Cellular Gateway Signal Level Values

The signal indicator used in iMonnit for cellular gateway uses the ASU (Arbitrary Signal Unit) signal indicator. This is converted into the “bars” icon that represents the signal strength. For reference, view the Wikipedia page for Mobile Phone Signal.

Graphical Representation

In the iMonnit Online Portal, the following scale is used for graphical representation of the ASU signal indicator to a 5 bar signal graphic where 0 bars equals low/no signal and 5 equals the best signal.

5 bars: 24 - 31

4 bars: 20 - 23

3 bars: 15 - 19

2 bars: 11 - 14

1 bar: 6 - 10

0 bars: 0 - 5

Technical conversion referencing RSSI

In GSM networks, ASU maps to RSSI (received signal strength indicator, see TS 27.007[3] sub clause 8.5).

dBm = 2 × ASU - 113, ASU in the range of 0.31 and 99 (for not known or not detectable).

In UMTS networks, ASU maps to RSCP level (received signal code power, see TS 27.007[3] sub clause 8.69 and TS 25.133 sub clause 9.1.1.3).

dBm = ASU - 115, ASU in the range of 0.90 and 255 (for not known or not detectable).

In LTE networks, ASU maps to RSRP (reference signal received power, see TS 36.133, sub-clause 9.1.4). The valid range of ASU is from 0 to 97. For the range 1 to 96, ASU maps to

(ASU - 143) < dBm = (ASU - 140).