DOCSIS 3.0 Testing & Troubleshooting

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Testing & Troubleshooting of new DOCSIS 3.0 Cable TV systems including the benefits of better bandwidth utilization and


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Slide 1: 

Testing and Troubleshooting


DOCSIS is the standard for data over cable Data Over Cable Service Interface Specification Cable systems provide higher signal-to-noise ratios than over-the-air transmission A well designed and maintained cable plant is required to meet DOCSIS specifications DOCSIS


16 QAM is part of the DOCSIS 1.0/1.1 upstream specifications 64 QAM is part of the DOCSIS 2.0 upstream specifications 64 QAM and 256 QAM are both used for digital video and DOCSIS downstream, allowing more digital data transmission using the same 6 MHz bandwidth Transmit equivalent of 6 to 10 (SD) analog channels or 2 to 3 (HD streams) over one 6 MHz bandwidth channel DOCSIS


1.0 (high-speed internet access) DOCSIS 1.1 (voice, gaming, streaming) Interoperable and backwards-compatible with DOCSIS 1.0 “QoS” and dynamic services, a MUST for PacketCable™ DOCSIS 2.0 (capacity for symmetric services) Interoperable and backwards compatible with DOCSIS 1.x More upstream capacity than DOCSIS 1.0 (x6) & DOCSIS 1.1 (x3) Improved robustness against interference (A-TDMA and S-CDMA) DOCSIS 3.0 (channel bonding) Interoperable and backwards-compatible with DOCSIS 1.x and 2.0 DOCSIS

DOCSIS 3.0 : 

Higher data rates Channel bonding More subscribers per channel Statistical multiplexing from channel bonding Better bandwidth utilization Source specific multicast Multicast header suppression High-quality IP video Multicast quality of service DOCSIS 3.0

DOCSIS 3.0 : 

More IP addresses when you need them IPv4 and IPv6 support Enhanced security 128 bit AES encryption (advanced encryption standard) Increased cable modem provisioning process security DOCSIS 3.0

DOCSIS 3.0 : 

Option to increase upstream bandwidth Option for 5 to 85 MHz upstream support Powerful reporting to manage traffic Cable modem diagnostic log IP detail record (IPDR) streaming protocol DOCSIS 3.0

Higher Data Rates : 

Channel bonding: Using multiple upstream and/or downstream channels to get a larger logical channel MSO can choose to bond any number of channels Channels do not have to be adjacent; but must be within 60 MHz Individual channels support legacy cable modems Full backward compatibility Minimum “CableLabs” requirement of 4 upstream and 4 downstream bonded channels Allows tiers of high speed data services Enables business services Higher Data Rates

Higher Data Rates : 

Upstream capacity with 6.4 MHz and 64 QAM Two channels, 60 Mbps Three channels, 90 Mbps Four channels, 120 Mbps Downstream capacity with 6 MHz and 256 QAM Two channels, 80 Mbps Three channels, 120 Mbps Four channels, 160 Mbps Eight channels, 320 Mbps Higher Data Rates

More Subscribers Per Channel : 

Subscriber gain of approximately 10% to 25% more customers per channel due to statistical multiplexing from channel bonding Multiple channels More opportunity for traffic to get through More subscribers per channel More Subscribers Per Channel

Better Bandwidth Utilization : 

Source specific multicast Multimedia (audio/video) services delivered from one specific source to multiple subscribers’ CPE devices Enables operators to offer broadcast-like services over DOCSIS network-based on subscriber demand (e.g. IPTV service) Enables bandwidth efficient on-demand multimedia services as compared with unicast Better Bandwidth Utilization

Better Bandwidth Utilization : 

Multicast header suppression Ability to remove repetitive portions of headers on multicast frames Provides bandwidth savings for bandwidth intensive multicast services such as IPTV (Internet protocol television) Enables MSOs to transmit more multicast sessions for a given amount of downstream channel spectrum Better Bandwidth Utilization

High-Quality IP Video : 

Multicast quality of service Provides guaranteed bandwidth for multicast sessions, enabling: Entertainment quality video services to MSO customers Differentiation of QoS-enabled multicast services Service level guarantees to be offered to the end customer High-Quality IP Video

More IP Addresses : 

Support for both IPv4 and IPv6 MSO decides when to convert network to use IPv6 A DOCSIS 3.0 cable modem first looks for an IPv6 address, Then will look for an IPv4 address More IP Addresses

More IP Addresses : 

Support for both IPv4 and IPv6 (continued) IPv6 address can be assigned to customer devices Allows MSO to rollout new IP based services that would not be possible due to the lack of IPv4 address space 340,282,366,920,938,463,463,374,607,431,768,211,456 = 340 trillion trillion trillion unique addresses More IP Addresses

IPv6 : 

Expands IP address size from 32 bits to 128 bits Colon-hexadecimal Thus IPv6 addresses are much longer than traditional IPv4 addresses Example of an IPv6 address: 2001:0bd8:fedc:5a19:7312:0030:654e Contrast this to an IPv4 address such as Over the coming years the Internet will gradually move over to IPv6 With a transition period in which both IPv4 and IPv6 are in use IPv6

Enhanced Security : 

128 bit advanced encryption standard (AES) Provides stronger traffic encryption for users’ data Maintains privacy of customer traffic Meets the US Government requirements for enhanced security of data traffic Enhanced Security

Enhanced Security : 

Increased cable modem provisioning process security Reduces operational complexity while enhancing network security Reduces denial of service attacks on MSO operations support systems Prevents hacked modems from requesting unauthorized services Facilitates sharing certificate revocation data from one MSO to another Enhanced Security

Option to Increase Upstream Bandwidth : 

Optional 5 to 85 MHz upstream support Upstream operation can be extended from 5 to 42 MHz up to 5 to 85 MHz Adds nearly 200 Mbps of potential capacity New DS/US symmetry ratio enables business services Requires fiber node and amplifier upgrades Option to Increase Upstream Bandwidth

Option to Increase Upstream Bandwidth : 

Option to Increase Upstream Bandwidth

Powerful Reporting to Manage Traffic : 

Cable modem diagnostic log CMTS monitoring of cable modems with unstable operations Repeated initialization Station maintenance retries Includes functionality commonly referred to as a “flap list” Enables adoption of common mechanisms for: Troubleshooting cable modem connectivity Proactive maintenance Powerful Reporting to Manage Traffic

Powerful Reporting to Manage Traffic : 

IPDR streaming protocol (internet protocol detail record) Selected to replace SNMP for bulk data collection from CMTS Allows efficient collection of statistics from the CMTS Powerful Reporting to Manage Traffic

Enhanced Tools : 

Additional physical layer measurements from the CMTS Enables operators to meet the higher capacity and reliability requirements for business services Enhanced Tools

DOCSIS 3.0 Summary : 

More speed More revenue per channel Guarantees on video quality (QoS) Transition to IPv6 when ready Option to increase upstream bandwidth DOCSIS 3.0 Summary

Channel Bonding : 

Channel Bonding Example:

DOCSIS 3.0 Certification/Qualification : 

Three levels of DOCSIS 3.0 CMTS submission to CableLabs: Bronze Includes downstream channel bonding and IPv4/IPv6 management of cable modems Silver Includes Bronze plus upstream channel bonding, AES, bonded multicast, and IPDR streaming protocol Full Full DOCSIS 3.0 compliance DOCSIS 3.0 Certification/Qualification

Channel Bonding Standards : 

Three channel bonding standards: Bronze At least 4 bonded downstream channels (160 Mbps and up) 1 upstream channel (Up to 30 Mbps)* Silver At least 4 bonded downstream channels (160 Mbps and up) At least 4 bonded upstream channels (120 Mbps and up)* Full All the above, plus: Enhanced network management Enhanced IP multicast *64 QAM Channel Bonding Standards

Primary Channels : 

One channel in the group carries timing info for whole group Each channel in the group carries its own timing information Primary Channels

DOCSIS 3.0 Checklist : 

Plant qualification Head-end RF alignment Downstream 256 QAM testing and qualification Upstream 64 QAM testing and qualification Avoid frequencies near the roll-off or band edges Avoid frequencies susceptible to ingress, if possible Control ingress, noise, CPD, and laser clipping Tighten RF leakage thresholds DOCSIS 3.0 Checklist

DOCSIS 3.0 Checklist : 

Test equipment DOCSIS 3.0 field test meter 64 QAM signal source? Upgrade or purchase new QAM analyzers DOCSIS 3.0 Checklist

DOCSIS 3.0 Checklist : 

Preventive maintenance Do complete system sweep every 12 to 18 months (all actives) End-of-line digital testing (MER and BER) Leakage testing Return path monitoring Daily reports (use as historical references) DOCSIS 3.0 Checklist

Data Management : 

Application software enables interactive analysis of measurement data QAM measurement data can be logged Tied to work order Uploaded to management server via web link Data Management

Data Management Software : 

Trilithic Data Manager (TDM) server Technical record storage and review Installation certification Technician compliance analysis Statistical analysis of “troubled” service areas Employs connection to billing software Data Management Software

Auto-Test Macros : 

Efficient, error-free testing DOCSIS 3.0 environment macro includes: Channels in a group Set of tests to be performed on each channel Performance limits to analyze test result Auto-Test Macros

Typical Macro for D3 Tests : 

Once the macros are built and loaded into the meter: Technician pushes one button and runs specific tests on specified channels Immediately alerts technician to failures Typical Macro for D3 Tests

Typical Macro for D3 Tests : 

Technician can then retrieve and view supporting test details, or save files for uploading to server Typical Macro for D3 Tests

Typical Macro for D3 Tests : 

Results may be retained, displayed in supporting software Typical Macro for D3 Tests

D3 Auto-Test Results : 

D3 Auto-Test Results

D3 Auto-Test Results : 

D3 Auto-Test Results

D3 Auto-Test Results : 

D3 Auto-Test Results

The Field Analyzer and D3 Tests : 

Additional tests, such as VoIP analysis and CM statistics can be run on any channels in the bonded group that have been configured as “primaries” The Field Analyzer and D3 Tests

D2 Meters: What They can do Now : 

Full physical tests, analog, digital VoIP, HSD test suites Automatic data analysis: “health check” Data upload/download to data management server D2 Meters: What They can do Now

Identical Physical Tests for D2 and D3 : 

Identical Physical Tests for D2 and D3 Signal level scan Spectrum analysis QAM EVS (error vector spectrum) TraffiControl Upstream QAM source QAM level Constellation MER BER iBER – Long-term BER

Additional Tests on “Primary” Channels : 

Additional Tests on “Primary” Channels VoIP Cable modem statistics Ping Trace route High-speed throughput (40 Mbps per primary channel)

Monitoring : 

Return path maintenance system Retain high transient capture speed, reverse sweep and installation support DOCSIS 3.0 No impulse noise bursts ≥10µS Monitoring

Advantages of DSP : 

Provides the fastest method of measuring return path ingress levels Increased flexibility in measurement and testing applications View “in channel” ingress on active carriers in Traffic mode Advantages of DSP

Monitoring : 

Monitoring Troubleshooting of active return carriers DSP technology allows “virtual removal” of live system return carriers Via Traffic mode Traffic mode may be transmitted to field units to localize and troubleshoot in-band interference

Monitoring : 

Monitoring Reduces service interruptions Faster alarm notification Simplified troubleshooting Accurate representation of return path spectrum Certification Reporting

Alarm Troubleshooting : 

To investigate alarm conditions RNOC operators can click on alarm events in the incident log Brings up Spectrum view with: Alarm threshold and ingress signature that caused the alarm event Evaluate the effect of ingress on system services Alarm Troubleshooting

Alarm Troubleshooting : 

Spectrum markers Allows RNOC operators to identify frequency and level on points of interest within the ingress signature 2 markers to perform measurements on any ingress CPD HAM CB Alarm Troubleshooting

Alarm History Folder : 

Stores changes in alarm state Recall past alarm events Correlate alarm events with service interruptions Identify ingress signature for troubleshooting Alarm History Folder

Reporting : 

Node service report Returns alarm activity over user specified time periods and locations Provides correlation of service interruptions and return path ingress events Identifies and prioritizes nodes in need of maintenance Selection criteria Alarm severity Number of nodes per location Reporting

Node Service Report : 

Node alarm detail list Alarm count by date Quick correlation between events and service interruptions Spectral information maybe obtained from node incident log Node Service Report

DOCSIS 3.0 and RPM : 

DOCSIS 3.0 and RPM Issue: Return band frequency extension CableLabs specification: 5 to 85 MHz Number of bonded upstream channels drives extension: 1 upstream (bronze): No extension 4+ upstream: Possible extension 8+ upstream: Needs extension

DOCSIS 3.0 and RPM : 

Downside for systems considering extension: May require replacement of all actives in distribution chain (diplex filters): Nodes Line amps (partial or total) For subs adopting DOCSIS 3 services: New modems Two-way drop amps Upgrade or purchase new monitoring equipment DOCSIS 3.0 and RPM

Troubleshooting : 


Cable Network : 

Transmission of digital information over HFC networks is via a QAM carrier The QAM channels consists of broadcast video, VOD, or DOCSIS The US follows ITU Annex B which is 6 MHz wide and normally 256 QAM with error correction algorithms (FEC) Most transmission of digital video is via a QAM modulator called an edge QAM and DOCSIS via a CMTS Cable Network

Channel Configuration : 

Configure the QAM analyzer channel plan Prepares instrument for measurements Can be done quickly with application support software WorkBench software TDM integrated server package Channel Configuration

Edit QAM Channel Parameters : 

Channel details Bandwidth Symbol rate Inclusion of channel in auto test macros Edit QAM Channel Parameters

QAM Signal Average Power : 

Level measurement Typical levels: 64 QAM 6 dB below analog carriers 256 QAM 10 dB below analog carriers QAM Signal Average Power

Scan : 

Scan shows level response with one channel level reading Note: Total power reading at the bottom of the graph Scan

How to Troubleshoot : 

A signal level meter will only show so much detail How to Troubleshoot

QAM Analyzer : 

A signal level meter is valuable tool, but it does not tell everything about digitally modulated signals QAM analyzers support numerous measurements Level Analog Digital channel average power Constellation MER Pre- and post-BER QAM Analyzer

QAM Analyzer – Additional Measurements : 

QAM Analyzer – Additional Measurements QAM source QAM EVS Track down in-channel ingress in the downstream Traffic mode Track down ingress under a modem or VoIP carrier in the upstream VoIP Throughput Ping Trace route CM-stat

DSP QAM Analyzer (Block Diagram) : 

DSP QAM Analyzer (Block Diagram)

QAM Analyzer : 

MER 64 QAM 27 dB min 256 QAM 31 dB min Typical problems: Laser clipping, sweep interference, loose connection, or a up-converter problem in the head-end Note: BER 1.0E-10 Good QAM Analyzer Note: Pre BER 3.00E-05 Bad

Constellation Display : 

How it is derived Will help to understand QAM modulation How the digital signal is transmitted The Constellation display a valuable tool for determining the health of a digital signal Constellation Display

Quadrature Modulation : 

Quadrature modulation – method of amplitude modulation that allows two channels to be carried at the same frequency, effectively doubling the bandwidth that can be carried A form of quadrature modulation has been used for many years in analog television to carry the two components of the color subcarrier By modulating two carriers at exactly the same frequency but shifted by 90°, both the amplitude and phase of the carrier is modulated Quadrature Modulation

Quadrature Modulation : 

Carrier phase shift Carrier amplitude Quadrature Modulation I channel carrier phase Q channel carrier phase 90° shifted I channel + Q channel = carrier amplitude

Quadrature Modulation : 

The phase and amplitude of the carrier at any given time determine the location on the Constellation and the I and Q channels can be derived from this information Quadrature Modulation

Constellation : 

The location on the Constellation determines the I and Q components amplitude The amplitude of the I and Q channels are derived from the rectangular coordinates of the carriers amplitude and phase Constellation

Gray Coding : 

The symbol which each location on the constellation represents is chosen using a technique known as gray coding Ensures that any adjacent location will only be one bit different, reducing the effect of an error Gray Coding

64 and 256 QAM Constellations : 

By adding more levels to the I and Q channels, higher data rates can be carried The higher the number of levels, the more effect there will be from noise or interference 64 QAM uses 8 levels in the I direction and 8 levels in the Q direction for a total of 8 squared or 64 symbols 256 QAM uses 16 levels in the I direction and 16 levels in the Q direction for a total of 16 squared or 256 symbols 64 and 256 QAM Constellations

64 QAM Constellation : 

I Amplitude Q Amplitude 64 QAM Constellation 64 possible combinations of I and Q

256 QAM Constellation : 

256 QAM Constellation I Amplitude Q Amplitude 256 possible combinations of I and Q

Decision Boundaries : 

Each location on the constellation is framed by decision boundaries If the signal falls within these boundaries, the correct data will be received If falls in an adjacent area, the data will be in error Decision Boundaries

Constellation Buildup : 

The locations on the constellation build up over time and the shape and distribution can tell you much about the health of the signal and any problems that it has Constellation Buildup

Clean Constellation Display : 

Example of a good 64 QAM constellation Dots are well defined and positioned and away from the decision boundaries indicating good: Gain Phase noise Modulation error ratio (MER) Clean Constellation Display

Gain Compression : 

The outer dots are drawn into the center while the middle ones are not affected Amplifier input level too high Gain Compression

System Noise : 

Constellation displaying significant noise System Noise

Phase Noise : 

Constellation rotates at the extremes A defective modulator or processor can add appreciable phase noise to the signal, resulting in a constellation that appears to have “rotated” around the center of the graph Phase Noise

Coherent Interference : 

The dots accumulate and look like a circle or “donut,” the problem is coherent interference CTB, CSO, spurs, laser clipping and ingress Coherent Interference

IQ Imbalance : 

I IQ Imbalance Q The constellation is taller than it is wide Difference in gain I channel Q channel I-Q imbalance Baseband amplifiers Filters Digital modulator

Constellation Display : 

Understanding the constellation display will go a long way towards helping you understand QAM modulation problems Constellation Display

QAM Mode – BER : 

The BER display shows a graph of errors over time This is a valuable troubleshooting tool QAM Mode – BER

Impulse BER : 

BER Corrupted bits/total bits received Shows BER before and after FEC Errored seconds The number of seconds with at least one corrected code word Impulse BER

Impulse BER (continued) : 

Severely errored seconds The number of seconds with at least one uncorrectable code word Valuable troubleshooting tool Whenever there are errors use this screen to divide and conquer Impulse BER (continued)

Linear Distortions : 

Good Bad Linear Distortions

Linear Distortions : 

Linear Distortions QAM analyzers incorporate an adaptive equalizer graph, also called “equalizer stress” Ideal for troubleshooting micro-reflections Vertical axis is in decibels Horizontal axis shows time Typically related to the QAM analyzer’s adaptive equalizer tap spacing

Linear Distortions : 

Linear Distortions Most QAM analyzers calculate the distance


QAM EVS Troubleshooting in-channel ingress is easy with the QAM EVS mode Typical ingress areas: Loose connector Tap plate loose Home wiring


QAM EVS Other possible ingress areas: CSO/CTB from an over driven house amp Sweep Make sure the sweep transmitter is properly setup

Traffic Mode : 

Traffic mode can be used to see the ingress that is present “underneath” an upstream cable modem carrier, VoIP carrier, or any bursty signal Troubleshooting made easy Divide and conquer Source typically a home Traffic Mode

QAM Source : 

Upstream QAM source verifies the transmission capability of the network for higher order QAM signals QPSK 16 QAM 64 QAM Adjustable: Symbol rate Level Frequency QAM Source

Upstream Performance : 

VoIP service the upstream packet loss should not exceed 0.1% to 0.5% Upstream Performance

Ping Test : 

Continuous ping Packet loss, latency and jitter Favorite addresses to ping Modem statistics Ping Test

Trace Route : 

Sometimes it’s helpful to run a Trace Route from the subscriber’s PC This will show the routing point where the transmission stops Some devices can be configured not to respond to ping, as a security measure Firewalls, for instance Trace Route

Throughput Test : 

Throughput rates up to 40 Mbps Select test at fixed throughput rates, such as 5, 10, 15, 30, and 40 Mbps to test various tiered services Test at both the desired speed and one speed higher to prove that the cable modem is provisioned correctly Throughput Test

VoIP RTP Test : 

Proprietary test call to server Upstream and downstream latency, jitter and MOS Drill down for details, upstream and downstream VoIP RTP Test

CMTS with Integrated Upconverter : 

Verify level, BER, and MER RF output should be in the 50 to 61 dBmV range Typical levels are 55 to 58 dBmV CMTS with Integrated Upconverter

CMTS with External Upconverter : 

Verify level, BER, and MER CMTS IF output Upconverter IF input Upconverter RF output CMTS with External Upconverter

Combiner Output and Fiber Link : 

Combiner Output and Fiber Link Check signal levels and BER at downstream laser input and node input BER problems at laser input But not at CTMS BER problems at node output But not at laser input are most likely laser clipping

Node and Premise : 

Node and Premise Measure RF levels and MER and BER levels for impairment Additional test features of the QAM analyzer: QAM EVS Traffic mode VoIP Ping Trace Route Throughput CM-stat Divide and conquer

Troubleshooting Summary : 

Troubleshooting Summary Constellation display Low MER or CNR Phase noise I-Q imbalance Coherent interference (ingress, beats) Gain compression Laser clipping Sweep transmitter interference Pre- and post-FEC BER Sweep transmitter interference Laser clipping Loose connections Low MER or CNR Equalizer graph Micro-reflections

Troubleshooting Summary : 

Troubleshooting Summary Testing modes QAM source QAM EVS Traffic mode VoIP Throughput Ping Trace Route CM-stat Transient impairments Pre- and post-BER Constellation display zoom function Upstream packet loss Signal level problems Analog signal level Digital channel power Upstream transmit level Constellation display

Slide 106: 

Questions? ? This concludes the Testing and Troubleshooting presentation.

Contact Information : 

Contact Information Sales and Applications Support (800) 344-2412 Support forum: Support email: Website:

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