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Guide to Wireless Communications

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  1. Guide to Wireless Communications

  2. Objectives • Explain how the major wireless technologies are used today - WiFi • Describe the applications used in wireless technology • List and explain the advantages of wireless technology • List and explain the disadvantages of wireless technology

  3. Wireless – the hype? • Wireless communications is the next major event in the history of technology • Wireless communications will revolutionize how we live • Users will be able to access digital resources no matter where they find themselves

  4. How Wireless Technology Is Used • Wireless refers to any device that does not use wires • Wireless communications refers to the transmission of user data without wires

  5. Wireless Applications • Wireless applications are found anywhere employees need mobility, including in the following industries: • Education • Military • Business • Entertainment • Travel • Construction • Warehouse management • Health care

  6. Wireless Communications in Industries • Education—classrooms, presentations, libraries, access anywhere on campus • Military—Universal Handset, a 1.5 lb. device allows full motion video, cellular and satellite communications, and Internet access • Business—office space where traditional infrastructure does not exist, such as conference room or hotel room

  7. Wireless Communications in Industries • Entertainment—barcodes on tickets validated by handheld readers; fans accessing game statistics, watching replays, ordering concessions through notebook computers or PDAs • Travel—global positioning systems (GPS) providing emergency roadside assistance; airline passengers using wireless notebooks or PDAs

  8. Wireless Communications in Industries • Construction—scheduling construction phases and employee travel, completing payroll, diagnosing equipment • Warehouse Management—inventory, shipping, reading bar-coded pallet labels • Health Care—tracking dispensed medicine, verifying patients’ bar-coded armbands, accessing patient records

  9. Current Wireless Systems • Fixed Wireless Access (last mile) • Wide Area Wireless Data Services (WWANs) • Cellular Systems • Satellite Systems & Paging Systems • HomeRF (SWAP) (now dead?) • Bluetooth • Wireless LANs (WiFi) • WiFi5

  10. SWAP • Shared Wireless Access Protocol (SWAP) defines wireless computer networks • Allows wireless data and voice communication from distances up to 150 feet at speeds up to 10 million bits per second (megabits or Mbps) • Established by HomeRF Working Group, comprised of over 50 different companies • Uses wireless home networking adapter that sends data over radio waves throughout the home, as seen in Figure 1-1

  11. Home Wireless Network

  12. HomeRF • Shared Wireless Access Protocol (SWAP), Home RF is an open industry specification that allows wireless devices to share information around home • Operates in license-free 2.4 GHz frequency and uses frequency-hopping spread spectrum (FHSS) • Provides quality-of-service (QoS) that prioritizes time-sensitive transmissions • Version 1.0, introduced in 2000, transmits at 1.6 Mbps, but version 2.0, released in 2001, transmits at 10 Mbps

  13. Bluetooth • Uses devices with small radio transceivers, called radio modules, built onto microprocessor chips • Special software, called a link manager, identifies other Bluetooth devices, creates links with them, and sends and receives data • Transmits at up to 1 Mbps over a distance of 33 feet and is not impeded by physical barriers • Bluetooth products created by over 1500 computer, telephone, and peripheral vendors

  14. Bluetooth Headset • The Bluetooth headset automatically establishes a connection with the telephone

  15. Piconet • Two or more Bluetooth devices that send and receive data make up a personal area network (PAN), also called a piconet • Figure 1-3 shows a Bluetooth network Bluetooth was named after the 10th century Danish King Harold Bluetooth, who was responsible for unifying Scandinavia

  16. Bluetooth Network

  17. Network Topology • Two types of Bluetooth network topologies • Piconet • Scatternet (collection of piconets) • Two Bluetooth devices within range automatically connect • One device is the master, controlling all wireless traffic • The other is the slave, taking commands from the master.

  18. Piconets • A piconet is one master and at least one slave using the same channel • An active slave is sending transmissions • A passive slave is not actually participating

  19. Bluetooth Issues • Many challenges face Bluetooth • Cost • Limited support • Shortcomings in protocol itself • Positioning in marketplace • Conflicts with other devices in radio spectrum

  20. Cost • Chips have decreased in price to about $15 from a high of over $75 • Not advantageous to replace a $7 cable with a $15 chip • Many think cost must come down to about $5 before Bluetooth reaches competitive advantage

  21. Limited Support • Bluetooth is caught in “chicken or egg” scenario • Because of low market penetration, Bluetooth is not fully supported by hardware and software vendors • Users reluctant to purchase technology that is not fully supported • Microsoft is “straddling the fence” • Provides Bluetooth support for Pocket PC 2002 • Does not support Bluetooth in Windows XP

  22. Protocol Limitations • Major limitation is no hand-off between piconets • Unlike cell phone switching, Bluetooth connection is broken and must be restored with new master when device moves from one piconet area to another • Bluetooth provides less than optimal security by authenticating devices instead of users • Devices cannot determine how function of other devices can be used in cooperating setting

  23. Market Position • Current position is between IEEE 802.11x WLANs and cell phones • WLAN is preferred technology for connecting wireless devices to form network • WLAN is mature, robust, flexible, popular technology • Trend today is fewer devices instead of more, and cell phones have integrated capabilities that Bluetooth lacks

  24. Spectrum Conflict • The 2.4 GHz band that Bluetooth uses conflicts with IEEE 802.11b WLANs • WLAN may drop connection when detects another device sharing its frequency • Most obvious fix is moving Bluetooth device away from WLAN • Many vendors offer products that let Bluetooth and 802.11b WLANs share spectrum • New 802.11a WLAN standard uses a different frequency, eliminating the conflict

  25. Wireless Local Area Network (WLAN) • Based on the Institute of Electrical and Electronic Engineers (IEEE) 802.11b networking standard • WLAN computers transmit up to 11 Mbps at distances of 375 feet • IEEE 802.11a standard increases bandwidth to 54 Mbps • Figure 1-8 shows a WLAN warehouse network • 802.11 often called wireless ethernet

  26. WLAN Warehouse Network

  27. WLAN Applications • Almost nonexistent until 2000, WLANs have experienced astonishing growth, with sales expected to top $34 billion by 2004 • WLANs have broad range of uses including colleges and schools, businesses, airports, warehouses, shopping malls, and stadiums • WLANs have taken the world by storm and the list of users grows daily

  28. How WLANs Operate • Although a variety of radio frequency WLANs exist, different products share similarities and operate similarly • Only two components are required for a wireless network • Wireless network interface (NIC) cards • Access points (AP)

  29. Wireless NIC and Access Point (AP) • Each computer on WLAN uses wireless network interface card (NIC) with built-in antenna • Wireless NIC sends signals through radio waves to a fixed access point (AP) • AP point may be attached to a wired LAN • Figure 1-9 shows an AP and wireless NIC • WLANs also used in office environments, as shown in Figure 1-10

  30. Access Point and Wireless NIC

  31. Office WLAN

  32. Wireless Network Interface Card • NIC connects computer to network so it can send and receive data • On wired network, NIC has a port for a cable connector, as seen in Figure 6-1 • On wireless network, the NIC has an antenna to send and receive RF signals • NIC changes internal data from parallel to serial, divides data into packets with sending and receiving addresses, determines when to send packet, and transmits packet

  33. Integrated Wireless NICs • Some vendors plan integrating components of wireless NIC onto single chip on motherboard • Some notebook manufacturers will integrate wireless NIC into top of notebook behind LCD display • This will keep RF waves away from motherboard

  34. Software for Wireless NICs • Software may be part of operating system itself • Windows XP has software integrated while previous versions of Windows do not • Software may be separate program loaded into the computer • All operating systems before Windows XP, including Linux, require loading software • Operating systems for PDAs may soon integrate software to recognize a wireless NIC

  35. Access Point • An access point (AP) has three main parts • An antenna and a radio transmitter/receiver • An RJ-45 wired network interface to connect to a wired network • Special bridging software

  36. Access Point

  37. Functions of an Access Point • Access point has two basic functions • Acts as base station for wireless network • Acts as bridge between wireless and wired network • Bridges are LAN connectors at MAC level • See Figure 6-7

  38. Access Point as a Bridge

  39. Characteristics of an Access Point • Range approximately 375 feet (115 meters) • Generally supports over 100 users • One access point for each 50 users with light email and basic Internet access • One access point per 20 users for heavy network access and large file transfer • APs typically mounted on ceiling, but AC power may be a problem • Power over Ethernet feature delivers DC power through standard unshielded twisted pair (UTP) Ethernet cable

  40. Ad Hoc Mode • Ad Hoc Mode or peer-to-peer mode lets wireless clients communicate among themselves without an access point • Officially called Independent Basic Services Set (IBSS), this mode is easy to set up, but it does not have access to a wired network • See Figure 6-8

  41. Ad Hoc Mode

  42. Infrastructure Mode • Infrastructure Mode, also called Basic Service Set (BSS), has wireless clients and an access point • More access points can be added to create an Extended Service Set (ESS) • See Figure 6-9

  43. Extended Service Set (ESS)

  44. Features of Access Points • Coverage area should overlap when using multiple access points • Wireless clients survey radio frequencies to find an AP that provides better service • A seamless handoff occurs when client associates with new AP

  45. ESS and Subdivided Networks • Drawback of ESS WLANs is that all wireless clients and APs must be part of same network to allow roaming • Network managers like to subdivide networks into subnets, but this prevents clients from roaming freely • Alternative may be software that tricks network into seeing subnets as one network

  46. Wireless Gateway • Devices that follow 802.11 standard are becoming less expensive and more popular • Wireless Gateway has made future of HomeRF very shaky • Wireless gateway has wireless access point, Network Address Translator (NAT) router, firewall, connections for DSL and cable modems, and other features

  47. IEEE 802.11 • Introduced in 1990 • Defines cable-free local area network with either fixed or mobile locations that transmit at either 1 or 2 Mbps • Uses OSI model with functions of PHY and MAC layer performing WLAN features • See Figure 6-10 • Slow bandwidth insufficient for most network applications

  48. WLAN features in PHY and MAC layers

  49. IEEE 802.11b • 1999 amendment to 802.11 standard • Added two higher speeds: 5.5 and 11 Mbps • Called Wi-Fi • Quickly became standard for WLANs