Radio interference in ITS

13. November 2014

The European DSRC technology, mainly used for road tolling, was standardized by CEN TC278 WG9 in the 1990's:

as an efficient technology for roadside-vehicle communications at 5,8 GHz using semi-passive transponder technology.

DSRC based EFC became a "cash cow" collecting money from road users not just in Europe. DSRC is one of the technologies required by the European Commission for the European Electronic Toll Service (EETS).

Obviously the nearby frequency bands at 5,9 GHz allocated for road safety and traffic efficiency may severely degrade the cash-flow function. Surprisingly it is not the DSRC "On-Board Unit" (OBU) with a receiver bandwidth of about 100 MHz that is primarily affected, but it is the DSRC "Road-Side Unit" (RSU) that suffers significantly due to its extremly high receiver sensitivity.

ETSI TC ITS intensively investigated in the interference effects, and proposed a number of mitigation techniques to reduce or totally eliminate the degrading impact of 5,9 GHz IEEE 802.11 communications on CEN DSRC. Well, we can lead back and smile!

This interference problem was known at ISO already more than a decade ago, when the design of the ITS station as Bounded Secured and Managed Domain with several access technologies and multiple instances of each one started. Part of this domain management is radio interference management, which requires management protocols at the side of the communication protocol stacks (ISO 24102-1).

This is another late proof of the excellent design of CALM with the station and communication architecture being standarized in ISO 21217. And, by the way, early mitigation techniques already had been implemented in the EC's CVIS project that validated ISO CALM standards. For day-1 deployment: the ISO CALM working group (TC204 WG16) developed a consistent set of communication and station management standards which can be used from 2015 on; and CALM is continuing the work towards the next release.

There is only one single word, and one single ITS!

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