| Determination of human exposure caused by indoor wireless communication technologies applied in homes and offices |
|
|
Please note: In the meantime this project was completed and there are new informations in the German version of this document. Topic Determination of human exposure caused by indoor wireless communication technologies applied in homes and offices Start 11.11.2003 End 30.11.2004 Project Management ARC Seibersdorf Research GmbH, Austria Objective The objective of this research project was to obtain a detailed overview of wireless communication devices for home and office currently being used or available on the market in the near future, from the standpoint of radiation protection. In addition to describing and comparing different technologies with regard to technical parameters (emitted frequencies, power, type of signal in the time-domain, etc.) relevant for radiation protection, associated technical measurement requirements for an adequate and reliable exposure determination will be developed and documented. Appropriate measurement and calculation methods developed during the course of the research project will be used to record exposures resulting from the different technologies (DECT, Bluetooth, WLAN, etc) in selected typical exposure scenarios. Results The researcher has presented the technical specifications and exposure-determining parameters of relevant product groups in a comprehensive fashion. In addition to wireless phones (e.g. DECT) and local wireless networks (WLAN/WPAN) non-standardised devices (e.g. baby phones) were investigated. Furthermore, a forecast of future standards of device of this kind was developed. Standards were defined for measuring methods and for the interpretation of measured results, taking into consideration operational frequencies, modulation pattern, media access and duplex schemes as well as the operational mode depending on current data traffic. Extensive computer simulations were conducted for devices operating close to the body (SAR calculations in homogeneous and anatomic FDTD body models) and for large-scale and complex exposure scenarios (e.g. parallel DECT and WLAN installations in the office environment) as well as for combined scenarios (simultaneous exposure through devices operating close to the body and from sources further away). Individual devices and typical office environments were investigated with measuring techniques. The SAR value was measured for devices which are designed to come into contact with the body or where body contact cannot be excluded. Measurement and calculations conducted during the course of the project showed that the personal exposure from DECT-, WLAN- and Bluetooth devices in typical scenarios is below 0.1% of the reference values set by the EC recommendation 1999/519/EU. Compared to basic limit restrictions, measurements of SAR values averaged over 10 g have led to maximum values of 0.1 W/kg during extreme proximity field exposure through WLAN or Bluetooth devices on a homogeneous flat dummy filled with tissue simulating fluid. Numerical simulations using an anatomic body model also showed maximum values of about 0.1 W/kg at the contact point/area between device and body. It is to be taken into consideration that the examined WLAN-PCMCIA card only used half of the maximum allowed transmitting power of 100 mW EIRP. The maximum SAR value for a generic model of DECT mobile telephone typically used at a head position was calculated using an anatomic head model (averaging over 10g). Its value was below 0.05 W/kg. The highest exposures were found in the vicinity of the most powerful device (baby phone – transmitting power 500 mW). Measurement of the SAR value at two different positions (each with contact of the device to the dummy) resulted in values of 0.07 W/kg and. 0.13 W/kg respectively. Again, in this specific case, compliance with the 2 W/kg limit value was observed. The frequency-selective channel or band-power-measurement with high-quality spectrum analysers using RMS detectors has turned out as the most suitable measuring method to determine emissions of sources away from the body, in particular with technologies with a changing duty cycle or frequency hopping scheme. The detailed results of the project can be found in the interim and final report, which are available for downloading. Download of reports as PDF file: First interim report (2.483 kB) Second interim report (1.489 kB) References
Conclusion Even simultaneous exposure through several devices operated away from the body used for wireless transmission of information in the home or office, evidently lead to a total exposure well below current limits. An exceedance of the limit values by the investigated devices is improbable even when operated with body contact and in adverse conditions such as the duty cycle depending on data traffic. In common usage the typical maximum exposure levels are significantly below the current limit value. Exposure of devices operated away from the body is usually dominated by additional devices operated close to the body. Investigation of baby showed that devices with very different maximum transmitting power and coverage are currently available on the market. This should be taken into consideration when selecting suitable devices. |