Applying IEEE 802. 11 MAC protocols in battery-powered devices make power consumption critical demand upon implementation. A statistical study on operator/bit usage, the weight of operator and operator type in the programs has been done, including converting the MAC functions from SDL to C to ASM with tow RISC targets. The study shows that implementing MAC functions should consider real-time protocol requirements by dividing MAC functions into sets. We enhance the set of time-critical functions implemented to dedicated hardware and the set of non-time-critical functions implemented to software run with embedded processor. This heterogeneous system is proposed in consideration of our study results to reduce power consumption.