anga 2013 v2
DESCRIPTION
DOCSIS & Testing Best Practices in an All Digital NetworkTRANSCRIPT
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Brady Volpe
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Massive Traffic Growth
The “terabyte club” will reach 6 million by 2015
There will be over 20 million households generating half a terabyte per month in 2015
-‐Cisco Visual Networking Index: Forecast and Methodology, 2010-‐2015
• Need: 1 Gbps bi-‐direcHon pipe in five years • Need more digital – Less Analog :: No Analog!
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Digital vs. Analog
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Simple Headend Best PracHces • Separate amplificaHon for analog & digital • No amplificaHon for DOCSIS • No amplificaHon for AGC pilot signals !! ▫ Lose pilot – lose plant & DOCSIS
• Minimize combining & cable runs ▫ eQAMs & dense CMTSs will have low output power • Do use forward path monitoring on QAMs
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Analog Impairments • For each 1 dB increase in system carrier levels:
• CTB raHo degrades by 2 dB • CSO raHo degrades by 1 dB • CNR improves by 1 dB
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CTB CSO
Noise Floor
Visual carriers Aural carriers
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Digital DistorHons – CIN & CCN • For each 1 dB increase in system carrier levels: ▫ CNR behaves as before with all-‐analog operaHon ▫ CIN raHo degrades by 1 to 2 dB (mix of 2nd & 3rd order) ▫ CCN raHo degradaHon depends on CIN and CNR values ▫ See ANSI/SCTE 17 2007
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Thermal noise
CCN
CIN
Visual carrier
Aural carrier
QAM Channels
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Sweep
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Standing Waves
Roll off at band edges
Misalignment
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Space Between QAM Channels Small
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No Sweep Points 8 MHz BW
No Sweep Points 8 MHz BW
• One sweep point every 8 MHz • No sweep points under QAM
• A lot can happen between QAM channels!
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Some Examples
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Loose seizure screw on amplifier
Corrosion on seizure screw in amplifier causes standing wave
• Suckouts, standing waves, LTE, and other impairments more difficult with standard sweep
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Sweepless Sweep – How it Works • Compares headend levels to outside plant levels
• No sweep injecHon signals (non-‐interfering)
• Less expensive, no headend unit, just meter
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Sweepless Sweep
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Sweepless Sweep System Problems
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Digital Levels • Cable Modem or Set Top Box ▫ Ideal Downstream RF Input: 60 dBuV (0 dBmV) ▫ Recommended RF Input: 55 – 65 dBuV (±5 dBmV) ▫ Worse Case RF Input: 50 – 70 dBuV (±10 dBmV) ▫ Never exceed total power: 90 dBuV (30 dBmV) • Too high or too low causes receiver demod issues
• Recommended Tx levels for opHmum CNR: ▫ 100 – 110 dBuV (40 – 50 dBmV)
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Summary • Cable networks are moving from analog to digital • CTB, CSO, etc. turn into noise (CIN) • Sweep systems may need to be upgraded • Correct digital levels at end devices are criHcal ▫ May require new test equipment
• It’s a great Hme to be in cable!
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