20/4/00 p. 1 Postacademic Course on Telecommunications Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven/ESAT-SISTA Module-3 : Transmission Marc Moonen Dept. E.E./ESAT, K.U.Leuven

Postacademic Course on Telecommunications 20/4/00 p. 2 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Module-3 : Transmission Module 1: Introduction to Telecommunications & Networks Module 2: Telecommunication Networks and Technologies Module 3: Transmission Techniques Module 4: Transmission of Sound, Video & Data

Postacademic Course on Telecommunications 20/4/00 p. 3 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Aims/Scope Basic Digital Communication principles modulation/demodulation, detection (for the regraders/sidegraders) New/Advanced Topics CDMA, multicarrier modulation, smart antennas (for the regraders/upgraders) Mostly `bird’s-eye view’ skip mathematical details (if possible) selection of topics (non-exhaustive)

Postacademic Course on Telecommunications 20/4/00 p. 4 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA New/Advanced Topics? Analog & 1G Digital Communication Systems: communication over fairly `simple’ (e.g. AWGN) channels emphasis on modulation/demodulation/timing/etc... circuitry Present Day/Future Communication Systems = box full of mathematics & signal processing for communication over highly bandwidth constrained channels, fading channels, etc...

Postacademic Course on Telecommunications 20/4/00 p. 5 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA New/Advanced Topics ? Example: Telephone Line Modems voice-band modems : up to 56kbits/sec in 0..4kHz band ADSL modems : up to 8Mbits/sec in 30kHz…1MHz band VDSL modems : up to 52Mbits/sec in …10MHz band xDSL communication impairments: channel attenuation/distortion, echo, cross-talk, RFI,... see Lecture-7/8

Postacademic Course on Telecommunications 20/4/00 p. 6 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA New/Advanced Topics? Example : Wireless Communications Typical spectral efficiency :...1 bits/sec/Hz MIMO-transmission (`smart antennas’ & co): example : V-BLAST (Lucent Techn. 1998) …40bits/sec/Hz exploits a `rich scattering environment’ see Lecture-2, Lecture-10

Postacademic Course on Telecommunications 20/4/00 p. 7 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA New/Advanced Topics? 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...

Postacademic Course on Telecommunications 20/4/00 p. 8 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Overview (I) 20/4/2000 Lecture-1 : General Intro Lecture-2 : Limits of Communication 27/4/2000 Lecture-3 : Transmitter Design/Modulation Lecture-4 : Receiver Design/Detection 4/5/2000 Lecture-5 : Channel Equalization Lecture-6 : Adaptive Equalization

Postacademic Course on Telecommunications 20/4/00 p. 9 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Overview (II) 11/5/2000 Lecture-7 : Multicarrier Modulation (I) Lecture-8 : Multicarrier Modulation (II) 18/5/2000 Lecture-9 : Multiple Access/CDMA Lecture-10: Smart Antennas/MIMO-transmission

Postacademic Course on Telecommunications 20/4/00 p. 10 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Assignments & Exam Assignments Pen & paper exercises Self-study material Exam 25/5/2000 WWW-site : telecom.europace.be

Postacademic Course on Telecommunications 20/4/00 p. 11 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Prerequisites Module-1 - M. Goossens : Yes (?) Module-2 - P. DeMeester : No Digital Communications Background : No (?) Mathematics Background : Yes statistics, linear algebra -> see assignments Signal Processing Background : Yes digital filters, transforms, stochastic processes -> see assignments

Postacademic Course on Telecommunications 20/4/00 p. 12 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Literature E.A. Lee & D.G. Messerschmitt `Digital Communication’ (Kluwer AP 1994) J.G. Proakis `Digital Communications’ (McGraw Hill 1989) B. Sklar `Digital Communications’ (Prentice-Hall 1988) S. Haykin `Communication Systems’ (Wiley 1994) H. Meyr, M. Moeneclaey & S. Fechte `Digital Communication Receivers’ (Wiley 1998) etc...

Postacademic Course on Telecommunications 20/4/00 p. 13 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Acknowledgement Many of the slides/text/figures/graphs are adopted from the handouts of Module T2 `Digital Communication Principles’ M.Engels, M. Moeneclaey, G. Van Der Plas 1998 Postgraduate Course on Telecommunications Special thanks to Prof. Marc Moeneclaey

Postacademic Course on Telecommunications 20/4/00 p. 14 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Lecture-1 : General Introduction Analog vs. Digital Communication Digital Communication Systems Description Transmitter Channel Receiver Preview Lectures 2->10

Postacademic Course on Telecommunications 20/4/00 p. 15 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Analog vs. Digital Communication (I) Analog Communication: Transmission of signals that are inherently analog (speech, video, etc..) Baseband or passband (AM, FM,..) Bandwidth = signal bandwidth Example: speech signal 0..4kHz -> BW=4kHz Received signal subject to channel impairments, transmitter/receiver impairments, etc..

Postacademic Course on Telecommunications 20/4/00 p. 16 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Analog vs. Digital Communication (II) Digital Communication: Transmission of signals that are inherently digital (`data’) or analog (speech, video, etc..) Analog signals are converted into digital signals by sampling & quantization (A-to-D conversion) Example : - speech 0…4kHz - sampled at 8kHz (cfr. Nyquist criterion), - each sample converted into 8 bits number-> 64kbits/sec =PCM (pulse code modulation)

Postacademic Course on Telecommunications 20/4/00 p. 17 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Analog vs. Digital Communication (III) Digital Communication What? A principle feature of a digital communication system is that during a finite interval of time, it sends a waveform from a finite set of possible waveforms. The objective of the receiver is not to reproduce the transmitted waveform, but (only) to determine which of the possible waveforms has been sent.

Postacademic Course on Telecommunications 20/4/00 p. 18 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Analog vs. Digital Communication (IV) Digital Communication Key Features: source coding/compression: Example: speech signal 64kbits/sec-> 11kbits/sec…4kbits/sec (through `signal modeling’) channel coding/error correction see also Module-4 increased spectral efficiency through coding, signal processing, etc. Example: v.34 voice-band modem 33.6 kbits/sec in 4kHz voice-band (=8bits/sec/Hz)

Postacademic Course on Telecommunications 20/4/00 p. 19 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Digital Communication System (I) Block Diagram Digital Information is digital signal (data) or `sampled+quantized’ analog signal (speech,..) digital information s(t)r(t) digital information channel TxRx Transmitter with D-to-A Receiver with A-to-D continuous-time channel

Postacademic Course on Telecommunications 20/4/00 p. 20 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Digital Communication System (II) Transmitter converts bit sequence into waveform s(t) (=`modulation’) bits are grouped into `symbols’ (n bits per symbol, hence M=2^n different symbols) (=`symbol alphabet’, `constellation’) each symbol corresponds to a different waveform segment symbol rate = # transmitted symbols/sec = Rs (`Baud rate’, after Baudot, French telegraph engineer)

Postacademic Course on Telecommunications 20/4/00 p. 21 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Digital Communication System (III) Channel physical medium : twisted pair, coax, optical fiber, radio channel impairments : noise, attenuation/distortion, cross-talk, interference, etc…

Postacademic Course on Telecommunications 20/4/00 p. 22 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Digital Communication System (IV) Receiver Converts received signal r(t) into bit sequence (=`demodulation/detection’) Receiver performance : Bit Error Probability (BEP) or Bit Error Rate (BER) BER = (#bit errors) / (#transmitted bits) example : voice : BER <1E-3 data : BER <1E-10

Postacademic Course on Telecommunications 20/4/00 p. 23 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Transmitter (I) Transmitted bits are grouped into symbols (n bits per symbol, hence M=2^n symbols) Transmitted symbols are Transmitted signal is where p(t) is transmit pulse, and is symbol energy ( and p(t) are energy-normalized), Ts is symbol period

Postacademic Course on Telecommunications 20/4/00 p. 24 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Transmitter (II) Transmitted signal is Linear modulation (e.g. PAM, QAM, PSK) all signal segments are proportional to the same pulse p(t) see Lecture-3 for pulse design Non-linear modulation (e.g. FSK) emphasis on this see assignments

Postacademic Course on Telecommunications 20/4/00 p. 25 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Transmitter (III) Constellations for linear modulation (=`symbol alphabet’) PAM PSK QAM pulse amplitude modulation phase-shift keying quadrature amplitude modulation 4-PAM (2bits) 8-PSK (3bits) 16-QAM (4bits) ps: complex constellations for passband transmission (see Lecture-3) I R I I R R

Postacademic Course on Telecommunications 20/4/00 p. 26 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Channel (I) Channel impairments: attenuation/distortion (linear/non-linear) noise (linear/non-linear) cross-talk (1 or many) echo (e.g. hybrid impedance mismatch) RFI (e.g. amateur radio)

Postacademic Course on Telecommunications 20/4/00 p. 27 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Channel (II) Mostly simple linear channel models Example: AWGN-channel (additive white Gaussian noise channel) n(t) is zero-mean Gaussian process with power spectrum No/2 for |f|<B (B=bandwidth) (example: satellite communication channel) r(t)=Ho.s(t)+n(t) channel s(t) n(t) Ho+

Postacademic Course on Telecommunications 20/4/00 p. 28 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Channel (III) PS: Gaussian noise model justified through central limit theorem (ex: 1 cross-talker is non-Gaussian, 30 cross-talkers approx. Gaussian) PS: `White’ actually means `white within useful bandwidth’ i.o. truly `white’ (->infinite power hence ill-defined) Example: frequency-selective channel frequency-dependent channel attenuation/phase distortion (example: twisted pair, coax) n(t) channel s(t) R(f)=H(f).S(f)+N(f) H(f) +

Postacademic Course on Telecommunications 20/4/00 p. 29 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Receiver (I) Receiver retrieves transmitted symbols from received signal r(t) This leads to an optimization problem Example: minimum distance receiver where p’(t) is transmit pulse p(t), modified by channel

Postacademic Course on Telecommunications 20/4/00 p. 30 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Receiver (II) For AWGN channels ( frequency-selective channels), a receiver may consist of : - (a front-end `(whitened) matched filter’, WMF) - a symbol-rate sampler (i.e. 1 sample/symbol interval) - a (memory-less) decision device that decides on the nearest symbol in the symbol alphabet Timing instant for symbol-rate sampling is crucial, hence synchronization scheme needed ! WMF see lecture 3-4 r(t) 1/Ts

Postacademic Course on Telecommunications 20/4/00 p. 31 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Receiver (III) For frequency-selective channels, the receiver may consist of - WMF + symbol-rate sampling front-end, or - anti-alias filtering + Nyquist-rate sampling front-end followed by more complicated processing: - Maximum-likelihood sequence estimation (e.g. Viterbi algorithms) - Equalization + decision device - … See Lecture 4-5

Postacademic Course on Telecommunications 20/4/00 p. 32 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Preview Lectures 2->10 Lecture-2 : Limits of Communication Given a communication channel, an amount of transmit power and transmit bandwidth, what is the maximum achievable transmission bit- rate (bits/sec), for which the bit-error-rate is sufficiently (infinitely) small ? Shannon theory (1948) Recent topic: MIMO-transmission (e.g. V-BLAST, cfr. supra)

Postacademic Course on Telecommunications 20/4/00 p. 33 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Preview Lectures 2->10 Lecture-3 : Transmitter Design/Modulation Baseband vs passband modulation Constellations for linear modulation Transmit pulse p(t) design: `(root) raised cosine pulses’ Simple receiver structures, eye diagrams, etc.

Postacademic Course on Telecommunications 20/4/00 p. 34 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Preview Lectures 2->10 Lecture-4 : Receiver Design/Detection Inter-symbol interference Receiver front-ends : - (whitened) matched filtering + symbol-rate sampling - anti-alias filtering + Nyquist-rate sampling Optimum detection - MAP/Maximum Likelihood-detection - MLSE/Viterbi algorithm

Postacademic Course on Telecommunications 20/4/00 p. 35 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Preview Lectures 2->10 Lecture-5 : Receiver Design/Equalization Equalization vs. inter-symbol interference Equalizer structures : - Linear equalizers - Decision-feedback equalizers - Fractionally spaced equalizers Design criteria - Zero-forcing equalization - Minimum-mean-squared-error (MMSE) equalization

Postacademic Course on Telecommunications 20/4/00 p. 36 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Preview Lectures 2->10 Lecture-6 : Adaptive Equalization Equalization when channel is unknown and/or time-varying Least-mean squares algorithm (Widrow 1965) - MMSE and stochastic gradient Recursive Least Squares algorithms - Least squares criterion - Introduction to Fast RLS algorithms

Postacademic Course on Telecommunications 20/4/00 p. 37 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Preview Lectures 2->10 Lecture-7/8 : Multicarrier Modulation Applications - ADSL modems (VDSL modems) Combination of frequency-shift keying (FSK) and quadrature amplitude modulation (QAM) Multicarrier modulation/demodulation based on fast Fourier transforms IFFT/FFT Alleviate (?) equalization problem through usage of cyclic prefix - Time vs. frequency domain equalization

Postacademic Course on Telecommunications 20/4/00 p. 38 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Preview Lectures 2->10 Lecture-9 : Multiple Access/CDMA Multiple Access: - TDMA/FDMA (e.g. GSM) - CDMA (e.g. IS-95, 3G mobile comms) CDMA code sequences CDMA receivers - Single-user detection - Multi-user detection

Postacademic Course on Telecommunications 20/4/00 p. 39 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Preview Lectures 2->10 Lecture-10 : Smart Antennas/MIMO transmission Antenna array receivers - Beamforming - Channel modeling SDMA : `spatial dvision multiple access’ allows different users to use the same frequencies/codes at the same time. Signal separation performed based on spatial properties. MIMO-transmission (e.g. V-BLAST)

Postacademic Course on Telecommunications 20/4/00 p. 40 Module-3 Transmission Marc Moonen Lecture-1 Introduction K.U.Leuven-ESAT/SISTA Preview Lectures 2->10 Lecture-10 (reserve) : Echo Cancellation Echo generation in full-duplex modems - Line echo - Acoustic echo Echo cancellation Adaptive echo cancellation