CDMA vs. GSM Cell Phones
Author: K. Lynn

If you are in the market for a new cellular carrier and mobile
phone it is important that you are an informed consumer and know
the differences between the two primary cellular technologies
available, CDMA and GSM technologies.

What Is CDMA

CDMA is an acronym for Code Division Multiple Access; it is a
digital technology that uses what is known as "spread spectrum
techniques." This means that the transmitted signal frequency
varies deliberately. Allowing the signal to vary gives an output
of more bandwidth than would be allowed if the frequency was not
varied. CDMA has long been the standard used in the USA and has
been known for its ability to provide better voice and data
services than other cellular technologies on the market. Verizon
and Sprint use CDMA technology.

What Is GSM

GSM is the acronym for Global System for Mobile communications;
it is a digital technology that assigns a fixed frequency every
user on their network. GSM is the current standard in most of
Europe, Asia, and has made rapid strides in gaining market share
in the USA. GSM mobile phones use SIM card technology. AT&T and
T-Mobile use GSM technology.

SIM and R-UIM

A SIM card is a small removable smart card that allows users to
easily switch between handsets while retaining their personal
contact information and address books. The SIM card is tied to
the carrier's network and can be moved without intervention from
the carrier. Activating a new phone on a GSM network is as easy
as putting an activate SIM card into it. GSM phones with a
removed SIM card can later be used again as soon as a SIM card
is placed into it.

CDMA phones are not card-enabled; this means that the cell
phone used on the CDMA networks can only be used on those
networks. The phone itself is tied to the carrier's network; you
cannot switch to a new CDMA phone without first talking to your
carrier and having them deactivate your old phone and then
activating your new phone on their network. Once the old phone
has been deactivated it then becomes useless.

The CDMA equivalent to a SIM card is called an R-UIM card;
Removable User Identity Module. The R-UIM card is not yet
available in the US market, currently only being available in
parts of Europe and Asia.

Travel

You will find that both GSM and CDMA networks have good
coverage in major metropolitan areas. When you find yourself
roaming outside of your usual area you may find yourself without
adequate coverage if you are on a CDMA network, especially if
you enter into a more rural area. GSM carriers have contracts
with other GSM carriers that will allow them to have better
roaming coverage, even in rural areas. If you are going to
travel internationally with a GSM carrier you will most likely
have no problem getting a signal from an international carrier.
Most carriers in international markets are GSM networks. You
will need to check with your chosen carrier about the domestic
and international roaming plans they can offer you.

TDMA

TDMA, or Time Division Multiple Access, is mostly in use in the
Americas (North and South) and some parts of Asia. TDMA is not
popular in widespread usage because of its lack of flexibility
as it compares to the other two digital cellular technologies.
Current cellular providers that are still using TDMA technology
are predicted to switch over to the more popular and more
flexible GSM technology.


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