Overview
ISO 21218:2018 - "Intelligent transport systems - Hybrid communications - Access technology support" defines the access-layer technical details for ITS station implementations. It complements the ITS station reference architecture in ISO 21217 by standardizing how communication interfaces (CIs) are adapted, managed and exposed to higher layers. The standard documents the service access points (SAPs) for communication (IN‑SAP) and for management (MI‑SAP), associated service primitives and functions, and references management primitives in ISO 24102‑3.
Keywords: ISO 21218:2018, intelligent transport systems, ITS, hybrid communications, access layer, IN‑SAP, MI‑SAP, communication interface, communication adaptation layer.
Key Topics and Requirements
- Communication module adaptation: roles of the Communication Adaptation Layer (CAL), CI Management Adaptation Entity (MAE) and CI Security Adaptation Entity to present a uniform access layer.
- Communication Interface (CI) architecture and classification: CI classes, access classes and link identifiers to support heterogeneous radio/physical technologies.
- CI procedures and states: registration, deregistration, activation, inactivation, suspension, resuming, connection/disconnection and CI state machine behavior.
- Virtual Communication Interface (VCI): concepts and procedures for creation, reset, deletion and association between VCIs and physical Link‑IDs.
- Communication SAP (IN‑SAP): addressing schemes, service primitives (e.g., IN‑UNITDATA.request/indication/STATUS), priority handling, timeouts, queue management and transmission status reporting.
- Management SAP (MI‑SAP): MI‑COMMAND and MI‑REQUEST primitives (examples in the standard include ChangePseudonymMACaddress, CIstateChange, CnConnect, MonitorIparameters, PrioritizationRequest/Release, RegulatoryInformation, VCImanagement).
- Supportive content: normative annexes on I‑Parameters, ASN.1 definitions, extended identifiers, path/flow management, conformance and test methods, and an Implementation Conformance Statement (ICS) proforma.
Practical Applications and Users
ISO 21218:2018 is intended for:
- ITS platform and stack implementers who need a standardized access layer for hybrid multi‑radio systems.
- Device manufacturers (OBUs, RSUs) integrating multiple access technologies (cellular, DSRC/C‑ITS, ITS‑G5, etc.).
- System integrators and test labs validating CI behavior, conformance, interoperability and performance against ITS station reference architecture.
- Standard writers and architects mapping higher-level ITS services to underlying access technologies.
Using ISO 21218 helps ensure consistent hybrid communications, predictable priorities, manageability of interfaces, and smoother interoperability across ITS deployments.
Related Standards
- ISO 21217 - ITS station reference architecture (defines overall architecture referenced by ISO 21218)
- ISO 24102‑3 - Management service primitives referenced by MI‑SAP
Keywords (SEO): hybrid communications, access technology support, ITS access layer, IN‑SAP MI‑SAP, ISO ITS standards.