Mobile Phones
When venturing into the realm of mobile phones, be
it literature on phones, looking at sites on the web,
or most daunting discussing phones with the mobile
phone sales representative at the phone shop, you’ll
be bombarded with plenty of confusing terms and jargon.
So here at Mobiles we thought it might be a good idea
to fill you in with the explanations of some of the
commonly used terms along with a little history to
put the terms into context.
In 1988, the Cellular Technology Industry Association
(CTIA) was established to work with the mobile phone
service operators and researchers to identify new
technology requirements and set goals. They wanted
the new products and services introduced by 1991,
a 1000% percent increase in system capacity with both
AMPS (analogue) and digital capability during transmission,
and new data features such as fax and messaging services.
The Telecommunications Industry Association (TIA)
created a standard specification based on the requirements
the CTIA had recommended. The TDMA Interim Standard
54 or TDMA IS-54 was released in early 1991. The technology
was tested that same year in Dallas America and Sweden.
In 1994, the FCC announced it was allocating spectrum
specifically for PCS technologies at the 1900 MHz
band. Three major standards have been released since
1991. All of these new digital wireless standards
are currently being used in Personal Communication
Services.
Mobile phone Standards
Analogue Service: A method of modulating radio signals
so that they can carry information such as voice or
data. Analogue mobile phones work like a FM radio.
The receiver and transmitter are tuned to the same
frequency, and the voice transmitted is varied within
a small band to create a pattern that the receiver
reconstructs, amplifies and sends to a speaker. The
drawback of analogue is the limitation on the number
of channels that can be used.
Digital Service: A method of encoding information
using a binary code of 0s and 1s. Most newer wireless
phones and networks use digital technology. In digital,
the analogue voice signal is converted into binary
code and transmitted as a series of on and off transmissions.
One of digital's drawbacks is that there are three
digital wireless technologies, CDMA, TDMA and GSM.
Phones that work with one technology may not work
on another.
TDMA IS-136 (Time Division Multiple Access) is an
update to TDMA IS-54, also called Digital AMPS or
D-AMPS. Released in 1994, TDMA IS-136 uses the frequency
bands available to the wireless network and divides
them into time slots with each phone user having access
to one time slot at regular intervals.
GSM (Global System for Mobile Communications) is
based on an improved version of TDMA technology. In
1982, the Conference of European Posts and Telecommunications
(CEPT) began the process of creating a digital cellular
standard that would allow users to roam from country
to country in Europe. By 1987, the GSM standard was
created based on a hybrid of FDMA (analogue) and TDMA
(digital) technologies. GSM engineers decided to use
wider 200 kHz channels instead of the 30 kHz channels
that TDMA used, and instead of having only 3 slots
like TDMA, GSM channels had 8 slots. This allowed
for fast bit rates and more natural-sounding voice-compression
algorithms. GSM is currently the only one of the three
technologies that provide data services such as email,
fax, internet browsing, and intranet/LAN wireless
access, and it's also the only service that permits
users to place a call from either North America or
Europe. The GSM standard was accepted in the United
States in 1995. GSM-1900 cellular systems have been
operating in the US since 1996, with the first network
being in the Washington, D.C. area. Major carriers
of GSM 1900 include Omnipoint, Pacific Bell, BellSouth,
Sprint Spectrum, Microcell, Western Wireless, Powertel
and Aerial.
|
