lecture dsl

Information about lecture dsl

Published on December 1, 2007

Author: Olivier

Source: authorstream.com

Content

Case Study ADSL Modems:  Case Study ADSL Modems Geert Leus Fac. EEMCS, TUDelft [email protected] ADSL Modems:  ADSL Modems Overview ADSL (VDSL) modems Modem technology : voice-band vs. xDSL Communication impairments (...call for DSP solutions) Equalization Echo Cancellation ADSL (VDSL) Modems:  ADSL (VDSL) Modems References: J.A.C. Bingham, `The theory and practice of modem design’, Wiley, 1980 J.A.C. Bingham, `Multicarrier modulation for data transmission, an idea whose time has come’, IEEE Communications Magazine, May 1990, pp.5-14 W.Y. Chen, `DSL simulation techniques and standards development for digital subscriber line systems’, Macmillan, 1998 ... ADSL (VDSL) Modems:  ADSL (VDSL) Modems Modem Technology : …-1970 : development of efficient modulation techniques for transmission over band limited channels, spurred by military applications (-> … 9.6 kbits/sec) 1970-1980 : Semiconductor technology (size & power reduction) 1980-1990 : Introduction of coding techniques (-> … 19.2 kbits/sec) 1990-2000 : reaching Shannon limit (-> 33kbits/sec, asymmetric 56kbits/sec modems) 1995-… : ADSL (8Mbits/sec downstream, 60 kbits/sec upstream) 2000-… : VDSL (52Mbits/sec downstream, 6Mbits/sec upstream), ... ADSL (VDSL) Modems:  ADSL (VDSL) Modems Performance improvement results from: improved telephone channel quality (digital switches, etc.) improved modulation/coding/DSP techniques (QAM, trellis coded modulation (TCM), echo cancellation (EC), adaptive equalization,…) semiconductor technology 1972 1976 1984 1989 1996 4.8kbits/sec (V.27) 9.6kbits/sec (V.29) 9.6kbits/sec (V.32) 19.2kbits/sec (V.33b) 33.6kbits/sec (V.34) 8-PSK 16-QAM 32-QAM/TCM 64-QAM/TCM 128-QAM/TCM simplex simplex EC-duplex EC-duplex EC-duplex ADSL (VDSL) Modems:  ADSL (VDSL) Modems PS: duplexing techniques Frequency division duplexing (FDD) `downstream’ = central office -> remote user `upstream’ = remote user -> central office Time division duplexing (TDD) : `ping-pong’ Full duplex with echo-cancellation (EC) up down frequency up down time up & down time & frequency ADSL (VDSL) Modems:  ADSL (VDSL) Modems ADSL : `Asymmetric Digital Subscriber Line’ …-1993: ADSL spurred by interest in video-on-demand (VOD) 1995 : ADSL/VOD interest decline 1996 : ADSL technology trials prove viability. 1997-... : ADSL deployment, reoriented to data applications, as telco’s reaction to cable operators offering high- speed internet access with cable modems. ADSL (VDSL) Modems:  ADSL (VDSL) Modems ADSL : `Asymmetric Digital Subscriber Line’ VDSL : `Very High Speed Digital Subscriber Line’ Backbone Network Access Node max 0.3…1.5 km cabinet (ONU) optical fiber copper wire copper wire ADSL (VDSL) Modems:  ADSL (VDSL) Modems Distance/bitrate trade-off (upstream) distance (km) 1 2 3 4 10 20 30 40 bitrate (Mbits/sec) ADSL VDSL ADSL (VDSL) Modems:  ADSL (VDSL) Modems Communication Impairments : Frequency-dependent cannel attenuation introduces inter-symbol interference (ISI) EM coupling between wires in same or adjacent binders introduces crosstalk Near-end Xtalk (NEXT) = US into DS, DS into US Far-end Xtalk (FEXT) = DS into DS, US into US ADSL (VDSL) Modems:  ADSL (VDSL) Modems Communication Impairments : ADSL (VDSL) Modems:  ADSL (VDSL) Modems Communication Impairments (continued) : Xtalk from other systems e.g. HPNA (Home Phone Network Alliance) vs. VDSL Radio Frequency Interference (RFI) e.g. AM broadcast, amateur radio Noise e.g. impulsive noise (=high bursts of short duration) Echo due to hybrid impedance mismatch Conclusion: Need advanced modulation, DSP,etc. ! ADSL (VDSL) Modems:  ADSL (VDSL) Modems Line Codes (modulation technique) : ADSL (ANSI standard) DMT (`Discrete Multi-tone Modulation’, a.k.a. multi-carrier modulation, orthogonal frequency division multiplexing (OFDM)) 256 different `carriers’, each of them QAM-modulated, see below. VDSL DMT or single carrier (CAP/QAM) systems ? =undecided.. ADSL (VDSL) Modems:  ADSL (VDSL) Modems Line Codes (modulation technique) : DMT: Multiple carriers are QAM-modulated with a low-rate bit stream. The high-rate bit stream is thus carried by dividing it into hundreds of low-rate streams. Modulation/demodulation by FFT/IFFT (see below) ADSL (VDSL) Modems:  ADSL (VDSL) Modems ADSL/VDSL Specs:  ADSL/VDSL Specs ADSL specs (=ANSI standard) 256 carriers 512-point (I)FFT’s (or `similar’) prefix length = 32 carrier spacing fo= 4.3215 kHz basic sampling rate is 2.21 MHz (=512*4.3215k) VDSL specs (=proposal) up to 4096 carriers same carrier spacing etc. ADSL/VDSL Spectrum:  ADSL/VDSL Spectrum ADSL spectrum : Equalization:  Equalization Problem Statement : ISI/ICI-free transmission if prefix length >= L-1 L is channel impulse response length In ADSL : prefix-length is 32 samples channel length is….500 samples (approx.) !!! Solution : Insert time-domain equalizer for channel shortening Equalization:  Equalization ps: standard (zero-forcing) equalization means `shortening to 1 non-zero tap’ (cfr. C(f).H(f)=1) ps: complexity ! Example: 32 taps @ 2.2 MHZ -> 70 Mflops... Equalization:  Equalization Echo Cancellation:  Echo Cancellation Problem Statement : ADSL with overlapping up- and downstream bands requires echo cancellation (adaptive filter) Main problem = complexity example : echo path with 500 taps @ 2.2 MHz -> ...Gflops Conclusion:  Conclusion Advanced features in ADSL/VDSL systems - DMT modulation, prefix trick & co - Equalization - Echo Cancellation - (Windowing) - etc… Confirms importance of digital signal processing techniques in present-day high-performance communication systems

Related presentations


Other presentations created by Olivier

Ext
20. 11. 2007
0 views

Ext

On the road to Basel II For TBA
28. 11. 2007
0 views

On the road to Basel II For TBA

9 3 Karan Gosal
28. 11. 2007
0 views

9 3 Karan Gosal

Health topics
03. 12. 2007
0 views

Health topics

relaxation
05. 12. 2007
0 views

relaxation

2007 LFA Health Fair
12. 12. 2007
0 views

2007 LFA Health Fair

fair housing presentation nov05
05. 11. 2007
0 views

fair housing presentation nov05

jesiennagra
05. 11. 2007
0 views

jesiennagra

FÃrderprogramme
16. 11. 2007
0 views

FÃrderprogramme

Teori
21. 11. 2007
0 views

Teori

ADSL Africa
26. 11. 2007
0 views

ADSL Africa

Extinction shot
15. 11. 2007
0 views

Extinction shot

sleep ppt 2 0606revised
29. 11. 2007
0 views

sleep ppt 2 0606revised

pescosolido
02. 01. 2008
0 views

pescosolido

FIRA ROBOCUP
07. 01. 2008
0 views

FIRA ROBOCUP

tunnel hepap
10. 12. 2007
0 views

tunnel hepap

Turkey Organic Agriculture
23. 11. 2007
0 views

Turkey Organic Agriculture

Lubchenco Sciences Sine QuaNon
04. 01. 2008
0 views

Lubchenco Sciences Sine QuaNon

2007 09 28 mm course intro
27. 02. 2008
0 views

2007 09 28 mm course intro

symposium abate
31. 12. 2007
0 views

symposium abate

UMS Status Brief 6 29 06 Rev
28. 02. 2008
0 views

UMS Status Brief 6 29 06 Rev

Final Fall 06
04. 01. 2008
0 views

Final Fall 06

HTM402 StatsJan08 Final
11. 03. 2008
0 views

HTM402 StatsJan08 Final

StarAllianceForum
14. 03. 2008
0 views

StarAllianceForum

SJPresentation
18. 03. 2008
0 views

SJPresentation

AAC May05 Funk
04. 01. 2008
0 views

AAC May05 Funk

india siewhoon06
30. 03. 2008
0 views

india siewhoon06

sustainability cohen
13. 04. 2008
0 views

sustainability cohen

ETI 11SoftLivre
05. 11. 2007
0 views

ETI 11SoftLivre

haloween
05. 11. 2007
0 views

haloween

FUENTES DIGITALES
15. 11. 2007
0 views

FUENTES DIGITALES

dyna202 5512
02. 11. 2007
0 views

dyna202 5512

albania presentation 10 30
02. 10. 2007
0 views

albania presentation 10 30

Industrie de la recommandation
20. 03. 2008
0 views

Industrie de la recommandation

Evaluation CM2
26. 01. 2009
0 views

Evaluation CM2

ihp 7th phase
23. 11. 2007
0 views

ihp 7th phase

Montaigu web-ouvert-def
30. 03. 2015
0 views

Montaigu web-ouvert-def

Abf clermont-oe
08. 06. 2016
0 views

Abf clermont-oe

Profil ertzscheid - copie
30. 06. 2016
0 views

Profil ertzscheid - copie

appetit-geants-ertzscheid
27. 06. 2017
0 views

appetit-geants-ertzscheid