Assured Voice Communication

In Release 15, the AVC (Assured Voice Communication) function was introduced with a specific correction to its colour parameters for visual presentation. This function is part of the broader critical communications framework, which leverages network slicing and QoS controls to provide reliable, priority voice services for scenarios like natural disasters. The enhancement ensures AVC meets the stringent requirements for essential services within 5G networks.

• Correction on AVC Colour Parameters TS 26.116CR0012

In Release 16, the AVC function introduced new capabilities for handling voice in critical scenarios, including support for originating MMTEL voice calls even when a general back-off timer (T3346) is running. It also defined a specific mobile-terminated voice gap procedure for Multimedia Priority Service (MPS) users to ensure their calls are not missed during network access control states.

• Support of time sensitive communication TS 24.501CR1466
• Release of NAS signalling connection for the UE authorized for V2X communication over PC5 TS 24.501CR1619
• Triggering service request procedure for V2X communication over PC5 interface TS 24.501CR1968
• Originating MMTEL voice due to upper layers request while T3346 is running TS 24.501CR1254
• T3540 for service request for V2X communications TS 24.501CR2111
• Mobile Terminated Voice Gap for MPS TS 24.501CR2227

In Release 17, the AVC function introduced enhancements for reliable voice service paging and handling, including mechanisms for "Only Paging for voice service" and ensuring the correct paging indication terminology for MUSIM devices in 5GS. It also extended support for MMTEL Voice and MMTEL Video services over non-3GPP access networks, requiring updates to procedures like voice domain selection and service request handling when responding to paging. Furthermore, the release enabled the resumption of RRC connections for critical ProSe and V2X communications over the PC5 interface, ensuring service continuity for direct device communications.

• Handling of service request when responding to paging with voice service indication TS 24.501CR3170
• MMTEL Voice and MMTEL Video in non-3GPP TS 24.501CR3050
• Consistent term on USS communication TS 24.501CR3566
• Resuming a connection due to ProSe discovery/communication over PC5 TS 24.501CR3420
• Resuming the RRC connection upon requesting resources for V2X communication over PC5 TS 24.501CR3449
• Handling of N1 mode capability for non-3GPP access for voice domain selection TS 24.501CR3279

+ 2 more changes

In Release 18, the AVC function introduced new capabilities for direct C2 (Command and Control) communications over PC5, including authorization procedures during 5GS registration and enhanced security for UUAA-MM and UUAA-SM procedures. It also expanded support for critical railway communications (FRMCS) by enabling interworking with GSM-R and allowing dynamic changes to user communication privileges based on identity or talker status. Furthermore, corrections and enhancements were made to IMS registration access checks during active calls and to the signaling for AVC within the 5GMS framework.

• Adding MCX Service Ad hoc Group Communication as alternative capability to support Railway Emergency Communication TS 22.989CR0012
• Authorization of A2X Direct C2 Communications in 5GS TS 24.501CR5193
• Request resources for A2X communication over PC5 TS 24.501CR5357
• Authorization of A2X direct C2 communication during registration in 5GS TS 24.501CR5358
• Changes to Critical Support Applications “Inviting-a-FRMCS User to a voice communication” use case TS 22.989CR0002
• Merging of Railway Emergency Communications TS 22.989CR0003

+ 9 more changes

In Release 19, the AVC function was enhanced with specific focus on Railway Emergency Communication, including new use cases for Public Train and Railway Staff emergency calls. The enhancements also addressed Multi-train voice communication for drivers and ground users, alongside a cleanup and update of the related gap analysis for emergency alerts and multi-talker control. Furthermore, considerations were introduced for satellite access technology regarding the disabling of N1 mode capability when voice service is unavailable.

• Virtual Coupling data communication use case TS 22.989CR13
• Public Train Emergency Communication related use cases TS 22.989CR17
• Railway staff Emergency Communication related use cases TS 22.989CR18
• Enhancement and clean-up of Railway Emergency Communication related use cases TS 22.989CR16
• Enhancement of Multi-train voice communication for Drivers and Ground FRMCS User(s) related use cases TS 22.989CR0019
• Enhancement of Railway Emergency Communication TS 22.989CR0022

+ 5 more changes

In Release 20, the AVC function introduced new use cases for multi-train voice communication, specifically enabling both a Train Controller (a Ground FRMCS user) and a train driver to merge two separate multi-train voice communications. This release also updated the requirements and gap analysis for these multi-train communications, which utilize Ad hoc Group Communications for drivers and ground users.

• New use cases: Merging of two multi-train voice communications by Train Controller (Ground FRMCS user) TS 22.989CR0033
• New use cases: Merging of two multi-train voice communications by the train driver TS 22.989CR0037
• Update of requirements and gap analysis for multi-train voice communication for Drivers and Ground FRMCS User(s) using Ad hoc Group Communications TS 22.989CR0032