We present an approach to distributing messages among highly mobile hosts in ad hoc networks. We focus on using direct radio communication between moving vehicles on the road that requires no additional infrastructure. Thus, the vehicles need to organize access to the radio channel in a decentralized manner. We derive the medium access control from the standard IEEE 802.11. Also, the vehicles use omnidirectional antennas implying that a sender can transmit to multiple hosts simultaneously. As an example, we study a road accident that is reported to nearby vehicles. Simulations show us the quality of the proposed protocol by measuring how many vehicles inside a zoneof -relevance are informed under various conditions. 1

This thesis proposes the use of a new routing paradigm to enable communication in highly mobile, ad hoc networks, which operate wirelessly in the absence of dedicated master stations or fixed infrastructure. Due to the mobility of the nodes, the network topology changes frequently and unpredictably. We explore the new routing paradigm in the context of inter-vehicle communication. In such highly mobile ad hoc networks, the nodes commonly do not know the identity of their communication partners in advance. Rapid topology changes and scarce bandwidth prevent the nodes from exchanging updates regularly throughout the network. Therefore, we advocate a new routing paradigm that implicitly addresses message destinations based on the current situation of the network. [...]

We present an approach to multicast messages among highly mobile hosts in ad hoc networks. We suggest a new definition of a multicast that suits the special needs of inter-vehicle communication: rather than explicit identification, a multicast group is defined implicitly by location, speed, driving direction and time. As an example, we study a road accident that is reported to nearby vehicles. We focus on sparse deployment of the system which is likely to occur soon after the system is introduced to the market. In this state, the resulting ad hoc network tends to be disconnected. We tailor the proposed algorithm to overcome this problem of network fragmentation. Simulations show us the quality of the proposed protocol by measuring how many vehicles inside a multicast area are informed in time under various conditions. Index Terms: Inter-vehicle communication, mobile ad hoc network, multicast, global positioning system. I.