CDMA vs GSM - Difference and Comparison

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CDMA

GSM

Currently 3.71/5
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Rating: 3.7/5 (49 votes)

Currently 3.89/5
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Rating: 3.9/5 (46 votes)

Stands for:

Code Division Multiple Access

Global System for Mobile communication

Global market share:

18%

82%

Dominance:

Dominant standard in the U.S.

Dominant standard worldwide except the U.S.

GSM (Global System for Mobile communications, originally from Groupe Spécial Mobile) is the most popular standard for mobile phones in the world, with its promoter, the GSM Association, estimating that the GSM service provides 82% of the global mobile market and is used by over 2 billion people across more than 212 countries and territories.

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.

Whereas Global System for Mobile Communications (GSM) is a specification of an entire network infrastructure, CDMA relates only to the air interface — the radio portion of the technology. For example, GSM specifies an infrastructure based on internationally approved standard, while CDMA allows each operator to provide network features it finds suitable. On the air interface, the signalling suite (GSM: ISDN SS7) work has been progressing to harmonise these features.

1 Subscriber Identity Module (SIM Card)
2 International Roaming with GSM and CDMA
3 Data Transfer Methods in GSM vs. CDMA
4 Interaction between GSM and CDMA
5 Prevalence of CDMA vs. GSM
6 Related Articles
7 References

[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.

[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] Prevalence of CDMA vs. GSM

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. In India, Hutch, Bharti and BSNL are on GSM whereas Reliance and Tata Tele are on CDMA networks.