Accurate knowledge of radio channel and network conditions — When does it matter?

One of the main motivations of wireless communication between vehicles is to establish a mutual awareness among vehicles. Such awareness is achieved through the periodic exchange of broadcast messages with information about the current position, heading or speed of a vehicle. The probability that neighboring vehicles receive such messages successfully depends on the current radio channel and network conditions. However, those conditions are not constant but varying due to the wide range of propagation environments, the number of vehicles in the surroundings and the transmission behavior of each vehicle. In order to cope with the current conditions and to achieve a desired communication reliability, communication protocols will have to be dynamically adjusted, e.g. by adjusting transmit power and transmit rate. The questions are therefore: how accurate do vehicles need to know the conditions and in which situations do they need to know them? This paper gives clarifications to those questions by means of a simulation-based sensitivity analysis, and in addition, surveys different methods of obtaining the required knowledge about radio channel and network conditions.