Wireless

Chapter 1: Introduction to Wireless Networks

Student: Yusuf Farhan

Wireless Applications

• Wireless applications are found anywhere employees need mobility, including in the following industries:– Education– Military– Business – Entertainment– Travel– Construction– Warehouse management– Health care

Advantages of Wireless Networks

• No need to install and maintain wires• Reduces cost –important in offices, hotels, …• Simplifies deployment –important in homes, hotspots, …• Supports mobile users:

– Move around office, campus, city, … -users get hooked– Remote control devices (TV, garage door, ..)– Cordless phones, cell phones, ..– WiFi, GPRS, WiMax, …

Disadvantages of Wireless Networks

• Quality of transmission• Interference and noise• Capacity of the network• Effects of mobility

Electronic Computing Devices & Technology Trends

Advances in Technology more computing power in smaller devices flat, lightweight displays with low power consumption user interfaces suitable for small dimensions higher bandwidths multiple wireless interfaces: wireless LANs, wireless WANs,

home RF, Bluetooth New Electronic Computing Devices

small, cheap, portable, replaceable and most important of all USABLE!

Technology Trends devices are aware of their environment and adapt - “location

awareness” devices recognize the location of the user and react

appropriately (e.g., call forwarding, fax forwarding)

1.6

Wireless and Mobile Communications

Definition of mobility: user mobility: users communicate anytime, anywhere, with anyone device portability: devices can be connected anytime, anywhere to the

network Definition of wireless:

no physical wire attachment Wireless vs. Mobile Examples

stationary computer notebook in a hotel wireless LANs in legacy buildings Personal Digital Assistant (PDA)

The need for mobility creates the need for integration of wireless networks into existing fixed network environments: local area networks: standardization of IEEE 802.11b/g/a Internet: Mobile IP extension of the internet protocol IP wide area networks: e.g., internetworking of 3G and IP

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Applications I

Vehicles transmission of news, road conditions, weather personal communication using cellular position identification via GPS inter vehicle communications for accident prevention vehicle and road inter communications for traffic control,

signaling, data gathering ambulances, police, etc.: early transmission of patient data to

the hospital, situation reporting entertainment: music, video

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Highway Scenario

ad ho

cGSM, 3G, WLAN, Bluetooth, ...

PDA, laptop, cellular phones,GPS, sensors

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Applications II

Mobile workers access to customer files and company documents stored in a

central location collaborative work environments access to email and voice messages

Replacement of fixed networks remote sensors, e.g., weather, environment, road conditions flexible work spaces LANs in legacy buildings

Entertainment, education, ... outdoor Internet access intelligent travel guide with up-to-date

location dependent information ad-hoc networks for

multi user games

Built

150BC

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Mobile Devices

performanceperformance

Pager• receive only• tiny displays• simple text messages

Mobile phones• voice, data• simple text displays

PDA• simple graphical displays• character recognition• simplified WWW

Palmtop• tiny keyboard• simple versions of standard applications

Laptop• fully functional• standard applications

Sensors,embeddedcontrollers

Spring 2003ICS 243E - Ch. 1 Introduction 1.11

Impact of Portability on Device Design/Functionality

Power consumption battery capacity - limited computing power, low quality/smaller

displays, smaller disks, fewer options (I/O, CD/DVD) Device vulnerability

Required design withstand bumps, weather conditions, etc. theft

Limited/Simpler User Interfaces display size compromise between comfort/usability and portability (keyboard size)

Limited memory memory limited by size and power flash- or SD memory as alternatives.

Wireless Networks Compared to Fixed Networks

Higher loss-rates due to interference other EM signals, objects in path (multi-path, scattering)

Limited availability of useful spectrum frequencies have to be coordinated, useful frequencies are

almost all occupied Low transmission rates

local area: 2 – 11 Mbit/s, wide area: 9.6 – 19.2 kbit/s Higher delays, higher jitter

connection setup time for cellular in the second range, several hundred milliseconds for wireless LAN systems

Lower security, simpler active attacking radio interface accessible for everyone base station can be simulated, thus attracting calls from

mobile phones Always shared medium

secure access mechanisms important

Location Dependent Services

Location aware services what services, e.g., printer, fax, phone, server etc. exist in the

local environment that can be used by the user (security and authentication)

Follow-on services automatic call-forwarding, transmission of the actual

workspace to the current location Information services

push: e.g., current special offers in the supermarket pull: e.g., where is the Sarah Lee New York Cheese Cake?

Support services caches, intermediate results, state information, etc., follow the

mobile device through the fixed network Privacy

who should gain knowledge about the location of the user/device

Data Communication Terms Data - entities that convey meaning, or information Signals - electric or electromagnetic representations of data Transmission - communication of data by the propagation

and processing of signals. Modulation is varying the properties of a career signal to

send information. The result of modulation is known as the carrier signal or

the baseband signal which we want to transmit to carry information. The basic parameters used to describe the carrier signal are (amplitude, frequency and phase).

Data Communication Terms

Altering these parameters results in three types of modulation; starting from amplitude modulation popularly known as AM, frequency modulation (FM), QPSK, PCM, GMSK, QAM etc.

Multiplexing is a way of combining multiple signals carrying information over a shared medium.

Analog Signals A continuously varying electromagnetic wave that may be

propagated over a variety of media, depending on frequency Examples of media:

Copper wire media (twisted pair and coaxial cable) Fiber optic cable Atmosphere or space propagation

Analog signals can propagate analog and digital data

Digital Signals A sequence of voltage pulses that may be transmitted over a

copper wire medium Generally cheaper than analog signaling Hardly affected by noise interference Suffer more from attenuation (reduction) Digital signals can propagate analog and digital data

Multiplexing

Multiplexing Techniques

Frequency-division multiplexing (FDM) Takes advantage of the fact that the useful bandwidth of the

medium exceeds the required bandwidth of a given signal Time-division multiplexing (TDM)

Takes advantage of the fact that the achievable bit rate of the medium exceeds the required data rate of a digital signal

Frequency-division Multiplexing

Time-division Multiplexing

Areas of research in mobile communication

Wireless Communication transmission quality (bandwidth, error rate, delay) modulation, coding, interference media access, regulations ...

Mobility location dependent services location transparency quality of service support (delay, jitter, security) ...

Portability power consumption limited computing power, sizes of display, ... usability ...

Spring 2003ICS 243E - Ch. 0 Overview 0.25

Mobile communications and the Reference Model

service location adaptive applications congestion and flow control quality of service addressing, routing,

device location hand-over authentication media access media access control multiplexing encryption modulation interference attenuation frequency

Application layer

Transport layer

Network layer

Data link layer

Physical layer

The wireless space

PAN(Personal Area

Network)

LAN(Local Area Network)

WAN(Wide Area Network)

MAN(Metropolitan Area Network)

PAN LAN MAN WAN

StandardsBluetooth802.15.3

802.11802.11802.16802.20

GSM, CDMA, Satellite

Speed < 1 Mbps 11 to 54 Mbps 10-100+ Mbps 10 Kbps–2 Mbps

Range Short Medium Medium-Long Long

ApplicationsPeer-to-Peer

Device-to-DeviceEnterprise Networks Last Mile Access Mobile Data Devices