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DPerez
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2020/10/09 02:42:09 (permalink)
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RSSI to distance

Hi there,
 
First of all, I would like to introduce you roughly the project we are working with right now.
 
It is mainly a project for industry 4.0, where we are meassuring different sensors (temperature, humidity, and so on) with some devices, and sending this information through LoRaWAN by using the RN2483 Microchip module. So far so good, since we receive every single data in the server side, but there is one thing we will need as well soon, and it is a translation between the RSSI and its range in meters/kilometers.
 
We have the following information for indoor cases:
https://en.wikipedia.org/wiki/ITU_model_for_indoor_attenuation
 
What we need is the same for outdoor cases.
 
We truly understand the difficulty of this, because the signal can be affected by many things, just like obstacles, the weather conditions and so on... but it is something included within the specifications, so we have to do it, even if it is only a tentative value.
 
Any information or tips would be appreciated. Looking forward to hearing from you.
 
Kind regards.
Daniel.
#1

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    MikeBP
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    Re: RSSI to distance 2020/12/15 14:37:09 (permalink)
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    Just started working with the SAMR34 in a P2P setup.   Reading from lab bench to about 55m (180ft) RSSI values of 0xc2, 0xa5 0xa0,  0x9c  respectively.  Not fully clear how to decode these values - but eyeballing the code it appears that, 
    *rssi = RSSI_HF_OFFSET + RADIO_RegisterRead(REG_LORA_PKTRSSIVALUE); 
    and  
    Actual signal power is –RssiPkt/2 (dBm)
     
    but I'm not sure how to translate that value into actual dBm.  0xc2 == 192 (on same bench) where 0x9c = 158 and using -TTSPkt/2 one gets -96dBm and -78dBm  which for close range (0xc2 or -96dBm and 180ft 0x9c or -78dBm) simply makes no sense.  One should read stronger Signal values closer than far.
     
    Makes no sense to me.
     
    I tried 800ft and could not connect.   ...have yet to try in-between.  NEed to decipher RSSI's and perhaps read SNR.  
    Set to 915 (North American Freq (10) but running all else at default:
       default data rate=5 (==Spreading Factor 7, SF7)
       default BW = 125kHz
       default TX Output Power = +1dBm with PA_Boost disabled
     
    Any progress on your end?
    Mike
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    ric
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    Re: RSSI to distance 2020/12/15 16:56:48 (permalink)
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    Maybe they are signed 8-bit values.
    So 0xC2 = -62
    0x9C = -100

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    MikeBP
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    Re: RSSI to distance 2020/12/15 17:14:26 (permalink)
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    Ric - thanks much for the quick reply.  And an interesting thought,  except the code: 
    uint8_t PacketRSSI;                 // RSSI value of the receive message
    defines it as unsigned int.
     
    Been hunting through docus and API's and can find nothing that provides a means to interpret/decode this value.
     
    urg!
    #4
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