GSM vs CDMA
 

Hi. I'm trying to find a reasoned discussion or paper that details real-world differences between GSM and CDMA phones. It's been a long time since I've personally used CDMA, but when I did it would never work well in elevators, parking lots etc whereas my GSM device doesn't have the same problems.

There is a reason why GSM works in places that CDMA doesn't but I can't find what that reason is. Does anyone have any ideas?

Thanks!

The new forms of GSM (UMTS) use CDMA.

When you say "CDMA", you probably mean IS-95 & CDMA2000.

My understanding is that tower proximity (closer = better) and frequency (850mhz penetrates buildings better than 1900mhz) matter more than the "language" the phone speaks. So if your GSM provider has a tower on the roof of your building, but your CDMA provider doesn't, you're far more likely to get GSM service in the elevator. And if your GSM provider uses the 850mhz band (AT&T) but your CDMA provider uses the 1900mhz band (Sprint), you're also probably more likely to get GSM service in the elevator.

If there's a Verizon (CDMA 850mhz) tower on the roof, however, and the nearest GSM tower is a TMobile (GSM 1900mhz) tower a few blocks away, there will be no contest.

Exactly. I'm a big Verizon fan (CDMA) cuz in the places I frequent, Verizon has towers everywhere and so it works everywhere. The GSM companies don't work as well. Things are especially bad with T-Mobile cuz everyone knows they don't have that many towers and their reception reflects it.

Dead-on correct explanation. :)

Also

When you say "it's been a long time" since you used CDMA...carriers are building their networks all the time, increasing coverage and capacity. I worked for a carrier in the early 2000's that had a footprint that now would be laughably poor.

As said above - it ALL depends on where you are and what you're doing. Aside from domestic coverage issues, typically Asia favors CDMA while Europe favors GSM. Technologically there is no reason why, at the same frequency and with the same cell site that GSM would outperform CDMA. In fact, IS-95/CDMA2000 should actually work at a lower signal level in a low noise environment.

RFTraveler :)

GSM uses a combination of FDMA and TDMA (Frequency division multiple access and Time division multiple access). CDMA stands for Code division multiple access. CDMA is a little bit more intolerant to bad connections since the mobile device has to calculate the data stream by using its personal code out of the general data stream (has something to do with XOR function). If the stream has to many bad bits it doesn't work. GSM doesn't calculate only anything. It just has to send and receive during its time slot (milliseconds).

CDMA can be in soft handoff between multiple cells. This gives it a huge advantage in error correction - if a GSM data stream (the voice call) is interrupted, there is only so much that can be done in processing. CDMA, on the other hand, can meld multiple data streams together and so can resolve calls with a far weaker signal.

RFTraveler :)

Aside from Korea and Japan, GSM is far more widespread in Asia than CDMA.

If you want to use it abroad anywhere aside from those two countries, you'd be mad to consider anything but GSM (at the moment). For coverage within the US I cannot comment as I'm from Europe.

This nails it and is the biggest difference... GSM is pretty-much international and CDMA isn't. I carry 2 phones, my Verizon for when I'm here and a GSM united-moblie SIMM'd phone for when I travel.

But, the OP was looking for an article... here you go:

http://www.appleinsider.com/articles...ma_iphone.html

http://www.appleinsider.com/articles...g_network.html

Granted... those are IPhone based but they have comparisons.

-SF

All depends where you are. I've never been impressed with Verizon. I have T-mobile and it works quite well in Chicago.

In general, the 800 MHz (A/B band cellular) carrier will outperform the 1900 MHz (PCS) carrier. But if you've got a 1900 MHz tower next door and a 800 MHz one a few blocks away, the 1900 service will be better.

This site has more info on CDMA: http://www.cdg.org/

China Telecom uses CDMA and had announced a multi-billion dollar upgrade recently. They are smaller than China Mobile but still a huge number of subscribers.

These days many phones are capable of using both GSM and CDMA networks, so from the user's point of view it doesn't matter. I have a European phone, Nokia E71 (step aside, Blackberry!) and use it without a hitch in JP and KR.

Yes, but . . .

CDMA is available in large cities (at least) in China.

If you're in the U.S., you'll get better coverage and reception with Verizon, which is CDMA. Just pick up a cheap GSM phone and buy a local SIM card for when you travel -- it will be lots cheaper than taking a U.S. carrier's GSM phone with you. Verizon also has the Motorola z6c, which is a dual CDMA/GSM phone.