Dynamic Spectrum ManagementDynamic Spectrum Management((1000M x 1000M)1000M x 1000M)

IEEE SCV Communications Society October 12, 2005

Speaker: J. CioffiStanford University (M. Mohseni, V. Pourahmad, M. Brady)

cioffi@stanford.edu

Special Thanks to: ASSIA Inc (Wonjong Rhee, I. Almandoz , G. Ginis, P. Silverman) SBC Network Systems Engineering (R. Savoor, S. Sposato)France Telecom (R&D) (H. Mariotte, M. Ouziff, F. Gauthier)British Telecom (K. Foster, J. Cook)Deutche Telekom T-Systems (S. Symalia, E. Berndt, J. Buhl)Alcatel Bell (DSM Research Group)Telcordia (K. Kerpez & D. Waring)

2

Automated Maintenance (=DSM)

• OPS = Majority of DSL effort• Reduce through electronic

management of– Provisioning– Maintenance– Qualification– Capacity (rate/range)

• Reduce “truck rolls” and improve overall ADSL performance– Permits higher speeds further

70+ %30- %

DSL "Effort" Equipment

Operations

3

Two DSM (“adaptive”) Steps

1. DON’T “HOG”• (Each line uses minimum power)

• Adaptive Spectrum

2. Cooperate• Signal Alignment

4

Outline

• Step One (Adaptive Spectra)– Margin/Rate management– Impulse/code management

• Step Two (Signal Alignment)

5

DSM System Diagram

• Accepts data• Processes data• Provides recommendations

FiberFiber

DLCDLCRTRT

ADSL

H or VDSL

ADSL

ADSL

cable

CO

DSLAM

RT+

CLEC

DSM CENTERDSM CENTER

ILEC

MonitorMonitor

ProvisionProvision

MaintainMaintain

MonitorMonitor

ProvisionProvision

MaintainMaintain

6

DSM Data (to DSM Center)

1) ADSL1• Margins, powers, rates, bit table, code

violations • Current and max data rates

2) Web Pages / ADSL2 (WT87)• Attenuation[n], Noise[n]

3) Loop “Make-Up” Report• Lines at same service terminal (same and nearby binders)• Common lengths (taper codes), bridged taps, total length

I/CLEC

DSM CENTERDSM CENTER

MonitorMonitor H or VDSL

ADSLcable

CO

DSLAM(EMS)

7

DSM Controls (from DSM Center)

I/CLEC

DSM CENTERDSM CENTER

MonitorMonitor H or VDSL

ADSL

cable

CO

DSLAM(EMS)

• Maxrate VECTOR

– Maxrate[1] (present conditions)

– Maxrate[2] = Difficult conditions

– Maxrate[3] = Other DSLs doing DSM

– Each may have different profile

• Profile Recommendation

– Rates/Margins

– Code Choices

[3]

[3]

[1]

[2]

Data rate

[0] = current rate

8

DSL Subscriber (Initially 384 kbps)

• 13.6 kft, currently at 384 kbps– Own power use (904 kbps)– Polite fiber-fed terminals (each held at 1.536

Mbps)

DSM Use - Mixed (RT/DSLAM) Binder

0

200

400

600

800

1000

1200

1400

1600

1800

2000

current full power Polite RTs

Power Usage

Dat

a R

ate

(kb

ps

)

Series1

RT/DSLAM Mix Victim

0

1

2

3

4

5

6

7

8

1 14 27 40 53 66 79 92 105 118 131 144 157 170 183 196 209 222 235 248

tone index

bit

s/to

ne

9

DSM Multi-user Rate REGIONS

• Plot of all possible rates of users– any point is possible

• More than 2 users (vector of possible rate-tuples)• Fear of “hogs” forces the small area to be used

– With worst-case FIXED models currently applied

RRlonglong

RRshortshort

SpectralSpectral pair 1pair 1

Spectral pair 2Spectral pair 2

Current “static spectrum management”Current “static spectrum management”

10

What is Politeness (Near/Far) ? (near transmitter “speaks softly” – transmits only power it needs)

RTRT

NEARNEAR

FARFARCOCO

Downstream Example

Upstream Example

LTLTNEARNEAR

FARFAR

11

Telcordia DSM-ADSL Rate Regions [T1E1.4/2002-063]

lines 1 & 3 (2 held at 1.6 Mbps)lines 1 & 3 (2 held at 1.6 Mbps) lines 1 & 2 (3 removed) – 063R1lines 1 & 2 (3 removed) – 063R1

• Nominal 15 kft data rate without DSM– 300 kbps

A AA A

Fiber, 10 kft

5 kft

Copper, 15 kft

A15 kft

Nominal 300 kbpsNominal 300 kbps

12

Higher Speeds? Symmetric? (yes with DSM)

• No coordination yet (but no hogging allowed)• No effect on existing ADSL if implemented with DSM• How did we do this???

13

Carrier A and DSM, CO/RT (ASSIA)

14

ADDNMR = Iterative Water-Fill• Minimize Power (at some max margin)

– Diagram on right below

• No coordination of modems– Service provider sets Rate & ADNMR

• “Adaptive Spectrum”

NSR(f)NSR(f)

S(f)S(f)

NSR(f)NSR(f)

S(f)S(f)

“HOG” (margin = 30 dB) POLITE (margin << 30 dB)

15

DSLAM to CPE

• Margins > 16 dB to 10 kft.– Despite promise by vendors that 16 dB would not be exceeded

• CPE Problem? – (no, CPE, DSLAM, and ITU standards all share in fault)

Measured Noise Margin (CURNMR) Comparison

05

101520253035

1000

3000

4000

5000

6000

8000

1000

0

1100

0

1300

0

1500

0

Loop Length, kft

No

ise

Mar

gin

, d

BAlcatel Speed TouchRA MAXNMR10

Efficient 5100 RAMAXNMR10

Westell MH RAMAXNMR10

Efficient 5100 RAPower BackOffMAXNMR10

2Wire Router

Modem 1Modem 1

Modem 2Modem 2

Modem 3Modem 3

Modem 4Modem 4

Modem 5Modem 5

16

Another Vendor Issue – “Virtual Noise”

• Telco sets a worst-case noise– Often wrong or not possible– Undue conservative (opposite of politeness)

17

Use of VN Upstream VDSL near/far

0 2 4 6 8 10 12 14 16 18 200

1

2

3

4

5

6

7

8

600 m. Lines

900

m.

Line

s

IW vs. VN, where VN = "noise seen in IW +10dB"

VN

IW

0 2 4 6 8 10 12 14 16 18 200

1

2

3

4

5

6

7

8

600 m. Lines90

0 m

. Li

nes

IW vs. Mixed IW/VN

IW

VN/IW

Same ILEC all lines Unbundled

VNVN

Politeness (IW)Politeness (IW)

18

Outline

• Step One (Adaptive Spectra)– Margin/Rate management– Impulse/code management

• Step Two (Signal Alignment)

19

A General Finding from FT work• Use erasures and lower-rate RS codes

– When code/CRC violations found– Use normal settings of (240,224) when no CRC violations

(i.e., no impulses)

20

Steps to take?

• Ask subscriber modem vendors for– Max-impulse protection option– Invoked by DSM Center when CRC or FEC violations noted– Almost in G.997.1 parameters (need > 500 s)

DSM CenterDSM CenterCenterCenter DSLAMDSLAM SubscriberSubscriber

ADSLADSL

Max impulse mode

CRC Violations

21

Live Subscriber – Bad Impulse

• 10 kft 26-gauge• Intermittant noise, 0-400 kHz• Code Violations even with

nominal “interleave” setting– 768 kbps– 28 dB DS margin, but CVs– 19 dB US margin, but CVs

• After DSM : > 3 Mbps– Uses 48,32 FEC

Bad Impulse House

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

1 14 27 40 53 66 79 92 105 118 131 144 157 170 183 196 209 222 235 248

tone index

bit

s/t

on

eCode Violations - 15 min

0

500

1000

1500

2000

2500

3000

3500

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33

15-min Interval

CR

C V

iola

tio

ns

22

Carrier C and DSM: Advanced INP

23

Cioffi DSL Line 1

• 17000’ loop• Provisioned at 192 kbps, now running 768 kbps with early DSM

NoiseNoise(also impulse(also impulsenot shown)not shown)

Insertion lossInsertion loss

24

Cioffi DSL Line 2

• 8000’ loop (fiber-fed “remote terminal” RT)• Provisioned at 1536 kbps, now running 6008 kbps with early DSM

ADSL FEXT region

1500’ bridged-tap

Noise

AM radio

Insertion loss

NoiseNoise(also impulse(also impulsenot shown)not shown)

25

Outline

• Step One (Adaptive Spectra)– Margin/Rate management– Impulse/code management

• Step Two (Signal Alignment)

26

Bonding ≠ Vectoring

• Bonding– Use N lines to get N x the data rate

• Possible to vector also, but bonding does not force use of vectoring

– Mux and inverse Mux

• Vectoring– Cogenerate at PHY level signals and/or– Coreceive at PHY level signals– Can do one-sided without bonding– Can do one/two-sided with vectoring

27

STEP TWO – “Vectoring”(Signal Alignment)

20-100 Mbps20-100 Mbps(symmetric)(symmetric)

CentralOffice

ILEC LT/RT

Switchrouter

FIBER

twisted pair

DSLAM

DSM

bbiinnddeerr

• Note Fiber to RT or LT

DSM

28

Upstream – Multiple Access (per tone)

• One for each tone• Lines synchronized and digitally duplexed• 3rd generation vectored DSLAM• Works as if No NEXT or FEXT present

Wn=Q’n++

YZ

X1,nG1,n

X2,nG2,n

.

.

.

XL,nGL,n

Hn=QnRnn(Loop)

dec

Bn=Rn

Feedback orPacket detector

One One sideside

29

Downstream Broadcast (per tone)

Q’n++

Y

Z1,nD1,n

Z2,nD2,n

.

.

.

ZL,nDL,n

mod

Bn=Rn

Feedback orPacket precoder

Xn,i

Hn=RnQnn

()

• One for each tone

• Lines synchronized and digitally duplexed

• 3rd generation DSLAM

• Works as if no FEXT present

One One sideside

30

T-Systems (German -DT) ResultsVDSL with SHDSL (I)

31

German results for VDSL with HDB3 (III)

32

Symmetric Rates – AS (green) vs SIA (blue)

• Increases data rates at all lengths with Vectored DSLAM• Power can be lowered – possible to do 10 dBm or less• 100 Mbps (single line, no bonding) at 1500 ft symmetric, 2500 ft

asymmetric• Cioffi’s 17 kft loop to 2.5 Mbps (256 kbps up) !

33

Ultimate Result of Vectoring

• Distribution Area to 100 Mbps single line

• 1000M x 100 Mbps– Getting closer to the goal

34

The Wireless Power Co ?

• Hmmm ……..– Lots of antenna’s needed for 100 Mbps (both sides)– Lots of power for 100 meters or more also– Perhaps high-speed wireless LAN stays at end of

DSL (like today)?

35

GDSL?• Pedestal drop

– <300 meters– 2 to 6 lines

typical– Xtalk is self

• Last few 100 meters is $$$ for fiber

GDSLGDSL

36

Split-pairs/”phantoms”7766

5544

3322

1100

There are actually 7 independent channels in those 4 loopsThere are actually 7 independent channels in those 4 loopsall 7 have high capacityall 7 have high capacity

Well over 1000 Mbps at 300 meters (category 3)Well over 1000 Mbps at 300 meters (category 3)

Vector 7x7 channelVector 7x7 channelPedestal drop DSL – how fast?Pedestal drop DSL – how fast?

37

Matrix Matched LoadVs(7)

Zs Z0

Vs(6)

Vs(5)

Vs(4)

Vs(3)

Vs(2)

Vs(1)

ZLZL

• Resistor across all 7 possibilities

38

Some Results (symmetric FDM)

39

DSM• DON’T “HOG”

– Adaptive Spectrum– 100M x 10M

2. Cooperate• Signal Alignment• 1000M x 100M

100 M100 M

3. GIGABIT DSL (GDSL)• 1000M x 1000M GGDSLDSL