CommunicationNetworkSimulator

Many simulators broaden their applicability by allowing customized interactions with third-party components, and SimMobility is no exception. In addition to traditional library-based extension, SimMobility ST provides a TCP socket integration layer that allows other software system to interact with a running SimMobility ST simulation. This is primarily used to overlay Android emulators running transit-related applications or "apps" onto existing SimMobility agents, thus providing accurate location information to the apps. In return, the apps provide more realistic within-day re-routing, creating a feedback loop which should optimize the system. The choice to communicate over TCP sockets has several advantages. First, it requires minimal changes to existing third-party software systems - usually only a small communication module is needed. Second, it facilitates interactions between a larger number of simulators. In the example just discussed, SimMobility ST connects to a running instance of a network simulator (ns-3), which it uses to provide accurate timing and packet loss information for messages sent between Android clients. Finally, the use of TCP sockets provides a stable, cross-platform means of interaction with clearly defined boundaries.