Trace metrics

Description

Trace metrics are a set of data items that can be collected and reported through the 3GPP Subscriber and Equipment Trace framework. This framework, specified in 3GPP TS 32.422 and TS 28.622, provides a standardized way for network operators to monitor the performance and behavior of user equipment (UE) and network elements. Trace metrics encompass a wide range of information, including trace messages (signaling messages exchanged between network entities), Minimization of Drive Tests (MDT) measurements (such as Immediate MDT, Logged MDT, and Logged MBSFN MDT), Radio Link Failure (RLF) reports, Radio Connection Establishment Failure (RCEF) reports, Radio Resource Control (RRC) reports, and 5G Core (5GC) UE level measurements.

The trace framework operates by activating trace sessions on specific network elements or subscribers. When a trace session is active, the network element collects the specified trace metrics and reports them to a trace collection entity (TCE) or a network management system. The metrics can be used for various purposes, including network optimization, fault diagnosis, performance monitoring, and customer experience management. For example, MDT measurements allow operators to assess coverage and quality of service without requiring extensive drive tests, reducing operational costs. RLF and RCEF reports help identify areas with poor coverage or interference, enabling targeted improvements.

Trace metrics are defined at different levels of granularity. At the subscriber level, traces can be activated for specific UEs based on International Mobile Subscriber Identity (IMSI) or other identifiers, allowing detailed monitoring of individual user experience. At the equipment level, traces can be activated on network elements such as base stations or core network nodes, capturing aggregate performance data. The framework supports both immediate reporting (e.g., Immediate MDT) and logged reporting (e.g., Logged MDT), where the UE stores measurements and reports them later when a connection is available.

The introduction of 5G has expanded the scope of trace metrics to include 5GC UE level measurements, which provide insights into the performance of the 5G core network functions. These measurements may include session management, mobility management, and QoS flow statistics. The trace framework is designed to be extensible, allowing new metrics to be defined as network technologies evolve.

In 3GPP Release 19, the term 'trace metrics' was formally defined to consolidate the various types of data that can be traced. This definition reflects the maturity of the trace framework and its role in supporting advanced network management and automation. By providing a standardized set of traceable metrics, 3GPP ensures that operators can consistently monitor and optimize their networks across multi-vendor environments.

Trace metrics are essential for enabling data-driven network operations. They support use cases such as self-organizing networks (SON), network slicing, and quality of experience (QoE) management. As networks become more complex with the introduction of 5G and beyond, the ability to trace and analyze detailed metrics will be crucial for maintaining high performance and reliability.

Purpose & Motivation

Trace metrics exist to provide a standardized and comprehensive set of data that can be collected through the 3GPP trace framework, enabling network operators to monitor, troubleshoot, and optimize their networks effectively. The primary motivation is to ensure that operators have access to detailed information about network and UE behavior without being tied to proprietary solutions from individual vendors. This standardization facilitates multi-vendor interoperability and simplifies network management.

Historically, network monitoring relied on vendor-specific tools and protocols, which made it difficult to correlate data across different network elements and vendors. The 3GPP trace framework was developed to address this by defining a common set of traceable events and measurements. Initially introduced in earlier releases for 2G and 3G networks, the framework has evolved to support 4G and 5G, incorporating new metrics such as MDT measurements and 5GC UE level measurements. The formal definition of 'trace metrics' in Release 19 consolidates these various data types under a single term, reflecting the growing importance of trace data in network automation and analytics.

Trace metrics solve several key problems. First, they enable cost-effective network optimization by reducing the need for manual drive tests through MDT. Second, they provide detailed insights into radio link failures and connection establishment failures, helping operators identify and fix coverage holes. Third, they support performance monitoring and SLA assurance by allowing operators to track key performance indicators (KPIs) at the subscriber and equipment levels. Finally, they facilitate advanced use cases such as network slicing and QoE management by providing the granular data needed to assess and optimize service quality.