radio spectrum

Radio Spectrum

The Achilles’ Heel of Wireless ComputingFred L. Strickland

COMP 7970 Persuasive ComputingFall 2002

Directed by Dr Richard Chapman Auburn University, Auburn Alabama

Abstract

Wireless devices are everywhere. Communicate while

moving Work outside of the desk

Are there any draw backs?

OutlineWhat 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?

What radio bands may be used?

Wireless devices are really radios.

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)

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)

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

- Unallocated bands

Below 9 kHz Above 400 GHz (EHF)

So what does this all mean?

–

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

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

Behavior, continueVHF (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.

Behavior, continue

SHF (Super High Frequency)3,000 to 30,000 MHzOR3 to 30 GHz

EHF (Extremely High Frequency)30 to 300 GHz

What activities are in those bands?

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.

Current Problems, continue

Do systems co-exist peacefully?


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?


Cordless telephones Operate in

900 MHz 2.4 GHz 5.8 GHz


Cordless telephones do cause interference to other wireless devices: To baby monitors To headphones To audio products To video products

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:

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


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

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.


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.

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

Over 500 access points!


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?


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.

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.

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

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

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.

Is there an answer?

Try doing something else. Talk face to face instead of using Instant

Messenger. Use wires instead of going wireless.

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.)

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.

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.

Questions? Comments? Feedback?

Your turn.

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.

radio spectrum

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