Another part of phone power is size/sexiness. Small phones = small batteries = less power. In general, this works well. You simply add more towers so, on average, you are closer to a tower.

In order to make cell phones cheaper, the receivers are generally half-deaf. Cell towers throw out around 100 times the power of the cell phones themselves. So, while this works well for normal phone calls, it hurts cell-to-cell calls.