Modified Adjacent Frequency Coding For Increased Notch Depth under

DAA/Spectral Sculpting

Kevin A. Shelby, Johann Chiang, Dr. Jim LansfordAlereon Inc.

CrownCom MykonosJune 2006

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Outline

- Objectives

- Regulatory Outlook

- System Overview

- System Design Considerations

- Simulation Results

- Closing Remarks

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Objectives- Extend adjacent frequency coding to include

some form of multi-carrier modulation:- Reuse antipodal signaling aimed at canceling

sidelobe contributions in adjacent carriers;- Introduce multi-carrier modulation to minimize the

impact on the existing WiMedia PHY Specification:- Preserve the existing time/frequency spreading characteristics in

order to maintain system performance in the presence of a variety of channel impairments, SOP interference most notably;

- Preserve the existing tone mapping to minimize the impact on the interleave and cyclic shift structures.

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Current Regulatory Outlook

1000 2000 3000 4000 5000 6000 7000 8000 9000 10000-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

Frequency (MHz)

Ave

rage

Pow

er S

pect

ral D

ensi

ty (

dBm

/MH

z)

UWB Spectral Mask

FCC R&O (Indoor)CEPT (Proposed)MIC (Proposed)

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Band Group 1

Band Group 2

Band Group 3

Band Group 4

Band Group 5

DAARequired

DAARequired

DAA Requirement Postponed in Europe

until June 30, 2010

IncreasedRolloff

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Adjacent Sidelobe Contributions- AFC leverages the observation that sidelobe

contributions in adjacent tones are similar in amplitude:

100 110 120 130 140 150 160 170 180-0.2

0

0.2

0.4

0.6

0.8

1Sidelobe Levels

Frequency(MHz)

Am

plitu

de

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Sidelobe Cancellation- The achievable notch depth can be increased by canceling

adjacent sidelobe contributions:

100 110 120 130 140 150 160 170 180-60

-50

-40

-30

-20

-10

0Sidelobe Cancellation

Frequency(MHz)

Sid

elob

e S

uppr

essi

on (

dBc)

Baseline TX OutputAntipodal Signaling

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Existing DCM Mechanism- Dual Carrier Modulation as originally conceived can be

described in terms of a linear transformation, M, as follows:

- Where the indices {a,b,c,d} represent a mapping from the interleaved transmit bitstream,

- and M={mij}; i,j=[1:2] constitutes a linear mapping of tones in the transmit OFDM symbol.

12/:0,2221

1211mod

50

D

db

ca

n

n Nnjxx

jxx

mm

mmk

y

y

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Modified AFC- Building directly on the original AFC proposal, a

linear mapping resembling that employed by DCM can be identified, aimed at canceling mutual interference in adjacent subcarriers:

- Where ck= xk +j yk corresponds to the output of the symbol mapper, QPSK or DCM encoded, depending on the selected data rate.*

*The extent to which M-AFC can be applied at rates above 200Mb/s is still under investigation.

12/:0,1

1

12

2mod

12

2

D

n

n

n

n Nnc

ck

y

y

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Baseband Transmitter

IFFT

SymbolMapper

Coding/Puncturing

Scrambler Interleaver

Pilots

Zero DC

DACsP/S

()*

2X

Preamble

Add ZeroSuffix

AnalogFilters

M

ToneNulling

Guard

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System Design ConsiderationsNotch Depth

Notch depth varies as a function of the scaling factor, , with the benefit of antipodal signaling maximized as approaches unity.

1

Invertible Matrix

The principal objective in introducing the scaling factor was to permit an invertible matrix at the receiver.

Det(M) = 1-2 ≠ 1

Tone Erasure

The potential for symbol erasure occurs whenever the data content in adjacent tones is the same, i.e. c2n = c2n+1.

y2n = c2n(1- ) < 1

RX SNR SNR in the RX constellation is maximized when the TX mapping results in evenly distributed constellation points.

= 1/2

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Achievable Notch Depth

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 20

5

10

15

20

25

30Modified AFC Scaling Factor

alpha

notc

h de

pth

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TX Constellation(=8/16)

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5TX Constellation: afcMAP(alpha = 0.5)

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RX Constellation

-4 -3 -2 -1 0 1 2 3 4-4

-3

-2

-1

0

1

2

3

4RX Constellation: Payload(200Mb/s) TFC5

-4 -3 -2 -1 0 1 2 3 4-4

-3

-2

-1

0

1

2

3

4RX Constellation: Header TFC5

Equalizer OutputDeMapper OutputDeSpread Output

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System SimulationSimulation results were compiled using the

following system configuration:- WiMedia compliant 1.0 PHY- Mandatory rates (53.3-200Mb/s)[1]- M-AFC, = 0.5- ~20MHz tone notching (3.6-3.8GHz)- Incumbent service passive during link tests

[1] The applicability of M-AFC to higher data rates is still under investigation

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DAA Spectral ScultpingSimple Tone Notching Modified AFC

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Link Performance

2 2.5 3 3.5 4 4.5 5 5.5 610

-2

10-1

100

SNR (dB)

PE

R (

%)

TFC1: CM2, 200Mbps, 1024 Octets, sculpting 9 tones in Band1

Sculpting

Sculpting w/ SCS

No sculpting

2 2.5 3 3.5 4 4.5 5 5.5 6

10-2

10-1

100

SNR (dB)

PE

R (

%)

TFC3: CM2, 200Mbps, 1024 Octets, sculpting 9 tones in Band1

Sculpting

Sculpting w/ SCS

No sculpting

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Closing Remarks- M-AFC applies a linear transformation at the symbol

mapper output leaving tone assignment and existing interleaver structure unchanged;

- Resembling DCM, M-AFC achieves antipodal signaling without sacrificing the time/frequency spreading present in the existing spec;

- The resulting notch depth approaches that demonstrated with the original AFC, less ~5dB once considerations affecting link performance are taken into account;

- The rate of OOB rolloff also increases similarly to the original AFC proposal over that without antipodal signaling.