Power gain and sensitivity
Last updated
Last updated
When configuring a node and a network, one important parameter is related with power gain and sensitivity.
Power level (dBm) at which the module transmits conducted power.
The possible values are Low ('L'), High ('H') and Max ('M'):
Parameter
SX1272 power level
'L'
0 dBm
'H'
7 dBm
'M'
14 dBm
Figure: Transmission power values
It is also possible to set the conducted power indicating the quantity as a parameter in the function setPower.
Note: dBm is a standard unit to measure power level taking as reference a 1 mW signal.
Values expressed in dBm can be easily converted to mW using the next formula:
Graphic about transmission power is exposed next:
Example of use:
Related variables:
sx1272._power → stores the selected power output level
Note: It is the responsibility of the users to know the maximum allowed power level in their country (if any), and use levels below it. Ignoring this could lead to considerable penalties.
It reports the Received Signal Strength of the last received packet and the current value of the Received Signal Strength in the selected channel. The RSSI of the packet is the meaningful one: if its value is greater than the sensitivity the packet sent is going to be successfully detected, otherwise the packet will be lost. The RSSI of the channel reports the signal level detected in every moment, even if it is not signal being transmitted, so it provides also noise level information. In the case the user develops a multi-hop network, this parameters only indicate the signal strength of the last hop, so it does not provide an accurate quality measurement of a multihop link.
Example of use:
Related variables:
sx1272._RSSIpacket → stores the RSSI of the last received packet
sx1272._RSSI → stores the current RSSI value
SX1272 RSSI example:
The ideal working mode is at getting maximum coverage with the minimum power level. Thereby, a compromise between power level and coverage appears. Each application scenario will need some tests to find the best combination of both parameters.
It reports the Signal-to-Noise Ratio of the last received packet. The LoRa module is capable to demodulate received signals with SNR values as low as -20 dB. Getting the SNR, it is possible to have an idea about the link\'s quality or health, and thus the additional distance we could get in a communication link.
Example of use:
Related variables:
sx1272._SNR → stores the SNR of the last received packet
SX1272 RSSI example:
