10gbase-t: a new proposal for improving pam performance with...

March 2004

10GBASE-T: A new proposal for improving PAM performance with OFDM

Yuji Kasai, Eiichi Takahashi, Tetsuya Higuchi(National Institute of Advanced Industrial Science and Technology )

Masahiro Murakawa(Evolvable Systems Research Institute)

Shinji Nishimura(Hitachi, Ltd.)

2

Supporters

• The Tokyo Electric Power Company, Inc.

• POWEREDCOM, Inc.

3

• OFDM signal transmission method applied to 10GBASE-T

• PAM-based frequency division multiplexing – 10-Gbps data transmission– 6.1-dB noise margin

• 100-m signal transmission with CAT-7 cable

Objectives

4

1. Current 10GBASE-T proposals

+3 -3 -1-4 Noise Margin (dB)with 6 dB coding gain

0.5-2us

20

-

500

1000

4D-PAM8

192633 RequiredSNR (dB)

< 100 ns

2

625

1250

PAM-5

< 100 ns< 100 nsLatency

3-LaunchVoltage (Vp-p)

417312.5Bandwidth(MHz)

833625Symbol Rate(Mbps)

PAM-10PAM-20

5

1. Issues with current proposals

6005004003002001000Freq. [MHz]

700 800

20

40

60

0

SNR [dB]

PAM20

PAM10

PAM5 Class-E 55m

Class-F 100m10

30

50

70

4D-PAM

6-dB coding gain included

6

2. OFDM Technique for 10GBASE-T

● Orthogonal Frequency Division Multiplexing (OFDM)– Special form of multi-carrier modulation– High spectral efficiency – Less sensitive to inter-symbol interference

● 7 PAM signals transmitted over 7 frequency-nonselective channels

● Required frequency bandwidth: 547 MHz + pilot signal● Symbol rate: 156.25 MHz (=10GHz/(4chx16bit))● Low latency: < 100 ns

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OFDMSignal

f1-I

f1-Q

f2-I

f2-Q

f3-I

f3-Q

Data Signals

f1 f2 f3156.25MHz 312.5MHz 468.75MHz

546.88MHz0 Freq.

Spectrum

2. OFDM Technique

Σ

OFDM technique distributes the data over a number of carriers that are spaced apart at precise frequencies. This spacing provides the "orthogonality" which prevents the demodulators from seeing frequencies other than their own.

8

2. Signaling in OFDM

01+12+23+3

4

Data bits

3468.75 MHz (I,Q)0

51020

PAM Level

625 MHzpilot signal

312.5 MHz (I,Q)156.25 MHz (I,Q)Base signal

Carrier Frequency

Total 16 bitsI: In-phase, Q: Quadrature-phase

156.25 MHz

I Q

312.5 MHz

I Q

468.75 MHz

I Q

Frequency: Base signal

9

2. SNR Margins

6005004003002001000Freq. [MHz]

700 800

20

40

60

0

SNR [dB]

(PAM20)

(PAM10)

(PAM3)

Class-E 55m

Class-F 100m10

30

50

70

(PAM5)

8dB

6dB

7dB

7dB

6-dB coding gain included

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DSP

2. Block Diagram

RJ45Hybrid

LineDriver

RxAmp.

AnalogFiltering

AnalogFiltering

DAC

ADC

OFDMDecoder

OFDMEncoder

Scrambler

De-scrambler

MACIF

ClockGeneratorClock

Detector

625MHz

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2. OFDM Modulation on DSP

● DSP processing on TX– 7 PAM signals (pi) are converted into 12 OFDM signals (xi,xpi,xni).– One symbol consists of 8 OFDM signals (xi).

tp7time

Symbol period (6.4 ns)x

−−−−−−−−−−

−−−−−

−−−−−

−−−−−

−−−−−−−−−

−−−−

=

ppppppp

xnxnxxxxxxxxxpxp

7

6

5

4

3

2

1

2

1

8

7

6

5

4

3

2

1

8

7

04.001.002.004.003.004.005.015.020.023.017.029.009.031.015.052.040.047.061.028.069.067.031.062.059.034.086.095.072.030.063.063.037.090.0130.072.063.063.090.037.0130.072.063.063.090.037.0172.030.063.063.037.090.0167.031.062.059.034.086.095.015.052.040.047.061.028.069.015.020.023.017.029.009.031.004.001.002.004.003.004.005.0

tp8 t1 t2 t3 t4 t5 t6 t7 t8 tn1 tn2

x1

x2

x3

x4 x5

x6

x7

x8

● RX can be handled in reverse fashion of TX. ● Major overhead of OFDM is only 20-ns matrix computation.

Low Latency

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2. Advantages of OFDM Method● OFDM achieves high spectral efficiency

– Required bandwidth is 547 MHz + pilot signal

● Slow symbol rate: 156.25 MHz– Inter-symbol interference is small

● Large noise margin: 6.1dB (with 6-dB coding gain)

● Latency: < 100 ns

● Add-on available: PAM-20,10,5, and 4D-PAM8

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3. Experimental Setup (1)

Hybrid

Cat-7 cable(100 m)

DataGenerator

EqualizerADCLogic

Analyzer

RX

TX

DAC

PLL: Waveform measured point

Hybrid

1-symbol and 1-channel data transmission

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Data GeneratorLogic Analyzer

CAT-7 Cable (100 m)

Testbed Board

3. Experimental Setup (2)

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3. Experimental Results (Waveform)

TX side RX side

156.25 MHz

I Q

312.5 MHzI Q

468.75 MHz

I Q


Clock jitter: < 20 ps (RMS)

156.25 MHz

I Q

312.5 MHzI Q

468.75 MHzI Q


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3. Experimental Results (DSP)

156.25 MHz

I Q

312.5 MHz

I Q

468.75 MHz


PAM Level

PAM Level PAM Level

PAM Level PAM Level

I QPAM Level PAM Level

6.4 ns

6.4 ns 6.4 ns 6.4 ns 6.4 ns

6.4 ns 6.4 ns

Inter-symbol interference is canceledSNR is measured

SNR: 32.1 dB

SNR: 31.9 dB SNR: 26.5 dB



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3. BER Estimation (1)

16SNR [dB]

20 24 28 32 3612 40

PAM20PAM10PAM8PAM5PAM3

without coding

468.75 MHz-Q 312.5MHz-Q

156.25MHz-Q

156.25MHz-I

Base signal

468.75 MHz-I 312.5MHz-I

1E-2

BER

1E-4

1E-6

1E-8

1E-10

1E-12

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1.2E-11< 1E-122.4E-10< 1E-128.5E-42.1E-113.0E-3BERwithout coding

18.8921.0824.3828.8126.4631.8532.09SNR (dB)

1

3

468.75 I-phase

3

10

156.25 Q-phase

12234AssignedNumber of bit

3551020PAM Level

468.75 Q-phase

312.5Q-phase

312.5 I-phase

156.25 I-phase

BaseSignal

CarrierFrequency(MHz)

Averaged BER without coding: 9.1E-4

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9.1x10-4

6dBCoding Gain

SNR [2dB/div]

1E-2BER

1E-4

1E-6

1E-8

1E-10

1E-14

1E-0

1E-12

BER < 10E-12with 6dB coding gain

WithCoding Gain

WithoutCoding Gain

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Conclusion

• OFDM method applied to 10GBASE-T– Required bandwidth: 547 MHz + pilot signal– Noise margin: 6.1 dB (with coding gain)– Low latency: < 100 ns

• Experimental result– 100-m data transmission with BER of < 1E-12

10gbase-t: a new proposal for improving pam performance with...

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