can someone tell what the difference is between the 2? I know Verizon and sprint use cdma and at&t and tmobile use gsm. What's the difference?
Going off the top of my head so feel free to correct me if I'm wrong on something.
GSM can travel further
CDMA can handle more connections per tower
GSM allows voice and data at the same time (ATT commercials)
CDMA has better building penetration
CDMA can tolerate a lower signal before dropping calls
GSM is used in more markets world wide(not a tech benefit but a benefit nonetheless)
Last edited by wsbsteven; 03-03-2010 at 01:08 PM. Reason: Clarification
back when i was working for qualcomm (where cdma was created) i was given this analogy:
- to talk to someone, you have to take them to a private room. in a house the number of rooms are limited. if there's no separate room to talk, then you can't talk (call is dropped). also, the limitations of the number of rooms is the biggest hurdle as far as in having a lot of people talk to each other in a single house.
- everyone talks in a different language. to talk to one another, you can stay in one room and talk to the person in front of you in a different language. you don't have to go to a different room to talk. you are not limited to the number of rooms.
just something simple.
also, we do a lot of test on idle channel noise (when people are not talking so you hear background noise). cdma has a much stricter idle channel noise measurements. hence...i feel that when i talk to cdma people, they come out much clearer as oppose to someone on att.
One can get all sorts of comparisons in technical terms, but the heart of the matter from a consumer/performance standpoint is that CDMA "streams" a signal while GSM "packages" a signal into discrete little packets that "chop up" a data stream and reassembles them on the other end.
This gives CDMA an advantage in terms of speed but does not allow two messages (e.g. data and voice) to share a "stream." In a GSM environment all the little packets are independent of one another and can share a connection. That's the heart of the AT&T's simultaneous "browse and talk" advertising.
From a carrier's point of view CDMA more or less shackles a consumer to one carrier (or at least to carriers who use the same version of CDMA.) GSM, on the other hand, because it stores phone data on a sim card, allows a user to move from one phone to another or one carrier to another in a more or less transparent fashion.
The entire rest of the world (other than the US and Iraq) concluded that regardless of other issues the greater flexibility provided to consumers was a good reason to opt for GSM. And that's why in Europe, Asia, etc. consumers usually buy phones and then look for a carrier rather than the other way around.
All in all, US consumers would be better off from a financial standpoint if we used the model adopted almost everywhere else. The upfront cost of phones would be higher but the carriers would not have to recover their equipment subsidies through monthly charges. Unfortunately, US consumers' addiction to credit has meant that subsidized phones tied to long term contracts is the model that has triumphed here.