# Principle of Communications

Mobile - Wireless

Nov 21, 2013 (4 years and 7 months ago)

85 views

Principle of Communications

Prof Yewen Cao

School of Information Science and Engineering

Shandong University

Shandong University

Prof Cao Yewen

1.
2

LECTURE 1

Introduction

Brief overview of
the Course

General Info

Chapter 1

䥮瑲o摵捴co渠no 捯浭c湩捡c楯湳

Shandong University

Prof Cao Yewen

1.
3

What this course is abou
t?

Content

Text book: J.G. Proakis and M. Salehi,

Communication System Engineering (2
nd

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

Shandong University

Prof Cao Yewen

1.
4

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.

What this course is abou
t?

Shandong University

Prof Cao Yewen

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

Shandong University

Prof Cao Yewen

1.
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

Shandong University

Prof Cao Yewen

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

Shandong University

Prof Cao Yewen

1.
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

Shandong University

Prof Cao Yewen

1.
9

Introduction to communications

Historical review

Early history of
c
ommunication

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

demonstrates electromagnetic induction

J.
Maxwell

(1831
-
79): theory of electromagnetic Fields, wave
equations (1864)

H.
Hertz

(1857
-
94): 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)

Shandong University

Prof Cao Yewen

1.
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

Shandong University

Prof Cao Yewen

1.
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

Shandong University

Prof Cao Yewen

1.
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/km
2
, 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, ...

Shandong University

Prof Cao Yewen

1.
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

Shandong University

Prof Cao Yewen

1.
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

-
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

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

2001 Start of 3G systems

Cdma2000 in Korea, UMTS in Europe, Foma (almost UMTS) in Japan

Shandong University

Prof Cao Yewen

1.
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
-

Sinks (information
output devices)

Computer screens, speakers, TV screens, etc

Shandong University

Prof Cao Yewen

1.
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

Reconvert received signals to original information

Output the original information

m
(
t
)

Signal

Processing

Carrier

Circuits

Transmission Medium

Carrier Circuits

Signal

Processing

TRANSMITTER

s
(
t
)

r
(
t
)

)
(
ˆ
t
m
CHANNEL

Shandong University

Prof Cao Yewen

1.
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

3x10
8
m/s, frequency f

Shandong University

Prof Cao Yewen

1.
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

Basic digital communications system

Shown in the picture next slide

Shandong University

Prof Cao Yewen

1.
19

Introduction to communications

audio

video

(analogue)

data

(digital)

Source

anti
-
alias

filter

A/D

•Nyquist

sampling

Channel

Code

FEC

ARQ

block

convolution

pulse

shaping

filter

ISI

FSK

PSK

binary

M’ar
y

Modulation

channel

filter

Communications

Channel

loss

interference

noise

distortion

channel

filter

Baseband

Passband

Transmit

Demodulation

envelope

coherent

carrier recovery

Regeneration

matched filter

decision threshold

timing recovery

low pass

filter

D/A

quantisation

noise

Channel

Decode

FEC

ARQ

Block

Convolution

data

(digital)

audio

video

(analogue)

Sink

Source

code

Source

decode

Basic Digital Communications System

Shandong University

Prof Cao Yewen

1.
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

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

Shandong University

Prof Cao Yewen

1.
21

Mathematical Models for Communication Channels

Physically, n
(
t
) arising from electronic components and amplifiers, both at transmitter and

Statistically, n
(
t
) is a random process.

Gaussian noise:
n
(
t
) follows Gaussian distribution.

When propagation happened, signal attenuation occurred

Channel

n
(
t
)

s
(
t
)

r
(
t
)
=s
(
t
)
+n
(
t
)

Frequently used channel models

r
(
t
)
=as
(
t
)
+n
(
t
),

Where a represents the attenuation factor

It is a predominant model due to its mathematical tractability

Shandong University

Prof Cao Yewen

1.
22

Mathematical Models for Communication Channels

Filter, ensuring that transmitted signal do not exceed specified
bandwidth limitation

h(t) is the impulse response of the linear filter

Channel

n
(
t
)

s
(
t
)

r
(
t
)
=s
(
t
)*
h
(t)
+n
(
t
)

Fig.2. The linear time
-
invariant (LTI)
filter channel with additive noise channel

Linear filter channel

Linear
filter

h
(
t
)

It is the most common used model in theory or practical applications

)
(
)
(
)
(
)
(
)
(
)
(
)
(
t
n
d
t
s
h
t
n
t
h
t
s
t
r

Shandong University

Prof Cao Yewen

1.
23

Mathematical Models for Communication Channels

Suitable for the case of physical channels such as under water acoustic

is the response of the channel at time t, due to an impulse applied at
time

represents the “age” (elapsed time) variable

)
;
(
t
h

Channel

n
(
t
)

s
(
t
)

Fig.2. The linear time
-
variant (LTV) filter

Linear time
-
variant filter channel

Linear
time
-
variant
filter

It is the most common used model in theory or practical applications

)
(
)
;
(
)
(
)
(
t
n
t
h
t
s
t
r

)
(
)
(
)
;
(
t
n
d
t
s
t
h

)
;
(
t
h

t

Shandong University

Prof Cao Yewen

1.
24

Mathematical Models for Communication Channels

)
(
)
(
)
(
)
(
1
t
n
s
t
a
t
r
L
k
k
k

Fig.3. Multipath channel model

Multipath channel

It’s a special case of LTV

Widely used in wireless communications

L
k
k
k
t
a
t
h
1
)
(
)
(
)
;
(

signal at sender

LOS pulses

multipath

pulses

)
(
t
a
k

is the possibly time
-
variant attenuation factors

L

is the number of multipath propagation paths

k

is the possibly delay attenuation factors

Shandong University

Prof Cao Yewen

1.
25

Let’s summarize today’s lecture !!!

Shandong University

Prof Cao Yewen

1.
26

What we have learnt today !!!

An brief introduction to the course

What we will learn in this course, i.e., the

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

Shandong University

Prof Cao Yewen

1.
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)

Shandong University

Prof Cao Yewen

1.
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

Shandong University

Prof Cao Yewen

1.
29

Thank you for attention!!!

&

Questions???

Shandong University

Prof Cao Yewen

1.
30