Wireless Communication &

Embedded Systems

CSC 726 1
Course Outline
 Introduction to wireless communication systems.
 Modern wireless communication systems.
 Introduction to cellular mobile systems
 Cellular system design fundamentals
 Multiple access techniques for wireless
communication.
 Wireless networking.
 Intelligent cell concept and application.
 Embedded systems?
 Introduction to microcontrollers.

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Outline for today

 Introduction
 What is wireless and mobile networking
 History of Wireless
 Challenges of Mobile and Wireless
 What is Personal Communications Systems
 Overview of Wireless Technologies and Systems

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What is Wireless
Communication?

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Block diagram of a Communication Systems

Carrier
Transmitted Received
signal signal
Transmitter Channel Receiver

Information to
be transmitted Recovery of
information
(Baseband signal)

Channel can be:

• Copper
• Optical fibre
• Open space
• Wireless

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Wireless Communication?
 Definition of wireless:
 Un-tethered, no physical wire attachment

 Transmitting voice and data using

electromagnetic waves in open space
 Electromagnetic waves
 Travel at speed of light (c = 3x108 m/s)
 Has a frequency (f) and wavelength (λ)
 c=fxλ
 Higher frequency means higher energy photons.
 The higher the energy photon the more penetrating is
the radiation.
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Types of wireless communication

celullar wireless computer network radio service

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Wireless Systems: Range Comparison
1 m 10 m 100 m 1 Km 10 Km 100 Km 1,000 Km

Mobile FM MW SW Satellite
WLANs Telephony Radio Radio Radio Links
Blueooth

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What are the driving factors for wireless?

 An explosive increase in demand of tether-less

connectivity.
 Need for mobility
 Definition of mobility:
 user mobility: users communicate anytime, anywhere, with
anyone.
 device portability: devices can be connected anytime, anywhere
to the network.

 Dramatic progress in VLSI technology

 Implementation of efficient signal processing algorithms.
 New Coding techniques.
 Success of 2G wireless standards (GSM)
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What are the driving factors for wireless? ctd

 Demand for Ubiquitous Computing

 Anywhere, anytime computing and
communication
 You don’t have to go to the lab to check your email
 Pushing the computers more into background
 Focus on the task and life, not on the computer
 Use computers seamlessly to help you and to make
your life more easier.
 Computers should be location aware
 Adapt to the current location, discover services

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Applications of Wireless communication

 Radio and TV broadcasting.

 Cellular Phones.
 Transmission of news, road conditions, weather.
 Position Identification via GPS
 Vehicle and road inter-communications for traffic control,
signaling, data gathering, accident prevention.
 ambulances, police, etc.: early transmission of patient
data to the hospital, etc.
 Computer Networking
 Etc.

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 Mobile devices

Pager PDA Laptop

• receive only • simple graphical displays • fully functional
• tiny displays • character recognition • standard applications
• simple text • simplified WWW
messages

Sensors,
embedded
controllers

Mobile phones Palmtop

• voice, data • tiny keyboard
• simple text displays • simple versions
of standard applications

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Vehicle and road inter-communications example

GSM, 3G, WLAN,

Bluetooth, ...

PDA, laptop, cellular phones,

GPS, sensors
Electromagnetic Spectrum wavelength

104 102 100 10-2 10-4 10-6 10-8 10-10 10-12 10-14 10-16

Radio Micro Cosmic

IR UV X-Rays
Spectrum wave Rays

104 106 108 1010 1012 1014 1016 1018 1020 1022 1024
frequency

Visible light

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 Electromagnetic Spectrum Application Areas
ISM band
902 – 928 Mhz
2.4 – 2.4835 Ghz
5.725 – 5.785 Ghz

LF MF HF VHF UHF SHF EHF

ν
30kHz 300kHz 3MHz 30MHz 300MHz 3GHz 30GHz 300GHz

10km 1km 100m 10m 1m 10cm 1cm 100mm λ

X rays
Gamma rays
ν infrared visible UV
1 kHz 1 MHz 1 GHz 1 THz 1 PHz 1 EHz

Propagation characteristics are different in each frequency band

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Electromagnetic Spectrum Application Areas
• 20 Hz to ~14 kHz, acoustic — normal range of adult human hearing (most
children and some animals perceive sounds outside this range, most teens
and children can hear frequencies from 14 kHz up to ~16 kHz where most
adults can't) .
• 530 kHz to 1.710 MHz, — AM radio broadcasts
• 42 MHz to 260 MHz, — VHF terrestrial TV broadcast channels
• 88 MHz to 108 MHz, — FM radio broadcasts
• 902 MHz to 928 MHz, common cordless telephone frequency in the US
• 0.8 to 2.3 GHz - mobile phone conversation channels.
• 2.4 GHz - microwave ovens, Wireless LANs and cordless phones
• 5.8 GHz, cordless phone frequency introduced in 2003
• 428 THz to 750 THz, — visible light, from red to violet
• 30 Petahertz (PHz)— x-rays
• 300 Exahertz (EHz) and above - gamma rays

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EM application areas ctd

 when the distance between the sender and receiver is

short (e.g. TV and a remote control) infrared waves are
used.
 for long range distances between sender and receiver
(e.g. TV broadcasting and cellular service) both
microwaves and radio waves are used.
 radio waves are ideal when large areas need to be covered and
obstacles exist in the transmission path.
 microwaves are good when large areas need to be covered and
no obstacles exist in the transmission path ( line of sight).

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Wired Vs. Wireless Communication

Wired Wireless
Each cable is a different channel One media shared by all

Signal attenuation is low High signal attenuation

No interference High interference

Noise: co-channel interference,
adjacent channel interference

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Wireless pros and cons
 Advantages  Disadvantages:
 a wireless communication  Higher loss-rates due to interference
 other EM signals & devices, objects in
network is a solution in path (multi-path, scattering), , climatic
areas where cables are conditions,
impossible to install (e.g.  Limited availability of useful spectrum
 frequencies have to be coordinated,
hazardous areas, long useful frequencies are almost all
distances etc.) occupied.
 Security Vulnerabilities - Lower
 User mobility security, simpler active attacking
 Cheaper to install, less time  radio interface accessible for everyone
too  base station can be simulated, thus
attracting calls from mobile phones .

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Electromagnetic Signal

 Function of time
 Can also be expressed as a function of
frequency
 Signal consists of components of different
frequencies

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Time-Domain Concepts
 Analog signal - signal intensity varies in a smooth
fashion over time
 No breaks or discontinuities in the signal
 Digital signal - signal intensity maintains a constant
level for some period of time and then changes to
another constant level
 Periodic signal - analog or digital signal pattern that
repeats over time
 s(t +T ) = s(t ) - ∞< t < + ∞
 where T is the period of the signal
 Aperiodic signal - analog or digital signal pattern that
doesn't repeat over time

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Time-Domain Concepts
 Peak amplitude (A) - maximum value or
strength of the signal over time; typically
measured in volts
 Frequency (f )
 Rate, in cycles per second, or Hertz (Hz) at which the
signal repeats
 Period (T ) - amount of time it takes for one
repetition of the signal
 T = 1/f
 Phase (φ) - measure of the relative position in
time within a single period of a signal
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Time-Domain Concepts
 Wavelength (λ) - distance occupied by a single cycle of the signal
 Or, the distance between two points of corresponding phase of two
consecutive cycles
λ = vT

Sine wave Square wave

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Frequency-Domain Concepts
 Fundamental frequency - when all frequency
components of a signal are integer multiples of one
frequency, it’s referred to as the fundamental frequency
 Spectrum - range of frequencies that a signal contains
 Absolute bandwidth - width of the spectrum of a signal
 Effective bandwidth (or just bandwidth) - narrow band
of frequencies that most of the signal’s energy is
contained in.
 Any electromagnetic signal can be shown to consist of a
collection of periodic analog signals (sine waves) at
different amplitudes, frequencies, and phases.
 The period of the total signal is equal to the period of the
fundamental frequency.

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Frequency Channels/bands

 The information from sender to receiver is carried

over a well defined frequency band.
 This is called a channel
 Each channel has a fixed frequency bandwidth (in
KHz) and Capacity (bit-rate)
 Different frequency bands (channels) can be used
to transmit information in parallel and
independently.

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Frequency channels ctd
 Assume a spectrum of 90KHz is allocated over a base frequency b for
communication between stations A and B
 Assume each channel occupies 30KHz.
 There are 3 channels
 Each channel is simplex (Transmission occurs in one way)
 For full duplex communication:
 Use two different channels (front and reverse channels)
 Use time division in a channel
Channel 1 (b - b+30)

Station A Channel 2 (b+30 - b+60) Station B

Channel 3 (b+60 - b+90)

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Basics of Radio Communication
 Radio waves generation:
 When a high-frequency alternating current (AC)
passes through a copper conductor it generates
radio waves which are propagated into the air
using an antenna.

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Radio propagation

• radio waves are generated by an antenna and they propagate in

all directions as a straight line.
• radio waves travel at a velocity of 186.000 miles per second
(speed of light).
• radio waves become weaker as they travel a long distance
(attenuation).

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there are 3 modes of propagation:

 surface mode – for low frequency waves

 direct mode – for high frequency waves

 ionospheric mode – long distance high frequency waves

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Modulation
 modulation = adding information (e.g. voice) to a carrier
electromagnetic (radio) signal.

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Types of Modulation

 Frequency Modulation (FM).

 Amplitude Modulation (AM)

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Simplex Communication

 Normally, on a channel, a station can

transmit only in one way.
 This is called simplex transmision
 To enable two-way communication (called
full-duplex communication)
 We can use Frequency Division Multiplexing
 We can use Time Division Multiplexing

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Duplex Communication - FDD

 FDD: Frequency Division Duplex

Mobile Forward Channel Base Station

Terminal B
Reverse Channel
M

Forward Channel and Reverse Channel use different frequency

bands

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Duplex Communication - TDD

 TDD: Time Division Duplex

Mobile Base Station

Terminal M B M B M B
B
M

A singe frequency channel is used. The channel is divided into time

slots. Mobile station and base station transmits on the time slots
alternately.

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What is PCS
 Personal Communication Services
 A wide variety of network services that includes wireless access
and personal mobility services.
 Enables communication at any time, at any place, and in any
form.
 The market for such services is tremendously big.
 cell-phone market is an example.
 Residential, business and public cordless access applications
and systems
 Paging Systems
 Mobile Satellite Systems
 LEO, MEO, HEO satellites for data/voice
 ISM band systems: Bluetooth, 802.11, 802.16, etc.

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Very Basic Cellular/PCS Architecture

Mobility
Public Switched Database
Base Station
Telephone Network Controller

Mobile
Switching
Center
(MSC)

Radio Network

Base Station
(BS) Mobile Station

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Wireless System Definitions

 Mobile Station
 A station in the cellular radio service intended for use while
in motion at unspecified locations. They can be either hand-
held personal units (portables) or installed on vehicles
(mobiles)
 Base station
 A fixed station in a mobile radio system used for radio
communication with the mobile stations. Base stations are
located at the center or edge of a coverage region. They
consists of radio channels and transmitter and receiver
antennas mounted on top of a tower.

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Wireless System Definitions

 Mobile Switching Center

 Switching center which coordinates the routing of calls in a
large service area. In a cellular radio system, the MSC
connections the cellular base stations and the mobiles to
the PSTN (telephone network). It is also called Mobile
Telephone Switching Office (MTSO)
 Subscriber
 A user who pays subscription charges for using a mobile
communication system
 Transceiver
 A device capable of simultaneously transmitting and
receiving radio signals

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Wireless System Definitions

 Control Channel
 Radio channel used for transmission of call setup, call
request, call initiation and other beacon and control
purposes.
 Forward Channel
 Radio channel used for transmission of information from
the base station to the mobile
 Reverse Channel
 Radio channel used for transmission of information from
mobile to base station

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Wireless System Definitions

 Simplex Systems
 Communication systems which provide only one-way
communication
 Half Duplex Systems
 Communication Systems which allow two-way
communication by using the same radio channel for both
transmission and reception. At any given time, the user can
either transmit or receive information.
 Full Duplex Systems
 Communication systems which allow simultaneous two-way
communication. Transmission and reception is typically on
two different channels (FDD).

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Wireless System Definitions

 Handoff
 The process of transferring a mobile station from one
channel or base station to an other.
 Roamer
 A mobile station which operates in a service area (market)
other than that from which service has been subscribed.
 Page
 A brief message which is broadcast over the entire service
area, usually in simulcast fashion by many base stations at
the same time.

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PCS Systems Classification

 Cordless Telephones
 Cellular Telephony (High-tier)
 Wide Area Wireless Data Systems (High-tier)
 High Speed Local and Personal Area
Networks
 Paging Messaging Systems
 Satellite Based Mobile Systems
 3G Systems

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 Major Mobile Radio Standards- USA

Standard Type Year Multiple Frequency Modulation Channel

Intro Access Band BW
(MHz) (KHz)
AMPS Cellular 1983 FDMA 824-894 FM 30

USDC Cellular 1991 TDMA 824-894 DQPSK 30

CDPD Cellular 1993 FH/Packet 824-894 GMSK 30

IS-95 Cellular/PCS 1993 CDMA 824-894 QPSK/BPSK 1250

1800-2000
FLEX Paging 1993 Simplex Several 4-FSK 15

DCS-1900 PCS 1994 TDMA 1850-1990 GMSK 200

(GSM)
PACS Cordless/PCS 1994 TDMA/FDMA 1850-1990 DQPSK 300

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 Major Mobile Radio Standards -
Europe
Standard Type Year Multiple Frequency Modulation Channel
Intro Access Band BW
(MHz) (KHz)
ETACS Cellular 1985 FDMA 900 FM 25

NMT-900 Cellular 1986 FDMA 890-960 FM 12.5

GSM Cellular/PCS 1990 TDMA 890-960 GMSK 200KHz

C-450 Cellular 1985 FDMA 450-465 FM 20-10

ERMES Paging 1993 FDMA4 Several 4-FSK 25

CT2 Cordless 1989 FDMA 864-868 GFSK 100

DECT Cordless 1993 TDMA 1880-1900 GFSK 1728

DCS-1800 Cordless/PCS 1993 TDMA 1710-1880 GMSK 200

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Cordless Telephones

PSTN
Telephone
Network
Cordless Base unit
Phone

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Cordless Telephones

 Characterized by
 Low mobility (in terms of range and speed)
 Low power consumption
 Two-way tetherless (wireless) voice communication
 High circuit quality
 Low cost equipment, small form factor and long talk-time
 No handoffs between base units
 Appeared as analog devices
 Digital devices appeared later with CT2, DECT
standards in Europe and ISM band technologies in
USA

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Cordless Telephones

 Usage
 At homes
 At public places where cordless phone base units
are available
 Design Choices
 Few users per MHz
 Few users per base unit
 Many base units are connected to only one handset
 Large number of base units per usage area
 Short transmission range

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Cellular Telephony

 Characterized by
 High mobility provision
 Wide-range
 Two-way tetherless voice communication
 Handoff and roaming support
 Integrated with sophisticated public switched
telephone network (PSTN)
 High transmit power requires at the handsets
(~2W)

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Cellular Telephony - Architecture

Radio tower

PSTN
Telephone
Network
Mobile Switching
Center

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Cellular Telephony Systems

 Mobile users and handsets

 Very complex circuitry and design
 Base stations
 Provides gateway functionality between wireless
and wireline links
 Mobile switching centers
 Connect cellular system to the terrestrial
telephone network.

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Mobile Systems Market

 Base station equipment

 Ericsson sells half of the mobile base stations
 1 base station ~ 100 thousand - 1 million dollar
 Huwei
 Alcatel
 Cell phones
 Nokia has the biggest market in cell-phones
 1 cell-phone ~ 100 dollar
 Samsung
 Tecno

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Cellular Networks
 First Generation
 Analog Systems
 Analog Modulation, mostly FM
 AMPS
 Voice Traffic
 FDMA/FDD multiple access
 Second Generation (2G)
 Digital Systems
 Digital Modulation
 Voice Traffic
 TDMA/FDD and CDMA/FDD multiple access
 2.5G
 Digital Systems
 Voice + Low-datarate Data
 Third Generation
 Digital
 Voice + High-datarate Data
 Multimedia Transmission also
 Fourth Generation?
 Five Generation?

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 2G Technologies
cdmaOne (IS-95) GSM, DCS-1900 IS-54/IS-136
PDC
Uplink Frequencies (MHz) 824-849 (Cellular) 890-915 MHz (Eurpe) 800 MHz, 1500 Mhz
1850-1910 (US PCS) 1850-1910 (US PCS) (Japan)
1850-1910 (US PCS)
Downlink Frequencies 869-894 MHz (US Cellular) 935-960 (Europa) 869-894 MHz (Cellular)
1930-1990 MHz (US PCS) 1930-1990 (US PCS) 1930-1990 (US PCS)
800 MHz, 1500 MHz
(Japan)
Deplexing FDD FDD FDD
Multiple Access CDMA TDMA TDMA
Modulation BPSK with Quadrature GMSK with BT=0.3 π/4 DQPSK
Spreading
Carrier Seperation 1.25 MHz 200 KHz 30 KHz (IS-136)
(25 KHz PDC)
Channel Data Rate 1.2288 Mchips/sec 270.833 Kbps 48.6 Kbps (IS-136)
42 Kbps (PDC)
Voice Channels per 64 8 3
carrier
Speech Coding CELP at 13Kbps RPE-LTP at 13 Kbps VSELP at 7.95 Kbps
EVRC at 8Kbps

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2G and Data

 2G is developed for voice communications

 You can send data over 2G channels by
using modem
 Provides data rates in the order of ~9.6 Kbps
 Increased data rates are requires for internet
application
 This requires evolution towards new systems:
2.5 G and more.

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2.5 Technologies

 Evolution of TDMA Systems

 HSCSD for 2.5G GSM
 Up to 57.6 Kbps data-rate
 GPRS for GSM and IS-136
 Up to 171.2 Kbps data-rate
 EDGE for 2.5G GSM and IS-136
 Up to 384 Kbps data-rate

 Evolution of CDMA Systems

 IS-95B
 Up to 64 Kbps

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3G Systems

 Goals
 Voice and Data Transmission
 Simultanous voice and data access
 Multi-megabit Internet access
 Interactive web sessions
 Voice-activated calls
 Multimedia Content
 Live music

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