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TECHNICAL REPORT
LTE;
Evolved Universal Terrestrial Radio Access (E-UTRA);
Potential solutions for energy saving for E-UTRAN
(3GPP TR 36.927 version 15.0.0 Release 15)
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3GPP TR 36.927 version 15.0.0 Release 15 1 ETSI TR 136 927 V15.0.0 (2018-07)
Reference
RTR/TSGR-0336927vf00
Keywords
LTE
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3GPP TR 36.927 version 15.0.0 Release 15 2 ETSI TR 136 927 V15.0.0 (2018-07)
Intellectual Property Rights
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Foreword
This Technical Report (TR) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
.
Modal verbs terminology
In the present document "should", "should not", "may", "need not", "will", "will not", "can" and "cannot" are to be
interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
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3GPP TR 36.927 version 15.0.0 Release 15 3 ETSI TR 136 927 V15.0.0 (2018-07)
Contents
Intellectual Property Rights . 2
Foreword . 2
Modal verbs terminology . 2
Foreword . 4
Introduction . 5
1 Scope . 6
2 References . 7
3 Definitions, symbols and abbreviations . 8
3.1 Definitions . 8
3.2 Symbols . 8
3.3 Abbreviations . 8
4 General . 9
5 Inter-RAT energy saving . 10
5.1 Study on inter-RAT scenario 1 . 10
5.1.1 Description of scenario 1 . 10
5.1.2 Energy saving procedures . 10
5.1.2.1 OAM-based solution for E-UTRAN cell entering or waking up from dormant mode . 10
5.1.2.2 Signalling based solution for E-UTRAN cell entering or waking up from dormant mode . 11
5.1.2.3 How to exit dormant mode efficiently? . 11
5.1.3 Evaluations and comparisons . 12
5.1.4 Conclusions. 13
6 Inter-eNB energy saving . 14
6.1 Study on inter-eNB scenario 1 . 14
6.1.1 Description of scenario 1 . 14
6.1.2 Energy Saving Procedures . 14
6.1.2.1 Baseline Rel-9 mechanisms . 14
6.1.2.2 How to exit dormant mode efficiently . 14
6.1.3 Evaluations and comparisons . 15
6.1.4 Conclusions. 16
6.2 Study on inter-eNB scenario 2 . 17
6.2.1 Description of scenario 2 . 17
6.2.2 Energy saving procedures . 17
6.2.2.1 OAM-based solution for E-UTRAN cell entering or waking up from dormant mode . 17
6.2.2.2 Signalling based solution for E-UTRAN cell entering or waking up from dormant mode . 18
6.2.2.3 Hybrid O&M and signalling based solution for E-UTRAN cell entering or waking up from
dormant mode . 18
6.2.3 Evaluations and comparisons . 18
6.2.4 Conclusions. 19
7 Intra-eNB energy saving . 20
7.1 Intra-eNB Scenario . 20
7.2 Potential solutions and Evaluations . 20
7.2.1 Configuring MBSFN subframes within the range supported according to current specification
limitation . 20
7.2.2 Configuring DwPTS in subframe 1 and 6 to the minimum length . 20
Annex A (informative): Evaluation Criteria . 21
Annex B (informative): Change History . 22
History . 23
ETSI
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Foreword
rd
This Technical Report has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
ETSI
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3GPP TR 36.927 version 15.0.0 Release 15 5 ETSI TR 136 927 V15.0.0 (2018-07)
Introduction
At present, sustainable development is a long-term commitment for all people in the world. This means not only
development but also innovation. People should do their best to handle the resource shortage and environment
deterioration. Therefore, how to improve the power efficiency and realize the power saving becomes a significant issue.
In the telecom area, most mobile network operators aim at decreasing the power consumption without too much impact
on their network. In this case, the greenhouse emissions are reduced, while the OPEX of operators is saved.
Thus, the power efficiency in the infrastructure and terminal becomes an essential part of the cost-related requirements in
network, and there is a strong need to investigate possible network energy saving solutions.
ETSI
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1 Scope
The present document is the technical report for the study item on Network Energy Saving for E-UTRAN, which was
approved at TSG RAN#47. The objective of the SI is to first identify the relevant scenarios and then study and present
the solutions that are applicable to EUTRAN energy saving. Furthermore, initial evaluation should be performed for
each solution.
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3GPP TR 36.927 version 15.0.0 Release 15 7 ETSI TR 136 927 V15.0.0 (2018-07)
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] RP-100674: "Network Energy Saving for E-UTRAN ", CMCC.
[3] 3GPP TS 36.214: "Physical layer; Measurements ".
[4] 3GPP TS 36.300: "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal
Terrestrial Radio Access (E-UTRAN); Overall description; Stage 2".
[5] 3GPP TS 36.331: "E-UTRA; RRC; Protocol specification Release 10".
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3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in TR 21.905 [1] and the following apply. A
term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905 [1].
3.2 Symbols
For the purposes of the present document, the following symbols apply:
3.3 Abbreviations
For the purposes of the present document, the abbreviations given in TR 21.905 [1] and the following apply. An
abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in
TR 21.905 [1].
eNB enhanced NodeB
EPC Evolved Packet Core
E-UTRAN Evolved UTRAN
ES Energy Savings
ESM Energy Savings Management
FFS For Further Specification
IoT Interference over Thermal
LTE Long Term Evolution
OAM Operations, Administration, Maintenance
OPEX Operating Expenses
RAN Radio Access Network
SON Self-Organizing Networks
TRX Transceiver
UMTS Universal Mobile Telecommunications System
UTRAN Universal Terrestrial Radio Access Network
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4 General
The objective of this study item is to identify potential solutions for energy saving in E-UTRAN and perform initial
evaluation of the proposed solutions, so that a subset of them can be used as the basis for further investigation and
standardization.
The following use cases will be considered in this study item as defined in RP-100674 [2]:
- Intra-eNB energy saving
- Inter-eNB energy saving
- Inter-RAT energy saving
Energy saving solutions identified in this study item should be justified by valid scenario(s), and based on cell/network
load situation. Impacts on legacy and new terminals when introducing an energy saving solution should be carefully
considered. The scope of the study item shall be as follows:
- User accessibility should be guaranteed when a cell transfers to energy saving mode
- Backward compatibility and the ability to provide energy saving for Rel-10 network deployment that serves a
number of legacy UEs
- Solutions shall not impact the Uu physical layer
- The solutions should not impact negatively the UE power consumption
Note that energy saving for HeNB is out of the scope of this study item.
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5 Inter-RAT energy saving
5.1 Study on inter-RAT scenario 1
5.1.1 Description of scenario 1
Networks may consist of LTE cells deployed as capacity enhancement, overlaying existing and optimized 2G/3G network.
Figure 5.1.1-1. Inter-RAT energy saving scenario 1
Figure 5.1.1.1 shows scenario 1 in which E-UTRAN Cell C, D, E, F and G are totally covered by the same legacy RAT
Cell A and B (e.g. UMTS or GSM). Cell A/B has been deployed to provide basic coverage of the services in the area,
while other E-UTRAN cells boost the capacity.
The E-UTRAN cells are only deployed for capacity enhancement at some hot spots, therefore, the continuity of LTE
coverage could not be guaranteed. The legacy network provides the basic coverage, for UEs with multi-mode capability.
The energy saving solutions for this scenario should only be considered in case the E-UTRAN is jointly deployed with
legacy RAT (e.g. UMTS or GSM). It is up to operator's policy whether service for LTE-only capable devices needs to be
maintained.
If all cells have the same multiple PLMNs in a network sharing scenario, there are no issues with the solutions to scenario
1. Limitations related to other network sharing scenarios are not included within this Study Item.
5.1.2 Energy saving procedures
To achieve energy savings in this inter-RAT energy savings scenario, two fundamental approaches, which differ in how
capacity-booster E-UTRAN cells enter or wake up from dormant mode, can be used. These approaches are:
1. OAM-based approach
2. Signalling-based approach
Furthermore, the energy saving policy may prefer not to switch off the E-UTRAN cells that are in an overlapping area
between two or more basic coverage cells (handover region).
5.1.2.1 OAM-based solution for E-UTRAN cell entering or waking up from dormant
mode
The approach is based on the complete set or a subset of following principles:
- E-UTRAN cells enters or leaves dormant mode based on centralized OAM decisions, which are made based on
statistical information obtained from coverage and/or GERAN/UTRAN/E-UTRAN cells, e.g. load information,
traffic QCI, etc The OAM decisions can be pre-configured or directly signalled to the EUTRAN cells.
- If an E-UTRAN cell enters or leaves dormant mode, its intra/inter-RAT neighbour nodes should be informed
either via OAM or signalling.
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5.1.2.2 Signalling based solution for E-UTRAN cell entering or waking up from
dormant mode
The approach is based on the complete set or a subset of following principles:
- E-UTRAN cells may decide to enter dormant mode autonomously or based on information exchanging with the
UTRAN/GERAN coverage cell.
- Switch off decisions/requests will be based on information locally available in the EUTRAN node, including
load information of both the coverage and E-UTRAN cells.
- Switch-on may be performed based upon requests from one or more neighbour inter-RAT nodes, or based on
internal EUTRAN node policies (periodic switch on, max switch off time, etc,).
- Intra-RAT and Inter-RAT neighbour nodes should be informed after on/off decision is made.
- To perform energy saving more efficiently, some energy saving parameters may be exchanged between inter-
RAT neighbour cells if required, e.g. traffic thresholds, time duration, power consumption and so on.
5.1.2.3 How to exit dormant mode efficiently?
Solution A: No assistance
When some E-UTRAN cells are in dormant mode and the load increases on the UTRAN/GERAN coverage cells, the
UTRAN/GERAN coverage cells may not know the most appropriate E-UTRAN cells to wake-up. The overloaded
coverage cells may request wake-up of one or more of the neighbouring dormant E-UTRAN cells. The final decision to
leave dormant mode is however taken by the E-UTRAN cell based on information locally available.
Some possible enhancements to optimize switch on decisions are reported below, whereby the actual “switch on” decision
algorithm implementation could be based on one or several of these enhancements:
Solution B: OAM predefined ‘low-load periods’ policies
When the coverage UTRAN/GERAN cell detects high load, it uses a proprietary algorithm to decide which E-UTRAN
cells should be activated.
The algorithm could rely on pre-defined ‘low-load periods’ policies for each neighbour E-UTRAN cell. The ‘low-load
periods’ information can first be derived from OAM based performance counters, and then the decision implemented in
the coverage cell.
Solution C: IoT measurements
When the coverage UTRAN/GERAN cell detects high load, it can request some dormant E-UTRAN cells to switch on
their listening capability to perform and report Interference over Thermal (IoT) measurements as defined in TS 36.214
[3].
Solution D: UEs measurements
When the coverage UTRAN/GERAN cell detects high load, it can request some dormant E-UTRAN cells to transmit the
pilot signal (e.g. reference signal in LTE) for at least a short time interval i.e. the so-called ‘probing’ interval. After this
interval, all or some E-UTRAN cells will return to dormant mode. The UEs covered by the coverage cell will be
configured to perform Reference Signal (RS) measurements from the E-UTRAN cells during this interval and send
feedback (the same approach as defined for mobility purposes in TS 36.331 [5] could be used). Based on the measurement
results, the UTRAN/GERAN coverage cell will then determine which E-UTRAN cells should be switched on.
Solution E: Positioning information
When the coverage UTRAN/GERAN cell detects high load, it can use a combination of UEs locations, cell locations, and
cell radii/transmit powers in deciding which E-UTRAN cells should be switched on (e.g. cells that cover the UEs).
Furthermore, a timer value can be included in the activation request message sent from the UTRAN/GERAN coverage
cell to the selected E-UTRAN cells. At the expiry of this timer, each cell verifies if the condition required for staying on
has been met, and if not, it autonomously switches off again.
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5.1.3 Evaluations and comparisons
In this section of the TR, the described cell switching procedures for Energy Saving are evaluated and compared. In
addition, all enhancements for signalling-based cell switching approach are also evaluated.
Criteria Cell switch Cell switch on/off based on signalling across RATs; assistance for switch on decisions base
on/off based on on:
centralized
No assistance OAM IoT UE Positioning
OAM decisions
Predefined ‘low measurements measurements information
load periods’
policies
Feasibility Feasible Feasible Feasible Feasible Feasible. Feasible
Applicable
Applicability Applicable Applicable Applicable Applicable Applicable
Backward
Yes Yes Yes Yes Yes Yes
compatibility
Medium:
- Common
O&M or
Medium:
High:
synchronised
High:
– Additional
Medium:
- IoT
O&M between
network Medium:
measurements
RATs is - need to collect
signalling is
- OAM sync is of legacy RAT - Creation of a
Complexity
required. position
needed for
not needed. new cell state
is needed in the
information for
- complexity
activate and
(*Note 1)
hotspot cell in (probing phase)
significant
- Statistics
also depends on
deactivate
for neighbour
ES mode.
number of UEs.
information is
the requested
unnecessary
relation
needed.
level of
cells.
handling
information to
be provided
from the RAN
to O&M.
The most useful
cells could be
selected, at the Since UE
cost of positions and
Possibly limited
introduction of link budgets are
accuracy of IoT
In the worst an intermediate not fully
measurement
case some It has the risk of probing state correlated, the
and thresholds
neighbouring statistic where the cell is method may
Potential ES
may reduce the
sleeping eNBs information is not fully therefore have a
gain
OAM based
efficiency of the
may be turned unable to reflect functioning and limited
solution is
method.
on even if these the real cannot accept efficiency.
relatively static
Accuracy could
eNBs are not conditions.
handover.
Additional gain
be increased at
useful. Energy
could be
the cost of
consumption
obtained at the
complexity
during the
cost of
probing phase
complexity
may reduce its
gain.
-Inter-RAT
signalling for
cell switching Inter-RAT
Inter-RAT Inter-RAT Inter-RAT
No impact on on/off signalling for
Specification signalling for signalling for signalling for
RAN cell switching
- IoT
impact cell switching cell switching cell switching
specifications. on/off and
measurements
on/off on/off on/off
probing trigger
reporting may
be added for
accuracy.
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Medium
because
location and
OAM impact High Low Medium Low Low
coverage
information is
needed.
High, because Medium, new
eNB impact Not foreseen Low Low additional UL "probing" cell Low
receiver state.
Negligible,
additional None to low
measurements depending on
UE impact Not foreseen. Not foreseen. Not foreseen. Not foreseen.
will be required the positioning
during probing mechanism
phase.
*Note1: OAM Sync means OAM for different RAT should be synchronized.
5.1.4 Conclusions
Both OAM-based approach and Signalling-based approach are feasible, applicable and backward compatible for
improving energy efficiency in inter-RAT scenario.
Enhancement solutions on how to exit dormant mode efficiently are feasible, applicable and backward compatible.
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6 Inter-eNB energy saving
6.1 Study on inter-eNB scenario 1
6.1.1 Description of scenario 1
When operators deploy the LTE network, one possible application scenario of energy saving is described hereafter.
Figure 6.1.1-1. Inter-eNB scenario 1 for energy saving
Figure 6.1.1-1 shows scenario1 in which E-UTRAN Cell C, D, E, F and G are covered by the E-UTRAN Cell A and B.
Here, Cell A and B have been deployed to provide basic coverage, while the other E-UTRAN cells boost the capacity.
When some cells providing additional capacity are no longer needed, they may be switched off for energy optimization.
In this case, both the continuity of LTE coverage and service QoS is guaranteed.
If all cells have the same multiple PLMNs in a network sharing scenario, there are no issues with the solutions to scenario
1. Limitations related to other network sharing scenarios are not included within this Study Item.
In general, inter-eNB energy saving mechanisms should preserve the basic coverage in the network.
6.1.2 Energy Saving Procedures
6.1.2.1 Baseline Rel-9 mechanisms
A signalling-based mechanism to achieve energy savings in the inter-eNB scenario 1 has already been specified in Rel-9
as captured in TS 36.300 [4].
In the following some proposed enhancements to the Rel-9 solution are discussed.
6.1.2.2 How to exit dormant mode efficiently
When some E-UTRAN hotspot cells are not active and the load increases on the E-UTRAN, the E-UTRAN coverage
cells may not know the most appropriate E-UTRAN cells to wake-up. The overloaded coverage cells may request wake-
up of one or more of the neighbouring dormant E-UTRAN ce
...