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Teranetics Proprietary Berkeley Presentation
Low BER (<10-12) and FER (<10-9)
Power: First generation <9W
Distance
1/19/2007 Page 4
Cable Noise
Self Noise:
1/19/2007 Page 3 Teranetics Proprietary Berkeley Presentation
Main Features
Low Latency (<2 microsecs)
Mostly budgeted for DSP functions Limits the code length Industry requirement: < 10-15 Practically no error floor A challenge for validation Limits the decoding complexity Good coverage on installed base (<55m) 100% coverage on improved cable(<100m) Small Gap to Capacity
THP:
Standard selected the THP approach
Teranetics Proprietary Berkeley Presentation
1/19/2007 Page 12
Binary Code: Regular vs Irregular
Regular Codes:
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Teranetics Proprietary
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Djurdjevic LDPC (2048, 1723)
Adopted by the IEEE Standard Based on RS(32, 2, 31) Check node degree = 32 Bit node degree = 6 Size of the permutation blocks = 64 Binary code about 2 dB away from Shannon bound around 10-12 Estimated overall latency about 640 nsec at 800 MHz symbol rate
Irregular Codes:
Standard decided to use regular codes
Teranetics Proprietary Berkeley Presentation
1/19/2007 Page 13
LDPC Codes based on RS Codes
Directly from:
Return Loss
Remote Transceiver
Attenuation reduces signal to be detected Near end Cross talk (NEXT) interferes with detection Far end cross talk (FEXT) interferes with detection Alien cross talk interferes with detection
Construction and Implementation of the LDPC Coding Scheme for 10G bits/sec Ethernet over Twisted Pair
Dariush Dabiri, Ph.D. Chief Systems Scientist Teranetics, Inc.
PLL Jitter:
Power:
Capacity:
Coding Gain:
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Teranetics Proprietary
Berkeley Presentation
Arriving at the DSQ Modulation
Only Two Levels considered: Uncoded and Coded Focused on the extended class of the Euclidean Geometry Code for the binary code A range of symbol rates from PAM capacity A discrete set of symbol rates from PLL jitter Lower bounds on code rate from:
Teranetics Proprietary
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AFE Noise
Thermal Noise:
Non-cancellable, i.e. requires coding gain Partially cancellable, still requires coding gain It depends on the peak power Only at low frequencies cancellable, i.e. requires coding gain Signal depenent System Requirements 10G-BaseT Architecture Coded Modulation LDPC Code Decoder Architecture Performance Validation Open Problems
I. Djurdjevic, et al. IEEE Communication Letter, pp. 317-319, Vol. 7, No. 7, July 2003
It is a regular LDPC code It can be constructed from the class of LDPC codes based on Euclidean Geometry (I. Djurdjevic, Ph.D. Thesis UC-Davis). The H matrix is in the form of blocks of permutation matrices.
Teranetics Proprietary Berkeley Presentation
1/19/2007 Page 8
Metrics for Coded Modulation
Latency:
Limits the code length Only certain symbol rates are allowed Symbol rate and code rate dependent Depends on symbol rate Code construction and coding rate dependent
Teranetics Proprietary Berkeley Presentation
1/19/2007 Page 10
DSQ
Its points are on the two dimensional checkerboard lattice. It is a 45° rotation of the 128-cross constellation, therefore it contains exactly 128 points. A per dimension Ungerboeck set partitioning of the 128-cross constellation 12 dB separation in the set partitioning:
Channel Constraints:
EMI/EMC Requirements Limited by the linearity of the AFE For the most part dominates the average power requirement.
Peak Power:
PAM signaling is optimum!
Echo:
Cancelled by DSP (>50 dB) Cancelled by DSP (>40 dB) Cancelled by DSP (>20 dB)
NEXT:
FEXT:
External Noise:
Alien Cross Talk
Non-cancellable, i.e. requires coding gain Non-cancellable, i.e. requires coding gain
The class of binary code Complexity of the decoder
Depth of the set partitioning upper bounded by the raw coding gain Alternatives with similar performance (PAM12, PAM8)
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Teranetics Proprietary
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The UTP Cable environment
2500 Mb/s Full Duplex for 10G
NEXT
FEXT
Local Transceiver
EMI Alien crosstalk
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Teranetics Proprietary
Berkeley Presentation
ISI: Precoding or DFE?
DFE:
4bit DAC Slightly lower PAR (~ 1dB) Error propagation or combined equalization/decoding 10~12 bit DAC Slightly more PAR Decoupled equalization from coding