Before discussing about telecom technologies, at first we should be aware of the term ‘’telecommunication”, it is said to be as sending some sort of information over particular distance. As we know in earlier times telecommunication was only possible via visual signals like smoke signals, signal flags, loud whistles etc. Nowadays telecommunication means the use of radio or microwave communication apart from telegraph, telephone, teleprinter etc. Again a telecommunication basically comprises of three units namely-transmitter, medium, receiver. Generations of cellular networks are 1G, 2G, 3G, and 4G.
1G (First Generation System) was based on analogue technology. It uses the FDMA technique for making communication.
It was also known as Digital Cellular System. 2G technologies mainly compromises of GSM, IS-95, IS-136.Of which GSM based on TDMA technique,IS-95 based on CDMA technique & IS-136 better known as D-AMPS based again on TDMA technique. This technology brings two basic terms like voice services & slow data transmission. Providing data rates up to 236.8 kbps. Same in case of CDMA One evolve to CDMA2000 1x or 1xRTT proving both voice & data communication at a good data rate of around 60-100 kbps compared to almost 14.4 kbps in case of CDMA One. Slowly but steadily we are heading towards the high data rate system also known to be as 3G (Third Generation System).
Already 2.5G systems were introduced to facilitate the need of high data rate consumption, but it was not enough. Soon individuals demands for separate packet data rather than circuit switched data. Moving towards 3G it is a part of IMT-2000 providing some new services like video calls, mobile TV, mobile internet, voice calls, etc. Again new license was to be obtained for new frequency spectrum & the equipments were quite different, so a whole new set up was required. Under the 3G CDMA 2000 EV-DO Release 0 was also introduced. This technology was using both CDMA & TDM technique. Its aim was to achieve more than 2 Mbps data rates. After that same like that of 2G, 3G was evolved into 3.5G also known as HSPA comes under UMTS system which was combination of HSDPA (High Speed Downlink Packet Access) & HSUPA (High Speed Uplink Packet Access).Here the data rates almost reach up to 14 Mbps as downlink & 5 Mbps as uplink.
4G offers around 100 Mbps. 4G uses the term either LTE or Wimax, but all are using same modulation technique i.e., OFDM. Right now this 4G has evolved to 4G Advanced in some countries & offering the data rates of around 1Gbps.
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