Speed-up techniques for simulation

Due to increased complexity and extreme quality of service requirements, traditional means for performance evaluation of telecom networks do not always suffice. The most flexible approach has been, and still is, simulation, which is the main focus of this paper. However, severe problems regarding efficiency exist, e.g. evaluation of ATM cell loss rate in range of <10-9 which is very computer intensive and hardly feasible within reasonable time with direct simulation. This calls for new and more efficient simulation techniques. An overview of some speed-up approaches is given. The paper also includes a simple quantitative comparison study of three novel techniques; importance sampling, RESTART and transition splitting. As an example of practical use, a technique combining three speed-up approaches is described at the end of this paper. It is prepared for both simulation and realtime measurements.