ETSI TS 103 175 V1.1.1 (2015-06)

TECHNICAL SPECIFICATION
Intelligent Transport Systems (ITS);
Cross Layer DCC Management Entity
for operation in the ITS G5A and ITS G5B medium

2 ETSI TS 103 175 V1.1.1 (2015-06)

Reference
DTS/ITS-0020046
Keywords
ITS, Spectral Management
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3 ETSI TS 103 175 V1.1.1 (2015-06)
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 . 7
3 Definitions, symbols and abbreviations . 7
3.1 Definitions . 7
3.2 Symbols . 9
3.3 Abbreviations . 9
4 Introduction . 10
5 DCC architecture . 11
5.1 Overview . 11
5.2 DCC_ACC . 11
5.3 DCC_NET . 12
5.4 DCC_FAC . 12
5.5 DCC_CROSS . 12
6 DCC management entity . 12
6.1 Overview . 12
6.2 DCC parameter evaluation . 13
6.3 DCC_CROSS_Access . 15
6.4 DCC_CROSS_Net . 16
6.5 DCC_CROSS_Facilities . 16
7 DCC limits specification . 17
7.1 Overview . 17
7.2 Requirements . 17
8 Interfaces . 18
8.1 Overview . 18
8.2 Interface (1) with DCC_ACC (MI SAP) . 18
8.2.1 MI-GET.request . 18
8.2.1.1 Function . 18
8.2.1.2 Semantics . 19
8.2.2 MI-GET.confirm . 19
8.2.2.1 Function . 19
8.2.2.2 Semantics . 19
8.2.3 MI-SET.request . 19
8.2.3.1 Function . 19
8.2.3.2 Semantics . 20
8.2.4 MI-SET.confirm . 20
8.2.4.1 Function . 20
8.2.4.2 Semantics . 20
8.2.5 DCC Parameters at the MI-SAP . 21
8.3 Interface (2) with DCC_NET (MN SAP) . 21
8.3.1 MN-GET.request . 21
8.3.1.1 Function . 21
8.3.1.2 Semantics . 21
8.3.2 MN-GET.confirm . 22
8.3.2.1 Function . 22
8.3.2.2 Semantics . 22
8.3.3 MN-SET.request . 22
8.3.3.1 Function . 22
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4 ETSI TS 103 175 V1.1.1 (2015-06)
8.3.3.2 Semantics . 22
8.3.4 MN-SET.confirm . 22
8.3.4.1 Function . 22
8.3.4.2 Semantics . 23
8.3.5 DCC Parameters at the MN-SAP . 23
8.4 Interface (3) with DCC_FAC (MF SAP) . 24
8.4.1 MF-SET.request . 24
8.4.1.1 Function . 24
8.4.1.2 Semantics . 24
8.4.2 MF-SET.confirm . 24
8.4.2.1 Function . 24
8.4.2.2 Semantics . 24
8.4.3 DCC Parameters at the MF-SAP . 25
9 Test procedures . 25
9.1 Introduction . 25
9.2 General Test requirements . 26
9.3 Test case 1: Homogeneous ITS traffic, energy threshold test . 27
9.4 Test case 2: Homogeneous ITS traffic, header decoding test . 28
9.5 Test case 3: Sensitivity threshold correction . 28
9.6 Test case 4: DCC stability . 28
Annex A (informative): List of requirements . 30
A.1 Introduction . 30
A.2 Requirements . 30
Annex B (informative): Other DCC entities . 32
B.1 Introduction . 32
B.2 DCC_ACC . 32
B.3 DCC_NET . 32
B.4 DCC_FAC . 33
Annex C (informative): DCC algorithms capable of satisfying testable limits . 34
C.1 Introduction . 34
C.2 State-Based Reactive DCC . 34
C.3 Linear Adaptive DCC . 35
History . 36

ETSI
5 ETSI TS 103 175 V1.1.1 (2015-06)
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 Specification (TS) 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", "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 TS 103 175 V1.1.1 (2015-06)
1 Scope
The present document specifies the functionality of the decentralized congestion control (DCC) entity residing in the
management plane for the ITS-G5A, ITS-G5B, and ITS-G5D radio interfaces, collectively known as the 5 GHz ITS
frequency band.
The purpose of the DCC operation is to evaluate the load of the active radio channels and to optimize the radio channel
usage by managing the ITS-S DCC parameters. Another purpose is to keep track and help the exchange of DCC
parameters which cannot be conveyed via the data plane between the different layers.
The present document specifies:
• The necessary support functions of DCC that needs to be in the management plane, i.e. cross-layer DCC
operations.
• The required interface parameters between the DCC management entity and the DCC entities in the facilities,
the networking & transport and the access layers.
• The testing procedures and corresponding test cases.
2 References
2.1 Normative 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.
The following referenced documents are necessary for the application of the present document.
[1] IEEE 802.11-2012: "IEEE Standard for Information technology -- Telecommunications and
information exchange between systems Local and metropolitan area networks -- Specific
requirements Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY)
Specifications".
[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".
[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".
[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".
[5] ETSI TS 102 723-1: "Intelligent Transport Systems (ITS); OSI cross-layer topics;
Part 1: Architecture and addressing schemes".
[6] ETSI EN 302 665: "Intelligent Transport Systems (ITS); Communications Architecture".
[7] ETSI EN 302 663: "Intelligent Transport Systems (ITS); Access layer specification for Intelligent
Transport Systems operating in the 5 GHz frequency band".
[8] 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".
ETSI
7 ETSI TS 103 175 V1.1.1 (2015-06)
[9] 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".
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
reference 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] ETSI TR 101 612: "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".
[i.2] G. Bansal, J. Kenney, and C. Rohrs, "LIMERIC: A Linear Adaptive Message Rate Algorithm for
DSRC Congestion Control", IEEE Trans. Vehicular Technology, Vol. 62, No. 9, Nov. 2013.
[i.3] B. Cheng, M. Gruteser, J. Kenney, G. Bansal, K. Sjoberg, "Performance Evaluation of a Mixed
Vehicular Network with CAM-DCC and LIMERIC Vehicles", Proceedings of the IEEE World of
Wireless, Mobile and Multimedia Networks (IEEE WoWMoM'15), Boston, USA, 2015.
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 [1],
ETSI EN 302 665 [6], ETSI EN 302 663 [7], ETSI EN 302 571 [8] and the following apply:
burst of messages: set of one or more messages that the gatekeeper transfers to the ITS-G5 radio at one time
CBR target value: value used in GN as discriminator for the evaluation of the global CBR
NOTE: In the present document it is set to a fixed value and equal to the congestion threshold C
TH
channel busy ratio: time-dependent value between zero and one (both inclusive) representing the fraction of time that
an individual radio channel used by an ITS-S was busy
NOTE: This is one possible implementation of the channel load metric.
channel resource limit: maximum amount of available resources of an individual radio channel used by an ITS-S
NOTE: 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.
chipset channel load: chipset data type that the DCC_ACC entity will transform into a local channel specific CBR
value
cross-layer DCC: cooperation mechanisms based on entities distributed over several layers of the protocol stack which
jointly work together to fulfil the operational requirements of DCC
DCC_ACC: DCC entity located at the Access Layer that acts as a gatekeeper and also provides the local CBR values
for all ITS-G5 radio channels used by a certain ITS-S
DCC_CROSS: DCC cross-layer entity located in the management plane
DCC_CROSS_Access: function in the DCC_CROSS entity that exchanges DCC control parameters with DCC_ACC
ETSI
8 ETSI TS 103 175 V1.1.1 (2015-06)
DCC_CROSS_Facilities: function in the DCC_CROSS entity that provides DCC control parameters to the facilities
layer and to the applications
DCC_CROSS_Net: function in the DCC_CROSS entity that provides DCC channel resources parameters to the
networking and transport layer
DCC_FAC: DCC entity located at the facilities layer
DCC fairness: concept where any ITS-S under the same channel conditions has an equal opportunity of accessing the
radio 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 interface
DCC flow control parameters: DCC parameters generated by the DCC_CROSS_Access that indicate to the DCC flow
control the amount of available resources available for transmission on the radio
DCC_NET: DCC entity 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 per radio channel
DCC power control parameters: DCC parameters generated by the DCC_CROSS_Access function to set the ITS-G5
TX power level limits per radio channel
DCC prioritization: function that routes messages per channel to DCC queues according to the IEEE 802.11 [1]
EDCA access category indicated in the traffic class field
DCC queues: set of buffer space in the DCC_ACC entity in the access layer that temporarily stores the transmission
requests per given radio channel sorted according to their priority and time of arrival
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-S 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 for a given radio channel
NOTE: The evaluation of the global channel busy ratio, the 1-hop channel busy ratio and the 2-hop channel busy
ratio is specified in ETSI TS 102 636-4-2 [4].
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 per given radio channel broadcasted to neighbouring ITS-S using the
same channel
idle time: time interval between the end of transmission of a first burst and the start of transmission of the next burst by
the ego ITS-S on a given radio channel, considering the inter-frame spacing and inter-leaving transmissions from other
senders
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9 ETSI TS 103 175 V1.1.1 (2015-06)
internal DCC parameters: management parameters that are used to disseminate the DCC parameter evaluation result
to DCC_CROSS_Facilities, to DCC_CROSS_Net and to DCC_CROSS_Access
NOTE: Internal DCC parameters are derived by the DCC parameter evaluation function based on the global DCC
RX parameters and the local CBR value. These parameters define how much channel resources an ITS-S
is allowed to use on each individual radio channel used by the ITS-S.
inter-reception rate: receiver-based metric representing the time between the successful reception of two messages
from the same ITS-S on the same given radio channel
NOTE: If the receiver knows the time between two CAM messages, the inter-reception rate indicates message
losses impacting the ITS-S safety applications.
ITS-G5A: frequency band ranging from 5 875 MHz to 5 905 MHz
ITS-G5B: frequency band ranging from 5 855 MHz to 5 875 MHz
ITS-G5D: frequency band ranging from 5 905 MHz to 5 925 MHz
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 for each individual radio channel
message generation parameters: parameters that inform the components in the facilities layer and in the applications
layer about the available channel resources
transmission duration: total time during which the ITS-S own messages are sent on the target radio channel as a burst,
not considering the inter-frame spacing or inter-leaving transmissions from other senders
NOTE: It is also considered to be the transmit duration for the DCC flow control function.
transmit ratio: contribution to the CBR on a given radio channel caused by the transmissions of the ego ITS-S
3.2 Symbols
For the purposes of the present document, the following symbols apply:
α Parameter of the linear adaptive algorithm
β Parameter of the linear adaptive algorithm
CBR Channel Busy Ratio
CBR Available CBR percentage per radio channel and per ITS-S (output of DCC algorithm)
a
target
CBR Target CBR in the linear adaptive algorithm
C Congestion threshold
TH
C Weight factor
w
NDL_timeUp Inertia control parameter in the state-based DCC algorithm (upwards direction)
NDL_timeDown Inertia control parameter in the state-based DCC algorithm (downwards direction)
N Number of ITS-S
Sta
P Received Power
RX
P Transmit Power
TX
R Message Rate
M
T Idle time
off
T Idle Time Limit
off Limit
T Measured equilibrium of the DUT idle time
offm
T Transmission duration
on
NOTE: All channel specific values refer to an individual radio channel used by an ITS-S.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ASN Abstract Syntrax Notation
AWGN Additive White Gaussian Noise
CA Cooperative Awareness (basic service)
CAM Cooperative Awareness Message
ETSI
10 ETSI TS 103 175 V1.1.1 (2015-06)
CBR Channel Busy Ratio
CEN Comité Européen de Normalisation
CL Channel Load
DCC Decentralized Congestion Control
DEN Decentralized Environmental Notification (basic service)
DENM Decentralized Environmental Notification Message
DSRC Dedicated Short Range Communication
DUT Device Under Test
E.I.R.P Equivalent Isotropically Radiated Power
EDCA Enhanced Distributed Channel Access
FAC-ID Facilities interface Identifier
GN GeoNetworking
IP Internet Protocol
ITS Intelligent Transportation System
ITS-S ITS StationMAC Medium Access Control
MAC-ID Medium Access Control interface Identifier
MF-SAP Management-Facilities SAP
MI-SAP Management-Interface SAP
MN-SAP Management-Networking and Transport SAP
NDL Network Design Limits
NT Networking and Transport
NT-ID Networking and Transport interface Identifier
OFDM Orthogonal Frequency Division Multiplexing
R/W Read/Write
RX Receiver
SAP Service Access Point
TC Traffic Class
TR Technical Report
TS Technical Specification
TX Transmitter
4 Introduction
The aim with the Decentralized Congestion Control (DCC) is to adapt the transmit parameters of the ITS station
(ITS-S) given the present radio channel conditions, in order to maximize the probability of a successful reception at
intended receivers.
The DCC attempts to provide equal access to the channel resources among neighbouring ITS-S. The channel resources
allotted by the DCC to the ITS-S should be distributed between the applications according to their needs. The ITS-S
determines priorities between different messages and discards messages if application requirements exceed allotted
resources (with the ITS-S applications' consent). In case of a situation of road traffic emergency even during a high
network utilization period, where every ITS-S has very few resources (e.g. CAM period at 1 Hz or 2 Hz), the ITS-S
may still transmit a burst of messages during a short period of time to maintain a safe road traffic environment.
However, this exception shall occur rarely and the messages transmitted for this purpose are only those of uttermost
importance.
The present document describes the cross-layer operation of the DCC mechanisms for ITS-S operating in the ITS-G5
band. It focuses on the DCC management functions in the DCC_CROSS entity and the corresponding internal functions
related to the different layers in the management entity as defined in ETSI TR 101 612 [i.1].
The present document specifies the functional behaviour and the interfaces of the DCC_CROSS component to control
the load on the active radio channels. Channel load limits are provided to accommodate this.
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11 ETSI TS 103 175 V1.1.1 (2015-06)
5 DCC architecture
5.1 Overview
ETSI EN 302 665 [6] provides the ITS reference architecture for an ITS-S. The present document provides details of
the DCC_CROSS entity residing in the management plane.
The DCC functionality, including interfaces mapped to the ITS-S architecture, is shown in Figure 1. It is distributed
between the following entities:
• DCC_FAC located in the facilities layer;
• DCC_NET located in the networking and transport layer as specified in ETSI TS 102 636-4-2 [4];
• DCC_ACC located in the access layer as specified in ETSI TS 102 687 [2];
• DCC_CROSS located in the management plane as specified in the present document.
The components are connected through the DCC interface 1 to interface 4 as shown in Figure 1. These interfaces are
compliant with ETSI TS 102 723-1 [5].

Figure 1: DCC Architecture
The DCC management entity (DCC_CROSS) in the management plane contains for each layer a function that is
connected to the interface towards the corresponding DCC entity in the communication stack.
In clauses 5.2 to 5.5, an overview of the four DCC entities is given. The corresponding cross-layer functionalities in the
management plane are addressed in clause 6 of the present document.
5.2 DCC_ACC
REQ001: The access layer of an ITS-S that transmits on an ITS-G5 radio channel shall include a DCC_ACC entity, as
specified in ETSI TS 102 687 [2], containing the access layer specific DCC functionalities such as those described in
Annex B.
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12 ETSI TS 103 175 V1.1.1 (2015-06)
5.3 DCC_NET
REQ002: If GeoNetworking over ITS-G5 is in place, as described in ETSI EN 302 636-4-1 [3], the network and
transport layer of an ITS-S that transmits on an ITS-G5 radio channel shall include the DCC_NET entity, specified in
ETSI TS 102 636-4-2 [4], which contains the networking & transport layer specific DCC functionalities such as those
described in Annex B. Otherwise, the usage of the DCC_NET entity is optional.
5.4 DCC_FAC
The facilities layer of an ITS-S optionally includes a DCC_FAC entity containing the facilities layer specific DCC
functionalities such as those described in Annex B.
5.5 DCC_CROSS
REQ003: The management plane of an ITS-S that transmits on an ITS-G5 radio channel shall include a DCC_CROSS
entity.
It contains the management specific DCC functionalities:
• DCC parameter evaluation. It computes the DCC internal parameters which indicate the available channel
resources based on CBR values collected by the CBR evaluation function (local CBR) and received by the
DCC_NET (highest global CBR value).
• DCC_CROSS_Access. It determines the DCC flow control and the DCC power control parameters for each
used radio channel based on the internal DCC parameters computed by the DCC parameter evaluation function
and provide them to the DCC_ACC entity.
• DCC_CROSS_Net. It returns to the DCC_NET the available resources per radio channel used.
• DCC_CROSS_Facilities. It uses internal DCC parameters from the DCC parameter evaluation function to
determine the available channel resource limit for the registered applications and basic facilities services. This
value is provided to the DCC_FAC entity.
6 DCC management entity
6.1 Overview
The DCC_CROSS entity is illustrated in the left side of Figure 2, configured for multi-channel operation and global
DCC information, as described in ETSI TR 101 612 [i.1]. The right part illustrates the functions in the data layers
interacting with the DCC_CROSS. For simplification of the figure, the DCC_ACC, DCC_NET, and DCC_FAC entities
introduced in clause 5 and located in the data plane are not pictured here.
ETSI
13 ETSI TS 103 175 V1.1.1 (2015-06)

Figure 2: Overview of the DCC in an ITS-S
Clause 6 provides functional requirements on the sub-components of the DCC_CROSS entity and a high level
description of its interfaces. The interfaces are described in more details in clause 8. The sub-components found in
DCC_CROSS are DCC parameter evaluation, DCC_CROSS_Access, DCC_CROSS_Net and DCC_CROSS_Facilities.
6.2 DCC parameter evaluation
Figure 3: DCC parameter evaluation function
ETSI
14 ETSI TS 103 175 V1.1.1 (2015-06)
REQ004: The DCC parameter evaluation function shall calculate the available channel resources to meet the
requirements as specified in clause 7.
REQ005: The DCC parameter evaluation function shall obtain the local CBR from the DCC_ACC entity specified in
ETSI TS 102 687 [2], and optionally obtain the global CBR from DCC_NET, for each radio channel used by the ITS-S.
REQ006: The local CBR value shall be provided by the DCC_ACC as a value between 0 and 1 for each given radio
channel used by the ITS-S. It shall represent the ratio between the channel active time and the measurement period of
100 ms. The channel active time is specified in ETSI TS 102 687 [2].
The local CBR is derived by the DCC_ACC from the measured CL value, as specified in ETSI TS 102 687 [2].
REQ007: When the global CBR is available, the DCC parameter evaluation function shall use the global CBR as input
for the DCC limits evaluation, as the measured local CBR is already taken into account in the global CBR described in
ETSI TS 102 636-4-2 [4]. Otherwise, the DCC parameter evaluation shall use the measured local CBR.
REQ008: The DCC parameter evaluation function shall provide the local CBR value, the CBR target value, and
optionally the TX power level upper limit of each individual used radio channel to the DCC_NET as described in
ETSI TS 102 636-4-2 [4].
REQ009: The CBR target value passed to the DCC_NET for the global CBR evaluation shall be set to 0,62. This is the
same value as the congestion threshold C used in Equation 1 in clause 7.2.
TH
REQ010: The DCC parameter evaluation function (DCC algorithm) shall provide as part of the internal DCC
parameters, the available CBR percentage per radio channel CBR . This value represents the upper limit of the time
a
fraction the ego ITS-S is allowed to transmit on the radio channel.
The output of the DCC parameter evaluation function is transferred to the DCC_CROSS Facilities, DCC_CROSS_Net
and DCC_CROSS_Access functions.
Parameters
• External interface from DCC_ACC (IM_SAP): local CBR for each radio channel used.
• External interface to DCC_NET (NM_SAP): local CBR, CBR target value, and optionally TX power level
upper limit (global DCC TX parameters shown in figure 3) for each radio channel used.
• External interface from DCC_NET (NM_SAP): global CBR for each used radio channel as described in
ETSI TS 102 636-4-2 [4] (global DCC RX parameters shown in figure 3).
• Internal usage to other DCC_CROSS functions: available CBR percentage CBR per radio channel for one
a
ITS-S (internal DCC parameters shown in figure 3).
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15 ETSI TS 103 175 V1.1.1 (2015-06)
6.3 DCC_CROSS_Access
Figure 4: DCC_CROSS_Access function
REQ011: The specified DCC_CROSS_Access function shall be implemented in every ITS-S that is sending messages
on an ITS-G5 radio channel.
REQ012: The DCC_CROSS_Access function shall provide the idle time T per radio channel to the DCC_ACC (DCC
off
flow control parameters as shown in figure 4) and, if GeoNetworking over ITS-G5 [3] is used, within the management
plane to the DCC_CROSS_Net function.
REQ013: DCC_ACC shall provide the length of all transmitted messages (air time per radio channel) T to the
on
DCC_CROSS_Access function.
REQ014: The DCC_CROSS_Access function shall retrieve the available CBR percentage per radio channel CBR from
a
the DCC parameter evaluation function (DCC algorithm) for each used radio channel as defined in clause 6.2.
REQ015: The value of T shall be calculated according to: T = T × ((1 - CBR ) / CBR )
off off on a a
REQ016: When DCC power control is implemented, the DCC_CROSS_Access function shall provide the DCC power
control parameters shown in figure 4 containing an upper TX power level limit to the DCC_ACC for each used radio
channel.
REQ017: If GeoNetworking over ITS-G5 in accordance with ETSI EN 302 636-4-1 [3] is used, the
DCC_CROSS_Access function shall receive from the DCC_ACC the time when the last message was forwarded to the
ITS-G5 radio and provide it to the DCC_CROSS_Net function.
NOTE: This is a general requirement, supporting forwarding algorithms in ETSI EN 302 636-4-1 [3].
Once the system operates under high channel load conditions it may happen that some packets have to be dropped in the
access layer queues. In the present document, there is no mandatory function to report back that packets have been
dropped.
Parameters
• External interface from DCC_ACC (IM_SAP): length of all transmitted messages (air time) T time when the
on,
last message was forwarded to the ITS-G5 radio.
• External interface to DCC_ACC (IM_SAP): idle time T and upper TX power level limit per given channel
off
used.
• Internal usage from DCC parameter evaluation function: available CBR percentage per radio channel, CBR
a
(internal DCC parameters shown in figure 4, as defined in clause 6.2.
ETSI
16 ETSI TS 103 175 V1.1.1 (2015-06)
• Internal usage to DCC_CROSS_Net function: idle time T per radio channel and time when the last message
off
was forwarded to the ITS-G5 radio.
6.4 DCC_CROSS_Net
Figure 5: DCC_CROSS_Net function
REQ018: If GeoNetworking over ITS-G5 in accordance with ETSI EN 302 636-4-1 [3] is used at the networking and
transport layer, then the implementation of DCC_CROSS_Net is mandatory. Otherwise, the implementation of the
DCC_CROSS_Net function is optional.
REQ019: When present, the DCC_CROSS_Net shall disseminate to the DCC_NET the idle time T per radio channel
off
and optionally, the CBR , i.e. the available resources that can be allocated per radio channel and, if available, the time
a
when the last message was forwarded to the ITS-G5 radio.
Parameters
• External interface to DCC_NET (NM_SAP): idle time T per radio channel and optionally, CBR and time
off a
when the last message was forwarded to the ITS-G5 radio (DCC channel resources parameters shown in
figure 5).
• Internal usage from DCC parameter evaluation function: available CBR percentage per radio channel CBR
a
(internal DCC parameters shown in figure 5), as defined in clause 6.2.
• Internal usage from DCC_CROSS_Access function: idle time Toff per radio channel, time when the last
message was forwarded to the ITS-G5 radio.
6.5 DCC_CROSS_Facilities
Figure 6: DCC_CROSS_Facilities function
The implementation of a DCC_CROSS_Facilities function is optional. When implemented, its purpose is the reduction
of the message rate already at generat
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