ETSI TR 103 494 V1.1.1 (2018-01)

TECHNICAL REPORT
Broadband Radio Access Networks (BRAN);
Study of central coordination of WAS/RLANs
operating in the 5 GHz frequency band

2 ETSI TR 103 494 V1.1.1 (2018-01)

Reference
DTR/BRAN-60022
Keywords
broadband, control, protocol
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3 ETSI TR 103 494 V1.1.1 (2018-01)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 6
3 Definitions, symbols and abbreviations . 7
3.1 Definitions . 7
3.2 Symbols . 9
3.3 Abbreviations . 10
4 Use cases of central control/coordination of WAS/RLAN in 5 GHz bands. 11
4.1 Use case 1: Coexistence management between coordinated and uncoordinated WAS/RLANs . 11
4.2 Use case 2: Coexistence management between coordinated and uncoordinated WAS/RLANs managed
by a single network operator . 12
4.3 Use case 3: Coexistence management between similar/dissimilar WAS/RLANs managed by multiple
network operators . 12
5 Possible requirements . 13
5.1 Requirements for application to WAS/RLAN in 5 GHz bands . 13
5.2 Other possible requirements . 13
6 Study on central control/coordination concepts . 14
6.1 Introduction . 14
6.2 Hierarchical Control Concepts . 14
6.2.1 Hierarchical Control concepts in COHERENT . 14
6.2.2 Possible enhancements to Hierarchical Control concepts . 15
6.2.2.1 General principles . 15
6.3 Abstractions . 16
6.3.1 Abstraction concepts in COHERENT. 16
6.3.1.1 Introduction . 16
6.3.1.2 Conceptual overview . 17
6.3.1.3 Examples of abstractions and network graphs . 17
6.3.1.3.1 Introduction . 17
6.3.1.3.2 Nodes . 18
6.3.1.3.3 Edges . 19
6.3.1.3.4 Abstracted network graph . 19
6.3.1.3.5 Overview of abstraction procedure . 19
6.3.2 Possible enhancements to Abstraction concepts . 20
6.3.2.1 Examples of weighted digraph . 20
6.3.2.1.1 Introduction . 20
6.3.2.1.2 Directed edge or arc . 20
6.3.2.1.3 Weight . 21
6.3.2.1.4 Path and directed path . 21
6.4 Network Slicing and Slice-Specific Network View . 22
6.4.1 Network Slicing and Slice-Specific Network View in COHERENT . 22
6.4.2 Possible enhancements to Network Slicing and Slice-Specific Network View . 23
6.4.2.1 Network slice resource management using Slice-Specific Network View . 23
7 System architecture . 24
7.1 COHERENT architecture and functionalities . 24
7.1.1 Overview of the COHERENT architecture . 24
7.1.2 Control and Coordination plane . 25
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4 ETSI TR 103 494 V1.1.1 (2018-01)
7.1.2.1 C3 and RTC . 25
7.1.2.2 System Functionalities of RTCs and C3 . 26
7.1.2.2.1 C3 Functionalities . 26
7.1.2.2.2 RTC Functionalities . 26
7.1.2.2.3 Southbound API Functionalities . 26
7.2 Possible enhancements to architecture and functionalities . 26
7.2.1 System description . 26
7.2.2 Possible procedures in the enhanced architecture . 28
7.3 Architecture for heterogeneous wireless access technologies . 28
8 Measurements and reports . 29
8.1 Measurements and reports in IEEE 802.11 standard . 29
8.1.1 Radio measurements . 29
8.1.1.1 Introduction . 29
8.1.1.2 Radio measurement procedures . 30
8.1.2 Wireless Network Management (WNM) . 31
8.1.2.1 Introduction . 31
8.1.2.2 WNM procedures . 31
8.1.3 Management procedures . 31
8.1.3.1 Overview of IEEE 802.11 management approach . 31
8.2 MLME SAP interface . 32
8.2.1 Introduction. 32
8.2.2 Relevant procedures . 32
8.3 Measurements in 3GPP LTE standards . 33
8.4 Possible new reports . 33
8.4.1 IEs for general reporting . 33
8.4.2 Reports for supporting QoS enforcement per flow or per radio bearer . 34
9 Control/Coordination messages . 35
9.1 Registration to C3 and initial operation . 35
9.2 Operational performance . 36
9.3 Interference coupling . 36
9.4 Dependency on the traffic type . 36
9.5 C3 actions for QoS enforcement . 37
9.5.1 Introduction. 37
9.5.2 Virtual LBT . 37
9.5.3 Carrier aggregation and LBT thresholds . 37
9.5.4 MCS selection . 38
10 Void . 38
11 Examples of algorithms . 38
11.1 Algorithm for low complexity spectrum reassignment . 38
11.1.1 Introduction. 38
11.1.2 Channel reassignment based on channel transition graph . 38
11.2 Algorithm for channel assignment based on graph information . 40
11.2.1 Introduction. 40
11.2.2 Channel assignment using graph representation of interference relationship among nodes and their
expected QoS . 40
11.3 Algorithm for channel assignment considering interference aggregation effect at reference points . 42
11.3.1 Introduction. 42
11.3.2 Interference aggregation effect coefficient . 42
11.4 Algorithm for the selection of candidate serving C3 instances for moving nodes . 43
11.4.1 Introduction. 43
11.4.2 Selection of candidate serving C3 instances for moving nodes . 44
11.5 Algorithm for network coordination based on spectrum utilization pattern . 45
11.5.1 Introduction. 45
11.5.2 Spectrum utilization pattern . 45
11.5.3 Channel ranking methodology based on spectrum utilization pattern . 47
Annex A: Change History . 49
History . 50

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5 ETSI TR 103 494 V1.1.1 (2018-01)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
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Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
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Foreword
This Technical Report (TR) has been produced by ETSI Technical Committee Broadband Radio Access Networks
(BRAN).
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.
Introduction
Developing technologies for 5G Broadband Systems is one of the objectives of the European Commission. The EC
H2020 project COHERENT [i.14], "Coordinated Control and Spectrum Management for 5G Heterogeneous Radio
Access Networks" has addressed topics related to the application of the basic principles of wired Software - Defined
Networks (SDN) to wireless networks.
The present document includes the main outcome of the project and the results of additional studies.
The present document does not address any regulatory issues and does not address mandatory requirements such as
those related to article 3.2 of Directive 2014/53/EU [i.13].
Some results incorporated in the present document received funding from the European Union's Horizon 2020 research
and innovation programme under grant agreement No 671639.

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6 ETSI TR 103 494 V1.1.1 (2018-01)
1 Scope
The present document contains studies of the architectures and the protocols supporting the central coordination of
WAS including RLANs (WAS/RLAN) operating in the 5 GHz bandIt also includes information provided by a radio
node/network of radio nodes and the procedures for the coordination of the operation of these nodes.
2 References
2.1 Normative references
Normative references are not applicable in the present document.
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] Alexandros Kostopoulos, George Agapiou, Deng Junquan, Dorin Panaitopol, Fang-Chun Kuo
(Editor-in-Chief), Kostas Katsalis, Navid Nikaein, Mariana Goldhamer, Tao Chen, Rebecca
Steinert, Roberto Riggio: "System Architecture and Abstractions for Mobile Networks", EU
H2020 5G-PPP COHERENT Project Deliverable D2.2, July 2016.
NOTE: Available online at http://www.ict-coherent.eu/.
[i.2] Nguyen et al.: "SDN and virtualisation-based LTE mobile network architectures: A comprehensive
survey", Wireless Personal Communications, vol. 86, no. 3, pp. 1401-1438, 2016.
[i.3] F. Ahmed et al.: "Distributed Graph Coloring for Self-Organization in LTE Networks", Journal of
Electrical and Computer Engineering, 2010.
[i.4] P. Cardieri: "Modeling interference in wireless ad hoc networks", IEEE Communication Surveys
& Tutorials, vol. 12, no. 4, p. 551-572, 2010.
[i.5] Ericsson Technical White paper: "5G systems - enabling industry and society transformation",
2015.
[i.6] 5G White Paper, white paper, NGMN Alliance, 2015.
[i.7] Antti Anttonen (Editor-in-Chief), Tao Chen, Tapio Suihko, Aarne Mämmelä, Sundar Daniel
Peethala, Nidal Zarifeh, Furqan Ahmed, Junquan Deng, Ragnar Frej-Hollanti, Sergio Lembo, Olav
Tirkkonen, Antonio Cipriano, Dorin Panaitopol, Per Kreguer, Akhila Rao, Rebecca Steinert, Chia-
Yu Chang, Roberto Riggio, Shah Nawaz Khan, Mariana Goldhamer, Pawel Kryszkiewicz, Fang-
Chun Kuo, George Agapiou, Dimitri Marandin, Yi Yu: "First report on physical and MAC layer
modelling and abstraction", EU H2020 5G-PPP COHERENT Project Deliverable D3.1,
June 2016.
NOTE: Available online at http://www.ict-coherent.eu/.
TM
[i.8] IEEE 802.11 -2012: "IEEE standard for Information Technology, Local and metropolitan area
networks, Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY)
Specifications".
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7 ETSI TR 103 494 V1.1.1 (2018-01)
[i.9] 3GPP TS 36.213 (V14.0.0) (2016-09): "Evolved Universal Terrestrial Radio Access (E-UTRA);
Physical layer procedures (Release 14)".
[i.10] ETSI TS 136 331 (V14.3.0): "LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); Radio
Resource Control (RRC); Protocol specification (3GPP TS 36.331 version 14.3.0 Release 14)".
[i.11] ETSI TS 136 214 (V14.2.0): "LTE; Evolved Universal Terrestrial Radio Access (E-UTRA);
Physical layer; Measurements (3GPP TS 36.214 version 14.2.0 Release 14)".
[i.12] 3GPP TS 36.423 (V14.0.0) (2016-09): "Evolved Universal Terrestrial Radio Access Network
(E-UTRAN); X2 application protocol (X2AP) (Release 14)".
[i.13] Directive 2014/53/EU of the European Parliament and of the Council of 16 April 2014 on the
harmonisation of the laws of the Member States relating to the making available on the market of
radio equipment and repealing Directive 1999/5/EC Text with EEA relevance.
[i.14] ICT-COHERENT.
NOTE: Available at http://www.ict-coherent.eu/.
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
arc: in digraph, an ordered pair of vertices is called a directed edge or an arc
Central Controller and Coordinator (C3): C3 is a logically centralized entity in charge of network-wide control and
coordination among entities in WAS/RLAN based on Centralized Network View (CNV)
NOTE: C3 could be implemented with physical control instances sharing network information with each other.
channel assignment: process which determines one or more frequency blocks (channels) for radio nodes
NOTE: Coexistence decision can be made when determining the channel(s) for radio nodes.
Control Plane Function: function which controls the operation of the system through appropriate messages
Control Vertex: vertex in a (di)graph which represents a C3 instance
digraph: graph which consists of a set of vertices connected by edges, where the edges have a direction associated with
them
directed path: digraph, a directed path is a sequence of arcs which connect a sequence of vertices, with the restriction
that all arcs in the path are directed in the same direction
dissimilar WAS/RLANs: dissimilar WAS/RLANs are WAS/RLANs that use different RATs without the
same/common wireless network coexistence technologies
graph: set of vertices connected by edges
head: arc (v ,v ) is considered to be directed from vertex v to vertex v , v is called the head of the arc
i j i j j
hierarchical control: control architecture based on a central controller which coordinates the operation of other
controllers
network slice instance: run-time instantiation of a Network Slice
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8 ETSI TR 103 494 V1.1.1 (2018-01)
network slice or service slice: network slice/service slice is a logical network that comprises a set of network functions
and the corresponding resources required to provide End-to-End support for specific network services, network
applications and radio configurations of WAS/RLAN
NOTE: The network services may be specific to some particular use cases or business applications. A network
slice can span all domains of the network: software programs running on cloud nodes, specific
configurations of the transport network, a dedicated radio access configuration, as well as settings of the
WAS/RLAN devices. Different network slices contain different network applications and configuration
settings.
Network View (NV): database containing information specific to the network operation
NOTE: A Local NV includes parameters available at a local radio entity while a Central NV includes parameters
available at a central controller/coordinator which are provided or resulting from the LNV.
Northbound interface (NBi): API transferring information and controls between a program running additional control
application and a Controller
path: in a graph is a finite or infinite sequence of edges which connect a sequence of vertices which, by most
definitions, are all distinct from one another
programmable control: function of the controller platform transferring the information from the SBi to the NBi and
enabling a programmer to write control applications on top of the controller
Radio Access Network: radio access network (RAN) is part of a public land mobile telecommunication system
controlled by an Operator
Radio Local Area Network (RLAN): intended to cover smaller geographic areas like homes, offices and to a certain
extent buildings being adjacent to each other
NOTE: Radio LANs are also known as Wireless LANs (WLANs).
Radio Transceiver (RT): logical entity that provides radio access with full WAS/RLAN node functions
NOTE: RT can be realized by either of the combinations of R-TP, vRP and/or RTC. A set of RTs forms a radio
access network (RAN/WAS) which is coordinated and controlled by C3. Some implementation examples
of RTs include LTE eNBs in cellular networks or WiFi APs in the WLANs. An RT could be composed
by one vRP (virtual device) and one or more R-TPs (physical devices). For example, in the Cloud-RAN
(C-RAN) architecture the R-TP coincides with the RRH, while the vRP coincides with the BBU Pool.
However, several other functional splits can be considered.
Radio Transmission Point (R-TP): physical entity implementing full or partial WAS/RLAN node functions while the
rest of functions are offloaded to and handled by the vRP
NOTE: An R-TP may include control plane functions.
Real-Time Controller (RTC): logical entity in charge of local or region-wide control, targeting at low latency control
operations such as, for example, MAC scheduling. RTC maintains the Local Network View (LNV)
NOTE: RTC can run on one RT or on a virtualized platform.
residency duration: represents the total time for a moving node to reside within the service area of a certain C3
service plane: collection of network applications and configurations of WAS/RLAN systems designed to deliver
services that satisfy the needs of system users
similar WAS/RLANs: WAS/RLANs that use the same RAT or different RATs with the same/common wireless
network coexistence technologies
Southbound interface (SBi): API transferring information and controls between network entities and a Controller
spectrum: within the present document the word "spectrum" indicates a combination of time-frequency resources
tail: arc (v ,v ) is considered to be directed from vertex v to vertex v , v is called the tail of the arc
i j i j i
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9 ETSI TR 103 494 V1.1.1 (2018-01)
Transport Node (TN): logical entity that is located between RTs and the core network (CN)
NOTE: A set of TNs forms a backhaul/fronthaul network whose data plane can be configured by C3. A network
switch is one of the implementation examples of TN.
Virtual Radio Processing (vRP): logical entity comprising a computing platform allowing for centralized processing
of full or partial RAN node functions (including the user plane and the control plane) offloaded from one R-TP or
multiple R-TPs
NOTE: A vRP includes control plane functions.
weight: one value or a set of values, assigned as a label to a vertex or edge (arc) of a graph (digraph)
weighted graph: graph whose vertices or edges have been assigned weights; more specifically, a vertex-weighted
graph has weights on its vertices and an edge-weighted graph has weights on its edges
weighted digraph: digraph whose vertices or arcs have been assigned with weights
Wireless Access System (WAS): defined as end-user radio connections to public or private networks. In the present
document WAS and RAN are interchangeably used
NOTE: Both RAN and WAS can include RLANs
3.2 Symbols
For the purposes of the present document, the following symbols apply:
(*) ordered sequence
{*} unordered sequence
∈ is a member of
∪ union
∩ intersection
\ the difference of two sets
α pathloss exponent
,v ) the arc a that connects an ordered pair of vertices v and v
a=(vi j i j
A(G) the arc set of a digraph G
CH the i-th channel
i
CI the i-th C3 instance
i
d the distance between the i-th and the j-th node
ij
D(p , p )  the distance between two points p and p
1 2 1 2
e=v v an edge e that connects vertices v and v
i j i j
E(G) the edge set of a graph G
ℱ failed spectrum usage event
G=(V,E) a graph G that consists of a pair of vertex set V and edge set E
I interference level from tail vertex to head vertex
(tail, head)
I interference from vertex v to vertex v
(vi,vj) i j
L a selection priority level of C3 instance CI determined by the amount of estimated available
i i
spectrum for the moving node from CI
i
L distance from the i-th node to the reference point P
iPk k
N number of failed spectrum usage event
ℱ
N number of successful spectrum usage event
N number of spectrum usage event
P(v ,v )=(v ,v ,v ,v ) a path from start vertex v to end vertex v , which consists of a sequence of vertices v ,v ,v ,v
s e s i j e s e s i j e
and the edges between adjacent vertices along the sequence
P index of the reference point
k
P transmit power of each node
max
successful spectrum usage event
SINR signal to interference plus noise ratio threshold
th
a
T an estimated arrival time for a certain moving node to enter the serving area of C3 instance CI
i
r
T an estimated residency duration for a certain moving node within serving area of C3 instance
i
CIi
th
T a threshold of time duration for successful spectrum usage on channel CH
i i
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10 ETSI TR 103 494 V1.1.1 (2018-01)
T a start time of estimation window
WinStart
T a stop time of estimation window
WinStop
spectrum usage event
v the vertex v
V(G) the vertex set of a graph G
W weight of the arch between the i-th and the j-th node
ij
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
3GPP Third Generation Partnership Project
th
5G 5 Generation Mobile Networks
AC Access Category
ANDSF Access Network Discovery and Selection Function
AP Access Point
AP Access Point
API Application Programming Interface
APSD Automatic Power Save Delivery
AWGN Additive White Gaussian Noise
BBU Baseband Unit
BS Base Station
BSS Basic Service Set
NOTE: As used in [i.8].
C3 Central Controller and Coordinator
CDF Cumulative Distribution Function
CM Coordination Manager
CN Core Network
CNV Centralized Network View
COE Coordination Enabler
CQI Channel Quality Indicator
C-RAN Cloud Radio Access Network
CSI Channel State Information
CW Contention Window
DL Downlink
DSCP Differentiated Services Coding Point
eNB Evolved Node B
eNodeB Evolved Node B
EU European Union
E-UTRAN Evolved Universal Terrestrial Radio Access Network
GPS Global Positioning System
HO Hand-Over
IE Information Element
IEEE Institute of Electrical and Electronics Engineers
IoT Internet of Things
IP Internet Protocol
LAA Licensed-Assisted Access
LAN Local Area Network
LBT Listen Before Talk
LNV Local Network View
LTE Long-Term Evolution
MAC Media Access Control
MCS Modulation and Coding Schemes
MIB Management Information Base
MLME MAC subLayer Management Entity
NaaS Network as a Service
NBi Northbound Interface
NGMN Next Generation Mobile Networks Alliance
NR New Radio (3GPP name for 5G technology)
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11 ETSI TR 103 494 V1.1.1 (2018-01)
OAM Operations and Management
PDU Protocol Data Unit
PHY Physical Layer
QCI QoS Class Identifier
QoE Quality of Experience
QoS Quality of Service
RAN Radio Access Network
RAT Radio Access Technology
RLAN Radio Local Area Network
RRH Remote Radio Head
RS Reference Signal
RSSI Received Signal Strength Indicator
RT Radio Transceiver
RTC Real-Time Controller
R-TP Radio Transmission Point
SAP Service Access Point
SBi Southbound Interface
SDN Software Defined Network
SINR Signal to Interference and Noise Ratio
SME Station Management Entity
SNIR Signal to Noise plus Interference Ratio
SNMP Simple Network Management Protocol
SNV Slice-Specific Network View
SSID Service Set IDentifier
STA Station
TN Transport Node
TP Transmission Point
TS Technical Standard
UE User Equipment
UL Uplink
UP User Plane
vRP Virtual Radio Processing
WAS Wireless Access System
WiFi Wireless Fidelity
WLAN Wireless Local Area Network
WNM Wireless Network Management
WT WLAN Termination
4 Use cases of central control/coordination of
WAS/RLAN in 5 GHz bands
4.1 Use case 1: Coexistence management between
coordinated and uncoordinated WAS/RLANs
Coordinated and un-coordinated WAS/RLANs are shown in Figure 4.1, where Operator A manages its network
operation (i.e. coordinated WAS/RLAN) on 5 GHz band (e.g. LAA-LTE) while private WLAN access point operates
nearby (i.e. uncoordinated WAS/RLAN).
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12 ETSI TR 103 494 V1.1.1 (2018-01)

Figure 4.1: Coordinated and uncoordinated WAS/RLANs
4.2 Use case 2: Coexistence management between
coordinated and uncoordinated WAS/RLANs managed by a
single network operator
Similar/dissimilar WAS/RLANs managed by a single network operator are shown in Figure 4.2, where operator A
network operates two LTE base stations and a 5G base station. Operator A network can also operate Wireless LAN
access point by utilizing ANDSF.
Operator A
Core network
Operator A
Operator A
LTE base station 1
5G base station
Operator A
LTE base station 2
Figure 4.2: Similar/dissimilar WAS/RLANs managed by single network operator
4.3 Use case 3: Coexistence management between
similar/dissimilar WAS/RLANs managed by multiple
network operators
Similar/dissimilar WAS/RLANs managed by multiple network operators are shown in Figure 4.3, where operator A
network operates two LTE base stations and a 5G base station while operator B operate a 5G base station, LTE base
station and WLAN access point. The coexistence management between different network operators could enhance their
network performance.
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13 ETSI TR 103 494 V1.1.1 (2018-01)

Figure 4.3: Similar/dissimilar WAS/RLANs managed by multiple network operators
5 Possible requirements
5.1 Requirements for application to WAS/RLAN in 5 GHz bands
According to the use cases as shown in clause 4, the following general requirements should be satisfied in the central
control/coordination of WAS/RLAN in 5 GHz bands:
• Central control/coordination mechanism should support coexistence management between coordinated and
uncoordinated WAS/RLANs.
• Central control/coordination mechanism should support coexistence management between similar/dissimilar
WAS/RLANs.
• Central control/coordination mechanism should support coexistence coordination between different network
operators operating WAS/RLANs in 5 GHz bands.
5.2 Other possible requirements
In order to achieve global optimization of the network operations of WAS/RLAN, the following requirements should be
satisfied:
• Central control/coordination mechanism should support network management for high efficient resource
utilization, which considers both radio spectrum and, when appropriate, core network resource per service
slice.
• Central control/coordination should support the mechanism for low complexity spectrum reassignment, which
considers spectrum transition capability within availability time period of the allocated spectrum.
• Central control/coordination should support moving radio nodes.
• Central control/coordination should support the service continuity of moving nodes, which includes serving C3
selection for moving nodes considering available spectrum and residency duration within the C3 along
predicted trajectory of the moving node.
• Central control/coordination should support the quick identification of the spectrum in which a radio node can
operate with high efficiency while considering the spectrum utilization pattern.
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14 ETSI TR 103 494 V1.1.1 (2018-01)
• Central control/coordination should support the spectrum assignment to increase the number of nodes whose
QoS are satisfied, which considers each node's QoS requirements and the possible QoS degradation due to
interference among nodes.
• Central control/coordination should support the spectrum assignment to reduce interference aggregation effect
from different nodes, while considering the effect of interference aggregation.
6 Study on central control/coordination concepts
6.1 Introduction
The transposition of SDN principles to the wireless domain is not straightforward, given the specificities of the wireless
network operation. In the present document are included the main outcomes of the project COHERENT related to a
control framework, based on SDN principles, applicable to the operation of heterogeneous wireless technologies in the
same band.
More specifically, this clause provides an overview of central control/coordination concepts applied to WAS/RLAN in
5 GHz bands.
First, the present document reviews the architecture, one of the main outcomes of the project COHERENT and
implements the following concepts:
• Control plane-user plane separation;
• Abstracted view of the network;
• Service slices;
• APIs offering a common framework for developing control applications.
6.2 Hierarchical Control Concepts
6.2.1 Hierarchical Control concepts in COHERENT
The architecture introduced in [i.1] adopts a centralized solution, SDN-based, which could achieve global optimization
of the wireless WAS/RLAN networks. Furthermore, by applying SDN principles to wireless networks is enabled the
control programmability, i.e. a software developer is provided with the software APIs for writing control applications
faster.
However, global optimization of SDN-based wireless networks comes at the expense of scalability and latency.
To address these issues, an SDN-based centralized solution has been introduced in [i.1], which employs two
hierarchical control mechanisms, namely network-wide control and real-time control as shown in Figure 6.1 and could
achieve global optimization of the wireless networks with higher scalability and lower latency.
ETSI
15 ETSI TR 103 494 V1.1.1 (2018-01)
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Figure 6.1: Network wide control and real-time control in hierarchical control scheme
The Central Controller and Coordinator (C3) is a logically centralized entity, which provides network-wide
control/coordination for the wireless networks deployed in a given geographic area. For overcoming the scalability
issues in a large and dense wireless network deployment, or for performance/reliability reasons, the logically centralized
C3 can be implemented with distributed control instances sharing network information with each other. Sharing
network information among C3 instances creates the logically Centralized Network View (CNV).The Real Time
Controller (RTC) is a logical entity that is designed to offer real-time control to overcome the latency challenges. RTC
should be close to the physical radio elements so that it could adjust to rapidly varying wireless networks. RTCs in the
wireless network may not coordinate with each other and therefore network information is not shared between RTCs. In
actual implementations RTC could be a separated entity or could be included into RT.
By separating control functionalities between C3 and RTC, C3 makes decisions that ar
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