Introduction
to Mobile Phone.
Cellular
telephone systems are a way of providing portable telephone services. Each
phone is connected by a radio link to a base station. In turn, this is linked
to the telephone network, which is the largest machine on the planet.
There is nothing
special about radio links - they've been used for scores of years. What is clever is that with a cellular system,
each base station covers a limited area, and if a phone moves away, the
connection is passed across to an adjacent base. This is called a hand-off, and
allows mobility of phones, whilst permitting re-use of frequencies by base
stations in nearby, but not adjacent, 'cells'.
In addition to telephony, modern mobile phones also support a wide variety of other services such as text messaging, MMS, email, Internet access, short-range wireless communications (infrared, Bluetooth), business applications, gaming, and photography. Mobile phones that offer these and more general computing capabilities are referred to as smartphones.
In
the year of 1973, a former general manager from the systems division of
Motorola, Dr. Martin Cooper, became who is thought
to be the inventor of the first portable handset. Dr. Cooper was also the first person to
make a call using a portable cell phone.
COMMUNICATION
SYSTEMS:
Simplex: Simplex communication refers to
communication that occurs in one direction only.
Examples:
- Commercial radio broadcast (not walkie-talkies, etc.)
- Television broadcast
- Internet multicast.
A half-duplex system provides for communication in both directions, but only one direction at a time (not simultaneously). Typically, once a party begins receiving a signal, it must wait for the transmitter to stop transmitting, before replying.
Examples:
Walkie-talkie
(since, it is two-way radio, wherein one must use "Over" or another
previously-designated command to indicate the end of transmission, and ensure
that only one party transmits at a time, because both parties transmit on the
same frequency.)
Full-duplex :
A full-duplex,
or sometimes Double-duplex system, allows Communication in both directions, and, unlike half-duplex, allows this to happen
simultaneously. Land-line telephone networks are full-duplex, since they allow
both callers to speak and be heard at the same time. A good analogy for a
full-duplex system would be a two-lane road with one lane for each direction.
Examples:
- Telephone,
- Mobile Phone, etc
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