RF exposure analysis for multiple Wi-Fi devices in enclosed environment

Abstract

Abstract-Wi-Fi devices operated inside a metallic enclosure have been investigation in the recent years. A motivation for this study is to investigate wave propagation inside an enclosed environment such as elevator, car, aircraft, and spacecraft. There are performances and safety concerned that when the RF transmitters are used in the metallic enclosed environments. In this paper, the field distributions inside a confined room were investigated with multiple portable Wi-Fi devices. Computer simulations were performed using the rigorous computational electromagnetics (CEM). The method of moments (MoM) was used to model the mutual coupling among antennas. The geometrical theory of diffraction (GTD) was applied for the multiple reflections off the ground and walls. The prediction of the field distribution inside such environment is useful for the planning and deployment of a wireless radio and sensor system. Factors that affect the field strengths and distributions of radio waves in confined space were analyzed. The results could be used to evaluate the RF exposure safety in confined environment. By comparing the field distributions for various scenarios, it was observed that the Wi-Fi device counts, spacing and relative locations in the room are important factors in such environments. The RF Keep Out Zone (KOZ), where the electric field strengths exceed the permissible RF exposure limit, could be used to assess the RF human exposure compliance. As shown in this study, it's possible to maximize or minimize field intensity in specific area by arranging the Wi-Fi devices as a function of the relative location and spacing in a calculated manner.

Investigation of Microwave Electromagnetic Fields in Open and Shielded Areas and Their Possible Effects on Biological Structure

“…Measurement with a human head phantom in a shielded environment shows that the value of electrical intensity for a 6-min interval was not exceeded. A call in a shielded environment could, especially with more than one RF source may cause a rise in values even exceeding the limit values [ 13 , 17 , 18 ]. It highly depends on the type of EMF source and on what frequency in the mobile band the phone connects to the base station.…”

“…Wi-Fi devices operated inside a metallic enclosure have been investigated in [ 17 ]. A motivation for this study was to investigate wave propagation inside an enclosed environment such as elevator, car, aircraft, and spacecraft.…”

Modal Analysis Based on an Integral Equation Method for Characterizing Wireless Channels in a Fully-Enclosed Environment

“…If each pulse stands for one bit, it appears readily feasible for channel A to accommodate wireless communication with data rate of at least 20 Mbps (which corresponds to 50 ns pulse repetition interval). It should be noted that data rate on the order of Mbps is very difficult to accomplish in fully-enclosed environments (according to [3][4][5][6][7][8][9][10][11][12], for instance), whereas 20 Mbps may not be considered a high data rate in regular environments. The phenomena displayed in Figure 14 and Figure 15 are similar to those in Figure 13, except that the received pulses have weaker amplitudes in Figure 14 and Figure 15.…”

“…Numerous research efforts have been reported on characterizing wireless communication channels in fully-enclosed environments by the means of simulations and/or measurements [5][6][7][8][9][10][11][12]. The results in [5][6][7][8][9][10][11][12] unequivocally reveal highly-dispersive wireless channels, which make it difficult for the data rate of wireless communication to reach Mbps. In recent years, wireless power transmission in fully-enclosed environments is investigated by many researchers [13][14][15].…”

“…In this paper, a semi-analytical modal analysis is conducted for the purpose of characterizing wireless channels in fully-enclosed space. Compared with the approaches in [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], the semi-analytical modal analysis is capable of yielding explicit physical insights toward efficient wireless communication and/or wireless power transmission in fully-enclosed environments. Specifically, the modal analysis is based upon an integral equation method.…”