CDMA and GSM Networks

CDMA and GSM are two different technology(rather network) altogether. Very
fundamentally different.Normally GSM networks operate in 900 MHz or 1800 MHz
using frequency division multiplexing. Another important feature of GSM is
Subscriber Identity Module or SIM Card. It is a small smartcard which contains
subscriber information and phonebook. Basically SIM card is the part of the
network. For higher speed data transmission either GPRS or EDGE can be used in
GSM phones.
CDMA is a form of multiplexing which divide signals by random pseudo codes
instead of conventional multiplexing methods like dividing by time or frequency.
CDMA is widely used in cellular networks and global positioning systems
(GPS).CDMA, a proprietary standard designed by Qualcomm in the United States.
CDMA is traditionally faster than GSM, providing better use in data transfer.
But usage of GPRS and EDGE on GSM network filled the gap. These two technologies
are basically used for data transfer in GSM network.
Both the technologies are moving ahead towards 3G standard or technology.
CDMA cell phones and CDMA carriers do not support SIM cards in most parts of the
world, though this is changing. A CDMA SIM card called the R-UIM (Re-Useable
Identification Module) was made available in China in 2002, and will eventually
be available worldwide. Expectations for the future include a cell phone market
that supports both SIM (GSM) and R-UIM (CDMA) cards by default.http://www.wisegeek.com/what-is-a-sim-card.htm
There are phones which are made for CDMA or GSM networks or both with two slots
of SIM. But if the phone is built for CDMA, it will only support CDMA SIM or R-
UIM. Similarly, if the phone is built for only GSM, it will support all GSM SIM
cards. This means that not only SIM or R-UIM plays the role in the network, but
also the phone circuitary. Now the phone having both the circuitary are available
in the market.http://www.techlivez.com/2007/08/wanna-have-gsm-and-cdma-both-in-a-single-
handset/
Also, one of the largest adv of GSM phones are having the capacity of world
roaming. CDMA have very poor in world roaming.
If your SIM card enabled phone(GSM) is quad band (850/900/1800/1900 MHz)this
means, if you travel to other countries you can even use your GSM cell phone
abroad, providing it is a quad-band phone (850/900/1800/1900 MHz).These are 4
bands which are used in GSM network all over the world.For other difference
between CDMA and GSM, please click on below link.http://www.wisegeek.com/what-is-the-difference-between-gsm-and-cdma.htm
Mobile Service Provider in india:CDMA service provider are Reliance and Tata Indicom. All others are GSM. Reliance
have both type of network in India. In Bihar, Assam and other eastern and central
India, Reliance have GSM network. In remaining parts of India, Reliance has CDMA
nework.http://www.tamilnow.com/articles/india-cellular-network.htm
Last piece of information, in india, CDMA service providers are lobbying number
protability while GSM service providers are against it.