In accordance with an embodiment a method for performing carrier sense multiple access with collision avoidance (CSMA-CA) by a station in a wireless communications network includes determining, in accordance with transmission information related to previous transmission attempts, a rate of success for each window section of a plurality of window sections, selecting a window section in accordance with at least the rate of success for each of the window sections and at least one predetermined threshold, and transmitting data after a back-off delay selected from within the selected window section.