First, I'm a fan of GSM since it is an open standard made by the ETSI guys. Go to http://www.etsi.org get an account and download the standards. I'm curious about your statement on saying IDEN is more secure than GSM or CDMA. IDEN is Radio and TDMA combined, and propietary. GSM & TDMA are not more secure than CDMA, as CDMA is base on code access using orthogonal functions. GSM and TDMA are somewhat similar in that they both provide multiple access to one channel through multiple time slots, hence being less secure. The cool thing about GSM (me favorite) and CDMA from a service provider is they actually have an upgrade path to 3G, TDMA does not or at least it won't be supported. GSM (circuit switched) goes to GPRS (packet switched) then to your choice of EDGE or WCDMA. Sim cards will be supported through the entire path. For the CDMA guys CDMA to CDMA 1X to CDMA2000, Qualcom earns royalties off this technology(me least favorite). From the service providers view it is cost effecient if they choose CDMA or GSM and stick with the upgrade path. Cingular & AT&T find themselves switching from TDMA to GSM, because no one is really providing an upgrade path for TDMA, although a standard was written for TDMA based 3G, no one will support it. By the way, Verizon is a CDMA based network and over 80% of the world uses GSM. IDEN who?
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If you want a phone that will work almost anywhere checkout AT&T's Siemens TDMA/GSM tri band phone TDMA/GSM tri band phone /a> . AT&T's TDMA coverage is by far the most in the U.S (compared with GSM & CDMA) and it can also be used where AT&T is sprouting up their new GSM network(CA, TX, FL...) not to mention Europe, Asia, South America.... The only country I can think of is perhaps South Korea they're using CDMA. So if you don't plan on going to South Korea. It would be a good idea to buy one off the net (costs more) that does not come sim card locked, You know, that way when you're on you're in Italy or France you can still use the same phone, it would be just a matter of swapping out sim cards with the providers that reside in that country. Also you could switch over to T Mobile at anytime.
Also clearing up some mis stated comments earlier:
"CDMA is a good standard.. Very fast data compared with GPRS (CDMAx1=144Kb/s theoretical vs GPRS=40.2Kb/s)"
GPRS is actually 171 Kb/s theoretical, using all 8 time slots of course, However in actual use the speed is much less than theoretical, as always with any technology especially in its initial use actual is far from theoretical. Also CDMA 1X is what I believe he's refering to, CDMA is only about 19 kb/s, this is because 2G is circuit switched(time based) not packet switched like 2.5G and up.
"First I would recommend looking seriously at the CDMA network or one of the other 2.5G networks."
CDMA is a 2G standard ->CDMA 1X is 2.5G -> CDMA 2000
GSM is a 2G standard -> GPRS is 2.5G-> WCDMA or EDGE is 3G
When you hop on a network provider with GSM this is what they'll offer you as an upgrade path to 3G over the next years. When you use 2.5G (GSM/GPRS based), you would still use GSM for voice, but GPRS for data.
It's not a question of what are service providers going to, but a question of which path they choose first and then which Generation have they upgraded to. At the minimum they must have either 2G (CDMA or GSM).
How to speak Australian I personally nominate Kazaa!
First, I'm a fan of GSM since it is an open standard made by the ETSI guys. Go to http://www.etsi.org get an account and download the standards. I'm curious about your statement on saying IDEN is more secure than GSM or CDMA. IDEN is Radio and TDMA combined, and propietary. GSM & TDMA are not more secure than CDMA, as CDMA is base on code access using orthogonal functions. GSM and TDMA are somewhat similar in that they both provide multiple access to one channel through multiple time slots, hence being less secure. The cool thing about GSM (me favorite) and CDMA from a service provider is they actually have an upgrade path to 3G, TDMA does not or at least it won't be supported. GSM (circuit switched) goes to GPRS (packet switched) then to your choice of EDGE or WCDMA. Sim cards will be supported through the entire path. For the CDMA guys CDMA to CDMA 1X to CDMA2000, Qualcom earns royalties off this technology(me least favorite). From the service providers view it is cost effecient if they choose CDMA or GSM and stick with the upgrade path. Cingular & AT&T find themselves switching from TDMA to GSM, because no one is really providing an upgrade path for TDMA, although a standard was written for TDMA based 3G, no one will support it. By the way, Verizon is a CDMA based network and over 80% of the world uses GSM. IDEN who?