How Cell Phones Work

How-Stuff-Works' Website

Before linking to this very good website explaining how cell phones work, it should be mentioned that one thing in the site apparently is wrong. They state that U.S. GSM and European GSM are not compatable, and that it is not possible to purchase one phone which will work anywhere in the world.

According to both T-Mobile's, Cingular's, and Nextel's Customer Services this is possible. In the case of T-Mobile, they have world-wide roaming agreements; and if one purchases the tri-band Worldphone, it can be used anywhere in the world where the roaming agreements are in place. In the case of Cingular, they do not have any foreign roaming agreements; and the user must purchase a prepaid SIM card to use his phone in any foreign country. Roaming in a foreign country is convenient but expensive. Thus the SIM-card solution is cheaper. T-Mobile also has the option of purchasing a SIM card, so in this sense, they have the best of both worlds.

Now to the link: For an excellent discussion of cell phone technology, go to How-Stuff-Works' Website. Take a special look at the page "Cellular Access Technologies". This has a very good discussion of TDMA and CDMA.