In a method for determining whether a communication device can transmit via a first communication channel, the communication device receives a packet via a second communication channel and sets a network allocation vector (NAV) timer corresponding to the second communication channel using duration information included in the header of the packet. The communication device determines whether the second communication channel overlaps in frequency with a first communication channel. If the second communication channel overlaps the first communication channel, the communication device is not permitted to transmit via the first communication channel when the NAV timer is not zero. If the second communication channel does not overlap the first communication channel, the communication device is permitted to transmit via the second communication channel even when the NAV timer is not zero.