Nowadays WiMax is becoming one of the main standards for the next generation wireless transmission systems. It provides QoS mechanism, but it needs performance optimization and evaluation and it is very difficult to make coverage prediction. This paper is about QoS estimation methods and measurements over WiMax networks. It presents first performance measurements about achievable rates for data or multimedia transmission, and estimations of the fading due to buildings, metal, glass, natural obstacles, vegetation, weather conditions and speed. We then present a synchronization method to derive end to end delay measurements