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DOCSIS 3.0

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. Market Trends. Media Convergence.

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DOCSIS 3.0

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  1. DOCSIS 3.0 Rev.A00

  2. 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 Confidential & Proprietary Information of VeEX Inc.

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

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

  5. CATV Operators Need DOCSIS 3.0! Confidential & Proprietary Information of VeEX Inc.

  6. 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 Confidential & Proprietary Information of VeEX Inc.

  7. 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. Confidential & Proprietary Information of VeEX Inc.

  8. DOCSIS OverviewDOCSIS 3.0 Benefits Confidential & Proprietary Information of VeEX Inc.

  9. DOCSIS Milestones Confidential & Proprietary Information of VeEX Inc.

  10. DOCSIS 3.0 Quick Overview Confidential & Proprietary Information of VeEX Inc.

  11. DOCSIS Throughput Compared • Notes: • Downstream bandwidths assuming QAM-256 modulation • Upstream bandwidth assuming QAM-64 modulation • Maximum synchronization speed and (Maximum usable speed) Confidential & Proprietary Information of VeEX Inc.

  12. DOCSIS 3.0 Channel Bonding Confidential & Proprietary Information of VeEX Inc.

  13. 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 Confidential & Proprietary Information of VeEX Inc.

  14. DOCSIS 3.0 Preparation Confidential & Proprietary Information of VeEX Inc.

  15. Preparing for DOCSIS 3.0 Confidential & Proprietary Information of VeEX Inc.

  16. Obtaining the Required Bandwidth Confidential & Proprietary Information of VeEX Inc.

  17. Frequency Spectrum Changes Today 870MHz Soon 1GHz Confidential & Proprietary Information of VeEX Inc.

  18. Upstream Expansion How much gain? 250Mb/s 500Mb/s 1000Mb/s Confidential & Proprietary Information of VeEX Inc.

  19. 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 Confidential & Proprietary Information of VeEX Inc.

  20. DOCSIS 3.0Plant Qualification & Test Methods Confidential & Proprietary Information of VeEX Inc.

  21. Typical DOCSIS Network Confidential & Proprietary Information of VeEX Inc.

  22. Plant Qualification Confidential & Proprietary Information of VeEX Inc.

  23. 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. Confidential & Proprietary Information of VeEX Inc.

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

  25. 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! Confidential & Proprietary Information of VeEX Inc.

  26. 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! Confidential & Proprietary Information of VeEX Inc.

  27. Upstream Testing – Part4 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 Confidential & Proprietary Information of VeEX Inc.

  28. 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 Confidential & Proprietary Information of VeEX Inc.

  29. Downstream QAM Parameters Constellation MER 64-QAM: 27 dB min 256-QAM: 31 dB min BER Pre/PostFEC • 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 Confidential & Proprietary Information of VeEX Inc.

  30. 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. Confidential & Proprietary Information of VeEX Inc.

  31. 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 Confidential & Proprietary Information of VeEX Inc.

  32. What MER is Acceptable? • 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 Confidential & Proprietary Information of VeEX Inc.

  33. 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 Confidential & Proprietary Information of VeEX Inc.

  34. 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. Confidential & Proprietary Information of VeEX Inc.

  35. QAM – Constellation Diagram Constellation Diagram Quadrant 4 Quadrant 1 Quadrant 3 Quadrant 2 Confidential & Proprietary Information of VeEX Inc.

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

  37. Forward Path Modulation QAM 64 or QAM 256 are most commonly used Confidential & Proprietary Information of VeEX Inc.

  38. Return Path Modulation – DOCSIS DOCSIS (Data-Over-Cable Service Interface Specifications) Reverse Path / Upstream Data Rate Standard symbol rate (bandwidth): 1.28 (1.6), 2.56 (3.2), 5.12 (6.4) MHz Confidential & Proprietary Information of VeEX Inc.

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

  40. 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 Confidential & Proprietary Information of VeEX Inc.

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

  42. 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 Confidential & Proprietary Information of VeEX Inc.

  43. Linear Distortions – a closer look (2) • 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 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 Confidential & Proprietary Information of VeEX Inc.

  44. Linear Distortions – a closer look (3) 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” • Shouldideally 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) Confidential & Proprietary Information of VeEX Inc.

  45. 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. Confidential & Proprietary Information of VeEX Inc.

  46. 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 Confidential & Proprietary Information of VeEX Inc.

  47. 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. Confidential & Proprietary Information of VeEX Inc.

  48. 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 Confidential & Proprietary Information of VeEX Inc.

  49. 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 Confidential & Proprietary Information of VeEX Inc.

  50. 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 Confidential & Proprietary Information of VeEX Inc.

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