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Based in France, Sercel is a global leader in the seismic acquisition industry. In 2019, Sercel announced that it was working on an integrated structural health monitoring solution called S-Lynks for dams, bridges, buildings, and other types of civil structures.
A typical Sercel S-Lynks system is made of 20 nodes and 2 gateways – the exact number can differ according to the size of the structure being monitored and preliminary studies. Each of these nodes are embedded with the QuietSeis™ MEMS accelerometer which measures vibrations induced from wind, road traffic or other natural noise. For Sercel to be able to remotely monitor structural health, the sensor data needs to be transmitted from its enclosing node to the cloud through wireless networks. This is where the Internet of Things (IoT) comes into the picture.
Transmitting data from multiple nodes for every structure can increase the cost of connectivity to a point where the solution becomes unviable. To find a way around this problem, optimize battery power and simplify other technical complexities in its intricate IoT project, Sercel chose Sierra Wireless Octave, the all-in-one edge-to-cloud solution for connecting industrial assets to the cloud.
Sercel’s S-Lynks system allows multiple gateway deployments on each structure, which receive data from the nodes on the structure. Having multiple gateways enables the system to offer a redundancy solution. All gateways are embedded with the WP7702 module, the edge component part of Octave’s IoT infrastructure.
The data from the nodes is transmitted to the gateway using a WiFi-mesh; but since there is no external power source supporting the nodes, Sercel had to make sure that the WiFi connection did not drain their battery levels. To optimize the use of WiFi and preserve battery life, Sercel has developed an advanced power saving function, which includes data optimization and deep sleep mechanisms.
Each of the nodes and the gateway is equipped with a processor; data collected by the sensors is therefore pre-processed locally on the nodes. Once this data is aggregated on the gateway, the gateway’s processor sends this data to the WP7702 module via the Octave Resource Protocol (ORP), a simple ASCII-based communication protocol.
At this stage, the WP7702 plays a critical role. The module, which supports Low Power Wide Area Networking (LPWAN) technologies, orchestrates and organizes the transfer of the aggregate data from the gateway to the cloud using LTE-M. In doing so, the WP7702 module performs seven essential functions:
Octave, via the WP7702 module, performs authentication of the nodes and the gateway from the edge to the cloud, and enables secured commands to be sent from the cloud to the gateway to the nodes.
The stream of messages from the gateway to the cloud are tagged with node IDs, and optimized using LW-M2M protocol.
Because nodes are not connected to an external power supply, Octave monitors their battery level.
Octave’s embedded SIM is able to choose the best available network at any time and place.
Being an all-in-one solution, Octave also comes with a cloud API enabling Sercel to inject data into its backend IT system; likewise, Sercel can also send commands to the Octave edge devices.
Without Octave, Sercel would have spent months to build its own IoT solution; the process would have been very complex and time-consuming given the specialized knowledge and technologies required in telecommunication, IoT security, system integration, device management, and in other areas that constitute an IoT infrastructure.
Structural Health Monitoring
Sierra Wireless Octave™
All-in-one Edge-to-Cloud Solution