The First Generation of communication system is the Analog cellular system, means carrier is Analog. we just send wave forms primarily with voice. it is continuous in amplitude and time. variation in a signal disrupts over long distance . This Analog system was introduced in seventies.NMT , AMPS, TACS, CDPD technologies were used in 1G. It uses FDMA technique call to one country. All the Analog systems were used circuit switched technology and design only for voice communication not data. The cost for the system and voice transfer is also high in 1G.Problems with 1G is poor voice quality , less battery life , no security , the phone size is big and frequent call drops.
second generation is digital cellular in this started sending 1's and 0's with the air. it is circuit switched and narrowband technology. It is low band digital cellular signaling system. Digital is more spectrally efficient it uses technologies like TDMA ,GSM,CDMA, iDEN , PDC, PHS.It uses digital modulation for better audio quality. GSM technology has both FDMA and TDMA techniques. An estimated GSM system users all over the world is 248 millions now and it is currently using in 140 countries.
In addition to this , PDC(Personal Digital Communication) technology based on TDMA is introduced. After this CDMA technology was introduced , it divide speech into small segments and encoded to identify the calls by using spread spectrum. While GSM and TDMA systems are most important in 2G wireless technology, the CDMA technology proved that it gives better voice quality, low noise, few call drops , good security, and high network capacity. Data transmission, fax , messages up to 9.6 kbps is capable by 2G , but not acceptable for multimedia and web browsing applications.
Internet usage has been increased from past few years and demand for advanced wireless data services are triggered. The data rates of 2G wireless system is slow for today's internet servers. So, the other carriers developed 2G+ technology with increased data rates up to 348 kbps.
These 2G+ systems are using one of the technique from below
1.HSCSD(High Speed Circuit Switched Data).
2. GPRS(General Packet Radio Service).
3. EDGE(Enhanced Data Rates for Global Evaluation).
HSCSD is one further step to 3G technology networks. wireless service providers are upgraded the 2G networks to 2.5 networks because of the subscribers demand and the 2G architecture remains same to give better voice and data applications.
Many users will not wait until the final 3G...