One of the biggest difficulties with purchasing phones for your prepaid carrier is compatibility.
Terms like GSM, CDMA, 4G, WCDMA will confuse your brain so much!
Well, take it easy and we will walk you through.
WCDMA - Wide Band Code Division Multiple Access (UMTS)
Before we talk about 4G or GSM. You must know WCDMA which stands for Wide Band Code Division Multiple Access. It is a third generation network developed by NTT Docomo and from 2G network CDMA. There are no cellular companies that are not based on WCDMA except Sprint (however they are slowly converting). WCDMA is a standard for 3G network. It was not a revolutionary upgrade to network, but by having the standard based on 2G GSM/EDGE. It was able for a simultaneous switch between GSM and EDGE. Also it was capable of compatibility with other UMTS family.
However, there are no phones that are not WCDMA compatible. All carriers except U.S. Cellular and Sprint are based on WCDMA with all GSM phones compatible with WCDMA technology.
CDMA – Code Division Multiple Access
CDMA is a channel access method used by various radio communication technologies. It shouldnot be confused with the mobile phone standars called cdmaOne, CDMA 2000 (3G Evolution of cdmaOne) and WCDMA (the 3G standard used by GSM carriers) which are often referred to as simply CDMA, and use CDMA as an underlying channel access method.
One of the concepts in data communication is the idea of allowing several transmitters to send information simultaneously over a single communication channel.This allows several users to share a band of frequencies. This concept is Multiple Access or MA of CDMA. This is also why Verizon has much better pentration than AT&T or T-Mobile.
However, there is a disadvantage of CDMA. Your phone will not use a subscriber identification module to access cell towers. It will use an electric serial number to access. Which is why Verizon or Sprint’s phones usually don’t have a sim card. However, with WCDMA being deployed. All phones for all carriers have a sim. Still, if the phone does not have a GSM (2G) antenna, the (W)CDMA phone will not be compatible with GSM carriers.
GSM - Global System for Mobile Communications
Our world divides into four different generations of cellular network.
1G – Analog Cellular Network
2G – GSM or CDMA
3G – WCDMA
4G – LTE, HSPA+ all based on WCDMA , Wi – Max
After the first generation network, carriers either chose GSM or CDMA standard for their 2G network. Both network are not compatible to each other. However, a WCDMA phone will be compatible with GSM network if it has a sim slot and has a GSM antenna.
GSM carrier frequencies are 900, 1800, 1900, and 2100 mHz. That is why iPhones are only capable with 2G network on T-Mobile’s network.
GSM/CDMA compatible phone – iPhone 4S
GSM phone compatible carriers – AT&T, T-Mobile, Solavei (based on WCDMA and GSM)
GSM phone possibly compatible carruers – Verizon or Sprint if it is an iPhone 4S
CDMA only carriers- U.S. Cellular and Sprint.