Rel-4 (EDGE) / GSM pre-3GPP · IMT - not formally classified
2G
GSM / GPRS / EDGE
The network that gave the world SMS.
2G replaced analogue 1G with digital transmission, which meant clearer calls, basic encryption, and - almost as an afterthought - SMS, tucked onto a signalling channel that was never meant to carry consumer traffic. It became one of the most lucrative accidents in telecoms history. Later extensions, GPRS and EDGE, bolted on packet data so phones could limp through WAP pages and early email, but speeds stayed in the kilobits: a single photo could take minutes to send. Decades on, 2G radios are still running quietly in the background of alarm systems, payment terminals, and fallback voice calls.
Key Metrics
Key Innovations
Replaced analogue AM/FM voice with digital TDMA encoding - cleaner audio, better spectrum efficiency, and basic encryption.
Short Message Service: 160-character text messages sent over the GSM signalling channel. Became one of the highest-revenue mobile services ever.
General Packet Radio Service introduced always-on packet data. Allowed IP-based data alongside voice, enabling WAP and basic internet access.
Enhanced Data rates for GSM Evolution introduced 8PSK modulation, tripling GPRS throughput to a theoretical 384 Kbps.
Subscriber Identity Module - portable credentials enabling network authentication and portability across devices.
Use Case Support
SMS was invented for GSM. 160 characters over signalling channel - works perfectly.
WAP and GPRS enabled basic web access but pages were designed specifically for the constraints. Real websites were unusable.
Max 384 Kbps vs 5 Mbps required. Even a compressed 360p stream was impossible reliably.
Two orders of magnitude below what 4K requires.
600ms latency vs 20ms required. Even ignoring bandwidth, this fails on latency alone.
GSM was designed for voice; device density per cell was measured in hundreds, not millions.
Requires >100 Mbps and <10ms. 2G provides 0.1 Mbps at 600ms.
Sub-1ms latency is a 600x improvement from 2G's best case.
Architecture
GSM Network Architecture
Circuit-switched voice core with a separate GPRS packet-switched overlay. The Base Station Subsystem (BSS) connects handsets to the core via BTS and BSC.
See the full diagram catalogue on the Architecture page.