1G, 2G, 3G, and 4G Cellular Wireless Standards
By Stephen Bucaro
The meaning of the terms 3G and 4G have been made very confusing because some wireless carriers
like Sprint and Verizon have built new high-speed 4G networks from the ground up while other wireless
carriers (AT & T and T-Mobile) have chosen to doctor-up their 3G service and market it as 4G.
The original cellular wireless, introduced in the 1980s, (now referred to 1G for 1st Generation) was
entirely analog, It worked by modulating a frequency of 150 MHz. 2G cellular networks were launched
in Finland in 1991, based on the Global System for Mobile Communications (GSM) standard. The difference
between 1G and 2G is that with 2G the voice signal is digital and is encrypted.
GSM networks operate in the 900 MHz or 1800 MHz bands. Where these bands were already allocated,
(for example in Canada and the United States) the 850 MHz and 1900 MHz bands were used instead.
With GSM the frequency is divided into timeslots for individual phones to use. These eight timeslots
are grouped into a Time division multiple access (TDMA) frame. This allows eight full-rate or sixteen
half-rate speech channels per frequency.
3G uses the International Mobile Telecommunications-2000 (IMT-2000) specifications set by the
International Telecommunication Union (ITU). To meet the IMT-2000 standards, a system is required
to provide peak data rates of at least 200 Kbit⁄s.
4G uses the IMT-Advanced specification set by the ITU in 2008. To meet the IMT-Advanced standards,
a system is required to provide peak data rates of up to 1 Gbit⁄s. The new standard also uses Internet
protocol (IP) and the orthogonal frequency-division multiplexing (OFDM) to jam more data into the
frequency. True 4G networks are referred to as Long Term Evolution (LTE) networks.
The wireless carriers that have chosen to doctor-up their 3G service rather than built new high-speed
4G networks, use technologies such as High Speed Packet Access (HSPA) and WiMax (Originally designed
as a wireless home broadband service) to beef up their 3G networks. They then market this as "4G".
The current versions of these technologies do not meet the IMT-Advanced specification requirement
of data rates up to 1 Gbit⁄s for 4G systems.
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