Digital Signal Processing II `Advanced Topics’ Marc Moonen Dept. E.E./ESAT, K.U.Leuven

DSP-II p. 2 Version Chapter-1 Introduction Chapter-1 : Introduction Aims/Scope Why study DSP ? DSP in applications : GSM, ADSL,… Overview Activities Lectures - Course Notes/Literature Homeworks/Exercise sessions Paper Review Assignment Exam

DSP-II p. 3 Version Chapter-1 Introduction Why study DSP ? Analog Systems vs. Digital Systems - can translate (any) analog (e.g. filter) design into digital - going `digital’ allows to expand functionality/flexibility/… (e.g. how would you do analog speech recognition ? analog audio compression ? …? ) IN OUT IN OUT A/DD/A 2 +2 =4

DSP-II p. 4 Version Chapter-1 Introduction Why study DSP ? Will give two `DSP in applications’ examples –DSP in mobile communications (GSM) –DSP in wireline communications (ADSL/VDSL) Main message: Consumer electronics products have become supercomputers (Mops/sec…Gops/sec), packed with DSP functionalities…

DSP-II p. 5 Version Chapter-1 Introduction DSP in applications : GSM Cellular mobile telephony (e.g. GSM) Basic network architecture : -country covered by a grid of cells -each cell has a base station -base station connected to land telephone network and communicates with mobiles via a radio interface -digital communication format

DSP-II p. 6 Version Chapter-1 Introduction DSP in applications : GSM DSP for digital communications (`physical layer’ ) : –a common misunderstanding is that digital communications is `simple’…. –While in practice… Transmitter 1,0,1,1,0,… Channel x+ a noise 1/a x Receiver decision.99,.01,.96,.95,.07,… 1,0,1,1,0,…

DSP-II p. 7 Version Chapter-1 Introduction DSP in applications : GSM DSP for digital communications (`physical layer’ ) : –In practice… –This calls for channel modeling + compensation (equalization) 1,0,1,1,0,… Transmitter 1,0,1,1,0,… + Receiver ?? noise ` Multipath’ Channel.59,.41,.76,.05,.37,… !!

DSP-II p. 8 Version Chapter-1 Introduction DSP in applications : GSM GSM Channel Estimation/Compensation –Multi-path channel is modeled with short (3…5 taps) FIR filter H(z)= a+b.zˉ¹+c.z ˉ²+d.z ˉ³+e.z ˉ (interpretation?) + ` Multipath’ Channel ≈ + Δ Δ Δ ΔΔ Δ ΔΔΔΔ a b c d e 4

DSP-II p. 9 Version Chapter-1 Introduction DSP in applications : GSM GSM Channel Estimation/Compensation (continued) –Multi-path channel is modeled with short (3…5 taps) FIR filter H(z)= a+b.zˉ¹+c.z ˉ²+d.z ˉ³+e.z ˉ + Δ Δ Δ ΔΔ Δ ΔΔΔΔ a b c d e 4 IN[k] OUT[k] =convolution

DSP-II p. 10 Version Chapter-1 Introduction DSP in applications : GSM GSM Channel Estimation/Compensation (continued) –Channel coefficients (cfr. a,b,c,d,e) are identified in receiver based on transmission of pre-defined training sequences (TS), in between data bits. Problem to be solved at receiver is: `given channel input (=TS) and channel output (=observed), compute channel coefficients’. This leads to a least-squares parameter estimation procedure See PART-III on optimal filtering

DSP-II p. 11 Version Chapter-1 Introduction DSP in applications : GSM GSM Channel Estimation/Compensation (continued) –Channel coefficients (cfr. a,b,c,d,e) are identified in receiver based on transmission of pre-defined training sequences (TS), in between data bits. –Channel model is then used to design suitable equalizer (`channel inversion’), or (better) to reconstruct transmitted data bits based on maximum-likelihood sequence estimation (`Viterbi decoding’). –Channel is highly time-varying (e.g. terminal speed 120 km/hr !) => All this is done at `burst-rate’ ( times per sec). = SPECTACULAR !!

DSP-II p. 12 Version Chapter-1 Introduction DSP in applications : GSM GSM Channel Estimation/Compensation GSM Speech Coding –Original `PCM’-signal has 64kbits/sec = 8 ksamples/sec * 8bits/sample. –Aim is to reduce this to <11kbits/sec, while preserving quality ! –Coding based on speech generation model (vocal tract,…), where model coefficient are identified for each new speech segment (e.g. 20 msec). –This leads to a least-squares parameter estimation (again), executed times per second. Fast algorithm is used, e.g. `Levinson-Durbin’ algorithm. See PART-III on optimal filtering. –Then transmit model coefficients instead of signal samples. –Synthesize speech segment at receiver (should `sounds like’ original speech segment). = SPECTACULAR !!

DSP-II p. 13 Version Chapter-1 Introduction DSP in applications : GSM GSM Channel Estimation/Compensation GSM Speech Coding GSM Multiple Access Schemes –Capacity increase by time & frequency `multiplexing’ –FDMA : e.g. 125 frequency channels for GSM/900MHz –TDMA : 8 time slots(=users) per channel, `burst mode’ communication (PS: in practice, capacity per cell << 8*125 ! ) See PART-II on filter banks/transmultiplexers Etc.. = BOX FULL OF DSP/MATHEMATICS !!

DSP-II p. 14 Version Chapter-1 Introduction Telephone Line Modems –voice-band modems : up to 56kbits/sec in 0..4kHz band –ADSL modems : up to 8Mbits/sec in 30kHz…1MHz band (3,5…5km) –VDSL modems : up to 52Mbits/sec in …12MHz band (0.3…1.5km) How has this been made possible? DSP in applications : ADSL X 1000

DSP-II p. 15 Version Chapter-1 Introduction Communication Impairments : Channel attenuation –Received signal may be attenuated by more than 60dB (attenuation increases with line length & larger at high (MHz) frequencies) PS: this is why for a long time, only the voiceband (up to 4kHz) was used –Frequency-dependent attenuation introduces ``inter-symbol interference’’ (ISI). ISI channel can (again) be modeled with an FIR filter. Number of taps will be much larger here (>500!) DSP in applications : ADSL

DSP-II p. 16 Version Chapter-1 Introduction DSP in applications : ADSL Communication Impairments : Coupling between wires in same or adjacent binders introduces `crosstalk’ –Near-end Xtalk (NEXT) (=upstream in downstream, downstream in upstream) –Far-end Xtalk (FEXT) (=upstream in upstream, downstream in downstream) Meaning that a useful signal may be drowned in (much larger) signals from other users.. … leading to signal separation and spectrum management problems Radio frequency interference (AM broadcast, amateur radio) Echo due to impedance mismatch Etc.. Conclusion: Need advanced modulation, DSP,etc. !

DSP-II p. 17 Version Chapter-1 Introduction DSP in applications : ADSL ADSL spectrum : divide available transmission band in 256 narrow bands (`tones’), transmit different sub-streams over different sub-channels (tones) (=DMT, `Discrete Multi-tone Modulation’)

DSP-II p. 18 Version Chapter-1 Introduction DSP in applications : ADSL ADSL-DMT Transmission block scheme : DFT/IDFT (FFT/IFFT) based modulation/demodulation scheme pointer : PS: do not try to understand details here...

DSP-II p. 19 Version Chapter-1 Introduction DSP in applications : ADSL ADSL specs 512-point (I)FFT’s (or `similar’) for DMT-modulation FFT-rate = kHz (i.e. >4000 times 512-point FFTs per second !!!! ) basic sampling rate is 2.21 MHz (=512*4.3215k) 8.84 MHz A/D or D/A (multi-rate structure) fixed HP/LP/BP front-end filtering for frequency duplex See PART-I on filter banks/transmultiplexers adjustable time-domain equalization filter (TEQ) e.g MHz filter initialization via least-squares/eigenvalue procedure adaptive frequency-domain equalization filters (FEQ) See PART-III on adaptive filters = BOX FULL OF DSP/MATHEMATICS !! >20M ops/sec >60M ops/sec

DSP-II p. 20 Version Chapter-1 Introduction DSP in applications : VDSL VDSL specs 4096-point (I)FFT’s (or `similar’) for DMT-modulation FFT-rate = kHz (i.e. >4000 times 4096-point FFTs per second !!!! ) etc.. = BOX FULL OF DSP/MATHEMATICS !! >160M ops/sec

DSP-II p. 21 Version Chapter-1 Introduction DSP in applications : Other… Speech Speech coding (GSM, DECT,..), Speech synthesis (text-to-speech), Speech recognition Audio Signal Processing Audio Coding (MP3, AAC,..), Audio synthesis Editing, Automatic transcription, Dolby/Surround, 3D-audio,. Image/Video Digital Communications Wireline (xDSL,Powerline), Wireless (GSM, 3G, Wi-Fi, WiMax CDMA, MIMO-transmission,..) …

DSP-II p. 22 Version Chapter-1 Introduction DSP in applications Enabling Technology is Signal Processing 1G-SP: analog filters 2G-SP: digital filters, FFT’s, etc. 3G-SP: full of mathematics, linear algebra, statistics, etc... VLSI etc... Signals&Systems course (JVDW) DSP-I (PW) DSP-II

p. 23 Version Chapter-1 Introduction DSP-II Aims/Scope Basic signal processing theory/principles filter design, filter banks, optimal filters & adaptive filters Recent/advanced topics robust filter realization, perfect reconstruction filter banks, fast adaptive algorithms,... Often `bird’s-eye view’ skip many mathematical details (if possible… ) selection of topics (non-exhaustive)

DSP-II p. 24 Version Chapter-1 Introduction Overview (I) INTRO : Chapter-1 Chapter-2 : Signals and Systems Review Part I : Filter Design & Implementation Chapter-3 : IIR & FIR Filter Design Chapter-4 : Filter Realization Chapter-5 : Filter Implementation

DSP-II p. 25 Version Chapter-1 Introduction Overview (II) Part II : Filter Banks & Subband Systems Chapter-6 : Filter Banks Intro/Applications (audio coding/CDMA/…) Chapter-7/8 : Filter Banks Theory Chapter-9/10: Special Topics (Frequency-domain processing, Wavelets,…). 3 subband processing 3 H1(z) G1(z) 3 subband processing 3 H2(z) G2(z) 3 subband processing 3 H3(z) G3(z) 3 subband processing 3 H4(z) G4(z) + IN OUT

DSP-II p. 26 Version Chapter-1 Introduction Overview (III) Part III : Optimal & Adaptive Filtering Chapter-11 : Optimal/Wiener Filters Chapter-12: Adaptive Filters/Recursive Least Squares Chapter-13: Adaptive Filters/LMS Chapter-14: `Fast’ Adaptive Filters Chapter-15: Kalman Filters.

DSP-II p. 27 Version Chapter-1 Introduction Literature / Campus Library Arenberg A. Oppenheim & R. Schafer `Digital Signal Processing’ (Prentice Hall 1977) L. Jackson `Digital Filters and Signal Processing’ (Kluwer 1986) P.P. Vaidyanathan `Multirate Systems and Filter Banks’ (Prentice Hall 1993) Simon Haykin `Adaptive Filter Theory’ (Prentice Hall 1996) M. Bellanger `Digital Processing of Signals’ (Kluwer 1986) etc... Part-III Part-II Part-I

DSP-II p. 28 Version Chapter-1 Introduction Literature / DSP-II Library Collection of books is available to support course material List/info/reservation via DSP-II webpage contact: (E/C)

DSP-II p. 29 Version Chapter-1 Introduction Activities : Lectures Lectures: 18 * 2 hrs Course Material: Part I-II-III : Slides (use version !!)...download from DSP-II webpage Part III : `Introduction to Adaptive Signal Processing’, Marc Moonen & Ian.K. Proudler = support material, not mandatory ! …(if needed) download from DSP-II webpage

DSP-II p. 30 Version Chapter-1 Introduction Activities : Homeworks/Ex. Sessions `Homeworks’ …to support course material 6 Matlab/Simulink Sessions …to support homeworks …come prepared ! contact:

DSP-II p. 31 Version Chapter-1 Introduction Activities : Paper Review Assignment Aim: Learn to read DSP research papers Aim: Discover DSP technology in present-day systems examples: 3D-audio, music synthesis, automatic transcription, speech codec, MP3, GSM, ADSL, … Select paper from list on DSP II webpage & submit 1 st /2 nd choice by Oct.15 to Study paper & context (=www surfing) Presentation: December, 20 mins per group (ppt or similar) –Present application, context & contribution –Make it understandable for your fellow students !!! –Everyone attends all presentations !!! Groups of 2 Time Budget=38h.pp+presentations

DSP-II p. 32 Version Chapter-1 Introduction Activities : Paper Review Assignment Papers List available in DSP-II web page Other topics : subject to approval ! ( to before Oct. 15) Tutoring Research assistants/postdocs (p28) All PPT presentations will be made available, for ref.

DSP-II p. 33 Version Chapter-1 Introduction Activities : Exam Oral exam, with preparation time Open book Grading : 5 pts for question-1 5 pts for question-2 5 pts for question-3 5 pts for assignment (presentation) ___ = 20 pts

DSP-II p. 34 Version Chapter-1 Introduction homes.esat.kuleuven.be/~pepe/dspII/ Contact: Slides Homeworks Projects info/schedule Exams DSP-II Library FAQs (send questions to or