Rel-8 (LTE) through Rel-13 (LTE-A Pro) · IMT-Advanced
4G
LTE / LTE-Advanced
All-IP. The generation that made smartphones indispensable.
4G LTE was an architectural clean break — a fully all-IP network with no circuit-switched domain. It introduced OFDMA and MIMO, pushing peak speeds to 1 Gbps in LTE-Advanced. This generation powered the app economy, HD/4K streaming, ride-hailing, social media, and on-demand everything.
Key Metrics
Key Innovations
Orthogonal Frequency Division Multiple Access divides the channel into hundreds of orthogonal subcarriers, enabling highly efficient multi-user scheduling and resistance to multipath interference.
Multiple Input Multiple Output uses multiple antennas at both base station and device to multiply throughput via spatial multiplexing — without using extra spectrum.
The Evolved Packet Core eliminated the circuit-switched domain entirely. Voice became VoLTE (Voice over LTE) — a data service, not a legacy circuit call.
LTE-Advanced (Rel-10) introduced carrier aggregation — bonding up to 5 separate spectrum blocks to multiply peak throughput.
Voice over LTE delivers HD voice calls as IP packets over the LTE data plane, achieving better audio quality and faster call setup than legacy CS voice.
Enhanced Inter-Cell Interference Coordination enabled heterogeneous networks of macro cells, small cells, and femtocells to coexist — dramatically increasing capacity.
Use Case Support
SMS continues to work via SMS-over-IP or legacy CSFB (Circuit-Switched Fallback).
30+ Mbps and 50ms latency makes mobile web indistinguishable from broadband for most browsing.
4G's 30 Mbps realistic speeds easily support 1080p streaming.
LTE-Advanced can support 4K, though consistency depends on network load.
50ms latency is technically above the 20ms threshold. Some cloud gaming works on 4G but input lag is noticeable in fast-paced games.
NB-IoT was added to LTE in Rel-13 as an overlay, but density and power efficiency fall short of 5G mMTC targets.
100 Mbps sustained and 10ms latency both exceed reliable 4G capabilities — especially in congested areas.
1ms ultra-reliability is a fundamental architecture requirement, not achievable with LTE's EPC design.
Architecture
4G EPC (Evolved Packet Core)
Flat, all-IP architecture. The EPC separates the control plane (MME) from the user plane (SGW/PGW). No circuit-switched domain — voice runs as VoLTE over the data plane.
See the full interactive diagram on the Architecture page.
What Changed from 3G
OFDMA's subcarrier structure dramatically improves spectral efficiency and multi-user scheduling vs CDMA.
No more circuit-switched domain. Everything — including voice (VoLTE) — runs over IP.
Multiple antenna streams multiply throughput without consuming extra spectrum.
Radio resource management moved into the base station, flattening the RAN architecture and reducing latency.
Bonding multiple spectrum blocks to reach Gbps peak rates.