Difference between TDMA, CDMA, and FDMA

These are all methods of exchanging and transmitting data. Because of their unique traits and features, they are particularly useful in a variety of contexts. In this article, we will see the specific differences between FDMA, TDMA, and CDMA.

A conventional analogue modulation technique may restrict the amount of data that may be transmitted over any given channel when connecting users that share the same radio frequency (such methods include FM and AM). Each channel can only hold one chat at a time in this situation. Therefore, it requires two users, one for receiving and one for broadcasting.

The ever-expanding needs of today are incompatible with AM (Analog Modulation) because only a limited number of users could occupy a spectrum of it. With a range of modulation algorithms that enable the transmission of more information on a channel, digital radio resolves this problem. In the end, the digital radio devised several ways to support several conversations within a single physical RF channel.

It primarily employs three typical methods to do so:

FDMA
TDMA
CDMA

FDMA (Frequency Division Multiple Access)

FDMA is a specific kind of channelization protocol. This bandwidth is broken up into different frequency bands. Each station has a specific band assigned to it for data transmission, and that band is always set aside for that station, as seen below:

Different stations’ frequency bands are separated from one another by a narrow band of unutilized frequency; this unutilized frequency band is referred to as a guard band since it prevents station interference. It is like the data link layer access approach, in which each station's data link layer instructs its physical layer to create a band pass signal using the data provided to it. There is no physical multiplexer at the physical layer because the signal is generated in the designated band.

TDMA (Time Division Multiple Access)

The channelization protocol known as TDMA divides a channel’s bandwidth among several stations based on the passing of time. Each station has a time slot that they can only use to send data during, which is as follows:

Each station needs to be aware of the beginning and placement of its time slot. Synchronization between various stations is necessary for TDMA. It is a particular type of data link layer access mechanism. Data link layer instructs each station to use the designated time slot at that location.

CDMA (Code Division Multiple Access)

All stations can broadcast data simultaneously in CDMA. Each station may continuously send data across the whole frequency thanks to this. A distinct code sequence divides the simultaneous transmissions into different groups. Each user is given a different code sequence.

There are four stations labelled as 1, 2, 3, and 4 in the illustration below. The code was assigned to the appropriate stations as c1, c2, c3, and c4, while the data was assigned to the appropriate stations as d1, d2, d3, and d4.