ETSI TR 101 612 V1.1.1 (2014-09)

TECHNICAL REPORT
Intelligent Transport Systems (ITS);
Cross Layer DCC Management Entity for operation
in the ITS G5A and ITS G5B medium;
Report on Cross layer DCC algorithms and performance
evaluation
2 ETSI TR 101 612 V1.1.1 (2014-09)

Reference
DTR/ITS-0020055
Keywords
ITS, Spectral Management
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3 ETSI TR 101 612 V1.1.1 (2014-09)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 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 Introduction . 11
5 Architecture . 12
5.1 Introduction . 12
5.2 Configurations of the DCC architecture . 12
5.2.1 DCC configuration 1 . 12
5.2.2 DCC configuration 2 . 13
5.2.3 DCC configuration 3 . 15
5.2.4 DCC configuration 4 . 16
5.3 Communication stack . 17
5.3.1 Facilities layer . 17
5.3.2 Networking and transport layer . 18
5.3.3 Access layer . 19
5.3.3.1 Gatekeeper architecture . 19
5.3.3.2 Traffic class prioritization . 20
5.3.3.3 DCC queues . 21
5.3.3.4 DCC power control . 21
5.3.3.5 DCC flow control . 22
5.3.3.6 ITS-G5 radio . 23
5.3.4 Management plane . 23
5.3.4.1 DCC_CROSS component . 23
5.3.4.2 DCC_CROSS_Facilities . 24
5.3.4.3 DCC_CROSS_Net&Tr . 25
5.3.4.4 DCC parameter evaluation . 26
5.3.4.5 DCC_CROSS_Access. 26
5.3.4.6 CBR evaluation . 27
5.4 Channel load limits . 28
5.4.1 Basic system level assumptions . 28
5.4.2 Test procedure concept . 28
5.4.3 System level CBR limit for conformance test . 29
5.4.4 Channel load limits for each individual ITS-S . 31
6 Evaluation metrics . 33
6.1 Introduction . 33
6.2 Metrics measurement . 33
7 Simulation scenarios & parameters . 35
7.1 Scenarios definition . 35
7.2 Estimation of the number of ITS-S in the communication range . 36
7.3 Mobility scenarios . 37
7.3.1 Homogeneous ITS-S density . 37
7.3.1.1 General . 37
7.3.1.2 1D highway . 38
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4 ETSI TR 101 612 V1.1.1 (2014-09)
7.3.1.3 2D Parking lot . 38
7.3.2 Heterogeneous scenarios . 38
7.3.2.1 Heterogeneous highway . 38
7.3.2.2 Heterogeneous clustered highway . 39
7.3.2.3 Heterogeneous elevated highway . 40
7.3.3 Weak LOS scenarios . 40
7.3.3.1 Blind intersection (static obstacles) . 40
7.3.3.2 Blind highway (mobile obstacles) . 40
7.4 Communication scenarios . 41
7.5 General functions . 42
7.6 Key Performance Indicators . 43
8 Initial simulation results . 43
8.1 Introduction . 43
8.2 Performance evaluation of reactive and linear adaptive DCC mechanisms . 44
8.2.1 General . 44
8.2.2 Scenario description . 44
8.2.3 Performance evaluation results . 45
8.2.4 Discussion on initial performance evaluation . 48
Annex A: DCC algorithms . 49
A.1 General DCC types: reactive and adaptive . 49
A.2 Reactive DCC class . 50
A.3 Adaptive DCC mechanisms . 51
Annex B: Simulation platforms . 54
B.1 iTETRIS ITS platform. 54
B.1.1 Introduction and general architecture . 54
B.1.2 The network simulator ns-3 and its extensions for iTETRIS . 54
B.2 IGOR . 56
B.2.1 Introduction . 56
B.2.2 Architecture . 56
B.3 Channel models . 56
History . 57

ETSI
5 ETSI TR 101 612 V1.1.1 (2014-09)
Intellectual Property Rights
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
server (http://ipr.etsi.org).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Report (TR) has been produced by ETSI Technical Committee Intelligent Transport Systems (ITS).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "may not", "need", "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
6 ETSI TR 101 612 V1.1.1 (2014-09)
1 Scope
The present document provides a preliminary technical overview of the cross-layer decentralized congestion control
(DCC) architecture to be implemented in the ITS-S. It describes DCC functions and testable DCC limits and includes
initial performance evaluation results based on simulations. In addition, reference scenarios and parameters used for
performance evaluation purposes and the corresponding evaluation metrics are summarized. It will be completed by a
Technical Report with validation set-up and results. Both will serve as a basis for the Technical Specification of the
Cross Layer DCC control entity in the ITS G5A and ITS G5B media.
2 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
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
2.1 Normative references
The following referenced documents are necessary for the application of the present document.
Not applicable.
2.2 Informative references
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] IEEE 802.11-2012: "IEEE Wireless Local Access Network - Part 11: Wireless LAN Medium
Access Control (MAC) and Physical Layer (PHY) Specifications".
[i.2] ETSI TS 102 687: "Intelligent Transport Systems (ITS); Decentralized Congestion Control
Mechanisms for Intelligent Transport Systems operating in the 5 GHz range; Access layer part".
[i.3] ETSI EN 302 636-4-1: "Intelligent Transport Systems (ITS); Vehicular Communications;
GeoNetworking; Part 4: Geographical addressing and forwarding for point-to-point and point-to-
multipoint communications; Sub-part 1: Media-Independent Functionality".
[i.4] ETSI TS 102 636-4-2: "Intelligent Transport Systems (ITS); Vehicular Communications;
GeoNetworking; Part 4: Geographical addressing and forwarding for point-to-point and point-to-
multipoint communications; Sub-part 2: Media-dependent functionalities for ITS-G5".
[i.5] ETSI TS 102 723-3: "Intelligent Transport Systems (ITS); OSI cross-layer topics; Part 3: Interface
between management entity and access layer".
[i.6] ETSI TS 102 723-4: "Intelligent Transport Systems (ITS); OSI cross-layer topics; Part 4: Interface
between management entity and networking & transport layer".
[i.7] ETSI TS 102 723-5: "Intelligent Transport Systems (ITS); OSI cross-layer topics; Part 5: Interface
between management entity and facilities layer".
[i.8] ETSI TS 102 723-10: "Intelligent Transport Systems (ITS); OSI cross-layer topics;
Part 10: Interface between access layer and networking & transport layer".
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7 ETSI TR 101 612 V1.1.1 (2014-09)
[i.9] ETSI TS 102 723-11: "Intelligent Transport Systems (ITS); OSI cross-layer topics;
Part 11: Interface between networking and transport layer and facilities layer".
[i.10] ETSI EN 302 665: "Intelligent Transport Systems (ITS); Communications Architecture".
[i.11] ETSI EN 302 663: "Intelligent Transport Systems (ITS); Access layer specification for Intelligent
Transport Systems operating in the 5 GHz frequency band".
[i.12] ETSI EN 302 571: "Intelligent Transport Systems (ITS); Radiocommunications equipment
operating in the 5 855 MHz to 5 925 MHz frequency band; Harmonized EN covering the essential
requirements of article 3.2 of the R&TTE Directive".
[i.13] ECC/DEC/(08)01 ECC Decision on the harmonised use of the 5875-5925 MHz frequency band
for Intelligent Transport Systems (ITS).
[i.14] ETSI TS 102 792: "Intelligent Transport Systems (ITS); Mitigation techniques to avoid
interference between European CEN Dedicated Short Range Communication (CEN DSRC)
equipment and Intelligent Transport Systems (ITS) operating in the 5 GHz frequency range".
[i.15] ETSI TS 103 257: "Intelligent Transport Systems (ITS); Access Layer; ITS-G5 Channel Models
and Performance Analysis Framework".
[i.16] M. Rondinone et al.: "iTETRIS: A Modular Simulation Platform for the Large Scale Evaluation of
Cooperative ITS Applications", Simulation Modelling Practice and Theory, Volume 34, May
2013.
[i.17] M. Boban: "GEMV2: Geometry-based Efficient Propagation Model for V2V Communication",
available at http://vehicle2x.net.
[i.18] G. Bansal and J.B. Kenney: "Controlling Congestion in Safety-Message Transmissions: A
Philosophy for Vehicular DSRC Systems," Vehicular Technology Magazine, IEEE, vol.8, no.4,
pp. 20 - 26, December 2013.
[i.19] B. Kloiber, J. Härri, T. Strang.: "Dice the TX power - Improving Awareness Quality in VANETs
by Random Transmit Power Selection", IEEE Vehicular Networking Conference (VNC'12), Seoul,
Republic of Korea, November 2012.
[i.20] T.Tielert, D.Jiang, L. Delgrossi, H. Hartenstein, "Design methodology and evaluation of rate
adaptation based congestion control for vehicle safety communications," IEEE Vehicular
Networking Conference (VNC '11), Amsterdam, Netherlands, Nov. 2011.
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in IEEE 802.11-2012 [i.1],
ETSI EN 302 665 [i.10], ETSI EN 302 663 [i.11], ETSI EN 302 571 [i.12] and the following apply:
adaptability: performance characteristic, which indicates that a system is capable of adjusting its parameters to
maintain the same level of performance when the input conditions are changing
CBR evaluation: function that transforms the hardware specific CL value into a hardware independent local CBR
value
channel access time: variable representing the time for an ITS-S to access the channel and send a packet.
channel busy ratio: time-dependent value between zero and one (both inclusive) representing the fraction of time that
the channel was busy
NOTE: this is one implementation of the channel load metric.
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8 ETSI TR 101 612 V1.1.1 (2014-09)
channel load: reference metrics, ranging between 0 and 1, which represents the relative quality of the channel. The
higher the load on the channel, the less reliable the reception of the transmitted message is
NOTE: This value is an indication for the channel usage, provided by the radio hardware.
channel resource limit: maximum amount of usable resources of a channel. It corresponds to a trade-off between the
maximum usage of the channel for periodic safety-related messages, maximizing the performance of the ITS-G5
technology and allowing any event-based emergency packet to be reliably transmitted
communication range: maximum Euclidian distance from the sender where a communication can take place with a
message reception rate of more than 95 %
cross-layer DCC: cooperation mechanisms based on components distributed over several layers of the protocol stack
which jointly work together to fulfil the operational requirements of DCC
DCC_ACC: DCC gatekeeper component located at the Access Layer
DCC channel switching indication: indication sent to the DCC functions at upper layers in the case where a message
has been switched to a channel different from the one initially requested
DCC channel switching parameter: parameter indicating to which other channels a message may be rerouted in case
the channel initially planned is congested DCC_FAC: DCC component located at the facilities layer
DCC_CROSS: DCC cross-layer component located in the management plane
DCC_CROSS_Access: function in the DCC_CROSS component that provides DCC control parameters to DCC_ACC
DCC_CROSS_Facilities: function in the DCC_CROSS component that provides DCC control parameters to the
facilities layer and to the applications Layer
DCC_CROSS_Net&Tr: function in the DCC_CROSS component that provides DCC channel switching parameters to
the networking and transport layer and a DCC channel switching indication to the DCC_CROSS_Facilities
DCC fairness: a concept where any ITS-S under the same channel conditions have an equal opportunity of accessing
the channel for periodic messages, while maintaining a channel access margin to always allow the exchange of safety-
critical event-based messages
DCC flow control: function that retrieves the messages from the DCC queues according to their priorities and transfers
them for transmission to the ITS-G5 radio functionalities
DCC flow control parameters: DCC parameters generated by the DCC_CROSS_Access that indicate to the DCC flow
control the amount of usable resources available for transmission on the radio
DCC_NET: DCC component located in the networking & transport layer
DCC parameter evaluation: function that takes the local CBR and the global DCC RX parameters as input and
evaluates them to obtain the internal DCC parameters and the global DCC TX parameters
DCC power control: optional function that sets the ITS-G5 TX power level according to the DCC power control
parameters
DCC power control parameters: DCC parameters generated by the DCC_CROSS_Access function to set the ITS-G5
TX power level limits
DCC prioritization: function that routes messages per channel to DCC queues according to the IEEE 802.11 [i.1]
EDCA access category indicated in the traffic class field
DCC queues: set of buffer space in the DCC_ACC component in the access layer that stores the transmission requests
sorted according to their priority (access class)
NOTE: A DCC queue retains a message, if a message in a DCC queue with higher priority is present.
decentralized congestion control: set of mechanisms for ITS-S to maintain network stability, throughput efficiency
and fair resource allocation to ITS-Ss using ITS-G5 access technology
global channel busy ratio: maximum value of the local channel busy ratio, the 1-hop channel busy ratio and the 2-hop
channel busy ratio
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9 ETSI TR 101 612 V1.1.1 (2014-09)
global DCC RX parameters: DCC parameters received from neighbouring ITS-S (e.g. their local CBR measurement)
and locally determined parameters (e.g. number of neighbours) that are used to derive the currently available channel
resources and the global DCC TX parameters
NOTE: These parameters comprehend the basic metrics to derive the current level of resource usage in order to
classify the congestion. Metrics based on local knowledge are used in a first step, such as the Channel
Busy Ratio (CBR) and the number of neighbouring ITS-S. To avoid channel congestion, it is appropriate
to also use cooperatively determined metrics that can be retrieved by exchanging the local metrics.
global DCC TX parameters: DCC parameters broadcasted to neighbouring ITS-S
internal DCC parameters: management parameters that are used to disseminate the DCC parameter evaluation result
to DCC_CROSS_Facilities, to DCC_CROSS_Net&Tr and to DCC_CROSS_Access
NOTE: Internal DCC parameters are derived by the DCC parameter evaluation function based on the DCC RX
parameters and the local CBR value. These parameters define how much channel resources an ITS-S is
allowed to use.
inter-reception rate: receiver-based metric representing the time between the successful reception of two CAM
messages
NOTE: As the receiver knows the time between two CAM messages, inter-reception rate indicates message losses
impacting the ITS-S safety applications.
local channel busy ratio: time-dependent value between zero and one (both inclusive), representing the channel busy
ratio (CBR) as perceived locally by a specific ITS-S
message generation parameters: parameters that inform the components in the facilities layer and in the applications
Layer about the available channel resources
neighbour density: metric illustrating the average number of ITS-S per square meter in the communication range of an
ITS-S
resilience: performance characteristic, which indicates that a system is capable of providing a sufficient level of
performance under certain conditions
responsiveness: performance characteristic, which indicates that a system is capable of adjusting its parameters fast
enough to maintain a certain level of performance to sudden, brief and recurring changes in the input conditions
RSSI/RCPI: indication of the received signal power level at the receiver
NOTE: RSSI/RCPI is a receiver-centric metrics that indicates the distance to the transmitter as well as the
potential impact of interfering radio signals.
scalability: performance characteristic, which indicates that a system is capable of keeping the level of performance
while increasing the number of participating ITS-S
TTT Road Tolling: radio interface specified at CEN mainly for road tolling applications
NOTE: Formerly referred to as CEN DSRC.
3.2 Symbols
For the purposes of the present document, the following symbols apply:
CR Channel Resources Limit
limit
CBR Channel Busy Ratio Limit
limit
target
CBR Target Channel Busy Ratio
N Number of ITS-Ss
Sta
P Transmit Power
TX
R Message Rate Limit
limit
tx
R Transmit Rate
R Message Rate
M
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10 ETSI TR 101 612 V1.1.1 (2014-09)
T Time during which a DCC queue is closed (OFF), in order to regulate congestion from the DCC
off
queue; also considered to be the idle time for the DCC flow control function
T Time during which a DCC queue is open (ON) and messages from the DCC queues are sent to the
on
ITS-G5 radio also considered to be the message transmit duration for the DCC flow control
function
Toff Idle Time Limit
limit
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ACC-XDCC DCC_CROSS_Access
AI Adaptive Increase
AIMD Additive Increase Multiplicative Decrease
ANPI Average Noise Power Indicator
C2X Car-to-X communication system
CAM Cooperative Awareness Message
CAT Channel Access Time
CBR Channel Busy Ratio
CCH Control Channel
CEN Commité Européen de Normalisation
CL Channel Load
CR Communication Range
CS Carrier Sensing
CSMA/CA Carrier Sense Multiple Access with Collision Avoidance
DCC Decentralized Congestion Control
DENM Decentralized Environmental Notification Message
DSRC Dedicated Short Range Communication
DTN Delay Tolerant Networks
DUT Device Under Test
DVB-H Digital Video Broadcast - Handheld
EDCA Enhanced Distributed Channel Access
FA Facility Layer-Application Layer
FAC-XDCC DCC_CROSS_Facilities
GN GeoNetworking
IDR Information Dissemination Rate
IRT Inter-Reception Time
ITS Intelligent Transportation System
ITS-S ITS Station
KPI Key Performance Indicator
LOS Line-of-Sight
MD Multiplicative Decrease
NET-XDCC DCC_CROSS_Net&Tr
NLOS Non Line-of-Sight
OFDM Orthogonal Frequency Division Multiplexing
OBU On-Board Unit
PDA Personal Digital Assistant, e.g., smartphone
QPSK Quadrature Phase Shift Keying
RCPI Received Channel Power Indicator
RF Radio Frequency
RSNI Received Signal-to-Noise Indicator
RSSI Received Signal Strength Indicator
RSU Road Side Unit
RX Receiver
SAP Service Access Point
SHB Single Hop Broadcast
STA Stations
TC Traffic Class
TTT Transport & Traffic Telematics
TCP Transmission Control Protocol
TX Transmitter
UMTS Universal Mobile Telecommunication Systems
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11 ETSI TR 101 612 V1.1.1 (2014-09)
VT Vehicular Technology
XDCC DCC_CROSS
4 Introduction
The DCC functionality is part of the ITS station (ITS-S) reference architecture given in ETSI EN 302 665 [i.10]. A
schematic description including interfaces is displayed in Figure 1. It consists of the following DCC components:
• DCC_ACC located in the Access as specified in ETSI TS 102 687 [i.2];
• DCC_NET located in the Networking and Transport as specified in ETSI TS 102 636-4-2 [i.4];
• DCC_FAC located in the Facilities;
• DCC_CROSS located in the management plane.
The components are connected through the DCC interface 1 to interface 4 as shown in Figure 1. These interfaces are
mapped to the corresponding cross-layer interfaces as described in ETSI TS 102 723-3 [i.5], ETSI TS 102 723-4 [i.6]
and ETSI TS 102 723-5 [i.7].
Figure 1: Overview of DCC Architecture
The present document describes the cross-layer architecture of the DCC mechanisms for ITS-G5 and focuses more
specifically on the DCC management functions in the DCC_CROSS component and the DCC functions in each layer,
as well as their interactions.
The present document does not specify a particular DCC algorithm to control the load on the channel between ITS-Ss;
instead channel load limits are provided that all ITS-Ss need to follow regardless of DCC implementation.
Further, the present document proposes a set of scenarios for simulation as well as an evaluation methodology to be
able to test and compare different approaches of the DCC algorithms The present document provides initial simulation
results for two different DCC algorithms.
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12 ETSI TR 101 612 V1.1.1 (2014-09)
5 Architecture
5.1 Introduction
The primary objective for the DCC algorithm in the ITS-S is to calculate based on input parameters the currently
allowed channel resource limit.
Four different configurations of the DCC architecture have been identified depending on if the ITS-S is operating on a
single channel or multiple channels and if only local or both local and global input parameters to the DCC algorithm are
present. In Table 1, the different configuration possibilities are outlined.
Table 1: The different identified DCC configurations
Supported channels Input parameters

Single Multi Local only Local and global
DCC configuration 1 X X
DCC configuration 2 X X X
DCC configuration 3 X X X
DCC configuration 4 X X X X
The specification of the cross-layer DCC behaviour (DCC_CROSS) should support interoperability between the
different DCC configurations. For all configurations, it is assumed that a measurement of the channel load (CL) is
provided by the ITS-G5 radio component. This is the primary input to the DCC algorithm. The DCC entity processes
the CL measurement data and feeds the DCC algorithm with a local channel busy ratio (CBR). All DCC configurations
listed in Table 1 provide the local CBR value and support single channel operation. In DCC configurations 2 and 4,
global parameters are also available through the use of ETSI TS 102 636-4-2 [i.4], which is the media-dependent part of
the GeoNetworking (GN) protocol. By using this functionality of the GN protocol, the ITS-S can disseminate
information about its local CL, the highest received CL from its neighbour ITS-S, its current message rate, output power
etc., in GN single-hop broadcast (SHB) packets. When global input parameters are available those are saved in the GN
location table of the GN protocol. The DCC configurations are detailed in clauses 5.2.1-5.2.4.
5.2 Configurations of the DCC architecture
5.2.1 DCC configuration 1
In DCC configuration 1, single channel and local DCC input parameters are present.
The calculation of available resources of the channel is only based on local CL measurements, transformed to internal
DCC parameters and distributed to the DCC_CROSS_Facilities and DCC_CROSS_Access functions. The facilities can
use the information to restrict the number of generated packets but it also gives the facilities the possibility to prioritize
between different types of data traffic. If higher layers perform according to the output from the DCC algorithm, the
access layer does not have to for example restrict the number of packets on the channel.
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13 ETSI TR 101 612 V1.1.1 (2014-09)
Applications Layer
DCC
CAM DENM Service
Facilities
Facilities Layer
Networking & Transport Layer
Message
internal DCC
generation
parameters
parameters
RX Message path TX Message path
DCC
DCC parm.
parameter
evaluation DCC prioritization
evaluation
. . . .
CBR
. . . .
. . . .
evaluation
. . . .
DCC queues
Local CBR
CL
. . . .
. . . .
DCC Access DCC flow control
DCC flow
ITS-G5 radio
control
parameters
RX signal TX signal
DCC_Cross Access Layer
Wireless Medium
Figure 2: Architecture overview of the DCC configuration 1:
Single channel operation with local DCC information
5.2.2 DCC configuration 2
In DCC configuration 2, the ITS-S only operates on a single channel but has access to global input as well as local.
Adding global DCC parameters provides the possibility to align the DCC parameters among all ITS-S in
communication range (Figure 3). These parameters are stored in a neighbour table in the networking & transport. For
example, ETSI TS 102 636-4-2 [i.4] specifies the dissemination of global DCC parameters and their storage in the GN
location table. Together with the local CL measurement the global DCC parameters are taken as input for the evaluation
of the internal DCC parameters, which are distributed and used in the same way as in the first configuration (Figure 2).
Having a global DCC coordination also enables the control of the transmit power level as part of the DCC mechanism
in the future. This will reduce the impact of the hidden node problem that may occur if this control is not provided.
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14 ETSI TR 101 612 V1.1.1 (2014-09)
Applications Layer
DCC
CAM DENM Service
Facilities
Facilities Layer
Global DCC TX
parameters
Networking & Transport Layer
All neighbours
Global DCC RX DCC Header
Neighbour
global DCC
parameters construction
Table
RX parameters
DCC
DCC parm.
parameter
evaluation DCC prioritization
evaluation
.. .. .. ..
CBR
.. .. .. ..
DCC queuDCC queueses
evaluation
Local CBR CL
.. .. .. ..
DCC flow control
DCC flow control
parameters
DCC Access DCC power control
DCC power control
ITS-G5 radio
parameters
Access Layer
DCC_Cross
Wireless Medium
Figure 3: Architecture overview of the DCC configuration 2:
Single channel with global DCC information
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15 ETSI TR 101 612 V1.1.1 (2014-09)
5.2.3 DCC configuration 3
In DCC configuration 3, the ITS-S has the capability of switching between different channels but it has only access to
local DCC information.
When deploying multi-channel configurations as shown in Figure 4, the DCC mechanisms can include off-loading of
messages from congested to uncongested channels. In this case, CBR measurements provided for each of the available
channels by the ACC_XDCC function are used as input to the NT_XDCC function, which controls the channel
switching in the networking & transport layer. Note that channel switching is possible even for a single transceiver
implementation. This requires CL monitoring on all the target channels.
Applications Layer
DCC
CAM DENM Service
Facilities
Facilities Layer
DCC channel
switching Networking & Transport Layer
indication
DCC Net&Tr
RX Message path TX Message path
DCC channel
DCC
switching
DCC parm.
parameter
parameters
evaluation
DCC prioritization
evaluation
. . . .
CBR
. . . .
. . . .
evaluation
. . . .
Local CBR
DCC queues
CL
. . . .
. . . .
DCC Access DCC flow control
DCC flow control
ITS-G5 radio
parameters
DCC_Cross Access Layer
Wireless Medium
Figure 4: Architecture overview of the DCC configuration 3:
Multi-channel operation with local DCC information
ETSI
16 ETSI TR 101 612 V1.1.1 (2014-09)
5.2.4 DCC configuration 4
In DCC configuration 4, the ITS-S has the capability of switching between different channels and it has access to global
DCC information, see Figure 5.
In contrast to the single channel DCC parameter evaluation, the neighbour table, such as the GN location table, holds
the global DCC parameters for each monitored channel. Based on these global parameters the internal DCC parameters
are evaluated for each channel.
Applications Layer
DCC
CAM DENM Service
Facilities
DCC channel
Facilities Layer
switching
Networking & Transport Layer
parameters
DCC Net&Tr
Global DCC TX
Global DCC RX DCC Header
Neighbour
parameters
parameters construction
Table
DCC
DCC parm.
parameter
evaluation DCC prioritization
evaluation
.. .. .. ..
CBR
.. .. .. ..
DCCDCC qu queueseues
evaluation
Local CBR
CL . . . .
DCC flow control
DCC flow control
parameters
DCC power control
DCC Access Flow control
DCC power control
ITS-G5 radio
parameters
DCC_Cross Access Layer
Wireless Medium
Figure 5: Architecture overview of the DCC configuration 4:
Multi-channel with global DCC information
ETSI
17 ETSI TR 101 612 V1.1.1 (2014-09)
5.3 Communication stack
5.3.1 Facilities layer
The facilities layer DCC functions (DCC_FAC), included in the facilities depicted in Figure 6, control the load
generated by facilities service messages (e.g. CAM and DENM) per channel. The message rate is either controlled by
indicating the maximum rate to the facilities/applications, or by dropping packets that overload the channel. The
DCC_FAC also potentially initiate switching between channels if the ITS-S supports this feature. Moreover, they are
responsible for mapping the message priorities indicated by applications/facilities to the corresponding traffic classes.
The facilities layer DCC functions are described in Table 2.
Applications Layer
RX Message TX Message
DCC
CAM DENM Services
Facilities
Facilities Layer
Message generation
parameters
RX Message TX Message
Networking & Transport Layer
Figure 6: Facilities layer DCC interactions
Table 2: Facilities layer DCC functionality
Facilities Layer DCC functionality
Type Name from / to Description
Input TX message Application Interface As given in ETSI EN 302 665 [i.10].
Under DCC rate control.
RX message Networking & Transport As given in ETSI TS 102 723-11 [i.9]
No impact from DCC.
Message generation DCC_CROSS_Facilities Indicate the share of radio resources
parameters the ITS-S can use.
Output TX message Networking & Transport As given in ETSI TS 102 723-11 [i.9].
Under DCC rate control.
RX message Application Interface As given in ETSI EN 302 665 [i.10].
No impact from DCC.
ETSI
18 ETSI TR 101 612 V1.1.1 (2014-09)
5.3.2 Networking and transport layer
The role of the networking and transport layer DCC functions (DCC_NET), depicted in Figure 7, is to provide global
DCC parameters and to disseminate the local DCC parameters to other ITS-S. These DCC functions also enable
multichannel operation. The networking and transport layer DCC functions are described in Table 3.
Facilities Layer
DCC channel
RX Message TX Message
switching parameters
Networking & Transport Layer
DCC Net&Tr
Global DCC TX
Neighbour
parameters
Table
DCC
parameter
TX Message
evaluation
RX Message
Global DCC RX Global DCC RX
Access Layer
parameters parameters
Figure 7: Networking & Transport Layer DCC interactions
Table 3: Networking & Transport Layer DCC functionality
Networking & Transport Layer DCC functionality
Type Name from / to Descriptio
...