Modelling of Dead Reckoning and Heartbeat Update Mechanisms in Distributed Interactive Simulation

Dead reckoning is employed in Advanced Distributed Simulation exercises to reduce the need to continually update a simulated entity’s state information. The IEEE Distributed Interactive Simulation (DIS) protocol provides a standard set of 11 algorithms for entity position and orientation dead reckoning. Related to dead reckoning is the heartbeat mechanism used to periodically define the current state of an entity. The IEEE standard defines heartbeat rates for many Protocol Data Units (PDUs) with default values specified for rate of issuance of heartbeat PDUs and timeout. Both the dead reckoning and heartbeat mechanisms are required to maintain continuity of entities within a distributed simulation exercise. To study dead reckoning and heartbeat, a model was developed that simulates these two mechanisms within DIS for entity position. This model can perform sensitivity analysis on the critical parameters, such as entity speed, heartbeat rate and dead reckoning threshold for different dead reckoning algorithms. The model demonstrated that the second order algorithm using acceleration and velocity is far more efficient than the first order algorithm that used only velocity. Third order algorithms that use rate of change of acceleration were also studied and shown to offer only marginal improvement while requiring additional computational resources. The model also demonstrated that the default values for threshold are too small for fast moving entities such as aircraft and can be used to determine more appropriate values. The fraction of heartbeat to dead reckoning PDUs was examined for several different entity types (tank, aircraft, missile) with appropriate settings for threshold and heartbeat rate. It was shown that the use of a fixed heartbeat rate is not appropriate for all entity types and that heartbeat PDUs predominate for high values of threshold. The model also shows that issuance of heartbeat PDUs depends on which dead reckoning algorithm is used: if an efficient algorithm that requires few dead reckoning PDUs is adopted, more heartbeat PDUs are then required to maintain the entity within the simulation exercise.