Q.List the additional features of 3G and 4G cell phone systems.

Cellular telephony has evolved through several generations, each adding capability. The first system, AMPS (Advanced Mobile Phone System), was developed in the 1970s and put into service in the early 1980s using analog techniques. Analog AMPS has since been replaced by digital systems — 2G, 2.5G, 3G and 4G.

Moving from analog to digital brought three major advantages: the available frequency spectrum is used to the maximum through multiplexing, so many more users can share the same band; digital transmission is far more reliable in noisy environments, because the signal can be cleanly regenerated; and handsets can be made more compact while offering many more features.

Second-generation (2G) digital systems are built on three basic technologies: GSM (Global System for Mobile communication), IS-136 or TDMA (Time Division Multiple Access), and CDMA (Code Division Multiple Access). Later 3G and 4G systems turned the phone from a voice-only device into a multipurpose personal terminal by adding features such as colour LCD screens, digital cameras, e-mail, games, GPS, internet access, Bluetooth, push-to-talk, voice recognition and video conferencing.

Understanding this progression explains why modern phones handle high-speed data, streaming and multimedia in addition to calls, and why efficient use of the shared radio spectrum has been the driving concern at every step. The generation labels (2G, 3G, 4G) are simply a shorthand for steadily higher data rates and richer services.