Advancement in mobile phones technology has been marked by generation (G). Analog phones are related to the 1st generation (1G), and then come digital phones marked by second generation (2G). This second generation mobile phones has changed the concept of mobile phones by introducing high data transfer rate, increased frequency band and wireless connectivity.
There are three different types of technologies in the second generation these are FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access) and CDMA (Code Division Multiple Access). All types have one common feature of multiple access which means that many users are able to use the same number of cells. First part of all the technologies makes difference.
Because of different types of technologies utilizes in 2G mobiles, there are different types of mobiles according to the technology incorporate in them. Let see the 2G technologies use in mobiles and their functions as they work.
How 2G (FDMA) Works
Frequency Division Multiple Access (FDMA) enables the calls to use different frequency by splitting it into small cells. Each call uses different frequency. The phenomenon is same as in radio where different channels broadcast on separate frequency. So every radio station has been assigned different frequency according to the specific band available. FDMA is best in case of analog transmission but also support digital transmission. No doubt it is accommodating to the digital signals yet with poor service.
How 2G (TDMA) Works
Different technologies are categorized in second generation’s TDMA standard according to the different time zones indifferent countries in the world. These technologies are
- GSM (Global System for Mobile Communication) nearly used in the whole world.
- IDEN (Integrated Digital Enhanced Network) is introduced by Motorola used in US and Canada.
- IS-136 (Interim Standard-136) also known as D-AMPS (Digital Advanced Mobile Phone System) prevail in South and North America.
- PDC (Personal Digital Cellular) is used in Japan.
TDMA is a narrow band of 30 KHz wide and 6.7 millisecond long. It is divided into three slots of time. Using the CODEC, stands for Compression / Decompression algorithm, compresses the digital information and use less space leaving for the other users. Division of this narrow band into three time slots increases the capacity of frequency band. TDMA supports both frequency bands IS-54 and IS-136. GSM (TDMA) is a different standard and provide basis for IDEN and PCS. Being an international standard, it covers many countries of the world. There is only the need for changing the SIM and you can get connected no need to buy a new phone. Having two different bands
- 900-1800 MHz band covers Europe and Asia
- 850-1900 MHz band covers United State
First band is in sync widely but second is limited to the United State. It is better to go for the first one if you need to go on extensive travelling.
How 2G (CDMA) Works
Contrary to TDMA, CDMA works in a singular way. Like TDMA, It also converts the information into digital data and sends it. Now the information is extended upon the bandwidth. Incoming calls are spread over the surface of the channel and a code is allocated to them. As the data is spread over the surface of channel it is known as spread spectrum. It compresses the data into small packets and sends it to a separate frequency columns.
Every caller sends out data to a similar spectrum. Every caller’s signals are spread over the channel having a unique code. Reaching at the receiving point, codes are to be matched and hence data delivers. CDMA refers to the GPS standard for marking the time stamp on the broadcast signals. CDMA supports Interim Standard (IS-95) and operational at the frequency bands of 800 MHz and 1900 MHz.