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Wireless Application Protocol

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Wireless Application Protocol

Today Lecture Introduction to wireless communication Why Wireless communication? Challenges in wireless communication. Human Requirements Wireless vs Mobile Types of Wireless Communication Limitations and Difficulties of Wireless Technologies

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What is wireless communication?

A wireless network enables people to communicate and access applications and information without wires. This provides freedom of movement and the ability to extend applications to different parts of a building, city, or nearly anywhere in the world.

Transfer of voice or data without wires.

Transmitting and receiving voice or data using electromagnetic waves in open space The information from sender to receiver is carrier over a well-

defined frequency band (channel) Each channel has a fixed frequency bandwidth and Capacity

(bit-rate) Different channels can be used to transmit information in

parallel and independently.

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Why Wireless communication?

Freedom from wires– No cost of installing wires or rewiring– No bunches of wires running here and there– communications without physical connection

setup, e.g., Bluetooth,WiFi Global Coverage– Communications can reach where wiring isinfeasible or costly, e.g., rural areas, old buildings,battlefield, vehicles, outer space (throughCommunication Satellites)

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Challenges in wireless communication

Stay Connected– Roaming allows flexibility to stay connected anywhere and any time– Rapidly growing market attests to public need for mobility and uninterrupted access Flexibility– Services reach you wherever you go (Mobility).E.g, you don’t have to go to your lab to check your

mail– Connect to multiple devices simultaneously (no

physical connection required)

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Techanical Challenges in wireless communication

Efficient Hardware– Low power Transmitters, Receivers

– Low Power Signal Processing Tools

Efficient use of finite radio spectrum– Cellular frequency reuse, medium access control

protocols,...

Integrated services– voice, data, multimedia over a single network

– service differentiation, priorities, resource sharing,...

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Challenges (2)

Network support for user mobility (mobile scenarios) – location identification, handover,... Maintaining quality of service over

unreliable links Connectivity and coverage (internetworking) Cost efficiency

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Challenges (3)

Fading Multipath Higher probability of data corruption – Hence, need for stronger channel codes Need for stronger Security mechanisms – privacy, authentication,…

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Human Requirements

Delay Packet Loss BER Data Rate Traffic

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Wireless vs Mobile

NOTE : Wireless does not necessarily mean mobile Wireless Systems may be – Fixed (e.g., Metropolitan Area Network) – Portable (e.g., wireless interaction between TV and

VCR) – Mobile (e.g., mobile phone)

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Wired Vs. Wireless Communication

Wired Wireless

Each cable is a different channel One media (cable) 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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Why Wireless Networks

Cabling is sometimes impossible – Even if possible, cabling is quite expensive

• Modern work conditions require the flexibility of installation No cost for re-installation or rewiring Wireless is convenient and not too expensive

Roaming allows flexibility – Stay connected anywhere and any time

Rapid market growth and application demands – uninterrupted, fast access regardless of the application • Consumers and businesses are willing to pay for it

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Why go wireless ?

Advantages► Sometimes it is impractical to lay cables► User mobility► Cost

Limitations► Bandwidth► Fidelity► Power► (In) security

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Types of Wireless Communication (1)

Radio Transmission – Easily generated, omni-directionally travel long distances, easily penetrate buildings – Problems: • frequency-dependent • relative low bandwidth for data communication • tightly licensed by the governments Microwave Transmission – Widely used for long distance communication – Gives a high S/N ratio, relatively inexpensive – Problems: • don’t pass through buildings well • weather and frequency-dependent

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Types of Wireless Communication (2)

Infrared and Millimeter Waves – Widely used for short-range communication – Unable to pass through solid objects – Used for indoor wireless LANs, not for outdoors Lightwave Transmission – Unguided optical signal, such as laser – Connect two LANs in two buildings via laser mounted on their roof – Unidirectional, easy to install, don’t require license – Problems: • unable to penetrate rain or thick fog • laser beam can be easily diverted by turbulent air

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Limitations and Difficulties of Wireless Technologies

Wireless is convenient and less expensive Limitations and political and technical difficulties

inhibit wireless technologiesLack of an industry-wide standardDevice limitations

►E.g., small LCD on a mobile telephone can only displaying a few lines of text

►E.g., browsers of most mobile wireless devices use wireless markup language (WML) instead of HTML

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Limitations and Difficulties of Wireless Technologies

Technology is still expensive – Newer technologies are much expensive

• Range is reduced as much as the speed is increased

• Problems of security and confidentiality Errors occur much more than in wired networks Interference with other systems • Detection of collision is impossible

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Wireless Systems: Range ComparisonWireless Systems: Range Comparison

SatelliteLinks

SWRadio

MWRadio

FMRadio

MobileTelephony,WLL

WLANsBlueoothIR

1,000 Km100 Km10 Km1 Km100 m10 m1 m

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User Growth

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Traffic Growth

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A Simplified Wireless Communication

System Representation

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Mobile Wireless Networks

What must a mobile network provide ?

– Connectivity with mobility – Cost-effective sharing of bandwidth – Performance

• How are mobile networks designed ?

– Layering – Protocols – Standards

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Role of Standards

Provide (the hope of) interoperability

– Equipment from different vendors – Existing protocols and software

• Volume in the marketplace – Broader support by equipment/software vendors Reduced

prices

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Classification of WirelessNetworks

Mobility: fixed wireless or mobile • Communication: Analog or digital • Topology/Infrastructure: Ad hoc (decentralized) or centralized (base stations) • Services: voice or data

• Ownership: public or private

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Classification of WirelessNetworks

Area: wide (WAN), metropolitan (MAN), local (LAN), or personal (PAN) area

networks • Medium: Switched (circuit- or Packet switched) or broadcast • Data Rate: Low bit-rate (voice grade)

or high bit-rate (video, multimedia) • Placement: satellite

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Current Wireless Systems

Cellular Systems Wireless LANs Satellite Systems Wireless PANs (bluetooth)