TELECOM Digest OnLine - Sorted: Re: When is TDMA Being Phased Out?

Re: When is TDMA Being Phased Out?

John Levine (
30 Nov 2005 22:11:57 -0000

> Could someone describe what is "TDMA" and "GSM" in layman's terms?

They're two different digital mobile protocols that are technically
fairly similar, but incompatible with each other. The practical
difference is that GSM phones use a SIM chip and TDMA phones don't.
You can move your SIM chip to any GSM phone and it'll work. Switching
TDMA phones requires help from the carrier to reprogram the phone and
put the new phone's serial number into the switch.

Outside of the Americas and Japan, most mobile systems in the world
are GSM, and GSM systems are very well integrated. I have SIM chips
from Switzerland and Luxembourg, and if I put one of them into my
phone, by golly, you can call it on my Swiss or Lux phone number
(forwarded to the US at great expense to me, of course.) At the
moment I'm in Vancouver, so I bought a prepaid GSM SIM with a
Vancouver number to use while I'm here.

> I get the impression all three companies are actually a hodgepodge of
> smaller companies they acquired and merged into along the way. That
> means service quality of a particular carrier will vary greatly from
> one part of the country to another, just as landline service varies
> greatly. (In Verizon particularly which is made up of many different
> companies).

That's true, they're all working on it to integrate their networks and
make them work more consistently. Most of the recent merges have been
between networks with the same technology, e.g., Cingular and AT&T
were both TDMA moving to GSM, so the phones all work, but sometimes
they think they're roaming.

Sprint and Nextel is different, the technologies are completely
incompatible and it remains to be seen if they're going to migrate
Nextel's iDen customers to Sprint's CDMA network, move to CDMA in
Nextel's band (which propagates better than Sprint's) or what.



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