In beaconing systems such as AIS or ADS-B, used by ships and aircraft, each node periodically broadcasts its navigational state to nearby nodes to increase traffic safety. Nowadays these beacons are also used as a source for satellite-based global traffic monitoring. This dual use imposes competing needs on the medium access control protocol as the size of the collision domains varies by a large factor between the use cases. Even the subproblem of solely avoiding terrestrial nodes’ packets to collide from the perspective of a receiving satellite is not trivial to solve if the satellite’s collision domain spans multiple hops in the terrestrial network. Based on ideas of the LAMA protocol, we propose CAMELAMA, a novel contention-free medium access control protocol for position awareness beaconing. Our low-overhead approach uses neither forwarding of node state nor handshakes but only the navigational data that is shared between the terrestrial nodes anyway. CAMELAMA provides local cooperative awareness while at the same time desynchronizing transmissions within a satellite’s collision domain even in terrestrially disconnected topologies. In a simulation-based performance evaluation we find that CAMELAMA outperforms SO-TDMA (the MAC protocol of AIS) and also scales better with respect to high node densities.
