L40: Lower Power Equalizer

1. L40: Lower Power Equalizer J. W. Kim and J.D.Cho 성균관대학교 http://vada.skku.ac.kr SungKyunKwan Univ.

2. Low Power Equalizer • Jin Woo Kim, J.D.Cho, 1999, SKKU • Introduction • Equalizer • 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 SungKyunKwan Univ.

4. Introduction – xDSL Channel Configuration SungKyunKwan Univ.

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 SungKyunKwan Univ.

6. DMT SubChannel Allocation for ADSL • #1 ~ #6 : Analog Voice • #7 ~ #38 : Upstream Channels • #7 ~ #256 : Downstream Channels SungKyunKwan Univ.

7. ADSL Block Diagram ( DMT ) SungKyunKwan Univ.

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 SungKyunKwan Univ.

9. Equalizer – Example of TEQ SungKyunKwan Univ.

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) SungKyunKwan Univ.

11. Equalizer – Example of FEQ • LMS(Least Mean Square) Adaptive Filter SungKyunKwan Univ.

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 SungKyunKwan Univ.

13. Low Power Methodology in Equalizers – Run-time • The Error Monitor • Adaptive Bit Precision • Burst-Mode Update • Adaptive Filter Length SungKyunKwan Univ.

14. Low Power Methodology in Equalizers – Example SungKyunKwan Univ.

15. Simulation – Environment (1) Input Sequence PRD(Pseudo Random Sequence)[T1E1.4] Make 4-QAM symbols as Training Sequence SungKyunKwan Univ.

16. Simulation – Environment (2) • Test Channel • CSA#6 • 26AWG(0.4mm) • 9000ft(about 2.7Km) • AWGN noise environment • SNR 40dB SungKyunKwan Univ.

17. Simulation – Channel ( Impulse Response ) SungKyunKwan Univ.

18. Simulation – Before Training( Received constellation ) SungKyunKwan Univ.

19. Simulation – Before Training( Coefficient constellation ) SungKyunKwan Univ.

20. Simulation – Before Training( Output constellation ) SungKyunKwan Univ.

21. Simulation – After Training( Output constellation ) SungKyunKwan Univ.

22. Simulation – Output SNR SungKyunKwan Univ.

23. Simulation – Result Analysis • Step Constants(m) are power-of-2 • 0.5 -> ½ (2-1) • 0.125 -> 1/8 (2-3) • 0.03125 -> 1/32 (2-5) • 0.007125 -> 1/128 (2-7) • The smaller Constant, the longer convergence time • Replace Complex Multiplier to Just Exponent Adder • Low Power Consumption is acquired SungKyunKwan Univ.

24. Simulation – Using HP ADSSchematic - Transceiver SungKyunKwan Univ.

25. Simulation – Using HP ADSSchematic - Channel SungKyunKwan Univ.

26. Simulation – Using HP ADSSchematic - Receiver SungKyunKwan Univ.

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 SungKyunKwan Univ.

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 SungKyunKwan Univ.

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. SungKyunKwan Univ.

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 SungKyunKwan Univ.

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. 415-419, Nov 27, 1994 • “DSP Solutions for Voiceband and ADSL Modems”, Texas Instrument, June, 1998 SungKyunKwan Univ.