In this paper a flexible concept for simulator coupling is introduced which permits the whole system simulation of distributed systems, e.g. of complex communication systems. In our approach we use different languages (Matlab-Code, VHDL, oTcl, C/C++) and combine the specialized simulators Matlab/Simulink, ModelSim and the network simulator NS-2. Matlab/Simulink and ModelSim are shipped with a powerful foreign language interface and for NS-2 we developed a solution for including user written functions. The simulators are extended with a special coupling component implemented in C/C++. The simulator coupling bases on TCP/IP sockets, so that the simulation of the model parts can run on different host computers using different platforms.