Cell phone carriers use one of two networks to transmit sound and data, GSM or CDMA. When you're looking for a cell phone and see these acronyms, don't just let your eyes skim over them. They actually mean something! Your cell phone coverage is going to be different based on the network you choose. Whether or not these differences will matter enough for you to choose one or the other is up to you.
First, CDMA - or Code-Division Multiple Access - is the dominant network in the USA, CAnada, and parts of Asia. Fourteen percent of the world uses CDMA. When transmitting sound and data, the CDMA network doesn't assign each user a specific frequency. Every channel uses the full available spectrum. This is the same technology that made it possible for the US to prevent Germany from breaking in on their transmissions during World War II. Instead of using just one frequency, the US broadcasted over several to make it difficult for the GErmans to pick up. Sound and data are encoded and then transmitted using a wide frequency range, which leaves more room on the spectrum for data transfer. This translates into more subscribers being able to use their phones simultaneously.
GSM - or the Global Sytem for Mobile Communication - is used by a huge percentage of the world. According to the GSMA (Global Syatem for Mobile Communication Association), GSM serves 2 billion subscribers in 212 countries. GSM uses TDMA - Time Division Multiple Access - which allows several users to share the same frequency by dividing signal into three different time slots. Data is converted to digital form and comressed so it takes up less transmission space. TDMA has three times as much capability as the older analog syatmes using the same amount of channels.
Is one network better than the other? The first consideration is location. If you plan to use your phone solely in the USA and CAnada, a CDMA network is sufficient. Unlocked GSM cell phones can be used almost anywhere if they are triband or quadband, so that's a better choice if travel is a priority.
GSM phones use sim cards, which hold all user information. On unlocked cell phones, these cards can be used interchangeably with other Sim-based phones. This allows users to change carriers or phones and not lose their information or phone numbers. CDMA phones have an equivalent, the R-UIM card, but it us only available in parts of Asia. US CDMA phones are locked to one carrier. To upgrade a CDMA phone, the old one has to be deactivated and the new one activated. This renders the old phone useless. Unlocked GSM cell phones, by contrast, can be used as long as a IM card is inserted.
Both CDMA and GSM are fast and keep current with new technology to improve speeds. GSM uses EDGE technology, which allows faster data transmission rates and better quality. CDMA uses EV-DO, which uses a second channel (1.25 MHz) solely for data transmission. EV-DO technology allows high-speed internet access from a cell phone or a wireless desktop or laptop. Both technologies support multimedia messages, video, camera and PDA functions, as well as high speed internet.
The average consumer may not notice any difference in service between GSM and CDMA network phones. Both have extensive coverage in cities and along highways. If, however, a user lives in a rural area, CDMA provides more service. This is because CDMA can provide users with analog services when digital cuts out. GSM doesn't support any analog technology. THE GSMA reports subscriber numbers reach about 2 billion. CDMA is estimated to have about 421 million subscribers worldwide, so the coverage is very extensive for both networks.
Another consideration is the service carriers available. In the USA, AT&T (Cingular) and T-Mobile provide GSM network phones. VErizon, Sprint, Alltell, and US Cellular use CDMA. If you have a strong preference of carrier, this may determine which network you choose to cubscribe to. If you want the choice associated with an unlocked cell phone, choose a carrier who uses the GSM network.
CDMA and GSM provide superior technology to their subscribers. The choice is yours. Do you need the phone for travelling abroad? Do you live in a rural area with spotty digital coverage? Do you want an unlocked cell phone? You can find a carrier who meets your needs
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