The GSM standard is a specification of an entire network infrastructure, while CDMA is a form of multiplexing and access interface that relates only to the RF interface. Check out the Wikipedia links for a more indepth look.
If you are not familiar with radio transmission concepts, by reading Wikipedia staff or going too soon into details is very easy to get lost.
The big difference between GSM and CDMA is spectrum management. GSM (and older NMT) is using a bunch of frequencies while CDMA is using just one radio frequency for covering a whole country. Because radio spectrum is a crossing-boarder very limited natural resource, ITU (International Telecommunications Union) has allocated a limited spectrum for each service (land-mobile, marine, aviation, satellite communications, broadcasting, etc.) and each country took a small slice of each service sub-spectrum. If in a country there are several mobile operators (usually 2-3), each of them have to pay to the government a fee (millions of dollars per annum) for spectrum utilization and are assigned (licensed) specific frequencies for not interfering to each other.
From this perspective, GSM looks bad compared to CDMA. However, it is much more spread in the world. Historically, GSM was created in Europe and CDMA in the USA. Their competition reflected the eternal commercial war. Lately, they began to compromise on mixed markets.
In order to improve the spectrum management, GSM is reusing each allocated frequency in different non-neighboring cells. The term "cellular telephony" is coming from a small territory (cell) in which a hand-held device can receive a usable signal from the surrounding base-stations (repeaters).
Both are evolving standards (so-called generations). They are very similar in applications but very very different in transmission technology.
You could write books on the differences. In fact, many people have.
The previous comments and the wikipedia links are very good and can help you understand the two technologies. GSM = Global System for Mobile Communications. CDMA = Code Division Multiple Access.
As pointed out before there are several differences and several similarities. Both are digital technologies. Both require registration and authentication with the network. The differences lie in how the devices authenticate, but suffice it to say that they are both secure.
Both are spread spectrum technologies. That is, they use larger chunks of radio spectrum than normal narrow band communications. Most RF transmissions occur in 20-30 KHz bands. GSM uses 2.5 MHz for both up-link and down link (5 MHz per carrier) where CDMA uses 1.25 MHz for each link or 2.5 MHz per carrier. The biggest difference lies in how they use the RF spectrum. GSM is a TDM technology -- users are assigned a specific time slot for transmission and reception. CDMA, as the name implies, uses a code to identify transmissions. Different codes are used for the up-link and down-link.
One crucial difference for operators was pointed out in an earlier posting. Neighboring cell towers in GSM must talk on different frequencies. Neighboring towers in CDMA usually talk on the same frequency. This enables a "soft" hand over when the mobile moves from one cell to another. In most cellular networks, the mobile has to change the radio frequency ("hard" hand over) which increases the likelihood of a call drop. In CDMA, the mobile simply stops communicating with one tower and begins communicating with another. So, there are elements of CDMA that extend beyond the air interface.
One interesting point is that all of the GSM carriers worldwide are moving to UMTS, the Universal Mobile Telecommunications System. Another name for UMTS is W-CDMA, or Wideband CDMA.
CDMA(Code Division Multiple Access) is a digital cellular technology that uses spread-spectrum techniques.CDMA consistently provides better capacity for voice and data communications than other commercial mobile technologies, allowing more subscribers to connect at any given time, and it is the common platform on which 3G technologies are built.It doesn't have sim card.
The reason for more GSM usage is that the international Roaming of GSM is Very good and it has sim card,So you can easily swap your sim card when you need. If we got a locked phone means we can unlock it; see the instructions here.
GSM And CDMA
Re: GSM And CDMA
