1. Principle of Communications
4/21/2017
Principle of Communications
Prof Yewen Cao
School of Information Science and Engineering
Shandong University 1

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. Prerequisites What this course is about? Maths
4/21/2017
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. 1

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
4/21/2017
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 1

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 Lab practices 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 ( ): theory of electromagnetic Fields, wave equations (1864)
H. Hertz ( ): demonstrates with 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, 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, 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, , 98% coverage
1991 Specification of DECT
Digital European Cordless Telephone (today: Digital Enhanced Cordless Telecommunications)
MHz, ~ m range, 120 duplex channels, 1.2Mbit/s data transmission, voice encryption, authentication, up to several 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 ( % coverage of the population)
1996 HiperLAN (High Performance Radio Local Area Network)
ETSI, standardization of type 1: GHz, 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, GHz 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 b, GHz, 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. 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
m(t)
Signal Processing
Carrier Circuits
Transmission Medium
TRANSMITTER
RECEIVER
s(t)
r(t)
CHANNEL

17. Introduction to communications
Elements of a communication system (cont)
Frequencies for communication
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
optical transmission
coax cable
twisted pair
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
Shown in the picture next slide

19. Introduction to communications
Baseband
Passband
audio
video
(analogue)
data
(digital)
A/D
Channel
Code
Modulation
ASK
FSK
PSK
binary
M’ary
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
D/A
Channel
Decode
Regeneration
Demodulation
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
Channel
s(t)
r(t)=s(t)+n(t)
n(t)
Fig.1. The 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
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
s(t)
Linear filter
h(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
Filter, ensuring that transmitted signal do not exceed specified bandwidth limitation
h(t) is the impulse response of the linear filter
It is the most common used model in theory or practical applications

23. Mathematical Models for Communication Channels
Linear time-variant filter channel
Linear time-variant filter
s(t)
n(t)
Channel
Fig.2. The linear time-variant (LTV) filter channel with additive noise 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
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. Visit my homepage at: http://202.194.26.100/caoyewen/
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