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Radio Spectrum

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36 diapositives · 524 Views · Aug 26, 2014

Radio Spectrum. The Achilles’ Heel of Wireless Computing Fred L. Strickland COMP 7970 Persuasive Computing Fall 2002 Directed by Dr Richard Chapman Auburn University, Auburn Alabama. Abstract. Wireless devices are everywhere. Communicate while moving Work outside of the desk

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  1. Radio Spectrum The Achilles’ Heel of Wireless Computing Fred L. Strickland COMP 7970 Persuasive Computing Fall 2002 Directed by Dr Richard Chapman Auburn University, Auburn Alabama

  2. Abstract • Wireless devices are everywhere. • Communicate while moving • Work outside of the desk • Are there any draw backs?

  3. Outline • What radio bands may be used? • What are the behaviors of these bands? • What are in those bands? • What problems exist today? • What problems may happen tomorrow? • Is there an answer?

  4. What radio bands may be used? • Wireless devices are really radios.

  5. 5.650-5.925 GHz (SHF) 24.000-24.250 GHz (SHF) 59.00-64.00 GHz (EHF) 120.02-126.00 GHz (EHF) 241.00-248.00 GHz (EHF) The License Free Radio Bands - Industry Scientific and Medical (ISM) • 6,765-7,000 kHz (HF) • 13,410-13,570 kHz (HF) • 26,950-27,410 kHz (HF) • 40-40.98 MHz (VHF) • 902-928 MHz (UHF) • 2.450-2.500 GHz (UHF)

  6. - Unlicensed National Informational Infrastructure (UNII) • 5.1250-5.2500 GHz (SHF) • 5.2500-5.3500 GHz (SHF) • 5.5250-5.8250 GHz (SHF)

  7. - Unallocated bands • Below 9 kHz • Above 400 GHz (EHF)

  8. So what does this all mean?

  9. What are these bands and their behaviors? • ELF(Extremely Low Frequency): • 30 to 300 Hz • 300 to 3,000 Hz • VLF (Very Low frequency): • 3,000 Hz or 3 kHz to 30 kHz) • LF (Low Frequency): • 30 to 300 kHz

  10. Behavior, continue • MF (Medium Frequency) • 300 to 3,000 kHz • HF (High Frequency) • 3,000 kHz to 30,000 kHz • Or • 3 to 30 MHz

  11. Behavior, continue • VHF (Very High Frequency) • 30 to 300 MHz • FM Broadcast band (88 to 108) FM Broadcast band • Air Traffic Control (108 to 138) • Television (begins here) • UHF (Ultra High Frequency) • 300 to 3,000 MHz • Same as above, plus radar.

  12. Behavior, continue • SHF (Super High Frequency) • 3,000 to 30,000 MHz • OR • 3 to 30 GHz • EHF (Extremely High Frequency) • 30 to 300 GHz

  13. What activities are in those bands?

  14. What problems exist today? • In general • What will the FCC do? • Between a licensed user and a non-licensed user: • The non-licensed user must • Reduce power • Change operations • Shut down • Between two or more non-licensed users • For the most part, the FCC does not oversee the conflict.

  15. Current Problems, continue • Do systems co-exist peacefully?

  16. Current Problems, continue • Radars and the Dedicated Short-Range Communication (DSRC) System • The DSRC could live near a radar with 1 meter separation and the right combination of frequency usage and antennas. • If the DSRC was on the same frequency with a regular antenna, then it would need 7.1 kilometers of separation! • Guess what band these systems operate in? • Guess what is the placement of these systems?

  17. Current Problems, continue • Cordless telephones • Operate in • 900 MHz • 2.4 GHz • 5.8 GHz

  18. Cordless telephones do receive interference from other devices, such as Microwave ovens Wireless computer networks And other devices operating in the 2.4 GHz band Current Problems, continue • Cordless telephones do cause interference to other wireless devices: • To baby monitors • To headphones • To audio products • To video products

  19. Current Problems, continue: • In the context of wireless computer users, how well do these wireless computer devices work? • Bandwidth or data rate • Transmission range • Still need wires to somewhere • Limited support to wireless users • Performance • Security

  20. Current Problems, continue • Bandwidth or data rate • IEEE 802.11a • 6 to 54 Megabits per second in the 5 GHz band • IEEE 802.11b • 2 to 11 Megabits per second in the 2.8 GHz band

  21. Current Problems, continue • Transmission range • IEEE 801.11a • 15 feet for 54 Megabits per second • Lower the rate and the distance increases • IEEE 801.11b • Roughly 300 feet • Thick concrete walls will cut down the range even more or stop it completely.

  22. Current Problems, continue • The cord cannot be completed cut. • Access points are needed. • Wires must run from each access point device to a network hub, bridge, or router. • Running wires has it challenges too.

  23. Roughly, how many access points does Dartmouth College use to cover the campus?

  24. Over 500 access points!

  25. Current Problems, continue • How many users? • IEEE 802.11a can support 8 channels • IEEE 802.11b can support 3 channels • Hard to tell • How many users can a single access point support? • How many access points can you have in a large lecture hall?

  26. Current Problems, continue • Another weakness is the area of performance. • Wireless connections will never approach the reliability and performance of wired networks. • Wireless connections are subject to noise, weak signals, and other communications problems. • The current best data rate is below the best telephone modem rate of 56 kilobits per second.

  27. Current Problems, continue • The point is security. • Not on par with wired security systems. • Some system administrators turn it off. • Dartmouth College did this so that any one on campus could access the network. • Once a signal is in the air, anyone can listen to it.

  28. What problems may happen tomorrow? • The demands for more radio spectrum keeps growing. A 1995 study* determined that 204 MHz of bandwidth (radio spectrum) is needed for new... • Cellular users • Personal communications services • Mobile satellites • Intelligent transportation system sectors • *NTIA Report 98-349: A Technological Rational to Use Higher Wireless Frequencies, February 1998

  29. Future Problems, continued • Some want to increase the 5 GHz band. • Some want 5.470-5.725 GHz. • This band is important to the Department of Defense. • High power radars and low power wireless computer devices cannot live together

  30. Future Problems, continued • As more devices appear in an area, then the overall throughput will decrease. • IEEE 802.11a and IEEE 802.11b are still evolving • Some companies (Intel and Microsoft) are planning to sell products in 2003 with the current evolving standard in wireless products. • Open wireless networks can be hacked. • Any illegal activities could be charged to the network owner.

  31. Is there an answer? • Try doing something else. • Talk face to face instead of using Instant Messenger. • Use wires instead of going wireless.

  32. Answer, continued • Think about your needs • Do you really need a wireless connection from the local cemetery? (Dartmouth College thinks so, but that seems to be a bit extreme.)

  33. Answer, continued • There are things that companies should be doing. • Do not oversell the benefits of being wireless. • Try other ISM radio bands. • Fix the receiver problems.

  34. What now? The end or the beginning. • This presentation was • To touch upon the radio spectrum side of wireless computing. • To make you aware of some of the hidden problems. • To ask you to change your lifestyle a bit. • To join your voice with others to ask for companies to fix their equipment.

  35. Questions? Comments? Feedback? • Your turn.

  36. Added material • Satellite radio is in 2332.5 to 2345 MHz • Global Positioning Satellites are in 1575 MHz • The satellite radio groups want more frequencies around the GPS radio bands.