Techniques and devices are described for wireless communication. A base station may determine a parameter associated with a transmission such as hybrid automatic repeat request (HARQ) feedback, a signal-to-noise ratio, or a determination regarding whether the transmission was successfully decoded. The base station may then determine a contention window adjustment value based on the parameter. The base station may then apply weighting factor (e.g., based on the time of the transmission, a number of devices being served, aspects of the transmission parameter, etc.) to the contention window adjustment value may adjust a contention window size for a second transmission based on the weighted contention window adjustment value (and, in some cases, other weighted adjustments based on other transmissions). The base station may then perform a clear channel assessment (CCA) based on the contention window size.