Abstract. This paper presents the validation methodology established and applied during the development of a wireless LAN application. The target of the development is the implementation of the hardware physical layer of the HIPERLAN/2 wireless LAN protocol and its interface with the upper layers. The implementation of the physical layer (modem) has been validated in two different levels. First, at the functional level, the modem was validated by a high-level UML model. Then, at the implementation level, a new validation framework drives the validation procedure at three different sub-levels of design abstraction (numerical representation, VHDL coding, FPGA-based prototyping). Using this validation methodology, the prototype of the HIPERLAN/2 modem has been designed and validated successfully.