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DOCSIS 3.0 from a test and measurement point of view
Randy Francis
Cable Networks Division
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION2
The HFC Pipe is Huge!
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION3
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
100% backward compatible with DOCSIS 1.0/1.1/2.0
1 x 256QAM => “up to” ~40Mbps
1 x 64QAM => “up to” ~30Mbps
4923:2A1C:0DB8:04F3:AEB5:96F0:E08C:FFEC
DOCSIS® 3.0 Overview
4 x 256QAM => “up to” ~160 Mbps
4 x 64QAM => “up to” ~120 Mbps
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION4
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 ----------8 channel
+343.04 (+304) Mbit/s
+444.96 (+400) Mbit/s
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION5
Un-Bonded Upstream Data rates
Courtesy Motorola
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION6
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– Each provides its own performance capability - and is scalable.
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION7
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
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION8
Pre-Equalization tapsBetter 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)
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION9
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!
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION10
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– Increasing number of DOCSIS 3.0 users on bonded channels
• Higher capacity utilization and concerns
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION11
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
Required
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION12
Testing during the Transition
What and How can we toast now?
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION13
Sorry – I meant “Test”
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION14
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
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION15
“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!
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION16
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 Analog Carrier
(“QAM Haystack”)
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION17
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
– Items in red are really ANALOG impairments measured on a QAM channel
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION18
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– Earth-loops in headend, interfering with the TV modulators
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION19
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
Effect on VoIP data: packet loss/robotized voice
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION20
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
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION21
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
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION22
eMTA-CABLE MODEM
7 dB TAP
Drop Cable
High Pass Filter
GROUND BLOCK
3-WaySplitter
DIGITAL SET-TOP
House
2-Way Amplifier
Testing the Home for Ingress Contribution
VoIP
OLDER TV SET
Return Equalizer
ONLINE GAMING
WIRELESS LAPTOP
COMPUTOR
ETHERNET
Disconnect drop from tap and check for ingress
coming from customer’s home wiring
INGRESS SPECTRUM MEASUREMENTS
If ingress is detected, scan spectrum at ground
block for ingress
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION23
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 •TV/radio booster amplifiers •TV sets •Automobile ignition noise •Sun lamps •Smoke detectors
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
FEDERALCOMMUNICATIONS
COMMISSION
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION24
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.
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION25
“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
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION26
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 dropsIf the problem is at
the FWD Output of tap, continue on towards end of line
Forward Path
Disconnect one drop at a time to determine the point of entry
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION27
4 Port Tap
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 MHzSpan: 40.000 MHzRBW: 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 MHzSpan: 40.000 MHzRBW: 300 KHz VBW: 100 KHz Dwell: 400 µS
In-Band Power 8.632 dBmV
Seizure screw probe
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION28
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 margin available to the set top box or cable modem.
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION29
Equalizer Stress
Signal arriving about 2usec after desired carrier
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION30
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 (0 RL)
(35)-(4)-(25)-(14)=(-8 dBmv)
A
BC
14
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION31
Micro reflections
Fault here….
Causes energy to reflect back…..
B
But its easy to see at non-directional or resistive test points
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION32
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.
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION33
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 SecondBER Error Frequency Error Incident 10-12 1 in 1 Trillion bits 25000 secs between errs (6.94 hrs) 10-11 1 in 100 Billion bits 2500 secs between errs (41.67 mins) 10-10 1 in 10 Billion bits 250 secs between errs (4.167 mins) 10-9 1 in 1 Billion bits 25 seconds between errors 10-8 1 in 100 Million bits 2.5 seconds between errors 10-7 1 in 10 Million bits 4 errors per second 10-6 1 in 1 Million bits 40 errors per second 10-5 1 in 100 Thousand bits 400 errors per second 10-4 1 in 10 Thousand Bits 4000 errors per second 10-3 1 in 1 Thousand bits 40000 errors per second
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION34
Lets simplify Pre and Post FEC
Imagine some ping pong balls How many balls can you play catch with…….
And not drop one?
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION35
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
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION36
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???
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION37
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
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION38
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
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION39
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
Constellation with Phase Noise Zoomed Constellation with Phase Noise
RotationRotation
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION40
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”
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION41
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
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION42
Index from 0 to 10 simplifies readingDerived from Raw I-Q data
DQI responds faster and gives the tech extra margin versus traditional measurements
Momentary events are easily seen in the historical graph
Digital Analysis Tools - DQI
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION43
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.
Isolate Packet Loss issues on the RF Plant from the IP Plant. Goal is to have 0% pkt loss Pkt loss on CMTS loop is often due to return path issues
© 2009 JDSU. All rights reserved. JDSU CONFIDENTIAL & PROPRIETARY INFORMATION44
So what will 3.0 test screens look like?
Maybe something like this:
Thank you –
Randy Francis
JDSU