Wireless LAN Systems

1
Wireless LAN Systems
LAN (Local Area Network) connects host computers
and information processing terminals in offices,
factories, and etc. It also connects terminals
mutually.
2
CISCO Wireless LAN Safety Precautions ref. 1
Proper operation according to the instructions
will result in user exposure that is
substantially below the FCC recommended
limits OET-65, ANSI C95.1, 1991, ETS 300.328

• Do not touch or move antenna while transmitting
  or receiving.
• Do not hold any component containing a radio
  such that the antenna is very close to or
  touching any exposed parts of the body,
  especially the face or eyes, while transmitting.
• Do not operate a portable transmitter near
  unshielded blasting caps or in an explosive
  environment.
• Do not operate the radio or attempt to transmit
  data unless the antenna is connected otherwise,
  the radio may be damaged.
• Orient antenna so that it is at least 20 cm from
  your body.

3
Wireless LAN Systems

• Peak transmitted power 32 mW, 2.4 GHz
• (20 x less than mobile phone)
  (lt 1mW/cm2 at 3 cm)
• Average power is less
• Isotropic (low gain antenna)
• Mobile phones 600 mW to 2 Watt
• Proximity - usually minimum of 1 m
• Complies with ACA guidelines sidebands 95 dB
  down
• Transmitting intermittently in bursts -
• (100 Mbytes/day is 10 min of transmission time)

4
Reference levels for exposure to instantaneous
RMS electric and magnetic fields (unperturbed
fields) ref. 2
Radiation Protection Standard 2002
Australia Maximum Exposure Levels to
Radiofrequency Fields - 3 kHz to 300 GHz
5
Wireless LAN Standard 802.11 ref. 1
Other wireless LAN standards HiperLan HiperL
an II OpenAir HomeRF SWAP BlueTooth
is cable replacement and not wireless LAN
6
Wireless LAN Systems Questions and Answers 1
ref.3
Can you absolutely assure customers that Wireless
LAN products are safe? Extensive research on the
safety of exposure to radio frequency
electromagnetic energy has been carried out for
more than four decades. This research is
continually reviewed and interpreted by
committees of scientists who develop safe limits
for exposure. Manufacturers of wireless LANs
monitor this research and participate in the
consensus standards process and ensure that WLAN
products operate within the guidelines of these
standards. Consequently, manufacturers of WLAN
products believe their products are safe.
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Wireless LAN Systems Questions and Answers 2
ref.3
What if the network has 100 nodes? Only one
transmitter is active at any point in time, so
the radiated power of a total network even when
it has 100 nodes is actually equivalent to the
radiated power of a single transmitter. WLAN
transmitters operate at a power of 0.035 Watts
(35 mW) in the 2.4 GHz band depending on the
specific product in use and the local
regulations.
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Wireless LAN Systems Questions and Answers 3
ref.3
How does WLAN technology differ from cellular
technology? WLAN products use a "bursty" type of
transmit/receive protocol, while Cellular
transmits and receives constantly (connection
oriented). As an example If a user would
transfer data on an average of 100 MB per day,
the WLAN transmitter would be on the air for
approximately 10 minutes. Moreover, a typical
hand held-cell phone has a RF power output of
0.600 Watts (600 mW) or almost 20X more output
power!
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Wireless LAN Systems Some Web Sites of interest

• http//www.cisco.com
• http//www.arpansa.gov.au/
• 3. http//www.wlana.org/learn/health.htm
• http//noc.net.umd.edu/safety.html
• http//www.uow.edu.au/its/wireless/wiresafe.pdf
• http//www.wi-fiplanet.com/tutorials/article.php/1
  428941
• http//www.it.northropgrumman.com/NGIT/files/CCLIB
  RARYFILES/FileName/complete_mobile.pdf

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Wireless LAN Systems Conclusion ref.3
Safe, Low-Power RadiationWireless LAN (WLAN)
devices emit radio frequency electromagnetic
energy. Because WLANs are designed to operate
within the guidelines found in radio frequency
safety standards and recommendations, WLANs are
safe for use by consumers. These standards and
recommendations reflect the consensus of the
scientific community and result from
deliberations of panels and committees of
scientists who continually review and interpret
the extensive research literature.
Conclusion The interpretation of over four
decades of research in this area has led to a
scientific consensus on the safety of exposure to
radio frequency electromagnetic fields. This
consensus is reflected in the recommendations and
standards developed by expert committees such as
NCRP Scientific Committee 53, IEEE Standards
Coordinating Committee 28, IRPA/INIRC and NRPB.
Manufacturers of Wireless Networking products
design their products to operate within the
guidelines of these standards and recommendations
and, therefore, are considered safe.