ISO 22738:2020

Intelligent transport systems -- Localized communications -- Optical camera communication

This document specifies OCC (Optical Camera Communication) as an access technology for localized communications applicable in ITS stations conforming with ISO 21217. OCC access technology is specified for the implementation context of ISO 21218. This document provides specifications of a communication interface (CI) named "ITS-OCC". This document specifies the additions to and deviations from IEEE 802.15.7:2018 which are required in order to make ITS-OCC CIs compatible with: — the ITS station and communication architecture specified in ISO 21217, and — the hybrid communications support specified in ISO 21218. This document specifies: — an OCC profile of IEEE 802.15.7:2018 for usage in C-ITS; — details of CAL (ISO 21218); and — details of MAE (ISO 21218, ISO 24102-3). NOTE Considering safety-related services involving communications between a vehicle and a roadside station being performed on the basis of OCC, it is noted that, due to shadowing, communications can be interrupted or blocked for a significantly long time.

Systèmes intelligents de transport -- Communications localisées -- Communication par caméra optique

Standards Content (sample)

INTERNATIONAL ISO
STANDARD 22738
First edition
2020-07
Intelligent transport systems —
Localized communications — Optical
camera communication
Systèmes intelligents de transport — Communications localisées —
Communication par caméra optique
Reference number
ISO 22738:2020(E)
ISO 2020
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ISO 22738:2020(E)
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© ISO 2020

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ISO 22738:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

5 IEEE 802.15.7 ........................................................................................................................................................................................................... 3

5.1 General requirements ....................................................................................................................................................................... 3

5.2 OCC PHY and MAC architecture ................................................................................................................................................ 3

5.3 PHY mode .................................................................................................................................................................................................... 4

5.4 Modulation schemes .......................................................................................................................................................................... 4

5.5 MAC frame format ................................................................................................................................................................................ 5

5.6 Dimming ....................................................................................................................................................................................................... 5

5.7 Mitigation of flickering ..................................................................................................................................................................... 5

6 ITS station .................................................................................................................................................................................................................... 5

6.1 ITS station and communication architecture ............................................................................................................... 5

6.2 ITS-S service access points ........................................................................................................................................................... 8

6.2.1 General...................................................................................................................................................................................... 8

6.2.2 Communications SAPs ................................................................................................................................................ 8

6.2.3 Management SAPs .......................................................................................................................................................... 8

6.2.4 Security SAPs ...................................................................................................................................................................... 8

6.3 Hybrid communications support ............................................................................................................................................ 8

7 Communication interface protocol stack .................................................................................................................................... 8

7.1 Communication interface parameters ................................................................................................................................ 8

7.2 Physical layer ............................................................................................................................................................................................ 8

7.3 Data link layer .......................................................................................................................................................................................10

7.3.1 General...................................................................................................................................................................................10

7.3.2 Communication adaptation sub-layer ........................................................................................................10

8 Communication interface management ....................................................................................................................................10

8.1 General management......................................................................................................................................................................10

8.2 Management adaptation entity..............................................................................................................................................10

8.2.1 OCC parameters and I-Parameters ................................................................................................................10

8.2.2 OCC management commands and MI-SAP commands and requests ..............................10

9 Procedures ...............................................................................................................................................................................................................11

9.1 Transmit procedure .........................................................................................................................................................................11

9.2 Receive procedures ..........................................................................................................................................................................11

9.3 Management procedures ............................................................................................................................................................11

10 Conformance ..........................................................................................................................................................................................................11

11 Test methods ..........................................................................................................................................................................................................11

Annex A (normative) Communication interface parameters ..................................................................................................12

Annex B (normative) MI-COMMANDs ...............................................................................................................................................................16

Annex C (normative) MI-REQUESTs ....................................................................................................................................................................17

Annex D (normative) ASN.1 definitions ..........................................................................................................................................................18

Annex E (informative) Frequency band and frequency allocation .....................................................................................21

Annex F (informative) Dimming method ......................................................................................................................................................22

Bibliography .............................................................................................................................................................................................................................25

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ISO 22738:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

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electrotechnical standardization.

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described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

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iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 22738:2020(E)
Introduction

Localized communications are an essential component of hybrid communications in Intelligent

Transport Systems (ITS). Various access technologies are suited for localized communications. An

increasing interest of ITS stakeholders for Cooperative ITS (C-ITS), Urban ITS (U-ITS), and Advanced

Driver Assistance Systems (ADAS) is on the access technology in OCC (Optical Camera Communication)

specified by IEEE.
OCC is capable of:
a) interoperating with cameras and LEDs devices, and

b) receiving messages from LED sources, and transmitting messages from back light and front light of

vehicles to other vehicles.
The purpose of OCC is broadcast dissemination of ITS information from:
— light sources (traffic light, street light, traffic sign), and
— vehicles
to other vehicles (one-to-many); see Figure 1.
Figure 1 — OCC based ITS Communication
OCC is considered for usage in:
1) roadside ITS station units (ITS-SUs), and
2) vehicle ITS-SUs.
OCC is intended to provide information to vehicles, see Figure 2.
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ISO 22738:2020(E)
Figure 2 — Vehicle-centric data flow in OCC

OCC uses LEDs as transmitters and cameras as receivers with visible light or near IR (NIR).

Characteristics of OCC are:
— visibility (visible light band);
— no regulation in optical frequency;
— harmlessness to human health (infrared and visible light band);
— non-interference with CIs based on radio waves; and
— licence-free operation.
See also Reference [6].

Figure 3 shows the basic operation of OCC. OCC supports ITS applications for vehicular scenarios such

[7], [8], [9]
as those already proposed by universities and companies .
Figure 3 — Basic OCC operation
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INTERNATIONAL STANDARD ISO 22738:2020(E)
Intelligent transport systems — Localized communications
— Optical camera communication
1 Scope

This document specifies OCC (Optical Camera Communication) as an access technology for localized

communications applicable in ITS stations conforming with ISO 21217.

OCC access technology is specified for the implementation context of ISO 21218. This document provides

specifications of a communication interface (CI) named "ITS-OCC".

This document specifies the additions to and deviations from IEEE 802.15.7:2018 which are required in

order to make ITS-OCC CIs compatible with:
— the ITS station and communication architecture specified in ISO 21217, and
— the hybrid communications support specified in ISO 21218.
This document specifies:
— an OCC profile of IEEE 802.15.7:2018 for usage in C-ITS;
— details of CAL (ISO 21218); and
— details of MAE (ISO 21218, ISO 24102-3).

NOTE Considering safety-related services involving communications between a vehicle and a roadside

station being performed on the basis of OCC, it is noted that, due to shadowing, communications can be

interrupted or blocked for a significantly long time.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 17419, Intelligent transport systems — Cooperative systems — Globally unique identification

ISO 21217, Intelligent Transport System — Communications access for land mobiles (CALM) — Architecture

ISO 21218, Intelligent transport systems — Hybrid communications — Access technology support

ISO/IEC 8825-2, Information technology — ASN.1 encoding rules: Specification of Packed Encoding Rules

(PER) — Part 2:
IEEE 802.15.7:2018, IEEE standard for Optical Wireless Communication (OWC)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 21217, ISO 21218, and

IEEE 802.15.7:2018 apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
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ISO 22738:2020(E)
— IEC Electropedia: available at http:// www .electropedia .org/
4 Symbols and abbreviated terms

For the purposes of this document, the symbols and abbreviated terms given in ISO 21217, ISO 21218,

and IEEE 802.15.7:2018, and the following apply.
ATS abstract test suite
DC direct current
DME device management entity
DS8-PSK dimmable spatial 8-phase shift keying
EIRP equivalent isotropic radiation power
FSK frequency shift keying
HS-PSK hybrid spatial phase shift keying
ICS implementation conformance statement
ITS-OCC name of the OCC communication interface
LED light-emitting diode
LLC logical link control
MAC medium access control sub-layer
M-FSK M-ary FSK
NIR near-infrared radiation
OCC optical camera communications
OOK on-off keying
OWC optical wireless communications
PAN personal area network
PHY physical layer
PIB PAN information base
S2-PSK spatial 2-phase shift keying
SAP service access point
SSCS service-specific convergence layer
SUT system under test
TSS&TP test suite structure and test purposes
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ISO 22738:2020(E)
UFSOOK undersampled frequency shift OOK
VPPM variable pulse-position modulation
VPWM variable pulse-width modulation
5 IEEE 802.15.7
5.1 General requirements

An ITS-OCC CI implementation shall be conformant with the specifications presented in IEEE 802.15.7,

with restrictions and amendments as specified in this document.

NOTE IEEE 802.15.7 represents the basis for developing products with guaranteed functionalities. It also

provides a minimum benchmark for future developments. IEEE 802.15.7 is intended to support a variety of

expected applications, relating to OWC Personal Area Networks. This document only supports a subset of the

whole functionality of IEEE 802.15.7.

Information on the frequency band and frequency allocation for rolling shutter OCC are presented in

Annex E.
Information on the dimming method is provided in Annex F.
5.2 OCC PHY and MAC architecture

IEEE 802.15.7 defines a PHY and MAC layer for short-range optical wireless communications using

visible light in optically transparent media. It considers mobility of the visible link, compatibility with

visible-light infrastructures, impairments due to noise and interference from sources like ambient light,

and a MAC layer that accommodates visible links. Furthermore, IEEE 802.15.7 adheres to applicable eye

safety regulations.

Figure 4 presents the OCC PHY and MAC architecture as specified in IEEE 802.15.7. This architecture

maps to the ITSS access layer of the station architecture presented in Figure 5 and Figure 6.

NOTE According to IEEE 802.15.7:2018 Annex B, an LLC sub-layer is part of the "upper layers". Figure 4 does

not reflect this fact.
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ISO 22738:2020(E)
Figure 4 — OCC PHY and MAC architecture in IEEE 802.15.7
5.3 PHY mode

An ITS-OCC CI implementation conformant with this specification shall support PHY mode IV specified

in IEEE 802.15.7.
NOTE 1 PHY IV is intended for use with discrete light sources.
NOTE 2 For PHY IV, over-the-air PHY and MAC frame configuration is forbidden.

NOTE 3 PHY IV distinguishes 5 sub-modes by different modulation schemes, i.e. UFSOOK, Twinkle VPPM, S2-

PSK, HS-PSK, Offset-VPWM, see also 5.4.
5.4 Modulation schemes
An ITS-OCC implementation shall be conformant with the specification of:

— Spatial 2 Phase Shift Keying (S2-PSK) modulation scheme specified in IEEE 802.15.7;

— Hybrid Spatial Phase Shift Keying (HS-PSK) modulation scheme specified in IEEE 802.15.7.

NOTE The choice between S2-PSK and HS-PSK is given by implementation, i.e. read from the PIB. Thus, there

is a potential interoperability problem, as the modulation scheme is not reported in a frame header.

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ISO 22738:2020(E)
5.5 MAC frame format
This document does not specify normative requirements on the MAC frame format.

NOTE 1 According to IEEE 802.15.7, for PHY IV, the frame control field, the sequence number field, the

destination OWPAN identifier field, the MAC source address field, the MAC destination address field, and the

auxiliary security header field are not present.

NOTE 2 According to IEEE 802.15.7, in PHY IV, the frame payload field is not used except in the Twinkle VPPM

and Offset-VPWM PHY modes. The Twinkle VPPM and Offset-VPWM PHY modes use only the frame payload.

The frame payload field has a variable length and contains information specific to individual frame types. If the

security is enabled, then the frame payload is protected as defined by the security suite selected for that frame.

NOTE 3 According to IEEE 802.15.7, in PHY IV, the FCS field is not used except in the UFSOOK, Offset-VPWM

PHY, and Twinkle VPPM PHY modes.
5.6 Dimming

An ITS-OCC CI implementation conformant with this document shall support dimming specified in

IEEE 802.15.7. Dimming requests from upper layers to the PHY shall be indicated using the PHY PIB

attribute specified in IEEE 802.15.7. The PHY shall support dimming using one of the techniques

specified in either dimming during idle time or dimming during data transmission time when the PHY

PIB attribute phyDim specified in IEEE 802.15.7 is set.
5.7 Mitigation of flickering

An ITS-OCC CI implementation conformant with this document shall support the mitigation of flickering

in intra-frames and inter-frames as specified in Table 1.
Table 1 — Flickering mitigation
Operational mode Data transmission Idle or RX periods
(Intra-frame flicker) (Inter-frame flicker)
S2-PSK DC-balanced waveforms, ½-rate line code
Out-of-band idle pattern
HS-PSK VPPM waveforms
6 ITS station
6.1 ITS station and communication architecture

The ITS station architecture specified in ISO 21217 is presented in Figure 5. The ITS-OCC CI is allocated

in the ITS-S access layer of the ITS station architecture.
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ISO 22738:2020(E)
Figure 5 — ITS station architecture (from ISO 21217)

Figure 6 shows the architecture diagram of an ITS-OCC CI embedded in the general ITS station

architecture.
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ISO 22738:2020(E)
Figure 6 — ITS-OCC CI architecture
The OSI communication protocol layers of the ITS-OCC CI are:
a) Physical layer (PHY); and
b) Medium access control sub-layer (MAC).
An ITS-OCC CI as specified in this document is an ITS wireless CI

— of MedType 12; The ASN.1 type of MedType shall be ITSatt, specified in ISO 17419 for ITS-ATT —

see also the NOTE below;
— of CI class CIC-il3, specified in ISO 21218;
— of CI access class CIAC-1, specified in ISO 21218.

NOTE The parameter MedType was originally specified in the first edition of ISO 21218 and then continued

in ISO 17419 with the new name ITS-ATT. Values 0 through 11, 128, 254, and 255 are already assigned values

presented in ISO 17419. The next available value 12 is thus used for ITS-OCC CIs.

An ITS-OCC CI shall provide the functionality of the IN-SAP specified in ISO 21218, and uses the

functionality of an MI-SAP, and an SI-SAP, as specified in ISO 21218 and ISO 24102-3.

ASN.1 definitions applicable for ITS-OCC shall be as specified in Annex D.
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ISO 22738:2020(E)
6.2 ITS-S service access points
6.2.1 General

As service access points (SAPs) by definition describe functional behaviour only, SAPs may be

implemented in different ways. Requirements set up in this document to support SAPs and the related

service primitives thus mean to support the functionality. This support may be implemented either in a

strict meaning or in an implementation-specific way.
6.2.2 Communications SAPs
An ITS-OCC CI shall support the IN-SAP functionality specified in ISO 21218.
6.2.3 Management SAPs

An ITS-OCC CI shall support the MI-SAP functionality of ISO 24102-3, taking into account details

specified in ISO 21218, and may implement this functionality in a strict way conformant with ISO 21217

and ISO 21218, but also in different ways supporting other station architectures.

The general specification of MI-COMMANDs is provided in ISO 24102-3. The applicability for ITS-OCC

shall be as specified in Annex B.

The general specification of MI-REQUESTs is provided in ISO 24102-3. The applicability for ITS-OCC

shall be as specified in Annex B.
6.2.4 Security SAPs

An ITS-OCC CI shall support the SI-SAP functionality of ISO 24102-3, taking into account details

specified in ISO 21218.

NOTE At the time of publishing this document, ISO 21218 did not yet specify any security details.

6.3 Hybrid communications support

An ITS-OCC CI shall support the hybrid communications functionality of ISO 21218 and may implement

this functionality in a strict way conformant with ISO 21217 and ISO 21218, but also in different ways

supporting other station architectures.
7 Communication interface protocol stack
7.1 Communication interface parameters

Communication interface parameters for the general case are specified in ISO 21218. Additional details

that are specific to ITS-OCC shall be as specified in Annex A.
7.2 Physical layer

The configuration of the OCC PHY layer shall be implemented via the configuration of PHY PIB attributes

as specified in IEEE 802.15.7 (see Table 2).
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ISO 22738:2020(E)
Table 2 — PHY PIB attributes
Attribute Type Range Description ISO 21188 I-parameter
phyOccMcsID Integer 0–15 This attribute identifies Part of medium-specific
the OCC modulation when parameter OperationalMode,
phyOccEnable = 1: see A.2
0: UFSOOK
1: Twinkle VPPM
2: S2-PSK (5 bps)
3: HS-PSK (22 kbps)
4: Offset-VPWM
5–15: Reserved
phyDim Integer 0–1 000 This attribute specifies Part of medium-specific
the dimming level in steps parameter OperationalMode,
of 0,1 %. see A.2

Dependent on the value of phyOccMcsID, the configuration of individual PHY modes shall be implemented

as presented in Table 3 for S2-PSK, and in Table 4 for HS-PSK.
Table 3 — PHY PIB attribute configuration of S2-PSK
OCC Attribute Type Range Description
phyS2pskNoLightSources Integer 0–3 The number of light sources used
to modulate the S2-PSK signal.
0: two light sources
1–3: Reserved
phyS2pskModulationRate Integer 0–7 This attribute specifies the modulation
frequency used for S2-PSK.
0: 200 Hz
2–7: Reserved
Table 4 — PHY PIB attribute configuration of HS-PSK
OCC Attribute Type Range Description
phyHSpskHighStreamMode Integer 0–7 The modulation of high data stream.
0: DS8-PSK mode
1: DS10-PSK mode
2–7: Reserved
phyHSpskModulationRate Integer 0–7 This attribute specifies the modulation
frequency used for S2-PSK and DSM-PSK
of HS-PSK.
0: 200 Hz for S2-PSK and 80 kHz
for DS8-PSK
1: 200 Hz for S2-PSK and 400 kHz
for DS8-PSK
2–7: Reserved
phyHSpskLowDim Integer 0-500 This attribute specifies the low
dimming level of DSM-PSK
phyHSpskHighDim Integer 500–1 000 This attribute specifies the high
dimming level of DSM-PSK
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ISO 22738:2020(E)
Table 4 (continued)
OCC Attribute Type Range Description
phyHSpskPsduLength Integer — This is to specify the length of the
high-speed link of HS-PSK.
7.3 Data link layer
7.3.1 General

The basic behaviour of the ITS-OCC CI data link layer shall be as specified in IEEE 802.15.7.

7.3.2 Communication adaptation sub-layer

The communication adaptation sub-layer (CAL) is introduced in ISO 21218. The major task of CAL is

to provide the IN-SAP. ASN.1 details of the IN-SAP IN-UNITDATA service primitives are specified in

ISO 21218.
8 Communication interface management
8.1 General management
The basic management of an ITS-OCC CI shall be as specified in IEEE 802.15.7.
8.2 Management adaptation entity
8.2.1 OCC parameters and I-Parameters
In implementations conformant with ISO 21218, the following rules apply:

— OCC parameters (PHY PIB) that have an equivalent I-Parameter defined in ISO 21218 shall be

mapped on I-Parameters as specified in Annex A.

— OCC parameters (PHY PIB) which are relevant for ITS-OCC and do not have an equivalent I-Parameter

defined in ISO 21218 shall be made visible to the ITS station management by means of medium-

specific I-Parameters as specified in Annex A.

— I-Parameters which are relevant for ITS-OCC but cannot be mapped on an OCC parameter shall be

implemented in the MAE as specified in ISO 21218, taking into account details specified in Annex A.

8.2.2 OCC management commands and MI-SAP commands and requests

In implementations conformant with ISO 21218 and ISO 24102-3, the following rules apply:

— OCC management commands that have an equivalent MI-COMMAND / MI-REQUEST defined in

ISO 24102-3 shall be mapped on these MI-COMMAND / MI-REQUEST as specified in Annex B and

Annex C.

— OCC management commands that are relevant for an implementation of ITS-OCC and do not have

an equivalent MI-COMMAND / MI-REQUEST defined in ISO 24102-3 shall be made accessible

...