Network Architecture
How each generation is built
Every mobile generation restructures the network core to meet new performance targets - from GSM's circuit-switched voice core to 5G's microservice-based architecture. Select a generation to see its components and how data flows between them.
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.
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.
UMTS Network Architecture
UTRAN (UMTS Terrestrial Radio Access Network) connects Node Bs via Radio Network Controllers to a split core: CS domain for voice, PS domain for data.
Wideband Code Division Multiple Access replaced TDMA with spread-spectrum CDMA, enabling the same spectrum to serve more users simultaneously with better interference management.
High Speed Downlink/Uplink Packet Access - adaptive modulation and fast retransmission (HARQ) dramatically improved throughput by adapting to channel quality in real time.
Introduced a framework for delivering voice and multimedia over IP, laying the groundwork for VoLTE in 4G.
3G's circuit-switched video calls (CS video) enabled the first mainstream mobile video calls via the CS domain.
3G data speeds made downloading apps viable, directly enabling the App Store (2008) and Google Play ecosystem.
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.
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.
5G Core - Service-Based Architecture
Decomposed microservice architecture where every function exposes an HTTP/2 API. The control and user planes are fully separated (CUPS). The NRF enables service discovery across all functions.
The 5G Core replaces monolithic EPC nodes with microservices (AMF, SMF, UPF, NRF, PCF…) that communicate via HTTP/2 REST APIs. Each service can be independently scaled and deployed.
A single physical 5G infrastructure can be partitioned into multiple isolated virtual networks (slices), each with different QoS profiles - one slice for enhanced mobile broadband, another for ultra-low latency URLLC.
5G base stations (gNodeBs) use 64–256 antenna elements to form precise beams directed at individual users, dramatically improving spectral efficiency and range - especially in mmWave.
5G opened millimetre-wave spectrum (24–100 GHz) for the first time in mobile networks. Extreme bandwidth (hundreds of MHz per carrier) enables multi-Gbps throughput - at the cost of range and penetration.
A dedicated service family designed for 1ms latency and 99.9999% reliability. Enables remote surgery, autonomous vehicles, and industrial automation.
Designed to connect 1 million devices per km² at ultra-low power. The foundation for smart cities, precision agriculture, and industrial IoT at scale.
6G - AI-Native Distributed Architecture (Conceptual)
6G architecture is not yet standardised. Research consensus describes a distributed, AI-native, cloud-native architecture with integrated sensing, non-terrestrial layers, and semantic communication.
6G research targets 0.1–10 THz bands, offering hundreds of GHz of contiguous bandwidth per carrier - enabling theoretical peak rates of 1 Tbps. Range is sub-100m; primarily indoor and dense urban.
Unlike 5G where AI is an add-on optimisation layer, 6G embeds machine learning directly into the air interface - channel estimation, beam management, and waveform selection are all ML-driven.
6G base stations simultaneously communicate and sense their environment - acting as distributed radar. Enables centimetre-precision positioning and environment mapping using the communication signal itself.
Extended ultra-reliability targets: 0.1ms over-the-air latency and up to 99.99999% (seven nines) reliability - enabling full remote surgery and safety-critical industrial automation.
Multi-dimensional holographic video transmission requires Tbps throughput and <1ms latency simultaneously - only feasible with 6G's combined improvements.
6G formally integrates LEO satellite, HAPS (high-altitude platform stations), and terrestrial networks into a unified access layer - true global coverage including oceans and polar regions.