Why is the original LTE called "3.9G" rather than true 4G, and what headline figures came with it in 2009?
When LTE was introduced in 2009 it fell just short of the ITU's official 4G (IMT-Advanced) bar, so it was labelled "3.9G": its minimum peak rates were 100 Mbit/s downlink and 50 Mbit/s uplink, with sub-10 ms ping latency and support for cell sizes from 1 km to 100 km.
The "3.9G" label:
The ITU defines what may officially be called "4G" through its IMT-Advanced requirements (notably 1 Gbit/s peak for low mobility). The first LTE release was a huge leap over 3G but didn't quite clear that bar, so it sits between 3G and 4G — hence 3.9G. Only LTE Advanced (Release 10+) met IMT-Advanced and became "real" 4G. Marketing called both "4G" anyway.
LTE (2009) headline figures:
| Property | Figure |
|---|---|
| Peak downlink (minimum) | ≥ 100 Mbit/s |
| Peak uplink (minimum) | ≥ 50 Mbit/s |
| Peak downlink with 4x4 MIMO | up to 326 Mbps |
| Ping (round-trip latency) | < 10 ms |
| Supported cell size | 1 km – 100 km |
Other defining traits: new transmission scheme OFDMA, adaptive antenna systems (MIMO), standardized by 3GPP, and coexistence with legacy standards (GSM/UMTS) so operators could run old and new side by side.
Tip: The huge 1 km–100 km cell-size range is what lets LTE serve both dense cities (small cells) and rural areas (one tower covering vast distances) with the same standard.
Go deeper:
LTE Advanced (Wikipedia) — why first-release LTE missed the ITU IMT-Advanced bar and only LTE-A earned the official "4G" name.- E-UTRA (Wikipedia) — the air-interface spec behind the headline numbers: OFDMA/SC-FDMA, MIMO peak rates, low latency.