As the expansion of IoT systems gains momentum, expectations are rising for sensor devices that support LPWA technology, which can wirelessly transmit sensor data directly to the cloud. To create systems that employ this technology, there has been a demand for the development of easy-to-install miniature devices that use solar cells for convenience and low cost, eliminating the need for battery replacements.
Fujitsu Laboratories previously developed power control technology (1) that can operate a beacon using the power supplied by a solar cell. Conventionally, the variation in solar cell output power due to temperature was tolerated by increasing the size of the energy storage elements. Now, however, Fujitsu Laboratories has developed technology that achieves high energy efficiency by controlling the signal transmission time based on the temperature variation measured by a temperature sensor, thus halving the energy storage elements required for signal transmission. This has allowed Fujitsu Laboratories to successfully miniaturize the device to a size of 82 x 24 x 6 mm, creating the world's smallest LPWA-compatible sensor device that does not require spare batteries.In a test of the sensor device using this technology, Fujitsu Laboratories confirmed that the collected temperature and humidity data can be transmitted to a Sigfox base station (2) at a distance of approximately 7 km. Since it is now possible to acquire measured data even from locations where securing power and installing power cables is difficult, simply by placing these sensor devices, the maintenance-free deployment and management of IoT systems has become a reality, accelerating the on-site digitization process.
Development Background:
The adoption of IoT systems has progressed in recent years, and it is projected that by 2020, tens of billions of IoT devices will be connected to the cloud via networks. In IoT systems, the information collected from multiple sensors installed in the field needs to be transmitted and analyzed in the cloud, and LPWA has been gaining attention as a wireless technology that can transmit data directly to the cloud with low power consumption over a wide area. From a convenience and cost perspective, there are high hopes for miniaturization, which not only meets LPWA standards but also utilizes solar cells, eliminating the need for replacement.
Fujitsu Laboratories has previously developed power control technology that uses miniature circuits capable of wirelessly transmitting data over short distances using Bluetooth Low Energy (BLE). This technology enables BLE-compatible sensor devices without the need for battery replacements, provides power via solar cells, and reliably activates a wireless circuit by monitoring and adjusting the balance between power generation and consumption. However
, sensor devices using this earlier technology cannot support LPWA. This is because the transmission time required with LPWA is significantly longer than with BLE. LPWA transmits small amounts of data slowly to ensure signal quality over long distances. In effect, this means that a single transmission can require a significant amount of energy—up to approximately 1,500 times that of BLE.
About the Newly Developed Technology
: Fujitsu Laboratories has developed a new power control technology to ensure transmission power while minimizing circuit size. The advantages of this technology are as follows:
1. Power Control Technology that Allows for Power Variations with Temperature:
Fujitsu Laboratories has developed a power control technology that can regulate the timing of LPWA signal transmissions in real time, based on temperature data collected from a temperature sensor. With this technology, signal transmissions only occur when the activation voltage, which varies with temperature, is at its maximum to prevent it from falling below the minimum operating voltage for the LPWA module (Figure 3). By using energy efficiently, it is possible to tolerate variations in the power consumed by the wireless circuit or the energy generated by the solar cells due to temperature. This eliminates the need for the excess energy storage elements that were previously required to meet power demands.
2. Energy Monitoring Technology Reliably Activates the Temperature Sensor
For the power control technology to function reliably, the device must be able to continuously and reliably activate the temperature sensor with a minimal amount of energy. To address this challenge, Fujitsu Laboratories has developed an energy monitoring technology that analyzes voltage changes in the power supply and accurately assesses whether sufficient energy has been stored to operate the temperature sensor. This technology can prevent unnecessary shutdowns of the temperature sensor by using the minimum amount of energy based on the temperature.
Effects:
This technology was implemented using Sigfox, an LPWA standard, creating the world's smallest sensor device (82 x 24 x 6 mm) that supports LPWA communications without the need for battery replacement. Fujitsu Laboratories verified that temperature and humidity data could be transmitted once every ten minutes, for seven days, directly to a base station approximately 7 km away, in an environment with 4,000 lux illumination. Fujitsu Laboratories also verified that the data could be visualized through the Fujitsu Cloud Service K5 IoT Platform, Fujitsu Limited's IoT data utilization platform service, which has received the Sigfox Ready Program for IoT PaaS certification as an IoT platform that connects to the Sigfox cloud (Figure 5).
This means that sensor data can be easily acquired in the cloud simply by configuring sensor devices, even in locations where securing power or installing power cables is difficult. This will enable the maintenance-free installation and management of IoT systems, accelerating the digitization process in the field.
Future Plans:
Fujitsu Laboratories will continue field trials for the real-world use of these sensor devices, incorporating this technology into the Fujitsu Cloud Service K5 IoT Platform and Fujitsu Frontech Limited's sensor solutions as connected devices, with the goal of commercialization in fiscal year 2018. Furthermore, we will continue developing technologies to miniaturize sensor devices.
Comment from Yoshihito Kurose, President of KYOCERA Communication Systems Co., Ltd. (KCCS):
As IoT utilization is expected to continue increasing, KCCS predicts that solutions utilizing the low-power characteristics of the Sigfox network will be developed in many industries. KCCS believes that Fujitsu Laboratories Ltd.'s development of a sensor device that does not require battery charging via a solar battery will promote the use of Sigfox not only in Japan but also worldwide. As the Sigfox operator in Japan, KCCS is working with Fujitsu Laboratories Ltd. and other partners to enable everything to be connected to the Sigfox network and contribute to creating a safe and livable society.
________________________________________
• [1] Power Control Technology Development
Fujitsu develops the industry's first flexible IoT support beacon that does not require battery replacement (Press release, March 25, 2015) http://www.fujitsu.com/global/about/resources/news/press-releases/2015/0325-02.html
• [2] Sigfox
Ltd. is the sole network service provider in Japan.
