# Smart Gateway for Healthcare Networks Based on Beam Steering Technology
###### Abstract  
To ensure high-reliability communication in healthcare networks, this paper presents a smart gateway system that includes an angle-of-arrival (AOA) estimation and a beam steering function for a small circular antenna array. To form a beam toward healthcare sensors, the proposed antenna estimates the direction of the sensors utilizing the radio-frequency-based interferometric monopulse technique. The fabricated antenna was assessed based on the measurements of complex directivity and the over-the-air (OTA) testing in Rice propagation environments using a two-dimensional fading emulator. The measurement results reveal that the accuracy of the AOA estimation agrees well with that of the analytical data obtained through the Monte Carlo simulation. This antenna is embedded with a beam steering function employing phased array technology, which can form a beam spaced at 45\({}^{\circ}\) intervals. The ability of full-azimuth beam steering with regard to the proposed antenna was evaluated by beam propagation experiments using a human phantom in an indoor environment. The received signal of the proposed antenna with beam steering increases more than that of a conventional dipole antenna, confirming that the developed antenna has great potential of achieving high-reliability communication in a healthcare network. c 202323259 20232  
method using an antenna with omni-directivity. A receiving device must then have two distinct features: localization and beamforming. In particular, since healthcare sensors are usually mounted on the human body, the sensors' position is expected to change drastically during walking or other motion, so tracking these sensors is a very important issue. The global positioning system (GPS) is known as a high-accuracy localization method for outdoors in situations where a receiving device can be confirmed by multiple GPS satellites, i.e., in a multiple line-of-sight (LOS) environment. If the sensor device can transmit the position information obtained by GPS to the receiver, the gateway does not need to locate these sensors. However, most indoor situations are non-line-of-sight (NLOS) propagation and, therefore, GPS satellites cannot see them directly. Many sensor devices are used in buildings, factories, and houses, so there has been great interest in indoor localization methods that have a high estimation accuracy [16]. A simple localization technique is the received signal strength indication (RSSI) method. This method guesses the location using triangulation based on multi-distance calculation of the path losses between the sensor and the access points installed indoors. Similar methods exist based on the time required for communication between the sensor and the access points. Because the received signal fluctuates due to the influence of the multipath, mitigation methods to reduce the degraded estimation accuracy are being investigated [17; 18]. Consequently, these estimation methods require multiple access points, and, moreover, the access points themselves cannot identify the location of the sensor device. On the other hand, a method using channel state information (CSI), which is based on the radio propagation characteristics between terminals, has also been reported [19; 20]. This method localizes the position based on the amplitude and phase difference between multiple transmitting antennas and multiple receiving antennas. The localization method based on CSI achieves a high accuracy estimation, but it requires specific hardware and software. One of the smart antenna systems that has the required attributes of localization and beamforming is the electric-steering parasitic array radiator (ESPER) antenna [21]. This antenna consists of an active element at the center and several parasitic elements arranged in a circle. The beam is created by terminating the parasitic elements with optimum load impedances depending on the desired direction.