1 Wireless Application Protocol
Week#1
2 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
3 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.
4 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 is infeasible or costly, e.g., rural areas, old buildings, battlefield, vehicles, outer space (through Communication Satellites)
5 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)
6 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.
7 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
8 Challenges (3) Fading Multipath Higher probability of data corruption
– Hence, need for stronger channel codes Need for stronger Security mechanisms – privacy, authentication,…
9 Human Requirements Delay Packet Loss BER Data Rate Traffic
10 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)
11 Wired Vs. Wireless Communication
Each cable is a different channel One media (cable) shared by all Signal attenuation is low High signal attenuation High interference noise; co-channel interference; adjacent channel interference No interference
12 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
13 Why go wireless ? Advantages Limitations
Sometimes it is impractical to lay cables User mobility Cost Limitations Bandwidth Fidelity Power (In) security
14 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 • don’t pass through buildings well • weather and frequency-dependent
15 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
16 Limitations and Difficulties of Wireless Technologies
Wireless is convenient and less expensive Limitations and political and technical difficulties inhibit wireless technologies Lack of an industry-wide standard Device 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
17 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
18 Wireless Systems: Range Comparison
CS 698T Wireless Systems: Range Comparison 1 m 10 m 100 m 1 Km 10 Km 100 Km 1,000 Km Satellite Links SW Radio MW Radio FM Radio Mobile Telephony, WLL WLANs Blueooth IR Q1. Can you think of a system whose range of communication is more than satellite links? Q2. Give an example of a system whose range of communication is shorter than IR links. Point to ponder: Why does range of communication increase on logarithm scale? P. Bhagwat 18
21 A Simplified Wireless Communication System Representation
22 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
23 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
24 Classification of Wireless Networks
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
25 Classification of Wireless Networks
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
26 Current Wireless Systems
Cellular Systems Wireless LANs Satellite Systems Wireless PANs (bluetooth)