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Wireless Networks. Instructor: Fatima Naseem Computer Engineering Department, University of Engineering and Technology, Taxila. Lecture # 09. Introduction To Wireless Networks And Its Types. Current Wireless Systems. Cellular system Wireless LANs Satellite Systems Paging Systems

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wireless networks

Wireless Networks

Instructor: Fatima Naseem

Computer Engineering Department, University of Engineering and Technology, Taxila

lecture 09

Lecture # 09

Introduction To Wireless Networks And Its Types

current wireless systems
Current Wireless Systems
  • Cellular system
  • Wireless LANs
  • Satellite Systems
  • Paging Systems
  • PANs (Bluetooth)
1 cellular systems
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
2 wireless local area network wlans
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
3 satellite systems
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)
3 satellite systems1
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
4 paging systems
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
5 personal area networks pans
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
emerging wireless system
Emerging Wireless System
  • Ad hoc wireless networks
  • Sensor networks
  • Distributed control networks
  • Ultra Wideband (UWB) Systems
1 ad hoc networks
1. Ad-Hoc Networks
  • Peer-to-peer communications
  • No backbone infrastructure
  • Routing can be multihop
  • Topology is dynamic
  • Fully connected with different link SINRs
1 ad hoc networks1
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
2 sensor networks
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.
3 distributed control over wireless links
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.
4 ultra wide band system
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)
4 ultra wide band system1
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
spectrum regulation
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
standard bodies
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
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