# Smart Gateway for Healthcare Networks Based on Beam Steering Technology
## 5 Radio Propagation Experiments in an LOS Environment
As can be seen from Figure 23b, the cause of this characteristic appears to be reflected waves from not only the walls, ceilings, and floors, but also from an aluminum pole close to the transmitting antenna and a metal switchboard near the receiving antenna, indicating that slightly stronger fading has been observed. This fading phenomenon also occurred in the  
Figure 24: CDF characteristics of the received power in short-term fading. long-distance propagation experiment. Although we did not perform the AOA estimation using the proposed antenna in this room, it is expected that the angle of the incoming wave can be estimated in this environment (\(K=4\) dB), as described in Section 4. Figure 25 shows the measurement results of the instantaneous response with respect to the antenna input terminal power with a division pattern of the beamforming area shown in Figure 18 as the parameter. Figure 18a,b indicate the case of 90\({}^{\circ}\) intervals from 0\({}^{\circ}\) and the case of 90\({}^{\circ}\) intervals from 45\({}^{\circ}\), respectively. Figure 18c,d are the case of 45\({}^{\circ}\) intervals and the case of 22.5\({}^{\circ}\) intervals, respectively. The received power in Figure 25 is a combination of the results measured by forming each beam shown in Figure 17 on a personal computer (PC). In addition, the black lines are the results of using a half-wavelength sleeve dipole antenna as the receiving antenna. The broken lines are the expected results when measured in free space and are calculated using the following equation:  
\[P(\phi)=G_{t}(\phi)G_{r}(\phi)\left(\frac{\lambda}{4\pi d(\phi)}\right)^{2} \tag{15}\]  
where \(G_{t}(\phi)\) and \(G_{r}(\phi)\) indicate the radiation gain at \(\phi\) of the transmitting and receiving antenna, respectively. \(\phi\) is the angle of the direct wave when the direction of the starting point is defined as 0\({}^{\circ}\), as shown in Figure 23a, and its values vary with the movement of the arm-swinging dynamic human phantom. \(d(\phi)\) is the distance between the transmitting and receiving antennas. When the human phantom reaches an end point, the angle \(\phi\) is  
Figure 25: Instantaneous received signals of the proposed antenna: (**a**) 90\({}^{\circ}\) intervals from 0\({}^{\circ}\); (**b**) 90\({}^{\circ}\) intervals from 45\({}^{\circ}\); (**c**) 45\({}^{\circ}\) intervals; and (**d**) 22.5\({}^{\circ}\) intervals. 63.4\({}^{\circ}\). The broken curves for the proposed antenna, excluding Figure 25a, are not smooth because of beam switching, as illustrated in Figure 18.  
It can be seen from Figure 25 that the experimental results in the classroom are reduced by the fading effect compared to the expected values in free space, as shown by the broken curves in the Figure. In addition, as the phantom moves, the receiving signal level decreases because the path loss increases with increasing distance between the transmitting and receiving antennas. Despite this, the received signals for all the division patterns are increased by forming the beam toward the direction of the human phantom, when compared to the results for the dipole antenna. Comparing the four measured results using different division patterns, we can see that the result for the case of 90\({}^{\circ}\) intervals from 45\({}^{\circ}\) shown in Figure 25b is slightly lower than the others. The CDF characteristics were analyzed to perform a statistical validation of the propagation measurement results obtained in the classroom. Figure 26 shows the CDF characteristics of the instantaneous response with the beamforming division area as the parameter. The received power is normalized by the median value measured by the dipole antenna. The pink and green curves indicate the case of 90\({}^{\circ}\) intervals from 0\({}^{\circ}\) and the case of 90\({}^{\circ}\) intervals from 45\({}^{\circ}\), respectively. The blue and red curves are the case of 45\({}^{\circ}\) intervals and the case of 22.5\({}^{\circ}\) intervals, respectively. The black curve is the dipole antenna.