1G, 2G

1G Mobile 

1G refers to the first generation of wireless cellular technology (mobile Telecommunications ). These are the analog telecommunication standards that were introduced in the 1980s.Audio transmissions on 1G Networks  were analog. 

1G is only modulate at higher frequencies  typically 150 MHz and up.

 1G: Voice only

 However, cell phones were introduced in the 1980's through 1G technology.  1G is the first generation of wireless cellular technology.  1G only supports voice calls.

1G is an analog technology, and the phones that used it had poor battery life and voice quality, poor security, and a tendency to drop calls.

2G Mobile 

2G is short for second generation cellular networks.  The 2G cellular network was launched commercially in 1991. [1]

  The 2G network had three primary advantages:

1. Digitally encrypted phone conversations, at least between mobile phones and cellular base stations but not necessarily on the rest of the network.

 2. Significantly more efficient use of the radio frequency spectrum enables more users in each frequency band.

 3. Data service for mobile, starting with SMS text message

Radio signals on 2G networks are digital.

 With General Packet Radio Service (GPRS), 2G 40 Kbit  / s (5 kB / s) provides a theoretical maximum transfer speed.  With EDGE (Extended Data Rate for GSM Evolution), 384 kbit / s (48 kB / s) is the theoretical maximum transfer speed.

The most common 2G technology was Time-Division Multiple Access (TDM) -based GSM , originally from Europe but used mostly in the world outside of Japan and North America.  In North America, digital AMPS (IS-54 and IS-136) and cdmaOne (IS-95) were the main systems.  In Japan, the ubiquitous system was the personal digital cellular.