ETSI TS 102 636-4-2 V1.3.1 (2020-08)

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

RTS/ITS-00365

General Information

• Status: Not Published
• Technical Committee: ITS WG3 - Transport and Network
• Current Stage: 12 - Completion
• Due Date: 07-Aug-2020
• Completion Date: 04-Aug-2020

Standards Content (Sample)

ETSI TS 102 636-4-2 V1.3.1 (2020-08)






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 V1.3.1 (2020-08)



Reference
RTS/ITS-00365
Keywords
addressing, ITS, network, point-to-multipoint,
point-to-point, protocol
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3 ETSI TS 102 636-4-2 V1.3.1 (2020-08)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 4
Introduction . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 5
3 Definition of terms, symbols and abbreviations . 6
3.1 Terms . 6
3.2 Symbols . 6
3.3 Abbreviations . 7
4 Overview . 7
5 DCC functionality at networking & transport layer (DCC_NET) for ITS-G5 . 8
5.1 General . 8
5.2 Maintenance of DCC variables . 9
5.3 Calculation of the global channel busy ratio CBR_G . 10
5.4 DCC_NET . 10
6 Addressing, data structure extensions and field settings for ITS-G5 . 11
6.1 GeoNetworking address . 11
6.2 Location table extensions for ITS-G5 . 11
6.2.1 General . 11
6.2.2 Definition of additional data elements for the location table entry . 11
6.2.3 Maintenance of additional data elements for the location table entry . 12
6.3 Field settings in the GeoNetworking header . 12
6.3.1 General . 12
6.3.2 Field settings in the Common Header . 13
6.3.3 Field settings in the Extended Header of the SHB packet . 13
6.4 EtherType . 14
7 Extensions of packet handling algorithms for ITS-G5 . 14
7.1 General . 14
7.2 Extensions of SHB packet handling . 14
7.2.1 Extensions for source operations . 14
7.2.2 Extensions for receiver operations . 15
8 Mapping of traffic classes to transmission parameters for ITS-G5 . 15
Annex A (normative): GeoNetworking protocol constants for ITS-G5 . 16
Annex B (informative): Extensions of the GeoNetworking MIB . 17
Annex C (informative): Extensions of forwarding algorithms for ITS-G5 . 18
C.1 General . 18
C.2 Enhancements of non-area and area Contention-Based Forwarding (CBF) algorithms . 19
Annex D (informative): Bibliography . 20
History . 21

ETSI

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4 ETSI TS 102 636-4-2 V1.3.1 (2020-08)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables 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 (https://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.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
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].
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.
Introduction
The GeoNetworking protocol is a network 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 ETSI EN 302 636-4-1 [1]. The present document specifies media-dependent
functionalities for GeoNetworking when using the ITS access technology ITS-G5 (see ETSI EN 302 663 [2]). The
specification in the present document should be regarded as ITS-G5 specific extensions of the GeoNetworking protocol
specified in ETSI EN 302 636-4-1 [1] and does not represent a distinct protocol entity.
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5 ETSI TS 102 636-4-2 V1.3.1 (2020-08)
1 Scope
The present document specifies the media-dependent functionalities for GeoNetworking defined in ETSI
EN 302 636-4-1 [1] over ITS-G5 defined in ETSI EN 302 663 [2] as a network protocol for ad hoc routing in vehicular
environments.
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
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://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] ETSI EN 302 636-4-1 (V1.4.1): "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".
[2] ETSI EN 302 663 (V1.3.1): "Intelligent Transport Systems (ITS); ITS-G5 Access layer
specification for Intelligent Transport Systems operating in the 5 GHz frequency band".
[3] ETSI TS 103 175 (V1.1.1): "Intelligent Transport Systems (ITS); Cross Layer DCC Management
Entity for operation in the ITS G5A and ITS G5B medium".
[4] ETSI TS 102 687 (V1.2.1): "Intelligent Transport Systems (ITS); Decentralized Congestion
Control Mechanisms for Intelligent Transport Systems operating in the 5 GHz range; Access layer
part".
[5] ETSI TS 103 301 (V1.3.1): "Intelligent Transport Systems (ITS); Vehicular Communications;
Basic Set of Applications; Facilities layer protocols and communication requirements for
infrastructure services".
®
[6] Car-2-Car Communication Consortium Version 1.5: "Basic System Profile".
NOTE: Available at https://www.car-2-car.org/documents/basic-system-profile.
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] ETSI EN 302 636-1 (V1.2.1): "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".
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6 ETSI TS 102 636-4-2 V1.3.1 (2020-08)
[i.3] ETSI EN 302 571 (V2.1.1): "Intelligent Transport Systems (ITS); Radiocommunications
equipment operating in the 5 855 MHz to 5 925 MHz frequency band; Harmonised Standard
covering the essential requirements of article 3.2 of Directive 2014/53/EU".
TM
[i.4] IEEE 802.11 -2016: "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".
TM
[i.5] IEEE Registration Authority.
NOTE: Available at https://standards.ieee.org/content/ieee-standards/en/products-services/regauth/index.html.
TM
[i.6] List of assigned EtherTypes at the IEEE Registration Authority.
NOTE: Available at http://standards-oui.ieee.org/ethertype/eth.txt.
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the terms given in ETSI EN 302 636-4-1 [1], ETSI EN 302 663 [2], ETSI
TS 103 175 [3], ETSI TS 102 687 [4] and the following apply:
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
channel busy ratio: time-dependent value between zero and one (both inclusive) representing the fraction of time that
the channel was busy
global channel busy ratio: maximum of the local channel busy ratio, the 1-hop channel busy ratio and the 2-hop
channel busy ratio
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
3.2 Symbols
For the purposes of the present document, the symbols given in ETSI EN 302 636-4-1 [1], ETSI EN 302 663 [2], ETSI
TS 103 175 [3], ETSI TS 102 687 [4] 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
T_Cbr Lifetime of the channel busy ratio
T_Trig Trigger interval to update CBR_G
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7 ETSI TS 102 636-4-2 V1.3.1 (2020-08)
3.3 Abbreviations
For the purposes of the present document, the abbreviations given in ETSI EN 302 636-4-1 [1], ETSI EN 302 663 [2],
ETSI TS 103 175 [3], ETSI TS 102 687 [4] and the following apply:
LocTEX Location Table Entry eXtension
4 Overview
The present document specifies the media-dependent functionalities necessary to run the GeoNetworking protocol
defined in ETSI EN 302 636-4-1 [1] over the ITS-G5 access technology defined in ETSI EN 302 663 [2]. The
functionalities are:
• Decentralized congestion control (DCC) at the networking & transport layer for the ITS-G5 access technology,
specifically information sharing for DCC (DCC_NET) (clause 5).
• Addressing, data structure extensions and field settings in the GeoNetworking headers for ITS-G5 (clause 6).
• Extensions for packet handling of the GeoNetworking protocol for ITS-G5 (clause 7).
• Mapping of traffic classes to transmission parameters for ITS-G5 (clause 8).
The present document also proposes extensions for forwarding algorithms of the GeoNetworking protocol for ITS-G5
(annex C).
Figure 1 illustrates the ITS reference architecture as specified in ETSI EN 302 665 [i.2]. The present document specifies
ITS-G5 specific, media-dependent functionalities for the GeoNetworking protocol, which are found in the networking
& transport layer.

Figure 1: ITS-S reference architecture as specified in ETSI EN 302 665 [i.2]
A GeoNetworking packet transmitted over the ITS-G5 access technology is part of the overall frame/packet structure
depicted in figure 2 (without security) and figure 3 (with security), respectively:
1) The MAC header is the header of the MAC protocol of the ITS-G5 access technology. The MAC protocol
adds an additional protocol element for the trailer for the MAC FCS as specified in ITS-G5 defined in ETSI
EN 302 663 [2].
NOTE 1: The MAC header is not specified by the present document. However, the GeoNetworking protocol sets
the MAC address, or more generally the link layer address, in order to define and identify the next hop of
a GeoNetworking packet.
2) The LLC header is the header of 802.2 LLC (see ETSI EN 302 663 [2]).
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8 ETSI TS 102 636-4-2 V1.3.1 (2020-08)
3) The GeoNetworking header is the header of the GeoNetworking packet as defined in ETSI EN 302 636-4-1 [1]
extended for media-dependent GeoNetworking functionality over ITS-G5 as specified in the present
document.
4) The optional payload represents the user data that are created by upper protocol entities, i.e. the T-SDU or
GN6-SDU. It is passed to the GeoNetworking protocol for transmission.
NOTE 2: The general packet structure is shown as seen by the MAC protocol of the ITS-G5 access technology.
NOTE 3: Some GeoNetworking packets do not carry a payload, such as Beacon.
MAC GeoNetworking Payload
LLC Header
Header Header (optional)

Figure 2: GeoNetworking packet structure over ITS-G5 (without security)

GeoNetworking GeoNetworking Secured Packet
MAC
LLC Header Basic with Common Header, Optional Extended Header and
Header
Header Optional Payload

Figure 3: GeoNetworking packet structure over ITS-G5 (with security)
5 DCC functionality at networking & transport layer
(DCC_NET) for ITS-G5
5.1 General
An ITS-S operating the ITS-G5 access technology supports Decentralized Congestion Control (DCC) to ensure that the
radio channel is not congested by too many transmissions within a certain geographical range (see ETSI
EN 302 571 [i.3]. As specified in ETSI TS 103 175 [3], clause 5 "DCC architecture", the DCC functionality is
distributed among the entities DCC_FAC, DCC_NET, DCC_ACC and DCC_CROSS at the different layers and entities
of the ITS reference architecture (see figure 4).

Figure 4: DCC architecture as specified in ETSI TS 103 175 [3]
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9 ETSI TS 102 636-4-2 V1.3.1 (2020-08)
The GeoNetworking protocol (see ETSI EN 302 636-4-1 [1]) over the ITS-G5 access technology (see ETSI
EN 302 663 [2]) provides the DCC functionality over ITS-G5 access technology (DCC_NET). DCC_NET shall support
the following functionality:
• maintain DCC state variables as specified in clause 5.2;
• periodically calculate the global Channel Busy Ratio CBR_G as specified in clause 5.3;
• process and provide DCC-related information to the DCC_CROSS entity as specified in clause 5.4;
• store and maintain DCC-related information using the Location Table Entry Extension for ITS-G5
(LocTEX-G5) as specified in clause 6.2;
• transmit and receive DCC-related information to other GeoNetworking routers using the extensions for
GeoNetworking packet handling as specified in clause 7.2.
In addition, DCC_NET may provide DCC-related information to the GN forwarding algorithm as specified in annex C.
5.2 Maintenance of DCC variables
If DCC_NET is present, it shall maintain the following DCC variables:
• CBR_L_0_Hop,
• CBR_L_1_Hop,
• CBR_L_2_Hop,
• CBR_R_0_Hop,
• CBR_R_1_Hop,
• CBR_G, and
• CBR_Target.
The CBR variables are described in detail in table 1.
Table 1: Description of DCC variables in DCC_NET
Parameter Description
Measured local channel busy ratio CBR, disseminated to neighbouring ITS-S as
CBR_L_0_Hop CBR_R_0_Hop.The local CBR measurement is performed in the access layer and specified in
ETSI TS 102 687 [4].
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 calculated locally and not
disseminated directly by an ITS-S.
Disseminated (measured) local 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 the 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 the 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), see clause 5.3.
Intended global channel busy ratio that DCC tries to achieve. CBR_Target is constant and its
CBR_Target
value shall be the same at DCC_NET and DCC_ACC.

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10 ETSI TS 102 636-4-2 V1.3.1 (2020-08)
The DCC variables CBR_R_0_Hop and CBR_R_1_Hop are per ITS-S in the location table (see clause 6.2 "Location
table extensions for ITS-G5" in the present document), i.e. 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.
5.3 Calculation of the global channel busy ratio CBR_G
To calculate CBR_G, the following steps shall be executed at every T_Trig:
The value of T_Trig equals the GeoNetworking protocol constant itsGNCBRGTriggerInterval. Within the
trigger interval T_Trig, all ITS-S shall start with a random time offset.
The values of CBR_L_1_Hop(0) and CBR_L_2_Hop(0) shall be initialized to 0.
NOTE: The time offset prevents that all ITS-Ss to trigger the calculation of CBR_G at the same time.
Step 1: Calculate the average of CBR_R_0_Hop(i), i.e. (1)
1
CBR__R 0_ Hop=∀CBR_ R_0_ Hop()iiRwhereCB _R_0_Hop(i)is not older than _T cbr

n
i
0

where n is the total number of the CBR_R_0_Hop entries that are not outdated (older than T_Cbr)
0
Step 2: (2)
If CBR__R 0_ Hop > CBR_ target
CBR_L_1_Hop := max { CBR_R_0_Hop (i) } during the last CBR lifetime T_Cbr
i
Else
Set CBR_L_1_Hop to the second largest CBR_R_0_Hop (i) during the last CBR lifetime T_Cbr

Step 3: Calculate the average of CBR_R_1_Hop(i), i.e. (3)
1
CBR__R 1_ Hop=∀CBR_ R _1_ Hop iiRwhereCB _R _1_Hopi is not older than _T cbr
() ()

n
i
1

where n is the total number of the CBR_R_1_Hop entries that are not outdated (older than T_Cbr)
0
Step 4: (4)
CBR _ R _1_ Hop > CBR _ target
If
CBR_L_1_Hop := max { CBR_R_0_Hop (i) } during the last CBR lifetime T_Cbr
i
Else
Set CBR_L_1_Hop to the second largest CBR_R_0_Hop (i) during the last CBR lifetime T_Cbr

Calculate the global channel busy ratio CBR_G (5)
Step 5:
CBR_G(n) CBR_G (n) = max ( CBR_L_0_Hop (n-1), CBR_L_1_Hop (n), CBR_L_2_Hop (n) )
where n corresponds to the nth trigger interval, T_trig
The CBR_G value is passed from the DCC_NET entity to the DCC_CROSS entity (see clause 5.4) and input to the
DCC algorithm running at the access layer as specified in ETSI TS 102 687 [4].
5.4 DCC_NET
As specified in ETSI TS 103 175 [3], clause 5.3 "DCC_NET", if GeoNetworking over ITS-G5 is used, a DCC_NET
entity shall be present.
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11 ETSI TS 102 636-4-2 V1.3.1 (2020-08)
The DCC_NET entity shall process the local CBR value, the CBR target value, and optionally the TX power level
upper limit of each individual used radio channel as specified in ETSI TS 103 175 [3], clause 6.2 "DCC parameter
evaluation" REQ008.
The service primitives and parameters for the interface between DCC_NET and the DCC_CROSS entity via the MN
SAP are defined in ETSI TS 103 175 [3], clause 8.3 "Interface (2) with DCC_NET (MN SAP)".
NOTE: ETSI TS 103 175 [3] also specifies the parameters idle time T per radio channel (REQ012), the
off
available resources that can be allocated per radio channel CBR , (REQ019), and the time when the last
a
message was forwarded to the ITS-G5 radio (REQ019). These parameters are not used in the present
document.
6 Addressing, data structure extensions and field
settings for ITS-G5
6.1 GeoNetworking address
As specified in ETSI EN 302 636-4-1 [1], clause 6, every GeoAdhoc router shall have a unique GeoNetworking address
and use the format in figure 5.
0    1    2    3
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
M ST Reserved MID
MID


Figure 5: GeoNetworking address format as specified in ETSI EN 302 636-4-1 [1]
For the MID field in the GeoNetworking address, the 48-bit MAC address of the ITS-G5 network interface shall be
used.
6.2 Location table extensions for ITS-G5
6.2.1 General
This clause specifies media-dependent extension to the Location Table Entry (LocTE) for GN over ITS-G5, following
the structure specified in ETSI EN 302 636-4-1 [1], clause 7.1.
6.2.2 Definition of additional data elements for the location table entry
If DCC_NET (see clause 5) is present, the location table of the GeoAdhoc router shall include the extensions - named
Location Table Entry Extension for ITS-G5 (LocTEX-G5) - for GN neighbours on ITS-G5 interfaces, as follows:
• Timestamp (local to ego station) of the last update of the LocTEX-G5, TST_G5(GN_ADDR).
• Timestamp in the SO PV of the SHB packet header as specified in ETSI EN 302 636-4-1 [1], clause 9.5.2
"Long Position Vector", TST_SO_PV_G5(GN_ADDR).
NOTE: TST_SO_PV_G5 is only updated when a received packet updates the LocTEX-G5; therefore it does not
necessarily equal the media-independent counterpart TST (POS, GN_ADDR) as specified in ETSI
EN 302 636-4-1[1], clause 7.1.2.
• Transmit power of the packet that updated the LocTEX-G5 entry, as specified in clause 6.3.3, table 3 (field
DCC-MCO octet 42, Bit 0 to Bit 4), TX_POWER_G5(GN_ADDR).
• Received signal-strength indicator RSSI of the packet that updated the LocTEX-G5 entry,
RSSI_G5(GN_ADDR).
ETSI
...