# Modeling and Analysis of Wearable Antennas
## 4 Conclusion and Future Prospects  
The field of sheet waveguides provides a new method of communication. It is conceivable to develop a direction to replace a part of wired communication and a new field expected to utilize wireless communication. In this paper, application examples to sensor/personal/body area network are considered depending on the communication range. There is a rising interest in ubiquitous sensor networks that can be used anytime and anywhere, whether indoors or outdoors. The number of applications, therefore, continues to increase, making it difficult to create a unified network for everything. Because there are various wireless sensor networks depending on applications [30], infrastructure technology supporting these networks is required. For this infrastructure, functions such as providing power wirelessly, location estimation, time synchronization, etc. are required. In outdoor wireless sensor networks such as ecological observation and forest monitoring, these functions can be provided to sensor networks using solar cells, GPS systems, mobile phones, etc. However, in indoor environments, it is possible to synchronize time with mobile phones, but otherwise, it is difficult to achieve these aims at present. In order to build an infrastructure indoors, it has been proposed to embed a sensor as a smart building material in a wall of a planar building and connect a network on the surface [19], and to construct the network, a sheet-like waveguide may be applied. For example, it is possible to supply power to a sensor connected to a sheet by connecting a high-frequency power  
Figure 10: Transmission characteristics of the smart suit. (**a**) Transmission characteristics on the back and front of the human body, (**b**) Transmission characteristics on the front of the human body. source to the sheet-like waveguide. Moreover, by combining a plurality of antennas in advance on the seat, the arrival direction can be estimated so that the position of the sensor can be estimated, and time synchronization and the like can be easily realized by communication via a transmission line. As described above, a sheet waveguide is suitable for application as infrastructure for a wireless sensor network. Communications limited to a narrow range can also be performed by the sheet-like waveguide. Wireless LAN is commonly used in offices and the like, but leakage of information outside the office and intrusion from outside the office are problematic and various security measures are being studied. Since many terminals are connected to the access point in the office, it is difficult to guarantee the stability of the connection and the communication speed. In order to solve these problems, data encryption is used for security, and for packet leakage methods using coaxial cables and the like are considered [31]. However, the encryption technology must always be ahead of the decryption technology - hacking, and in fact, methods of breaking the encryption are known and are easily available on the Internet. A method of constructing a wireless LAN system using leaky coaxial has been applied to railway radio such as Shinkansen, radio communication in a tunnel and disaster prevention radio system of an underground shopping mall is also considered. However, in many cases, in the 5 GHz band and the 2.4 GHz band like the wireless LAN, the leakage coaxial loss becomes a problem and realization is difficult. Also, a cable of several tens of meters can be used for applications covering the entire office, but it is not suitable for wireless environments of individuals with high security, that is, for LANs of about several meters. Since the size of a desk, 1 m to 2 m can be thought of as the range that can be managed by the user, the system that allows communication only to wireless devices close to the sheet-like waveguide can be expected to be applied to wireless LAN with high security.