Hi folks, dumb question - apologies if covered elsewhere.
Are these radios full duplex? F’rinstance, if I have two devices nearby and we both send a message to each other at the same time… is message lost, or are the devices able to figure this out?
cheers, Andy
I believe the radios themselves are not truly full duplex (can’t receive and transmit at the same time (unless you have one of the multiradiochannel devices found in expensive gateways)). But the software takes care of managing the radio and it acts like it is full duplex. And meshtastic is designed to retransmit for other reasons as well.
Consumer wifi is actually half duplex, but the frames are so short, frequent, and managed so you don’t notice.
thanks for the info! So when acting as a repeater/relay… is message loss uncommon when usage is high?
ANd if I send a message and it doesn’t go though, do I get any kind of message or indication that it was unsuccessful?
Sorry one more noob question: this is unrelated to LoRaWAN, right?
cheers… Andy
Message loss will be related to the signal to noise ratio. If there is not enough signal parts of the message may not be received and because of how messages are handled it is an all or nothing scenario at the level Meshtastic process the message, if that issue is on going the retry attempts will fail. The radio layer is designed to deal with noise and week signals in a few clever ways so a momentary loss of signal doesn’t result in a total failure to receive. There are varying levels or error correction built in.
There is a feature in Meshtastic to get confirmation that a message was received. If you want to understand the limits of this check out Two Generals' Problem - Wikipedia
Also, depending on how a message is sent the ack (acknowledgment) could be that any radio part of that mesh / channel heard it, and you heard their ack. Or a specific radio heard it and you heard it’s ack.
I don’t think Meshtastic has been tested outside peoples workshop for ‘high usage’ issues. Some people have setup a situation where the radios are exchanging messages near the theoretical limit as it is understood to isolate bugs. And the project has been updated based on that feedback.
If it is important enough radios should be deployed in a way that ensures a good safety margin of signal to noise and messages should be managed in such a way they are not sent so fast that retry attempts do not have time to be processed if necessary.
In your experience, is there a rule of thumb SNR to look for when testing range and placement of nodes? I’m using the rangetesting plugin and find the SNR can vary a fair bit depending on moving just a few steps sideways (transmitting through forest…) What would excellent, good, fair, poor numbers look like?
Cheers
Thank you. Radio stuff is pretty new to me. I’m on the long/slow setting. Does that mean that -20 is the limit of my range? and anything approaching -7 is better? I have the stock antennas although I don’t know their actual dba.