Next generation mobile wireless systems (4G) support a wide range of communication protocols and services opening new design challenges. The desired flexibility requires an effective utilization of system resources. In this paper, we introduce the concept of system scenarios in wireless communication baseband engines. The scenario methodology classifies the system behavior from a cost perspective and provides the necessary information for an effective system tuning. Apart from the case study, we propose improvements at the detection of the scenarios at run time achieving a better tradeoff between cost estimation accuracy and detection overhead. From our case study, a representative example the WLAN communication protocol, we can demonstrate the accurate prediction of the execution time of each packet, which on average is 90% shorter than the worst case, allowing us to use the remaining time for the optimization of specifications like power consumption.