A fixed station in a cellular wireless network, used for communicating with mobile terminals (phones). A base station is what links mobile phones to a wireless carrier's network.
A base station provides local coverage (an area where mobile phones will work) for a wireless network. The area of coverage may be many miles or just a few city blocks. The coverage can be in all directions, or the antennas may be aimed only in one direction.
Each base station is typically owned by one wireless company (carrier) and only provides coverage for that company's network, although it may also provide roaming coverage for other networks, if the technology is compatible and the carriers have a roaming agreement. However, a single location (building or pole) often hosts multiple base stations, each owned by a different carrier. Each base station at that location has its own antennas and electronic equipment.
A base station consists of an electronic equipment cabinet connected by large cables to a group of antennas. The equipment is sometimes large enough to require its own small building. The antennas may be mounted on a dedicated tower structure, or on an existing structure, such as the top of a building, water tower, smoke-stack, or church steeple.
Smaller types of base stations include microcells, picocells, and femtocells.