AMBIENT RADIOFREQUENCY POWER: THE IMPACT OF THE NUMBER OF DEVICES IN A WI-FI NETWORK

• Published in: Health physics (1958) Vol. 96; no. 6; pp. 629 - 635
• Main Authors: Malone, David, Malone, Lesley A
• Format: Journal Article
• Language: English
• Published: United States Health Physics Society 01-06-2009; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Biophysical Phenomena; Data transmission; Environmental Exposure; Health physics; Humans; Local Area Networks - instrumentation; Models, Theoretical; Occupational Exposure; Protocol; Radiation; Radio frequency; Radio Waves - adverse effects; Radiometry - statistics & numerical data; Wireless networks
• ISSN: 0017-9078; 1538-5159
• DOI: 10.1097/01.HP.0000341329.79077.29

This paper considers how the total radiofrequency power varies as the number of devices in a Wi-Fi network increases. Under the assumption that all devices in the network always have data to transmit, we show that work from network engineering can be adapted to calculate the total transmitted power, accounting for the possibility of multiple devices transmitting at the same time. The paper focuses on total transmitted power as it gives an upper bound on exposure and makes the impact of multiple devices clear. The results show that the number of devices does have a significant impact on the radiated power. For example, one station transmitting small packets in unicast mode gives about half the nominal power value; to reach nominal value around 25 devices are required, and 150% of the nominal value is achieved around 350 devices. We see that 802.11’s transmission protocol is usually effective in limiting the power even in very large 802.11 networks.