Second generation (2G) mobile phones switched from analog system of 1G to digital system. It was commercially launched in 1991 as GSM standard in Finland. As with 1G phones, 2G phones didn’t have any worldwide standardizations. 2G systems were also known as personal communications services (PCM).
It allows voice signals to be digitized and compressed. So, they are more efficient on frequency spectrum than 1G.
They introduced data services for mobile in form of SMS text messaging.
Data and voice signals are digitally encrypted. So, security against eavesdropping and fraud increased manifold.
Digital signals consume less battery power. And so mobile sets are much more energy efficient than their 1G counterparts.
Several 2G systems were developed, the notable among which are as follows −
D – AMPS (Digital Advanced Mobile Phone Systems) : D-AMPS was a digital version of advanced mobile phone systems (AMPS) that coexisted with AMPS. It used time division multiplexing (TDM) for multiple calls.
GSM (Global System for Mobile Communications) : 2G was launched through GSM. It is the most widely globally used technology. It uses frequency division multiplexing (FDM) and time division multiplexing (TDM) for handling multiple calls simultaneously.
CDMA (Code Division Multiple Access) : It uses a different technology from the above and was standardized by International Standards IS-95.