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Wireless Networks

Wireless Networks

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Wireless Networks

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  1. Wireless Networks Instructor: Fatima Naseem Computer Engineering Department, University of Engineering and Technology, Taxila

  2. Lecture # 09 Introduction To Wireless Networks And Its Types

  3. Current Wireless Systems • Cellular system • Wireless LANs • Satellite Systems • Paging Systems • PANs (Bluetooth)

  4. 1. Cellular Systems • Reuse Channels to maximize capacity • Geographic region divide into cells • Frequencies/timeslots/codes reused at spatially separated locations. • Base stations/Mobile telephone Switching Offices (MTSOs) coordinate handoff and control functions

  5. 2. Wireless Local Area Network (WLANs) • WLANs connect “local” computers(100m range=> confined regions) • Break data into packets • Channel access is shared (random access) • Backbone Internet provides best-effort service • Poor erformance in some applications e.g. video • Low mobility

  6. Wireless LAN Standard

  7. 3. Satellite Systems • Cover very large areas (global coverage) • Very useful in sparsely populated areas: e.g. rural, sea, mountains, etc. • Different orbit heights • GEOs (39000 Km) LEOs (2000 Km) • Optimized for one way transmission • Radio, TV broadcasting • Expensive base stations (satellites)

  8. 3. Satellite Systems • Limited-Quality voice/data transmission • Traditional applications • Weather satellite • Radio/TV broadcasting • Military satellites • Telecommunication Applications • Global telephone connections • Backbone for global network • GPS • Iridium Globalstar, Teledesic, Inmarsat are some examples systems

  9. 4. Paging Systems • Broad coverge for short messaging • Message broadcasting from all base stations • Simple terminals • Low complexity, very low-power pager (receiver) devices • Optimized for 1-way transmission • Answer-back hard • Overtaken by cellular

  10. 5. Personal Area Networks (PANs) • Bluetooth • Cable replacement RF technology (low cost) • Short range (10m, extendable to 100m) • 2.4 GHz band (crowded) • 1 data (700 Kpbs) and 3 voice channels • 1 Mbps data rate shared between 7 devices • TDD duplex scheme • Polling based multiple access • Widely supported by telecommunications, PC, and consumer electronics companies

  11. Emerging Wireless System • Ad hoc wireless networks • Sensor networks • Distributed control networks • Ultra Wideband (UWB) Systems

  12. 1. Ad-Hoc Networks • Peer-to-peer communications • No backbone infrastructure • Routing can be multihop • Topology is dynamic • Fully connected with different link SINRs

  13. 1. Ad-Hoc Networks • Ad-hoc networks provide a flexible network infrastructure for many emerging applications. • The capacity of such networks generally unknown. • Transmission, access, and routing strategies for these networks are generally ad-hoc. • Crosslayer design critical and very challenging. • Energy constraints impose interesting design tradeoffs for communication and networking

  14. 2. Sensor Networks • Energy is the driving constraint • Nodes powered by non-rechargeable batteries • Data flows to centralized location • Low per-node rates but upto 100,000 nodes. • Data highly correlated in time and space. • Nodes can cooperate in transmission, reception, compression and signal processing.

  15. 3. Distributed Control over Wireless Links • Packet loss and/or delays impacts controller performance. • Controller design should be robust to network faults. • Joint application and communication network design.

  16. 4. Ultra Wide Band System • Ultra Wide Band (UWB) is an emerging wireless communications technology that can transmit data at around 100 Mbps (upto 1000 Mbps). • UWB transmits ultra-low power radio signals with very narrow pulses (nanosecond) • Because of its low power requirements, UWB is very difficult to detect (hence secure)

  17. 4. Ultra Wide Band System • Why UWB? • Exceptional multi-path immunity • Low power consumption • Large bandwidth • Secure communications • Low interference • No need for a license to opreate • Next generation communication system

  18. Spectrum Regulation • Worldwide spectrum controlled by ITU-R • ITU auctions spectral blocks for set applications. • Some spectrum set aside for universal use. • Spectral allocation/regulation heavily impacts the evolution of wireless technology

  19. Standard Bodies • CCIR (Consultative Committee on International Radio) • Study groups for radio spectrum usage and interworking of wireless systems • Radio Communications Sector ITU-R (formerly CCIR and IFRB) • World conferences, radio regulations • Telecommunication Standardization Sector ITU T (formerly CCIT) • All worldwide wireline and wireless standards • IEEE standards often accepted