Although Sprint's 4G LTE network has already been available in some pockets of San Francisco for months, the carrier has yet to announce its official launching. Until then, CNET takes a look at one of the carrier's active cell sites in San Francisco, known as Site SF33XC664.
The site is located on the roof of the Medical Arts Building on Van Ness Avenue. When looking for an ideal location for a cell site, engineers involved in radio frequency design look at the surrounding typography, population, and traffic density of a given area.
Once a location is chosen, carriers must get clearance from municipality and zoning commissions. They then negotiate leasing terms with building landlords for every individual site. Currently, Sprint has 38,000 sites across the U.S.
At this location, Sprint has installed three antennas on the roof. The range of each antenna depends on its location. For a site like this, this antenna is estimated to cover about a quarter square mile.
Below that is the RF amplifier for the 800MHz band. By installing the radio heads directly below the antenna (instead of nearby underground or at the cell site's base station, both of which are common methods), the carrier minimizes the amount of lost signal.
Cords that run throughout the antenna and the radio heads are wrapped in bright tape, with different colors representing different network speeds and bands. It helps engineers to quickly identify fiber optics for 4G LTE and 3G CDMA technology.
Warning signs about radio frequency exposure are posted in various locations throughout the site.
The vice president of Sprint's network service management, Joe Meyer, stands in front of the site's base station where signal traffic between phones and the network are regulated.
Here, the top control panel handles LTE data, while the bottom two handles CDMA data and voice. The station does not support WiMAX technology.
Next to the base station is a backup power unit made up of 12 deep-cycle batteries. If a site loses commercial power, the batteries are designed to provide between 4 and 8 hours of emergency power.
Data from the base station is fed through this fiber back haul station, which will then send signals through AT&T's (the incumbent cable company in the City) fiber cables. The signals travel about 10 miles out to Brisbane, Calif., where calls and Internet receptions are routed to the appropriate locations.
At the very top of the base station is a white and red GPS antenna, which synchronizes information like the local time and location to your cell phone.
Sprint isn't the only carrier to install a cell site here. Though you can see another one of its antennas on the left, one of AT&T's white antennas stands a few feet to the right of it.
Two Samsung engineers (right) stand by at the cell site. A total of three OEMs -- Samsung, Ericsson, and Alcatel -- are providing the build-out for Sprint's expanding 4G LTE network.
Next to Sprint's new base station is one of the carrier's own previous, 15-year-old base station (left), which is equipped with radio heads inside. To the right of it are two backup battery sources. The station only provides 1X, 3G, and voice technology, and will soon be decommissioned.
Behind Sprint's equipment is MetroPCS' own base station.
A MetroPCS sticker labels the carrier's equipment.
Not far from both carriers' stations is AT&T's equipment as well.
The door leading to the cell site is riddled with more warning signs from different carriers cautioning against high amounts of radio frequency exposure.