2G or second generation

2G or second-generation wireless technologies saw their first commercial light of day on the GSM standard. GSM stands for global system for mobile communications.In the world of cell phones, 2G signifies second-generation wireless digital technology. Fully digital 2G networks replaced analog 1G, which originated in the 1980s.2G on GSM standards were first used in commercial practice in 1991 by Radiolinja, which was a Finnish GSM operator founded on Sept 19,1988.The main differentiator to previous mobile telephone systems, retroactively dubbed 1G, is that the radio signals that 1G networks use are analog, while 2G networks are digital. Note that both systems use digital signalling to connect the radio towers (which listen to the handsets) to the rest of the telephone system.

FLAVOURS OF 2G

2G technologies can be divided into TDMA-based standard and CDMA-based standard depending on the type of multiplexing used. The main 2G standards are:

• GSM (TDMA-based), originally from Europe but used worldwide
• iDEN (TDMA-based), proprietary network used in the United States and in Canada
• IS-136 aka D-AMPS, (TDMA-based, commonly referred as simply TDMA in the US), used in the Americas
• IS-95 aka cdmaOne, (CDMA-based, commonly referred as simply CDMA in the US), used in the Americas and parts of Asia
• PDC (TDMA-based), used exclusively in Japan

Capacity

Using digital signals between the handsets and the towers increases system capacity in two key ways:

• Digital voice data can be compressed and multiplexed much more effectively than analog voice encodings through the use of various CODECs, allowing more calls to be packed into the same amount of radio bandwidth.
• The digital systems were designed to emit less radio power from the handsets. This meant that cells could be smaller, so more cells could be placed in the same amount of space. This was also made possible by cell towers and related equipment getting less expensive.