Brady	  Volpe	  
Massive	  Traffic	  Growth	  The “terabyte club” will reach 6 million by 2015There will be over 20 million households genera...
Digital	  vs.	  Analog	  ©	  The	  Volpe	  Firm	  	  	  	  ConfidenHal	  3	  
Simple	  Headend	  Best	  PracHces	  •  Separate	  amplificaHon	  for	  analog	  &	  digital	  •  No	  amplificaHon	  for	  ...
Analog	  Impairments	  •  For	  each	  1	  dB	  increase	  in	  system	  carrier	  levels:	  •  CTB	  raHo	  degrades	  by...
Digital	  DistorHons	  –	  CIN	  &	  CCN	  •  For	  each	  1	  dB	  increase	  in	  system	  carrier	  levels:	  ▫  CNR	  ...
Sweep	  	  ©	  The	  Volpe	  Firm	  	  	  	  ConfidenHal	  7	  Standing WavesRoll off at band edgesMisalignment
Space	  Between	  QAM	  Channels	  Small	  ©	  The	  Volpe	  Firm	  	  	  	  ConfidenHal	  8	  No	  Sweep	  Points	  8	  MH...
Some	  Examples	  ©	  The	  Volpe	  Firm	  	  	  	  ConfidenHal	  9	  Loose seizure screw on amplifierCorrosion on seizure ...
Sweepless	  Sweep	  –	  How	  it	  Works	  •  Compares	  headend	  levels	  to	  outside	  plant	  levels	  •  No	  sweep	...
Sweepless	  Sweep	  ©	  The	  Volpe	  Firm	  	  	  	  ConfidenHal	  11	  
Sweepless	  Sweep	  System	  Problems	  ©	  The	  Volpe	  Firm	  	  	  	  ConfidenHal	  12	  
Digital	  Levels	  •  Cable	  Modem	  or	  Set	  Top	  Box	  ▫  Ideal	  Downstream	  RF	  Input:	   	  60	  dBuV	   	  (0	...
Summary	  •  Cable	  networks	  are	  moving	  from	  analog	  to	  digital	  •  CTB,	  CSO,	  etc.	  turn	  into	  noise	...
©	  The	  Volpe	  Firm	  	  	  	  	  	  ConfidenHal	  15	  Brady	  Volpe	  brady.volpe@volpefirm.com	  
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Anga 2013 v2

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DOCSIS & Testing Best Practices in an All Digital Network

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Anga 2013 v2

  1. 1.  Brady  Volpe  
  2. 2. Massive  Traffic  Growth  The “terabyte club” will reach 6 million by 2015There will be over 20 million households generatinghalf 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!  ©  The  Volpe  Firm        ConfidenHal  2  
  3. 3. Digital  vs.  Analog  ©  The  Volpe  Firm        ConfidenHal  3  
  4. 4. 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  ©  The  Volpe  Firm        ConfidenHal  4  
  5. 5. 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  ©  The  Volpe  Firm        ConfidenHal  5  CTB CSONoise FloorVisual carriers Aural carriers
  6. 6. 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  ©  The  Volpe  Firm        ConfidenHal  6  Thermal noiseCCNCINVisual carrierAural carrierQAM Channels
  7. 7. Sweep    ©  The  Volpe  Firm        ConfidenHal  7  Standing WavesRoll off at band edgesMisalignment
  8. 8. Space  Between  QAM  Channels  Small  ©  The  Volpe  Firm        ConfidenHal  8  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!  
  9. 9. Some  Examples  ©  The  Volpe  Firm        ConfidenHal  9  Loose seizure screw on amplifierCorrosion on seizure screw in amplifiercauses standing wave•  Suckouts,  standing  waves,  LTE,  and  other  impairments  more  difficult  with  standard  sweep  
  10. 10. 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  ©  The  Volpe  Firm        ConfidenHal  10  
  11. 11. Sweepless  Sweep  ©  The  Volpe  Firm        ConfidenHal  11  
  12. 12. Sweepless  Sweep  System  Problems  ©  The  Volpe  Firm        ConfidenHal  12  
  13. 13. 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)    ©  The  Volpe  Firm        ConfidenHal  13  
  14. 14. 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!  ©  The  Volpe  Firm        ConfidenHal  14  
  15. 15. ©  The  Volpe  Firm            ConfidenHal  15  Brady  Volpe  brady.volpe@volpefirm.com  

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