Question

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Compare and contrast Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), and Code Division Multiple Access (CDMA). What are the advantages and disadvantages of each access method?

Answer 1

Frequency division multiple access (FDMA):
FDMA is a technology thet, the total bandwidth available to the system is divided into frequencies. This division is done between non overlapping frequencies assigned to each communicating pair.FDMA is used mainly for analog transmission. This technology is also capable of carrying digital information, but it is not considered to be an efficient method for digital transmission. Because if the frequencies to handle communication,what about the situation that required more capacity. Then existing frequencies becomes much narrower amount which will not be very efficient. In FDMA all users share the satellite simultaneously but each user transmits at single frequency.Best example of FDMA is FM radio. All the radio channels have their own frequency bands and they send their signals at the allocated unique frequencies within the available bands.

Code division multiple access (CDMA):
In CDMA technology separates calls by code. Every part of conversation is with a specific and unique code. If the system gets a call,it allocates a unique code to that particular conversation, and then data is split into small parts and is tagged with the unique code.After that, this data of small pieces is sent over a number of the discrete frequencies that available for use at any time in the specified range. At the end it reassembles the conversation from the coded bits and deliver it.
For example , collecting luggage at the end of the flight journey.

Time division multiple access (TDMA):
Unlike FDMA and CDMA, In TDMA the division of calls based on time. The system first digitizes the calls, and then combines those parts into a unified digital stream on a single radio channel. Now it divides each cellular channel into three time slots,a time slot is assigned to each call during the conversation, a regular space in a digital stream. The users transmit in rapid succession, one after the other, each using its own time slot. In this technology this allows multiple stations to share the same transmission medium .The main advantage of this technology is, it enables three different users to use one frequency at the same time.There is no need for three separate frequencies like in FDMA.Instead of allocating a single radio channel for a single call, TDMA efficiently carries three calls at the same time.