Mobile phone base station antennas in MRT station

While in the MRT station today, I managed to glance up at the ceiling and saw these antennas in the ceiling. I noticed that they were internal base station antennas for telcos. The M1 sticker on one of them kind of gave that away. I am referring to the circular antennas, not the stick-like ones. I have absolutely no idea what those are for. They are probably for walk-talkie communication between station staff. Interesting to see antennas like these. They look different from other base station antennas installed in other places.