2G

2G refers to the second generation of cellular mobile technology, deployed from the early 1990s onward as a wholesale replacement for analog 1G networks. The jump from 1G to 2G was a shift to digital modulation and transmission, which brought dramatic improvements in spectral efficiency, call quality, and the ability to carry data alongside voice. The major 2G standards included GSM (Global System for Mobile Communications), which became dominant in Europe and much of Asia; TDMA (Time Division Multiple Access) and its variant iDEN, which saw use in North America; PDC (Personal Digital Cellular), the standard in Japan; and CDMA variants. Each operated on different frequency bands and used different air-interface protocols, though all shared the fundamental principle of digitizing the signal at the handset.

GSM, by far the most widely deployed 2G system, used time-division multiplexing to assign each user a narrow time slot within a radio channel, typically 200 kHz wide. A single GSM channel could support up to eight simultaneous calls. Data transmission on 2G networks was initially limited to short bursts; GPRS (General Packet Radio Service) and later EDGE (Enhanced Data Rates for GSM Evolution) extended 2G's usefulness into the early mobile internet era by allowing packet-switched data at speeds around 56 to 236 kbps, enough for email and basic web access on phones with small screens.

Why the shift mattered

The move to 2G solved several acute problems. Analog 1G networks consumed far more spectrum for the same number of calls and offered no encryption; conversations were vulnerable to casual eavesdropping with a scanner. Digital 2G networks incorporated SIM cards (Subscriber Identity Modules), which stored the user's identity and authentication data separately from the handset, making the system more secure and allowing subscribers to change phones easily. The handsets themselves could be far simpler; a 1G phone needed complex analog circuitry, while 2G phones used digital processors and could rely on software to handle many functions.

By the late 2000s, 2G networks were being phased out in developed markets as carriers transitioned to 3G and 4G. However, the long tail of 2G deployment meant many regions retained functioning GSM networks well into the 2010s and beyond. The simplicity and low power consumption of 2G also made it useful for machine-to-machine communication and IoT devices that did not require high throughput. Most carriers in North America and Europe have now shut down 2G service entirely, though some 2G infrastructure remains operational in developing regions.