Time Division Multiple Access (TDMA)
Why use TDMA?
TDMA (Time Division Multiple Access), is used in the largest available networks in the world. It is a digital communication method allowing many users to access a single communication channel. TDMA is aimed at dealing with multiple access to the same communication medium. Each individual user is given a unique time slot within the defined communication channel. This methodology increases the efficiency of transmission by allowing multiple users simultaneous access to a time slot. A significant benefit is TDMA can be easily adapted to transmission of data as well as voice communication. And the reason for choosing TDMA for all these standards is that it enables some vital features for system operation in an advanced cellular or PCS environment.
TDMA offers the ability to carry date rates of 64 kbps to 120 MBPS, which enables options of communication such as fax, voiceband data, sms, as well as bandwidth intensive apps. TDMA allows the mobile device to have extended battery life, since the cellular device is only transmitting a portion of the time during sessions. In addition, TDMA is the most cost effective technology for upgrading an analog system to digital (http://www.iec.org/online/tutorials/tdma/topic04.html).
How it works
It’s necessary for TDMA to rely upon that fact that the audio signal has been digitized. These signals are divided into a number of milliseconds and distributed into time slots. TDMA is also the access technique used in the European digital cellular standard, GSM, and the Japanese digital standard, personal digital cellular (PDC). A single channel can carry all four conversations if each conversation is divided into relatively short fragments, is assigned a time slot, and is transmitted in synchronized timed. For instance, if there are four people: Jan, Tom, Bill, and Bob making calls, each would be assigned a time slot on a single channel. However, if Bob was no longer using his phone, his time slot would still be used, wasting bandwidth. (http://www.iec.org/online/tutorials/tdma/topic04.html).