ETSI TS 102 636-4-2 V1.1.1 (2013-10)

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

DTS/ITS-0030007

General Information

• Status: Published
• Publication Date: 27-Oct-2013
• Technical Committee: ITS WG3 - Transport and Network
• Current Stage: 12 - Completion
• Due Date: 22-Nov-2013
• Completion Date: 28-Oct-2013
• Mandate: M/453

Standards Content (Sample)

ETSI TS 102 636-4-2 V1.1.1 (2013-10)






Technical Specification
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

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2 ETSI TS 102 636-4-2 V1.1.1 (2013-10)



Reference
DTS/ITS-0030007
Keywords
addressing, ITS, network, point-to-multipoint,
point-to-point, protocol
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3 ETSI TS 102 636-4-2 V1.1.1 (2013-10)
Contents
Intellectual Property Rights . 4
Foreword . 4
Introduction . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 5
3 Definitions, symbols and abbreviations . 6
3.1 Definitions . 6
3.2 Symbols . 6
3.3 Abbreviations . 6
4 Overview . 8
5 Information sharing for decentralized congestion control . 9
5.1 Introduction . 9
5.2 Information sharing . 10
5.2.1 General rules . 10
5.2.2 CBR aggregation . 10
5.2.3 Sending process . 12
5.2.4 Receiving process . 12
5.2.5 Algorithm for CBR information sharing . 12
6 Location table extensions for ITS-G5 . 13
6.1 Location table entry extensions . 13
6.1.1 Additional data elements for the location table entry . 13
6.1.2 Specific maintenance of the location table entry . 13
7 Field settings in the GeoNetworking header for ITS-G5 usage . 14
7.1 Overview . 14
7.2 Field settings in the Common Header . 14
7.3 Field settings in the Extended Header . 15
8 Traffic classes for ITS-G5 . 16
Annex A (informative): Multichannel operation . 17
A.1 Introduction . 17
A.2 Single transceiver ITS-S on ITS-G5 . 17
A.2.1 Safety-related context . 17
A.2.2 Non safety-related context . 18
A.3 Multi-transceiver ITS-S on ITS-G5 . 18
A.3.1 General . 18
A.3.2 Multi-Channel Operation for service management . 18
A.3.3 Multichannel in safety-related context for ITS-G5 . 19
A.4 TX/RX synchronization . 20
A.4.1 Single transceiver (outside the safety-related context) . 20
A.4.2 Multi-transceiver . 20
Annex B (informative): DSRC Interference Mitigation . 21
Annex C (informative): ITS-G5 extensions to GeoNetworking NDL parameters . 23
Annex D (informative): Bibliography . 24
History . 25
ETSI

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4 ETSI TS 102 636-4-2 V1.1.1 (2013-10)
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).
The present document is part 4, sub-part 2 of a multi-part deliverable. Full details of the entire series can be found in
part 1 [i.1].
Introduction
The GeoNetworking protocol is a network layer protocol that provides packet routing in an ad hoc network. It makes
use of geographical positions for packet transport. GeoNetworking supports the communication among individual
ITS-Ss as well as the distribution of packets in geographical areas.
GeoNetworking can be executed over different ITS access technologies for short-range wireless technologies, such as
ITS-G5. In order to reuse the GeoNetworking protocol specification for multiple ITS access technologies, the
specification is separated into media-independent and media-dependent functionalities. Media-independent
GeoNetworking functionalities are those which are common to all ITS access technologies for short-range wireless
communication and are specified in EN 302 636-4-1 [1]. The present document specifies media-dependent
functionalities for GeoNetworking when using the ITS access technology ITS-G5 [2]. It covers an information sharing
strategy for the decentralized congestion control (which is situated in the ITS access layer) and it provides multichannel
operation.
The specification in the present document should be regarded as ITS-G5 specific extensions of the GeoNetworking
protocol specified in [1] and does not represent a distinct protocol entity.
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5 ETSI TS 102 636-4-2 V1.1.1 (2013-10)
1 Scope
The present document specifies the media-dependent functionalities for GeoNetworking [1] over ITS-G5 [2] as a
network protocol for ad hoc routing in vehicular environments.
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
referenced 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.
[1] ETSI EN 302 636-4-1 (V1.2.0): "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".
[2] ETSI EN 302 663 (V1.2.1): "Intelligent Transport Systems (ITS); Access layer specification for
Intelligent Transport Systems operating in the 5 GHz frequency band".
[3] 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".
[4] ETSI TS 102 792 (V1.1.1): "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".
[5] ETSI TS 102 724: "Intelligent Transport Systems (ITS); Harmonized Channel Specifications for
Intelligent Transport Systems operating in the 5 GHz frequency band".
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] ETSI EN 302 636-1 (V1.2.0): "Intelligent Transport Systems (ITS); Vehicular Communications;
GeoNetworking; Part 1: Requirements".
[i.2] ETSI EN 302 665 (V1.1.1): "Intelligent Transport Systems (ITS); Communications Architecture".
[i.3] ETSI EN 302 571 (V1.2.1): "Intelligent Transport Systems (ITS); Radio communications
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.4] IEEE Vehicular Networking Conference (VNC) (2011): "Design Methodology and Evaluation of
Rate Adaptation Based Congestion Control for Vehicle Safety Communications", pp. 116 -123,
T. Tielert, D. Jiang, Q. Chen, L. Delgrossi and H. Hartenstein.
[i.5] IEEE Std. 802.11-2012: "Part 11: Wireless LAN Medium Access Control (MAC) and Physical
Layer (PHY) specifications", March 2012.
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6 ETSI TS 102 636-4-2 V1.1.1 (2013-10)
[i.6] IEEE 1609.4-2010: "IEEE Standard for Wireless Access in Vehicular Environments (WAVE)--
Multi-channel Operation".
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in EN 302 636-4-1 [1], EN 302 663 [2],
TS 102 687 [3], TS 102 792 [4], TS 102 724 [5] and the following apply:
channel busy ratio: time-dependent value between zero and one (both inclusive) representing the fraction of time that
the channel was busy
local channel busy ratio: time-dependent value between zero and one (both inclusive) representing the channel busy
ratio as perceived locally by a specific ITS station
1-hop channel busy ratio: highest local channel busy ratio that the ego ITS station has received from its 1-hop
neighbourhood over a certain time
2-hop channel busy ratio: highest 1-hop channel busy ratio that the ego ITS station has received from its 1-hop
neighbourhood over a certain time
global channel busy ratio: maximum of the local channel busy ratio, the 1-hop channel busy ratio and the 2-hop
channel busy ratio
3.2 Symbols
For the purposes of the present document, the symbols given in EN 302 636-4-1 [1], EN 302 663 [2], TS 102 687 [3],
TS 102 792 [4], TS 102 724 [5] and the following apply:
CBR_L_0_Hop Local channel busy ratio for a specific frequency channel for ego ITS station
CBR_L_1_Hop Highest received value of CBR_R_0_Hop
CBR_L_2_Hop Highest received value of CBR_R_1_Hop
CBR_R_0_Hop Local channel busy ratio CBR_L_0_Hop disseminated in single-hop broadcast packets
CBR_R_1_Hop Highest received CBR_L_1_Hop disseminated in single-hop broadcast packets
CBR_target Intended global channel busy ratio
CBR_G Global Channel Busy Ratio for a specific frequency channel
PHY-S ITS-S tuned on SCHs and operating in non-safety-related context
PHY-C ITS-S tuned on CCH and operative in safety-related context
T_cbr Lifetime of the channel busy ratio
T_trig Trigger interval
T_duty Multi-channel switching duty cycle
T_SCH1 Reference channel returning period
T_Safety Phase, where an MCO-capable ITS-S is on PHY-C
T_Service Phase, where an MCO-capable ITS-S is on PHY-S
T_mon Minimum CBR monitoring interval as specified in [3]
t_offset Offset time for the reference channel returning period
3.3 Abbreviations
For the purposes of the present document, the abbreviations given in EN 302 636-4-1 [1], EN 302 663 [2],
TS 102 687 [3], TS 102 792 [4], TS 102 724 [5] and the following apply:
AC Access Category
AC_BE AC Best Effort
AC_BK AC BacKground
AC_VI AC VIdeo
AC_VO AC VOice
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7 ETSI TS 102 636-4-2 V1.1.1 (2013-10)
AIFS Arbitration InterFrame Space
BUSY Busy Mode
CAM Cooperative Awareness Message
CBR Channel Busy Ratio
CCF Channel Configuration Function
CCH Control CHannel
CEN Comité Européen de Normalisation
C-ITS Cooperative ITS
CSF Channel Switching Function
CW Contention Window
DCC Decentralized Congestion Control
DENM Decentralized Environmental Notification Message
DSRC Dedicated Short Range Communication
ETC Electronic Toll Collection
GN GeoNetworking
HST Header Sub-Type
HT Header Type
IN-SAP interface between access layer and network & transport layer
ITS Intelligent Transport Systems
ITS-S ITS Station
LocTE Location Table Entry
LocTEX Location Table Entry Extension
MAC Medium Access Control
MAP road map message
MCO Multi Channel Operations
MCS Modulation and Coding Scheme
MHL Maximum Hop Limit
MIB Management Information Base
MN-SAP Interface between management and network & transport layer
NDL Network Design Limits (DCC management information base)
NF-SAP Interface between networking & transport and facilities layer
NH Next Header
OBU On-Board Unit
PHY PHYsical layer
PHY-C ITS G5 transceiver tuned on CCH
PHY-S ITS-G5 transceiver tuned on any channel
PL Payload Length
POS Position
PV Position Vector
RSSI Received Signal Strength Indicator
RSU Road Side Unit
RX Receiver
SAM Service Announcement Message
SAP Service Access Point
SCF Store Carry Forward
SCH Service CHannel
SHB Single-Hop Broadcast
SO Source
SW Switching mode
TC Traffic Class
TC ID Traffic Class IDentity
TOPO road topology message
TST Time STamp
TX Transmitter
TX/RX transmit / receive
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8 ETSI TS 102 636-4-2 V1.1.1 (2013-10)
4 Overview
The present document specifies the media-dependent functionalities necessary to run the GeoNetworking protocol [1]
over ITS-G5 media [2]. The functionalities are:
• information sharing for Decentralized Congestion Control (DCC) (clause 5);
• support for multi-channel operation (annex A);
• interference mitigation techniques for co-existence between CEN DSRC and cooperative ITS (annex B).
Additionally, the present document specifies extensions to the GeoNetworking location table (clause 6), to the
GeoNetworking header (clause 7) and to the GeoNetworking MIB (clause 9). Clause 8 specifies the traffic classes (TC)
used for ITS-G5.
Figure 1 illustrates the ITS reference architecture as specified in [i.2]. The present document specifies ITS-G5 specific,
media-dependent functionalities for the GeoNetworking protocol, which are found in the ITS networking & transport
layer.

Figure 1: ITS-S reference architecture as specified in [i.2]
DCC is a necessity to control the load on a specific frequency channel and to avoid unstable behaviour. As specified in
[i.3], several different frequency channels are available for Cooperative ITS (C-ITS) in Europe. Figure 2 illustrates the
frequency channels together with their maximum allowed output power levels [i.3]. The spectrum comprises of four
service channels (SCHx) and one control channel (CCH). The frequency band ITS-G5A contains frequency channels
CCH, SCH1, and SCH2, which are intended for ITS road safety related applications. SCH3 and SCH4 are contained in
the frequency band ITS-G5B and are intended for ITS non-safety applications. ITS-G5D is for future use and not yet
allocated for C-ITS. The present document addresses information sharing to be used in the DCC algorithm for the
access layer technology ITS-G5, which primarily uses the frequency bands ITS-G5A, ITS-G5B, and ITS-G5D.
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9 ETSI TS 102 636-4-2 V1.1.1 (2013-10)

Figure 2: Maximum limit of mean spectral power density for each channel in ITS-G5A,
ITS-G5B, and ITS-G5D as specified in [i.3]
5 Information sharing for decentralized congestion
control
5.1 Introduction
This clause specifies an information sharing concept for the DCC algorithm situated in the ITS access layer [3]. The
DCC algorithm controls the network load and thereby avoids unstable behaviour of the system due to its ad hoc
topology [3]. The information sharing is based on dissemination of channel busy ratio (CBR) values among the ITS-Ss.
This dissemination of CBR values makes the ITS-S aware of a possible channel congestion at neighbouring ITS-Ss that
the ego ITS-S can contribute to (even though the ego ITS-Ss does not perceive a local congested channel status). More
information about the CBR information dissemination and motivation of thereof is found in [i.4]. The obvious place for
CBR dissemination is at the network & transport layer due to its network wide view. The dissemination of CBR values
are conducted in every transmitted Single Hop Broadcast (SHB) packet assembled at the networking & transport layer,
see clause 7. For every entry of an ITS-S in the location table [1], there will also be information about its transmitted
CBR values.
Additionally, the algorithm to ensure coexistence between CEN DSRC equipment used for Electronic Toll Collection
(ETC) and ITS described in TS 102 792 [4] belongs to the networking & transport layer (due to the network wide view
and the placement of the location table). Depending on whether the placement of the CEN DSRC equipment on the
roadside is known or unknown, the combination of the DCC concept and the coexistence algorithm looks different.
Proposed implementation details for coexistence methods are given in informative annex B.
The information sharing shall provide a parameter called CBR_G to the management entity. This parameter is used by
the DCC algorithm in the ITS access layer when calculating the current allowed time between packets [3]. The
information sharing shall read the local CBR from the management via a parameter called CBR_L_0_Hop. The value of
CBR_L_0_Hop is disseminated in SHB packets. More information about the inclusion of CBR values at the networking
& transport layer can be found in clause 5.2.3. A schematic overview of the information sharing together with DCC in
the protocol stack is depicted in figure 3. The exchange of CBR_G and CBR_L_0_Hop could also be performed via the
service access point (SAP) between the access and networking & transport layers.
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10 ETSI TS 102 636-4-2 V1.1.1 (2013-10)
Networking & transport
CBR_G
CBR dissemination
CBR_L_0_Hop
s
Management
CBR_G
CBR_L_0_Hop
Access
s
CBR_L_0_Hop
DCC
s
CBR_G

Figure 3: Overview of the information sharing together
with the placement of DCC in the protocol stack
5.2 Information sharing
5.2.1 General rules
The information sharing is subject to the following general rules:
• The inclusion of CBR values shall be performed in each GN SHB packet.
• The calculation of CBR_G shall be activated at every trigger interval, T_trig.
5.2.2 CBR aggregation
The CBR dissemination and aggregation are central in DCC since this is regarded as the best feedback that can be used
in C-ITS, where broadcast is the prevalent transmission mode (see also [i.4]).
The CBR aggregation is dependent upon the following CBR parameters:
• CBR_L_0_Hop,
• CBR_L_1_Hop,
• CBR_L_2_Hop,
• CBR_R_0_Hop,
• CBR_R_1_Hop, and
• CBR_G.
The CBR parameters are described in detail in table 1.
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11 ETSI TS 102 636-4-2 V1.1.1 (2013-10)
Table 1: Description of necessary CBR parameters for DCC algorithm
Parameter Description
Local (measured) channel busy ratio, disseminated to neighbouring ITS-S as CBR_R_0_Hop.The
CBR_L_0_Hop
local CBR measurement is performed in the access layer and specified in [3].
CBR_L_1_Hop is the maximum CBR_R_0_Hop value received from a neighbouring ITS-S in a
CBR_L_1_Hop given T_cbr interval, i.e. it is the 1-hop channel busy ratio. It is subsequently disseminated to
neighbours as CBR_R_1_Hop.
CBR_L_2_Hop is the maximum CBR_R_1_Hop value received from a neighbouring ITS-S in a
CBR_L_2_Hop
given T_cbr interval, i.e. it is the 2-hop channel busy ratio. It is never disseminated by ego ITS-S.
Disseminated local (measured) channel busy ratio (CBR_L_0_Hop), i.e. CBR_L_0_Hop becomes
CBR_R_0_Hop
CBR_R_0_Hop when disseminated. At receiving ITS-S it becomes CBR_L_1_Hop.
Disseminated 1-hop channel busy ratio (CBR_L_1_Hop), i.e. CBR_L_1_Hop becomes
CBR_R_1_Hop
CBR_R_1_Hop when disseminated. At receiving ITS-S it becomes CBR_L_2_Hop.
Global channel busy ratio at ego ITS-S, used in the DCC algorithm (maximum over
CBR_G
CBR_L_0_Hop, CBR_L_1_Hop and CBR_L_2_Hop).
In control theory called reference value. It is the intended global channel busy ratio that DCC tries
to achieve. The CBR_target shall be one common parameter for both the access layer and the
CBR_target
network and transport layer DCC algorithm (e.g. shared as constant MIB parameter – see
Annex C).

For every ITS-S, i, in the location table:
• CBR_R_0_Hop(i) is the remote CBR_L_0_Hop received from i,
• CBR_R_1_Hop(i) is the remote CBR_L_1_Hop received from i.
A plausibility check shall be performed when calculating CBR_L_1_Hop and CBR_L_2_Hop from the maximum value
of CBR_R_0_Hop(i) and CBR_R_1_Hop(i), since the highest received value could come from a faulty chipset or
malicious sources. The plausibility check shall be performed as follows:
• If the CBR_L_1_Hop is larger than CBR_target and the average of all CBR_R_0_Hop(i) is smaller than
CBR_target, take the second largest entry found for CBR_R_0_Hop(i); otherwise take the largest entry.
• If the CBR_L_2_Hop is larger than CBR_target and the average of all CBR_R_1_Hop(i) is smaller than
CBR_target, take the second largest entry found for CBR_R_1_Hop(i); otherwise take the largest entry.
Following this procedure the 1-hop channel busy ratio CBR_L_1_Hop shall be calculated according to equation (2)
when the average of CBR_R_0_Hop(i), i.e. , from equation (1) is bigger than CBR_target.
CBR__R 0_ Hop
1
 (1)
CBR__R 0_ Hop=∀CBR_ R_0_ Hop iiRwhereCB _R_0_Hopi is not older than _T cbr
() ()
∑
n
i
0
In equation (1), n is the total number of the CBR_R_0_Hop entries that are not outdated (older than T_cbr).
0
When
CBR__R 0_ Hop > CBR_ target
CBR_L_1_Hop := max { CBR_R_0_Hop (i) } during the last CBR lifetime T_cbr, (2)
i
otherwise CBR_L_1_Hop shall be set to the second largest CBR_R_0_Hop (i) during the last CBR lifetime T_cbr.

Accordingly, the 2-hop channel busy ratio CBR_L_2_Hop shall be calculated by equation (4) when the average of
CBR_L_1_Hop, i.e. , from equation (3) is bigger than CBR_target.
CBR__R 1_ Hop
1
 (3)
CBR__R 1_ Hop=∀CBR_ R _1_ Hop iiRwhereCB _R _1_Hopi is not older than _T cbr
() ( )
∑
n
i
1
In equation (3), n is the total number of the CBR_R_1_Hop entries that are not outdated (older than T_cbr).
1
When , CBR_L_2_Hop shall be calculated by
CBR__R 1_ Hop > CBR_ target
CBR_L_2_Hop := max { CBR_R_1_Hop (i) } during the last CBR lifetime T_cbr (4)
i
otherwise CBR_L_2_Hop shall be set to the second largest CBR_R_1_Hop (i) during the last CBR lifetime T_cbr.

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12 ETSI TS 102 636-4-2 V1.1.1 (2013-10)
The global channel busy ratio CBR_G(n) after the nth trigger interval, T_trig, is calculated as specified in equation (5).
CBR_G (n) = max ( CBR_L_0_Hop (n-1), CBR_L_1_Hop (n), CBR_L_2_Hop (n) ) (5)
The initial values are CBR_L_1_Hop(0) = 0 and CBR_L_2_Hop(0) = 0.
The CBR_G value is the input to the DCC algorithm running at the access layer as specified in [3].
5.2.3 Sending process
ITS-Ss executing the GeoNetworking protocol over ITS-G5 shall include the following DCC information in every
transmitted SHB packet:
• the most recently obtained value CBR_L_0_Hop;
• the most recently calculated value CBR_L_1_Hop.
Further details are specified in clauses 6 and 7 of the present document.
5.2.4 Receiving process
Upon reception of a SHB packet from a remote ITS-S, an ITS-S shall update the loca
...