Existing position-based unicast routing algorithms, where packets are forwarded in the geographic direction of the destination, require that the forwarding node knows the positions of all neighbors in its transmission range. This information on direct neighbors is gained by observing beacon messages each node sends out periodically. The transmission of beacons and the storage of neighbor information consumes resources. Due to mobility, collected neighbor information can quickly get outdated which in turn can lead to packet drops. In this paper, we propose a mechanism to perform position-based forwarding without the help of beacons or the maintenance of neighbor tables. In our contention-based forwarding scheme(CBF) the next hop is selected through a distributed contention process using biased timers. To avoid packet duplication, the first node that is selected suppresses the selection of further nodes. We propose three suppression strategies which vary with respect to forwarding efficiency and suppression characteristics. We analyze the behavior of CBF with all three suppression strategies and compare it to an existing greedy routing approach by means of simulation with ns-2. Our results demonstrate that CBF is a promising strategy for position-based routing
