docsis 3.0 us planning & bandwidth management

© 2009 Cisco Systems, Inc. All rights reserved. Cisco ConfidentialPresentation_ID 1

DOCSIS 3.0 US Planning & Bandwidth Management

John Downey, Consulting Network Engineer – CMTS BU

© 2009 Cisco Systems, Inc. All rights reserved. Cisco Confidential 2Presentation_ID

Co-Sponsor – CCI Systems

Cisco Gold Partner End-to-end network

services– Network and headend engineering– Network mapping– Network construction (cable/fiber)– Network maintenance– NOC services


Co-Sponsor – Todd Gingrass, CCI Systems Vice President of Network

Technology 14 years at CCI Systems. Bachelor of Electrical Engineering

degree from Michigan Technical University

Certifications include Cisco Certified Network Associate Routing & Switching (CCNA), Cisco Certified Design Associate (CCDA), and Cisco Certified Internetwork Professional (CCIP)

A member of the Society of Cable and Television Engineers (SCTE) and Institute of Electrical and Electronics Engineers (IEEE)


Presenter – John Downey, Cisco 20 years in the

data/telecommunications/ networking industry

BS in Electrical Engineering from Penn State University.

Nine years with Cisco as a Broadband Network Engineer presently with the Cable Modem Termination System (CMTS) Business Unit.

Certifications include CCNA and CCCS.

An SCTE member since ’96.


Agenda

Frequency Stacking Levels– What is CM max US output with four channels stacked and do

channels have to be contiguous?

Power/Hz & laser clipping Diplex Filter Expansion to 85 MHz?

– Amplifier upgrades occurring now; Best to make 1 truck roll– Think about diplex filters, line EQs, step attenuators, taps, etc.


Business Objectives

Allow more BW for DOCSIS 1.x & 2.0 CMs

Limit/reduce more node splits

Introduce new HSD service of 50 to 100 Mbps

Allow migration of existing customers to higher tier and DOCSIS 3.0 capability– Better Stat Muxing


ATDMA General Deployment Recommendations After increasing CW to 6.4 MHz, measure & document

unequalized US MER at multiple test points in the plant– Use PathTrak Return Path Monitoring System linecard– Or Sunrise Telecom Upstream Characterization toolkit

25 dB or higher Unequalized MER is recommended– Less than 25 dB reduces operating margin– Check US MER as well as per-CM MER

Pick freq < 30 MHz away from diplex filter group delay

Make sure latest IOS version is running on CMTS

Turn on Pre-Equalization


US MER(SNR) Issues Increasing ch width from 3.2 to 6.4 keeps same average

power for single carrier– SNR drops by 3 dB or more

Keeping same power/Hz could cause max Tx level from CMs and/or laser clipping/overload

Equalized vs unequalized MER readings

Modulation profile choices– QPSK for maintenance, 64-QAM for Data, 16-QAM for VoIP?– Max output for 64-QAM is 54 dBmV

• Cab up n power-adjust continue 6

Pre-EQ affect– Great feature in 1.1 & > CMs, but could mask issues


D3.0 US Issues Frequency Stacking Levels

– What is the max output with multiple channels stacked– Is it pwr/Hz & could it cause laser clipping?

Diplex Filter Expansion to 85 MHz– If amplifier upgrades are planned for 1 GHz, then pluggable diplex

filters may be warranted to expand to 85 MHz on the US– Still must address existing CPE equipment in the field and potential

overload– RFoG could be perfect scenario (maybe even 200 MHz split)

CM must be w-online (requires 1.1 cm file) for US bonding Monitoring, Testing, & Troubleshooting

– Just like DOCSIS 2.0, now test equipment needs to have D3.0 capabilities


US Frequency and Level Issues Freq assignments

– 5 to 42, 55, 65, 85 MHz ?• Diplex filters, line EQs, step attenuators, CPE overload

Max Tx for D2.0 64-QAM for 1 ch is 54 dBmV

D3.0 US ch max power– Tx for D3.0 TDMA

• 17 - 57 dBmV (32 & 64-QAM)• 58 dBmV (8 & 16-QAM)• 61 dBmV (QPSK)

– Tx for D3.0 S-CDMA• 17 - 56 dBmV (all modulations)

Max Tx per ch for 4 freqs stacked at 64-QAM ATDMA is only 51 dBmV & 53 for S-CDMA


Total Power Was only one US channel present, now up to four US chs

transmitting at same time– Possibly 6.4 MHz each; nearly 26 MHz US channel loading

Lots of power hitting return path fiber optic transmitter

Probability of laser clipping is increased, especially if using legacy Fabry-Perot (FP) lasers– Good idea to upgrade to Distributed Feedback (DFB) lasers, which

have significantly more dynamic range

Use return path monitoring system capable of looking above 42 MHz to see second and third order harmonics

Any burst noise above diplex filter (i.e. 42 MHz) coming out of return path receiver is usually indicative of laser clipping


Laser Clipping

Blue trace shows case of strong laser clipping Green line represents flat US laser noise floor with no clipping Note that this US has four US bonded channels


Channel Placement

Each US channel used for bonding is individual channel

Transmitters (channels) are separate– Don't have to be contiguous and can have different physical layer

attributes like; modulation, channel width, tdma or scdma, etc.

Frequencies can be anywhere in US passband and do not need to be contiguous

It may be wise to keep relatively close so plant problems like attenuation and tilt don’t cause issues

CM will have some dynamic range to allow specific channels to be a few dB different vs. other channels


New Architectures New conundrum raised when fiber run deeper into network

– RF over Glass (RFoG)– DOCSIS Passive Optical Networks (DPON)

May incorporate 32-way optical splitter/combiners. Having a laser Tx in your house combined with 32 other houses feeding 1 Rx in the HE is addressed with lasers timed with the actual traffic from the house; unlike how it is done today where the US laser is on all the time

US bonding and/or load balancing presents potential issue where an US laser could be transmitting same time as another US laser

May be acceptable with multiple lasers transmitting same instant in time, if they are carrying different frequencies,

Will S-CDMA pose same problems? This multiplexing scheme allows multiple CMs to transmit same instant in time


US Load Balance & Isolation Example

Attempting to “share” one US port across two other US ports– Can cause isolation issues– Load balance issues (ambiguous grouping)

4-Way

4-WayCMTS US0@ 24 MHz

CMTS US1@ 24 MHz

CMTS US2@ 31 MHz

Fiber OpticRx 1

Fiber OpticRx 2

Filter

Amplifier


System Levels Reverse

26 23 17 4350’ 500’ 600’

1.5 dB 2 2.5

17Input

43 dBmV 42 39.5 29

PIII .5” cable.40 dB @ 30 MHz

Reversetransmitlevel @ the tap

A total design variation of ~14 dB!

CS(CEQ) tap

• 17 dB at 5 MHz & 32 dB at 1 GHz• Eliminates max transmit CMs• Eliminates high DS tilt to TV

FEQ w/ US pad

Step Attenuator or EQ tap

38X


Transmit Level Possibilities Running D3.0 CM in low modulation scheme

allows higher power

Use D3.0 CM in 2.0 mode– Single frequency on D3.0 CM offers 3 dB higher power

Using SCDMA with more codes may also allow higher Tx power, but depends on implementation

Minimum level of 17 dBmV (24?) could cause issues in lab environment or HE test CM– Pmin = +17 dBmV, 1280 ksym/s– Pmin = +20 dBmV, 2560 ksym/s– Pmin = +23 dBmV, 5120 ksym/s


Summary

Cost effective and faster time to market– Decrease costs today – deploy DOCSIS 3.0 later with no

additional CMTS investment!

Targeted insertion of D3.0 – Leverage existing US chs while adding more US capacity– Load balance 1.x/2.0 and enable D3.0 when needed– Minimizes capex & opex

Leverage D3.0 bonding for D2.0 tiers & services – Better stat-mux efficiency– Improved consumer experience


Summary (cont)

Long term D3.0 service planning – Insure optimized frequency allocation– Enable seamless upgrade to higher D3.0 tiers– Wire once– Add QAM chs as tiers or service take-rates go up

End-to-end solution minimizes risk– CMTS, QAM, and CPE

Account for physical connectivity, not just channel capacity– May not be advantageous to combine noise to satisfy connectivity

docsis 3.0 us planning & bandwidth management

Documents