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Rajeev PiyareRajeev Piyare 

Low power listening using SX1276

Hello Team,
First, I would like to explain my application scenario. I have two nodes, one acting as a sink and the other as a sensor node. Currently, both the nodes are always on and listening. I am trying to implement receiver initiated MAC where the sink initiates the data collection. My main aim is to duty cycle both the nodes something similar to low power listening MAC where the Sink will first tx a preamble before sending the command to end node. On the end node side (receiver side) it will be duty cycled where it will switch between RX and TX. When the preamble is detected, the end device will switch to tx mode and send the data to sink. Other times it will keep checking for any data in a periodic manner as shown in the figure.
Has anyone done anything similar like this? If yes or any suggestions or guidelines will be really helpful.

SebastienSebastien (Semtech Corporation) 
Hi Rajeev,

This method is extremely widespread in the industry, for instance in Drive-by smart-metering scenarii where an interrogator is present and sends a long preable to wake-up a device for seldom interrogation. It is all a trade-off between Rx duty-cycle (energy efficiency on the Rx), length of the interrogating preamble, and over-hearing.

The source has to be clever-enough to detect false interrogations, and adapt itself to fake interrogations, for example due to a raise in the noise floor in the channel. Typically, wake up on RSSI is used, and self-adapting RSSI threshold help mitigate over-hearing, whihc is harmful for the battery lifespan.