Research On Hybrid Multicast-unicast Assignment Algorithm In DDM

The main focus of data distribution management (DDM) in HLA is to reduce theamount of data received by federates in large-scale distributed simulations. Some ofexisting DDM schemes only use multicast communication, some only use unicastcommunication, some use a mix of multicast and unicast communication. Even thoughcommunication protocol selection strategies used by these DDM schemes can solve someproblems, there are also some drawbacks. The first drawback is that limited number ofmulticast groups is not considered; the second is that amount of network bandwidth isoccupied; the third is that advantages of multicast and unicast are used fully. Therefore,this paper aims to research communication protocol strategy used by DDM to improve theperformance of DDM.The use of limited multicast resources plays a key role in the performance of DDM.Considering advantages and disadvantages of multicast and unicast, this paper tries to usemulticast and unicast synthetically to improve the performance of DDM. So a hybridmulticast-unicast data transmission problem and its formal definition are presented, andthen a hybrid multicast-unicast assignment approach is proposed. The approach uses anew adaptive communication protocol selection (ACPS) strategy to utilize the advantagesof multicast and unicast, avoid their disadvantages, and consider the inter-relationshipbetween connections. It includes the ACPS static assignment algorithm used by staticassignment and the ACPS dynamic assignment algorithm used by dynamic assignment,according to the difference between the static connections and the dynamic connections.In our approach, a concept of distance is presented to measure the inter-relationshipbetween connections for multicast and the message redundancy for unicast, which is thecore of the two algorithms in order to gather the connections to a multicast group or tobalance the use of unicast and multicast for best performance. As a result, our algorithms can more effectively decide whether a new connection should use unicast or multicastcommunication, and whether adjusting previous assignment result can further improve theperformance. In addition, a control mechanism is introduced to deal with connectionchanges during the dynamic assignment.The experiment results indicate that our algorithms can utilize the multicast andunicast communication resources effectively, as well as can achieve better performancethan existing methods in the real running environment.