out of band rejection gsm

there is a aritcal said , GSM receiver designers specify the receive strips' compression points based on in-band blocking signal level specifications, and uses the out-of-band blocking signal levels to define the filter rejection specifications to avoid signal path compression.

Q1 : Why to specify the reciever strips' compression points based on in-band blocking signal lever?

Q2 : Why are the signals below 3Mhz called in-band signal in GSM spec.?

Q3 : the compression point above is just the P1db compression point?

Answer for Q1: When a large blocker make the receiver compression, Small desired signal gain will decrease. So the sensitivity is worse.