DOCSIS 3.0 US
Planning & Bandwidth
Management
John Downey, Consulting Network Engineer – CMTS BU
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
1
Co-Sponsor – CCI Systems
 Cisco Gold Partner
 End-to-end network
services
–
–
–
–
–
Presentation_ID
Network and headend engineering
Network mapping
Network construction (cable/fiber)
Network maintenance
NOC services
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
2
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)
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
3
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.
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
4
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.
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
5
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
6
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
7
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
8
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
11
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
12
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
14
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
15
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
16
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
17
US Load Balance & Isolation Example
CMTS US0
@ 24 MHz
4-Way
Fiber Optic
Rx 1
Filter
CMTS US2
@ 31 MHz
Amplifier
4-Way
Fiber Optic
Rx 2
CMTS US1
@ 24 MHz
 Attempting to “share” one US port across two other US ports
– Can cause isolation issues
– Load balance issues (ambiguous grouping)
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
18
System Levels Reverse
• 17 dB at 5 MHz & 32 dB at 1 GHz
• Eliminates max transmit CMs
CS(CEQ) tap
• Eliminates high DS tilt to TV
26
350’
1.5 dB
23
500’
2
17
FEQ
w/ US
pad
600’
2.5
Input 17
Reverse 43 dBmV
transmit
level @ the tap
42
39.5
4
Step
Attenuator
or EQ tap
29
X 38
PIII .5” cable
.40 dB @ 30 MHz
A total design variation of ~14 dB!
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
19
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
20
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
21
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
Presentation_ID
© 2009 Cisco Systems, Inc. All rights reserved.
Cisco Confidential
22