Some Ownership Management Issues in Distributed Simulation using HLA/RTI

Abstract

To study the High Level Architecture (HLA) and the services that are provided by the Runtime Infrastructure (RTI), in particular Object Management and Ownership Management, we have developed a distributed air traffic controller simulator. In our simulation model, each airport is represented by a federate and controls a number of aircraft. The control of the aircraft is transferred among airports as the aircraft fly to different airports. In this paper we discuss two different approaches that we have used to facilitate the exchange of ownership of aircraft attributes among federates, namely the pull and the negotiated push method. We present a comparison of the two methods and also discuss the problems associated with each method and our approach to resolving them. These problems include the oscillation effect, which causes aircraft attributes to be pulled back and forth between federates, and the pending attribute acquisition requests, which result in loss of aircraft (or unattended aircraft attributes). We have experienced that in such scenarios, the push method is more efficient and accurate. We also present our experiences and observations from our experimentation with the RTI. We have noticed some shortcomings in the current RTI interface specification that we will discuss in the paper.