1 / 18

On the Relation Between Time-Domain Equalizers and Per-Tone Equalizers for DMT-Based Systems

On the Relation Between Time-Domain Equalizers and Per-Tone Equalizers for DMT-Based Systems. Koen Vanbleu, Geert Ysebaert, Gert Cuypers, Marc Moonen Katholieke Universiteit Leuven, ESAT / SCD-SISTA, Belgium. IEEE Benelux Signal Processing Symposium Hilvarenbeek, the Netherlands.

padma
Download Presentation

On the Relation Between Time-Domain Equalizers and Per-Tone Equalizers for DMT-Based Systems

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. On the Relation Between Time-Domain Equalizers and Per-Tone Equalizers for DMT-Based Systems Koen Vanbleu, Geert Ysebaert, Gert Cuypers, Marc Moonen Katholieke Universiteit Leuven, ESAT/SCD-SISTA, Belgium IEEE Benelux Signal Processing Symposium Hilvarenbeek, the Netherlands April 16, 2004

  2. On Equalization Alternatives and their Relations for ADSL Modems Koen Vanbleu, Geert Ysebaert, Gert Cuypers, Marc Moonen Katholieke Universiteit Leuven, ESAT/SCD-SISTA, Belgium IEEE Benelux Signal Processing Symposium Hilvarenbeek, the Netherlands April 16, 2004

  3. Overview • ADSL Basics • What? Multicarrier modulation • Transmitter/Receiver • ADSL Equalizer Design • Problem Description • Current Equalizers (TD-MMSE) • Bit rate Maximizing Equalizers (FD-MMSE criterion) • Relations

  4. Introduction Downstream Central Customer Upstream • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • - Relations Broadband communication over telephone line • ADSL (Asymmetric Digital Subscriber Line) • ADSL2 / ADSL2+ (Second-Generation ADSL) • VDSL (Very high bit rate Digital Subscriber Line) • Bit rate is function of the line length

  5. Multicarrier Modulation POTS UP DOWN 4 25 138 1104 f (kHz) • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • - Relations • Digital multicarrier modulation scheme: Discrete Multitone (DMT) • Assign different frequency bins to up- and downstream directions e.g. ADSL • Traditional telephony (POTS) still available over the same wire.

  6. Discrete Multitone: Transmitter bits Data symbols (QAM) Cyclic Prefix Im 0 10 00 CP ... ... Re 11 01 2 bits N-point Im IDFT P/S Re ... ... 4 bits IDFT modulation (Inverse Discrete Fourier Transform) • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • - Relations Block transmission!

  7. Why Equalization? noise channel ... • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • - Relations CP ... ... N-point P/S IDFT Why equalization? “Invert” channel distortion while not boosting noise ... Transmitter

  8. Discrete Multitone: Receiver Frequency Domain Equalizer 1 tap / tone Data symbols Im bits 10 00 CP ... x Re 11 01 x 2 bits ... Im TEQ w S/P x Re Time Domain Equalizer taps 4 bits CP length + 1 • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • - Relations noise ... channel h N-point DFT DFT demodulation

  9. DMT Equalization: Problem Description CP Residual ISI/ICI where Noise (RFI/XT/etc.) • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • - Relations Im 10 00 Re T taps 1 tap/tone N-point 11 01 TEQ w ... ... ... S/P FEQ FEQ DFT 2 bits To maximize bit rate: is hard with time-domain equalizer w

  10. Current ADSL Equalizers noise Channel h TEQ w - delay TIR b TIR = target impulse response of (CP-length+1) CP length + 1 • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • - Relations Channel shortenerse.g. time-domain MMSE-TEQ design Constrained linear least-squares based MMSE-TEQ No bit rate optimization!

  11. Bit rate Maximizing Equalizers:Per-tone equalization x x ... . . . . . . N-point x DFT taps FEQ TEQ w • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • Per-tone equalization • BM-TEQ - Relations Time Domain Equalizer

  12. Bit rate Maximizing Equalizers:Per-tone equalization S/P ... ... ... PTEQ ... sliding N-point DFT T –tap linear combiner w for each tone N-point ... ... DFT n • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • Per-tone equalization • BM-TEQ - Relations

  13. Bit rate Maximizing Equalizers:Per-tone equalization • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • Per-tone equalization • BM-TEQ - Relations • Least-squares criterion per tone: “design TEQ per tone” • Optimizes the SNR per tone •  Performs always better than a TEQ • Efficient computation: exploit sliding DFT structure •  similar complexity as TEQ

  14. Bit rate Maximizing (BM) Equalizers:Time-domain equalization where PTEQ: CP BM-TEQ: with T taps FEQ N-point x TEQ ... ... ... S/P DFT x • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • Per-tone equalization • BM-TEQ - Relations

  15. Bit rate Maximizing Equalizers:Time-domain equalization • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • Per-tone equalization • BM-TEQ - Relations with Iteratively-reweighted separable non-linear least squares-based frequency-domain MMSE-TEQ design

  16. Relation between ADSL equalizers Block transmission/CP/Multicarrier FD-MMSE-TEQ: constrained linear LS or separable NL-LS Bit rate maximization BM-TEQ: iteratively reweighted separable NL-LS Only 1 tone PTEQ: linear LS • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • - Relations (Channel shortening) TD-MMSE-TEQ: constrained linear LS Remarkable correspondence between generalized eigenvalue problems

  17. Relation between ADSL equalizers • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • - Relations TD-MMSE-TEQ Real FD-MMSE-TEQ 1 Complex FD-MMSE-TEQ 1 Real FD-MMSE-TEQ 2 Complex FD-MMSE-TEQ 2 Real BM-TEQ Complex BM-TEQ Real PTEQ Complex PTEQ

  18. Relation between ADSL equalizers • ADSL Basics • - Intro • - DMT Transmitter • - Why Equalization? • - DMT Receiver • ADSL Equalizer Design • - Problem Description • - Current Equalizers • - Bit rate Maximizing • Equalizers • - Relations (Channel shortening) TD-MMSE-TEQ: constrained linear LS Block transmission/CP/Multicarrier FD-MMSE-TEQ: constrained linear LS or separable NL-LS Bit rate maximization BM-TEQ: iteratively reweighted separable NL-LS Only 1 tone Remarkable correspondence between generalized eigenvalue problems PTEQ: linear LS

More Related