EVOLUTIONS OF WIRELESS SYSTEMS

First generation: Almost all of the systems from this generation were analog systems where voice was considered to be the main traffic. These systems could often be listened to by third parties. Some of the standards are NMT, AMPS, Hicap, CDPD, Mobitex, DataTac, TACS and ETACS.

Second generation: All the standards belonging to this generation are commercial centric and they are digital in form. Around 60% of the current market is dominated by European standards. The second generation standards are GSM, iDEN, D-AMPS, IS-95, PDC, CSD, PHS, GPRS, HSCSD, and WiDEN.

Third generation: To meet the growing demands in network capacity, rates required for high speed data transfer and multimedia applications, 3G standards started evolving. The systems in this standard are essentially a linear enhancement of 2G systems. They are based on two parallel backbone infrastructures, one consisting of circuit switched nodes, and one of packet oriented nodes. The ITU defines a specific set of air interface technologies as third generation, as part of the IMT-2000 initiative. Currently, transition is happening from 2G to 3G systems. As a part of this transition, numerous technologies are being standardized.

* 2.75G:
o EDGE.
o EGPRS.
* 3G:
o CDMA 2000.
o W-CDMA or UMTS(3GSM).
o FOMA.
o 1xEV-DO/IS-856.
o TD-SCDMA.
o GAN/UMA.
* 3.5G:
o HSDPA.
o HSUPA.
* Post 3G:
o HSOPA/LTE.

Fourth generation: According to the 4G working groups, the infrastructure and the terminals of 4G will have almost all the standards from 2G to 4G implemented. Although legacy systems are in place to adopt existing users, the infrastructure for 4G will be only packet-based (all-IP). Some proposals suggest having an open platform where the new innovations and evolutions can fit. The technologies which are being considered as pre-4G are the following: WiMax, WiBro, iBurst, 3GPP Long Term Evolution and 3GPP2 Ultra Mobile Broadband.