bonding and grounding for iptv services...triple play, data/ip analysis solutions office: 972...

Jeff HarmonAccount Manager – Western RegionTriple Play, Data/IP Analysis SolutionsOffice: 972 692-3705Mobile: 972 670-2664Email: [email protected]

JDSU Presents The Cause and Effects of

Bonding and Grounding on xDSL IPTV Services

February 12th, 2009

© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION2

IPTV Service Offering over DSL ServicesAs the Service Provider of IPTV Services

• What’s are your customers expectations?

• If you can’t meet your customer’s expectations what’s at stake?

•You’ve qualified your copper loop for xDSL loopYou’ve tested for AC/DC Current and Resistance

Measured the pair for length

Measure Longitudinal Balance

Performed a TDR to check for bridetaps and other interferers

Checked for load coils

However, your customer is still complaining of tiling on their TV’s and they’re very dissatisfied with their service

It’s going on the second or third dispatch and the problems still exist

Wideband Noise


Wideband Noise Definition

Wideband noise is defined as noise in the spectrum of 25 kHz to 2.5 MHz range.

Ultra-wideband noise is defined as noise in the spectrum of 2.5 MHz to 30 MHz.

DSL circuits carrying voice and high speed internet services are effected by WB noise on the line but those effects are often less noticeable than the effects of WB noise on circuits carrying IPTV signals.

During a recent seminar a leading Cable TV authority discussed noise impairments that affect Cable TV signals within their Wideband RF frequencies. He noted that 500 kHz -28MHz is the noisiest portion of the RF spectrum in the plant. He further stated the true service effecting noise is between 500 kHz-15MHz. This is primarily due to AM radio, amateur radio, shortwave, and CB radios.


Causes of WB Noise

The single biggest causes of WB Noise on your outside plant is Pair Balance and Bonding and Grounding problems

The biggest problem with Bonding and Grounding schemes…

They were written for electrical protection rather than noise considerations

With high frequency xDSL signals bonding and grounding schemes may have to change to support noise interferes and ingress


The Goal of Bonding

Sheath Current is responsible for providing a magnetic field which helps to cancel at least part of what the power leads induce into the pairs.

Most any type of signal/harmonic that is induced (ingress) into the pairs becomes noise

To obtain maximum current in the sheath it is necessary to provide the least possible resistance in the bonding conductors and ground connections

Using #6 stranded copper wire or copper braid attached to the cable sheath with compression clamps having a large contact area is your best choice for bonding conductors


The Goal of Proper Grounding

As we look at Bonding and Grounding, Grounding is the most important of the two and also most difficult to achieve.

The purpose of grounding is to make sure there is a good electrical connection from the cable sheath to the soil/earth.

Herein lies the problem. The surface area of ground rod is really quite small The soil around the ground rod may be of high resistance

because of the soil content and moisture. Always remember if a better path to ground presents itself,

the sheath current will not flow to the ground rod but to the better path


Proper Grounding The best possible ground is the power company’s MGN

(multi-ground neutral), or a grounded neutral of a secondary power system, or a specially constructed grounding system

Using the MGN is critical where the topology of the power lines change (transformer, capacitor bank, tap, drop, and direction change) as you need to get those locally coupled signals returned to their source return.

If the locally sourced signals are not returned to their own source return they cannot be canceled as well as when they are returned to a distant return, thus you have noise ingress.

Please don’t think that ground rods serve no purpose as they do.

Ground rods are there for personnel and plant protection in case of a lighting strike or power cross.


Bonding and Grounding Schemes to support IPTV

If your DSL service has progressed to the point where you’re going to offer IPTV services there’s a chance your current bonding and grounding schemes may have to change.

In order to eliminate WB noise from your cable plant to support IPTV services, it is imperative that every pole or pedestal be properly bonded and/or grounded with #6 stranded copper wire or copper braid attached to the cable sheath with compression clamps having a large contact area.

It is also a good practice to seal every bond or ground with a dielectric sealant

Always avoid using two different dissimilar metals for your bonding and grounding schemes as two dissimilar metals will invite the formation of corrosion.


Why is Bonding and Grounding more important than ever?

xDSL evolution to higher frequency ranges for Triple Play Services- POTs to ADSL to VDSL

- Higher sensitivity to interferers/poor balance

Bridge Tap sensitivity increased

Wider frequency band = More interference opportunities

25kHz 1.1MHz 2.2MHz 12MHz Frequency 30MHz

ADSL2+

ADSL

VDSL

VDSL2

Tech

nolo

gy

17.66MHz


Noise level is determined by: – Size of the magnetic field– Distance from pair and the center of the field – Distance both run parallel

OSP Local Loop – Power Influence

Power Lines

Telephony

Power Influence


Caused when over-the-air radio-frequency signals (AM radio, amateur radio, short wave radio) couple into twisted-pair lines

Pair balance and proper bonding and grounding is critical

Frequency

Noi

se p

ower

leve

lRadio Frequency Interference (RFI)


Testing ADSL 2+ line quality

Graphical Results: The graphs provide a graphical representation of the bits per tone (BPT).

Dips sometimes represent areas where interference is degrading the ADSL signal.

Large empty gaps in tones represent noise interferes that have ingress into the line

Moving the Cursor to those dips or gaps will help to identify the affected frequencies.

Tone 256 (1104kHz), Bits 14

Using the Bits Per Tone Graph to help identify noise interferes

Presenter

Presentation Notes

Table 7 Noise sources and tones Noise Source Noise Frequency (kHz) Tone # Tone Frequenc y (kHz) ISDN BRI 40 9 38.8125 HDSL passband center 196 45 194.0625 HDSL passband max 392 91 392.4375 HDSL2 274 64 276 T1 passband center 772 179 772 E1 passband center 1024 237 1022


Identifying WB Noise on your pairThe two examples below show high wideband noise

These two examples show good noise readings, though the -51 dBm reading is getting near to the top of the threshold.


Understanding the dBm and dBrn Scales

Noise Thresholds can be measured with either a dBm or dBrn scale

dBm measures absolute power– 0 dBm equals 1 mW to the appropriate

load

dBr n measures dB above reference noise: – Reference noise 0 dBr n = -90 dBm

Scale show the relationship between dBm and dBrn

There is much confusions between these two scales

0 dBm 90 dBrn

-10 80

-20 70

-30 60

-40 50

-50 40

-60 30

-70 20

-80 10

-90 0

-64 dBm

or

26dBrn


Using a Spectral Analyzer

The purpose of this test is to analyze wideband noise across the VDSL spectrum

It is important to understand the information being displayed on the spectral noise graph. For VDSL circuits the noise floor should not exceed -100 dBm. The lower the noise floor on a VDSL circuits the better.

1. Often you can see the actual up and down stream VDSL signals on the spectral noise graph

2. The noise floor for a VDSL line should remain below -100 dBm.


VDSL Bonding and Grounding Trouble

-119 dBm noise floor

Good VDSL Sync levels however the customers IPTV signal is tiling

Bonding problems cause of noise Bonding problems corrected

Sync at Crossbox Sync at Customers NID

bonding and grounding for iptv services...triple play, data/ip analysis solutions office: 972...

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