There are a lot of dependent factors when we talk about the coverage of a certain area.
First is the kind of 4G coverage that you are talking about... Wimax?, LTE? (2 km from base station is very far), HSDPA? (which is now being marketed by Globe as 4G also and 2 km from coverage is quite far).
Second would be the propagation of those sites or where they are concentrated... equal propagation? more on the north or south or east or west?
Third would be the power they are utilizing.
Fourth would be the load they are expected to handle at any one time.
Fifth is the topography of the area between the user and the base transmitter (clear or with obstructions?).
There are many other factors to consider and the best way to find out is through an actual test and making necessary adjustments which the user could do in order to maximize the signals being received and transmitted (like utilizing a high gain antenna, boosters (which are now illegal if not registered) and even microcells, picocells and even femtocells like Globe's AirBoost).