What is RSSI? And how to use it?

Received Signal Strength Indicator. It indicates the RF signal strength at the receiver antenna input. Being a value of power, RSSI values are quoted in dBm. To indicate this on the module, the RSSI pin outputs a DC voltage value that varies with received RF strength. There are conversion charts in the manuals to read off the RSSI value from this voltage. Monitor the RSSI value while conducting tests, in the case of MU-4-434 with RS232C or USB test board, the RSSI can be monitored using the Air Monitor function.