Overview
ISO 29281-2:2019 - "Intelligent transport systems - Localized communications - Part 2: Legacy system support" defines how Intelligent Transport Systems (ITS) support legacy Dedicated Short Range Communication (DSRC) application-layer services specified in ISO 15628. The standard specifies architectures, procedures and facility-layer protocols that enable ISO 15628 DSRC applications to operate over ITS station (ITS‑S) access technologies suited for localized communications, while interoperating with ITS station management and networking services.
Key topics and technical requirements
- Legacy CI support: Defines how an existing access technology can be represented as a 15628 legacy CI inside an ITS station so that legacy DSRC peers (not aware of ITS context) can be supported.
- ITS station architecture compliance: Requires conformance with the ITS station and ITS-SCU concepts in ISO 21217 and management interfaces in ISO 24102.
- Adaptation layers and forwarding: Uses the Fast Networking & Transport Protocol (FNTP) (ISO 29281‑1) for packet forwarding between the access layer and facilities layer; specifies a Communication Adaptation Layer (CAL) extension for FNTP support.
- Facilities-layer entities:
- Legacy CI Port Agent - port abstraction to connect legacy service entities to the ITS facilities layer.
- 15628 Kernel Emulator - emulates the ISO 15628 T‑Kernel interface for legacy applications and maps 15628 flow control semantics to ITS VCIs (BC‑VCI and UC‑VCI).
- FSAP integration - uses the Fast Service Announcement Protocol (ISO 22418) for initialization (BST/VST ↔ FSAM/FSRM exchanges).
- I‑Parameters and registration: Introduces dedicated I‑Parameters (e.g., LegacyOption, PortPA) to classify legacy operational options and identify Legacy CI Port Agent ports.
- Conformance and test methods: Specifies conformance declaration and test methods; normative ASN.1 and legacy CI definitions are provided in annexes.
Applications and users
ISO 29281‑2 is intended for organizations deploying or integrating ITS localized communications where legacy DSRC systems must be supported. Typical users:
- ITS equipment manufacturers (roadside units, vehicle OBUs) implementing hybrid DSRC/CAL/FNTP stacks
- System integrators migrating legacy DSRC deployments into ITS networks
- Test houses and certification bodies verifying conformance and interoperability
- Standards bodies and traffic authorities planning backward-compatible ITS rollouts
Related standards
- ISO 15628 - DSRC application layer (legacy service definitions)
- ISO 21217 / ISO 21218 - ITS station architecture and access technology support
- ISO 22418 - Fast Service Announcement Protocol (FSAP)
- ISO 29281-1 - Fast networking & transport layer protocol (FNTP)
- ISO 24102 series - ITS station management
Keywords: ISO 29281-2, ITS localized communications, legacy DSRC, ISO 15628, Legacy CI Port Agent, 15628 Kernel Emulator, FNTP, FSAP, ITS station.
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