# Frequency Division Multiple Access (FDMA)
FDMA is the first-generation analog mobile access method that uses separate frequencies for each call.
For example if there are four stations, each will receive their own frequency.
So there is no interference between them.
This reduces interference but limits the number of users.
# Time Division Multiple Access (TDMA)
TDMA allocates unique Time Slots to each user within each channel.
Therefore it allows many users to access the radio frequency without anyone's interference.
Each mobile conversation uses only a particular frequency slot of the time.
# Code Division Multiple Access (CDMA)
In CDMA system, your encoded voice is digitized and divided into packets. These packets are tagged with "codes." The packets then mix with all of the other packets of traffic in the local CDMA network as they are routed towards their destination. The receiving system only accepts the packets with the codes destined for it.
CDMA quickly became one of the world's fastest-growing wireless technologies.
3G CDMA networks provide more capacity for voice traffic, along with high-speed data capabilities, hence many cellular service providers are now building or upgrading to it.
CDMA is used in both 2G and 3G wireless technologies.
# Global System for Mobile Communications (GSM)
GSM is now the worldwide standard technology for mobile communications. The advantage of GSM is that it provides a
High level of security,
Globally accepted technology standards and
Superior sound quality.
For any GSM phone to work, it requires a Subscriber Identity Module (SIM), a card that contains your telephone account information.
So an Indian GSM phone can be used in USA and other countries too.
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