The clear advantages brought by wireless sensor networks (WSNs) for environmental observation or security systems are increasing the focus on these node-based sensor platforms. Because it is difficult to adapt the behavior of WSNs after they have been deployed, researchers are now looking to develop software-defined WSNs (SDWSNs). Such networks hold the promise of rapid customization and adaptability. In hopes of bringing these networks to fruition, a group of researchers has teamed, thanks to support from Japan’s Strategic Information and Communication R&D Promotion Program and Grants-in-Aid for Scientific Research. These researchers include Toshiaki Miyazaki, Shoichi Yamaguchi, Koji Kobayashi, Junji Kitamichi, Song Guo, Tsuneo Tsukahara, and Takafumi Hayashi.

Software-defined sensor networks

To control the behavior of the SDWSN, the team uses wireless communications to assign roles to the individual sensor nodes. This requires a role generation and delivery mechanism as well as a reconfigurable sensor node. Each sensor node is equipped with a microprocessor unit (MCU) for general program tasks and a field-programmable gate array (FPGA) to handle sensor and data processing efficiently.

The role generator is composed of a scenario compiler that generates roles based upon the scenario description, which specifies the behavior of the sensor nodes. These roles are transmitted wirelessly and downloaded using a multi-hop wireless network. A base station and control terminal are required to operate the role generator. The delivery mechanism relies on a wireless-network access point powered by a 920-MHz RF module.

Power consumption of the sensor node was measured at 220 mW with the majority of power consumed by the RF module. Using a 32-bit central processing unit (CPU) instead of the MCU, the power consumption increased to 899 mW. The CPU version could run up to 20 hours using a 10,000-mAh battery. In contrast, the MCU version could potentially run for more than 80 hours at a rate of 25 packets per second. See “A Software Defined Wireless Sensor Network,” 2014 International Conference on Computing, Networking, and Communications (ICNC), Feb. 2014,  pp. 847-852.