How Does A FDMA Cell Phone Work?

Though virtually all new wireless phone handsets now sold are digital, an analog FDMA cell phone can still be the right choice for rural areas where digital cell coverage is either severely restricted or even non-existent. So checking out coverage maps of the various cellular phone service carriers when reviewing their flashy cellular phone promotions is always an essential task.

Of course you can have the best of both worlds with a dual-mode cell phone, which can perform both as FDMA cell phones and digital cell phones, depending on circumstance.

All cellular phones used to be analog when the availability of a commercial cellular telephone started off in the early eighties, and before the arrival of the digital cell age around a decade later, which brought the world the likes of CDMA, TDMA and GSM technology. And for brief explanations of these cell phone systems, you should read the articles:

But now for a look at how FDMA cell phones work their older (if less impressive) magic.

FDMA is an abbreviation that stands for Frequency Division Multiple Access, and this is a description of one way of using cell phones that could actually carry digital information if other better ways were not used instead, so it remains as the standard for cellular analog.

The cellular telephone system works by dividing up a geographical area into multiple smaller sections known as cells, each of which are perceived as taking on the shape of a hexagon over the area of about 10 square miles, and fit neatly together like a honeycomb in a bee hive.

Now a cell phone is really a kind of radio, and is known as a full-duplex device; this means that it will transmit on one cellular frequency and transmit on another. Which in turn means that a cell phone conversation can proceed as it would naturally, with both people talking without having to wait for the other to finish what they are saying first!

Each cell phone service provider has 832 such radio frequencies for their cellular phones to use (frequencies are the rate at which sound waves vibrate) to use within a city, 42 of these are used for non-voice cell phone calls and the other 790 is then divided in pairs (one to transmit - one to receive) to get at 395. Now you divide 395 by 7 (each individual hexagonal cell plus its six neighboring cells) to come to the number of 56. (Alright 56.4 but let’s not get picky).

So with FDMA cellular analog each cell phone carrier has 56 voice channels per cell at any one time for cellular customers to use their cell phones simultaneously; and each transmitting cell frequency has a separation of about 45 MHz from its partner receiving frequency, to prevent them from interfering with one another.

In the USA analog cell phones work in the 800 MHz range, and FDMA analog cell phones divides these frequencies along the designated part of the spectrum up for us to use. Frequency Division Multiple Access, remember - it just means dividing frequencies for access by many cell phone users.

But many more cellular phone users can be accommodated on a digital platform, and within this new world phones themselves can have so many more features and accessories that many of us demand now like on-board digital cameras for example. So the cell phone can be yet more adaptable still than just a phone with improved voice clarity, as important as that obviously is.

Also see; answers to common cell phone questions.

Author Notes:

Matt Jacks contributes and publishes news editorial to http://www.cell-phones-n-plans.com. A cell phone industry resource that features service plan comparisons, cellular phone reviews and articles.