An introduction is given to the topics of the parallel and distributed simulation and of the modeling of telecommunications systems. Our practical modeling concept for simulation in heterogeneous execution environment is presented. Its logical topology is a star shaped network of homogeneous clusters. The load balancing and the coupling factor criteria are set up for building models of telecommunications systems so that the simulation may produce good speed-up in a heterogeneous distributed execution environment. A case study is given with the open source OMNeT++ discrete-event simulation system and its parallel CQN (closed queueing network) sample model executed by 64 CPU cores of four different types. Our criteria are heavily supported by the results of our experiments. © 2013 IEEE.