Possibilities and limitations of Extended Spectrum DOCSIS return path
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The document discusses the challenges of higher upstream frequencies in DOCSIS technology, particularly the impact of outdoor temperature changes on return path performance. It highlights that issues become evident above 100 MHz and problematic above 204 MHz, suggesting that following forward path changes can mitigate seasonal maintenance needs. Further results and information are expected to be shared at the forthcoming technical forum.
![Teleste Proprietary. All rights reserved.
Upstream frequency responses
6
Frequency [MHz]
10 30 50 70 150 170 190 204 220
+140°F
+77°F reference
-4°F
18 dB
10 dB
14 dB
12 dB
16 dB
4
dB
1.5 dB](https://image.slidesharecdn.com/possibilitiesandlimitationsofesdreturnpathapril2021-210527065531/85/Possibilities-and-limitations-of-Extended-Spectrum-DOCSIS-return-path-6-320.jpg)
![Teleste Proprietary. All rights reserved.
Upstream frequency responses (RFF ON)
9
Frequency [MHz]
10 30 50 70
18 dB
10 dB
14 dB
12 dB
16 dB
1 dB
1 dB
150 170 190 204 220
+140°F RFF ON
+77°F reference
-4°F RFF ON](https://image.slidesharecdn.com/possibilitiesandlimitationsofesdreturnpathapril2021-210527065531/85/Possibilities-and-limitations-of-Extended-Spectrum-DOCSIS-return-path-9-320.jpg)
Possibilities and limitations of Extended Spectrum DOCSIS return path
- 1. Teleste Proprietary. All rights reserved. Possibilities and limitations of the Extended Spectrum DOCSIS return path Steve Condra Senior Director, Engineering and Product Management Teleste Intercept
- 2. Teleste Proprietary. All rights reserved. Preface 2 From HFC standpoint the higher upstream capacity requires “DOCSIS 4.0 technology supports up to 10 Gbps speeds downstream capacity and up to 6 Gbps upstream capacity, easily allowing for multi-gigabit symmetric services over HFC networks.” https://www.cablelabs.com/technologies/docsis-4-0-technology Higher frequencies, higher gain, higher RF power Advanced constellations (1K, 2K OFDM) requiring better RF performance More advanced amplifiers (when N≠0) What “more advanced amplifiers” means, besides better RF performance … Why does the changing outdoor temperature become an additional challenge?
- 3. Teleste Proprietary. All rights reserved. 1K OFDM upstream (DOCSIS 3.1) 𝑀𝐸𝑅𝑅𝑃𝐷_𝑈𝑆 = −10 log10 10 𝑀𝐸𝑅𝐶𝑀_𝑈𝑆 −10 + 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓𝑎𝑚𝑝𝑠 × 10 𝐶𝑁𝑅𝑎𝑚𝑝 −10 3 Modulation RPD upstream receive requirements (MER) CM upstream TX (MER) 1K OFDM 35.5 dB 44 dB In theory five cascaded amplifiers can meet this MER requirement easily CNR performance of an ESD amplifier is ≈ 55 dB for the upstream
- 4. Teleste Proprietary. All rights reserved. 1K OFDM upstream, amplifier clusters 4 Noise cumulation (funneling), assumption: around 20 (4x5) amps below an RPD However, due to the changing outdoor temperature….. 𝑀𝐸𝑅𝑅𝑃𝐷_𝑈𝑆 = −10 log10 10 𝑀𝐸𝑅𝐶𝑀_𝑈𝑆 −10 + 4 × 5 × 10 𝐶𝑁𝑅𝑎𝑚𝑝 −10 → 𝑀𝐸𝑅𝑅𝑃𝐷_𝑈𝑆 ≈ 40 𝑑𝐵 CM RPD
- 5. Teleste Proprietary. All rights reserved. Test (from -4°F to 140°F ) 5 17 dB@ 1.2 GHz 20 dB@ 1.2 GHz 26 dB@ 1.2 GHz 23 dB@ 1.2 GHz Network Analyzer Heating Chamber Coax: 100 ft = 2.83 dB @ 1.2 GHz, 100 ft = 1.07 dB @ 204 MHz Note: Internal (but not external) temperature compensation always on
- 6. Teleste Proprietary. All rights reserved. Upstream frequency responses 6 Frequency [MHz] 10 30 50 70 150 170 190 204 220 +140°F +77°F reference -4°F 18 dB 10 dB 14 dB 12 dB 16 dB 4 dB 1.5 dB
- 7. Teleste Proprietary. All rights reserved. Consequences 7 Attenuation increases, modems have higher (if possible) output level, at some point amplifiers are overloaded. → Distortion → Lower MER Attenuation decreases, modems have lower output level, at some point input levels of amplifiers are too low. → Noise rises → Lower MER
- 8. Teleste Proprietary. All rights reserved. Proposal 8 17 dB@ 1.2 GHz 20 dB@ 1.2 GHz 26 dB@ 1.2 GHz 23 dB@ 1.2 GHz RFF RFF RFF RFF RFF Heating Chamber Network Analyzer Note: Internal and external temperature compensation on By following downstream changes, we can make real-time upstream adjustments Return path gain Return path slope Return Follows Forward (RFF) = Return path ALSC Return path ALSC has been used successfully in Europe together with 204 MHz upstream
- 9. Teleste Proprietary. All rights reserved. Upstream frequency responses (RFF ON) 9 Frequency [MHz] 10 30 50 70 18 dB 10 dB 14 dB 12 dB 16 dB 1 dB 1 dB 150 170 190 204 220 +140°F RFF ON +77°F reference -4°F RFF ON
- 10. Teleste Proprietary. All rights reserved. Summary 1. As upstream frequencies rise, outdoor temperature changes cause return path issues 2. Issues become visible above 100 MHz and problematic above 204 MHz 3. By following forward path changes (RFF), all seasonal maintenance visits can be avoided 4. More information / results above 204 MHz will be published at fall technical forum 10
- 11. Teleste Proprietary. All rights reserved. For more information, please contact: steve.condra@telesteintercept.com 11