How to interpret a noise scan result
This section gives some guidelines on how to interpret a noise scan result with general indications and troubleshooting advices.
General indications
For a clear and accurate view of the result, plot a logarithmic average graph.
About the values themselves:
The thermal noise floor is -174 dBm/Hz, which gives a theoretical and expected noise level of noise level of -120 dBm because -174 dBm/Hz gives -123 dBm/125 kHz + 3 dBm of Noise Factor = -120 dBm
The lower the RSSI measured by the Base Station, the better.
Following are some reference values for channels using 125 kHz bandwidth:
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< -130dBm: impossible result. The RSSI measured by the Base Station should not be even lower than the thermal noise floor (around -120dBm).
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-130 to -120 dBm: wrong result. The RSSI measured by the Base Station should not be even lower than the thermal noise floor (around -120dBm). Probably a measurement issue on the Base Station.
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-120 to -110 dBm: excellent result. No signal or interferences around the Base Station.
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-110 to -100 dBm: very good result. Very few interferences around the Base Station.
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-100 to -95 dBm: good result. Little interferences around the Base Station, but not disturbing the Base Station.
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> -95 dBm: bad result. Signal coming from an end-device or strong interferences around the Base Station. Do not use the corresponding channel.
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≥ 0 dBm: impossible result. RSSI cannot be null or positive.
Following are some reference values for channels using 500 kHz bandwidth:
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< -125dBm: impossible result. The RSSI measured by the Base Station should not be even lower than the thermal noise floor (around -114dBm).
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-125 to -114 dBm: wrong result. The RSSI measured by the Base Station should not be even lower than the thermal noise floor (around -114dBm). Probably a measurement issue on the Base Station.
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-114 to -105 dBm: excellent result. No signal or interferences around the Base Station.
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-105 to -95 dBm: very good result. Very few interferences around the Base Station.
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-95 to -90 dBm: good result. Little interferences around the Base Station, but not disturbing the Base Station.
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> -90 dBm: bad result. Signal coming from an end-device or strong interferences around the Base Station. Do not use the corresponding channel.
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≥ 0 dBm: impossible result. RSSI cannot be null or positive.
Important The noise can be high for some frequencies as soon as it is not inside channels in use.
To display the data without the extreme RSSI values, plot a RSSI percentile graph with the percentile set to 50%, which corresponds to the median RSSI value for all frequencies.
Troubleshooting
Plot the linear average graph to better detect if there are sporadic interferes with high power level. If there is a peak on a frequency used: plot a RSSI distribution graph for this frequency. It permits to see the repartition of the measured values, and the impact of extreme values for this frequency.
It is better to execute more than one noise scan on a given Base Station to average any transient problems: there could be an interferer during a specific time in the day or your own LoRaWAN® traffic can be interpreted as interference.
Important If there is always a peak on a specific frequency for different noise scan results of the same Base Station, it may be necessary to change the frequency of the corresponding channel to use a less noisy frequency. In that case, contact Actility.