Download presentation

Presentation is loading. Please wait.

Published byLandyn Sultan Modified over 2 years ago

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 April 16, 2004 IEEE Benelux Signal Processing Symposium Hilvarenbeek, the Netherlands

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

3
3Overview 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
4Introduction Communication at high rates towards customer telephone wire, cable, fiber, wireless Communication over telephone wire Evolution: ever increasing bit rates E.g. Time to download 10 Mbyte file ModemTime 56 Kbps Voice band modem 24 minutes 128 Kbps ISDN10 minutes 6 Mbps ADSL13 seconds 52 Mbps VDSL1.5 seconds ADSL Basics - Intro - DMT Transmitter - Why Equalization? - DMT Receiver ADSL Equalizer Design - Problem Description - Current Equalizers - Bit rate Maximizing Equalizers - Relations

5
5Introduction 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 Upstream Downstream CustomerCentral ADSL Basics - Intro - DMT Transmitter - Why Equalization? - DMT Receiver ADSL Equalizer Design - Problem Description - Current Equalizers - Bit rate Maximizing Equalizers - Relations DownUpLine lengthFrequency band ADSL6 Mbps640 kbps3.7 km1.1 MHz ADSL2+15 Mbps1.5 Mpbs1.8 km2.2 MHz VDSL52 Mbps2.3 Mbps< 1 km12 MHz

6
6 Traditional telephony (POTS) still available over the same wire. Multicarrier Modulation Assign different frequency bins to up- and downstream directions f (kHz) POTSUPDOWN 4251381104 e.g. ADSL Digital multicarrier modulation scheme: Discrete Multitone (DMT) ADSL Basics - Intro - DMT Transmitter - Why Equalization? - DMT Receiver ADSL Equalizer Design - Problem Description - Current Equalizers - Bit rate Maximizing Equalizers - Relations

7
7 Discrete Multitone: Transmitter... P/S CP Cyclic Prefix ADSL Basics - Intro - DMT Transmitter - Why Equalization? - DMT Receiver ADSL Equalizer Design - Problem Description - Current Equalizers - Bit rate Maximizing Equalizers - Relations 00 11 10 01 Re Im 2 bits Re Im 4 bits bitsData symbols (QAM) 0 IDFT N -point............... IDFT modulation (Inverse Discrete Fourier Transform) Block transmission!

8
8 Why Equalization? channel noise... P/S CP IDFT N -point............... Transmitter Why equalization? “Invert” channel distortion while not boosting noise ADSL Basics - Intro - DMT Transmitter - Why Equalization? - DMT Receiver ADSL Equalizer Design - Problem Description - Current Equalizers - Bit rate Maximizing Equalizers - Relations

9
9 Discrete Multitone: Receiver 00 11 10 01 Re Im 2 bits Re Im 4 bits bits Data symbols channel h noise ADSL Basics - Intro - DMT Transmitter - Why Equalization? - DMT Receiver ADSL Equalizer Design - Problem Description - Current Equalizers - Bit rate Maximizing Equalizers - Relations CP length + 1... S/P CP...... DFT N -point DFT demodulation...... Frequency Domain Equalizer 1 tap / tone x x x TEQ w taps Time Domain Equalizer

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

11
11 Current ADSL Equalizers ADSL Basics - Intro - DMT Transmitter - Why Equalization? - DMT Receiver ADSL Equalizer Design - Problem Description - Current Equalizers - Bit rate Maximizing Equalizers - Relations Channel shorteners e.g. time-domain MMSE-TEQ design Channel h noise No bit rate optimization! CP length + 1 TEQ w Constrained linear least-squares based MMSE-TEQ TIR = target impulse response of (CP-length+1) delay TIR b -

12
12 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 DFT N -point TEQ w taps Time Domain Equalizer...... x x x FEQ............

13
13 Bit rate Maximizing Equalizers: Per-tone equalization S/P... DFT N -point DFT N -point sliding PTEQ... 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 n T –tap linear combiner w for each tone

14
14 Bit rate Maximizing Equalizers: Per-tone equalization 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 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
15 Bit rate Maximizing (BM) 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 PTEQ: where BM-TEQ: with TEQ S/P CP... DFT FEQ T taps... N -point x x

16
16 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

17
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 (Channel shortening) TD-MMSE-TEQ: constrained linear LS FD-MMSE-TEQ: constrained linear LS or separable NL-LS Block transmission/CP/MulticarrierBit rate maximization BM-TEQ: iteratively reweighted separable NL-LS PTEQ: linear LS Only 1 tone Remarkable correspondence between generalized eigenvalue problems

18
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 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

19
19 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 FD-MMSE-TEQ: constrained linear LS or separable NL-LS Block transmission/CP/Multicarrier Bit rate maximization BM-TEQ: iteratively reweighted separable NL-LS PTEQ: linear LS Only 1 tone Remarkable correspondence between generalized eigenvalue problems

Similar presentations

Presentation is loading. Please wait....

OK

Digital Subscriber Line (DSL)

Digital Subscriber Line (DSL)

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on social networking dangers Ppt on spirituality in daily life Ppt on statistics in maths what does median Ppt on excessive use of chemicals in our daily life Ppt on life study of mathematician blaise Ppt on product specification meaning Ppt on end of life care Ppt on census 2001 people Ppt on obesity and overweight Download ppt on c#