Exposure caused by wireless technologies used for short-range indoor communication in homes and offices

Abstract

In order to estimate typical radio frequency exposures from indoor used wireless communication technologies applied in homes and offices, WLAN, Bluetooth and Digital Enhanced Cordless Telecommunications systems, as well as baby surveillance devices and wireless headphones for indoor usage, have been investigated by measurements and numerical computations. Based on optimised measurement methods, field distributions and resulting exposure were assessed on selected products and real exposure scenarios. Additionally, generic scenarios have been investigated on the basis of numerical computations. The obtained results demonstrate that under usual conditions the resulting spatially (over body dimensions) averaged and 6-min time-averaged exposure for persons in the radio frequency fields of the considered applications is below approximately 0.1% of the reference level for power density according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines published in 1998. Spatial and temporal peak values can be considerably higher by 2-3 orders of magnitude. In case of some transmitting devices operated in close proximity to the body (e.g. WLAN transmitters), local exposure can reach the same order of magnitude as the basic restriction; however, none of the devices considered in this study exceeded the limits according to the ICNIRP guidelines.

A Technical Approach to the Evaluation of Radiofrequency Radiation Emissions from Mobile Telephony Base Stations

“…Reducing the highest allowed level of RF EMR, and the establishment of other legislation on High Frequency Electromagnetic Dosimetry, are issues of worldwide importance, taking into consideration the contradictory information about mobile phones, mobile telephony base stations, and their possible dangerous effects on human health [17,18,19,20,21]. …”

Power variations of wireless communication systems

“…The modulation schemes employed by 802.11b WLANs include spread spectrum, whereas the later a and g variants use OFDM. The access is TDD, using a carrier sense multiple access with collision avoidance (CSMA/CA), which means that the timing structure may be more random and dependent on the general interference from other users [IEEE Standard, 2007;Schmid et al, 2007]. An example of the power fluctuations near a laptop while uploading files is illustrated in Figure 5 a,b.…”

Radiofrequency exposure assessment of baby surveillance devices in the frequency range 400 MHz–2.45 GHz

“…Exposure to baby monitors has rarely been investigated: Schmid et al [] and Kühn et al [] investigated exposure to baby monitors within larger studies on exposure to short‐range indoor wireless communication devices. We investigated the exposure, in terms of both the peak spatial‐averaged specific absorption rate (SAR) in 10 g of tissue and the time‐averaged root‐mean‐squared (RMS) electric (E) field, induced by baby monitors operating in a frequency range between 400 MHz and 2.45 GHz.…”

“…Under the assumption of a continuous transmitted burst, the marmitek babyview 725 yielded the maximum RMS electric field of 5 V/m, which is about a factor 12 below the ICNIRP reference level. Schmid et al [2007] reported electric fields ranging from 0.4 till 1.1 V/m, which are in line with the values observed in our study. K€ uhn et al [2007] observed larger electric fields (3.2 V/m), which might originate from a 40 MHz device.…”