DOCSIS 3.0

DOCSIS 3.0

Randy Francis Cable Networks Division

The HFC Pipe is Huge!

 New Specifications

– DOCSIS 3.0 Interface Specifications (released December 2006) – CPE equipment in development stages( Bronze, Silver, Full)

 Downstream data rates of 160 Mbps or higher

– Channel Bonding – 4 or more channels

 Upstream data rates of 120 Mbps or higher

– Channel Bonding – 4 or more channels

 Internet Protocol version 6 (IPv6)

– IPv6 greatly expands the number of IP addresses

• Expands IP address space from 32 bits to 128 bits

• IPv6 supports 3.4×10³⁸ addresses;

• Colon-Hexadecimal Format



1 x 256QAM => “up to” ~40Mbps

1 x 64QAM => “up to” ~30Mbps

DOCSIS^® 3.0 Overview

4 x 256QAM => “up to” ~160 Mbps

4 x 64QAM => “up to” ~120 Mbps

Maximum and (Maximum Usable)DownStream Speeds

Downstream

Version DOCSIS EuroDOCSIS

1.x 42.88 (38)

Mbit/s 55.62 (50) Mbit/s 2.0 42.88 (38)

Mbit/s 55.62 (50) Mbit/s 3.0

---4 channel

171.52 (+152) Mbit/s

+222.48 (+200) Mbit/s

3.0 +343.04 +444.96 (+400)

Un-Bonded Upstream Data rates

Channel Requirements

 Combines down and upstream channels for added performance

• “Technically” could support 10 bonded down streams.

• Plans are currently for 4 DS and up to 4 u/s channels to be bonded

– Do not have to be adjacent to each other – but must be within 60 MHz.

» “Bonded” in data layer – not Physical layer

» Each DS channel remains a 6 MHz 256QAM

» A DOCSIS 3.0 QAM can be a Primary or Secondary

» Primaries carry all info needed for a CM to register

» Secondary's do not have registration data – only payload

» ALL down streams can be provisioned as primaries but there MUST be at least 1 primary.

– Possible combinations of u/s and d/s

– 2x1, 2x2, 3x1, 3x2, 3x3, 4x1, 4x2, 4x3, 4x4

Security

 DOCSIS 1.0 had BPI ( Baseline Privacy Interface)

– Did not hardware authenticate Cable Modems

 DOCSIS 1.1 and 2.0 have BPI+

– Digital Certificate based security – No more spoofing MAC addresses

 DOCSIS 3.0 adds more enhancements – and the specification is now named “Security”, or BPI/SEC

 BPI/SEC encrypts data flows between the CPE and the CMTS

– BPI/BPI+ use 56 bit encryption – SEC uses 128 bit encryption

Pre-Equalization taps

Better performance under adverse plant enviroment

 Docsis 1.1 has 8 tap u/s eq

 DOCSIS 2.0/3.0 uses u/s24 tap eq

 Configured in response to the CMTS ranging request ( RNG-RSP)

 CMTS says give me a taste – CM responds with a burst

 CMTS analyzes response of the burst – and

instructs CM on how to configure its EQ taps ( Equalizer Coefficients)

DOCSIS 3.0 Flavors

 BRONZE

– Supports downstream bonding – Supports IPv6

 SILVER

– Supports upstream channel bonding – AES – Advanced Encryption Standard

• More secure than DES – Data Encryption Standard

– Support for IPDR

• IP Detail Record

• Allows “Consumption Based Billing” – Pay as you use

 FULL ( and you thought it would be gold?)

– All of Bronze and Silver

 Applies to CMTS only – not CM’s

 CMs from Cisco, Moto, Ambit & Others are now available

– 4x4 bonding only( Texas Instruments silicon

– Broadcom announced 8x4 silicon (400Mbs DS/160 Mbs US) in January 2009

 This is kinda important – you don’t want to have to upgrade twice. Think hard if 4x4 will be enough!

MSO Rollout of DOCSIS 3.0

 Phase 1

– Prepare plant

• Physical layer upstream and downstream

– Service turn-on

• Downstream Bonding

– Adding additional Downstream carriers

» Avoids Node Splitting

» Provides load balancing

– Relatively lower number of DOCSIS 3.0 customers on bonded channels

– Capacity utilization on secondary/bonded downstreams more physical layer related

• Adding upstream channels

– Avoids node splitting – Offers load balancing

• Limited by CMTS’s

– Major CMTS vendors are only “Bronze”

– Operators are deploying systems using same CMTS & CM vendors

» Cisco & Cisco, Motorola & Motorola, Arris & Arris

 Phase 2

– Bonding upstream channels

MSO - Phase 2 Rollouts

 Phase 2:

– Bonded upstreams

• Major CMTS vendors aren’t planning on production release of bonded upstream support until late CY 2009

– Capacity ramping up

– Deployment of DOCSIS 3.0 eMTAs for Voice service

 Tests covered by DOCSIS 3.0 solution

– Upstream and downstream data-layer performance

• Throughput, packet loss, etc

• 100+ MB/s symmetrical

– Breakdown bonded group performance

• Isolation of channel issues

DOCSIS 3.0 Hardware

quired

Testing during the Transition

 What and How can we

toast now?

Sorry – I meant “Test”

Analog Integrity is Still Paramount, Supplemented by QAM Measurements

 Majority of “digital” issues involve basic analog

maintenance of the RF plant

– Levels, including network tilt, must be optimized beginning at headend – Carrier-to-noise and Hum on analog – Managing Hum has been shown to

improve QAM carrier quality – MER on QAM channels

– BER and DQI for intermittent impairments

– Ingress and leakage management

“Back to the Basics” Troubleshooting

 Majority of problems are basic physical layer issues

 Do a visual inspection of cable, connectors and passives and replace as needed

 Check for proper grounding

 Tighten F-connectors per your company’s installation policy

– Be very careful not to over tighten connectors on CPE (TVs, VCRs, converters etc.) and crack or damage input RFI integrity

 Check forward and return RF levels, analog and digital

 Check for reverse ingress coming from home

 Most of the test strategy remains the same divide and conquer technique – bad here-good there-problem in between!

Generate Digital (modulate)

What is Digital?

 Source and Destination is digital data

– Assign unique patterns of 1’s and 0’s

 Transmission path is via an analog QAM carrier

– Choice of modulation is the one that optimizes bandwidth (data versus frequency ‘space’) and resiliency to noise

00 01 10 11 00 01 10 11

Receive Digital

(demodulate)

QAM Measurements

 Spectrum & Digital Average Power Level

 MER (Modulation Error Ratio)

 Pre/Post FEC BER (Bit Error Ratio)

 QAM Constellation Display

 QAM “Ingress Under The Carrier”

 QAM DQI (Digital Quality Index)

 AGC Stress

 Group Delay

 In-Channel Frequency Response

 Equalizer Stress

Hum

 Low frequency amplitude modulation (<1 kHz) of a carrier when passing through an active or passive component

 FCC states that Hum must be < 3%

 Caused By:

– Power Supply Filter Failure – Bad Solder Connections – Corroded Connectors

– Bad power supplies in amplifiers – Earth-loops on coax cables

– Bad connection to ground

Hum Modulation Characteristics

 Diagnosis - if hum caused by . . .

– 60 Hz Component - Check for bad ground connections – CAREFULLY!

– 120 Hz Component - Check DC Power Supply For Ripple (possible filter capacitor or diode failure)

• Can be customer equipment – old TV or VCR or radio ( remember them) power supply

 Effect on analog TV picture: one or two bars slowly scroll up the picture

 Effect on Digital picture: digital tiling in the picture

 Effect on DOCSIS^® data: packet loss/slow throughput

Hum Mode is Easy and Non-Intrusive

 Tune to analog video carrier, press HUM key

 Works on unscrambled analog video carriers only

 In-service Hum measurement does not interfere with picture

 Some meters have selectable 60Hz, 120Hz and <1,000Hz filters

 HUM measurements can be expressed in percentage or dB

AGC Stress

 Triggers alarm flag when meter AGC detects signal level change of > .5dB in 1 second of time.

 This small but rapid up and down change in level can cause problems with digital set tops boxes and CM’s.

 Single channel can be caused by a problem with the QAM modulator

 Flagging on multiple channels indicates a problem with the plant trunk/bridger AGC circuits

7 dB TAP

Drop Cable

High Pass Filter GROUND

BLOCK

DIGITAL SET-TOP

House

2-Way Amplifier

Testing the Home for Ingress Contribution

VoIP OLDER TV SET

Return Equalizer

WIRELESS LAPTOP

COMPUTOR

ETHERNET

Disconnect drop from tap and check for ingress coming from customer’s

home wiring

If ingress is detected, scan spectrum at ground

block for ingress

Electrical Devices

•Doorbell transformers

•Toaster Ovens

•Electric Blankets

•Ultrasonic pest controls (bug zappers)

•Fans

•Refrigerators

•Heating pads

•Light dimmers

•Touch controlled lamps

•Fluorescent lights

•Aquarium or waterbed heaters

•Furnace controls

•Computers and video games

•Neon signs

•Power company electrical equipment

•Alarm systems

•Electric fences

•Loose fuses

•Sewing machines

•Hair dryers

•Electric toys

•Calculators

•Cash registers

•Lightning arresters

•Electric drills, saws, grinders, and other power tools

•Air conditioners

There are Many Possible Sources of Interference

Off-Air Broadcast

•AM Radio Station

•FM Radio Station

•TV Station

•Two-way Radio Transmitters

•Citizens Band (CB)

•Amateur (Ham)

•Taxi

•Police

•Business

•Airport/Aircraft

•Paging Transmitters

FEDERAL

Typical Ingress Problem Areas

 Taps

– Most ingress comes from houses with tap values of 17 dB or less

 House Wiring

– Drop Cable & F Connectors contribute

approximately ~95% of system ingress problems

 Amplifiers, hard line cable and the rest of the system are a small percentage of the problem if a proper leakage maintenance program is performed.

“Reverse Spectrum” Install Test

 View return spectrum (5 to 42 MHz) and FM band (88 to 108 MHz)

 Select peak hold and wait for a few minutes

 Re-scan spectrum to confirm that you’ve fixed the ingress problem in the home

Return Path

Taps - Probe the Seizure Screws for Ingress & CPD

If the problem is at the FWD Input and not the FWD Output, then the problem is likely from one of the drops

If the problem is at the FWD Output of tap, continue on towards end of line

Forward Path

Probe the seizure screws for ingress

Taps are made up of a Directional Coupler and Splitters

Disconnect one drop at a time to determine the point of entry

-60 -50 -40 -30 -20 -10 0 10 20 30 40

Center: 25.000 M Hz Span: 40.000 M Hz

RBW: 300 KHz VBW: 100 KHz Dwell: 400 µS

In-Band Power 10.393 dBmV

-60 -50 -40 -30 -20 -10 0 10 20 30 40

Center: 25.000 M Hz Span: 40.000 MHz

RBW: 300 KHz VBW: 100 KHz Dwell: 400 µS

In-Band Power 8.632 dBmV

Seizure screw probe

Equalizer Stress

 Digital demodulation receivers utilize adaptive equalizers to negate the effects of signals arriving other than the desired signal.

 Signals can arrive ahead of or after the desired signal. In a cable system, the majority of signals are reflections

and micro-reflections that arrive after the desired signal.

 Cable modems and digital set top boxes must be able to handle pre and post signals at levels defined by DVB standards. If the equalizer is pushed beyond those limits, errors will occur.

 By using the Velocity of Propagation, the distance to the source of the reflection can sometimes be located. If the reflections occur before the next upstream amplifier, they are simply amplified and passed downstream thereby

eliminating the ability to perform fault detection based on reflection time.

 Equalizer stress is used more as a figure of merit for the

Equalizer Stress

Signal arriving about 2usec after desired carrier

Micro reflections

Fault here….

Causes energy to reflect back…..

BUT..it has to go thru

isolation of directional

coupler ….and tap loss

Will we see it at drop?

Level Fault After cable loss,

Coupler

isolation and tap loss

35dbmv Minor(15

dbRL)

(20)-(4)-(25)- (14)=(-23dBmv)

35dBmv Short/Open (35)-(4)-(25)-

A C B

14

Micro reflections

Fault here….

Causes energy to reflect back…..

B

But its easy to see at non- directional or resistive test points

In Channel Frequency Response

In-Channel Frequency response is amplitude ripple. This means that signals at one frequency are attenuated relative to signals at another frequency.

For downstream digital carriers DOCSIS 1.0 specifies a max ripple of 0.5dB in 6MHz. DOCSIS 1.1 has relaxed this specification to 3.0dB in 6MHz.

BER – yet again

 A 256QAM channel transmits at a symbol rate of 5M symbols per second

 Bit rate = 8 bits per symbol X 5M symbol per second =40M bits per second

 Error Incident = Bit rate X BER = Errors Per Second

Lets simplify Pre and Post FEC

 Imagine some ping pong balls

 How many balls can you play catch with…….

And not drop one?

BER and intermittent’s…..

 Even though digital services (and VoIP) work at MERs of 32, and pre BER of E-7…….THINK…

 If you found the cause of that less than normal MER….or improved BER from E-7 to E-8……

 Do you think that might have an impact on an intermittent issue?

 Lets imagine some ping-pong balls

Why fix -8 and -7 Pre-FEC BER?

 You decide to go Bungee Jumping

 BungJee Jumpee Co says they use 100% more bungee strands than your weight needs….for safety!

 You need 50 strands for your weight, so they tell you they will use 100.

 When they go to put the bungee on your leg you notice a lot of broken strands…when you point this out, they say..

 Not to worry….you only need 50, right?

ARE YOU JUMPING???

Dots are spread out showing error

Constellation – a few words

 Constellation is Graphic View of MER – But captures bursty impairments better

 A constellation displaying significant noise

 Dots are spread out indicating high noise and most likely significant errors

– An error occurs when a dot is plotted across a boundary and is placed in the wrong location

 Meter will not lock if too much noise present

Gain Compression

 If the outer dots are pulled into the center while the middle ones are not affected, the signal has gain compression

 Gain compression can be caused by IF and RF amplifiers and filters, up/down

converters, modulators, etc

Outer edges pulled in

Phase Noise

 Display appears to rotate at the extremes

 HE down/up converters can cause phase noise

 Random phase errors cause decreased transmission margin

 Caused by transmitter symbol clock jitter

 Bad LO in meter can cause phase noise Constellation

Rotation Rotation

Coherent Interference

 If the accumulation looks like a “donut”, the problem is coherent interference

– CTB, CSO, spurs and ingress

 Sometimes only a couple dots will be misplaced

– This is often laser clipping or sweep interference

– Remember I told you about sweep insertion points?

Circular

“donuts”

BUT…….

 Constellation still doesn’t tell the whole story

 Constellation is ‘Sampled’

– For each point ( Symbol ) plotted, there are 1000’s that are not.

– So transient intermittents can still be missed.

 DQI is a method of showing transients that BER/Consellation views can still miss

– Accesses I/Q data before the Constellation sampler

Index from 0 to 10 simplifies reading

Derived from Raw I-Q data

DQI responds faster and gives the tech extra margin versus traditional

Momentary events are easily seen in the historical graph

Digital Analysis Tools - DQI

Current Support of Phase 1:

Upstream Testing

 Most field meters can test upstream signal quality

– Range, Packet Loss, VoIP Check, Throughput

 PacketLoss and VoIP Check are powerful tools to troubleshoot upstream/downstream BER issues

 Upstream QAM generator used out of band with Headend analyzer

– Troubleshoot degraded node performance and find problems in plant.

So what will 3.0 test screens look like?

 Maybe something like this:

Thank you –

Randy Francis JDSU