GSM and CDMA are competing wireless technologies with GSM enjoying about an 82% market share globally. In the U.S., however, CDMA is the more dominant standard. Technically GSM (Global System for Mobile communications, originally from Groupe Spécial Mobile) is a specification of an entire wireless network infrastructure, while CDMA relates only to the air interface — the radio portion of the technology.

Code division multiple access (CDMA) describes a communication channel access principle that employs spread-spectrum technology and a special coding scheme (where each transmitter is assigned a code). CDMA also refers to digital cellular telephony systems that use this multiple access scheme, as pioneered by QUALCOMM, and W-CDMA by the International Telecommunication Union (ITU), which is used in GSM’s UMTS.

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Stands for Code Division Multiple Access Global System for Mobile communication
Storage Type Internal Memory SIM (subscriber identity module) Card
Global market share 25% 75%
Dominance Dominant standard in the U.S. Dominant standard worldwide except the U.S.
Data transfer EVDO/3G/4G/LTE GPRS/E/3G/4G/LTE
Network There is one physical channel and a special code for every device in the coverage network. Using this code, the signal of the device is multiplexed, and the same physical channel is used to send the signal. Every cell has a corresponding network tower, which serves the mobile phones in that cellular area.
International roaming Less Accessible Most Accessible
Frequency band Single (850 MHz) Multiple (850/900/1800/1900 MHz)
Network service Handset specific SIM specific. User has option to select handset of his choice.

Contents: CDMA vs GSM

A CDMA tower, viewed from the bottom up
A CDMA tower, viewed from the bottom up

edit Subscriber Identity Module (SIM Card)

SIM (subscriber identity module) card, the onboard memory device that identifies a user and stores all of his information on the handheld. You can swap GSM SIM cards between handsets when a new one is necessary, which enables you to carry all of your contact and calendar information over to a new handset with no hassle. CDMA operators answer this flexibility with their own service that stores user data, including phone book and scheduler information, on the operator’s database. This service makes it possible to not only swap over to a new handset with little trouble, but it also gives users the ability to recover contact date even if their phone is lost or stolen.

edit International Roaming with GSM and CDMA

Where international business travel is an issue, GSM leaps forward in the race for the title of “Most Accessible.” Because GSM is used in more than 74% of the markets across the globe, users of tri-band or quad-band handsets can travel to Europe, India, and most of Asia and still use their cell phones. CDMA offers no multiband capability, however, and therefore you can’t readily use it in multiple countries. However, certain phones like the iPhone 5 now have Quad-band GSM built in so they can be used overseas with special calling plans from carriers.

edit Data Transfer Methods in GSM vs. CDMA

Another difference between GSM and CDMA is in the data transfer methods. GSM’s high-speed wireless data technology, GPRS (General Packet Radio Service), usually offers a slower data bandwidth for wireless data connection than CDMA’s high-speed technology (1xRTT, short for single carrier radio transmission technology), which has the capability of providing ISDN (Integrated Services Digital Network)-like speeds of as much as 144Kbps (kilobits per second). However, 1xRTT requires a dedicated connection to the network for use, whereas GPRS sends in packets, which means that data calls made on a GSM handset don’t block out voice calls like they do on CDMA phones.

edit Interaction between GSM and CDMA

In cities and densely populated areas, there are often high concentrations of GSM and CDMA connection bases. In theory, GSM and CDMA are invisible to one another and should "play nice" with one another. In practice, however, this is not the case. High-powered CDMA signals have raised the "noise floor" for GSM receivers, meaning there is less space within the available band to send a clean signal. This sometimes results in dropped calls in areas where there is a high concentration of CDMA technology. Conversely, high-powered GSM signals have been shown to cause overloading and jamming of CDMA receivers due to CDMA’s reliance upon broadcasting across its entire available band.

The result of this little cross-broadcasting joust has led some cities to pass ordinances limiting the space between cell towers or the height they can reach, giving one technology a distinct advantage over the other. This is something to note when choosing a wireless provider. The distance between towers will severely affect connectivity for GSM-based phones because the phones need constant access to the tower’s narrow band broadcasting.

edit Popularity and Market Share

GSM is a lot more widespread in Europe and Asia. In the United States, Sprint and Verizon networks are CDMA whereas AT&T and T-Mobile are on GSM. Most of Europe uses GSM and so does China. In India, Hutch, Bharti and BSNL are on GSM whereas Reliance and Tata Tele are on CDMA networks.

edit Video explaining the difference

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Comments: CDMA vs GSM

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Anonymous comments (13)

February 13, 2014, 3:12am

Most Useful content to the both users of CDMA and GSM mobiles.

— 42.✗.✗.150

April 28, 2014, 6:19am

Scrap cdma entirely

— 206.✗.✗.137

March 16, 2014, 3:46pm

here it is...

— 37.✗.✗.38

April 27, 2013, 1:33pm

i made gsm

— 117.✗.✗.100

December 6, 2012, 4:23pm


— 124.✗.✗.121

August 22, 2010, 1:13am

You guys do realize that HSPA is really an implementation if W-CDMA built on top of a GSM network right? The only part of the world that uses GSM exclusively is Europe, pretty much everyplace else has pockets of CDAM and GSM. North America, South America, Africa, Europe, The Middle East and Asia... all have CDMA along with GSM.

CDMA is actually a superior technology to GSM. It propagates further, works better inside structures, has built in noise cancellation, more calls per cel cite, automatically hands off calls to different cel cites to minimize congestion, and works better in low signal areas to name a few. The only thing that GSM brings top the table other than coverage in Europe, is better battery life, but that's because it is a less powerful chip-set.

It is true that eventually almost everyone int he world is going LTE, but Verizon is not "switching" they are transitioning, and their CDMA (EVDO-A) will be up and running for at least another 5-6 yeras if not longer.

— 75.✗.✗.94

May 30, 2010, 3:17am

I'm a bit surprised CDMA has lasted this long in the US. Other than India, who else uses that here in Asia?

— 115.✗.✗.206

January 4, 2010, 11:27pm

How do you see LTE as "part of the GSM family of technologies"? LTE supports both FDD and TDD mode. GSM does not, it is strictly Time Division.

— 72.✗.✗.215

November 26, 2009, 12:08pm

Dr Simon Geraldene, you have got it so wrong. WiMAX is a niche trechnology at best and is seriously struggling - it's losing money all over the world. The future is quite clearly GSM - so HSPA, HSPA Evolved/+ and LTE. There's no point comparing WiMAX with LTE - you should be comparing HSPA with WiMAX. HSPA and HSPA+ are used globally and gaining traction (200 million HSPA subscribers vs. WiMAX's 100,000 globally) - everything will lead to LTE (also part of the GSM family of technologies), but HSPA will be around for a good few years yet. Think global traction and economies of scale! Neither of which WiMAX has.

So LTE is the future - just look at what the operators in the US are doing:

- Verizon moving from CDMA to LTE in 2010
- AT&T moving from HSPA to LTE
- T-Mobile moving from HSPA to HSPA+, and the LTE

We'll ALL be using LTE withing 10 years - CDMA and WiMAX will be technologies of the past.

Johan Lassing, Sweden

— 80.✗.✗.212

June 11, 2012, 7:36pm

Good Information

— 221.✗.✗.66

April 11, 2011, 1:58am

John Lassing,
The reason other carriers don't use WiMAX is simply that they don't OWN the spectrum! Sprint Nextel bought up all of the 3.5GHz and MMDS licenses a while back, so Verizon had no choice but to move to the inferior technology. Granted Sprint and Clear have been very slow (VERY slow) in moving out coverage but the technology itself is solid. China? They're renowned for hanging on to old crap. I'm amazed they've moved past 2G at all!!

— 99.✗.✗.21

February 4, 2011, 8:06am

Well HSPA is build on top of W-CDMA. It actually incorporates multiple technologies (TDMA, W-CDMA and code multiplexing). So the comment that CDMA networks are superior and GSM-based operators have worse networks is, well totally misguided. Most GSM operators have a UMTS (aka. 3GSM, WCDMA, HSPA) overlay network. Both use CDMA as a base, but 3GSM expands it considerably. As to GSM limitations ,well 82% market share of GSM vs. 18% market share of CDMA kind of illustrates the difference. GSM and WCDMA is by far more prevalent than the dying CDMA. GSM also has had a constant roadmat through 3G to 4G. Also roaming works globally. It'll be around for some years, but it constantly in a downward cure (subscriber base wise). LTE and WiMAX are essentially the same technology. WiMax's main problem is that it didn't do mobility very well (makes sense if you look at the origins of the spec). LTE was brought out to make sure mobility works properly and thus is one of the big reasons that it prevail

— 83.✗.✗.183

October 29, 2009, 2:37am

CDMA is far superior. GSM is an old less efficient technology. GSM's only advantage is data/voice simultaneously. CDMA is faster, clearer, more secure, and much less likely to drop calls. Its the newest mobile technology. GSM will be around for quite sometime however. And CDMA will as well. There will be an eventual change in the near future shifting to WiMax and LTE using VoIP insead of traditional cellular voice. This is when mobile technology will get exciting. WiMax is the clear front runner. LTE is still just in talks while WiMax is up and running in select areas. WiMax is the future. If the LTE network is eventually built, it will be very powerful. But WiMax may have a stronghold on the wireless broadband industry by then. Time will tell. But I would bet on WiMax.

-Dr. Simon Geraldene
Sr. Mobile Network Engineer

— 72.✗.✗.1


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