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• Introduction
• What is cable Proactive Network monitoring an Overview
• How does it work
• Full Band Capture: A spectrum analyzer in every home
• Demo of cPNM
• Conclusion
Agenda
Cable Proactive Network Maintenance as a Service (CPNMaaS)
• Lower OPEX by reducing call volume and truck rolls for field problems and repair issues.
Objective
• PNM provides proactive monitoring of the DOCSIS network. Allowing for repairs to be identified, located, prioritized and completed before service impact to customers.
Solution
• Improved operational efficiency, lowered OPEX cost, improved system performance and forward looking impact of new services like DOCSIS 3.1.
Result
Delivery Process
CMTS
MSO Subscriber Database CPNM Portal
AS RF NCE
Failure Scenarios
Detailed Analysis
Optimization Levers
Cable Modem Full Spectrum Capture
OUTPUT – Recommendations
•Open Cases with NOC
•Track Issues open by CPNM
•Provide SME resource for field
•Assist in Delivering Optimization Service
Cable PNM Collector
DC
Customer Network
(SNMP, CLI)
Technician Portal FSC
cPNM motivation
Which of the following do you have deployed more widely in your network?
(A)
Portable
test equipment
(B)
Handheld
test equipment
(C)
DOCSIS-based CPE
cPNM in cable networks: Overview
• Uses DOCSIS cable modems and set-tops as continuous “probes” throughout the network to identify and locate plant and subscriber drop problems
• Detect and locate faults in coax and actives before rolling trucks
• Perform trend analysis to predict future faults before they happen
• Improve network performance to higher levels for DOCSIS 3.1
• How? (1) Derive complex frequency response signatures from modem pre-equalization coefficients, (2) look for responses indicative of the presence of linear distortions, and (3) overlay modem location information on digitized outside plant maps.
cPNMaas Key Tenants
Turnkey ownership
NOC Business Assurance:
Improved effectiveness
Accelerated migrations,
and
Service assurance/experience
Focus People
Dedicated Team with vast Deployment Experience
End-to-End Responsibilityfrom Installation, Support, Maintenance and operation of the PNM service
Core Skills in Execution, Technology, and Process
Proactive Maintenance:
• Maintaining optimal
consumer
experience
• KPI/KQI measured
progress and
analytics
• Iterative
improvement,
learning and
adapting to smooth
preventative
maintenance
• Net positive
subscriber retention
• Faster Time to
Deployment
• Lesser Maintenance
Windows
• Right First Time
Approach
• Productivity and
Predictable Success
• Fact-based and
Evidence-based
Refinements
• Maintaining Security
Posture
What is equalization?• In a coaxial cable distribution network, higher frequencies are attenuated more than
lower frequencies as RF signals travel through the coax. This results in a tilted frequency response at the input to each amplifier.
• It is necessary to install a fixed-value plug-in equalizer at each amplifier. The equalizer has the opposite amplitude-versus-frequency response of the coaxial cable preceding the amplifier.
• The equalizer “cancels” the tilted frequency response, resulting in a flat amplitude-versus-frequency spectrum at the input to the amplifier’s internal gain stages.
50 MHz 870 MHz 50 MHz 870 MHz
50 MHz 870 MHz
Equalizer’s frequency response
Spectrum’s frequency responseafter equalization
What is an adaptive equalizer?
• Adaptive equalization performs a function similar to that of a cable amplifier’s equalizer, but rather than equalizing the entire 50-860 MHz downstream or 5-42 MHz upstream RF spectrum, it deals with just a single channel. Adaptive means the equalizer can change its characteristics as channel conditions change.
Graphic courtesy of Sunrise Telecom
What is an adaptive equalizer?
• An adaptive equalizer is a digital circuit that compensates for a digitally modulated signal’s in-channel complex frequency response impairments.
•Complex frequency response includes amplitude (or magnitude)-versus-frequency, and phase-versus-frequency.
• The adaptive equalizer uses sophisticated algorithms to derive coefficients for an equalizer solution “on the fly”—in effect, creating a digital filter with essentially the opposite complex frequency response of the impaired channel.
•At high SNR (ES/N0) the equalizer will synthesize the opposite response of the channel. At lower SNR doing so would cause noise enhancement, so a compromise solution is derived.
Pre-equalizer’s frequency
response
(inverse of channel response
“seen” by modem)
Post-equalized frequency
response
(response “seen” by CMTS)
Equalizer
Impedance MismatchesSource
(7 dB return loss)Load
(7 dB return loss)Transmission Medium
(1 dB attenuation)
+31 dBmVat time T0
+30 dBmVat time T1
+22 dBmV
+15 dBmV
+23 dBmV
+14 dBmV(-16 dBc)at time T2
+30
+25
+20
+15
+10
+5
Am
plit
ud
e(d
Bm
V)
Time (T)
Incident signal (T1) Echo (T2)
+14 dBmV
+30 dBmV
234 ns
100 ft23 20
Information that can be derived from coefficients (single modem)
Impulse coefficients (adaptive equalizer
graph)
In-channel frequency response
In-channel phase response
In-channel group delay
QAM constellation
Cable modem: CMTS:
cPNM: Locating a fault
• This example shows a 5T echo. That is, the time delay of the echo is approximately 5 symbol
periods.
• For a 6.4 MHz bandwidth upstream QAM signal, the symbol period is 1/(5.12 Msym/s) =
1.953E-7 second, or about 195 ns
• One symbol period can be converted to distance: (T/2) x VF, where T is the symbol period in
ns, and VF is the cable’s velocity factor: (195/2) x 0.87 = 85 feet, or 25.8 meters
• The distance for a 5T echo is 5 x 85 feet = 425 feet, or 130 meters
Distance from where?• Rule #1 - The distance is not measured from the modem
• Rule #2 - There must be at least two reflection points
• Rule #3 - The fault is one of the reflection points
~3.5T echo = 298 feetDistance between
splitter and
amplifier is 299
feet, or 91
meters
cPNM spectrum analysis
• Quickly view the performance of the entire forward spectrum
• Complements DOCSIS coarse metrics (MER, FEC, etc.)
Why spectrum analysis?
• Evaluate frequency response of downstream RF spectrum
• Look for downstream ingress
Standing
waves
Resonant
peaking
Ingress
(e.g. LTE)FM radio
ingress
Suckouts Roll-off Filters Adjacency
Viewable frequency response impairments
Non-flat spectrum• Suck-outs/notches
• Tilt (and direction)
• Ripples/waves
• Roll-off
• Resonance/peaking
• Excessive leveling
• Adjacency/alignment
• Signal levels
• Pilot levels
• Missing QAM channels
• Audits
Interference/distortionOver-the-air ingress
FM
UHF
LTE
Foreign carriers
Wideband/transient noise
Group delay variation (filters, etc.)
Distortion/intermodulation
cPNM: A technician’s perspective
• It’s like having TDRs and spectrum analyzers distributed throughout the network (all DOCSIS devices) under centralized control
• Quicker identification of problem cause and fix strategy
• Customers don’t lose service during measurements
• Service calls can send techs to exactlywhere the problem is to quickly fix the issue
cPNM: An engineer’s perspective
• Uses DOCSIS CPE upstream pre-equalization coefficients to estimate channel impulse response
• Interpolation of pre-equalizer tap samples increases accuracy
• Correlation among modems and integration with GIS allows triangulation to locate source of impairment
cPNM: A manager’s perspective
• Raises the bar of our collective understanding of RF
• Exposes the problems being solved by adaptive equalizers
• Exposes end-of-line performance, creates transparency
• Potential to improve operational efficiency
cPNM summary
• cPNM is a game changing technology that reduces OPEX and increases customer satisfaction
• cPNM technology will also be important in moving to higher order modulation in DOCSIS 3.1 since the plant must be even better maintained
• cPNM “hooks” have been included in the DOCSIS 3.1 specification
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