march 2010proprietary & confidential1 sunrise telecom presents: cable 101 sales training –...

March 2010 Proprietary & Confidential 1

NOCEngineer

DOCSISEthernetATMSonetSS7

Sunrise Telecom Presents:Cable 101

Sales Training – CATV Products

By: Jerry Green

D’stream

Upstream

EthernetLink

On-Line

CM2000

Shift

ESC


Agenda

In the beginning……

System Architectures

Signal on the Network

Channel Allocations

Analog Channels

Digital Channels

System Sweep

DOCSIS

Future


It all began…..

1948 – John Walson of Pennsylvania installs an antenna on the mountain and runs twin-lead wires to his appliance store. TV sales soared. John began to connect customers to his antenna & changes the wire to coaxial cable to improve picture quality.

1948 - Ed Parson, of Astoria, Oregon built a CATV system consisting of twin-lead strung from housetop to house top.

1950 – Bob Tarlton, of Lansford Pennsylvania used coaxial cable on utility polls under a franchise from the city.

Community Antenna Television (CATV) was born.


First Network Architecture

System components:– Preamp installed at antenna– Maybe a ‘booster’ in the tree– 300 ohm ‘Railroad Track’ wire

Number of channels:– 1 to 10

Performance:– OK to poor


Test Equipment of the 1950’s & 60’s

Jerrold 704

•Developed 1951

•Manufactured from 1952 to 1967

Jerrold 727

•Developed 1966

•Manufactured from 1967 to mid 70’s

Portable TV

•Measure levels with modified unit

•See distortions


Tapped Trunk Architecture

antennas

SignalCombining

Distrib.Amp.

tap

drop

Coax. cable

Headend


Trunk/Bridger Architecture

Typical amplifier cascades: 35+ amplifiers.

Satellite dish

Antenna Tower

TV Transmitter

Headend


Trunk/Bridger Architecture with Return

Microwave tower

Headend

Antenna Tower

TV TransmitterSatellite dish


Microwave Transport

Microwave tower

Headend

Antenna Tower

TV TransmitterSatellite dish


Hybrid Fiber Coax (HFC) Architecture

Fiber Link reduces the number of amplifiers in cascade

Fiber LinkHeadend

Antenna Tower

TV Transmitter

Satellite dish


Broadband networks HFC architectures

Antennas

Earth station

RemoteSite

MainHead-End

PrimaryHub 1

PrimaryHub 3

PrimaryHub 2

OpticalFiberRing

Secondary Hub 1

Node

Node

Node

Node

Node Node

Node

Node

Secondary Hub 2

Secondary Hub 3

Coax. cable

Optical Fiber

Hybrid Fiber-Coaxial Network Infrastructure


What is the Forward Path of the System

Return Equip.

R

H

LR

Forward Signal Path

Signal flow in the forwardpath is from the headend tothe customers home as indicated by the blue arrows.


Each amplifier compensates forthe loss in the wire before the amplifier under test.



Sample Amplifier

H

L

H

L

SlopeControl

ResponseEqualizer

AGC / ASC

H

L

Forward Amplifier

Return Amplifier Bridger AmplifierT.P.

-20 dB

T.P.-20 dB

T.P.-20 dB

Forward Path


What is the Return Path

Return Equip.

R

H

LR

Return Signal Path

Signal flow in the returnpath is from the customershome to the headend as shown by the blue arrows.


Each amplifier compensates forthe loss in the wire after the amplifier under test.



Sample Amplifier

H

L

H

L

SlopeControl

ResponseEqualizer

AGC / ASC

H

L

Forward Amplifier

Return Amplifier Bridger AmplifierT.P.

-20 dB

T.P.-20 dB

T.P.-20 dB

Return Path


Signals on the Network


Channel Types & Terms

Analog– NTSC, PAL, SECAM

Digital– 64QAM, 256QAM, 8VSB– Annex A, Annex B, Annex C– DOCSIS, EuroDOCSIS


Digital Channel Penetration

– Evolution of digital signals penetration in HFC transport architecture

C

200090 % analog TV10% digital TV

200560 % analog

TV40% digital TV

200825 % analog TV75% digital TV

20120 % analog TV 100% digital TV


Why change to Digital?

Bandwidth efficiency allows more program channels

Picture quality improvement

Better conditional access system

Supports HDTV

Not content dependent


PAL Cable Frequency Allocation


Channel Plan


Analog TV Standard Spectrum


– High Definition Television (HDTV)• 16:9 Format (widescreen)

NTSC PAL SECAM

Lines/Image 525 625 625

Images/second 30 25 25

Horizontal Frequency

15.734 kHz

15.625 kHz

15.625 kHz

Vertical Frequency 59.94 Hz 50 Hz 50 Hz

FormatHorizontal

linesHorizontal

PixelsImage Format

Display scanning

format

Images per second

1080p 1080 1920 16:9 Progressive 241080p 1080 1920 16:9 Progressive 301080i 1080 1920 16:9 Interlaced 30720p 720 1280 16:9 Progressive 24720p 720 1280 16:9 Progressive 30720p 720 1280 16:9 Progressive 60

480p 480 640 4:3 Progressive 24480p 480 640 4:3 Progressive 30480p 480 640 4:3 Progressive 60480i 480 704 16:9 Interlaced 30480i 480 704 4:3 Interlaced 30480i 480 640 4:3 Interlaced 30

HD

TV

SD

TV

Analog TV, NTSC / PAL / Secam / HDTV


Spectrum Analysis

Ch. 3 Spectrum AnalysisCh. Allocation

6 MHz

V/A 4.5 MHz

V/Color3.58 MHz

Lower Band Edge

60.00 MHz

Video Carrier

61.25 MHz

Audio Carrier

65.75 MHz

Lower Band Edge

60.00 MHz


525LINES

Horizontal Blanking

SC

AN

MO

TIO

N

Vertical Blanking

Receiver Frame (Raster)

485LINES

Vertical Sync

VITS Signals


Analog Channel in Time


Analog TV, TV Signal Modulation


Analog TV, test signal

• Basic video reference points, - Sync tip amplitude,

- Depth of modulation- Color Burst

• Test signals are added to measure signal quality- Vertical synchronisation

- Lines 7 to 21 are part of the non-visible image


Analog TV Chroma

– Chroma (or Color)

• Subcarrier 3.58MHz

• Suppressed carrier, AM modulation


Analog TV audio transmissions

– Frequency modulated audio sub-carrier• 4.5 MHz to 5.5 MHz, ± 25 kHz

– Pre-emphasis• Reduces high frequency transmission noise• Amplification of high frequencies before modulation• An inverse filter is applied after demodulation

– Encoding similar to FM stereo receivers• L+R base signal• L-R differential signal


Analog Measurements

Levels

Carrier Frequency

Carrier to Noise (CCN)

Coherent Disturbances (CCN, CSO & CTB)

HUM

In-Channel Response

Color Measurements


Analog Measurements

Carrier Levels


Relative Frequency, Hz

Relative

Amplitude in dB

Absolute Frequency, Hz

AbsoluteAmplitude,dBmV

Absolute levels and frequency only on visual carrier

All other amplitudes and frequencies are relative to the visual carrier

Absolute and Relative


CM2000/2800 SLM Mode


Multi-Channel Modes

Mini Scan

Scan


AT2500 Channel Level Display


CATV Measurements

Carrier to Noise (CCN)


Carrier to Noise Ratio

S.A. Noise Floor

Overload (TP)

Dynamic Range

CCN


CCN Measurement Algorithm

Measure Carrier Level

Measure Noise in a 30KHz Bandwidth

Correct for:– Bandwidth of noise to 4 MHz (add 21.25 dB)– Log Detection (add 2.5 dB)– Bandpass Filter Shape (subtract .5 dB)

Correct for Noise to near Noise

Correct for pre-amplifier if used

Subtract corrected noise from carrier level


Out of Band CCN Measurement

Carrier Level

Noise Measurement

NOTE:

Noise measurement most be corrected for video bandwidth & instrument measurement errors.


Setup Out-of-Band CCN Measurement

==> SINGLE ==> COMBINED

Center frequency = Video carrier frequency

==> IN-CH GATED

Press F5 to setup Measurement parameters.

Noise Meas set to clear area

OR


Out-of-Band CCN Measurement



CCN Result

Measurement Point

Noise near Noise Correction


Instrument Noise Measurement


In Band CCN Measurement

Measurement Range

CNR

NOTE:

Noise measurement most be corrected for video bandwidth & instrument measurement errors.


Gated CCN Measurement

Quiet Line of Video


Setup CCN Measurement


IN-CH

==> GATED


==> SINGLE ==> COMBINED

OR

Noise Meas set 2 MHz


CCN Measurement

CCN Result

Measurement Point

Noise near Noise Correction


CATV Measurements

Coherent Disturbances (CSO & CTB)


Second Order Inter-modulation

61.25 MHz 211.25 MHz 271.25 MHz

272.50 MHz

2IM = f1 ± f2

CSO


Third Order Inter-modulation

61.25 MHz 211.25 MHz 271.25 MHz

272.50 MHz

121.25 MHz

CTB

3IM = ± f1 ± f2 ± f3


CTB

0.75 MHz

.25 MHz

Visual Carrier

Aural CarrierLowerAdjacentAural

CSO

Where do the beats fall?

Composite Distortions are measured as a ratio in terms of dB down from the carrier.


Digital Beat Products

Add pix of digital channels beating together.


Manual Measurement Procedures

Measure carrier peak

Turn off carrier

Set 30 kHz resolution bandwidth

Narrow video bandwidth to 10 KHz

Composite level using marker

CSO or CTB = visual carrier - distortion level

Automatic cable analyzers can makes CSO measurement without interrupting the subscriber


Setup CCN/CTB/CSO

SINGLE

==> COMBINED


IN-CH

==> GATED



Initiate Measurement

Set Frequency to Video Carrier

Press F6 to MEASURE

User is prompted to remove test carrier at the headend once test has been initiated


CCN/CSO/CTB Results

CSO

CTB

CNR


CATV Measurements

Low Frequency Disturbancesor Hum


Hum Definition

Hum is ANY low frequency disturbance of the RF carrier

Program modulation sometimes interferes with hum measurements causing the measurement to look worse than it actually is.

Hum looks like AM modulation of the carrier

HUM problems reduce MER and increase BER


De

mo

du

late

d C

arr

ier

Vo

lta

ge

Time

Peak

Peak-to-Peak

% Hum = 100 X Peak

Peak-to-Peak

0

How is Hum Measured?


Hum Results


Digital HUM


CATV Measurements

In Channel Frequency Response


6 MHz

Lower

Channel

Boundary

Upper

Channel

Boundary

1.25 MHzVisual Carrier

0.75 MHz 1 MHz

4.25 MHz

Aural Carrier

(Off or Suppressed)

2 dB Measurement Area

Response Specification


525LINES

Horizontal Blanking

SC

AN

MO

TIO

N

Vertical Blanking

Receiver Frame (Raster)

485LINES

Vertical Sync

VITS Signals


Multi-Burst


Ghost Cancelation Reference


In-Channel Frequency ResponseResults Using GCR VITS


Digital Channels


Digital Measurements

Levels

Constellation

MER, EVM

BER

Frequency Response

Group Delay


Basic Components

Consistent Wave Carrier (CW Carrier)

Content– MPEG stream

• Multiplexed video/audio streams• HD video/audio• Audio content• Modem traffic• VOIP traffic


CW Carrier

Consistent Wave Carrier

Sine wave shape

At one consistent rate

At one frequency

Used to carry content over the network


CW Carrier

Frequency Domain

Time

Time Domain


Multiple CW Carriers

Time Time

Frequency Domain

Time Domain

F1 F2

F1 F2


Purpose of CW Carrier

It’s the BUS

Modulation is putting content on the Bus

Demodulation is taking content off the Bus


Describing a sine wave

Time

Amplitude

Phase

90°

Ref. Point

0°

Rate (Frequency):

• Time to complete a cycle

• Unit of measure = Hertz

• 1 cycle/sec = 1Hz


Putting Content on the BUS

0 1 0 1 0 0 1AM

ASK

0 1 0 1 0 0 1FM

FSK

Amplitude Modulation Frequency Modulation

0 1 0 1 0 0 1

PSK

M

Phase Modulation


Phase Relationships

0º 90º 180º

Time


Bi-Phase Shift Keying (BPSK)

Simplest method of digital transmission.

Data transmitted by reversing the phase of the carrier.

Carrier amplitude & frequency remains constant.

1 bit transmitted at a time

Advantage - Very robust method

Disadvantage - Consumes significant bandwidth (1 bit per hertz)

180º 0º

0 1


Amplitude and Phase Modulation

Higher data rates are achieved by adding amplitude modulation to the carriers

By having multiple levels of amplitude and phase more symbols can be transmitted in the same time period.

Two Levels of Amplitude Modulation and Bi-Phase Modulation Makes Four Possible

Symbols

00 01 10 11

180º 0º


QPSK

Two carriers at the same frequency, 90º out-of-phase, transmitted at the same time

One carrier is at 0º or at 180º, called the In Phase carrier – one carrier is at 90º or 270º, called the Quadrature carrier

The resultant vector of these two carriers designates the symbol to be transmitted.

A symbol is a digital word that is a combination of several bits.

In this case the symbol contains two bits

Using this method twice as much data can be transmitted in the same amount of bandwidth.


How QPSK symbols are transmitted

The digital receiver analyzes both the phase and the amplitude of the incoming signal and produces a bit stream that corresponds to that signal.

10|11|01|00|11

10 11 01 00 11

1011010011


Symbols, Symbol Rate, Bit Rate Symbols, Symbol Rate, Bit Rate

The Digital Language– If bits are the letters, then symbols are the words in the

language of digital modulation.

The bit rate is the number of bits sent per second

Symbols transmit one or more bits of digital information.

Symbol Rate is the number of symbols sent per second.

The transmission bandwidth is the symbol rate.

Symbol Rate = Bit Rate / Number of bits per Symbol


Describing a sine wave

Time

Amplitude

Phase

90°

Ref. Point

0°

Rate (Frequency):

• Time to complete a cycle

• Unit of measure = Hertz

• 1 cycle/sec = 1Hz


QPSK

Example: I carrier transmitted at 0º, Q carrier transmitted at 90º.

Resultant vector at 45º represents a symbol of 11.

If we needed to transmit a 01, then the I carrier would be at 0º and the Q carrier would be at 270º.

1145º

01315º

00225º

10135º

0º180º

270º

90º

Q Carrier

I Carrier


Quadrature Amplitude Modulation (QAM)

Analog color subcarrier similar to QAM modulation

Two signals carried at the same frequency out of phase

Two carriers called the I and Q, each carrying one-half of the data.

Each I & Q carrier transmits 8 levels of data for 64 QAM

Hence 82 equals 64 combinations or 64 QAM


In-Phase and Quadrature

I ChannelCarrierPhase

Q ChannelCarrier

Phase 90°Shifted

+ =

Carrier Phase Shift over time

Carrier

Amplitude

t

t180 Deg Shift

IQ


Creating a QAM signal

101 010 Local Osc

8 Level AMModulator

8 Level AMModulator

Bit Stream

OscillatorShifted 90°

Combiner 64 QAMSignal

Q Component

I Component

I & Q carriers, same frequency, but phase shifted by 90°

AM modulated

Combined make up the QAM signal.


QAM

QAM is Quadrature Amplitude Modulation

Two carriers at the same frequency, 90º out-of-phase, transmitted at the same time

Uses multiple levels of amplitude & phase modulation

Each carrier is a representation of half of the transmitted symbol.


QAM (Cont.)

If each of the I and Q channels transmits 4 levels of data

16 symbols transmitted in one clock cycle

Each symbol contains 4 bits

Known as 16QAM

8 levels per carrier

64 symbols transmitted

Symbol contains 6 bits

64QAM

16 levels per carrier

256 symbols transmitted

Symbol contains 8 bits

Known as 256QAM


Vectors and 16 QAM

10

11

01

00

10

11

Q 90°

I 0°

1010 1110

1011

1111

0100

0001

0000

0101

0100

I 180°

Q 270°

1011


64 QAM Constellation64 QAM Constellation

6 Bits per Symbol


256 QAM

8 Bits per Symbol


Digital Measurements

Digital Channel Power

MER, ENM, and EVM

Constellation Impairments

Pre and Post FEC BER

Adaptive Equalizer

QIA Measurements


Analog vs. Digital Power Measurements

6 MHZ

300 KHz

6 MHZ


Digital Power MeasurementDigital Power Measurement


Balancing System Levels


Modulation Error Ratio

MER is used as a single figure of merit for quality for RF digital carriers

It includes distortions such as CCN, CSO, CTB, laser compression, etc…. The sum of all evils.

A 256 QAM picture tiles at 28dB MER

A minimally good MER is 31 dB for 256 QAM at the back of the customer’s set.


Vectors and 16 QAM

10

11

01

00

10

11

Q 90°

I 0°

1010 1110

1011

1111

0100

0001

0000

0101

0100

I 180°

Q 270°

1011


MER and a Constellation


Acceptable MER

Output of QAM Modulator – 40 dB

Input to Lasers – 39 dB

Output of Nodes – 37 dB

Output of Subscriber Taps – 35 dB

At the input to the subscriber’s receiver – 34 dB

The absolute minimum is 31db.


Constellation Analysis


Noise Impairments


Phase Impairments

Looks good here in the Headend!

Looks good here in the Headend!


Coherent Interference Constellation


Coherent Interference in Freq Spectrum

Ingress from UHF off-air channels

Headend beats

CSO & CTB


Phase Impairments


Gain Compression


I/Q Gain Imbalance


Laser Compression


CM2000/2800 Constellation


BER Measurement


What is BER?

BER is defined as the ratio of the number of wrong bits over the number of total bits.

Sent Bits 1101101101

Received Bits 1100101101

BER = # of Wrong Bits

# of Total Bits=

1

10= 0.1

error


BER Display

BER is normally displayed in Scientific Notation.The more negative the exponent, the better the BER.Better than 1.0E-6 is needed after the FEC for the system to operate.

Lower and

Better BER

Fraction Decimal Scientific Notation1/1 1 1.0E+001/10 0.1 1.0E-01

1/100 0.01 1.0E-021/1,000 0.001 1.0E-03

1/10,000 0.0001 1.0E-041/100,000 0.00001 1.0E-05

1/1,000.000 0.000001 1.0E-061/10,000,000 0.0000001 1.0E-07

1/100,000,000 0.00000001 1.0E-081/1,000,000,000 0.000000001 1.0E-09

2/1,000 0.002 2.0E-03


Calculated Bit Error Rate

Using the amount of FEC overhead required to reproduce a bit string, the bit error rate can be calculated.

Using the FEC to determine the BER allows BER to be measured without removing the service which is usually required for most BER testing.


Forward Error Correction DecoderForward Error Correction Decoder

Forward error correction (FEC) is a digital transmission system that sends redundant information along with the payload, so that the receiver can repair damaged data and eliminate the need to retransmit.


Pre and Post FEC errors

Pre FEC errors– Errors that have occurred before the FEC has had an

opportunity to correct any of the errors.

Post FEC errors– Errors that could not be corrected

A cable modem will tolerate pre-FEC errors and the FEC will continue to correct pre-FEC errors up until 1E-06 or one error in one million bits. After that the FEC can do no more.

Post-FEC errors will cause retransmissions requests and slowdowns in a DOCSIS systems.


Pre and Post FEC BER

To get an accurate idea of the BER performance you need to know both the pre and post FEC bit error rate.

The FEC decoder needs a BER of better than 1 E-6 in order to operate.

Post FEC Bit errors are not acceptable.

You should look at both the Pre and Post FEC BER to determine if the FEC is working to correct errors and if so how hard.

FEC Decoder

Pre FEC BER

Post FEC BER


Parity

By adding an additional bit to a group of bits, errors can be detected within the group. This is known as a parity bit.

Even parity means that when the parity bit is added the group of bits including the parity always has an even number of ones. Odd parity means the group would have an odd number of ones.

If after transmission the number of ones is no longer even (for even parity), then there must be an error.

101110001 1

010111011 0

Parity Bit

Always Even Number of Ones

(Even Parity)

101100001 1

010111011 0

ErrorOdd Number

of Ones Indicates

Error


How Reed Solomon FEC Works

FEC works by addition additional data bits to the data stream to determine if errors exist and to try and correct them.

1011100010110100

Video Data Stream

1011 11000 11011 10100 1

1100 0

1=odd

0=Even

Stream With FEC Added

1011100010110100 1111 1100 0


How Reed Solomon Works

1011 11000 11001 10100 1

1100 0

1011 11000 11011 10100 1

1100 0

Error 1=odd

0=Even

Before Transmission

After Transmission the Bit in Error is

Detected and Corrected

Once you know a bit is wrong, correcting it is easy, if you know its wrong and its a zero, then it has to be a one.


BER and a Constellation


CM2000/2800 Constellation


Statistical Mode


Adaptive Equalizer

Every Digital Receiver has an Adaptive Equalizer

It performs 3 functions– Compensates for amplitude imperfections of the

digital signal– Compensates for group delay– Rings at the symbol rate to only allow one symbol

at a time into the digital receiver


Equalizer Mode


Digital Video – EQ Control

Standard EQ– Used in current equipment– More taps– Improved correction

Min EQ– Less taps– Mirrors performance of old

equipment– Disables Auto Diagnosis


Frequency Response

– Effective span equal to symbol rate

– Measurement calculated using Equalizer data


Amplitude Ripple

An in-service spectrum analyzer measurement


Group Delay

Definition:–Group delay is a measure of how long it takes a signal to traverse a network, or its transit time. It is a strong function of the length of the network, and usually a weak function of frequency. It is expressed in units of time, pico-seconds for short distances or nanoseconds for longer distances.

Measured in units of time,–Typically nanoseconds (ns) over frequency–Or, Delay per MHz.


Group Delay (Cont.)

In an ideal system all frequencies are transmitted through the system, network or component with equal time delay

Frequency response problems cause group delay problems

Group delay is worse near band edges and diplex filter roll-off areas


Group Delay (cont’d)

Excessive group delay increases bit error rate due to inter-symbol interference

DOCSIS spec.– no greater than 200nSecs per MHZ– Spec should be less than 100 nSecs per MHz


Group Delay Measurement


QIA Screen


QAM Impairment Analysis (QIA)

I/Q Gain and Phase– The phase and gain of both the I and Q carrier must be

equal in order for the constellation to be correct. – This impairment is caused by the QAM modulators. – The gain difference between the 2 carriers should be less

than 1.8% and the phase difference should be less than 1 degree.

Echo Margin– A measurement in dB of how far the taps are from the

template with the time equalizer measurement.– Caused by impedance mismatches in the system.– Should be at least 6 dB.


QIA Continued

Carrier Offset– Carrier frequency test.– Should be no more than +/- 25KHz

Estimated Noise Margin– Difference in dB between MER and the digital cliff– Depends on if the signal is 64 or 256 QAM– Minimum depends on where the measurement is taken– Example if the Minimum MER for 256 QAM is 28 and the

measurement is 34, than the ENM is 6

Frequency Response– Frequency response of the digital carrier– Should be less than 3 dB pk-to-pk


QIA Continued

Hum– Low frequency disturbances of the digital carrier– Same as hum on analog carriers, if the level is the same,

it’s the system, if higher on the digitals then it’s probably the QAM modulator

Symbol Rate Error– Should be less than +/- 5 ppm

Phase Noise– Jitter (changes in phase) of the oscillators, most likely

the up-converter– The phase shift or jitter should be less than .5 degrees


QIA Continued

Group Delay– Different frequencies travel through the same medium at

different speeds. So the lower the lower frequencies of the same carrier arrive at the receiver at different timing than the higher frequencies.

– Should be less than 50 nSec pk-to-pk

Compression– Caused by overdriving lasers or amplifiers– Shows up as corners pulling in at the outer corners of

the constellation– Should less than 1%


System Sweep


What does sweep do for the technician?

Measures the Frequency Response of the network

Confirms Unity Gain

View impedance mismatches– Bad connectors & cable– Bad devices

Checks both Forward and Return paths

Concept: If the system is flat and levels are correct, distortion will be minimal


Why Sweep?

Insures proper headroom

Preventative Maintenance

Non-obtrusive measurement

Look at network with a microscope


CM2800 Sweep

Compatible with 3010H/R

Forward Sweep– New 3 Dwell definition– Simultaneous Pilot &

Forward Sweep Results

Return Sweep– Switch Control (Phase

2)– Return Spectrum

(Phase 2)


Sweep System Facts

CM2800 compatible with 3010 version 5.53 firmware only

3010R & 3010H, same measurement hardware

3010H ships fully loaded – Basic unit support Return Path Monitor mode (both R&H)– Option 052 – Forward Sweep TX & Dual Path Mode– Option 061 – Switch control

3010 upgrade to ver. 5.53 – Version 4.x & above included with Calibration – Version 3.x available for an additional charge


Sweep Application

Spliter

CMTS

Downstream

US-1

US-2

US-3

US-4

Upstream 1

Upstream 2

Upstream 3

Upstream 4

AT1602 Switch

3010H Downstream

Upstream

AT2500

Fiber

To N

eighborhoods

Com

bine

r (2

0)

DownstreamChannels

Laser

OpticalReciever

Node

Forward & Reverse Sweep


Forward Sweep

Forward Sweep Path3010 Output Combined with Downstream SignalsSweep Level 16dB to 20dB below analog levelsSweep tilt = channel tiltNormalized sweep is a relative meas.Change in response between meas. Point and reference point

Spliter

CMTS

Downstream

US-1

US-2

US-3

US-4

Upstream 1

Upstream 2

Upstream 3

Upstream 4

AT1602 Switch

3010H Downstream

Upstream

AT2500

Fiber

To N

eighborhoods

Com

bine

r (2

0)

DownstreamChannels

Laser

OpticalReciever

Node


Reverse Sweep

Reverse Sweep PathDS Comms Combined with Downstream Signals (Comms only)Test signal inserted in field, measured by 3010H, meas. sent to field instrument on DS CommsMust know your reference points & design levels

Spliter

CMTS

Downstream

US-1

US-2

US-3

US-4

Upstream 1

Upstream 2

Upstream 3

Upstream 4

AT1602 Switch

3010H Downstream

Upstream

AT2500

Fiber

To N

eighborhoods

Com

bine

r (2

0)

DownstreamChannels

Laser

OpticalReciever

Node


Network basics

Unity Gain Concept– Total System Gain equals Total Loss– Gain = Loss or Gain/Loss = 1– Forward Path:

• Constant Output Levels• Amp compensates for cable before

device– Return Path:

• Constant Input Levels• Amp compensates for cable after

device• Same cable forward amp is

compensating for.

Sweep Insertion– ~ 17 dB Below Channels– System Level to Sweep Delta will

Remain Consistent– Matches Design Level Tilt

Unity Gain Network

Input – Cable Loss + Amp Gain = Output

Low Pilot High Pilot

Design Pilots”Low = 32High = 36

Sweep Insertion Level


Reality of Frequency Response

Output Levels and Slopes are customized to provide the best performance

Highest Carrier to noise Ratio (CC/N & MER)

Highest Carrier to Distortion Ratio (CSO, CTB, ect.)

Com

bine

r (2

0) Node

45

40

35100 300 500 700

40

35

30100 300 500 700

40

35

30100 300 500 700

40

35

30100 300 500 700

40

35

30100 300 500 700

10

0

-10100 300 500 700


How Sweep Works with no Sweep Table

50 4501 MHz

400 measurement points

Transmitter output witha blank sweep table.

The sweep frequency resolution is determined by the start andstop frequencies in areas of the spectrum where no frequencies arein the sweep table.

Sweep Resolution = (Stop freq... - Start freq...)

400 points=(450MHz - 50MHz)

400 points=1MHz/point


Components of the Sweep Table

Stop freq... = 450MHzStart freq... = 50MHz

57.20MHz 63.20MHz

61.25MHz


What is the Forward Path of the Cable System

Return Equip.

R

H

LR

Forward Signal Path






Lash-Up for Forward Sweep Set Up

Forward Combiner

RF In RF Out

To ForwardLasers


Forward Sweep Setup Flow

Setup Channel plan

Connect the input of the 3010 to a port containing all the channels on the network

Set Forward Sweep mode to Fast

In the Sweep Parameters screen set the following:– Start Freq. to your start frequency– Stop Freq. to your stop frequency– Comm’s Pilot Freq. to a clear area of network spectrum– Scan Type to Phantom– Channel Plan to the Channel Plan you created– Sweep Table to None


Forward Sweep Parameters Screen

Start Frequency

Stop Frequency

Communications Pilot Frequency

Scan Type

Frequency PlanCreated for

system under test

Sweep Table(Set to None to create anew table.)

3010H


Forward Sweep Setup Flow

Scan the network and the instrument creates the basic Sweep table for you

Add system pilots and edit table

Save the table

Set the level & slope

Your done!!!!


Table Entries for other type signals

Digital Signal – (Places sweep point between Digital Channels)– Frequency = Channel Center Freq.. – Guard band = 1/2 Channel bandwidth– Dwell = 0

Digital Signal – (Measures Digital channel, no sweep point)– Frequency = Channel Center Freq.– Guard band = ½ Channel bandwidth + 0.1 MHz– Dwell = 3

Phantom Carrier Setup– (Sweep point in Vestiges Sideband) – Frequency = Center Freq. + 200 kHz– Guard band = ½ Channel bandwidth – 0.1 MHz– Dwell = 0

System AGC or Setup Pilot Channels– Frequency = Video carrier frequency– Guard band = 1MHz– Dwell = 0


Forward Sweep Level

Sweep points between Digital Channels– Sweep points must be at least 17dB or greater below analog

video level

No sweep points around Digital Channels– Sweep points should be at the same level as the measured

digital channels


Sweep Setup

Go to SETUP / SWEEP

– Enter / Select the Low and High System Pilot

– Enter the Forward Sweep Communications Pilot Frequency (per 3010 setting)

– Enter the Reverse Sweep Communications Pilot Frequency (per 3010 setting)

– Check “Get New Table” to force download of new Forward Sweep

– SAVE & EXIT


Sweep Setup

Go to SETUP/LIMITS and SWEEP tab – Select the Location from the Pull Down

Menu

– Set the Downstream Sweep Limits for

• Low System Pilot min & max

• High System Pilot min & max

• Tilt max (we will add min)

• Peak-to-valley max

– Set the Upstream Sweep Limits for

• Tilt max (we are adding min)

• Peak-to-valley max

– SAVE & EXIT

Sweep Limits Screen


Sweep Tools

View Sweep Table


Screen Annotations – Forward Sweep

Freq. & dB/Div Control

View Sweep Table

Trace control – (only active when

reference is selected)

Site File

Select Reference

Attenuator– Sets Dynamic range

System Pilot Freq. & Level

P/V freq. range set by Vert. Marker Position

Save Ref. File


Forward Sweep

First Connection– Communication Icon (lock symbol) will flash

yellow, Markers & start stop will update.

– If Comms Icon not flashing - Adjust Attenuation• If test point system levels are > 10 dBmV,

increase the attenuator setting. If < 0 dBmV, decrease attenuator setting.

– Wait for sweep table download (or press F4 on 3010)

– Note the sweep trace and the pilot graphs. Pilots should be 10 to 15 dB above sweep.

– Note markers• Use Touch Screen or Arrows• Tilt & Peak-to-valley Calculated on Markers• Click on the SAVE icon at top tool bar and enter

a name for a reference file.

Lock Symbol


Sweep ReferenceSweep Reference

Sweep File are used as a Reference

Select a Reference File

– Sweep Display will be the difference between Ref and current results


Referenced Forward Sweep

– Click REFERENCE, select saved file.

– RED trace = Live Trace – Reference Trace

– Automatically adjusts to 2 dB/Div

– Click A, B, A&B, A-B to toggle Trace (Live, Reference, Both or Difference Traces)

– Low & High Pilot Frequency & Levels are Displayed

– Tilt & Peak to Valley calculations based on Vertical Marker Position


Return Sweep Configuration

Return Equip.

R

H

LR

Return Signal Path






Alignment Issues & the Return Path

The monitor point is some distance from the adjustment point.

The communications between the 3010R and 3010H is through the system under test.

Interference on the return or forward path can affect the communication between the instruments.

The Ingress detection system is used to troubleshoot interference on the return path.


Reverse Sweep Communications

Reverse Sweep PathDS Comms Combined with Downstream Signals (Comms only)Test signal inserted in field, measured by 3010H, meas. sent to field instrument on DS CommsMust know your reference points & design levels

Spliter

CMTS

Downstream

US-1

US-2

US-3

US-4

Upstream 1

Upstream 2

Upstream 3

Upstream 4

AT1602 Switch

3010H Downstream

Upstream

AT2500

Fiber

To N

eighborhoods

Com

bine

r (2

0)

DownstreamChannels

Laser

OpticalReciever

Node


3010H Polling Sequence

3010H Sends New User Pollmessage on Forward Pilot

3010H sets switch string tonext polling set

3010H monitors return pilotlistening for field units

Receives data

Good Data is received

New field unit is placed on theuser list displayed on 3010H

3010H services any field unitson line switching ports as

required

3010H Broadcastspectrum measurement

on forward pilot

3010H services new user

Yes

No

Yes

No


Return Sweep Headend Lash-Up

Forward

Combiner

RF out

To ForwardLasers

RF in

Return Receivers

To Return Processing Equipment


Connecting the 3010R to the 3010H back to back

3010H

Input

Output OutputInput


Return Sweep Setup

Set dynamic range for measurement

Full Scale (FS) setting in Spectrum Scan

If < 5 return paths connected to 3010 or using AT1600 Switch– Set FS for modem traffic to upper division of display

If > 5 return paths– Set FS for noise floor below second division of display

Remember the setting!


Return Sweep Setup (Cont.)

Set Switch driver if connected to a switch

Set Return Sweep mode to Fast

In Return Sweep Parameters screen set the following:– Start Freq. to your start frequency– Stop Freq. to your stop frequency– Forward Pilot to a clear area Forward Path spectrum– Return Pilot to a clear area Return Path spectrum– Ret Swp Table to None (to create new table)


Return Sweep Setup (Cont.)

To Speed up sweep– Enter frequency every 1 MHz – Guard band = 0.5 MHz– Dwell = 0

Save Table

Set Forward Pilot level 10 dB below the analog channels

You are done!


Screen Annotations

Freq. & dB/Div Control

View Sweep Table

Trace control – (only active when

reference is selected)

Site File

Select Reference

Attenuator– Sets Forward Pilot

Dynamic range Source Level/Slope Controls

P/V freq. range set by Vert. Marker Position

Save Ref. File


Reverse Sweep

– Upstream sweep table is automatically Downloaded

– Communication Icon (lock symbol) will flash yellow, Marker Freqs. & start / stop will update

– • If test point system levels are above 10

dBmV, increase the attenuator setting. If below 0 dBmV, decrease attenuator setting.

– – Set the Transmitter Level for the

appropriate Injection Level

• Peak reference level limited by 3010H setting

– Note Markers• Tilt & P/V Calculated on Vertical Marker

Position


Referenced Return Sweep

– Click REFERENCE, select saved file.

– RED trace = Live Trace – Reference Trace

– Automatically adjusts to 2 dB/Div

– Click A, B, A&B, A-B to toggle Trace (Live, Reference, Both or Difference Traces)

– Tilt & Peak to Valley calculations based on Vertical Marker Position


Bi-directional Test Point

Typical Amp diagrams

How to connect

Splitter

Set the Test Point Loss to 3 dB to compensate for the Splitter or for the Splitter and Test Point loss.


Directional Test Points

Amp Configurations are Tailored for the Span they serve

Diplexers Separate the Upstream & Downstream Path

Pads adjust the Flat Gain of Amplifiers

Equalizers Compensate for Cable Loss

Forward Pad Forward EQ

Reverse Pad Reverse EQ

Forward InputTest Point

Reverse OutputTest Point Reverse Input

Test Point

Forward OutputTest Point

RF InRF Out

Reverse EQ Reverse PAD


Connecting the 3010R to the 3010H in the System

3010H

Fiber Node

3010R

Forward PathFiber Laser

Return PathFiber Receiver

RF in

RF out


What is Ingress?

Ingress refers to interference typically found on the Return Path. Most timesit is caused by signals entering the systemfrom the customer drop.

When ingress is detected by the 3010H, the it makes a spectrum scan measurement and broadcasts the display data to the fieldon the forward Pilot.

When a 3010R receives the BroadcastIngress message, it is displayed over F3.Pressing F3 with the message displaywill allow you to view the spectrum scanmeasurement from the 3010H

Return Path with Ingress

Return Path without Ingress

3010R


When Ingress is a Problem.

F3 F3

A flashing SquareIndicates loss of

ReturnCommunications

Indicates Ingress

detectionat the 3010H

A flashing symbol indicatethe Forward pilot is receivedfrom the 3010H

A solid symbol indicates noForward Pilot communications

Pressing F3 will activate the

Broadcast IngressMeasurement

3010R


The Typical Return

H

L

FiberNode

Optical

Receiver

Optical

Receiver

Optical

Receiver

CoaxDist.Network

H

L

FiberNode

H

L

FiberNode

To CMTS Receive PortSpare Splitter Leg


The Funnel

Noise from every nook & cranny in the system ends up at the CMTS receive port.

H

L

FiberNode

Optical

Receiver

Optical

Receiver

Optical

Receiver

CoaxDist.Network

H

L

FiberNode

H

L

FiberNode


You can’t get there from here

H

L

Optical

Receiver

Optical

Receiver

Optical

Receiver

CoaxDist.Network

H

L

H

L

FiberNode

To CMTS Receive Port

Spare Splitter Leg

The actual Call might be here

The problem

could be here …

or here …

or here …

or the problem could be anywhere in these three nodes.


Upstream Impairments

Common Path Distortion

Fast transient noise

Ingress


Upstream Ingress

Return Path with Ingress

Return Path without Ingress Ingress refers to interference typically found on (but not limited to) the return path. Most ingress comes from the drops.

Some sweep systems detect ingress on their return sweep data frequency and broadcast the display data to the field on the forward data carrier for display.


Corrosion & Diode Effect

Crystallization occurs and the corrosion creates thousands of small diodes between the two metals

Diodes are non-linear devices that can act as frequency “mixers” in a CATV plant


Frequency Mixing

Mixing two frequencies (F1 & F2) will yield four results:

F1

F2

F1 + F2

F2 – F1

55.25 MHz

61.25 MHz

116.50 MHz

6.00 MHz


Common Path Distortion

27

Corroded ConnectionA corroded connection causes mixing

The resulting impedance mismatch also causes reflections

The mixing products are reflected right back into the return amplifier.

The diplex filter takes out everything above 42 MHz.

Downstream Signals

Difference frequencies reflected upstream(~6, 12, 18, 24…)


CPD in 6 MHz Intervals

Because the channels in the forward system are 6 MHz apart, the sum & difference frequencies occur at 6 MHz intervals as well.


Other Non-Linear devices

Other non-linear devices can create return path problems

Splitters utilizing toroid wound coils can also be non-linear and create mixing problems.

A cable modem transmitting at high levels can saturate the toroids forcing them to become non-linear.


Spectrum Display Limitations

Scanning Spectrum Analyzers measure only one band of frequencies at any given instant.

Frequency Range Where

Measurement is Being Made at

That Instant

Frequencies Stored From Last Pass of

Filter


Fast Intermittents

If the spectrum analyzer is at another frequency when the transient appears it will not be displayed.

A transient happening at this time will be missed by the filter unless it is still there when the filter comes

by again


3010Switch Control Feature

Setup and Operation


Switch Control Description

3010H– Adds switch driver for AT160x & RPS switches

3010R– Adds remote switch control – Single node return sweep

Requirements– Firmware version 5.53 or greater– Option 061 turned on (Shown on opening screen)


Features

Auto node polling

Two switch drivers– AT1601 or AT1602 – RPS switch

Remote switch control

Backwards compatible

Single node sweep


AT160x Configuration

Com

bine

r*

RF Inputs (Returns and Forward Feeds)

*Combining Ratio will depend on the number of switches used.

Maximum of 8 switches per 3010H

All RS232 cables arestraight-through typeunless otherwise noted.

AT-1601M Broadband 16 X 1 Multiplexer

STATUS

RESET

LOCAL

REMOTE

RF INPUTTEST POINT -20dB

RF OUT

B R O A D B A N DSUNRISE TELECOM


STATUS

RESET

LOCAL

REMOTE


RF OUT



STATUS

RESET

LOCAL

REMOTE


RF OUT


RS232 IN

RS232 OUT

3010 Cloning Cable

AT1601

AT1601

AT1601

3010H

RF Out


Cabling & Equipment

Cable - 3010H to Switch string– Cloning Cable– Male 9-pin to Male 9-pin Null Modem

Cable - Switch to Switch– Straight Through cable– Female 9-pin to Male 9-pin Straight Through

Combiner– Number of ports equals number of switches


AT160x Programming the Considerations

Each Switch in the string requires a unique address– Switch address is used to identify the ports. If you have

multiple 3010H/switch configurations in your system you may want to consider using different addresses for every switch in the system.

Use the Short Protocol (P1)

Use 38,4k baud rate (b2)


Programming the AT160x

Press Reset then Local/Remote button– Status light will turn yellow

Set Switch address, then press Local/Remote button

Set Protocol to P1 (Short Protocol), then press Local/Remote button

Set Band Rate to b2 (38,4k band), then press Local/Remote button

Programming Complete – Status light will turn green


3010H Programming

F3

3010H

F3

Switch Driver

Port Control


Switch Drivers

‘AT160x’ Driver– AT1601– AT1602

‘Alt SW1’ Driver– RPS Switch


RPS Limitations

Only one switch port in a string can be closed at a time.

Special switch lash-up required to minimize connection time.


RPS Configuration 1

Configuration using 1 communications port per switch

Switch

12

34

56

78

910

1112

1314

1516

Output

DC

3010H

ConnectthroughDC to

Splitter

12345678910111213141516

16-way

Comm Node = 15

RS232

RS232 toother

switches


RPS Configuration 2

Switch

12

34

56

78

910

1112

1314

1516

Output

12345678

DC

3010H

ConnectthroughDC to

Splitter

ConnectthroughDC to

Splitter

12345678

DC


8-way

8-way

Comm Node = 7

RS232

RS232 toother

switches


RPS Configuration 3

DC

3010H

ConnectthroughDC toSplitter


DC

1234

1234


DC

12344-way

4-way

4-way RS232

RS232 toother

switchesSw

itch1

23

45

67

89

1011

1213

1415

16O

utput

1234

Connect toother

switches.


Comm Node = 4


3010H Programming

RPS DriverSet to

4, 7 or 15

AT DriverSet to Last Polled port

AT160x Driver Alt SW1 Driver

Select switch driver first, then Comm Node


3010H Operation

F3F3

Communication Status


ADD REALWORX SLIDES


Troubleshooting DOCSISSystems


History of DOCSIS

DOCSIS 1.0– Open standard for high-speed data over cable– Best-effort– 1st products certified 1999

DOCSIS 1.1– Quality-of-Service (QoS) service flows– BPI+ with Certificates– Improved privacy with key distribution & encryption processes– SNMP for network management security


History of DOCSIS (Cont.)

DOCSIS 2.0– Goal: greater throughput & robustness on Return Channel

• Adds 64 & 128 QAM modulation to Return Channels• Higher symbol rate up to 5.12 Msps (BW 6.4)• Adds Forward Error correction, Trellis coding &

programmable interleaving to Return channel• Adds multiple modulation & access schemes

DOCSIS 3.0– Channel bonding (Increase capacity)– Enhanced network security– Expanded addressability (IPv6)


DOCSIS 1.0, 1.1 & 2.0 Reference Architecture

Courtesy of SCTE™


DOCSIS 3.0 Reference Architecture

Courtesy of Cable Labs®


Basic DOCSIS Setup

Fiber Distribution

CoaxDist.Network

Drop &HomeWiring

HL

FiberNode

10/

10

0 M

b E

ther

ne

tDHCP

TFTP

TOD

DNS

HTTP

ISPC M T S

Optical

Receiver

Up-converter

44 MHz

In

Out

System

signalsLASER

Signal to add’l

Laser inputs

Co

mb

ine

r

Upstream

Downstream Network

Modem


Basic DOCSIS Setup

Fiber Distribution

CoaxDist.Network

Drop &HomeWiring

HL

FiberNode

10/

10

0 M

b E

ther

ne

tDHCP

TFTP

TOD

DNS

HTTP

ISPC M T S

Optical

Receiver

Up-converter

44 MHz

In

Out

System

signalsLASER

Signal to add’l

Laser inputs

Co

mb

ine

r

Upstream

Downstream IP Network

Modem &Cust. Equip.


Cable Modem Registration

Physical layer (RF plant) - signal transport

DOCSIS and IP protocol layers - communicate messaging for modems to come online

The next slides illustrate the interaction of these layers in the registration process


DS Freq. Acquisition

CMTSCMTSCMTSCMTS cable modemcable modemcable modemcable modem

Wait for UCDWait for UCD

Wait for MAPWait for MAP

Wait for SyncWait for Sync

Yes

No

Next Frequency

Next Frequency

Yes

No

No

SyncSync Broadcast(Minimum one per 200 msec)

SyncSync Broadcast(Minimum one per 200 msec)

UCDUCD Broadcast (every 2 sec) UCDUCD Broadcast (every 2 sec)

MAP MAP Broadcast (every 2 ms) MAP MAP Broadcast (every 2 ms)

Scan DSScan DS Frequency for a QAM signalScan DSScan DS Frequency for a QAM signal



Adjust Timing Offset and Power OffsetAdjust Timing Offset and Power Offset

Wait forRNG-RSPWait forRNG-RSP NO

YES

RNG-RSPRNG-RSPRanging Response Contains:

•Timing offset•Power offset•Temp SID

RNG-RSPRNG-RSPRanging Response Contains:

•Timing offset•Power offset•Temp SID

RNG-REQRNG-REQInitial Ranging Request

Sent in Initial Maintenance time Slot Starting at 8 dBmV

Using an initial SID = 0

RNG-REQRNG-REQInitial Ranging Request

Sent in Initial Maintenance time Slot Starting at 8 dBmV

Using an initial SID = 0

Increment by3 dBIncrement by3 dB

CM Ranging


DHCP Overview

CMTSCMTSCMTSCMTS

DHCP RequestDHCP RequestAcks Initial lP Address andrequests Default GW, ToD Server,TOD offset, TFTP Server Addrand TFTP Boot Config File Name

DHCP RequestDHCP RequestAcks Initial lP Address andrequests Default GW, ToD Server,TOD offset, TFTP Server Addrand TFTP Boot Config File Name

cable modemcable modemcable modemcable modem

MAP MAP BroadcastsMAP MAP Broadcasts

ToD RequestToD RequestToD RequestToD Request

DHCP DiscoverDHCP DiscoverDHCP DiscoverDHCP DiscoverDHCP Reply (Offer)DHCP Reply (Offer)DHCP offers an IP addressDHCP Reply (Offer)DHCP Reply (Offer)DHCP offers an IP address

Bandwidth Request Bandwidth Request Use Temp SIDTemp SID (Service ID)Bandwidth Request Bandwidth Request Use Temp SIDTemp SID (Service ID)

ToD ResponseToD ResponseContains Time of Day per RFC 868RFC 868 (Not NTP)

ToD ResponseToD ResponseContains Time of Day per RFC 868RFC 868 (Not NTP)

DHCP Ack (Response)DHCP Ack (Response)Contains IP AddrIP Addr, plus additional information

DHCP Ack (Response)DHCP Ack (Response)Contains IP AddrIP Addr, plus additional information


TFTP & Registration


TFTP Boot File TransferTFTP Boot File TransferDOCSIS config file which containsClassifiers for QoS and schedule,Baseline Privacy (BPI), etc.

TFTP Boot File TransferTFTP Boot File TransferDOCSIS config file which containsClassifiers for QoS and schedule,Baseline Privacy (BPI), etc.

Registration RequestRegistration RequestSend QoS ParametersRegistration RequestRegistration RequestSend QoS Parameters

Validate file MD5 ChecksumImplement ConfigValidate file MD5 ChecksumImplement Config

TFTP Boot RequestTFTP Boot RequestFor ‘Boot File name’TFTP Boot RequestTFTP Boot RequestFor ‘Boot File name’

Registration ResponseRegistration ResponseContains Assigned SIDAssigned SIDModem registered

Registration ResponseRegistration ResponseContains Assigned SIDAssigned SIDModem registered

Registration AcknowledgeRegistration AcknowledgeSend QoS ParametersRegistration AcknowledgeRegistration AcknowledgeSend QoS Parameters


BPI+

Added in DOCSIS 1.1

If BPI+ is turned on, the modem will verify it’s authentication

Two Certificate types– Factory installed

• Higher level of security• Encrypted Certificate obtained by VeriSign and installed

by manufacturer– Self signed

• MAC address referenced in Certificate server for authentication

BPI+ eliminates MAC address spoofing


CM Registration Summary

Downstream channel searchRangingDHCPToDTFTPRegistrationOptional BPI Encryption (DOCSIS 1.1 or higher)

If modem contains eMTA, the next slide shows a table of the remaining 25 steps in the eMTA registration process


eMTA Registration

CM

MTA


Troubleshooting the Registration ProcessDownstream

Downstream– First step in the process– Make sure you are connected to the correct DOCSIS

channel• One channel may be fine and another in trouble

– Check performance• Levels (Remember adjacent channels)• MER, BER• Linear performance (Freq. response, Group Delay)

– If the Downstream is fine, Check the Upstream

Downstream


Troubleshooting the Registration ProcessUpstream

Upstream – Check Transmit Level

• High or Low could indicate a problem– Check Frequency & Modulation type

• May work using QPSK & not 16 or 64 QAM– BKER

• Should be little or no errors• Check for Lost or Discarded Packets

– Lost Packets indicate ingress– Discarded Packets indicate congestion– May be deceiving

Upstream


Troubleshooting the Registration ProcessIP Network

Network – Check IP addresses

• A CPE, or Emulator IP address is required to pass data through the network. Cable IP address is not enough

• Check Bootfile – If default file, you are not provisioned

– Test ability to pass data through the network• Ping – Test connectivity to another device• Tracert (Trace route) – Test IP route with transmit times through

the network.• Throughput – Test the ability to pass data through the network.• Browser – Test the ability to connect to a known site through the

modem

Network


Troubleshooting the Registration ProcessModem & Customer Equipment

Modem– Test ability to pass data through the customer modem

• Ping – Test connectivity to another device• Tracert (Trace route) – Test IP route with transmit times through

the network.• Throughput – Test the ability to pass data through the network.• Browser – Test the ability to connect to a known site

– If your test equipment is fine, it is probably the customer equipment

Customer Equipment– Connect customer PC to test instrument

• May have to reboot PC• If not working, maybe bad Net card

Modem


CM Network Analyzers

Cable Modem Network Analyzer are continually being developed & improved to troubleshoot DOCSIS systems

These powerful tools are designed around the premise that if you can quickly determine the source of the problems in a DOCSIS system, you will also save valuable time and un-necessary truck rolls while trying to troubleshoot and repair these problems.


Digital Network Analyzers

Connect to the CMTS

Obtain an IP from the DHCP server

Provide Downstream QAM information

Provide Lost Packets and BKER information in the upstream

Can do Ping, Trace Route and Throughput testing from the Cable Modem or PC emulator

Provide the ability to emulate another modem and then step you through the connection process using the customer equipment’s MAC address if BPI+ is turned off.

Provide special measurements for extended services such as VoIP and IPTV


Connecting to the Network

Select the Downstream DOCSIS channel


Connecting to the Network

Select UCD (upstream channel descriptor)


Connecting Process

Screen updates as the process is completed & displays the status


Instrument connected

Completed Range & Register Process

Modem On-line

Win CE Emulator IP

MTA IP


Downstream/Upstream Info

Analyzer view of Downstream & Upstream parameters.


Key IP Detail Parameters

IP Address

Gateway

TFTP Server

DHCP server

TFTP File name

& more


Key Downstream Details

Channel Displayed

Measurements– MER– Pre & Post FEC

BER– Errored Sec

Click on a Quadrant to Zoom In


Upstream Detail

Upstream transmit level

Lost Packets

Upstream Block Error Rate


Network Testing

Upstream

Downstream

Network

Modem


The Gateway

Fiber Distribution

CoaxDist.Network

Drop &HomeWiring

H

L

FiberNode

10/

10

0 M

b E

ther

ne

tDHCP

TFTP

TOD

DNS

HTTP

ISPC M T S

Optical

Receiver

Up-converter

44 MHz

In

Out

System

signalsLASER

Signal to add’l

Laser inputs

Co

mb

iner

CMTS converts DOCSIS to Ethernet or some other protocol.


Network Side of the Gateway

10/

10

0 M

b E

ther

ne

tDHCP

TFTP

TOD

DNS

HTTP

ISP

CMTS

ISP – Internet Service Provider(s)

DHCP – Dynamic Host Control Protocol Server hands out the IP addresses

TFTP – Trivial File Transfer Protocol Server sends the tftp file sometimes called bootp file or bootfile.

DNS – Domain Name Server Resolves domain names/IP addresses

HTTP – Hypertext Transmission Protocol Server used for download testing

TOD – Time of Day Server

Connection to HFC Network


Testing the Network

Ping Tests

Trace Route Tests

Throughput Tests

Protocol Analysis

Digital(DOCSIS) Network Analysis


How Pings Can Get Lost

A CMTS (or any router) will discard any ping packet received in error (upstream errors)

A CMTS will discard ping packets when the upstream bandwidth allocation of the originating modem is exceeded

DISCARDEDPACKETS


A Simple DOS ping

C:\ping 10.0.0.10Pinging 10.0.0.10 with 32 bytes of data:

Reply from 10.0.0.10: bytes=32 time<10ms TTL=128




Ping statistics for 10.0.0.10:

Packets: Sent = 4, Received = 4, Lost = 0 (0% loss)

Approximate round trip times in milli-seconds:

Minimum = 0ms, Maximum = 0ms, Average = 0ms

(TTL A set maximum amount of time a packet is allowed to propagate through the network before it is discarded.)


A Simple DOS Tracert

C:/tracert 38.211.178.2

Tracing route to SR-INTRA [38.211.178.2] over a maximum of 30 hops:

1 <10 ms <10 ms <10 ms 10.0.0.254

2 82 ms 82 ms 83 ms 172.16.1.1

3 82 ms 82 ms 82 ms SR-INTRA [38.211.178.2]

Trace complete.


Any file

Care needs to be taken when making throughput comparisons.

Processing time of the servers comes into play as well as the type of networks and routers that are involved.

HTTP Server

Throughput Testing

Network PC


Network Summary

Ping – A packet sent to a specific IP address and returned for test purposes.

Trace Route – An offshoot of the Ping test, but provides a trace of the packet through the IP network

Throughput – Downloading files to a PC to determine how much average data per second is being transferred


Downstream Testing

Upstream

Downstream

Network

Modem


Upstream Testing

Upstream

Downstream Network

Modem


Getting A BKER

NE NEPING#1

PING#2

PING#3

Ping Packets are numbered consecutively and accounted for as they are received.


Serial Pings & Lost Packets

PING #1 Sent PING #1 Received



4 PACKETS LOST(#4, 5, 6 & 7)



BLOCK ERROR RATE

# Lost Packets

Block Error Rate = ----------------------------------------

Total # of Transmitted Packets

Block Errors (Lost Packets are used to characterize return path performance)

It is possible to “Load Test” the Upstream DOCSIS system using BKER


Why Test Loading ?

Confirm that the customer is actually getting the upstream BW he is paying for

Confirm that the BW restrictions are working properly


Loading Calculation

Load = (50 Bytes + Bytes in Payload) X (8 bits/Byte)(kb/sec) (delay in msec) X 1000 msec/sec

Ping Packet Header & Overhead

P A Y L O A D (Packet Size)

0 - 1024 Bytes50 bytes

The upstream “load” is a function of the packet size and the packet delay.

Packet size = Header + Payload

Packet Delay – How often the packets are transmitted.


Approximate Loading

Delay Size Pkts/min Upstream Load(mSec) (Bytes) (approximate)

20 1024 3000 430 kb/sec

40 1024 1500 215 kb/sec

60 768 1000 109 kb/sec

*Based on a 50 Byte ping packet in addition to the size of the payload.


Upstream Fly in the Ointment

Upstream

Downstream Network

Modem

In three out of the four possible problem areas, the trouble can be solved by the service tech handling the call.

The Upstream piece of the puzzle is a different story.


You can’t get there from here

H

L

Optical

Receiver

Optical

Receiver

Optical

Receiver

CoaxDist.Network

H

L

H

L

FiberNode

To CMTS Receive Port

Spare Splitter Leg

The actual Call might be here

The problem

could be here …

or here …

or here …

or the problem could be anywhere in these three nodes.


Diplex Filter

H

L

Optical

Receiver

Optical

Receiver

Common

DOCSIS Network

Analyzer

C M T S

Up-converter

44 MHz

In

Out

Low High


Zero Span/Time Domain Mode

Frequency

Am

pli

tud

e TIME

In the Spectrum Mode the horizontal access of the analyzer displays frequency.

In the Time Domain mode the analyzer remains on one specified frequency and the horizontal access represents TIME.


Upstream Power Measurement

Because upstream Cable Modems transmit in very short bursts, it is difficult to measure their levels.

Putting the analyzer in Max Hold will allow you to get an approximation of the CM return levels.

Using the Time Domain Mode on the analyzer will allow you to get a very accurate power measurement of your cable modem signals.


Max Hold

Using Max Hold will allow you to get a relative reading on the Cable Modems in the return.

This Method is not very accurate, but does provide a good approximation.


Measuring Power in TDM mode

Measuring power of cable modems in the return system is a two step process.

Step One – Calculate the half-channel bandwidth of the Upstream signal in order to properly setup the analyzer.

Step Two – Measure the power using the analyzer average detector and make a bandwidth correction.


Calculating Analyzer Center Freq

1. Half Channel Width = Symbol Rate / 2

2. Offset the Center Frequency by 80% of the Half Channel Width:

New CF = Original CF - (half Channel Width X 80%)

3. Calculating New CF setting for a 1.6 MHz QPSK signal:

Half Channel Width = 1.6MHz (.80)/2

Half Channel Width = .64 MHz = 640 KHz

4. Analyzer CF = 11.98 MHz – 0.64 MHz

5. Analyzer CF = 11.34 MHz


Measuring the Level

Set the SPAN to 50-100 mSec and the Resolution Bandwidth to 1 MHz.

Set the trigger level near the top of the signal and adjust to where the preamble is clearly displayed.

Use the average detector and place a marker on the preamble

Make the bandwidth correction for the measurement.

Note: Making the measurement with a noise marker will give you the ability to automatically have the analyzer give you the BW correction. This summary was derived from a detailed Cisco procedure. More detailed information can be found on the Cisco website.


Measurement at Preamble

The Measurement Bandwidth is the symbol rate. In this case 1.6 MHz.

Adjust for B/W difference between RBW of 1 MHz and the 1.6 MHz measurement BW.

Some analyzers will calculate this automatically.

BW adjustment= 10 log BW1/BW2


Characterizing the Upstream

Return PathVerification, Test

& Troubleshooting

Test signal injected in field & measured on analyzer

Measure MER, BER, Constellation, Freq. Response, Group Delay


Modem & Customer Equip. Testing

Upstream

Downstream Network

Modem

Testing the modem, it’s provisioning and the PC connection is the last piece of the troubleshooting puzzle.


Network Analyzer as a CM

Customer

PC

Digital

Network

AnalyzerCMTS ISP

In this case the Network Analyzer is taking the place of the customer’s cable modem.

With some units, it is actually possible to “borrow” the MAC address of the customer’s modem and actually emulate that specific modem during the testing process


PC Emulator

Digital

Network

AnalyzerCMTS ISP PC

Emulator

Using a PC emulation mode, the network analyzer is able to do Ping, Trace Route and Throughput testing from the customer’s premise to any location on the internet.

The PC emulation also allows analysis of IP details related to the customers own MAC address


Key to CM Troubleshooting

The key to good DOCSIS troubleshooting is to identify which of the four areas need to be worked on.

Then as Kenny Rogers said “know when to hold ‘em and know when to fold ‘em”.


Architecture of the Future

????????


Thank You

QUESTIONS??


Group Delay

5 MHz

10 MHz

15 MHz

20 MHz

25 MHz

30 MHz

40 MHz

35 MHz

As different frequencies pass through a Cable System, some will move faster than others

5 MHz

10 MHz

15 MHz

20 MHz

25 MHz

30 MHz

40 MHz

35 MHz

5 MHz

10 MHz

15 MHz

20 MHz

25 MHz

30 MHz

40 MHz

35 MHz

SYSTEM

Filters &

Traps

SYSTEM

Filters &

Traps

T I M E

t


Equalizer Taps


What does sweep do?

Checks the Frequency response of the network

Checks both forward and return paths

Confirms unity gain

If the system is flat and levels are correct, distortion will be minimal


Setting the Dynamic Range in the 3010H

F1 F2 F3 F4

SCALE

ENTERPress to save change

3010H

march 2010proprietary & confidential1 sunrise telecom presents: cable 101 sales training –...

Documents

return slide

digital tv slide

system slide

network slide

eurodocsis slide

time slide

dependent slide

poor slide