Welcome to c-its.dev

This is the inaugural post of c-its.dev, an engineering notebook on Cooperative Intelligent Transport Systems. The unglamorous middle of the cooperative-mobility stack: ASN.1 UPER decoders, C-ITS PKI tooling, GNSS error budgets, CAN bus diagnostics, the kind of things you find out about by reading three ETSI specifications, two Wireshark dissectors, and finally the C++ source of a reference encoder at 2 AM.

The rest of this post is a short manifesto so you know what to expect.

Who this is for

Engineers who already know what a CAM is, and who want to understand how the implementation decisions behind one shape the system they’re building. We’re going to talk about hexadecimal payloads, certificate validity windows, Kalman gain tuning, the specific way ETSI TS 103 097 encodes geographic restrictions, and the reasons your DENM might pass UPER validation while still being semantically wrong.

This is not a vendor blog. There is nothing to sell here. The site has no tracking, no newsletter, and no comment section.

What you’ll find here

A non-exhaustive list of topics:

• ETSI C-ITS message sets — CAM, DENM, CPM, VAM, MAPEM, SPATEM, IVIM, SREM, SSEM. Field-by-field, with the implementation gotchas that the standard documents tend to underplay.
• GNSS for V2X — error models, multipath in urban canyons, RTK and PPP-RTK from the receiver-side perspective, integration with IMUs. Always with the V2X positioning requirement in the background.
• PKI — the C-ITS trust model in TS 102 941, AT pseudonym rotation strategies, the operational reality of running an EA or AA, the European Certificate Trust List (ECTL) and its quirks.
• CAN and SDV — bus diagnostics seen from a connected vehicle, the slow migration from CAN to zonal architectures, automotive Ethernet, how SDV reshapes what a vehicle-side V2X stack looks like.
• Sensor fusion — what is actually achievable at sub-second latency, the limits of cooperative perception vs. on-board perception, where CPM fits and where it doesn’t.
• ADAS — same idea but from the function side: how V2X data can or can’t feed an ADAS function without compromising safety arguments.

Everything is written through the V2X lens. GNSS posts will be about GNSS for V2X positioning; CAN posts will be about CAN seen from the ego of a connected vehicle. The cooperative angle is what unifies the topics here.

Format

Posts are long. There are no 600-word teaser posts that link out to a gated whitepaper. Either there’s something to say, in which case it’s said in full, or there isn’t, in which case nothing is written. No schedule, no newsletter.

Where useful, posts embed interactive widgets — small but real tools the reader can poke at while reading. The next post, ETSI C-ITS message set — a 5-minute tour, has one of these.

How to follow

There’s an RSS feed. There’s no email list. There are no analytics beyond the standard server access logs, which aren’t kept long.

Onward to the actual technical posts.