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Prior to start, list all continents and countries in which your devices will be commercialized and operated: it is necessary to provision the hardware capability and transmission configurability beforehand. Indeed, operating frequencies, radio access method, emission power, and bitrate, are fragmented worldwide.
To facilitate radio parameters management, Sigfox has defined sets of operating parameters for continents, or at least large group of compatible countries, they are called RC, for Radio Configuration.
Your use case comes with traffic volume and density requirement, and a certain level of flexibility. (...) Ingredients to cook a good traffic model are payload and periodicity. The set of constraints includes energy efficiency, regulatory and billing terms,
Select freely your device transmission periodicity based on the use case: of course, more frequent transmissions cost more energy, causing shorter battery life.
Just make sure you stay within regulatory limits! In practice, most metering devices implement an evenly spread periodic transmissions, ranging from 1 per day to 1 per 10 minutes; while alarm and tracking devices generate aperiodic series of transmissions upon a specific event, and are silent the rest of the time.
The important point is there is no specific Sigfox-related constraint: transmission over Sigfox is purely on-demand.
- In Europe (RC1), a 1% hourly duty cycle constraint apply for devices (ETSI EN 300 220), resulting in a maximum number of messages per hour.
- In Americas and most Asia-Pacific countries (RC2/RC4), Frequency Hopping constraints apply (FCC Part 15.247), and result in indirect timing constraints.
- In Japan and Korea (RC3/RC5), Listen Before Talk (LBT) timing constraints apply (STD-T108 for Japan and RadioWavesAct for Korea)
"I'm using a 12-bytes payload all the time, although I could work out a solution with 6. It doesn't change the subscription cost anyway, so why should I care?"
Well, you certainly have an energy budget to manage, and using 12 bytes when you only need 6 means that you will be wasting 20% of your energy. Can you afford that?
Why does a device's radiated power matter? Because the quality of the link between an object and the network is never a network-only concern! Indeed, in identical network conditions, devices radiating different power do not experience the same service.
Field performance is related to how well your device (antenna!) is designed for its target operating conditions. In particular: wall mounting, devices hand held by humans, or devices buried in the ground require specific attention in optimizing performance.
Remember that assessing your device performance in various situations corresponding to its target operating conditions is more than advised! the device class certification alone is necessary, but not sufficient for good field performance.