WebConf

erence/RecordingDefault.aspx?c_psrid=E

D50D98486

(32)

Characterizing Signal Leakage

from an All-Digital Cable Network

Field tests were conducted in the Denver, Co area using an analog CW carrier and a 256

QAM carrier

CW test frequency was Ch. 18 @145.25 MHz Digital test with 256QAM carrier @ 147Mhz Digital test with power -6dBc from CW (video)

Testing leakage carrier in between 2 QAMs

(33)

Characterizing Signal Leakage

from an All-Digital Cable Network

 Review the characteristics of the analog and digital carriers

 Review type of modulation

 Where the RF energy is located

 Historical test instruments to measure leakage

 Troubleshooting gear

 MER/BER performance behavior being deteriorated by signal ingress

(34)
(35)
(36)

Analog A/V Carriers

4.5 MHz 3.59 MHz 6.0 MHz 0 -10 -20 -30 -40 -50 -60 -70 dB 4.2 MHz Video Carrier Audio Carrier Sous-porteuse couleur 1.25 MHz 3.58MHz Amplitude Modulation FM Modulation +/- 25 KHz

(37)

Analog C/I Objective Table

Red designates Visible interference Green designates Non-visible interference 4.5 MHz 3.59 MHz 6.0 MHz 0 -10 -20 -30 -40 -50 -60 -70 dB

(38)
(39)
(40)

Characterizing Signal Leakage

from an All-Digital Cable Network

Conclusion from Hranac/Comcast test results:

 Leaks from digital QAM carriers can cause

harmful interference to terrestrial users just like analog carriers

 Terrestrial RF energy can impair on QAM

signals depending on the level of the ingress

 Patrol leakage program should apply to all-digital systems

 The compliance spec for all-digital networks is similar as for analog cable systems

(41)

Characterizing Signal Leakage

from an All-Digital Cable Network

Summary and conclusion of SCTE tests (cont’d):

 A CW carrier is still the most cost/efficient method for testing and troubleshooting leakage

 The minimum frequency offset allocation to a QAM is 1 MHz

 The frequency range for leakage detectors can be from 108MHz ~147MHz (Aeronautical band)

 Allocating CW carrier between 2 QAM carriers will impair on both QAM carriers

(42)

Characterizing Signal Leakage

from an All-Digital Cable Network

Summary and conclusion of SCTE tests (cont’d):

 Some manufacturers are working on or already supplying leakage detection tools for digital QAM carriers

 Cost efficiency of digital leakage instrumentation will accelerate its deployment in all-digital cable systems

(43)

Leakage – Downstream Ingress – Facts

• Being leakage compliant with rules and

regulations increases the figure of merit of

the HFC network

• Higher MER levels throughout the RF

plant - greater signals reliability

• The average MER objective at the

subscriber tap of 33dB ~ 35dB

(44)

P

Operating margin Zone Risk Zone RS-FEC Crash Zone

MER TARGET - THE “CLIFF” EFFECT

Upstream 16 QAM >22dB 22dB - 20dB <17dB Objective

UP/Downstream 64 QAM >28dB 28dB - 26dB <23dB P- BER CER

Downstream 256 QAM >33dB 33dB - 31dB <28dB 1 x10-8 9 x10-7

(45)

Constellation Performance

(46)

QAM EVS

Troubleshooting in-channel ingress is

easy with

QAM EVS

mode

Typical ingress areas

• Loose connector • Broken shields • Tap plate loose • Home wiring

• CSO/CTB from house amp • Sweep inter-mod

(47)

BER

Digital signals work well until very close to the point of failure Measurement of digital carriers is critical in determining the system margin

 Signal level

 MER

 Pre/Post BER

 CER (Codedword Error Rate)

The BER helps to find problems related to point of failure.

 Gray lines designate marginal signal quality

(48)

BER/CER

BER

Pre: before FEC repair Post: after FEC repair

ERRORS

Corr = corrected codewords

uncor = uncorrectable codewords err sec = errored seconds

sev sec = severely errored seconds

Codeword Error Rate: Objective = 9x10⁻⁷

(49)

MER/BER Demonstration

(50)

Characterizing Signal Leakage

from an All-Digital Cable Network

Thank you, Gracias, Danki, Merci

to the CCTA members

Mario Sebastiani: msebastiani@incospec.com

http://www.incospec.com/resources/webinars/webinars.php

“Serving the industry since 1978

with pride, integrity and commitment”

(51)

Tools

Dipole

(52)

Some of Incospec’s Associates

References

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