Landslides during heavy rainfall cause a great amount of damage in terms of both property and human life. To predict landslide disasters, we designed and implemented a wireless sensor network using our existing highly fault tolerant ad-hoc network. Since many sensors must be used, we propose a new MAC protocol that allows the network to support more sensor terminals. Our protocol is a hybrid CSMA/Psuedo-TDMA scheme which allows the terminals to decide their transmission timing independently in a random fashion. A timing beacon is not required, so power consumption can be reduced. Simulation results show that the number of terminals supported by the network can be greatly increased.

A regional protection system based on a wireless Ad-Hoc network has been in operation since 2008 in Shiojiri City, Japan. Wireless terminals transmit data packets to a server via transponders situated around the city. In this paper, a new routing algorithm that takes into account the level of congestion of the transponders is proposed. Using computer simulations, the proposed algorithm is shown to reduce the packet loss rate compared to the previous algorithm which is based on minimization of the number of hops to the server. Also, the proposed algorithm is shown be have almost the same packet loss rate as the best routing decisions obtained by an exhaustive search. Furthermore, the simulations used recreate the actual movement of terminals, so the results show what will happen in a realistic environment.