EnergySaving state

Description

The EnergySaving state is a operational mode in which a cell or network element (NE) reduces its energy consumption by powering off certain functions or restricting resource usage. This state is typically entered during periods of low traffic (off-peak) and is managed by the network management system. The key characteristic is that even in this state, the cell or NE remains controllable, meaning it can be commanded to return to normal operation when traffic demands increase. This concept was introduced in 3GPP Release 10 and has been refined over subsequent releases.

Architecturally, the EnergySaving state is part of the Self-Organizing Network (SON) framework, specifically the Energy Saving Management (ESM) function. The management system monitors traffic load and energy consumption, and decides when to transition cells or NEs into or out of the EnergySaving state. The state can be applied to various levels: individual cells, base stations, or even entire network elements. When a cell enters EnergySaving state, it may reduce its transmit power, turn off some carriers, or even shut down completely if neighboring cells can provide coverage. The decision is based on policies and algorithms defined in specifications such as TS 28.310 (Energy Efficiency of 5G) and TS 32.551 (Energy Saving Management).

The EnergySaving state is not a simple on/off switch; it involves a set of actions that balance energy savings with service continuity. For example, a cell might enter a 'not available' state for energy saving, but the network ensures that coverage is maintained by other cells. The management system coordinates these actions to avoid coverage holes or service degradation. The state is also reversible: when traffic increases, the cell is brought back to normal operation, often within seconds.

In Release 20, the definition was updated to emphasize that the state is a powered-down condition for energy saving purposes, reflecting the evolution towards more granular and dynamic energy management. The term has been used consistently across releases, with the core idea remaining the same: a temporary, controllable reduction in network resources to save energy.

Key components include the Energy Saving Management function, which resides in the Element Manager (EM) or Network Manager (NM), and the associated procedures for entering and leaving the state. These procedures are defined in TS 28.310 and TS 32.551, which specify the requirements, triggers, and coordination mechanisms. The state is also linked to other SON functions, such as load balancing and coverage and capacity optimization, to ensure that energy savings do not conflict with other network objectives.

Purpose & Motivation

The EnergySaving state was introduced to address the growing energy consumption of mobile networks, particularly during periods of low traffic when network resources are underutilized. Traditional networks were designed to operate at full capacity continuously, leading to significant energy waste during off-peak hours. The EnergySaving state provides a standardized mechanism to reduce energy consumption dynamically without sacrificing network availability or service quality.

Before its introduction, energy-saving techniques were often proprietary and lacked coordination across network elements. This could lead to coverage gaps or service disruptions if not managed properly. The 3GPP standardized the EnergySaving state to enable interoperable and coordinated energy savings across multi-vendor networks. It allows operators to define policies that balance energy efficiency with performance, and to automate the process through SON functions.

The state also supports the industry's sustainability goals by reducing the carbon footprint of mobile networks. As networks become more complex with 5G and beyond, the ability to dynamically manage energy usage is crucial for cost reduction and environmental compliance. The EnergySaving state is a key enabler for green networks, allowing operators to save energy when and where it is most effective.