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To conclude this chapter, I would like to discuss a little bit about energy consumption.
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Obviously, the energy consumption is directly linked to the autonomy of the device, and we need to
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understand which parameter influence its value.
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The main parameter is the Time On Air,
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so the time used by the transceiver to send data. The Higher the Time On Air the higher consumption.
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And the Time On Air is directly linked to the Spreading Factor.
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As we already said, the higher the Spreading Factor the higher the symbol time.
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So the higher the Time On Air. 
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Then the number of data to transmit and finally the bandwidth and coding rate.
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Another element that will influence consumption is the fact that it can be collisions.
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What happened when they are collisions?
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Actually, nothing if you don't ask for an acknowledgement. And in that case the frame is just lost.
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But if you ask for a confirmation,
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so the protocol will spend time to confirm or retransmit in case of a packet loss.
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And all this transmission will consume energy.
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Then, there is a duty cycle parameter.
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1% is the maximum.
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But obviously there are many use cases where only a few LoRaWAN packets a day are enough.
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And then you can save power.
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Next of course, there will be the transmitted power.
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In Europe, the limit is 14 dBm, which correspond to 25 milliwatts.
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But of course, if you close to a gateway, there is no need to send this much power.
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And finally, what does a LoRaWAN device do between two transmission ?
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Usually nothing.
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And the LoRaWAN transceiver and the application MCU (Microprocessor Unit).
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should reach the deepest sleep mode to reduce the power as much as possible.
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So to illustrate the power consumption point, we can just play with a little online calculator to get an idea of the autonomy we can expect.
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In this calculator, we have to enter a few parameters.
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I will keep my temperature sensor with one byte and assume that I need to send my data every one hour.
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Finally, I will use a well known AA-type battery.
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When we look at the results, the Time On Air generated are the one we had for LoRaWAN transmission.
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For a LoRaWAN transmission, we need to had the LoRaWAN Header, which is 13 bytes.
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So there are actually 14 bytes in the LoRa frame.
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So I just change this value and I've got now the right Time On Air.
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And the calculation gives the following result in the worst case will have 4 years and 11 months
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for autonomy.
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And in the best case, 17 years and two months, which is huge.
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What does these figures actually represent?
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They represent the consumption of the LoRa module.
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We should also add the consumption that is linked to the application.
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For example, if you're processing data for a long time, obviously if you have many sensors and so on.
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Because they haven't been taken into account in this simulation. Then what's the worst case ?
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The worst case would be a high Spreading Factor and a high transmission power.
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Obviously, the best case would be exactly the contrary.
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So a low Spreading Factor and a low transmission power, well, this still gives you a rough idea,
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so just play along with it.
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Change the parameters and try to see what's the autonomy you can expect for a LoRaWAN device.