Coordinated Energy Saving between RAN and Transport Network
draft-chen-green-ran-transport-coord-energy-saving-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Chenxinyu , Jin Zhou | ||
| Last updated | 2026-07-06 | ||
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draft-chen-green-ran-transport-coord-energy-saving-00
GREEN X. Chen
Internet-Draft CMCC
Intended status: Standards Track J. Zhou
Expires: 7 January 2027 ZTE
6 July 2026
Coordinated Energy Saving between RAN and Transport Network
draft-chen-green-ran-transport-coord-energy-saving-00
Abstract
This document provides an coordinated energy saving mechanism between
RAN and transport network.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 7 January 2027.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Coordination . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Extension . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Informative References . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
This document addresses the usecases of RAN and transport network
identified in [I-D.ietf-green-use-cases] through an coordinated
energy saving mechanism.
As described in Section 2.7 of [I-D.ietf-green-use-cases], radio base
stations are typically connected to the backbone network by means of
fiber technologies. The capability of radio link can be adjusted
accordingly to the traffic observed. Some of the power-related
parameters are dynamically configured to adjust the power to the
observed traffic levels with some coarse granularity to avoid the
underutilized of energy. In addition, as described in
[I-D.chen-green-transport-energy-saving] describes the energy saving
in transport network.
However, under current energy-saving methods, energy saving of RAN
and TN are done separately and without coordination. This leads to
RAN adjusting its wireless link according to its own traffic
conditions, but the transport network is unaware of this and still
reserves resources based on the maximum traffic, especially the
internal forwarding resources, optical module resources, and TDM slot
resources, resulting in resource waste.
Therefore, it is necessary to study an energy-saving coordination
mechanism between the RAN and the transport network.
2. Coordination
This section describes the detailed coordination mechanisms that may
exist between the Radio Access Network (RAN) and the Transport
Network (TN).
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+--------------------------------------------------------------------------------+
| |
| +------------------+ |
| | RAN Controller <----------------------------------------------------+
| +--------+---------+ | |
| | | |
| +------------+------------+------------+------------+------------+ | |
| | | | | | | | |
| +---+---+ +---+---+ +---+---+ +---+---+ +---+---+ +---+---+ | |
| | RAN1 | | RAN2 | | RAN3 | | RAN4 | | RAN5 | | RAN6 | | |
| +---^---+ +---^---+ +---^---+ +---^---+ +---^---+ +---^---+ | |
| | | | | | | | |
| | | | | | | | |
+------+------------+------------+------------+------------+------------+--------+ |
| | | | | | |
+--------------------------------------------------------------------------------+ |
| | | | | | | | |
| | +----v----+ | | +----v----+ | | |
| +-------> Access <-------+ +-------> Access <-------+ | |
| | Node 1 | | Node 2 | | |
| +----+----+ +----+----+ | |
| | | | |
| | | | |
| +-----------------+--------------------+ | |
| | | | | |
| | +--------+-------+ | | |
| | | Aggregation | | | |
| | | Node | | | |
| | +--------+-------+ | | |
| | | | | |
| +-----------------+--------------------+ | |
| | | |
| +----------+-------+ | |
| | TN Controller <-------------------------------------------------+
| +------------------+ |
| |
+--------------------------------------------------------------------------------+
Figure 1: Energy Saving Coordination between RAN and Transport
Network
As show in Figure 1, the upper part represents the Radio Access
Network(RAN), which consists of six RAN access nodes, labeled RAN1
through RAN6. These nodes provide radio coverage and user-plane
termination for mobile terminals. All six RAN nodes are under the
control of a single RAN controller, which is responsible for radio
resource management, traffic scheduling, and RAN-side energy-saving
decisions.
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The lower part represents the Transport Network (TN), which provides
the connectivity between the RAN nodes and the core network. This
part comprises three transport nodes arranged into a two-tier
hierarchy, two access nodes, referred to as Access Node 1 and Access
Node 2, and one aggregation node. Access Node 1 and Access Node 2
are directly interact with the RAN nodes, while the Aggregation Node
provides aggregated streams toward the core network. All transport
nodes in the TN are under the control of TN controller (e.g. for path
computation and resource allocation), which is responsible for TN
side energy-saving decisions such as port sleep, switching board
sleep, and TDM timeslot deactivation, etc.
The energy-saving coordination between the RAN and the TN may
include:
* Energy-related information advertisement: energy consumption
prediction, link power status;
* Energy-saving intent decomposition or policy: translating an
operator-level energy-saving goal into concrete actions for both
the RAN and the TN;
* Action alignment: aligning wake-up latencies and co-sleep windows
to avoid one domain sleeping while the other related resources
remains active;
* Traffic/load coordination: jointly migrating services and
rerouting backhaul paths before shutting down a transport link;
This coordination can be realized through four approaches:
* Controller-to-Controller (C2C) coordination is best suited for
policy-level and long-horizon tasks such as intent decomposition,
global state aggregation, and joint energy-budget management,
where minutes-to-hours decision cycles are acceptable. This
approach may exist between peer controllers or orchestrators
across RAN and TN for unified energy saving.
* Node-to-Node (N2N) coordination is best suited for data-plane and
short-horizon tasks such as real-time action synchronization, link
adaptation, and rapid wake-up upon unexpected traffic bursts,
where controller involvement would introduce latency.
* Hybrid coordination combining both C2C and N2N is also possible.
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3. Extension
Depending on the specific coordination approach, different extensions
may be required. For C2C coordination, the interaction typically
relies on CPIs and may necessitate extensions to existing YANG data
models and intent objects within the IETF GREEN framework or network
management agent coordinations. For N2N coordination, nodes may
leverage existing protocols, such as LLDP, IPv6, or some OAM
protocol, without introducing new protocols.
This part requires further study within the GREEN framework and its
YANG modules.
4. Informative References
[I-D.belmq-green-framework]
Claise, B., Contreras, L. M., Lindblad, J., Palmero, M.
P., Stephan, E., and Q. Wu, "Framework for Energy
Efficiency Management", Work in Progress, Internet-Draft,
draft-belmq-green-framework-10, 8 February 2026,
<https://datatracker.ietf.org/doc/html/draft-belmq-green-
framework-10>.
[I-D.chen-green-transport-energy-saving]
Chen, X., Zhou, J., and J. Yan, "Hybrid Energy Saving
Mechanism for Transport Network", Work in Progress,
Internet-Draft, draft-chen-green-transport-energy-saving-
01, 6 July 2026, <https://datatracker.ietf.org/doc/html/
draft-chen-green-transport-energy-saving-01>.
[I-D.ietf-green-terminology]
Chen, G., Boucadair, M., Wu, Q., Contreras, L. M., and M.
P. Palmero, "Terminology for Energy Efficiency Network
Management", Work in Progress, Internet-Draft, draft-ietf-
green-terminology-02, 30 June 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-green-
terminology-02>.
[I-D.ietf-green-use-cases]
Stephan, E., Palmero, M. P., Claise, B., Wu, Q.,
Contreras, L. M., Bernardos, C. J., and X. Chen, "Use
Cases for Energy Efficiency Management", Work in Progress,
Internet-Draft, draft-ietf-green-use-cases-01, 22 January
2026, <https://datatracker.ietf.org/doc/html/draft-ietf-
green-use-cases-01>.
Authors' Addresses
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Xinyu Chen
China Mobile
No.32 Xuanwumen west street
Beijing
100053
China
Email: chenxinyuyjy@chinamobile.com
Jin Zhou
ZTE Corporation
Email: zhou.jin6@zte.com.cn
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