3G Communication
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UMTS (Universal Mobile Telecommunications System) is also called third generation (3G), rates up to 2 megabits per second (Mbps). Having 2 Mbps, 3G is able to provide consistent set of services no matter where the users are located. UMTS consists of two main elements, UMTS Terrestrial Radio Access Network (UTRAN) and the Core work, offering the highest efficiency within a single system regardless of the conditions of wide area, urban, indoor coverage from outdoor or indoor. 3G was first implemented and standardized by cellular phone manufacturers for mobile users around the world in 2002. Having UMTS allows mobile users to have access through a combination of terrestrial wireless and satellite transmissions. A lot of the commercially available cellular phones have the features that are required for the 3G networks today. Mainly, a cellular phone needs to have a camera and a screen to send and receive video also an internet browser to explore the world wide web.
As demand for high speeds, capacity and reliability of data communications in mobile device networks increased, the third generation ā3Gā wireless technology has been planned, designed and deployed over the world. This technology provides more speed, higher frequency and larger bandwidth compared to the 2G technology. 3G networks have enough capacity to support 3G applications including rich multimedia content, fast reliable connectivity and mobility services. Examples of these services are customized infotainment, multimedia messaging services, mobile intranet/extranet access, mobile internet access, location-based services and rich voice, etc.
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Technical Background
Cellular Communications
In order to understand what 3G is, it is important to understand where it is coming from. Cellular phones are based on cellular technology, where a geographic region, such as a city, is divided into sub-regions or cells. Each cell contains a base station, which acts as an antenna to transmit and receive information over radio waves.
Cellular communication are a lot different than walky-talkies/radios since walky-talkies/radios require that both the transmitter and the receiver are on the same frequency, and only use one frequency at a time. Thus only one transmitter can talk at a time, and still share the same frequency. This method is called half-duplex mode. Cellular phones on the other hand use two frequencies, one to transmit and another to receive from the base station, also called full-duplex mode.1 Another advantage is that the information is digitized over the frequency in such a way that more than one cellular phone can use the same frequency to talk to the base station, also called channels.
There are two major protocols or methodologies that exist under 2G (The predecessor of 3G): Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA).2
Code Division Multiple Access (CDMA)
CDMA is an approach such that digitized voice is sent over the frequency in use by using a unique spread spectrum (or spreading code). Both the cellular phone and base station use the same code to encode and decode, thus allowing different cellular phones to share the same frequency. The cellular phone can only decode the data with the unique code it knows, and that is also how the base station knows whose data is being received. This method allows 8 to 10 different calls to be placed within the same channel.3
Time Division Multiple Access (TDMA)
TDMA is a time interleaving approach to share the same frequency by multiple cellular phones. It divides each channel into three parts, which the digitized voice data is compressed into. So in any channel, up to three calls can be going on at the same time.5
Global System for Mobile communications (GSM)
Global System for Mobile communications (GSM) is an implementation of TDMA with a few extra features. Unlike CDMA where the cellular phone must know the unique code to decode the information, TDMA lacks inherent security feature. GSM implements TDMA with an addition layer to deal with security.7 General Packet Radio Service (GPRS) is an extension to GSM. It enhances the data capabilities of GSM by increasing the bandwidth and speed for internet connectivity. It is also called 2.5G since it not part of the 2G specification, and a half step to 3G.
