One mobile operator I was using did a special package with free calls between all employees - with the little oops that one of the offices (where I was located) did not have any coverage.

They installed a slave cell in the corridor outside my room. One of the antenna outputs was configured for low power output and connected to a small dish antenna in the roof. The other antenna output was configured for high-power mode and connected to an antenna on the roof of the house.

A guy in a room on the other side of the corridor got problems with his CRT monitor. The image jumped up and down similar to what happens if you put our mobile phone under a CRT and wait until someone calls. The image was jumping until he put a screen of aluminum foil between the indoor antenna and his room. The technician who configured had mixed up the two antenna outputs, so the outdoor antenna got 50mW and the indoor antenna was allowed to run at full power - and since it was indoors with a lousy antenna, it had to run at high power to communicate with all outdoor mobile phones...

But in the end, the distance to the cell mast isn't the most important factor (unless you are very, very close). The send direction is more important. Most energy is sent in a horisontal lobe, so if you are close and below the mast, you will miss most of the lobe. The next thing is that most newer installations can dynamically adjust the power in different directions. Two cells close together can be configured to broadcast very little energy towards each other.