We propose in this paper a new approach of bit-free control frames to improving the performance of the IEEE 802.11 DCF. Basically, a bit-free control frame does not contain any meaningful bits; instead, its length (i.e., airtime) is encoded with the control information. This new approach has two advantages over the traditional control frames. First, the airtime of a bit-free frame is easy to detect and robust against channel effects. Second, bit-free control frames can be very short because no headers or preambles are needed for them. Our investigation demonstrates that the new approach improves the performance of the IEEE 802.11 DCF significantly (network throughput gains from fifteen to more than one hundred percent).