GSM vs. CDMA - Two Competing Cell Phone Technologies

There are two main types of cell phones used in the US. These are GSM (Global System for Mobile Communications) and CDMA/iDEN. GSM phones utilize SIM cards (Subscriber Identity Module) while CDMA/iDEN do not. As of this writing only T-Mobile and Cingular utilize GSM in the US, Sprint and Verizon use CDMA/iDEN.

GSM was developed in Europe and allows for easy international roaming. The key feature of GSM, the SIM card allows the subscriber information to be stored on a small, removable card, rather than on the phone. This means that personal information such as contacts, and key technical information for connecting to your service, are stored on a card that can be moved from phone to phone. Changing services is as easy as swapping the card, and changing phones is as easy as popping out your card and moving it to a new phone. This allows for easy portability of service. Even when a phone’s SIM card is locked by a service, it is usually quite easy to unlock the card and/or phone.

Integrated Digital Enhanced Network (iDEN) was originally developed from GSM by Motorola for use by Nextel (now Sprint). Although this technology allows for SIM cards, today providers often hard wire the SIM information into the phone, defeating the ease of portability. Nextel’s acquisition by Sprint likely means the demise of iDEN in the US.

Code Division Multiple Access (CDMA) is the other large technology for cell phones. While CDMA has a larger coverage footprint in the US, it’s global coverage is much smaller than GSM. CDMA phones do not utilize SIM cards and therefore the subscriber personal information is not easily portable or accessible.

With the introduction of Apple’s new iPhone (which is a GSM phone) perhaps we’ll see a rise in GSM adoption in the US. If the iPhone reaches market share anywhere close to that of the iPod then I could easily see GSM becoming a standard in the US, which would be nice since we’ve seen how well forging a nonstandard path has worked for Americans with unit measures (lost space probe anyone?).