1. J. W. Kim and J.D.Cho 성균관대학교 http://vada.skku.ac.kr
Lower Power Equalizer
J. W. Kim and J.D.Cho
성균관대학교
SungKyunKwan Univ.

2. Low Power Equalizer Jin Woo Kim, J.D.Cho, 1999, SKKU Introduction
Low-Power Methodology in Equalizers
Simulation
Future Work
Reference
SungKyunKwan Univ.

3. Introduction – xDSL (Digital Subscriber Line)
Provide high bandwidth over copper twisted pair local loop cable, without amplifiers or repeaters
Utilize full potential of a copper telephone subscriber loop up to a few hundred times that of a voiceband modem
Support industry – standard transmission formats and bit rate such as T1 and E1
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4. Introduction – xDSL Channel Configuration
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5. DMT for ADSL ( Discrete MultiTone Modulation)
Built-in subchannel optimization
Ongoing active monitoring
Maximum loop variation coverage
Highest level of rate flexibility
Superior noise immunity for greater throughput
Broad industry chipset support
Interoperability through standards
Virtually future proof
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6. DMT SubChannel Allocation for ADSL
#1 ~ #6 : Analog Voice
#7 ~ #38 : Upstream Channels
#7 ~ #256 : Downstream Channels
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7. ADSL Block Diagram ( DMT )
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8. Equalizer – TEQ ( Time Domain Equalizer )
TEQ with a small number of taps can reduce the cyclic prefix(CP)
Power Consumption Critical Part
Adaptive FIR filters (LMS algorithm)
The Filter Output
The Filter Coefficient
The Error Signal
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9. Equalizer – Example of TEQ
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10. Equalizer – FEQ ( Frequency Domain Equalizer )
Compensate for the remaining frequency dependent attenuation and phase rotation of each subchannel
Complex One-Tap FIR filter per one subchannel (ADSL ; 256-7)
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11. Equalizer – Example of FEQ
LMS(Least Mean Square) Adaptive Filter
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12. Low Power Methodology in Equalizers – Circuit
FIR Filter
Carry-save adder
Grouped Multipliers(Wallace Tree Multiplier)
Booth Recoding technique
Updating Circuits
Power-of-two LMS updating
The use of register file
Coefficient freezing
Make step size constant(m) to power-of-2
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13. Low Power Methodology in Equalizers – Run-time
The Error Monitor
Adaptive Bit Precision
Burst-Mode Update
Adaptive Filter Length
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14. Low Power Methodology in Equalizers – Example
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15. Simulation – Environment (1)
Input Sequence
PRD(Pseudo Random Sequence) [T1E1.4]
Make 4-QAM symbols as Training Sequence
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16. Simulation – Environment (2)
Test Channel
CSA#6
26AWG(0.4mm)
9000ft(about 2.7Km)
AWGN noise environment
SNR 40dB
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17. Simulation – Channel ( Impulse Response )
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18. Simulation – Before Training ( Received constellation )
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19. Simulation – Before Training ( Coefficient constellation )
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20. Simulation – Before Training ( Output constellation )
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21. Simulation – After Training ( Output constellation )
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22. Simulation – Output SNR
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23. Simulation – Result Analysis
Step Constants(m) are power-of-2
0.5 -> ½ (2-1)
> 1/8 (2-3)
> 1/32 (2-5)
> 1/128 (2-7)
The smaller Constant, the longer convergence time
Replace Complex Multiplier to Just Exponent Adder
Low Power Consumption is acquired
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24. Simulation – Using HP ADS Schematic - Transceiver
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25. Simulation – Using HP ADS Schematic - Channel
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26. Simulation – Using HP ADS Schematic - Receiver
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27. Future Work (1) Simulation TEQ simulation NEXT, FEXT Channel Modeling
Attach Cyclic Prefix
Echo Canceller Simulation
Apply more Low-power Method
Apply Auto Bit Loading
Transmission Test to 215-QAM
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28. Future Work (2) Hardware Synthesis Implement FEQ in VHDL (Synopsys)
Implement TEQ in VHDL (Synopsys)
Apply Low-Power algorithm to EQ
Verify the function between Classical EQ and Low-Power EQ
Compare the power between Classical EQ and Low-Power EQ
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29. Future Work (3)
Current Simulation and Implementation model is for ADSL, but after improve the Speed and Power, I will apply all the algorithms to VDSL.
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30. Reference (1) W. Y. Chen, “DSL”, Macmillan Technical publishing, 1998
W. Goralski, “ADSL and DSL Technologies”, McGraw-Hill, 1998
K. Azadet et al, “Low-Power Equalizer Architectures for High-Speed modems”, IEEE Comm. Magazine, Oct. 1998
C. Nicol et al, “A Low-Power 128-Tap Digital Adaptive Equalizer for Broadband Modems”, IEEE jour. Of Solid-state Circuits, Nov. 1997
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31. Reference (2)
H. Lee et al, “A New Hardware-Efficient Architecture for Programmable FIR Filters”, IEEE Trans. On Circuits and Systems, Sep. 1996
J. Rinne et al, “Equalization of Orthogonal Frequency Division Multiplexing Signals”, Proc. Of GLOBECOM’94, pp , Nov 27, 1994
“DSP Solutions for Voiceband and ADSL Modems”, Texas Instrument, June, 1998
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