Description
The Optimised Active Codec Set (OACS) is a principle within 3GPP's Self-Organizing Network (SON) framework, specifically under Operations, Administration and Maintenance (OAM) aspects. It addresses the operational challenge of managing a potentially large and diverse set of speech and audio codecs supported by User Equipment (UE) and the network. An OACS is a curated, minimized list of codecs that a network operator actively enables and prefers for use within a specific geographical area or network slice. The goal is to move from a state where all theoretically supported codecs are available to a managed state with a smaller, optimized set.
Implementation of OACS involves coordination between the OAM system, the core network (e.g., Policy and Charging Rules Function - PCRF, or call control nodes), and the radio access network. The OAM system, using inputs from performance management (PM) and fault management (FM) data, determines the optimal codec set based on criteria like voice quality metrics (e.g., Mean Opinion Score - MOS), network capacity, UE capabilities, and interoperability requirements. This optimized set is then configured into the relevant network nodes. During call setup, nodes like the MSC Server (for CS calls) or the P-CSCF/Interrogating-CSCF (for IMS calls) will use the OACS to guide codec negotiation, prioritizing codecs within the set.
The process reduces the 'codec jungle' where numerous codec negotiation attempts can lead to call setup delays, suboptimal voice quality selections, or interoperability issues. By defining an OACS, operators can ensure a more consistent and high-quality voice experience, simplify troubleshooting, and reduce the testing and validation burden associated with a large codec portfolio. It is a key enabler for efficient network operation and is closely tied to other SON use cases like Mobility Robustness Optimization (MRO) and Energy Saving Management (ESM), as codec selection can impact handover success and radio resource efficiency.
Purpose & Motivation
OACS was introduced to solve operational and quality problems stemming from the proliferation of voice codecs in 3GPP networks. As networks evolved from GSM (with mainly FR, EFR, AMR) to UMTS and LTE (adding AMR-WB, EVS, and others), and with the rise of VoLTE and VoNR, the number of possible codec combinations exploded. This created a 'codec negotiation maze' where call setup could involve multiple offer/answer rounds, increasing latency. Furthermore, some codecs, while efficient, might not provide the best quality in certain radio conditions, leading to inconsistent user experience.
The traditional approach of supporting all UE-capable codecs was operationally burdensome, requiring extensive testing and complex configuration management. OACS provides a framework for a data-driven, optimized approach. It allows operators to analyze network performance data to identify which codecs actually deliver the best quality and efficiency in their specific network environment and for their specific mix of UEs. By actively managing and pruning the active codec set, operators can improve overall voice service reliability, reduce call setup times, and concentrate optimization efforts on a smaller set of codecs, leading to more predictable network behavior and simplified fault management.
Key Features
- Defines a managed, subset of codecs actively promoted for use in a network region, as opposed to all supported codecs.
- Driven by OAM system analysis of performance metrics like voice quality, success rates, and UE capability reports.
- Aims to reduce call setup complexity and latency by streamlining the codec negotiation procedure.
- Improves consistency of voice quality experience by prioritizing proven, high-performance codecs for local conditions.
- Reduces operational overhead for testing, configuration, and troubleshooting of voice services.
- Integrates with broader SON frameworks for automated or semi-automated optimization of network parameters.
Evolution Across Releases
Introduced as a concept within the Self-Organizing Network (SON) framework, specifically in the context of OAM requirements and use cases. Defined the need for an Optimised Active Codec Set to manage operational complexity and improve voice service performance, establishing it as a key principle for network management automation.
Defining Specifications
| Specification | Title |
|---|---|
| TS 28.062 | 3GPP TS 28.062 |