Mobile phone technology is attached in our everyday life. Mobile phone has given us the independence to communicate between each other regardless of place, city and country and the backbone of this is mobile phone technology. A mobile phone is owned by three among four people in this world. This growth of mobile technology is tremendous.

There are many technologies in use in mobile communication. Those are like GSM (Global System for Mobile Communication), CDMA (Code Division Multiple Access), EDGE (Enhanced Data Rate For GSM Evolution) to UMTS (Universal Mobile Telecommunication System) or W-CDMA (Wide Band Code Division Multiple Access) and CDMAOne (IS-95) to CDMA 2000 1X, EV-DV and Mobile TV technologies such as Media FLO, DMB and DVB-H.

GSM (Global System for Mobile Communication) is the most widely used mobile communication technology in the world. This technology gives us the advantage to use the mobile communication service all over the world through roaming. One of its advantage to make it become popular is interoperability.
The letters originally was the abbreviation of the words Group Special Mobile, but as it becomes popular enormously, the meaning of the words also change radically and now it stands for Global system for Mobile communications. The GSM technology was first used in the year 1991 and it is increasing rapidly for some of its unique advantage. Now the total number of GSM subscriber in the world is around 3 billion and this number is increasing steadily.

GSM System overview:
GSM technology is the 2G (second generation ) mobile communication technology. The aim was to serve a large number of subscriber and increasing the channel capacity and giving the advantage of interoperability which was not there in the analog system (first generation system) earlier. GSM achieved this by using a multiplexing technique which is called as TDMA (Time Division Multiple Access). By adopting this it was possible to accommodate a large number of user in a limited bandwidth by increasing the channel capacity. In additional to this ciphering was added to encrypt the voice in the communication medium. The previous system was not that much secured and anyone was able to trace the voice data through a receiver.

GSM basic services:
Voice communication s the basic service that GSM provides. To provide this service in GSM the voice data is first encoded and then decoded by a vocoder device. As the voice service is the basic service in GSM, in addition to this GSM system also provides other services. Though their quality is that much keen like the 3G service still those are popular where the 3G service is still not available. GSM supports data rate up to 9. 6 kbps, teletext and voice text and other value added services.

A service that provided by GSM which is enormously popular and availed by the people of every category is short message service (SMS). Earlier this was developed only for GSM but after that other mobile technologies also adopted this and this is successfully used in all technologies. This service has become popular in all mobile phone services, particularly young people likes this because the cost is low and this service provides alphanumeric messaging, forwarding, bidirectional messaging etc.

GSM Technology Basics:
GSM technology uses 200 KHZ RF frequency channels. In this technology each carrier is divided into eight carriers to give access to eight users in a carrier. This is called time division multiplexing. So, this is why it is called a TDMA (Time Division Multiple Access) system.

The BTS (Base Trans-receiver Station) are located in a small groups’ BSC (Base Switching Center) controls a group of base trans-receiver station, a MSC (Mobile Switching Center) controls all these BSC’s. Attached with this is two other devices HLR (Home Location Register) and VLR (Visitor Location Register) which tracks the location of the mobile.

EDGE:
The evolution of GSM is EDGE. Implementing EDGE data can be transferred up to a speed of 384kbps. In some cases it is also called as EGPRS (Enhanced General Packet Radio Service System). This system can be called as 2. 5G system. GSM uses Gaussian Minimum Shift Keying for data transfer but EDGE uses the 8 PSK which increase the data rate significantly.

GSM EDGE Basics:
GSM EDGE cellular technology is an update to the existing GSM network technology. This can be implemented in the existing GSM network by installing software.

CDMA1x2000 Technology:
CDMA1X2000 is the up gradation of the original IS-95 CDMA one system. CDMA has a number of evolution for which CDMA1X2000 is the first one.

The aim of this CDMA1X200 is to provide a migration path from the original CDMA one which is existing. This format is the basic 3G standard.

The first change that was made in CDMA1X200 was in the Walsh Code which was initially 64 bits in CDMAone and now it is being changed to 128 bits. Another code name turbo code was introduced in this technology to detect the error more efficiently.

In CDMAone a form of QPSK was used where the data in both I and Q channel was same but in CDMA1X2000 the data in Q and I channel is different. So, half of the bandwidth can be used for same number of chips or in other words double number of chips can be sent through the same bandwidth.

So, the CDMA1XX2000 has provided an efficient spectral efficiency and also improves the performance and the data rate is significantly high.

3G HSPA or High Speed Packet Access:
The technology 3G HSPA or High Speed Packet Access is a technology which is a combination of two technologies, one is the up-link and one is the down-link which can be built on to the existing 3G-UMTS or W-CDMA technology to provide increased data transfer speeds in data transmission.

16 QAM is used in the down-link to increase the data rate. Here, sharing the channels provide a great efficiency and also integrates with IP and packet data concepts.

3G LTE or 3G LONG TERM EVOLUTION:
To compete the high data rate services like WiMax, the work on next generation of cellular technology is already been started and also implemented in some cases.

The third generation partnership project that works on the development of the UMTS 3G started their evolutionary work with a workshop that was held in Toronto, Canada on November, 2004.

The target of LTE is to get the download speed up to 100Mbps and upload speed of 50Mbps in each 20Mhz spectrum. LTE is also required to serve 200 active users in each 5MHz cell.

The basic work of 3G LTE is already been done by 3GPP and the infrastructure upgrading task is also going on parallel.