Packet suppression protocol for a regional protection system using a wireless ad-hoc network

We are currently developing a regional protection system in which children have terminals, and transponders installed at various locations receive packets sent from these terminals via a specified low-power radio system. The packets are then transmitted to a server so the positions of the children can be inferred from that information. With the ARIB STD-T67 access protocol used in this system, collisions frequently occur at locations where there are many terminals. Therefore, the authors improved a protocol in which frequent collisions do not occur, even when as many as 150 terminals gather in the same place. However, it was impossible to prevent frequent collisions when many terminals are concentrated in one place, such as in a school. A new access protocol was developed in this research to deal with this problem. In this protocol, transmission by terminals is suppressed at specific locations, and then resumed after the terminal moves away from those locations. However, the position of a terminal must not be lost when its transmission is being restricted. In this presentation, we propose this new access protocol, and evaluate its effectiveness.