Systems, methods, and devices for operating a multiplex wireless local area network using separated uplink and downlink channels in the 802.11 and television white space (TVWS) spectra are disclosed. Opportunistic detection and use of available TVWS frequency channels allows for fixed and mobile wireless devices to more efficiently use the available wireless bandwidth. By using separated uplink and downlink channels, a fixed wireless device can listen to incoming uplink frames from other mobile and fixed wireless devices and monitor for uplink frame collisions. In the event of an uplink frame collision, the fixed wireless device can immediately send a stop frame in the downlink channel to all involved wireless devices to avoid lost channel time due to the delay caused by most acknowledgement-based collision recovery protocols. Similarly, communicating mobile and fixed wireless devices can transmit and receive data frames in both directions simultaneously.