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Cellular
Communications |
5. Cellular System
Components
The cellular system offers mobile and portable telephone stations
the same service provided fixed stations over conventional wired
loops. It has the capacity to serve tens of thousands of subscribers
in a major metropolitan area. The cellular communications system
consists of the following four major components that work together
to provide mobile service to subscribers.
- public switched telephone network (PSTN)
- mobile telephone switching office (MTSO)
- cell site with antenna system
- mobile subscriber unit (MSU)
PSTN
The PSTN is made up of local networks, the exchange area
networks, and the long-haul network that interconnect telephones and
other communication devices on a worldwide basis.
Mobile Telephone Switching Office (MTSO)
The MTSO is the central office for mobile switching. It houses
the mobile switching center (MSC), field monitoring, and relay
stations for switching calls from cell sites to wireline central
offices (PSTN). In analog cellular networks, the MSC controls the
system operation. The MSC controls calls, tracks billing
information, and locates cellular subscribers.
The Cell Site
The term cell site is used to refer to the physical
location of radio equipment that provides coverage within a cell. A
list of hardware located at a cell site includes power sources,
interface equipment, radio frequency transmitters and receivers, and
antenna systems.
Mobile Subscriber Units (MSUs)
The mobile subscriber unit consists of a control unit and a
transceiver that transmits and receives radio transmissions to and
from a cell site. The following three types of MSUs are available:
- the mobile telephone (typical transmit power is 4.0 watts)
- the portable (typical transmit power is 0.6 watts)
- the transportable (typical transmit power is 1.6 watts)
The mobile telephone is installed in the trunk of a car, and the
handset is installed in a convenient location to the driver.
Portable and transportable telephones are hand-held and can be used
anywhere. The use of portable and transportable telephones is
limited to the charge life of the internal battery.
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