Presentation by Steve Condra, Senior Director, Engineering and Product Management for Teleste Intercept. SCTE® LiveLearning for Professionals Webinar™ Series: Swimming Upstream: How to Boost Upstream Network Capacity, February 17th 2022

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Extended Upstream
– The Heat is on!
Steve Condra
Senior Director, Engineering and Product Management

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Upstream RF Levels
Additional Bandwidth translates to additional RF level variation.
• In the past, variation in attenuation was handled by the cable modem.
• Some variation in setup attenuation (differences in drop length)
• Some variation in temperature (seasonal).
• In the future, it is likely that we could exceed the cable modem capability.
• Downstream signals use closed loop feedback to measure and adjust.
• The burst nature of Upstream signals makes that difficult.
• Teleste Technology Project Goals
• Estimate the expected variation as a result of reasonable temperature fluctuations
• Recommend a method to enable amplifiers to compensate if required.
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Amplifiers and Cables in a Heating Chamber
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Downstream Output: 55dBmV, 17 dB tilt (258 MHz … 1794 MHz)
Upstream Input: 11 dBmV flat
Attenuation: 1000ft. Coaxial cable -> 15 dB@396 MHz, 11 dB@204 MHz

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Frequency Response of the Cascade, Upstream ALSC off
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Green@77°F, Orange@-4°F, Red@140°F (-20°C, 25°C, 60°C)
Theoretical
50MHz 2.6 dB
100MHz 3.7 dB
150MHz 4.4 dB
204MHz 5.1 dB
396MHz 7.3 dB

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The problem
• The last amplifier in the cascade that feeds is forced to
tolerate signal level fluctuations caused by the network
before and after it.
• 7.3 dB is equivalent to a 180-ft (RG6) coaxial cable (±90-ft)
• What if an existing 150-ft drop cable would have 60-ft …
240-ft virtual length?
• The variable “length”/level challenges even the best
amplifiers and especially cable modems
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Theoretical
50MHz 2.6 dB
100MHz 3.7 dB
150MHz 4.4 dB
204MHz 5.1 dB
396MHz 7.3 dB

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Solution
• ALSC (Automatic Level and Slope Control) is a closed loop feedback
technology for measuring RF levels of two channels in the downstream to
adjust level and slope for downstream RF control.
• RFF (Reverse Follows Forward) uses an algorithm to take the measurements
from the ALSC downstream signals and adjust the upstream RF levels
accordingly.
• The amplifier and embedded technology is smart enough to calculate how
much attenuation is passive vs. cable and then translate that change in
attenuation to the appropriate frequency response of the cable.
• (i.e. a signal change at 900 MHz can be used to calculate the corresponding
change in c
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The Solution: Upstream ALSC On (Return-follows-forward)
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Green@77°F, Orange@-4°F, Red@140°F
Measured
50MHz ±1 dB
100MHz ±1 dB
150MHz ±1 dB
204MHz ±1 dB
396MHz ±1 dB

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Conclusions
• Cable networks
• Typically will have cable modems not capable of adjusting for variation in drop length
combined with seasonal temperature changes at the higher frequencies.
• Typically amplifiers do not tolerate extremely high/low return path signal levels
• High signal levels could overloaded amplifiers -> nonlinear behavior -> decrease MER
• Low signal levels -> noise increases -> decreases MER
• Use amplifiers to compensate signal level as a result of temperature fluctuations
• Allow cable modem upstream signal level to compensate for variation in drop length.
• The RFF upstream ALSC provides superior performance at an affordable price.
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