ETSI TR 103 667 V1.1.1 (2021-09)

Intelligent Transport Systems (ITS); Study on Spectrum Sharing between ITS-G5 and LTE-V2X technologies in the 5 855 MHz-5 925 MHz band

DTR/ERM-TG37-274

General Information

• Status: Not Published
• Technical Committee: ERM TG37 - ERM Intelligent Transport Systems
• Current Stage: 12 - Completion
• Due Date: 03-Sep-2021
• Completion Date: 10-Sep-2021

Standards Content (Sample)

TECHNICAL REPORT
Intelligent Transport Systems (ITS);
Study on Spectrum Sharing between ITS-G5 and LTE-V2X
technologies in the 5 855 MHz - 5 925 MHz band

2 ETSI TR 103 667 V1.1.1 (2021-09)

Reference
DTR/ERM-TG37-274
Keywords
ITS, radio, spectrum
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ETSI
3 ETSI TR 103 667 V1.1.1 (2021-09)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 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 . 6
4 Spectrum Sharing Options for ITS Technologies . 7
4.1 Introduction . 7
4.2 Framework for non-prioritized use of road ITS channels . 8
4.3 Priority-based framework for using road ITS channels . 9
4.3.1 Overview . 9
4.3.2 Description of the basic idea of priority-based framework . 9
4.3.3 Formalization and extension of the priority-based framework . 11
4.3.4 Inclusion of the frequency range 5 915 - 5 925 MHz in the framework . 17
4.4 Summary of options for priority-based framework . 18
5 Conclusions . 19
Annex A: Technical description of road ITS technologies . 21
A.1 Introduction . 21
A.2 ITS-G5 . 21
A.2.1 Introduction . 21
A.2.2 Physical layer . 22
A.2.3 Medium Access Control (MAC) . 23
A.2.3.1 Introduction. 23
A.2.3.2 Backoff procedure. 23
A.2.3.3 Medium access control . 24
A.2.3.4 EDCA parameters, AC and UP . 25
A.3 LTE-V2X . 26
A.3.1 Introduction . 26
A.3.2 Physical layer . 26
A.3.3 Medium access control . 27
A.3.3.1 Introduction. 27
A.3.3.2 Sensing based semi-persistent scheduling . 28
A.3.3.3 Hybrid automatic request . 29
History . 30

ETSI
4 ETSI TR 103 667 V1.1.1 (2021-09)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The declarations
pertaining to these essential IPRs, if any, are 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 Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
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.
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Foreword
This Technical Report (TR) has been produced by ETSI Technical Committee Electromagnetic compatibility and Radio
spectrum Matters (ERM).
Modal verbs terminology
In the present document "should", "should not", "may", "need not", "will", "will not", "can" and "cannot" are to be
interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.

ETSI
5 ETSI TR 103 667 V1.1.1 (2021-09)
1 Scope
The present document proposes an overall framework based on combinations of co-channel and/or non-co-channel
operation, as presented to CEPT, to address spectrum sharing between ITS-G5 and LTE-V2X ITS technologies
enabling both technologies to use the same spectrum in the same geographical area. The overall framework may consist
of several options for such combined operation.
2 References
2.1 Normative references
Normative references are not applicable in the present document.
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI TR 103 766: "Intelligent Transport Systems (ITS); Pre-standardization study on co-channel
co-existence between IEEE- and 3GPP-based ITS technologies in the 5 855 MHz-5 925 MHz
frequency band".
[i.2] ECC Decision (08)01: "The harmonised use of Safety-Related Intelligent Transport Systems (ITS)
in the 5875-5935 MHz frequency band", latest amendment on 06 March 2020.
[i.3] Commission Implementing Decision (EU) 2020/1426 of 7 October 2020 on the harmonised use of
radio spectrum in the 5 875-5 935 MHz frequency band for safety-related applications of
intelligent transport systems (ITS) and repealing Decision 2008/671/EC.
[i.4] ETSI EN 302 665 (V1.1.1) (09-2010): "Intelligent Transport Systems (ITS); Communications
Architecture".
[i.5] ETSI EN 302 663 (V1.3.1) (01-2020): "Intelligent Transport Systems (ITS); ITS-G5 Access layer
specification for Intelligent Transport Systems operating in the 5 GHz frequency band".
TM
[i.6] IEEE Std 802.11 -2020: "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.7] IEEE/ISO/IEC 8802-2 -1998: "Information technology -- Telecommunications and information
exchange between systems -- Local and metropolitan area networks -- Specific requirements --
Part 2: Logical Link Control".
TM
[i.8] IEEE 802.11e -2005: "IEEE Standard for Information technology - Local and metropolitan area
networks - Specific requirements - Part 11: Wireless LAN Medium Access Control (MAC) and
Physical Layer (PHY) Specifications - Amendment: Medium Access Method (MAC) Quality of
Service Enhancements".
TM
[i.9] ANSI/IEEE Std 802.1D 1998: "IEEE Standard for Information technology -
Telecommunications and information exchange between systems - Local and metropolitan area
networks - Common specifications - Part 3: Media Access Control (MAC) Bridges".
ETSI
6 ETSI TR 103 667 V1.1.1 (2021-09)
[i.10] ETSI EN 303 613 (V1.1.1) (01-2020): "Intelligent Transport Systems (ITS); LTE-V2X Access
layer specification for Intelligent Transport Systems operating in the 5 GHz frequency band".
[i.11] ETSI TS 136 213: "LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer
procedures (3GPP TS 36.213 version 15.9.0 Release 15)".
[i.12] ETSI TS 136 211: "LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical
channels and modulation (3GPP TS 36.211 version 14.3.0 Release 14)".
[i.13] ETSI TS 136 300: "LTE; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved
Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (3GPP
TS 36.300 version 14.3.0 Release 14)".
[i.14] ETSI TS 136 321: "LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); Medium Access
Control (MAC) protocol specification (3GPP TS 36.321 version 14.2.1 Release 14)".
[i.15] ETSI TS 136 101: "LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment
(UE) radio transmission and reception (3GPP TS 36.101 version 14.4.0 Release 14)".
[i.16] ETSI TS 103 723 (V1.2.1) (2020-11): "Intelligent Transport Systems (ITS); Profile for LTE-V2X
Direct Communication".
[i.17] ETSI TR 103 319 (V1.1.1): "Broadband Radio Access Networks (BRAN); 5 GHz high
performance RLAN; Mitigation techniques to enable sharing between RLANs and Road Tolling
and Intelligent Transport Systems in the 5 725 MHz to 5 925 MHz band".
3 Definition of terms, symbols and abbreviations
3.1 Terms
Void.
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AC Access Category
AIFS Arbitration Interframe Space
AIFSN AIFS number
AP Access Point
ARQ Automatic ReQuest
BE Best Effort
BK BacKground
BPSK Binary Phase Shift Keying
BSS Basic Service Set
BSSID BSS IDentifier
CW Contention Window
DCF Distributed Coordination Function
DFS Dynamic Frequency Selection
DIFS Distributed Interframe Space
DL Data Link layer
EDCA Enhanced Distributed Coordination Access
EE Excellent Effort
HARQ Hybrid ARQ
IBSS Independent BSS
ETSI
7 ETSI TR 103 667 V1.1.1 (2021-09)
ITS Intelligent Transport Systems
LLC Logical Link Control
MAC Medium Access Control
MCS Modulation and Coding Scheme
MIB Management Information Base
MPDU MAC Protocol Data Unit
NC Network Control
OFDM Orthogonal Frequency Division Multiplexing
OSI Open System Interconnect
PHY Physical Layer
PLCP Physical Layer Convergence Procedure
PPDU PLCP Protocol Data Unit
PSCCH Physical Sidelink Control Channels
PSDU PLCP Service Data Unit
PSSCH Physical Sidelink Shared Channels
QAM Quadrature Amplitude Modulation
QPSK Quadrature Phase Shift Keying
RB Resource Block
RLAN Radio Local Area Network
RSRP Reference Signal Received Power
RSSI Received Signal Strength Indicator
SCI Side Control Information
SPS Semi-Persistent Scheduling
TTI Transmission Time Interval
UP User Priority
VI VIdeo
VO VOice
4 Spectrum Sharing Options for ITS Technologies
4.1 Introduction
Currently, there are two technologies for short-range wireless communications for cooperative ITS that can be used in
the 5,9 GHz band [i.3]: ITS-G5 [i.5] based on IEEE 802.11p [i.6] and LTE-V2X [i.10] developed by 3GPP. Spectrum
sharing options are therefore necessary to make sure both technologies can co-exist in a seamless way. The spectrum
sharing options need to be defined in the context of the new CEPT band plan for 5,9 GHz, which is depicted in
Figure 1. It designates a total of 40 MHz in the frequency range 5 875 MHz - 5 915 MHz for safety related ITS
prioritized for road ITS. Therefore, the spectrum sharing options which will be proposed are based on the availability of
10 MHz radio channels for road ITS. In addition, the frequency range 5 915 MHz - 5 925 MHz, which is prioritized for
urban rail ITS, could be used by road ITS after ETSI has developed polite protocols and/or proper co-channel sharing
mechanisms between road ITS and urban rail ITS. According to the ECC decision (08)01 [i.2], the frequency range
5 915 MHz - 5 925 MHz could be used for road ITS I2V applications on a national basis before the development of the
above mentioned polite protocols and/or proper co-channel sharing mechanisms, which is out of the scope of the
present document. Therefore, the sharing of the frequency range 5 915 - 5 925 MHz between road ITS technologies
discussed in clause 4.3.4 assumes that road ITS technologies could access this frequency range by applying the polite
protocols and/or proper co-channel sharing mechanisms between road ITS and urban rail ITS specified by ETSI.
ETSI
8 ETSI TR 103 667 V1.1.1 (2021-09)

Figure 1: New CEPT band plan for ITS technologies
Table 1 shows the frequency range for each of the four radio channels in 5 875 MHz - 5 915 MHz prioritized for road
ITS and a proposed mapping of these radio channels to the channel numbers used in the present document. In addition,
the same nomenclature is used in the present document for the frequency range 5 915 MHz - 5 925 MHz prioritized for
urban rail ITS under the assumption that road ITS technologies can access this frequency range by applying the polite
protocols and/or proper co-channel sharing mechanisms between road ITS and urban rail ITS specified by ETSI (not
covered by the present document, as above clarified).
Table 1: The frequency range of road ITS radio channels and the numbers assigned to them
Channel 1 Channel 2 Channel 3 Channel 4 Channel 5
5 875 MHz - 5 885 5 885 MHz - 5 895 5 895 MHz - 5 905 5 905 MHz - 5 915 5 915 MHz - 5 925
MHz MHz MHz MHz MHz
4.2 Framework for non-prioritized use of road ITS channels
This framework means that all road ITS radio channels can be accessed on equal footing by all road ITS technologies
through a co-channel co-existence method. The decision to use a specific channel is not based on technology but rather
on other criteria, which could for example be based on use cases, where different channels would be used for different
clusters of use cases, such as basic CAM/DENM safety messages, platooning messages, collective perception messages,
etc. Addressing the requirements for such scenarios is out of the scope of the present document.
This framework means that all road ITS radio channels can be accessed on equal footing by all ITS technologies, and
the decision to use a specific channel is not based on technology but on other criteria. One example scenario is "use
case" as a criterion, where different channels would be used for different clusters of use cases, such as basic
CAM/DENM safety messages, Platooning messages, cooperative perception messages, etc. Addressing the
requirements for such scenarios is out of the scope of the present document.
There are several proposed methods for co-channel coexistence between the road ITS technologies ITS-G5 and
LTE-V2X in ETSI TR 103 766 [i.1].
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9 ETSI TR 103 667 V1.1.1 (2021-09)
4.3 Priority-based framework for using road ITS channels
4.3.1 Overview
Unlike the non-prioritized framework of the previous clause 4.2, the priority-based framework assigns technology-
dependent priorities to individual road ITS channels. The goal is to develop a framework for spectrum sharing because
co-channel sharing is not yet defined, and it is not still assessed if such sharing would be feasible with acceptable
performance degradation. The purpose is the assignment of priorities to different ITS technologies in the different ITS
radio channels shown in Table 1. For this purpose, the following driving criteria are considered:
1) The basic essential safety messages need to be delivered with the reliability and latency requirements defined
for such messages.
2) Other safety and non-safety messages can be delivered with a different level of reliability and latency.
The ultimate objective of criterion 1 is to make sure that essential safety messages will be reliably transmitted over a
10 MHz radio channel. In this context, the reliability of the safety messages is a key factor for the selection of a
proposed spectrum sharing option. Because such option aims at coexistence between the two road ITS technologies
with different radio air interfaces, its selection in a manner to avoid impacts on the structure of the radio air interface of
the involved technologies might be challenging, especially for the latency requirement in the case of short timescale
interaction (in the order of μs) with high reliability. Also, the impact on existing specifications depends on the detection
capability and the envisaged target reliability. A high-level pictorial representation of different trade-offs involved in
developing a coexistence solution is shown in the example of Figure 2.

Figure 2: An example of trade-offs in designing/developing a coexistence solution
4.3.2 Description of the basic idea of priority-based framework
Based on the above observations, a hybrid approach is proposed where different technologies need to fulfil different
coexistence requirements on different radio channels. The coexistence requirements depend on priorities assigned to
specific technologies in specific channels. A set of radio channels is meant to be used for essential safety messages of a
certain technology. To guarantee high reliability in such channels, a priority level is assigned to each technology in each
of the channels. Depending on way the priority levels are assigned to different technologies, different options will
result.
A pictorial presentation of the basic idea is depicted in Figure 3, assuming two different technologies, Tech A and Tech
B, operating in the band prioritized for road ITS. The example can be summarized as follows:
• Tech A and Tech B share the available 40 MHz spectrum (4 radio channels each 10 MHz).
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10 ETSI TR 103 667 V1.1.1 (2021-09)
• Two 10 MHz radio channels are assigned for essential safety with different priority levels for Tech A and
Tech B:
- In the channel with the highest priority level assigned to Tech A (Tech B), Tech A (Tech B) does not
need to perform any detection of the presence of Tech B (Tech A).
• The other two 10 MHz channels are shared in time between the two technologies, for example based on one of
the methods described in ETSI TR 103 766 [i.1].

Figure 3: Proposed hybrid approach for road ITS coexistence
On the priority channels the burden of detection will be on the technology which has the least priority. On the other
hand, in the shared channels, the burden of detection is shared between the two technologies. Based on this principle,
two coexistence mechanisms can be defined:
• A mechanism for the channels assigned with high priority level to a specific technology. In this case, the
burden of detection will be on the technology which does not have priority. In particular, the technology that
intends to use the channel, that is prioritized for the other technology, would need to meet additional
coexistence criteria which requires the detection of the channel use by the other technology. These criteria, e.g.
detect and vacate, are not yet defined and are out of the scope of the present document. Existing detect and
vacate schemes, e.g. DFS in RLAN to protect radars where an access point monitors the frequency for some
time and coordinates channel switching cannot be applied to ITS, since ITS stations are highly mobile and
communicate via broadcast without connection establishment. The technology with lower priority cannot
assign a service solely to this channel without risking service interruption. Therefore, additional mechanisms
for service continuity are required in this case.
• A different mechanism will be used for the channels which are shared. For such channels, both technologies
need to detect the presence of each other based on the equal sharing principle. The solution is defined in
ETSI TR 103 766 [i.1].
The detect and vacate method is not studied in detail in the present document and needs to be investigated in the future.
Similar studies on detection with other technologies have been done in other ETSI deliverables such as ETSI
TR 103 319 [i.17]. Detect and vacate needs to be implemented to achieve a good trade-off between protection of
prioritized technologies and efficient use of spectrum.
So, in summary for channels which are shared, the coexistence solution will be based on the co-channel coexistence
study in ETSI TR 103 766, while requirements associated to the imbalance priority case will be defined in a future ETSI
specification.
The priority channels identified for safety are some sort of "anchor" channels: one technology can always use the
10 MHz assigned with high priority for basic safety applications but can only get access to the other channels if the
coexistence requirements defined for those channels are met. This approach represents a trade-off between optimizing
spectrum utilization and providing reliable access to the "anchor" channels. The benefit of the proposed approach is that
from day 1 both technologies can operate on such "anchor" channels, where they have the highest priority, without
requiring any change to their radio air interface specifications. The potential disadvantage is that initially deployed
technologies without sharing capability may stay on their priority channels for the future and could impact other
technologies using those channels for safety applications in the case that priorities for using those channels are changed.
At the same time, the shared channels could be used by all technologies provided additional requirements for the
co-channel coexistence are met.
ETSI
11 ETSI TR 103 667 V1.1.1 (2021-09)
4.3.3 Formalization and extension of the priority-based framework
The proposed approach can be formalized as follows:
• For each radio channel a priority level is assigned to each technology, called mapping between a radio channel
and the priority level assigned to a specific technology in that channel.
• Based on the assigned priority level in a specific channel, a decision is made by a technology in that channel in
case of detection of the other technology (if detection required).
Depending on the number of priority levels used and the mapping between the radio channels and the priority levels
assigned to different technologies, several options are possible as presented below. For this purpose, the following
priority levels are defined:
• "0": the radio channel cannot be used, since it is either reserved for future services or no sharing between
technologies with different access schemes is allowed, unless the technology with a lower priority applies a
channel access scheme compatible with that of the technology with the higher priority.
• "1": the radio channel could be accessed by Tech A (Tech B), which has lower priority, provided it is not
occupied by Tech B (Tech A), which has higher priority.
• "2": the radio channel is shared in time between Tech A and Tech B on a non-prioritized basis.
• "3": the radio channel is prioritized for Tech A (Tech B) but could be used by Tech B (Tech A), provided it is
not occupied by the technology, which the radio channel is prioritized for.
Depending on the mapping between a radio channel and the assigned priority to a specific technology in that channel,
one of the following actions will be taken by this technology if it detects another technology in the considered radio
channel.
• VOID/ COMPATIBLE ACCESS: corresponds to the priority level "0" assigned to a technology in a radio
channel and means that a device implementing this technology cannot use the radio channel.
• VACATE: corresponds to the priority level "1" assigned to a technology in a radio channel and means that a
device implementing this technology should vacate the radio channel if it detects there a device implementing
a technology with a higher assigned priority for that radio channel.
• SHARE: corresponds to the priority level "2" assigned to a technology in a radio channel and means that the
radio channel is shared between the technologies operating in this channel by using one of the coexistence
methods defined in ETSI TR 103 766 [i.1].
• STAY: corresponds to the priority level "3" assigned to a technology in a radio channel and means that a
device implementing this technology may access the channel without any need for modifications in its channel
access mechanism. Such device does not need to perform any assessment about the presence of another
technology in such radio channel and even if does so and detects in the radio channel a device implementing a
technology with a lower assigned priority for that radio channel, it should stay in the radio channel. In other
words, the technology with a lower priority, which can use the channel, carries the full burden of assessing
whether the technology with a higher priority is operating in the channel and needs to vacate the channel if it
detects a device implementing the technology with the higher priority.
Based on the framework above, different priority options can be set in different situations. What matters is that for the
supported priority the device fulfils the minimum requirement associated to that priority.
Option 1: Two prioritized channels and 3 priority levels
It is the option in Figure 3 and the mapping between the radio channels and the priority levels assigned to different
technologies is shown in Table 2. In this option, the anchor channels will consist of 10 MHz.
ETSI
12 ETSI TR 103 667 V1.1.1 (2021-09)
Table 2: Example of assigned priorities
Priorities
Channel 1 Channel 2 Channel 3 Channel 4

Tech A 3 2 1 2
Tech B 1 2 3 2
Depending on the mapping between the radio channels and the priority level assigned to a specific technology in
Table 2, the actions shown in Table 3 need to be taken in the case that one technology detects another technology.
Table 3: Decisions to be taken by each technology in case of detection
Decision in case of detection
Channel 1 Channel 2 Channel 3 Channel 4

Tech A STAY SHARE VACATE SHARE
Tech B VACATE SHARE STAY SHARE

The abovementioned actions put specific requirements on PHY mechanisms which would allow to facilitate channel
access depending on the priority level. Depending on the prioritization, each technology will then choose to multiplex
its traffic across different channels in the most appropriate way as outlined below.
• Tech A:
- It can use channel 1 with very relaxed/no PHY additional requirement.
- It can use channel 2 and channel 4 with a specific PHY additional requirement not covered in the present
document. This requirement is one of the possible co-channel coexistence requirements defined in
ETSI TR 103 766 [i.1].
- It can use channel 3 with a specific PHY additional requirement not covered in the present document.
This requirement can be defined in an ETSI specification and should be a very stringent requirement
since it needs to allow the other technology to use the same channel with a high priority level. The goal is
that the channel is not used if the other technology is present.
• Tech B:
- It can use channel 3 with very relaxed/no PHY additional requirement.
- It can use channel 2 and channel 4 with a specific PHY additional requirement not covered in the present
document. This requirement is one of the possible co-channel coexistence requirements defined in
ETSI TR 103 766 [i.1].
- It can use channel 1 with a specific PHY additional requirement not covered in the present document.
This requirement can be defined in an ETSI specification and should be a very stringent requirement
since it needs to allow the other technology to use the same channel with high priority. The goal is that
the channel is not used if the other technology is present.
Option 2: Four prioritized channels and 2 priority levels
In the option presented in Figure 4, one of the shared channels in Option 1 is assigned to Tech A with the priority level
"3" whereas the other shared channel is assigned to Tech B with the priority level "3". In this option, the anchor
channels will consist of 20 MHz (two 10 MHz radio channels). The corresponding priorities and decisions to be taken
in case of detecting the other technology are shown in Table 4 and Table 5, respectively.

Figure 4: An approach for road ITS coexistence with four prioritized channels
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13 ETSI TR 103 667 V1.1.1 (2021-09)
Table 4: Example of assigned priorities
Priorities
Channel 1 Channel 2 Channel 3 Channel 4

Tech A 3 3 1 1
Tech B 1 1 3 3
Depending on the mapping between the radio channels and the priority level assigned to a specific technology in
Table 4, the actions shown in Table 5 need to be taken in the case that one technology detects another technology.
Table 5: Decisions to be taken by each technology in case of detection
Decision in case of detection
Channel 1 Channel 2 Channel 3 Channel 4

Tech A STAY STAY VACATE VACATE
Tech B VACATE VACATE STAY STAY

The abovementioned actions put specific requirements on PHY mechanisms which would allow to facilitate channel
access depending on the priority level. Depending on the prioritization, each technology will then choose to multiplex
its traffic across different channels in the most appropriate way as outlined below.
• Tech A:
- It can use channel 1 and channel 2 with very relaxed/no PHY additional requirement.
- It can use channel 3 and channel 4 with a specific PHY additional requirement not covered in the present
document. This requirement can be defined in an ETSI specification and should be a very stringent
requirement since it needs to allow the other technology to use the same channel with a high priority
level. The goal is that the channel is not used if the other technology is present.
• Tech B:
- It can use channel 3 and channel 4 with very relaxed/no PHY additional requirement.
- It can use channel 1 and channel 2 with a specific PHY additional requirement not covered in the present
document. This requirement can be defined in an ETSI specification and should be a very stringent
requirement since it needs to allow the other technology to use the same channel with high priority. The
goal is that the channel is not used if the other technology is present.
Option 3: Two prioritized channels and 3 priority levels
In this option, the radio channel assigned to Tech A as anchor channel is not accessible for Tech B stations and vice
versa. As in Option 1, the other two radio channels are shared in time between the two technologies, for example based
on one of the methods described in ETSI TR 103 766 [i.1].
Table 6: Example of assigned priorities
Priorities
Channel 1 Channel 2 Channel 3 Channel 4

Tech A 3 2 0 2
Tech B 0 2 3 2
Depending on the mapping between the radio channels and the priority level assigned to a specific technology in
Table 6, the actions shown in Table 7 need to be taken in the case that one technology detects another technology.
ETSI
14 ETSI TR 103 667 V1.1.1 (2021-09)
Table 7: Decisions to be taken by each technology in case of detection
Decision in case of detection
Channel 1 Channel 2 Channel 3 Channel 4

VOID/
Tech A STAY SHARE COMPATIBLE SHARE
ACCESS
VOID/
Tech B COMPATIBLE SHARE STAY SHARE
ACCESS
This option differs from Option 1 as the "VOID/ COMPATIBLE ACCESS" setting are used. The rationale is:
• The "STAY" setting in this option refers to plain Tech A (Tech B) without any modifications of this
technology.
• "VOID/ COMPATIBLE ACCESS" setting introduces an even more constraining situation than the
"VACATE". This might be especially useful for the situations where one technology is already started to be
deployed in a specific channel without any concept of coexistence. Thus, to ensure maximal safety and no
performance compromise, access to this channel, characterized as "COMPATIBLE ACCESS", strictly
requires applying the channel access scheme of the technology that has "STAY' setting for this channel.
The abovementioned actions put specific requirements on PHY mechanisms which would allow to facilitate channel
access depending on the priority level. Depending on the prioritization, each technology will then choose to multiplex
its traffic across different channels in the most appropriate way as outlined below:
• Tech A:
- It can use channel 1 without any PHY additional requirement.
- It can use channel 2 and channel 4 with a specific PHY additional requirement not covered in the present
document. This requirement is one of the possible co-channel coexistence requirements defined in
ETSI TR 103 766 [i.1].
- It cannot use channel 3, unless it uses the channel access scheme of Tech B.
• Tech B:
- It can use channel 3 without any PHY additional requirement.
- It can use channel 2 and channel 4 with a specific PHY additional requirement not covered in the present
document. This requirement is one of the possible co-channel coexistence requirements defined in
ETSI TR 103 766 [i.1].
- It cannot use channel 1, unless it uses the channel access scheme of Tech A.
Option 4: Four prioritized channels and 3 priority levels
In this option, the channel assigned to Tech A (Tech B) as anchor channel is not accessible for Tech B (Tech A) stations
and vice versa. Amongst the other two channels, one is prioritized for Tech A and one for Tech B, as in Option 2.
Table 8: Example of assigned priorities
Priorities
Channel 1 Channel 2 Channel 3 Channel 4

Tech A 3 3 0 1
Tech B 0 1 3 3
Depending on the mapping between the radio channels and the priority level assigned to a specific technology in
Table 8, the actions shown in Table 9 need to be taken in the case that one technology detects another technology.
ETSI
15 ETSI TR 103 667 V1.1.1 (2021-09)
Table 9: Decisions to be taken by each technology in case of detection
Decision in case of detection
Channel 1 Channel 2 Channel 3 Channel 4

VOID/COMPATIBLE
Tech A STAY STAY VACATE
ACCESS
VOID/COMPATIBLE
Tech B VACATE STAY STAY
ACCESS
This option differs from Option 2 as the "VOID/ COMPATIBLE ACCESS" setting are used in two of prioritized
channels. The rationale is:
• The "STAY" setting in this option refers to plain Tech A (Tech B) without any modifications of this
technology.
• "VOID/ COMPATIBLE ACCESS" setting introduces an even more constraining situation than the
"VACATE". This might be especially useful for the situations where one technology is already started to be
deployed in a specific channel, without any concept of coexistence. Thus, to ensure maximal safety and no
performance compromise, access to this channel, characterized as "COMPATIBLE ACCESS", strictly
requires applying the channel access scheme of the technology that has "STAY' setting for this channel.
The abovementioned actions put specific requirements on PHY mechanisms which would allow to facilitate channel
access depending on the priority level. Depending on the prioritization, each technology will then choose to multiplex
its traffic across different channels in the most appropriate way as outlined below.
• Tech A:
- It can use channel 1 without any PHY additional requirement.
- It can use channel 2 with very relaxed/no PHY additional requirement.
- It cannot use channel 3, unless it uses the channel access scheme of Tech B.
- It can use channel 4 with a specific PHY additional requirement not covered in the present document.
This requirement can be defined in an ETSI specification and should be a very stringent requirement
since it needs to allow the other technology to use the same channel with a high priority level. The goal is
that the channel is not used if the other technology is present.
• Tech B:
- It can use channel 3 without any PHY additional requirement.
- It can use channel 4 with very relaxed/no PHY additional requirement.
- It cannot use channel 1, unless it uses the channel access scheme of Tech A.
- It can use channel 2 with a specific PHY additional requirement not covered in the present document.
This requirement can be defined in an ETSI specification and should be a very stringent requirement
since it needs to allow the other technology to use the same channel with a high priority level. The goal is
that the channel is not used if the other technology is present.
Option 5: Two prioritized channels and two channels reserved for other services
This option is outlined as follows:
1) Address the allocation strategies for channels 3 - 4 (5 895 MHz - 5 915 MHz) according to Table 10 and
Table 11 which may be used for day-1 basic safety.
2) Address the remaining channels 1 - 2 (5 875 MHz - 5 895 MHz) according to Tabl
...