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Wireless Networking


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Overview of Wireless Networking

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Wireless Networking

  1. 1. Presented By Mrs. Vasanthi Muniasamy M.Sc., M.Phil
  2. 2. INTRODUCTION  Wireless network is an interconnection of many systems capable of providing service to mobile users within a particular geographic region (country or continent)  In wireless network, data are carried by electrical wave (e.g., radio wave) from one node to another.  There is no physical cable/wire connecting one computer to another  Components  Base station  Mobile Switching Center (MSC)  PSTN (Public Telecommunication Switching Network)
  3. 3. Wired (Cabled) Network versus Wireless Network  Advantages of Wireless Network over Wired (Cabled) Network  Mobility: Users can roam around the network without being disconnected  Installation speed and cost: Building wireless medium to large network is usually faster and cheaper than building wired (cabled) medium to large network because there is no need to pull cable through walls and ceilings  Reach of network: Wireless network can be extended to places where wire/cable cannot reach  Flexibility/scalability: New computers can be added easily without having to pull cable into the computers  Disadvantages of Wireless Network compared to Wired Network  Speed: In general, wireless network technology is slower than wired network technology  Security: In general, wireless network is less secured than wired network
  4. 4. Basic Components of Wireless Network
  5. 5. Wireless Network Hardware  Wireless NIC (e.g., wireless Ethernet NIC or Bluetooth NIC) must be installed in each computer  Major functions of wireless NIC:  Sender NIC:  Take data from Layer 3 (Network Layer)  Encapsulate the data into frame  Load the frame to electrical wave  Transmit the electrical wave  Receiver NIC performs the reverse activities  Wireless NIC comes in various forms (Eg., Expansion board, PCMCIA, USB, built-in)
  6. 6. Wireless Network Hardware  Wireless Access Point (WAP/Access Point/AP/Universal Access Point/UAP)  Central “wiring” device to connect wireless nodes to wireless/wired network  If a network uses WAP, all computers must communicate via the WAP
  7. 7. Wireless Network Mode  Ad-Hoc Mode (Peer-to-Peer Mode)  Each wireless node can communicate directly with each of the other nodes in the network (without Wireless Access Point)  Mesh network topology  IBSS (Independent Basic Service Set): a group of nodes communicating in ad-hoc mode  Infrastructure Mode  All wireless node communicate to one another via Wireless Access Point  Star network topology  BSS (Basic Service Set): a group of nodes communicating in infrastructure mode.  An BSS has one wireless access point  EBSS (Extended Basic Service Set): two or more BSS that can communicate to one another  An EBSS contains two or more wireless access points
  8. 8. Ad-Hoc versus Infrastructure Mode Ad-Hoc Mode (IBSS) Infrastructure Mode (BSS)
  9. 9. Wireless Network Security  Three basic wireless network security methods:  SSID (Service Set Identification)  MAC Address Filtering  Encryption
  10. 10. Wireless network Speed  Wireless network speed depends on:  The wireless network technology standard  The distance between sender and receiver, or between a node and a Wireless Access Point  Interference from other wireless devices or electronic devices (e.g., wireless phone)  The presence of solid object (especially metal object, electronic appliance) between the sender and receiver, or between a node and a Wireless Access Point
  11. 11. Wireless Network Range  Wireless network range depends on:  The wireless network technology standard  Interference from other wireless devices or electronic devices  The presence of solid object (especially metal object, electronic appliance) between the sender and receiver, or between a node and a Wireless Access Point  To increase the wireless network range:  Using “signal booster”  Using Wireless Access Point (i.e., instead of using ad-hoc mode, use infrastructure mode)  Using MULTIPLE Wireless Access Points
  12. 12. Wireless Environment and Wireless LANs 13 Wireless Spectrum (1) 30 MHz 30 GHz3 GHz300 MHz Broadcast TV • VHF: 54 to 88 MHz, 174 to 216 MHz • UHF: 470 to 806 MHz FM Radio • 88 to 108 MHz Digital TV • 54 to 88 MHz, 174 to 216 MHz, 470 to 806 MHz
  13. 13. Wireless Environment and Wireless LANs 14 Wireless Spectrum (2) 30 MHz 30 GHz3 GHz300 MHz 3G Broadband Wireless • 746-794 MHz, 1.7-1.85 GHz, 2.5-2.7 GHz Cellular Phone • 800-900 MHz Personal Communication Service (PCS) • 1.85-1.99 GHz
  14. 14. Wireless Environment and Wireless LANs 15 Wireless Spectrum (3) 30 MHz 30 GHz3 GHz300 MHz Wireless LAN (IEEE 802.11b/g) • 2.4 GHz Local Multipoint Distribution Services (LMDS) • 27.5-31.3 GHz Bluetooth • 2.45 GHz Wireless LAN (IEEE 802.11a) • 5 GHz
  15. 15. Wireless Environment and Wireless LANs 16 Evolution of Mobile Wireless (1) Advance Mobile Phone Service (AMPS) • FDMA • 824-849 MHz (UL), 869-894 MHz (DL) • U.S. (1983), So. America, Australia, China European Total Access Communication System (E-TACS) • FDMA • 872-905 MHz (UL), 917-950 MHz (DL) • Deployed throughout Europe
  16. 16. Wireless Environment and Wireless LANs 17 Evolution of Mobile Wireless (2) Global System for Mobile communications (GSM) • TDMA • Different frequency bands for cellular and PCS • Developed in 1990, expected >1B subscriber by end of 2003 IS-95 • CDMA • 800/1900 MHz – Cellular/PCS • U.S., Europe, Asia
  17. 17. Wireless Environment and Wireless LANs 18 Evolution of Mobile Wireless (3) General Packet Radio Services (GPRS) • Introduces packet switched data services for GSM • Transmission rate up to 170 kbps • Some support for QoS Enhanced Data rates for GSM Evolution (EDGE) • Circuit-switched voice (at up to 43.5 kbps/slot) • Packet-switched data (at up to 59.2 kbps/slot) • Can achieve on the order of 475 kbps on the downlink, by combining multiple slots
  18. 18. Wireless Environment and Wireless LANs 19 Evolution of Mobile Wireless (4) Universal Mobile Telecommunication Systems (UMTS) • Wideband DS-CDMA • Bandwidth-on-demand, up to 2 Mbps • Supports handoff from GSM/GPRS IS2000 • CDMA2000: Multicarrier DS-CDMA • Bandwidth on demand (different flavors, up to a few Mbps) • Supports handoff from/to IS-95
  19. 19. Generations in Mobile Wireless Service  First Generation (1G)  Mobile voice services  Second Generation (2G)  Primarily voice, some low-speed data (circuit switched)  Generation 2½ (2.5G)  Higher data rates than 2G  A bridge (for GSM) to 3G  Third Generation (3G)  Seamless integration of voice and data  High data rates, full support for packet switched data
  20. 20. Block Diagram of Cellular System
  21. 21. Development of Wireless Networks  First Generation Wireless Networks  Second Generation Wireless Networks  Third Generation Wireless Networks  Fixed Network transmission Hierarchy  Traffic Routing in Wireless Networks  Circuit Switching  Packet Switching  X.25 Protocol
  22. 22. First Generation Wireless Networks Mobile User Base Station MSC
  23. 23. Second Generation Wireless Networks  Employs digital modulation and advanced call processing capabilities  Ex: GSM, TDMA ,CDMA, Cordless Phones.  Dedicated control channel for voice, signal data.  Provides paging and other data services.  High data rate (N/W access.)  Uses MAHO (Mobile Assisted Hand Off) where mobile units performs the following functions:  reporting received power.  scanning adjacent base station.  data encoding and encryption.
  24. 24. Third Generation Wireless Networks  Aim: to provide single set of standards that can meet wide range of applications and provide universal access thru out the world.  Distinction between cordless and cellular phones disappear as personal handset provides access to voice, data and video services.  It uses broadband integrated service digital N/W (ISDN) to provide internet for both fixed or mobile users.  Provides reliable transfer of information.
  25. 25. Traffic Routing in Wireless Networks 1. Circuit Switching 2. Packet Switching 3. X.25 Protocol
  26. 26. Circuit Switching  There are three phases in circuit switching:  Establish  Transfer  Disconnect  The telephone message is sent in one go, it is not broken up. The message arrives in the same order that it was originally sent.
  27. 27. Packet Switching  In packet-based networks, the message gets broken into small data packets. These packets are sent out from the computer and they travel around the network seeking out the most efficient route to travel as circuits become available. This does not necessarily mean that they seek out the shortest route.  Each packet may go a different route from the others.