1/3 - Transmission strategy
Each use case comes with its own feautures: physical environment of the device, specific amount of data to transmit or level of criticity of the data delivery time. To answer those different needs in the most efficient way, one can adapt and customize its transmission strategy.
What to transmit? Useful data from sensors (position from a GNSS receiver, temperature, pressure…), or user-specific messages. Message size depends on the precision required and the nature of the information to transmit. For example a 10m resolution GNSS location can typically occupy 8 bytes of data.
How to transmit? Messages are transmitted with a fixed repetition period, defined in accordance with the use case needs (amount of data to transmit, maximum age of the data…). To ensure a good reception considering the deployment constraints (transmission power, environment…), each message is usually repeated 3 to 5 times. Different transmission strategies exist, including data cycling and message interleaving, for a more efficient communication and thus an economy on battery consumption.
When to transmit? Kinéis relies on a constellation of polar low-earth orbit satellites that rotate at an impressive speed of nearly 8km/s around our planet, each satellite achieving global coverage in less than 12 hours. For a connected device, the communication is possible when a satellite passes above it, for a duration of up to 12 minutes depending on the maximum elevation reached by the satellite during the pass (passage angle in relation to the horizon).
4 types of transmission strategies are possible, depending on user needs and regulatory possibilities: