Cell sites are locations where antennas and electronic communications equipment are located to create a cell in a mobile phone network (cellular network). Cell sites are normally erected on property that is not owned by either tower companies or wireless carriers. Tower companies and carriers gain access to property through a lease or license with a property owner. Property owners have discovered profitable returns in building and leasing cellular towers on their properties.
Many cell site antennas are mounted on buildings rather than on towers. Some towers are hidden inside artificial trees, preserved trees, or structures that look like sculptures; they are referred to as concealed sites or stealth sites. Many cell sites are on roof tops, and many of these are stealth in form. Sometimes antennas are located in church steeples and mock chimneys.
A site hosting just a single phone company may house several base stations, each to serve a different air interface technology. A site is composed of a tower or other elevated structure for mounting antennas and one or more sets of transmitter/receivers transceivers, digital signal processors, control electronics, a GPS receiver for timing, regular and backup electrical power sources, and shelter. Cell towers always set aside part of their available bandwidth for emergency calls.
Cell sites are grouped in areas of high population concentration, with the most possible users. Cell phone transfer through a single tower is limited by the tower’s capacity; there is a fixed number of calls that can be handled at once. This constraint is another aspect affecting the spacing of tower sites. In low density areas towers are usually spaced 1-2 miles apart; within dense metropolitan areas they may be only 1/4 to 1/2 mile apart. Each tower overlaps other cell sites.
When phones are moving from place to place, they also have to change from site to site. Cell tower sites are linked to phone exchange switches, which connect to the telephone network or another switch of the cellular company. There is multiple independent access in each tower, so an early stage of handoff is to reserve a new channel for the phone on the new base station which will serve it. As a phone user repositions from one vicinity to another, the switch routinely commands the phone and a site with a stronger signal to go to the new frequency; it then moves from the channel on its current base station to the new channel. When the phone responds through the new site, from that point on communication takes place from the new tower.
For property owners, sites can add considerable value to their property, and in some cases the site is worth more than the property itself. In recent years, a large number of companies have formed with the singular purpose of acquiring these leases from property owners. These buyout companies offer lump sum payments to property owners for both rooftop and tower sites. This can be a viable option for site owners that want to cash out their leases.