D22.51 Communication requirements
This document describes communication and networking features and protocol functions for a safety related vehicular ad-hoc network. The main application for this automotive WLAN, besides hotspot interconnect during stops in parking areas and gas stations, are safety related communications such as obstacle and hazard warning. The nature of the network with many highly mobile nodes in the absence of a central network controller demands distributed networking algorithms. Combined with the demands of a safety relevant application the focus points of the WILLWARN networking architecture are on
- extremely fast channel acquisition
- short messages only. The synchronization issues related to long-term connections between vehicles and roadside units are beyond the scope of WILLWARN.
- broadcast communication with a possibility to flood messages towards a defined area and obtain indications that messages are received from passing cars rather than disappearing in areas with a low ratio of equipped vehicles
- strict priority handling to cope with both network congestion and environmental conditions such as accidents or road blockage, that need immediate preference of safety related network traffic.
- Local communication only, thereby excluding the vast research area of mobile IP, internet gateways on the road etc.
- Non-centralized network where the backbone connection of road side units is out of scope.
Considering the market introduction of a car-to-car communication system, it seems inevitable to include private/commercial WLAN applications reusing the WILLWARN hardware. A promising approach is the 5.9GHz dedicated short range communication concept recently adopted by the FCC, which currently stimulates considerable development efforts from the industry as well as state departments and road authorities.