GSM v. CDMA
Monday, December 7, 2009 The two most popular network technologies for mobile devices are GSM (Global System for Mobile Communications) and CDMA (Code Division Multiple Access). GSM operates on the 900 & 1800 MHz bands (850 & 1900 MHz in North America). The major GSM carriers in the U.S. are AT&T and T-Mobile. CDMA is on 800 & 1900 MHz, and is used by Verizon and Sprint.
Advantages of GSM
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GSM phones use SIM (Subscriber Identity Module) cards to identify the customer on the network. GSM subscribers can swap phones by removing the SIM card from one phone and placing it into another phone - no carrier intervention is required. On GSM networks, the service and the phone number are tied to the SIM card, not the handset. An unlocked GSM phone can be used with any GSM carrier’s SIM card.
CDMA networks identify the subscriber based on a serial number stored directly on the handset. CDMA phones are proprietary to the issuing carrier, and for all practical purposes, can’t be unlocked. A CDMA upgrade entails having the carrier deactivate the old phone and activate the new one.
- Because GSM has about 80% of the global market share, GSM phones can be used throughout the world, and roaming charges may be avoided by using a local SIM card to make local calls.
Advantages of CDMA
- CDMA offers better voice quality and fewer dropped calls than GSM.
- CDMA is the basis for 3G data communications, even on GSM networks.
- CDMA can be implemented using fewer cell towers, and can handle more concurrent calls over a fixed frequency range than GSM, so it’s more efficient.
- Because CDMA uses spread-spectrum technology calls are harder to intercept, making CDMA more secure.
- GSM phones may cause speakers in nearby electronic equipment to buzz intermittently; CDMA phones don’t create this issue.