Modern wireless communication systems was marked by intervention of telegraph in 18 century. In 1876 scientist Thomas Edison invented telephone known as Public Switched Telephone Network (PSTN) which was established in Western countries.
From that moment new techniques was introduced to improve the quality of telecommunication services such as Modulation, Demodulation and Cellular concepts.
In aspect of wireless technology we have various generation;
The 1G mobile cellular system was analog speech communication system. 1G have the following technologies;
In 1G were analog signals / analog systems, they cannot cover the long distance. 1G uses FDMA (Frequency Division Multiple Access) technique.
2G is a digital technology and its signal uses digital signal, which means they convert analog signal to digital signal and digital signal to analog signal. Digital signal can cover long distance. 2G cellular system were deployed to overcome 1G limitations. In 2G new access techniques were introduced like TDMA (Time Division Multiple Access) and CDMA (Code Division Multiple Access).
2G support Voice and Data signals.
2G have the following technologies;
2.5G: Second Generation Networks
2.5G was original from the ideas of 2 G, 2.5 G this technology also called GPRS (General Packet radio Service). 2.5 G modifying the air interface so that it could handle data as well as voice. The data rate in GPRS (2.5 G) is very less. Data rate for GPRS 56 Kbps to 64 Kbps.
2.75G: Second Generation Networks
With the low data rate in 2.5 G that leads to move into 2.75 G generation. 2.75 G also known as EDGE (Enhanced Data Rates for GSM Evolution). Data rate for EDGE 170 Kbps.
3G also called UMTS (Universal Mobile Telecommunication System) with a data rate of 384 Kbps. 3 G introduces video calling because of its high data rate.
3G support Voice, Data and Video Signals.
Have high data rate with 1 Gbps for stationary users (for low mobility or pedestrian speeds or fixed) and 100 Mbps for high mobility users. Key technologies for 4G are;
4G, have high speed and IP based.
5G is official commercial in 2020 with high data rate about 5 Gbps.