In technical literature and especially in domestic, predominant way to examine performance of 802.11a-based systems are experiments in simulations. In this paper, we present FPGA based 802.11a prototype, which gave us a possibility to gain closer insight into the problems of OFDM system implementation. A specific design of base band modem physical layer is discussed, along with the presentation of the FPGA prototyping platform on which it was developed. Prototype is implemented on the latest generation of FPGA chips, using state-of-the-art tools for DSP development. Custom made development environment, and design flow optimized for rapid prototyping of software defined radios, are also presented in the paper.