1 / 30

Principle of Communications

Principle of Communications. Prof Yewen Cao School of Information Science and Engineering Shandong University. LECTURE 1 Introduction. What this course is about Brief overview of the Course General Info Chapter 1 ： Introduction to communications. What this course is abou t?.

derora
Download Presentation

Principle of Communications

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. Principle of Communications Prof Yewen Cao School of Information Science and Engineering Shandong University

  2. LECTURE 1 Introduction • What this course is about • Brief overview of the Course • General Info • Chapter 1：Introduction to communications

  3. What this course is about? • Content Text book: J.G. Proakis and M. Salehi, Communication System Engineering (2nd Ed) • General components in communications system • Review of time- and frequency-domain analysis of signals and systems • Review of the characterization of random processes • Introduction to analog signal transmission and reception • Introduction to digital communications

  4. What this course is about? • Prerequisites • Maths • Engineering mathematics Trigonometry, series, integration/ differentiation, etc. • Probability, random variables and statistics Gaussian and uniform distributions, noise, autocorrelation , power spectrum, etc. • Primary courses in Electronics • Linear systems and signals Fourier series/transform, transfer function, sampling, filtering, etc.

  5. Brief overview of the Course • Chapter 1 General introduction to communications system • Historical review • Elements and block diagram of an communication system • Communication channels： • Types and their characteristics • Mathematical models • Chapter 2 and 4 • Review of basic material on signals and systems • Review of probability and random processes • Chapter 3 and 5 • Principle of modulation and demodulation of AM,FM and PM • Performance analysis of AM, FM and PM

  6. Brief overview of the Course • Chapter 6 Characterization of information sources and source encoding • Modeling of information sources, both discrete and continuous • Discrete source coding: Huffman and Lempel-Ziv coding algorithms • Continuous source coding: PCM,DPCM,DM • Practical examples of source coding: CD player and JPEG image-coding standard • Chapter 7 A range of digital modulation and demodulation techniques • Binary and M-ary modulation methods: geometric representation ,performance analysis and comparison • Symbol and carrier synchronization methods

  7. Brief overview of the Course • Chapter 8 Digital transmission over band-limited channels • Channel distortion and ISI • Signal design for a band-limited channel: Nyquist’s rules • Equalizers • Chapter 9 Channel coding and decoding • Channel capacity, Shannon formula • Linear block codes • Convolutional codes • Practical applications of coding

  8. General Info • How to study this course • With patience • Listen carefully • Take notes • With endeavour • e.g., go through the context of the incoming lecture • Review the context and notes over one more times • With interests • Always remind yourself it’s a truly useful course for your career in future • With aids of references • If with much difficulties, refer to a textbook in Chinese, although not to be encouraged • With helps one another –talk to each other in English as much as possible • except for the homework and Exams • Homework, Exams and Assessment • Handing in homework in time • Judgement, all in English but regardless of the accuracy of using English • Lab practices • In parallel, another independent course for experiments is arranged

  9. Introduction to communications • Historical review • Early history of communication • 1799 Alessandro Volta invented electric battery, • 1837 Samuel Morse demonstrated telegraph and 1844 first telegraph line (Washington-Baltimore) became operational • Early history of wireless communication • 1831 Faraday demonstrates electromagnetic induction • J. Maxwell (1831-79): theory of electromagnetic Fields, wave equations (1864) • H. Hertz (1857-94): demonstrateswith an experiment the wave character of electrical transmission through space(1888, in Karlsruhe, Germany, at the location of today’s University of Karlsruhe)

  10. Introduction to communications • Historical review • Early history of wireless communication I • 1895 Guglielmo Marconi • first demonstration of wireless telegraphy (digital!) • long wave transmission, high transmission power necessary (> 200kw) • 1907 Commercial transatlantic connections • huge base stations (30 100m high antennas) • 1915 Wireless voice transmission New York - San Francisco • 1920 Discovery of short waves by Marconi • reflection at the ionosphere • smaller sender and receiver, possible due to the invention of the vacuum tube (1906, Lee DeForest and Robert von Lieben) • 1926 Train-phone on the line Hamburg - Berlin • wires parallel to the railroad track

  11. Introduction to communications • Historical review • Early history of wireless communication II • 1928 many TV broadcast trials (across Atlantic, color TV, TV news) • 1933 Frequency modulation (E. H. Armstrong) • 1958 A-Netz in Germany • analog, 160MHz, connection setup only from the mobile station, no handover, 80% coverage, 1971 11000 customers • 1972 B-Netz in Germany • analog, 160MHz, connection setup from the fixed network too (but location of the mobile station has to be known) • available also in A, NL and LUX, 1979 13000 customer in D • 1979 NMT at 450MHz (Scandinavian countries) • 1982 Start of GSM-specification • goal: pan-European digital mobile phone system with roaming • 1983 Start of the American AMPS (Advanced Mobile Phone System, analog) • 1984 CT-1 standard (Europe) for cordless telephones

  12. Introduction to communications • Historical review • Early history of wireless communication III • 1986 C-Netz in Germany • analog voice transmission, 450MHz, hand-over possible, digital signaling, automatic location of mobile device • Was in use until 2000, services: FAX, modem, X.25, e-mail, 98% coverage • 1991 Specification of DECT • Digital European Cordless Telephone (today: Digital Enhanced Cordless Telecommunications) • 1880-1900MHz, ~100-500m range, 120 duplex channels, 1.2Mbit/s data transmission, voice encryption, authentication, up to several 10000 user/km2, used in more than 50 countries • 1992 Start of GSM • in D as D1 and D2, fully digital, 900MHz, 124 channels • automatic location, hand-over, cellular • roaming in Europe - now worldwide in more than 170 countries • services: data with 9.6kbit/s, FAX, voice, ...

  13. Introduction to communications • Historical review • Early history of wireless communication IV • 1994 E-Netz in Germany • GSM with 1800MHz, smaller cells • As Eplus in D (1997 98% coverage of the population) • 1996 HiperLAN (High Performance Radio Local Area Network) • ETSI, standardization of type 1: 5.15 - 5.30GHz, 23.5Mbit/s • recommendations for type 2 and 3 (both 5GHz) and 4 (17GHz) as wireless ATM-networks (up to 155Mbit/s) • 1997 Wireless LAN - IEEE802.11 • IEEE standard, 2.4 - 2.5GHz and infrared, 2Mbit/s • already many (proprietary) products available in the beginning • 1998 Specification of GSM successors • for UMTS (Universal Mobile Telecommunication System) as European proposals for IMT-2000 Iridium • 66 satellites (+6 spare), 1.6GHz to the mobile phone

  14. Introduction to communications • Historical review • Early history of wireless communication V • 1999 Standardization of additional wireless LANs • IEEE standard 802.11b, 2.4-2.5GHz, 11Mbit/s • Bluetooth for piconets, 2.4Ghz, <1Mbit/s • Decision about IMT-2000 • Several “members” of a “family”: UMTS, cdma2000, DECT, … • Start of WAP (Wireless Application Protocol) and i-mode • First step towards a unified Internet/mobile communication system • Access to many services via the mobile phone • 2000 GSM with higher data rates • HSCSD offers up to 57,6kbit/s • First GPRS trials with up to 50 kbit/s (packet oriented!) • UMTS auctions/beauty contests • Hype followed by disillusionment (approx. 50 B$ payed in Germany for 6 UMTS licenses!) • 2001 Start of 3G systems • Cdma2000 in Korea, UMTS in Europe, Foma (almost UMTS) in Japan

  15. Introduction to communications • Elements of a communication system • Basic concepts • Sources (information inputs) voice (audio), text, image/video and data • Signals Analogue signals, Digital signals • Noises Thermal noise, man-made noise, atmospheric noise, etc • Sinks (information output devices) Computer screens, speakers, TV screens, etc

  16. SignalProcessing CarrierCircuits Transmission Medium Carrier Circuits SignalProcessing m(t) s(t) r(t) TRANSMITTER CHANNEL RECEIVER Introduction to communications • Elements of a communication system (cont) • Basic components • Transmitter • Convert Source (information) to signals • Send converted signals to the channel (by antenna if applicable) • Channel • Wireless: atmosphere (free space) • Wired: coaxial cables, twisted wires, optical fibre • Receiver • Reconvert received signals to original information • Output the original information

  17. twisted pair coax cable optical transmission 1 Mm 300 Hz 10 km 30 kHz 100 m 3 MHz 1 m 300 MHz 10 mm 30 GHz 100 m 3 THz 1 m 300 THz visible light VLF LF MF HF VHF UHF SHF EHF infrared UV Introduction to communications • Elements of a communication system (cont) • Frequencies for communication • VLF = Very Low Frequency UHF = Ultra High Frequency • LF = Low Frequency SHF = Super High Frequency • MF = Medium Frequency EHF = Extra High Frequency • HF = High Frequency UV = Ultraviolet Light • VHF = Very High Frequency • Frequency and wave length:  = c/f wave length , speed of light c  3x108m/s, frequency f

  18. Introduction to communications • Basic digital communications system Signals processing • Source encoding/decoding • Reduction of redundancy • Encryption /decryption • Security and privacy • Channel encoding/decoding • Anti-interferences • Modulation/demodulations • Channel adaptation and sharing Basic digital communications system • Shown in the picture next slide

  19. Modulation Demodulation Regeneration Introduction to communications Baseband Passband audio video (analogue) data (digital) • ASK • FSK • PSK • binary • M’ary A/D Channel Code anti-alias filter •Nyquist sampling • FEC • ARQ • block • convolution • pulse • shaping • filter • ISI channel filter Source Source code • Communications • Channel • loss • interference • noise • distortion Transmit Receive data (digital) audio video (analogue) Source decode Sink Channel Decode D/A low pass filter quantisation noise • matched filter • decision threshold • timing recovery • envelope • coherent • carrier recovery channel filter • FEC • ARQ • Block • Convolution Basic Digital Communications System

  20. Mathematical Models for Communication Channels • Physical channels • Wireless electromagnetic channel: • Atmosphere (free space) • ionospheric channel • Wireline channels • twisted-pair wirelines • coaxial cables • optical fiber cables • Underwater acoustic channels • Storage channels • Common feature for distinct physical channels • Noises, existing always and anywhere • Interferences ,from adjacent channels • Distortion, of channel • Model for communication channels • Reflect the most important characteristics of transmission medium, i.e., physical channels • Be able to conveniently use in design and analysis of communication system

  21. Mathematical Models for Communication Channels • Frequently used channel models • Additive noise channel • Physically, n(t) arising from electronic components and amplifiers, both at transmitter and receiver. • Statistically, n(t) is a random process. • Gaussian noise: n(t) follows Gaussian distribution. • When propagation happened, signal attenuation occurred Channel s(t) r(t)=s(t)+n(t) n(t) Fig.1. The additive noise channel r(t)=as(t)+n(t), Where a represents the attenuation factor • It is a predominant model due to its mathematical tractability

  22. Mathematical Models for Communication Channels • Linear filter channel • Filter, ensuring that transmitted signal do not exceed specified bandwidth limitation • h(t) is the impulse response of the linear filter Linear filter h(t) s(t) r(t)=s(t)*h(t)+n(t) n(t) Channel Fig.2. The linear time-invariant (LTI) filter channel with additive noise channel • It is the most common used model in theory or practical applications

  23. Mathematical Models for Communication Channels • Linear time-variant filter channel • Suitable for the case of physical channels such as under water acoustic channel and ionospheric radio channels. • is the response of the channel at time t, due to an impulse applied at time • represents the “age” (elapsed time) variable Linear time-variant filter s(t) n(t) Channel Fig.2. The linear time-variant (LTV) filter channel with additive noise channel • It is the most common used model in theory or practical applications

  24. Mathematical Models for Communication Channels • Multipath channel • It’s a special case of LTV • Widely used in wireless communications multipath pulses LOS pulses signal at sender signal at receiver Fig.3. Multipath channel model is the number of multipath propagation paths is the possibly time-variant attenuation factors is the possibly delay attenuation factors

  25. Let’s summarize today’s lecture !!!

  26. What we have learnt today !!! • An brief introduction to the course • What we will learn in this course, i.e., the roadmap of the course • General pre-requirements for learning this course • Block diagram of communication systems and its basic components, esp. for digital communication systems • Brief history of communications • Channel models for communication systems

  27. What is the next ? • Frequency domain analysis of signals and systems---Chapter 2 (totally, 2-3 lectures) We will learn and review: • Fourier series (Section 2.1) • Fourier transforms (Section 2.2)

  28. What you need to do after lecture? • Review and self-study Go through the Chapter 1(at least 1 times) • Homework Nil • Preparation pp.24-40, of textbook

  29. Thank you for attention!!! & Questions???

  30. Slides downloading Visit my homepage at: http://202.194.26.100/caoyewen/

More Related