Wireless Communication Fundamentals

Wireless

• The Way of accessing a network or other communication waves through ‘Air’

Characteristics of Communication Device: 1.Fixed and Wired: eg: Desktop computers in Office

• Mobile and Wired: Eg: Laptop

• Fixed and Wireless: In historical buildings to avoid

damage by installing wires or at trade show to ensure fast network.

• Mobile and Wireless:GSM(Global System for Mobile Communications) ie.No Cable restricts the user, user can roam

between different wireless network

GSM (Global System for Mobile communications) is an open, digital cellular technology used for transmitting mobile voice and data services.

• GSM supports voice calls and data transfer speeds of up to 9.6 kbps, together with the transmission of SMS (Short Message Service).

Kinds of Mobility

• User Mobility: where user moves to access to the same or similar telecommunication services at different places.

eg: Call forwarding solutions• Device Portability: where communication

device moves.Eg: Mobile Phone System

• Mobile and wireless systems really accomplish two very different things. While a wireless system provides a fixed or portable endpoint with access to a distributed network, a mobile system offers all of the resources of that distributed network to something that can go anywhere, barring any issues with local reception or technical area coverage.

Applications I• Vehicles

– transmission of news, road condition, weather, music via DAB– personal communication using GSM– position via GPS– local ad-hoc network with vehicles close-by to prevent accidents,

guidance system, redundancy – vehicle data (e.g., from busses, high-speed trains) can be transmitted

in advance for maintenance

• Emergencies– early transmission of patient data to the hospital, current status, first

diagnosis– replacement of a fixed infrastructure in case of earthquakes,

hurricanes, fire etc.– crisis, war, ...

Applications• Vehicles:

mobility aware application play a role in car’sAllows to receive music, news weather reports via

(DAB) Digital Audio Broadcasting .UMTS(Universal Mobile Telecommunications

System) phone might be available to offer voice and data connectivity.

GPS(Global Positioning System) for receving position of car.

Typical application: road traffic

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UMTS, WLAN,DAB, DVB, GSM, cdma2000, TETRA, ...

Personal Travel Assistant,PDA, Laptop, GSM, UMTS, WLAN, Bluetooth, ...

Mobile and wireless services – Always Best Connected

UMTS2 Mbit/s

UMTS, GSM384 kbit/s

LAN100 Mbit/s,WLAN54 Mbit/s

UMTS, GSM115 kbit/s

GSM 115 kbit/s,WLAN 11 Mbit/s

GSM/GPRS 53 kbit/sBluetooth 500 kbit/s

GSM/EDGE 384 kbit/s,DSL/WLAN 3 Mbit/s

DSL/ WLAN3 Mbit/s

Applications II• Travelling salesmen

– direct access to customer files stored in a central location– consistent databases for all agents– mobile office

• Replacement of fixed networks– remote sensors, e.g., weather, earth activities– flexibility for trade shows– LANs in historic buildings

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

location dependent information– ad-hoc networks for

multi user games

HistoryInfo

Location dependent services• Location aware services

– what services, e.g., printer, fax, phone, server etc. exist in the local environment

• 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 Black Forrest Cherry 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

Mobile devices

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Pager• receive only• tiny displays• simple text messages

Mobile phones• voice, data• simple graphical displays

PDA• graphical displays• character recognition• simplified WWW

Palmtop• tiny keyboard• simple versions of standard applications

Laptop/Notebook• fully functional• standard applications

Sensors,embeddedcontrollers

www.scatterweb.net

Simple reference model used here

Application

Transport

Network

Data Link

Physical

Medium

Data Link

Physical

Application

Transport

Network

Data Link

Physical

Data Link

Physical

Network Network

Radio

Reference model comprises of

• End systems:»PDA or computer needs a full

protocol stack comprising the Application layer,t ransport ,datalink and physical layer.

»Applications on end systems communicate with each other using layer services.

Intermediate system

• Need only network, data link and physical layer

Influence of mobile communication to the layer model

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

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

Application layer

Transport layer

Network layer

Data link layer

Physical layer

Wireless Transmission

• Wireless transmission means “Transmitting Signals between two devices without incorporating any wire between them”

Spring 2003 ICS 243E - Ch.2 Wireless Transmission 2.20

Spectrum Allocation

VLF = Very Low Frequency UHF = Ultra High FrequencyLF = Low Frequency SHF = Super High FrequencyMF = Medium Frequency EHF = Extra High FrequencyHF = High Frequency UV = Ultraviolet LightVHF = Very High Frequency

Relationship between frequency ‘f’ and wave length ‘’ :

= c/f

where c is the speed of light 3x108m/s

1 Mm300 Hz

10 km30 kHz

100 m3 MHz

1 m300 MHz

10 mm30 GHz

100 m3 THz

1 m300 THz

visible lightVLF LF MF HF VHF UHF SHF EHF infrared UV

optical transmissioncoax cabletwisted pair