DOCSIS 3.0 Rev.A00.

DOCSIS 3.0 Rev.A00

Agenda & Discussion Points
CATV Market Dynamics DOCSIS 3 Overview DOCSIS 3 Benefits Preparing for DOCSIS 3 What you need to test How VeEX can help you Troubleshooting Summary Essential Technical Terms DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Confidential & Proprietary Information of VeEX Inc.
Market Trends Media Convergence Source: Future services on HFC networks: 33th PIKE Conference, 14 October 2008, Zakopane, Poland DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

User Profiles & Applications
Digital Photos Gaming MP3 WMV DVD Blu-ray SDTV HDTV Mobile Video iPod Walkman You Tube VOD DVR/PVR Data & VoIP Home Networks Web 2.0 DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

CATV Operators Need DOCSIS 3.0!
Rev.A00 CATV Operators Need DOCSIS 3.0! Customer Demand IPTV, Netflix, Blockbuster, SIP Video, Gaming, You Tube (HD), Video Phone (HD) ... Competitor Offering FTTx, GPON, VDSL2, FiOS, Wireless Business Services T1/E1 solutions HD Video Conferencing IP Addresses needed IPv6 DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

CATV Operators Feeling Pressure
Competition is extremely active Telcos are deploying VDSL2, GPON, FIOS and FTTx (USA & Europe) Consumer’s have an insatiable demand for new services HDTV, VoD, PVR, interactive DTV etc To meet the growing challenge cable operators have to: Expand network capacity in cost effective and timely manner Evolutionary steps - incremental investments in current technology Revolutionary steps – need to decide if and when to implement a Next Generation HFC network DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

An Ongoing Battle for Customers
Verizon Beats Back Cable With YouTube Tilt April 27, 2010 Verizon Communications Inc. (NYSE: VZ) will soon use FiOS TV's ability to feed in thousands of YouTube videos as a key selling point in TV spots aimed at drawing cable and satellite TV subscribers to its completely fiber-fed platform. DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

DOCSIS Overview DOCSIS 3.0 Benefits
Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Rev.A00 DOCSIS Milestones DOCSIS 1.0 (1999) 1st products certified (CableLabs started project in 1996) Open standard for high-speed data over cable Modest security, Best-effort service DOCSIS 1.1 (2000) Quality-of-Service (QoS) service flows Baseline Privacy Interface (BPI+) Certificates Improved privacy & encryption process DOCSIS 2.0 (2002) Improved throughput & robustness on Upstream 64/128 QAM modulation & higher symbol rates with FEC Programmable interleaving to upstream channels DOCSIS 3.0 (2006) Channel bonding (4U/4D) for increased capacity IPv6 support Improved security (AES) DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Quick Overview Increased Downstream Throughput
Rev.A00 DOCSIS 3.0 Quick Overview Increased Downstream Throughput Bonded downstream channels 56Mbps (RAW) each, 222Mbps Total Increased Upstream bandwidth Bonded upstream channels, 5-85MHz 27Mbps (RAW) each, 122Mbps Total IPv6 Support IPV6 will allow for 3.4x1038 IP addresses Address shortcomings with NAT devices Backwards compatibility Existing DOCSIS 1.0, 1.1 and 2.0 systems CMTS qualification Bronze and silver certifications phased out with only full certification available now Modem certification Full certification (CableLabs & Euro CableLabs) Additional network security Early Authentication and Encryption (EAE) or AES 128bit encryption which is more secure DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

DOCSIS Throughput Compared
Rev.A00 DOCSIS Throughput Compared EuroDOCSIS Version Date Rates – Annex A Downstream Upstream 1.x ~ (50) Mb/s 10.29 (9) Mb/s 2.0 30.72 (27) Mb/s 3.0 (4 Channels) ~ (200+) Mb/s (108+) Mb/s 3.0 (8 Channels) ~ (400+) Mb/s Notes: Downstream bandwidths assuming QAM-256 modulation Upstream bandwidth assuming QAM-64 modulation Maximum synchronization speed and (Maximum usable speed) DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Channel Bonding
Additional Upstream and Downstream Channels “Bonded” together for higher aggregate speed and capacity Can be deployed incrementally 4D/4U = 150Mb/s downstream 120Mb/s upstream No upper limit to # of channels HFC sub-split effectively limits # upstream channels Existing DOCSIS modems share channels with no negative impact DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Signals What do we know? Physically the same as DOCSIS 2.0 signals Consist of multiple QAM signals bonded logically together Carry data of mutual relevance Bonded channels can be contiguous or non-contiguous: Contiguous - consist of frequency consecutive signals Non-contiguous - interspersed in the spectrum with other carriers MPEG-2 transport for downstream signals QAM transport for upstream signals DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Preparation Confidential & Proprietary Information of VeEX Inc.

Preparing for DOCSIS 3.0 RF Bandwidth Availability
Rev.A00 Preparing for DOCSIS 3.0 RF Bandwidth Availability Headend and Core Network Equipment Preparation Verify QAM64 Upstream Txmission Verify QAM256 Downstream Txmission DOCSIS 3.0 Modem Emulation IP/Ethernet Testing (Ping, FTP, RFC2544, Web) DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Obtaining the Required Bandwidth
DOCSIS 3.0 Rev.A00 Obtaining the Required Bandwidth DOCSIS 3.0 requires a minimum of 4 to16 downstream channels Use Switched Digital Video to reclaim bandwidth Launch Digital Simulcast and migrate selected analog channels Launch digital only systems Expand the plant to 860MHz or 1GHz Use unusable old analog broadcast channels Move test carriers to alternate frequencies CMs are able to receive 4 DS channels spread across a 60MHz window DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Frequency Spectrum Changes
DOCSIS 3.0 Rev.A00 Frequency Spectrum Changes Today 870MHz Soon 1GHz Reclaiming bandwidth: Switched Digital Video MPEG 4 video Analog Video Reclamation Higher order modulation Test requirements: Downstream expanding to 1GHz Bonded channels need verification Return Path filling up rapidly impacting traditional sweep and ingress test methods In-service testing where possible DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Upstream Expansion How much gain? Extension of the US band from 65 MHz to 85 MHz DOCSIS technology becoming available FM band is compromised Large network investment is required Extension of the US band beyond 85 MHz Not in current DOCSIS recommendations New upstream band 900 – 1000 MHz Adaptation of DOCSIS (RF up converter) Ingress noise issue “solved” 862 to 1000 GHz is considered as DS extension band Big investment in diplex filters and return amplifiers New upstream band above 1000 MHz Ingress noise issue solved Quality concern regarding passives and cables Investment in diplex filters and return amplifiers 250Mb/s 500Mb/s 1000Mb/s DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Expanding HFC Network Capacity
Operators have strong differences in opinion with regard to options: Solutions are typically driven by specific technical, geographical or local market factors A combination of solutions often determines the preferred option Source: Michiel Peters, TNO - Benelux Chapter SCTE , 15 September 2008, Amsterdam DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Plant Qualification & Test Methods

Typical DOCSIS Network

DOCSIS 3.0 Rev.A00 Plant Qualification Generate QAM signal in RP to verify attenuation, level, Tilt, MER and BER Frequency response, Group delay, Constellation and Adaptive equalization Check spectrum for ingress, noise, CPD and laser clipping Check for modems transmitting excessive levels due to high value taps Upstream Testing Forward Sweep (Sweepless), frequency response, amplifier tilt MER, CNR, Group Delay, Constellation, BER pre/post errors MPEG-2 Video Signal Analysis Downstream Testing Qualify the plant on a node by node basis Cable drops should be Tri or Quad shielded Check for leakage & improve thresholds (< 5uV/m is recommended) Use the “divide-and-conquer” technique to locate problems Avoid downstream/upstream frequencies near the band edges/roll off Avoid downstream/upstream frequencies susceptible to ingress/interference Useful Tips DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Upstream Test – Part 1 Setup Configure the Upstream Generator (USG): Frequency, level, modulation, bandwidth, and symbol rate Transmit the QAM-64 signal upstream to a CX180+, CX350 or CX380 located in the Headend or Hub. DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Upstream Test – Part 2 Basic At the Headend or Hub, check: Digital signal level (dBmV, dBµV) Modulation Error Ratio (MER) DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Upstream Test – Part 3 Spectrum At the Headend or Hub, check: Upstream spectrum (5-65MHz) for Ingress, CPD, and other interference Check below 5MHz and above 65MHz all the way to 200MHz if possible A QAM-64 signal requires a clean upstream path! DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Still Having Problems? Level and MER look OK? A Signal Level Meter (SLM) and Spectrum Analyzer are great application specific tools, but they can be limited in telling you everything you need to know about advanced digital signals Downstream and upstream (DOCSIS) signals can be impaired by other factors not easily viewed using conventional test methods Look for the “needle inside the QAM haystack” to figure out what is going on! DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Upstream Testing – Part 4
Advanced For the Upstream, you need to check: MER (equalized and un-equalized) Pre and Post FEC Frequency response (in-channel) Group delay (in-channel) Constellation diagram Adaptive equalizer results DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Downstream Testing – Part 5
Advanced For the Downstream, you need to check: Digital Power Level MER (equalized and un-equalized) Pre and Post FEC Frequency response (in-channel) Group delay (in-channel) Constellation diagram Adaptive equalizer results DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Downstream QAM Parameters
DOCSIS 3.0 Rev.A00 Downstream QAM Parameters Constellation MER 64-QAM: 27 dB min 256-QAM: 31 dB min BER Pre/Post FEC Pre/Post Errorred Seconds (PRES/POES) The number of seconds with at least one corrected codeword Severely Errorred Seconds The number of seconds with at least one uncorrectable codeword DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Impairments Thermal noise is a basic physical phenomenon which cannot be avoided Random voltage variation proportional to temperature, bandwidth and resistance. At room temperature, in 6 MHz bandwidth and 75 ohms circuit, the thermal noise is approximately -60dBmV. After amplification, the noise level can get much higher. All the other impairments are “human made”, they depend on the design, implementation and operation of all the elements in the signal chain It is convenient to group all impairments into 2 categories: Linear distortions and Non-linear distortions. DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

What Degrades MER? Transmitted phase noise & Low carrier-to-noise ratio Non-linear distortions (CTB, CSO, XMOD, CPD…) Linear distortions (micro-reflections, amplitude ripple, group delay) Severe impedance mismatches aka linear distortions Improperly aligned or defective amplifiers In-correct modulation profiles Incorrect signal levels In-channel ingress Data collisions Laser clipping DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

What MER is Acceptable? RMS error magnitude Average symbol magnitude
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 MER is expressed in dB derived as follows: RMS error magnitude Average symbol magnitude 10 log DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Downstream Performance
DOCSIS 3.0 Rev.A00 Downstream Performance Pre/Post FEC BER What the results are telling you: Level, MER and Constellation are OK Pre/Post FEC BER indicate a problem What to look for: Interference from a sweep transmitter Downstream laser clipping Up-converter problem in the Headend Loose connections or CPD DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Notes on FEC To have an accurate idea of the BER performance you need to know both pre and post FEC bit error rate Forward error correction (FEC) is a digital error checking system that sends redundant information with the payload so the receiver can repair corrupted data and eliminate the need to retransmit. By using the same Reed Solomon decoder at the receiving end, bit errors can be detected – these are called Pre-FEC errors Pre FEC BER is the error rate of the incoming signal prior to being corrected by the FEC circuitry - a minimum of 1x10-7 is expected, but FEC may be able to correct errors as high as 1x10-6. Post-FEC errors cause poor TV quality or DOCSIS data retransmission Post FEC Bit errors are not acceptable and should be corrected The FEC decoder needs a BER of >1x10-6 to operate properly Both Pre and Post FEC BER need to be verified in order to determine if the FEC circuitry is working to correct errors and if so how hard. DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

QAM – Constellation Diagram
DOCSIS 3.0 Rev.A00 QAM – Constellation Diagram Constellation Diagram Each box in the Constellation diagram contains one symbol QAM64: 6 bits per symbol, 64 boxes QAM256: 8 bits per symbol, 256 boxes Quadrant 4 Quadrant 1 Quadrant 3 Quadrant 2 DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Modulation Error Ratio
DOCSIS 3.0 Rev.A00 Modulation Error Ratio MER = 10log (avg symbol power/avg error power) Q I Q A large “cloud” of symbol points means low MER—this is not good! Average error power Average symbol power I Q A small “cloud” of symbol points means high MER—this is good! I Source: Hewlett-Packard DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Forward Path Modulation
DOCSIS 3.0 Rev.A00 Forward Path Modulation QAM 64 or QAM 256 are most commonly used Modulation Type Std. Symbol Rate (MHz) Max data rate (Mbps) Annex A (8MHz) QAM64 6.952 41.4 QAM256 55.2 (220 max 4 channel bonding) Annex B (6MHz) 5.057 38 5.361 43 (160 max 4 channel bonding) DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Return Path Modulation – DOCSIS
Rev.A00 Return Path Modulation – DOCSIS DOCSIS (Data-Over-Cable Service Interface Specifications) Reverse Path / Upstream Data Rate DOCSIS Bandwidth (MHz) Modulation type Max data rate (Mbps) 1.0 3.2 QPSK 5.12 1.1 QAM16 10.24 2.0 6.4 QAM64 30.72 3.0 QAM128 120 (4 channel bonding) Standard symbol rate (bandwidth): 1.28 (1.6), 2.56 (3.2), 5.12 (6.4) MHz DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Constellation Display
Learn to interpret the constellation display – it tells you a lot of the signal Symbol points should be small and well-defined DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

The Adaptive Equalizer
Every MPEG2 digital receiver has an Adaptive Equalizer The Equalizer typically cascades two digital filters: Feed Forward Equalizer (FFE) - reference tap is the last of 16 taps Decision Feedback Equalizer (DFE) - output is fed back to input, 108 taps long Compensates for Linear distortions (Amplitude imperfections & group delay) The Equalizer uses MER as a tool to adaptively cancel these Linear distortions DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Adaptive Equalizer Test Functions
Frequency Response & Group Delay Graphs Impairment Results Tap Expert DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Linear Distortions – a closer look (1)
DOCSIS 3.0 Rev.A00 Linear Distortions – a closer look (1) What the key measurements are telling you! Hum Low frequency disturbances of the digital carrier e.g. switching power supplies Phase Jitter Instability of the QAM carrier seen at the demodulator Phase changes of oscillators e.g. the up-converter Introduces a back and forth rotation of the constellation where some symbols will eventually cross the decision boundaries and cause an error in transmission EVM (Error Vector Magnitude) A measure of how far constellation points deviate from their ideal locations. Ratio of RMS Constellation Error Magnitude to peak Constellation symbol magnitude Symbol Rate Error Should be less than +/- 5pm DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

What the measurement is telling you! Frequency Response Frequency response of the digital carrier Micro-reflections can cause amplitude ripple in the frequency response Should be less than 3dB (peak-to-peak) Group Delay Different frequencies travel through the same medium at different speeds (see supporting slide) Worse near band edges and diplex filter roll-off areas Group Delay variation is usually expressed in ns for the Downstream and in “ns / MHz” for the Upstream Should be < 50ns peak-to-peak General Notes: Amplitude and Group Delay responses help visualize the effects of filters, diplexers, traps, suck-outs in the signal path, from (and including) the QAM modulator up to the point of test. The frequency span of the calculated responses is directly related to sampling period of the Equalizer Symbol period. For QAM-64, the span response is 5.05 MHz, while for QAM256 the span is 5.36 MHz DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

What the measurement is telling you! Echo Margin Echoes are micro-reflections The tallest vertical bar is the incident signal (reference tap) Smallest difference between any coefficient and the DOCSIS template defined by CableLabs Safety margin when getting too close to the “cliff effect” Should ideally be > 6dB Equalizer Stress Derived from all the Equalizer coefficients Indicates how hard the Equalizer is working to cancel out the Linear distortions Global indicator (the higher the figure, the less stress) Noise Margin Generally, the lower the MER, the larger the probability of errors in transmission (Pre-FEC and Post FEC) Amount of noise that can safely be added to degrade the Equalized MER before losing the signal (cliff effect) DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Rev.A00 Linear Distortions Micro-reflection at about 2.5 µs (2500 ns): Assume ~1 ns per ft., 2500/2 = 1250 ft (actual is 1.17 ns per ft: (2500/1.17)/2 = 1068 ft) Frequency response ripple ~400 kHz p-p: Distance to fault = 492 x (.87/.400) = 1070 ft. DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Rev.A00 Operational RF Levels DOCSIS recommends that the digitally modulated signal’s average power level be set 6 dB to 10 dB below what the visual carrier level of an analog TV channel on the same frequency would be This ratio should be maintained throughout the entire cable network DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 CM Emulation Link Up
Rev.A00 DOCSIS 3.0 CM Emulation Link Up Step-by-step CM link up process to clearly identify any failed steps After link up, power level on forward and return paths are measured. DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 CM – IP Tests (1) Complete server connection status indicates any IP problems Once the CM is on-line, a full range of IP tests including Ping test can be performed DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Rev.A00 DOCSIS 3.0 CM – IP Tests (2) Throughput (FTP) Download and Upload should be verified at the CM service location. Web Test and Web Browser provide bandwidth and visual indications of performance DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 CM – VoIP Tests (1)
VoIP Expert generates industry standard wave files to verify MOS and R-Factor of upstream and downstream and includes packet jitter, packet loss, and delay. Real-time of subjective voice quality evaluation (MOS and R-factor) using the Telchemy Algorithm and test method is provided DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 CM – VoIP Tests (2)
Detailed Packet statistics provide a complete insight to transport and IP layer impairments Jitter performance is checked using the Inter Packet Delay Variation (IPDV) method per RFC3393 recommendations DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 – Ethernet Tests (1)
Ethernet Testing is important to validate business services, E1 circuit emulation or Wireless backhaul applications (E1/T1/IP) Copper (10/100/1000BaseT) & Fiber (1000BaseX) based Ethernet service should be verified DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 – Ethernet Tests (2)
RFC2544, BERT, & Throughput test modes are used to test Ethernet circuits running at the subscriber premise or in the core network at Headend locations Advanced traffic generation and detailed analysis is used to check and benchmark all types of Ethernet service offered at customer locations. DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Pre-Qualification
Spectrum analysis (Upstream & Downstream) Bonded channel statistics (Upstream & Downstream) Constellation analysis (Upstream & Downstream) Equalizer measurements (Upstream & Downstream) Group delay and Frequency response (Upstream & Downstream) Cable Modem Emulation (Bonding, Encryption, BPI certificates, etc) IP & Ethernet Tests (Ping, Throughput, Web Browser, VoIP, RFC2544) DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

How Many Testers Do You Need?
DOCSIS 3.0 Rev.A00 How Many Testers Do You Need? Signal Level Meter DOCSIS 3.0 CM Analyzer QAM-64 USG Source Digital Spectrum Analyzer Group delay & frequency response tester Adaptive equalizer tester Ethernet Tester CX380 can do it all CX350 can do it all DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

RF Test Checklist Constellation display Pre / Post FEC BER
DOCSIS 3.0 Rev.A00 RF Test Checklist Constellation display Low MER or CNR Phase noise I-Q imbalance Coherent interference (ingress) Gain compression Laser clipping Sweep transmitter interference Pre / Post FEC BER Loose connections CPD Linear Distortions Adaptive equalizer graph In-channel frequency response In-channel group delay Constellation display Unequalized MER Unequalized Signal Level problems Analog channel signal level Digital channel power Upstream transmit level Transient Impairments Pre/Post-FEC BER Upstream packet loss Equalizer Graph Micro-reflections DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Rev.A00 Troubleshooting Integrated Up-converter Verify correct average power level Integrated up-converter RF output should be set in the DOCSIS-specified +50 to +61dBmV range Typical levels are +55 to +58dBmV Also check BER, MER and constellation DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Rev.A00 Troubleshooting External Up-converter Verify correct Power level, BER, MER and Constellation CMTS downstream IF output External up-converter IF input External up-converter RF output DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Combiner Output and Fiber Link
DOCSIS 3.0 Rev.A00 Combiner Output and Fiber Link Check signal levels and BER at downstream laser input and node output Bit errors present at downstream laser input but not at CMTS or up-converter output may indicate sweep transmitter interference, loose connections or combiner problems Bit errors at node output but not at laser input are most likely caused by downstream laser clipping DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Troubleshooting Tips DOCSIS 3.0 Rev.A00
Residential wireless networks may limit DOCSIS 3.0 performance benefits Routers, Switches, and Ethernet cards can limit bandwidth to 100Mbps or 10Mbps PC performance can effect or limit throughput Hardware settings can effect bandwidth e.g. MTU size Speed test servers can skew throughput results Ensure Test Equipment has sufficient bandwidth to perform high throughput test DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Essential Technical Terms to Remember

QAM Measurement Terms (1)
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. Phase Noise Jitter (changes in phase) of the oscillators, most likely the up-converter The phase shift or jitter should be < 0.5 degrees DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

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 < +/- 5ppm 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 > 6dB DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

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 < 50ns peak-to-peak Frequency Response Frequency response of the digital carrier Should be < 3dB peak-to-peak Carrier Offset Carrier frequency test. Should be no more than +/- 25KHz DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Group Delay - Return Path
5 MHz 5 MHz 5 MHz HFC (Filters, Taps) HFC (Filters, Taps) 10 MHz 10 MHz 10 MHz 15 MHz 15 MHz 15 MHz 20 MHz 20 MHz 20 MHz 25 MHz 25 MHz 25 MHz 30 MHz 30 MHz 30 MHz 35 MHz 35 MHz 35 MHz 40 MHz 40 MHz 40 MHz 45 MHz 45 MHz 45 MHz 50 MHz 50 MHz 50 MHz 55 MHz 55 MHz 55 MHz 60 MHz 60 MHz 60 MHz 65 MHz 65 MHz 65 MHz t DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Rev.A00 Linear Distortions In-Depth Understanding ECHO MARGIN The Coefficients of the Equalizer will also reveal the presence of an Echo, (a.k.a. micro-reflections). The Equalizer will cancel such an echo, and in doing so, the equalizer coefficient which corresponds to the delay of the echo will be much higher than the surrounding ones, “it sticks out of the grass”. The relative amplitude of this coefficient is an indication of the seriousness of the echo, and its position gives the delay of the echo, hence its roundtrip distance. The Echo Margin is the smallest difference between any coefficients and a template defined by Cablelabs, as a safety margin before getting too close to the “cliff effect”. It is normal to notice relatively high coefficients close to the Reference as this corresponds to the filters in the modulator / demodulator pair and to the shape of QAM signal. EQUALIZER STRESS The Equalizer Stress is derived from the Equalizer coefficients and indicate how much the Equalizer has to work to cancel the Linear distortions, it is a global indicator of Linear distortions. The higher the figure, the less stress. NOISE MARGIN We all know that the lower the MER, the larger the probabilities of errors in transmission (Pre-FEC and then Post-FEC); the MER degrades until errors are so numerous that adequate signal recovery is no more possible (cliff effect). As Noise is a major contributor to the MER, we define Noise Margin as the amount of noise that can be added to a signal (in other words, how much we can degrade MER) before get dangerously close to the cliff effect. Noise is chosen because on the one hand it is always present, and on the other hand it is mathematically tractable. Other impairments, such as an Interferer, are not easily factored into error probabilities. DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

DOCSIS 3.0 Rev.A00 Linear Distortions In-Depth Understanding EQUALIZED MER vs. UN-EQUALIZED MER The MER (Modulation Error Ratio) is the ratio of the QAM signal to Non-Linear distortions of the incoming QAM signal. The MER should have included the Linear distortions to indicate the health of the signal; but the QAM demodulator cannot operate properly without the Equalizer and the Equalizer uses the MER as a tool to adaptively cancel the Linear distortions. Consequently it is convenient to distinguish the MER (non-linear distortions only) from an Un-equalized MER (non-linear and linear distortions), the Un-equalized MER is calculated from the MER and Equalizer Stress. The Un-equalized MER is always worst than the MER. A small difference between the two indicates little Linear distortions, a large difference shows that there are strong Linear distortions. Even if the Linear distortions are cancelled by the Equalizer, we have to keep in mind that the Equalization is a dynamic process as it tracks Linear distortions by trial and error even after converging. The larger the Linear distortions the larger the tracking transients are, hence more probability of transmission error (pre-FEC or Post-FEC BER). PHASE JITTER Phase Jitter is caused by instability of the carrier of the QAM signal at the demodulator. This instability could be found at the QAM modulator and up-converter or in the QAM receiver (Local Oscillators used in frequency conversions). The phase jitter introduces a rotation of the constellation, where the symbols clusters elongate and get closer to the symbol’s boundary. Eventually some symbols will cross the boundary and cause an error in transmission. The QAM demodulator has a Phase lock loop to track phase variations of the carrier; it tracks easily long term drift as well as some short terms variations (up to 10 or 30 kHz) but it cannot track very fast variations above its loop response. So in a QAM demodulator, the wideband jitter is more damageable than short term jitter. DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc. Confidential & Proprietary Information of VeEX Inc.

Recommended Reading Hranac, R. “Digital Troubleshooting, Part 1” Communications Technology, June 2006 Hranac, R. “Troubleshooting Digitally Modulated Signals, Part 2” Communications Technology, July 2006 Hranac, R. “Linear Distortions, Part 1” Communications Technology, July 2005 Hranac, R. “Linear Distortions, Part 2” Communications Technology, August 2005 DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

Thank You. Any questions? DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

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