APs in hallways is always a bad idea. Sometimes there's no other option and I get that. But, RF is a bit like water in that it will take the path of least resistance. A hallway basically becomes a tunnel for all the RF to pour into. What's left going into the rooms is typically not very good, low signal.
Another reason against hallway placement is that it exacerbates CCI, especially in 2.4GHz. And it plays havok with a systems auto-RF features because the APa can here each other every well. APs may power down to try and avoid interference and then signal levels in rooms go down.
By placing APs within rooms you use the building itself (walls, doors, furniture, etc) to your advantage by attenuating the signal and helping to reduce CCI. Another benefit of placing APs within room is your getting getting the signal where it's supposed to be - IN THE ROOMS.
Mid you just place APs in hallways again try to use the building - insets where doors are, or other architectural features, to TRY and put some separation between APs. You could also use external antennas that are more directional to place the RF where you want it. Another option are APs that use beam-forming. That can help with CCI and getting the RF where you want it
The take aways here are
- Try to get your RF as close to the clients as possible.
- Use the buildings structure to your advantage.
- Ue directional antennas where you can.