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 (24.25–71 GHz, defined by 3GPP as FR2) 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 service family targeting low latency and high reliability for industrial automation and other demanding applications. Actual end-to-end performance depends on deployment; a radio target alone does not make medical or safety-critical applications suitable.
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. This conceptual diagram combines ideas from current research proposals: a distributed, AI-native, cloud-native design that could integrate sensing, non-terrestrial layers, and network digital twins.
The main candidate for new 6G capacity is the upper mid-band (roughly 7–15 GHz), under study for WRC-27, which balances bandwidth with wide-area coverage. Some research also explores sub-THz bands for very wide channels, though these face severe propagation constraints. A 6G spectrum plan has not been standardised.
Research explores using machine learning for tasks such as channel estimation, beam management, and network optimisation. The role of AI in future radio standards remains under study.
ISAC research investigates whether communication signals can also support sensing functions such as positioning or environmental awareness. Performance, privacy, and deployment limits remain open questions.
Some 6G research explores sub-millisecond radio-interface targets. End-to-end latency and reliability depend on the full system and application; these targets do not guarantee suitability for safety-critical or medical use.
Researchers study future immersive media that could need much higher data rates and lower latency. Holographic communication remains a concept with unresolved requirements and no 6G service guarantee.
Studies explore closer integration of satellite, high-altitude platform, and terrestrial networks. Such integration could extend connectivity, but coverage depends on system design, capacity, spectrum, regulation, and economics.