OREANDA-NEWS. Toshiba has developed low-power multi-hop wireless network technology that can operate on battery power for over 10 years and can collect over 99.999% of data from sensors deployed over a wide area through wireless relaying. This technology makes it possible to monitor, with low maintenance costs, natural environments where there is a risk of disaster, as well as buildings, bridges, tunnels, and other aging structures. The details of this technology will be presented on 23 September 2016 at the IEICE Society Conference to be held at Hokkaido University.

In recent years, aging of public infrastructure and natural disasters have become growing problems. Attention has therefore turned to sensor networks in which sensors and communication devices are fitted to target objects and data collection and monitoring are performed via a network with the aim of reducing casualties due to accidents and disasters. However, the communication devices need to be installed in locations with rugged natural environments and poor accessibility, creating the problems of difficult installation and maintenance during operation. A further problem is that monitoring over a wide area requires considerable effort.

To address these problems, Toshiba has developed wireless communication technology that offers highly reliable data collection with low maintenance costs. The communication devices employ special low-power wireless devices that operate in the 920-MHz band, which allows for long-distance communication exceeding 1 km in line-of-sight environments and easy deployment because no license is required. The devices are also easy to install because they are battery powered and do not need communication or power lines. Furthermore, data collection over wide areas is achieved through relay transmission (multi-hop communication) in which the sensor data transmitted by a wireless device are received and then retransmitted by surrounding wireless devices.

The system is equipped with a function that, when communication fails during data transmission, selects a new communication partner with a good communication status from among the surrounding wireless devices and retransmits the data. This function enables over 99.999% of sensor data to be collected. Furthermore, for the purpose of power-saving, the communication timings are synchronized and time-division communication is implemented, in which the wireless devices are made to sleep in time bands when communication is not needed. A mechanism was developed that autonomously determines the sleep timing for wireless devices based on the number of wireless relay hops needed for data collection and a self-assigned device number, enabling long periods of sleep even during multi-hop communication. This greatly reduces power consumption, and computer simulations have confirmed that maintenance for battery replacement is not needed for periods exceeding 10 years in all communication devices. Furthermore, results supporting this have been obtained from field communication trials for a period of 16 days using prototype devices.

These technologies can deliver both reduced power consumption (battery operation for over 10 years) and high reliability with a data collection rate of over 99.999% through a wireless network using the 920-MHz band.