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Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics •...

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1 Motorola General Business Use, MOTOROLA and the Stylized M Logo are registered in the US Patent & Trademark Office. All other product or service names are the property of their respective owners. © Motorola, Inc. 2009 Access Networks Solutions Introduction to S-CDMA
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Page 1: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

1Motorola General Business Use,

MOTOROLA and the Stylized M Logo are registered in the US Patent

& Trademark Office. All other product or service names are the property of their respective owners. ©

Motorola, Inc. 2009

Access Networks Solutions

Introduction to S-CDMA

Page 2: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

2

Why S-CDMA?•

Upstream is a looming bottleneck–

Traffic growth–

Competitive environment–

Highly bandlimited

Imperative that the bandwidth be fully exploited–

Unused spectrum represents 25-40% of band–

Unused Spectrum = Unused Capacity

DOCSIS tools for optimal upstream use–

Optimize Mbps: Modulation Profiles (64-QAM @ 5.12 Msps)–

Optimize Channel: Pre-Equalization–

Optimize Spectral Usage: S-CDMA

S-CDMA is standardized, mature, powerful – cost effective new capacity

Page 3: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

3

Upstream Impairment Catalogue•

Narrowband Interference–

Radio signal ingress–

Common path distortion (CPD)

Burst/Impulse Noise–

1 us – 100 ms duration–

Strongest < 20 MHz–

Combined with ingress < 20 MHz–

S-CDMA is uniquely capable against impulse noise

….and thus also against combined impulse plus ingress

Other–

Frequency Response Distortion–

Noise Floor

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

Time

Impulsive Events

15 16 17 18 19 20 21-60

-50

-40

-30

-20

-10

CPDIngress

Frequency

Narrowband Interference

Page 4: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

4

Impulse Noise – Spectrum

Impulse Noise – Typical < 20 MHz

Signature and Burst Typical

Burst

Page 5: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

5

Impulse Noise – MER PerspectiveNode NDN02, Modem 0019.5EE6.87FE

MER vs. DOCSIS TX PRE-EQ Levels

27

28

29

30

31

32

33

34

35

36

17:16

18:14

19:12

20:09

21:07

22:04

23:02

0:00

0:57

1:55

2:52

3:50

4:48

5:45

6:43

7:40

8:38

9:36

10:33

11:31

12:28

Time (Beginning 10-21-08)

MER

(dB

)

-12.00

-11.50

-11.00

-10.50

-10.00

-9.50

-9.00

DO

CSI

S TX

PR

E-EQ

Lev

els

(dB

c)

MER MT/TAP MT/(+/-3T) MT/POST

> 8 dB Range

> QAM Order

Equalizer Taps (Channel Freq Response)MER

MER versus Time

Page 6: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

6

S-CDMA Overview

Page 7: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

7

S-CDMA Basics

What–

Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology added in D2.0, and enhanced in D3.0

Why–

S-CDMA technology is particularly robust against impulse noise, a critical requirement at the low end (<20 MHz) of the band

How–

S-CDMA stretches QAM symbols out in time by 128 times–

Symbols multiplied by (-1 or 1) via CDMA spreading “code”–

Transmits all sets of stretched symbols in parallel–

Zero theoretical interference among transmissions due to special code properties

No decrease in channel capacity

Page 8: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

8

S-CDMA Spread Symbol

Up to 128 symbols (codes) can be transmitted at the same time

Spread Interval

Chip = 1/Symbol RateTime

←O

rthog

onal

Cod

es →

Page 9: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

9

DOCSIS 2.0 vs 3.0 S-CDMA

DOCSIS 2.0 S-CDMA–

Full impulse immunity (Code spreading + FEC)–

Ingress cancellation•

A few narrowband interferers•

Sufficient for majority of live deployments

DOCSIS 3.0 S-CDMA–

Selectable Active Codes: SAC Mode 2•

Enhanced ingress cancellation–

Maximum Scheduled Codes (MSC)•

Trade SNR for throughput – fewer codes used, more power in each

Page 10: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

10

S-CDMA: Benefits and Capabilities

Page 11: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

11

Key S-CDMA Benefits•

Impulse noise robustness for lower upstream band–

Gain of symbol spreading >100x A-TDMA at same throughput–

Improving A-TDMA robustness requires narrower channels•

Decreases throughput•

Still weaker than S-CDMAS-CDMA is strongly recommended below 20 MHz

Combined ingress and impulse immunity–

D3.0 S-CDMA & A-TDMA are comparable in ingress-only–

S-CDMA outperforms A-TDMA for combined ingress + impulse typically observed < 20 MHz (D2.0 or D3.0)

Secondary Benefits–

Increased efficiency of synchronous operation–

Lower FEC overhead due to inherent impulse immunity–

Max Scheduled Code feature – SNR vs throughput trade-off

Page 12: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

12

S-CDMA vs. A-TDMA Comparison

Recover unused and/or underutilized 5-20 MHz bandwidth–

S-CDMA: 67 Mbps in lower channels (152 Mbps total)–

A-TDMA: 30 Mbps in lower channels (115 Mbps total)•

S-CDMA throughput Advantages–

Increase capacity up to ~50% –

Ensure 100 Mbps upstream service capacity–

Defer node splitting

42 MHz5 MHz

64 QA

M

SC

DM

A

64 QA

M

ATD

MA

64 QA

M

ATD

MA

64 QA

M

ATD

MA

32 QA

M

SC

DM

A

16 QA

M

ATD

MA

64 QA

M

ATD

MA

64 QA

M

ATD

MA

64 QA

M

ATD

MA

16 QA

M

ATD

MA

16 QA

M

ATD

MA

16 QA

M

ATD

MA

A-TDMA

S-CDMA

32 QA

M

SC

DM

A

Page 13: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

13

Est. Link Gain – S-CDMA vs A-TDMA

• QAM Relationships: 4-8 dB represents 1-2 orders of modulation– 16-QAM → 32-QAM (~3 dB) → 25% more throughput– 16-QAM → 64-QAM (~6 dB) → 50% more throughput– 32-QAM → 64-QAM (~3 dB) → 20% more throughput

Frequency Band 2.56 Msps 5.12 Msps5.0-9.0 MHz < 6 dB < 8 dB

9.0-15.0 MHz < 4 dB < 6 dB15.0-20.0 MHz < 2 dB < 4 dB

20 MHz < fo ~Equiv ~Equiv

Page 14: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

14

S-CDMA Summary•

The Situation Upstream –

Traffic continues to grow–

New channels are being added–

Spectrum remains limited– Maximize spectrum– Optimize its use

Congestion Relief–

S-CDMA: standardized 7+ years ago–

Built for tough channels–

Available, mature, improved, proven

S-CDMA is required to effectively operate high throughput channels at lower end of band–

Works where A-TDMA will not–

Better throughput where A-TDMA supports a modest link

S-CDMA: Cost-Effective Upstream Capacity

Page 15: Introduction to S-CDMA - SCTEchapter.scte.org/...D3-Upstream-S-CDMARonHowald.pdfS-CDMA Basics • What – Synchronous Code Division Multiple Access (S-CDMA) is an upstream technology

15Motorola General Business Use,

MOTOROLA and the Stylized M Logo are registered in the US Patent

& Trademark Office. All other product or service names are the property of their respective owners. ©

Motorola, Inc. 2009

Access Networks Solutions

Thank You!

Dr. Robert Howald CTO Office Motorola Home & Networks [email protected]


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