History of Mobile Voice in the UK

The UK’s first mobile network used TACS (Total Access Communication System), an analogue standard based on the US AMPS system. Launched by Cellnet (now EE/BT) and Vodafone in 1985. Voice was carried as an analogue FM signal on 900 MHz spectrum. No encryption. Calls could be intercepted with a scanner. Quality degraded at cell edges. No data capability. Peak UK TACS subscribers around 4 million. Networks closed by 2000.

GSM (Global System for Mobile Communications) launched in the UK in 1992 on 900 MHz. Voice was now digital, using the RPE-LTP codec initially (13 kbps), later replaced by the AMR-NB (Adaptive Multi-Rate Narrowband) codec in 1999. AMR-NB operates at 4.75 to 12.2 kbps and captures 300 Hz to 3,400 Hz – the classic “telephone voice” quality. GSM introduced SIM cards, SMS, and basic data (GPRS from 1999, EDGE from 2003). The 900 MHz and 1800 MHz bands gave good building penetration. All four UK operators have confirmed 2G will eventually close, though no UK date is confirmed as of 2025.

3G UMTS (Universal Mobile Telecommunications System) launched in the UK from 2003 using 2100 MHz spectrum. Voice used circuit-switched bearers with the same AMR-NB codec as 2G – so call quality did not improve for standard voice calls. 3G’s contribution to voice was video telephony (H.324M), which allowed face-to-face video calls before smartphones made OTT apps the default. HSPA/HSDPA (from 2005) delivered mobile broadband speeds. All UK 3G networks closed in 2024: Vodafone (January), Three (August), EE (October), O2 (December).

4G LTE launched in the UK in 2012 (EE first, then others). LTE is a data-only network – it carries no circuit-switched voice. Early 4G phones used Circuit Switch Fallback (CSFB) to drop to 3G for calls. VoLTE launched on EE in 2015, Vodafone and O2 in 2016, Three from 2016 onwards. VoLTE carries voice over the LTE data bearer using the IMS (IP Multimedia Subsystem) and the AMR-WB (HD Voice) codec – capturing 50 Hz to 7,000 Hz. Call setup dropped from 6-8 seconds (CSFB) to under 2 seconds. Data connection stays active during calls. VoLTE SIMs require ISIM credentials. Full VoLTE technical reference: voltesim.co.uk.

EE launched 5G in the UK in May 2019. The initial 5G rollout used Non-Standalone (NSA) architecture – the 5G NR radio delivers additional data capacity, but the core network is still 4G EPC and voice calls use VoLTE. Most consumers on a 5G phone in the UK today are still using VoLTE for voice calls, not VoNR. The “5G” indicator refers to the data bearer, not the voice mechanism.

5G Standalone (SA) networks began deploying in the UK from 2023 onwards. 5G SA uses the 5G Core (5GC) end-to-end, enabling true VoNR – voice calls over the 5G NR air interface with the EVS codec and up to 20 kHz fullband audio. UK operator 5G SA availability is expanding, but consumer VoNR remains limited as coverage builds. Enterprise VoNR via network slicing is an earlier commercial use case. This is the beginning of the VoNR era, not the peak.