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In 3G, the most prevalent technology was UMTS with CDMA-2000 in close contention. All radio access technologies have to solve the same problems: to divide the finite RF spectrum among multiple users as efficiently as possible. GSM uses TDMA and FDMA for user and cell separation. UMTS, IS-95 and CDMA-2000 use CDMA. WiMAX and LTE use OFDM.
The iPhone 5 is shipped with iOS 6, which was released on September 19, 2012. [34] Many of the iPhone 5 's features that work specifically with the included iOS 6.0 operating system only worked in certain territories on release. [36] Apple has said this is a rolling program, which will take longer to implement across more regions. [37]
As a more recent example the Apple iPhone 5 and iPhone 4S support quad-band GSM at 850/900/1800/1900 MHz, quad-band UMTS/HSDPA/HSUPA at 850/900/1900/2100 MHz, and dual-band CDMA EV-DO Rev. An at 800/1900 MHz, for a total of 'six' different frequencies (though at most four in a single mode).
In Russia and some other countries, local carriers received licenses for 450 MHz frequency to provide CDMA mobile coverage area. Many GSM phones support three bands (900/1,800/1,900 MHz or 850/1,800/1,900 MHz) or four bands (850/900/1,800/1,900 MHz), and are usually referred to as tri-band and quad-band phones, or world phones; with such a ...
CDMA (IS-95) uses the Enhanced Variable Rate Codec, which runs from about 8kb/s to as low as 800bytes/s. GSM (2G) appears to use a number of codecs, (see GSM) which range from 13kb/s to 1.8kb/s. Although it looks like CDMA is the clear winner, it is important to note that EVRC is not intended to transmit understandable speech at that rate.
CDMA is analogous to the last example where people speaking the same language can understand each other, but other languages are perceived as noise and rejected. Similarly, in radio CDMA, each group of users is given a shared code. Many codes occupy the same channel, but only users associated with a particular code can communicate.