Hybrid network synchronization for MANETs

Military radio networks such as mobile ad hoc networks (MANETs) usually rely on global satellite navigation systems (GNSSs) for network time synchronization. However, in reality all nodes may not have a GNSS timing device or they do not have a direct link to a GNSS timed node. In addition, in some situations GNSSs may fail. Therefore, additional supporting mechanisms are needed for synchronization. This paper provides a hybrid algorithm that uses GNSS timed nodes as master time servers if they are available but automatically turns to a distributed mode if GNSS time is not available providing robustness and survivability. Furthermore, the distributed mode can be used also as a stand-alone synchronization mechanism, i.e., a GNSS time reference is not necessarily needed at all. Simulations show the behavior of the algorithm in different scenarios but as main conclusions it can be said that the availability of GNSS timed nodes speeds up the initial convergence, the convergence rate depends on the number of nodes and the number of hops and that if GNSS time is lost, the network still maintains synchronism but time is not necessarily GNSS time.