A novel forwarding paradigm for position-based routing (with implicit addressing)

Existing position-based unicast routing algorithms, which forward packets 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. Due to mobility, the information that a node receives about its neighbors becomes outdated, leading either to a significant decrease in the packet delivery rate or to a steep increase in load on the wireless channel as node mobility increases. We describe a mechanism to perform position-based unicast forwarding without the help of beacons. In our contention-based forwarding (CBF) scheme, the next hop is selected through a distributed contention process based on the actual positions of all current neighbors. For the contention process, CBF makes use of biased timers. To avoid packet duplication, the first node that is selected suppresses the selection of further nodes. Since the basic scheme can lead to packet duplication, we describe alternative ways of suppressing those. In addition to that, we compare the CBF schemes and standard greedy forwarding by means of simulation with ns-2.