210 nrf52840

[arquiteturade...@gmail.com]

In my application

210 nrf52840 will transmit a UDP counter each 1.X seconds...only 4 bytes...

Will i have collision problems ?

Wich should be the better interval between transmittions ?

[Jonathan Hui]

210 Thread devices transmitting a message every second is probably more than Thread can handle.

Thread's IEEE 802.15.4 2.4 GHz PHY has a data rate of 250 kbps. A typical IEEE 802.15.4 MAC frame that carries a UDP/IPv6 datagram with 4 bytes UDP payload is around 70 bytes. 70 * 8 * 210 is around 118 kbps, just sending MAC data frames. Then you still need to account for other overheads (MAC CSMA/CA backoff, MAC acknowledgments, control messages, etc.). Also, given that Thread is a multi-hop mesh network, forwarding messages also cuts the usable channel capacity to one-third, accounting for the fact that neighboring devices need to forward the message. If the environment is lossy, then you also need to account for retransmissions.

How much data you can reasonably push will largely depend on the factors I mentioned above. But to start, I would suggest something closer to 1 minute rather than 1 second. Also, if you can afford latency, I would suggest aggregating multiple data points into a single message to reduce the overhead mentioned above.

Hope that helps.

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Jonathan Hui

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