1. Wireless Technologies Chapter 9

2. Learning Objectives Explain current wireless networking technologies Discuss history of wireless networks and their advantages Describe radio wave technologies Explain 802.11 radio wave networking continued…

3. Learning Objectives Describe alternative radio wave technologies: Bluetooth, HiperLAN, and HomeRF Shared Wireless Access Protocol Discuss infrared wireless technologies Describe microwave technologies Explain low Earth orbiting (LEO) satellite wireless networking

4. Current Wireless Networking Technologies Radio wave technologies 802.11 wireless standard Alternative approaches Infrared technologies Microwave technologies Low Earth orbiting (LEO) satellite wireless networking

5. Short History of Wireless Networks Informal beginning in early experimentation with packet radio performed by amateur radio operators

6. Advantages of Wireless Networks Enable communications in areas where wired networks are difficult to install Reduce network installation costs Provide access anywhere (mobile computing) Simplify networks for novices; enable easier small and home office networking Enhance data access

7. Wireless Network Support Organizations Wireless LAN Association (WLANA) WINLAB

8. Radio Wave Technologies Transmit signal in one or multiple directions, depending on type of antenna Use line-of-sight and spread spectrum communications Used for short distance communications Main types IEEE 802.11 standard Alternative technologies

9. Radio Wave Technologies

10. Radio Wave Technologies: Advantages Inexpensive alternative where communications cabling cannot be installed easily Option for portable communications Usually no licensing requirements

11. Radio Wave Technologies: Disadvantages May not be feasible for high-speed networking requirements Subject to interference from the military, radio, cell phones, and other sources Subject to interference from natural obstacles

12. IEEE 802.11 Radio Wave Networking Not reliant on proprietary communications Also called IEEE Standard for Wireless LAN Medium Access (MAC) and Physical Layer (PHY) Specifications Encompasses either fixed or mobile wireless data communications Involves two kinds of communications Asynchronous communications Those governed by time restrictions continued…

13. IEEE 802.11 Radio Wave Networking Includes support for network management services (eg, SNMP protocol) and network authentication Focuses on use of OSI Data Link and Physical layers Recognizes indoor and outdoor wireless communications

14. How IEEE 802.11 Wireless Networks Function Components Access methods Handling data errors Transmission speeds Security techniques Using authentication to disconnect 802.11-based topologies Using multiple-cell wireless LANs

15. Wireless Components Wireless NIC (WNIC) Access points Antennas Directional antenna Omnidirectional antenna

16. Directional Antenna

17. Omnidirectional Antenna

18. Wireless Networking Access Methods Priority-based access Carrier-sense multiple access with collision avoidance (CSMA/CA)

19. Handling Data Errors Automatic repeat-request (ARQ) 802.11 error handling technique Helps reduce communication errors created by sources of interference, such as adverse weather

20. Transmission Speed Standards 802.11a Uses orthogonal frequency-division multiplexing (OFDM) 802.11b Uses direct sequence spread spectrum modulation (DSSS) 802.11g Emerging as extension of 802.11b standard

21. Characteristics of 802.11a and 802.11b

22. Security Techniques Open system authentication Shared key authentication Employs Wired Equivalent Privacy (WEP)

23. Using Authentication to Disconnect Prevents two communicating stations from being inadvertently disconnected by another non-authenticated station

24. 802.11 Network Topologies Independent basic service set (IBSS) topology Two or more wireless stations that can be in communication Does not use an access point Ad hoc peer-to-peer communication between WNICs on individual computers Extended service set (ESS) topology One or more access points provide a larger service area

25. IBBS Wireless Topology

27. Multiple-Cell Wireless LANs ESS wireless topology that employs two or more access points Cell Broadcast area around a single access point Inter-Access Point Protocol (IAPP) Roaming protocol that enables a mobile station to move from one cell to another without losing connection

28. Alternative Radio Wave Technologies Bluetooth HiperLAN HomeRF Shared Wireless Access Protocol (SWAP)

29. Bluetooth Uses the 2.4 GHz band that is defined through Bluetooth Special Interest Group Uses time division duplexing (TDD)

30. HiperLAN Uses the 5 GHz band Compatible with Ethernet and ATM communications Popular in Europe Supports Data Encryption Standard (DES) and QoS Operates in direct or centralized mode

31. HomeRF SWAP Uses the 2.4 GHz band Targeted for home use

32. Infrared Technologies Used for short distance communications Diffused infrared Transmits by reflecting infrared light from the ceiling Used by 802.11R standard Uses pulse position modulation (PPM)

33. Diffused Infrared Wireless Communications

34. Infrared Technologies: Advantages Signal is difficult to secretly interpret

35. Infrared Technologies: Disadvantages May not be feasible when high-speed communications are needed Subject to interference from other light sources Does not go through walls Does not offer as many device choices as other forms of wireless networking

36. Microwave Technologies Used for longer distance communications Two forms Terrestrial microwave Satellite microwave

37. Terrestrial Microwave

38. Satellite Microwave

39. Microwave Technologies: Advantages Inexpensive alternative where communications cabling cannot be installed easily, particularly over long distances Terrestrial microwave may be less expensive in the long run than leasing telecommunications lines

40. Microwave Technologies: Disadvantages May not be feasible when high-speed communications are needed Expensive to install and maintain Subject to interference from rain, snow, fog, EMI, and atmospheric conditions

41. LEO Satellite Wireless Networking Network of communications satellites that orbit above Earth between 435 and 1000 miles

42. Global LEO Network

43. LEO Satellite: Advantages and Disadvantages Advantages Will be positioned around Earth for a global area network Does not have same transmission delays as geosynchronous satellites Disadvantages Not available until 2005

44. Summary of Advantages of Wireless Communications Radio WaveInfraredMicrowaveLEO Satellite  Inexpensive alternative where cabling is not easy to install  Option for portable communications  Usually no licensing requirements  Signal is difficult to interpret secretly  Inexpensive alternative where cabling is not easy to install  Terrestrial microwave costs less than leasing telecommunica- tions lines  Will be positioned around Earth for a global area network  Does not have same transmission delays as geosynchronous satellites

45. Summary of Disadvantages of Wireless Communications Radio WaveInfraredMicrowaveLEO Satellite  May not be feasible for high- speed networks  Subject to interference from military, radio, and cell phones  Subject to interference from natural obstacles  May not be feasible for high- speed networks  Subject to interference from other light sources  Does not go through walls  Not as many device choices  May not be feasible for high- speed networks  Expensive to install and maintain  Subject to interference from rain, snow, fog, EMI, atmospheric conditions  Not available until 2005

46. Chapter Summary Brief history and advantages of wireless networking Currently used forms of wireless networking Radio wave technologies IEEE 802.11 wireless networking standard Alternative radio wave technologies Diffused infrared technologies for relatively secure wireless communications Land-based and satellite microwave technologies for networking, including LEO satellites