The cellular signal strength bars of Accelerated LTE routers are calculated using various algorithms based on the network type it is connected to. For 4G LTE, the RSRP, SNR, and RSSI values are all factored in to determine the reported signal strength bars. For 3G networks (including HSPA+) and 2G networks, the signal strength bars are determined by the RSSI value.

Determine RSRP, SNR, and RSSI values separately, using the following

RSRP > -85, rsrp_bars=5
-95 < RSRP <= -85, rsrp_bars=4
-105 < RSRP <= -95, rsrp_bars=3
-115 < RSRP <= -105, rsrp_bars=2
-199 < RSRP <= -115, if we're connected to the cellular network, rsrp_bars=1, if not rsrp_bars=0

If RSRP <= -199, then use RSSI as the value and run it through the same algorithm described above.

SNR >= 13, snr_bars=5 
4.5 <= SNR < 13, snr_bars=4 
1 <= SNR < 4, snr_bars=3 
-3 < SNR < 1, snr_bars=2 
-99 < SNR <= -3, if we're connected to the cellular network, snr_bars=1, if not snr_bars=0

Once the snr_bars and rsrp_bars are determined, use the lesser of the two. That is the reported signal strength bars.

Determine RSSI signal strength.

RSSI > -80, bars=5 
-90 < RSSI <= -80, bars=4 
-100 < RSSI <= -90, bars=3 
-106 < RSSI <= -100, bars=2 
RSSI <= -106, if we're connected to the cellular network, bars=1, if not bars=0

bars is then reported as the signal strength bars.

Determine RSSI signal strength.

RSSI > -80, bars=5 
-89 < RSSI <= -80, bars=4 
-98 < RSSI <= -89, bars=3 
-104 < RSSI <= -98, bars=2 
RSSI <= -104, if we're connected to the cellular network, bars=1, if not bars=0

bars is then reported as the signal strength bars.