Topic

Determination of the real field distribution of high frequency electromagnetic fields near wireless LAN installations (WLAN) in inner cities

Start

15.11.2004

End

14.05.2006

Project Management

ARC Seibersdorf research GmbH, Austria

Objective

Wireless LAN systems are frequently considered to be an alternative to GSM and UMTS networks for data communication in inner cities. When the project was defined at the beginning of 2004, a number of so-called 'City LANs' were being set up (e.g. in Hamburg). Today, in the first month of 2007, a total of more than 12,000 WLAN hotspots, i.e. public places at which wireless internet access via WLAN is available, are registered all over Germany.

This project was intended to address the distribution of electromagnetic fields near WLAN transmitters used as public 'hotspots'. The real exposure situation of the population at these places was evaluated with the help of computer simulations and measuring campaigns. Research was supposed to cover both the fields emanating from Access Points (which can be compared to mobile phone base stations) and the fields emanating from the end user devices (these will generally be the users' laptops).

Results

Investigations were made in a café, at an airport terminal, at a university campus, on an inner city square, in residential quarters which offer their inhabitants wireless internet access via WLAN and on the CeBit IT trade faire in Hanover. In all scenarios the IEEE 802.11 b or g standard was used. All exposures observed at the different WLAN hotspots were significantly below the reference value of 10 W/m² which is set out in the European Union Council recommendation 1999/519/EC. A difference must be made, however, between peak values measured in time and space and values averaged over time and space. The highest peak values measured were in the range of 100-200 mW/m², while measured values averaged over typical dimensions of the human body and over 6 minutes were by one to two orders of magnitude (factor 10 to 100) Lower than the peak values.

The final report is available as PDF-file in German (3.127 KB MB).

References

• G. Schmid, P. Preiner, D. Lager, R. Überbacher, and R. Georg: Exposure of the general public due to wireless LAN applications in public places, Radiation Protection Dosimetry, Vol. 124, No. 1, 2007, pp. 48-52, doi:10.1093/rpd/ncm320

Conclusions

WLAN transmitters and the transmitters employed by WLAN users at so-called hotspots cause only a very low level of additional exposure to the general public. It would be possible to reduce the exposure even further for reasons of precaution, if the antennae, in particular that of the Access Point, were positioned in such a way that people do not have access to their immediate vicinity.