In the first part of this text, you got to know the second generation (2G) mobile technologies: TDMA, CDMA, GSM, GPRS and EDGE , which were (and are) essential for the popularization of mobile telephony. In this second part, you will see the characteristics of the technologies CDMA-2000 (and their variations), UMTS (W-CDMA) and HSPA (HSDPA and HSUPA) , which are part of the so-called third generation (3G, see ABBREVIATIONFINDER). Finally, you will learn about LTE technology , which fits into the advanced fourth generation (4G).
For better understanding, it is recommended to read the first part mentioned , if you have not already done so, since concepts or technologies related to 2G standards are also mentioned here.
3G Technologies
The term 3G refers to the third generation of mobile phone technologies. Internet access from mobile devices has become even more popular with 3G standards because of its speed, even making many people think that these two characters are merely synonyms for “mobile internet”, but it is much more than that.
The main idea of 3G is to make it possible for users to have mobile access to the internet with quality similar to fixed broadband connections, in order to be able to take advantage of features such as video streaming , audio applications, multimedia messages, among others. Not least, operators have even started to market the so-called “3G modems”, devices equipped with SIM cards developed to allow access to the internet via 3G networks on notebooks and desktops.
As already reported, 3G networks are formed by the technologies CDMA-2000 (and its variations), UMTS and HSPA (HSDPA and HSUPA). You will learn about each of them below.
What is CDMA-2000?
The name CDMA-2000 (a term coined by Qualcomm) actually refers to a set of standards, starting with CDMA-2000 1x , which is also known as CDMA 1xRTT (1x Radio Tansmission Technology). As the name implies, it is a technology that is based on the CDMA communication standard, being considered an evolution of CDMAOne.
Although it also allows approximately twice as many connections for voice as the first versions of CDMA, CDMA-2000’s main feature is its ability to work with data transfer rates of up to 144 Kb / s (307 Kb / s in theory) , with the upload being practically at the same speed level, all using only one carrier (in a nutshell, radio frequency wave where the information is transmitted) of 1.25 MHz.
Despite being rated as 3G, it is not uncommon to find literature that describes the CDMA-2000 1x as being 2G or even 2.5G. It makes sense: the characteristics of this version make it, in fact, “pre-third generation”.
It didn’t take long for an improved version of the standard called CDMA-2000 1xEV (Evolution Data) to appear on the market that has two classifications: CDMA-2000 1xEV-DO (Data Only), which implements only data channels; and CDMA-2000 1xEV-DV (Data and Voice), which allows the use of channels for both voice and data.
From the speed point of view, the 1xEV-DO and 1xEV-DV versions can be considered closer to 3G, since they can offer data transfer rates of up to 3.1 Mb / s (megabits per second) and upload rates up to 1.8 Mb / s.
There is also a variation called CDMA-2000 3x (or CDMA 3xRTT) that, as the name implies, uses three 1.25 MHz carriers. In this case, the transfer speed can reach 2 Mb / s.
CDMA-2000 technologies can work with various frequency bands, such as 450 MHz, 850 MHz, 1.9 GHz and 2.1 GHz.
What is UMTS?
Acronym for Universal Mobile Telecommunications Service (something like ” Universal Mobile Telecommunications System”), UMTS is seen as an evolution of the GSM standard, with its implementation being able to even take advantage of its structure. UMTS is considered, in fact, a third generation technology in itself.
UMTS arose mainly as a result of work involving companies and entities linked to the 3GPP (Third Generation Partnership Project) consortium , which leads the efforts for the development of technology. Until then, work related to the GSM standard was commanded by ETSI (European Telecommunications Standards Institute).
UMTS technology has among its main features the implementation based on the W-CDMA standard, discussed below. Subsequently, a variation based on the HSPA standard emerged.
What is W-CDMA?
Acronym for Wideband Code Division Multiple Access (something like “Broadband Code Division Multiple Access “), W-CDMA is a standard for radio frequency use based on the same communication concepts as CDMA that enables UMTS to achieve rates of up to 2 Mb / s for download and upload, although it does not usually exceed 384 Kb / s. These speeds are possible, among other reasons, thanks to the use of a 5 MHz carrier (against 1.25 MHz of CDMA-2000, worth remembering).
The W-CDMA has essentially two modes of operation: the TDD (Time Division Duplex – something like “Duplexing Time Division”) where the download activities (downlink) and upload (uplink) share the same carrier, but at different intervals (slots); and FDD (Frequency Division Duplex – something like “Duplexing by Frequency Division”), which uses different carriers for each of these activities, with a frequency range of 190 MHz between them.
The use of TDD and FDD makes transmission more efficient, since each mode is more suited to certain situations. For example, TDD is more advantageous in “asymmetric” applications, such as Web services, where the number of data sent is usually different from the amount received.
What is HSPA (HSDPA / HSUPA)?
If W-CDMA can provide reasonable data transfer rates, HSPA specifications , which stands for High Speed Packet Access (something like ” High Speed Packet Access “), also used in UMTS, can go much further: they offer speeds larger and can support a greater number of users.
As an evolution of W-CDMA, HSPA is based on two protocols: HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access). Both work using 5 MHz carriers, but HSDPA is directed to download, while HSUPA, in addition to this aspect, also focuses on uploading.
HSDPA can offer data transfer rates of up to 14.4 Mb / s (the other speeds are 1.8 Mb / s, 3.6 Mb / s and 7.2 Mb / s), while HSUPA (also known as Enhanced Uplink – EUL) offers a maximum speed of 5.76 Mb / s. Such high levels are due, for other reasons, to the reduction of the TTI (Transmission Time Interval – ” Transmission Time Interval “), which varies between 1 and 3 milliseconds, while in other standards this measure revolves around 10 milliseconds.
As they are more recent, the HSPA specifications are also called “3.5G”.