104 страниц. 2010 год. LAP Lambert Academic Publishing In this thesis, we present Position-based Highway-Optimized Geocast (?OG), an efficient, ad-hoc protocol for vehicle-to-vehicle geocasting of urgent warning messages along a highway. ?OG is an optimized position-based forwarding (PBF) protocol, i.e. messages are relayed via neighbors toward the destination. Position-based routing and geocasting protocols are well known, but previous works did not explore the ability to optimize their performance for the critical task of geocasting of alerts between vehicles along a highway. We present simulation results showing that the optimizations in ?OG significantly improve performance, compared to PBF protocols not optimized for geocasting over highways. Furthermore, we show that ?OG also significantly outperforms ODAM, one of the recent contention-based geocasting protocols. This is the first simulation-based comparison of (optimized) position-based and contentionbased geocasting protocols.