3G : UMTS/HSPA/HSPA+
3G brought mobile internet to the mainstream. Where 2G was built for voice and SMS, 3G (UMTS, then HSPA/HSPA+) switched to WCDMA on the air interface and pushed data rates from tens of kbps into the multi-Mbps range — enough for video calls, web browsing and the first smartphone apps.
Key points:
Air interface: WCDMA (wideband CDMA), later HSPA/HSPA+ for faster data
Typical data speeds: 384 kbps → 42 Mbps (HSPA+)
Stronger authentication than 2G (mutual auth, USIM) — no trivial A5/1-style break
Being shut down worldwide in favour of 4G/5G, but still instructive to study