Wireless network simulators have become a fundamental tool to study, evaluate and improve wireless networks. The quick evolution of wireless technology involves the necessity of continuous changes and updates in these simulators which makes them more complicated and time demanding. Regarding software design, wireless network simulators are generally based on the object-oriented paradigm. However, the use of more advanced programming techniques (such as UML and design patterns) is still an issue for further research. This paper discusses the application of design patterns in a HSDPA system simulator, pointing the suitable pattern and its application place in the wireless system. We focus on the strategy pattern whose implementation is showed in two points of the simulator: the scheduler and the radio channel. Strategy pattern allows us to change the scheduling mechanism or the radio channel even in execution time and simplifies the inclusion of new scheduling schemes or new radio channels.