[geeks] Opinions on T-Mobile and Verizon

[Geoffrey S. Mendelson]

On Sat, Nov 24, 2007 at 12:46:59PM -0500, Shannon Hendrix wrote:
> ...but I thought GSM was just a modification of TDMA and another  
> related technology?

Ys and no. What you are referring to as TDMA is D-AMPS. D-AMPS is
the old AMPS protocols implemented using TDMA instead of FM radio
for the voice portion of the telephone conversation. Even in AMPS,
the control information was all digital. 

GSM is a completely different protocol which also uses TDMA for
the voice data.

GSM has also been implemented under other methods of transmission,
notably CDMA, but it does not fit the standard and never took off
due to the other failings of CDMA.

Back when it was still AT&T wireless, they migrated their AMPS
network to D-AMPS. By the year 2000, they found that D-AMPS did
not provide the services their customers wanted and was faced with
one choice, CDMA, because GSM equipment was not available for 800mHz.


Instead of choosing CMDA, they were able to order enough to get Ericson
and Nokia to make 800mHZ GSM equipment for them. The difference between
GSM 800 and GSM 850 is that one side of the conversation is on 800 mHz,
the other is on 850 mHZ. AMPS describes one side, GSM the other,
but I don't remember which.


Here the original carrier was AMPS who moved to NAMPS and then CDMA.
They are about to phase out CDMA service and replace it with GSM.
The second carrier was D-AMPS (aka TDMA) and is now GSM. The third
carrier started late (1998) and has always been GSM.

Motorola was an original partner in the first carrier. When they
sold out, they started selling MIRS (trunked radio) service as
cellular service. 

Geoff.
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