A9.1.3 Derivation from a protection ratio

This is the case for GSM, with regards to the 2 first adjacent channels.

In 3GPP TS 45 005  [21], Table 6.3-1 in section 6.3, protection ratios are specified in dB for a desensitisation D_STANDARD of 20 dB (see section 6.1).

• Co-channel, [C/Ic]_dB = C - Ic = 9 dB
• First adjacent channel, [C/Ia1]_dB = C - Ia1 = -9 dB
• Second adjacent channel, [C/Ia2]_dB= C - Ia2 = -41 dB

These are the “blocking protection ratios”.

The Blocking Response is given by the following equation:

Blocking Response    = I_IB-STANDARD - I_OOB-STANDARD    (Eq. 135)

= (C - I_OOB-STANDARD) - (C - I_IB-STANDARD)  (Eq. 136)

                               = (C - Ia) - (C - Ic)

I_OOB-TARGET can then be derived from the following equation:

I_OOB-TARGET = N + 10.log₁₀[10^(D_TARGET/10) - 1] + (C - Ic) - (C - Ia)   (Eq. 137)

I_OOB-TARGET = N + I/N_TARGET + (C - Ic) - (C - Ia)   (Eq. 138)