CDMA is the leading GSM competitor. Despite being superior in some respects, the CDMA is a Qualcomm proprietary standard, which receives royalties on equipment sold, while GSM is an open standard.
Technically speaking, the CDMA is a technology used as a basis for cdmaOne and CDMA2000 standards, which are the telephony standards. Both are referred to as “CDMA“, which is the term popularly used. If you are interested in the technical details, see the link cdg.org/technology/cdma.asp.
The CDMA plan still has some interest here in Brazil, Embratel’s network and Vivo’s CDMA network, which remains active. It is true that the pattern of use will decline over time, but it can still take a while, so it is interesting to know a little about the technology.
With respect to the data traffic, which is what interests us, the most basic means of access within the CDMA works at 14.4 kbits, which seems to joke near the current standards, but it was acceptable at the time that the system began to be implemented, since the CSD (which at the time was the direct competitor) operated just 9.6 kbits.
The following default (which turned out to be the most used on a large scale surviving until some time ago) is 1xRTT (also known as 1xRTT CDMA 2000), which multiplied by 10 baud rate, reaching 144 kbits. Although faster than GPRS, the 1xRTT is also considered a form of access 2.5G.
Besides being used for access on CDMA phones, the 1xRTT was used in the first version of Vivo Zap*, who inaugurated the use of the plans of web access via USB modems. Even with the deployment of EVDO Vivo network, 1xRTT continued to be used as a fallback system for areas where EVDO was not available, or for use on older devices without support for the new system.
With the implementation of UMTS 3G networks of Claro, Tim and after Vivo, the 1xRTT seemed destined to leave the scene definitely, but ended up having an unexpected return with the purchase of Vesper by Embratel**, who inherited the license to provide services access based on CDMA standard.
Like any wireless data transmission protocol, 1xRTT has a relatively large overhead, which, combined with the traditional jams and fluctuations in the signal, causes, in practice, the speed is not much greater than the dial-up. However, 1xRTT has a small advantage, which is the best penetration in rural areas or obstacles, allowing the service to be used in many areas of poor coverage, where other forms of access are not available.
Then we have the EVDO (also called EV-DO, 1xEV-DO and CDMA 2000 EVDO), which is the 3G standard within the CDMA, offering data rates of up to 2.4 megabits. It was used in the initial version of Vivo Zap 3G that launched in 2005, ended up being the first 3G access service in Brazil, prior to the UMTS networks. As usual, 2.4 megabits are theoretical; in practice it is possible to achieve little more than 1 megabit in a good connection.
Although the EVDO be originally slower that UMTS, the final velocity depends more the quality of each carrier structure, thus as those defined band limitations. A UMTS plan limited to 512 kbits, for example, would be much slower than a connection via EVDO without limitations. In Brazil, this technology is used by Embratel in transmissions by broadband radio–frequency, both in commercial use as in home use. However, this technology is being discontinued by Vivo, being replaced by HSDPA technology.
* VIVO ZAP: It is a data plan for smartphone that was used in Brazil by VIVO Company. Today, was substituted by other plans.
** EMBRATEL: EMpresa BRAsileira de TELefonia, or Brazilian telephone company, one of the major national telephone companies, as Claro, TIM, Vivo, etc.
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MORIMOTO, Carlos Eduardo. Smartphones, guia prático / Carlos Eduardo Morimoto. – Porto Alegre: Sul Editores, 2009. Pages. 310-313. (with adaptations and updates)