In this paper, broadband wireless LAN (WLAN), the representative model of broadband wireless IP network, is taken as a target of the research and analysis. The influence of the variation of transmission power and data rate on the bit error rate (BER) performance of the broadband modulation schemes in a typical indoor application environment of non - cell wireless communications is explored and analyzed. An associated power - rate control scheme is presented based on the analysis and the practical design consideration.