The bidirectional transmission based-protocols have been proposed to resolve an uplink (UL)/downlink (DL) unfairness problem of an infrastructure mode WLAN. However, they do not guarantee the fairness in an error-prone channel. We propose two protocols enhancing the UL/DL fairness, named negative acknowledgement (NACK)-based channel reservation and hybrid automatic repeat request-based bidirectional media access control (MAC) (HyBiM). We analyze the throughput of the two protocols by proposing a new Markov chain model. The analytical and simulation results show that the HyBiM protocol guarantees the UL/DL fairness even in the error-prone channel.