VoLTE Standards and Regulatory
3GPP specifications
VoLTE is built on a stack of 3GPP (3rd Generation Partnership Project) specifications. The key documents are:
| Specification | Title | VoLTE relevance |
|---|---|---|
| TS 22.173 | IMS Multimedia Telephony service and supplementary services | Service requirements for IMS voice |
| TS 23.228 | IP Multimedia Subsystem (IMS) stage 2 | IMS architecture – the foundation document |
| TS 24.229 | IP multimedia call control protocol based on SIP and SDP | SIP/SDP procedures for VoLTE call setup |
| TS 24.301 | Non-Access-Stratum (NAS) protocol for Evolved Packet System | EPS bearer management including QCI 1 bearer setup |
| TS 26.114 | IMS conversational video and voice; media handling and interaction | AMR-WB codec use in VoLTE, jitter buffer requirements |
| TS 26.441 | Codec for Enhanced Voice Services (EVS) | EVS codec used in VoNR and some VoLTE implementations |
| TS 36.331 | E-UTRA Radio Resource Control | LTE RRC procedures including dedicated bearer setup for VoLTE |
GSMA specifications
The GSMA (GSM Association) produces implementation profiles that ensure interoperability between operators. For VoLTE, the key document is:
| Specification | Title | Purpose |
|---|---|---|
| IR.92 | IMS Profile for Voice and SMS | The mandatory VoLTE interoperability profile. Defines exactly which 3GPP features operators must implement for handsets and networks to interwork. The most important VoLTE standard after 3GPP TS 23.228. |
| IR.94 | IMS Profile for Conversational Video Service | VT (video telephony) interoperability profile for VoLTE video calls |
| IR.51 | IMS Profile for Wi-Fi Calling | VoWiFi interoperability, same IMS as VoLTE |
| IR.92 Annex B | Device requirements | Specific requirements for handsets claiming VoLTE compliance |
UK regulatory context
Ofcom
Ofcom regulates UK telecommunications. Its Communications Market Report tracks VoLTE adoption, call quality metrics, and network performance. Ofcom has monitored the impact of the 3G switch-off on consumers and business users and has published guidance on the PSTN migration.
BT Openreach PSTN migration
Openreach’s Digital Voice programme is the industry-wide programme to migrate the UK’s telephone infrastructure from the PSTN to IP-based delivery. The January 2027 closure date affects all analogue lines. Openreach has published guidance for housing associations, businesses, and equipment manufacturers on the migration path.
BS EN 81-28:2018
Safety rules for the construction and installation of lifts – Rescue of persons in stalled lifts. Requires a two-way communication system in every lift car capable of contacting a rescue service. This standard is the primary driver for VoLTE adoption in lift installations replacing PSTN emergency phones.
Building Regulations Approved Document B
Fire safety requirements relevant to alarm communicators. Grade D fire systems may use voice communicators; these must be reviewed against the PSTN closure timeline.
PD 6662:2017 and BS 8243:2021
UK standards for intruder alarm systems design. Systems using PSTN-connected diallers for ARC signalling must be reviewed against the 2027 deadline. BS 8243:2021 covers the use of cellular transmission paths for alarm signalling.