DOCSIS 3.1:

WHAT IS IT, HOW DOES IT WORK, AND

HOW CAN YOU PREPARE FOR IT?

Daniel Howard, SCTE CTO

July 16, 2013

VIDEO

PART 1: OFDM BUSINESS DRIVERS

MAIN OBJECTIVES: As we go through Part 1 of todays lecture, you

should be able to answer the following questions:

What are the options in multiplexing today's data signals to the customer?

What are the business, market and technology drivers for OFDM in cable?

Why move beyond QAM 256?

What are the options for higher order modulation?

How will DOCSIS 3.1 with OFDM enable operators to deliver higher speed

data services and increase the capacity of their HFC access networks?

What makes OFDM especially well suited to deliver wider effective channels?

In a phrase: MORE HFC CAPACITY IS NEEDED!

Market drivers: Business services, Over The Top (OTT) video, 4K video, 3DTV, etc.

Economic drivers: Decrease cost per bit transmitted

How much capacity do we need?

10 Gb/s downstream or greater

1 Gb/s upstream or greater

Flexibility requirement: Need easy adaptation to different amounts of spectrum and plant conditions

BUSINESS DRIVERS FOR OFDM ON HFC

Higher orders of modulation (HOM)

Elimination/reduction of RF guard bands

Greater capacity achieved primarily through LDPC (HOM in clean channel) and OFDM (elimination of guard bands and HOM in impaired channels)

Close to 2x improvement over DOCSIS 3.0

HOW TO GET MORE CAPACITY?

256-QAM 4096-QAM

NO WASTED CAPACITY: OFDM

ADAPTIVE BIT LOADING

OFDM D/S PHY

channel S

ub

-ca

rrie

r -

25

6 Q

AM

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b-c

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ier

- 2

56

QA

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Su

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ier

- 5

12

QA

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b-c

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ier

- 5

12

QA

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Su

b-c

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ier

- 1

02

4 Q

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b-c

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- 4

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6 Q

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- 4

09

6 Q

AM

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b-c

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02

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Why not just add LDPC to Single Carrier (SC) QAM to get higher order modulation? Guardbands and robustness!

Other reasons for going to OFDM: Easier channel synthesis

Less complex than MAC layer bonding

Channel equalization (EQ) is simpler

Incremental capacity addition

Better economies of scale

Attract new chipset and system vendors to cable market

HIGHER ORDER MODULATION OPTIONS

PART 2: ENGINEERING DETAILS

MAIN OBJECTIVES: As we go through Part 2 of todays lecture, you

will be able to answer the following questions:

How does OFDM differ from conventional FDM, ATDMA, and S-CDMA?

How are the subcarriers orthogonal to each other in OFDM?

How and why is the IFFT used in defining the OFDM waveform?

How are pilot tones and the cyclic prefix used in OFDM?

How does OFDM optimize the modulation order used in RF spectrum?

Why makes OFDM better than S-CDMA and ATDMA in general?

GLOSSARY:

FDM: Frequency Division Multiplexing ATDMA: Advanced Time Division Multiple Access

IFFT: Inverse Fast Fourier Transform S-CDMA: Synchronous Code Division Multiple Access

OFDM: Orthogonal Frequency Division Multiplexing

OFDM sub-carriers can be packed tightly without interfering with each other

And they fall off faster at band edges

THE OFDM CONCEPT

SC-QAM OFDM

Mathematical orthogonality:

In communications, orthogonality means zero interference with each other at the receiver sampling instant

Orthogonality in communications is typically in one of these domains: temporal, frequency, code, or spatial

ORTHOGONALITY DEFINED

0)()(, b

a

dxxgxfgf

ORTHOGONALITY EXAMPLES: TDMA

Ramp-down

time

Guard time at

CMTS receiver:

Timing-phase

difference

Dtsi-th Burst

Ramp-up

time

(i+1)-th Burst

Symbol

period

ORTHOGONALITY EXAMPLES: S-CDMA CODE DOMAIN

RF

Channel

Spreading

Code 1

Data stream 1

+Spreading

Code 2

Data stream 2

Spreading

Code N

Data stream N

De-spreading

Code 1

Data stream 1

De-spreading

Code 2

Data stream 2

De-spreading

Code N

Data stream N

ORTHOGONALITY EXAMPLES: S-CDMA TIMING SYNCH

Ramp-down

time

Guard time at

CMTS receiver

may be 0

Timing-phase

difference

nearly 0i-th Burst

Ramp-up

time

(i+1)-th Burst

Chip

period

OFDM ORTHOGONALITY

Df = k , k = 1 typically t

rect(t) transforms to sin(f)/f or sinc(f)

Precise

frequency spacing

F

time frequency

HOW OFDM DATA IS TRANSMITTED VIA IFFT

),()(1

0

/2 DnIFFTekD N

N

k

Nnkj

D(k)

D(k)

D(k)

e +j

0n

e +j

1n

e +j

N-1n

+ Channel

This

is mathematically

equivalent to this:

OFDM TX BLOCK DIAGRAM

Scrambler Error

Correction Encode

Interleaver Symbol

Map (bits to QAM)

Seri

al t

o P

aral

lel

IFFT

Para

llel t

o S

eria

l

Data bits

to RF

upconverter

Cyclic Prefix

OFDM CYCLIC PREFIX

N-point IFFT Output

copy

SymbolnSymboln-1 Symboln+1

Cyclic Prefix

OFDM SYNCHRONIZATION

Frequency Synchronization Error

Clock Synchronization Error

Other carriers do not cancel

Initial synch is lost during sampling

PILOT TONES IN OFDM

These curves are the same for OFDM as for S-CDMA and ATDMA in an additive white Gaussian noise (AWGN) channel

BER PERFORMANCE IN AWGN

PART 3: PERFORMANCE DETAILS

MAIN OBJECTIVES: As we go through Part 3 of todays lecture, you

will be able to answer the following questions:

Why is OFDM better on the upstream in impulse and narrow band ingress?

What are the advantages/disadvantages of OFDM?

What are some key areas that cable operators can focus on when preparing to

deploy OFDM in their networks?

How will operators transition to OFDM and higher order QAM rates?

What are the operational system and network implications of OFDM and its

deployment?

OFDMS SECRET WEAPON

time frequency

Narrow subcarriers mean long symbols

Benefits are easy

mitigation of: Micro-reflections

Ingress, impulse and burst noise

23 dB

tap(R=7 dB)

20 dB

tap

(R=7 dB)

+31 dBmV +30 dBmV

+23 dBmV+22 dBmV

+15 dBmV +14 dBmV

100 feet (1 dB loss)

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

x 10-4

-0.01

-0.005

0

0.005

0.01

0.015

0.02

CA Node H41

BURST NOISE PERFORMANCE DETAILS

0.5 1 1.5 2 2.5 3 3.5 4

x 107

-70

-65

-60

-55

-50

-45

-40

0.5 1 1.5 2 2.5 3 3.5 4

x 107

-75

-70

-65

-60

-55

-50

-45

-40

-35

FFT of oscilloscope capture of burst noise event on upstream

Same trace with burst noise event clipped out of time capture Reveals ingress and

flatness of actual channel

MDU cable modems can have highly attenuated upstreams

S-CDMA and OFDM modulations allow Tx power to be concentrated on fewer tones (or codes in S-CDMA) SNR per tone is much higher

Reduces burst rate, but keeps spectral efficiency high

HIGHLY ATTENUATED UPSTREAMS

Normal power per

tone

Cable upstream frequency

OFDM has a high peak-to-average power ratio (PAPR), but so does a spectrum full of SC-QAM

PAPR can be reduced, but probably not necessary

HIGHER PEAK TO AVERAGE POWER RATIO OF OFDM

PAPR = (|x|2)peak

xrms2

PART 4: DEPLOYMENT PLANNING

MAIN OBJECTIVES: As we go through Part 4 of todays lecture, you

will be able to answer the following questions:

How will operators transition to OFDM and higher order QAM rates?

What are the operational system and network implications of OFDM and its

deployment?

What are some key areas that cable operators can focus on when preparing to

deploy OFDM in their networks?

How will the SCTE help operators deploy DOCSIS 3.1 OFDM in their networks?

OPERATION ON HFC NETWORKS

Key aspects: Upstream spectrum remains below downstream

CPE devices support current and future upstream splits

CPE devices operate in current and future downstreams

Deployment implications No plant changes required to deploy DOCSIS 3.1 equipment

Future proof - no CPE or infrastructure swap required

EFFECTIVE MIGRATION STRATEGY

Achieved primarily by including: Backward compatibility requirements

Support for upgrades to DOCSIS 3.1 technology in CCAP

How does that enable an effective migration

strategy? Incremental deployment of DOCSIS 3.1 modems

Continued use of DOCSIS 2.0 & 3.0 modems after 3.1 upgrades

DOCSIS 3.1 TECHNOLOGY - MIGRATION

Backward compatibility

Support of at least 24 bonded SC-QAMs in downstream and 8 in upstream

S-CDMA in the upstream

DOCSIS 3.1 CMs required to operate on DOCSIS 3.0 CMTSs

DOCSIS 3.1 CMTSs required to support DOCSIS 3.0 (and 2.0) CMs

To be implemented also with CCAP equipment

Operation on existing HFC networks

Upstream spectrum remains below downstream

Supports operation with existing upstream splits (42/65 MHz as mostly in operation,

85 MHz as specified in DOCSIS 3.0)

Supports spectrum enhancement in upstream (e.g. 200 MHz) and downstream (e.g.

1.2 GHz or even 1.7 GHz)

Supports the ability to take advantage of enhanced capabilities when network,

headend and CPE equipment permit

DOCSIS 3.1 Use Cases

Today

Few 1.0/1.1 Lots of 2.0 Some 3.0 C

PE

He

ade

nd

5-65 MHz US 3.0 CMTS

DS Bonding

Soon

Remove 1.0/1.1 More 3.0

3.0 CCAP More DS Bonding

US Bonding S-CDMA

3.1 CM

Many 3.0 First 3.1

3.0 CCAP More DS & US

Bonding

3.1 DS CCAP

3.1 CCAP First 3.1 DS OFDM

DS Expansion

Lots of 3.0 More 3.1

3.1 US CCAP

First 3.1 US OFDMA

Lots of 3.1

Better HFC

US & DS Expansion

Reduction of 2.0

Considerations when introducing DOCSIS 3.1 DOCSIS 3.0 CCAP before DOCSIS 3.1 available First DOCSIS 3.1 CM with DOCSIS 3.0 CCAP Introducation of DOCSIS 3.1 DS in CCAP via Firmware Upgrade Introducation of DOCSIS 3.1 US in CCAP via Line Card swap Expansion of frequency range particularly in US very complex

DOCSIS 3.0 CM DOCSIS 3.1 CM

DOCSIS 3.0 CMTS/CCAP DOCSIS 3.1 CMTS/CCAP

(Source: CableLabs, Comcast)

TOWARDS FTTH ? Residential Services

Business Services

DOCSIS 3.0

Channel Bonding

EPON / GPON / P2P

CCAP

High-density Headend

DOCSIS 3.1

New PHY

Distributed Architecture

All Fiber

EPoC

Time

SCTE SUPPORT FOR DOCSIS 3.1

SCTE engineering support to 3.1 spec development

DOCSIS training/certification update for 3.1

Other content

DOCSIS 3.1 landing zone: SCTE Standards

SCTE recommended practice documents

New SCTE HFC readiness working group

Symposium on 3.1/HFC readiness

SCTE HFC READINESS SPECIAL WORKING GROUP (SWG)

Goal: Accelerate deployment of 3.1

Output: Best practices documents for optimizing network

capacity with DOCSIS 3.x

Kickoff meeting 24 May 2013

Phase 1: Optimizing loaded DOCSIS 3.0 networks

Delivery: 1 Sep 2013

Phase 2: Optimizing loaded DOCSIS 3.1 networks

Measurement project to be undertaken

Procedures being written up for MSOs

Webinar planned to demonstrate procedures

SWG team as backup to do measurements

PHASE 1 GENERAL ISSUES

How fully loaded D3.0 network capacity is affected by

equipment performance limits and plant impairments

Planning and optimization recommendations

Recommendations for network equipment and monitoring

equipment

How to configure, monitor, and maintain a fully utilized

DOCSIS 3.0 upstream and downstream

SWG TOPICS FOR PHASE 1 DOCUMENT

Laser linearity and dynamic range (headroom)

Noise measurement recommendation (Measurements for accurate noise/interference diagnostics)

Impairment visibility on fully loaded plants

Effect of changing signal levels (increase for High Order Modulation, distortion, etc)

Educating the workforce for High order Modulation with existing equipment (new tools)

Availability of test & diagnostics equipment (to add intelligence and higher measurement resolution)

LTE ingress, TV white space, satellite and MoCA

Minimum standards for plant & maintenance (+evolution)

Beyond MER (higher order moments in measurements)

Dynamic modulation rollback and proactive network maintenance (PNM) actions

Best mix of SCDMA and ATDMA

Improve Home/Biz/MDU installation practices (certificate of install, better records, trends/tracking,

operations and field)

Impairment library, map to migration strategy

Better CMTS metrics

Configuration/optimization planning (CMTS, plant specific, key knobs)

TUTORIALS IN PHASE 1 DOCUMENT

Upstream laser characterization using D3.0 bonded carriers

Steady state ingress, transient noise, and high levels of collisions in

contention mini-slots with modern equipment (VSA, DSO, CMTS)

RF spectral power density considerations for the upstream:

Constant power per Hz, constant power per carrier, other power

profiles, and other methods to optimize total upstream capacity

Correlation of RF leakage measurements to downstream and upstream

ingress and transient noise estimation; and

New measurement procedures oriented towards determining how best to

maximize the capacity of fully loaded DOCSIS 3.x networks.

IMPACT OF INGRESS AND CONTENTION COLLISIONS ON UPSTREAM LASER

-40

-35

-30

-25

-20

-15

-10

-5

0

5

10

15

20

25

30

35

6 14 22 30 38 46 54 62 70 78 86

Am

plit

ud

e (

dB

mV

)

Frequency (MHz)

DYNAMIC RANGE VS. LASER TYPE

IMPAIRMENT VISIBILITY OUT OF BAND

-40

-35

-30

-25

-20

-15

-10

-5

0

5

10

15

20

1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81

Am

plit

ud

e (

dB

mV

)

Frequency (MHz)

Transient Noise on Return Node

HOMEPLUG INTERFERENCE SEEN ON UPSTREAM

WHAT TO MEASURE

Attenuation and thermal noise in the channel vs. transmit power limit

Capabilities of existing optics

Frequency response/Micro-reflections

Ingress, impulse and burst noise

Non-linear impairments (CSO, CTB)

LONG TERM REQUIREMENTS

Objectives of 10 Gbit/s DS and 1 Gbit/s US capacity requires more RF spectrum 1.2-1.5 GHz on the downstream, 200-400 MHz on the upstream

Highest availability and capacity may ultimately require Better DFB cooled downstream lasers

Higher powered upstream lasers

Improved passives and RF amplifiers

These improvements can be done surgically, only on nodes where needed

Characterizing current plant performance will determine how close an MSO can come to the objectives with minor to moderate tweaks to the existing HFC Infrastructure

OFDM basics tutorial http://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.php

What is OFDM (Hranac) http://www.cablefax.com/cfp/ct/news/ctreports/commentary/What-Is-OFDM_55404.html

OFDM FAQ/Tutorial http://mobiledevdesign.com/tutorials/ofdm/

OFDM Tutorial http://www.complextoreal.com/chapters/ofdm2.pdf

DVB-C2: Revolutionising RF Bandwidths Utilization in Cable http://www.ict-redesign.eu/fileadmin/documents/1003_SCTE_Broadband_DVB-C2.pdf

OFDM and the orthogonality principle http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/

Wikipedia entry on OFDM http://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexing

The principles of OFDM (RF Design) http://rfdesign.com/images/archive/0101Puegel30.pdf

OFDM Overview (Va Tech) http://www.mprg.org/research/OFDM/index.html

OFDM Uncovered Part 1: The Architecture http://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecture

REFERENCES / FOR MORE INFO

http://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.phphttp://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.phphttp://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.phphttp://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.phphttp://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.phphttp://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.phphttp://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.phphttp://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.phphttp://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.phphttp://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.phphttp://www.radio-electronics.com/info/rf-technology-design/ofdm/ofdm-basics-tutorial.phphttp://www.cablefax.com/cfp/ct/news/ctreports/commentary/What-Is-OFDM_55404.htmlhttp://www.cablefax.com/cfp/ct/news/ctreports/commentary/What-Is-OFDM_55404.htmlhttp://www.cablefax.com/cfp/ct/news/ctreports/commentary/What-Is-OFDM_55404.htmlhttp://www.cablefax.com/cfp/ct/news/ctreports/commentary/What-Is-OFDM_55404.htmlhttp://www.cablefax.com/cfp/ct/news/ctreports/commentary/What-Is-OFDM_55404.htmlhttp://mobiledevdesign.com/tutorials/ofdm/http://www.complextoreal.com/chapters/ofdm2.pdfhttp://www.ict-redesign.eu/fileadmin/documents/1003_SCTE_Broadband_DVB-C2.pdfhttp://www.ict-redesign.eu/fileadmin/documents/1003_SCTE_Broadband_DVB-C2.pdfhttp://www.ict-redesign.eu/fileadmin/documents/1003_SCTE_Broadband_DVB-C2.pdfhttp://www.ict-redesign.eu/fileadmin/documents/1003_SCTE_Broadband_DVB-C2.pdfhttp://www.ict-redesign.eu/fileadmin/documents/1003_SCTE_Broadband_DVB-C2.pdfhttp://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://www.ice.rwth-aachen.de/research/algorithms-projects/ofdm/ofdm-and-the-orthogonality-principle/http://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexinghttp://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexinghttp://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexinghttp://rfdesign.com/images/archive/0101Puegel30.pdfhttp://www.mprg.org/research/OFDM/index.htmlhttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecturehttp://www.eetimes.com/design/communications-design/4141953/OFDM-Uncovered-Part-1-The-Architecture

Courses Channel Bonding in DOCSIS 3.0

http://www.scte.org/professional_development/channel_bonding_in_docsis_30_on_demand_description.aspx

Coaxial Cable in the HFC Plant http://www.scte.org/professional_development/_coaxial_cable_in_the_hfc_plant.aspx

Data Communications http://www.scte.org/professional_development/data_communications_description.aspx

Digital Basics and DOCSIS Fundamentals http://www.scte.org/events/Digital_Basics_and_DOCSIS%C2%AE_Fundamentals_.aspx

DOCSIS Systems http://www.scte.org/events/DOCSIS%E2%84%A2_Deployment_Detail.aspx

Return Path http://www.scte.org/events/Return_Path_Detail.aspx

Primers: What is LTE?

http://www.scte.org/resources/SCTE_Primers_for_Download.aspx#LTE

What is Modulation? http://www.scte.org/resources/SCTE_Primers_for_Download.aspx#modulation

SCTE DOCSIS AND PHY LAYER LEARNING RESOURCES

http://www.scte.org/professional_development/channel_bonding_in_docsis_30_on_demand_description.aspxhttp://www.scte.org/professional_development/_coaxial_cable_in_the_hfc_plant.aspxhttp://www.scte.org/professional_development/data_communications_description.aspxhttp://www.scte.org/events/Digital_Basics_and_DOCSIS%C2%AE_Fundamentals_.aspxhttp://www.scte.org/events/DOCSIS%E2%84%A2_Deployment_Detail.aspxhttp://www.scte.org/events/DOCSIS%E2%84%A2_Deployment_Detail.aspxhttp://www.scte.org/events/Return_Path_Detail.aspxhttp://www.scte.org/resources/SCTE_Primers_for_Download.aspxhttp://www.scte.org/resources/SCTE_Primers_for_Download.aspx