ieee 802.3ap proposal to use pr-4 signaling for 10gbase-kr...
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Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
IEEE 802.3ap
Proposal to use PR-4 Signaling
for 10Gbase-KR links
IEEE 802.3ap Task ForceJan’05
Michael Altmann, Fulvio Spagna, Jun Wang
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 2
Objectives
� Propose a PR-4 based signaling solution for 10Gbase-KR signaling on backplanes
� Allows leveraging signaling techniques & experience from the storage industry
� PR4 signaling can acceptably equalize typical BP channels� Simulation results will be shown
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 3
Agenda
� Layer Model� Proposal Overview� Link Model� PR-4 Signaling� AN and Link training� PR-4 simulation results
� Adaption simulations
� MMSE-optimized eye diagrams
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 4
IEEE802.3ap Layer Model
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 5
Overview
� Use PR-4 signaling for 10Gb serial BP channels� PR-4 has spectrum & implementation advantages
� Requires pre-coding to limit error propagation
� Use existing 802.3 clauses for other functions:� PCS (clause 49)
� PMA (clause 51)
� MDIO (clause 45)
� Auto-Negotiation (clause 28)� Possible signaling modifications as in brink_01_1104.pdf or
thaler_01_1104.pdf)
� Programmable Tx and Rx equalization optimized with training
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 6
PR-4 Signaling - Background
� Used extensively in disk drive industry� Equalized systems use non-unity target polynomial
0 0.5 1 1.5 2 2.5 3
x 1010
0
10
20
30
40
50
60
70
Line code=nrz
Freq [Hz]
Spe
ctra
l Pow
er [d
bmW
/Hz]
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
x 10-10
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2Filtered Eye Diag
Time [s]
[V]
0 0.5 1 1.5 2 2.5 3
x 1010
0
10
20
30
40
50
60
70
Line code=pr4
Freq [Hz]
Spe
ctra
l Pow
er [d
bmW
/Hz]
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
x 10-10
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2Filtered Eye Diag
Time [s]
[V]
PR4: Y=(1-D2)XNRZ: Y=X
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 7
PR-4 Signaling - Background
� Multi-level encoding� 2-level NRZ becomes 3-level PR-4 encoded data at Rx� Adds coding redundancy which alters the spectrum
� Nulls at DC and fbit/2� True Nyquist channel possible for minimum noise� Encoding mechanism is combination of Tx Eq, channel, Rx
AFE and Eq
� ‘Allowable’ ISI reduces equalization boost from NRZ� See ‘altmann_02_0904.pdf’
� Zero crossing between +1, -1 pulses is an excellent timing indicator� Enables baud-rate Rx design� Reduces sampler complexity by 50%
� PR-4 requirements� Requires both Tx and Rx equalization
� Tx pre-coding to limit error propagation
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 8
PR-4 Signaling
� Data encoding requirements� Tx pre-coding not explicitly required, however it eliminates error
prpoagation from incorrectly decoded bits
� Data Decoding options� Can use bit-by-bit or optional MLSE (ex. Viterbi) detection
� Receiver can operate at half-rate, as data stream is intrinsically interleaved
� Both decoding methods requires a pre-coder to eliminate error propagation.
� PR-4 Pre-coder
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 9
PR-4 Signaling vs NRZ
� Controlled ISI creates 3-level eye diagram� In BW-limited channels, eye height reduces slower than NRZ� Jitter is higher due to direct +1 →→→→ -1 transitions
0 20 40 60 80 100 120 140 160 180 200-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5Data & clock response: f0=7.5GHz
Filtered NRZ Eye: ωωωω0=7.5GHz Filtered PR-4 Eye: ωωωω0=7.5GHz
0 20 40 60 80 100 120 140 160 180 200-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5Data pattern & clock response: fr=750m
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 10
Link Model (from brink_01_1104.pdf)
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 11
Auto-Negotiation & Eq Training
� AN and link training required� AN will exchange PHY capabilities and determine bit-rate
� Follow method similar to thaler_01_1104.pdf or brink_01_1104.pdf
� Timing Acquisition� Initial timing acquisition using ¼-rate signal: +1 +1 -1 -1
(approx a clk at PR4 spectral peak) before equalization� Rx signal is approximate sine wave� Final timing acquisition using simple (TBD) known data
patterns
� Equalizer training� Initial equalizer training can occur using (TBD) training
sequences (altmann_02_1105.pdf)� Optimal (TBD) training sequence will be defined for faster
PR4 adaption
� After link training, equalizers continuously update with active traffic
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 12
PR-4 Equalizer Adaption Simulations
� Simulated results for channels equalized to PR-4 target polynomial
� Initial Eq estimate provided from channel response� Substitute for training sequence adaption
� Simulation conditions� Data Pattern: PRBS15, 100kbit sim time
� NEXT/FEXT: off
� Tx Pulse shaping: 4th Order Bessel Filtering
� Rx Noise Filtering: None
� Tx Eq: 8 tap FIR, 10b coeffs
� Rx Eq: 5 tap DFE, 10b coeffs
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 13
PR-4 Equalization Simulations – Tyco Case 5
0 500 1000-2
-1
0
1
2Tx EQ coeffs
0 500 1000-0.5
0
0.5
1
1.5Rx EQ coeffs
0 500 1000-0.06
-0.04
-0.02
0Normalized Sampling Phase
0 500 1000
0.5
0
0.5
Sampler Eye Diagram
0 500 1000-0.5
0
0.5Sampler Error
-2 0 2 4 6-1
0
1
2Tx EQ final coeffs
0 2 4 6-0.5
0
0.5
1Rx DFE final coeffs
Channel model: tyco: Case5_DS_13_10_T_D13_L6
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 14
PR-4 Adaptive Eqn Sims – Intel T32
0 500 1000-5
0
5Tx EQ coeffs
0 500 1000-1
-0.5
0
0.5Rx EQ coeffs
0 500 100-0.1
0
0.1Normalized Sampling Phase
0 500 1000
0.5
0
0.5
Sampler Eye Diagram
0 500 1000-0.5
0
0.5Sampler Error
-2 0 2 4 6-5
0
5Tx EQ final coeffs
0 2 4 6-1
-0.5
0
0.5Rx DFE final coeffs
Channel model: Intel T32
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 15
PR-4 Equalization Simulations – Eye Diagrams
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
-1
-0.5
0
0.5
1
X: 0.7188Y: 0.2558
X: 0.5045Y: 0.4376
X: 0.3007Y: 0.27
X: 0.5056Y: 0.08217
Tyco Case5 PR4 equalized Eye
Time [UI]
Sam
pler
Vol
tage
[V]
'-1' Lower'-1' Upper'0' Lower'0' Upper'+1' Lower'+1' Upper
Data: PRBS15Tx Eq: 7T FIRRx Eq: 5T DFETR: Data-Directed Sign-Sign
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
-1
-0.5
0
0.5
1
X: 0.3468Y: 0.2386
X: 0.501Y: 0.3983
X: 0.6518Y: 0.26
X: 0.5053Y: 0.1146
Intel T32 PR4 equalized Eye
Time [UI]
Data:PRBS15Tx Eq: 7T FIRRx Eq: 5T DFETR: Data-Directed Sign-Sign
0.355
0.205
Eye Height
[V]
0.691 0.418 Tyco Case #5
0.205 0.154Intel T32
Max NEXT/FEXT
[Vp-p]
Eye width[UI]
Channel
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-0.02
-0.015
-0.01
-0.005
0
0.005
0.01
0.015
0.02X: 0.8438Y: 0.01975
Worst-Case NEXT/FEXT at sampler vs phase
Time [UI]
Sam
pler
Vol
tage
[V]
X: 0.4688Y: -0.01872
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 16
PR-4 Simulation Summary
� Simulation conditions:� Noise filter: 2nd order linear filter ωωωω0=6GHz & 10GHz
� NEXT/FEXT & noise: None
� Fixed coefficients, post-MMSE adaption
� Linear tap values (no quantization)
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 17
PR-4 Simulation Summary
Intel B12 Intel M12 Intel T12 Intel B8
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 18
PR-4 Simulation Summary
Intel M8 Tyco Case #1 Tyco Case #5
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 19
PR-4 Simulation Summary – Eye Parameters
0.506 0.315 Case #1
Intel Channels (Peters)
0.691 0.375 Case #2
Tyco Channels (D’Ambrosia)
0.288 0.261 Intel M8
0.343 0.264 Intel B8
0.205 0.154Intel T12
0.341 0.277Intel M12
0.461 0.314Intel B12
Eye Height[V]
Eye width[UI]
Channel
Michael AltmannIEEE 802.3ap Task Force - 21-Jan-05
Slide 20
Summary
� Presented a PR-4 signaling proposal for 10Gbase-KR� Leverages existing clauses for PCA, PMA and MDIO� Leverages known PR-4 implementation advantages� Includes Tx (FIR) and Rx (DFE) adaptive equalization� Successful adaption simulations shown� Successfully equalizes a range of Tyco and Intel
(ATCA) backplanes
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