Due to limited frequency resources, frequency reuse must be used to deploy 26-GHz band fixed wireless access (FWA) systems in expanding service areas. In this case, the co-channel interference from other zones using the same frequency channel is a serious problem. We propose a TDMA/TDD frame timing control method that avoids co-channel interference. The method employs the frame error rate (FER) to detect the co-channel interference, and, if the access point (AP) detects interference, the AP shifts the timing of the TDMA/TDD frame by a random delay. This method is performed at each AP independently and asynchronously. Based on simulations, we effectively optimize the FER threshold for detection of co-channel interference. We also show the effectiveness of avoiding co-channel interference and suppressing throughput degradation.