CDMA vs GSM

[itwerk]

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?:iphone:

 

[hookbill]

I decided to google that. You aren't the only one asking this question. Best answer I can give is it's two different types of technology.

 

[LtKen]

There was a thread about this awhile back, and someone had a really good answer. Cant seem to find it now.

PC Today Article - CDMA vs. GSM

That might help.

 

[wsbsteven]

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)

 

[hookbill]

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(not a tech benefit but a benefit nonetheless)

I assume that's meant in more markets world wide?

 

[bastosero]

Phones that use SIM cards are GSM. Phones that don't are CDMA (like the Droid).

 

[Fletchi18]

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(not a tech benefit but a benefit nonetheless)

I assume that's meant in more markets world wide?

Yes, GSM is used in the vast majority of the countries around the world.

I'll add this subjective view to the comparison: I've noticed that when I use GSM phones, or talk to someone on a GSM phone, they sound 'tinny' where CDMA calls are much clearer.

 

[mach330]

back when i was working for qualcomm (where cdma was created) i was given this analogy:

gsm/tdma:
- 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.

cdma:
- 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.

 

[jsh1120]

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.

 

[bastosero]

Now when 4G comes along, we will be able to use voice and data together.

 

[wsbsteven]

back when i was working for qualcomm (where cdma was created)

Qualcomm didn't invent CDMA, they invented the CDMA2000 3G standard. CDMA was invented over 40 years prior to their foundation and was used in World War 2. The analogy used is correct though and very simple.

Qualcomm Products and Services - 1X Advanced - Four-fold increase in voice capacity

CDMA network.CPT1


"CDMA became commercially available only in the mid-1990s. However, the origin of CDMA can be traced back to 1940. The roots of CDMA technology are in the military field and navigation systems. Originally developed to counteract intentional radio jamming, it was later proved to be suitable for cellular communications. CDMA has its roots in pre World War 2 America. In 1940, Hollywood actress turned inventor Hedy Lamer and co-inventor George Antheil, with WW2 looming, co-patented a way for torpedoes to be controlled by sending signals over multiple radio frequencies."

 

[unix.punkx]

GSM is technically faster but AT&T will be on the same network as Verizon (technology wise) once they roll out (both companies) the LTE 4G network. Sprint already has their 4G service in select cities, however it is based on WiMax and not the LTE technology.

 

[takeshi]

Phones that use SIM cards are GSM. Phones that don't are CDMA (like the Droid).

To further confuse things: iDen phones also use SIM cards. So do CDMA/GSM hybrid devices (such as the Blackberry Storm).