RSSI question

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#1
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Hi !

I'm working with ATmega128RFA1 with PA, LW_mesh.

My question is:

from your experience which is bottom limit of RSSI (in hex) required for I would say reliable communication?

My app is going to be on open space.
My problem is that I have chained network, so I would like to know how to determine distance between routers.

I observe RSSI as hex value in:

 
static bool appDataInd(NWK_DataInd_t *ind)
{
	lqi = ind->lqi;
	rssi = ind->rssi;	
		
	AppMesage_t *msg = (AppMesage_t*)ind->data;
	
	for(int i=0; imessage[i];
	}
		
	return true;
}

Ideas and suggestions are welcome,

Thank you !

Last Edited: Fri. Oct 16, 2015 - 01:43 PM
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It is impossible to reliably determine the distance from RSSI. And there is no limits for reliable communication. RSSI is useless in that respect.

LQI shows how reliable your communication is and there is even a graph in the datasheet that shows how LQI relates to probability of frame loss.

NOTE: I no longer actively read this forum. Please ask your question on www.eevblog.com/forum if you want my answer.

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Generally a channel with random noise is reliable at 6dB signal-to-noise ratio. 3dB is reliable with error correction. Low LQI at high S/N means the modulation is not what the receiver is expecting.

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dak664 wrote:
Generally a channel with random noise is reliable at 6dB signal-to-noise ratio. 3dB is reliable with error correction. Low LQI at high S/N means the modulation is not what the receiver is expecting.
Yes, for a given radio type and modulation mode, absent any interference and with no fade margin.