In designing WLAN MAC protocols, several issues must be considered. Among them, the hidden-terminal and exposed-terminal problems are two of the most important issues. The hidden-terminal problem has been analyzed by many researchers and significant improvements have been made. The exposed-terminal problem, however, has not been fully considered in the design of WLAN MAC protocols. In this paper, we propose two protocols. In the first one, referred to as channel splitting protocol, the channel is split into two subchannels--the control channel and the data channel--to solve several problems inherent in existing protocols, including hidden terminal and exposed terminal problems. With channel splitting, a control frame is transmitted through the control channel alternatively of a data frame which is transmitted through the data channel. In the second protocol, referred to as RTR/ATR reservation protocol, hosts that want to transmit data reserve several slotted data channels in advance to increase performance, while the first protocol reserves only one transmission. In the second protocol, control frames are transmitted through the control channel independently of data frames. The performance of the proposed protocols is evaluated by simulation and compared with existing protocols.