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of the signal at the receiving end decreases even if there are no obstacles in the way. Second, as the
electromagnetic waves are propagated through air, a signal travelling from a transmitter may take
alternative paths on its way to the receiver. These paths may cause delays in the received signal due
to the extra distance travelled.

CTM: Wireless in local loop is a system that is similar to telephone system which provides wireless
telecommunication by deploying a multiplicity of multichannel transceivers.

8.15 MOBILE TELECOMMUNICATION TECHNOLOGIES—1G, 2G, 3G & 4G

 1G Technology

1G technology was used in the first mobile phones. 1G was introduced in the 1980’s.
Transmission of voice data took place through analog radio signals. 1G network was used for
voice calls and not for transmitting text messages. For example, NMT, C-Nets, AMPS, TACS.
Salient features of 1G technology:
• It provides data rates up to 2.4 kbps.

• It uses analog signals.
• Voice quality is not very good.

• It does not support transmission of text messages.
• It does not provide security.

 2G Technology

2G technology is the first digital cellular system that was launched in the early 1990’s that
provides high data transmission rate in digital format. 2G also introduced data services for
mobiles, starting with SMS. For example, D-AMPS, GSM/GPRS, CDMAOne.
Salient features of 2G technology:

• Good quality of sound.
• Higher data rates up to 64 kbps.

• Improved security mechanism.
• Transmission of data such as text messages in digital format.
• Support transfer of picture messages and MMS.

• It does not support transfer of complex data such as videos.
• It allows multiple users per radio channel with each user talking one at a time.
 3G Technology
Computer Science with Python–XII 8.36 3G technology was introduced in the year 2000 and provides much higher data rates with
• Digital transmissions enable compressed voice and multiplexing multiple users per channel.

speed from 144kbps to 2mbps.

3G technology has introduced more efficient ways of carrying data, making it possible to have
faster web services, live chat, fast downloading, videoconferencing, etc., over mobile phones.
For example, CDMA2000/EV-DO,WCDMA/HSPA+,TD-SCDMA.