Brain Frying Wi-Fi?
Yesterday I saw a BBC Panorama program on the risks of WiFi radiation. According to the BBC journalist, the measured WiFi radiation in a UK city center is about three times higher than the radiation produced by a GSM cell station about 100 meters away. The journalist was trying to make the case that if cellular GSM masts are required to be located away from schools, then, why encourage kids to use WiFi-enabled laptops or why deploy city-wide WiFi networks, including at schools and homes.
I have always been very skeptical about the risks of such low power radiation devices. After all, a WiFi router radiates about 100,000 times less than a domestic microwave. Nevertheless, the program showed people that claim to get sick with WiFi radiation. If this picks up with the public opinion, it could be a serious problem for WiFi systems, regardless of whether the problem exists or not.
The methods used in the program were far from being “scientific”, and there is a lot to debate about the results presented. Still, the reason I am concerned about this is because I had hoped that the WiFi revolution (both when being used as base stations and to create mesh networks) would not only provide wireless networks with greater capacity (in the information theory way), but would also be perceived as a “greener” wireless technology, since less powerful base stations have to be deployed. However, this seems to be under debate now. Not a good start…
sbm:
Recording my first time visit! I’ll have to turn off my always-on wireless router at home from now on!
19 July 2007, 10:09 amSue B. Moon's Blog:
AP (Access Point) Diet…
This fall I am on my first sabbatical leave from KAIST and am living in San Diego. I had many plans for my precious sabbatical. To read books and papers I had no time for, to cook and eat more at home, to get back into shape, etc. I sigend up for the g…
15 November 2007, 7:57 pmAnthony Dyer:
Hopefully this will qualm any fears and will correct any misunderstandings of the WiFi technology we use and the risks associated. Informations taken from http://www.fcc.gov/oet/rfsafety/#sec5
HOW SAFE ARE MICROWAVE AND SATELLITE ANTENNAS?
“Point-to-point microwave antennas transmit and receive microwave signals across relatively short distances (from a few tenths of a mile to 30 miles or more). These antennas are usually rectangular or circular in shape and are normally found mounted on a supporting tower, on rooftops, sides of buildings or on similar structures that provide clear and unobstructed line-of- sight paths between both ends of a transmission path or link. These antennas have a variety of uses such as transmitting voice and data messages and serving as links between broadcast or cable-TV studios and transmitting antennas.
The RF signals from these antennas travel in a directed beam from a transmitting antenna to a receiving antenna, and dispersion of microwave energy outside of the relatively narrow beam is minimal or insignificant. In addition, these antennas transmit using very low power levels, usually on the order of a few watts or less. Measurements have shown that ground-level power densities due to microwave directional antennas are normally a thousand times or more below recommended safety limits. Moreover, as an added margin of safety, microwave tower sites are normally inaccessible to the general public. Significant exposures from these antennas could only occur in the unlikely event that an individual were to stand directly in front of and very close to an antenna for a period of time.
Ground-based antennas used for satellite-earth communications typically are parabolic “dish” antennas, some as large as 10 to 30 meters in diameter, that are used to transmit (”uplinks”) or receive (”downlinks”) microwave signals to or from satellites in orbit around the earth. The satellites receive the signals beamed up to them and, in turn, retransmit the signals back down to an earthbound receiving station. These signals allow delivery of a variety of communications services, including long distance telephone service. Some satellite-earth station antennas are used only to receive RF signals (i.e., just like a rooftop television antenna used at a residence), and, since they do not transmit, RF exposure is not an issue.
Since satellite-earth station antennas are directed toward satellites above the earth, transmitted beams point skyward at various angles of inclination, depending on the particular satellite being used. Because of the longer distances involved, power levels used to transmit these signals are relatively large when compared, for example, to those used by the microwave point-to-point antennas discussed above. However, as with microwave antennas, the beams used for transmitting earth-to-satellite signals are concentrated and highly directional, similar to the beam from a flashlight. In addition, public access would normally be restricted at station sites where exposure levels could approach or exceed safe limits.
Although many satellite-earth stations are “fixed” sites, portable uplink antennas are also used, e.g., for electronic news gathering. These antennas can be deployed in various locations. Therefore, precautions may be necessary, such as temporarily restricting access in the vicinity of the antenna, to avoid exposure to the main transmitted beam. In general, however, it is unlikely that a transmitting earth station antenna would routinely expose members of the public to potentially harmful levels of microwaves.”
9 November 2008, 11:29 pm