Danger in round-trip delay

10 November 2005

Some more detail about one of the car-to-car comms systems demonstrated at the ITS World Congress this week comes via digital map specialist Navteq.

The experimental system built into two BMW cars is called Vehicle Infrastructure Integration (VII) and is backed by Navteq, BMW, Motorola and Volkswagen.

VII uses a centralised approach, according to Navteq: “Prototype vehicles [send] vehicle sensor data to the processing centre. Once processed, this data [is] broadcasted and displayed on VII-enabled navigation systems in prototype vehicles. [At the ITS event] Motorola will demonstrate the output of this processing through a website that displays the location and severity of road hazards on Navteq maps.”

While the broadcast and subscribe model is the only way to pool data for maps, it is surprising that there is not a peer-to-peer element. Perhaps there is, and Navteq neglects to mention it.

In life or death situations milliseconds may count, and the round-trip delay involved in sending a message to a central co-ordinating centre and back will be unavoidable. Not counting processing time, a round trip to a processing centre just 10 miles away cannot take less than 100 microseconds.

Direct communication between cars on the same piece of road has to be desirable if this kind of work is to prevent motorway pile-ups, for example.

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