Question: What conditions must be met for a UE to consider an MBS service as part of the MBS services of interest?
Option 1: The UE is receiving or interested in receiving this service via a unicast MRB, and one or more MBS FSAIs in the USD for this service are included in SIB21 acquired from the PCell.
Option 2: The session of this service is ongoing or about to start, but no frequency mapping is provided in SIB21 for the concerned service.
Option 3: The UE has previously received this service via a broadcast MRB, and the USD for this service includes one or more MBS FSAIs that are not included in SIB21 acquired from the PCell.
Option 4: The UE is receiving or interested in receiving this service via a broadcast MRB, the session of this service is ongoing or about to start, and one or more MBS FSAIs in the USD for this service are included in SIB21 acquired from the PCell for a frequency belonging to the set of MBS frequencies of interest.
Explanation: According to the 3GPP TS 38.331 specification, a UE considers an MBS service as part of the MBS services of interest if three conditions are met: (1) the UE is receiving or interested in receiving this service via a broadcast MRB, (2) the session of this service is ongoing or about to start, and (3) one or more MBS FSAIs in the USD for this service are included in SIB21 acquired from the PCell for a frequency belonging to the set of MBS frequencies of interest.