Signal to Interference Ratio

The SIR indicates the ratio between the received signal level and the level of interference. This parameter is used in WCDMA systems to control transmission power of user equipment (UE). If the measured SIR is higher/smaller than the target SIR, the base station will command UE to increase/lower power.

SIR calculation


SIR mapping table

Code Range of SIR in dB Code Range of SIR in dB Code Range of SIR in dB
0 <-11.00 22 -0.50 to 0.00 44 10.50 to 11.00
1 -11.0 to -10.5 23 0.00 to 0.50 45 11.00 to 11.50
2 -10.5 to -10.0 24 0.50 to 1.00 46 11.50 to 12.00
3 -10.0 to -9.50 25 1.00 to 1.50 47 12.00 to 12.50
4 -9.50 to -9.00 26 1.50 to 2.00 48 12.50 to 13.00
5 -9.00 to -8.50 27 2.00 to 2.50 49 13.00 to 13.50
6 -8.50 to -8.00 28 2.50 to 3.00 50 13.50 to 14.00
7 -8.00 to -7.50 29 3.00 to 3.50 51 14.00 to 14.50
8 -7.50 to -7.00 30 3.50 to 4.00 52 14.50 to 15.00
9 -7.00 to -6.50 31 4.00 to 4.50 53 15.00 to 15.50
10 -6.50 to -6.00 32 4.50 to 5.00 54 15.50 to 16.00
11 -6.00 to -5.50 33 5.00 to 5.50 55 16.00 to 16.50
12 -5.50 to -5.00 34 5.50 to 6.00 56 16.50 to 17.00
13 -5.00 to -4.50 35 6.00 to 6.50 57 17.00 to 17.50
14 -4.50 to -4.00 36 6.50 to 7.00 58 17.50 to 18.00
15 -4.00 to -3.50 37 7.00 to 7.50 59 18.00 to 18.50
16 -3.50 to -3.00 38 7.50 to 8.00 60 18.50 to 19.00
17 -3.00 to -2.50 39 8.00 to 8.50 61 19.00 to 19.50
18 -2.50 to -2.00 40 8.50 to 9.00 62 19.50 to 20.00
19 -2.00 to -1.50 41 9.00 to 9.50 63 >20.00
20 -1.50 to -1.00 42 9.50 to 10.0
21 -1.00 to -0.50 43 10.0 to 10.50

Source: ETSI

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