In some examples, a method includes transmitting frames over a wireless channel after a first backoff period has elapsed. The method also includes estimating a channel condition of the wireless channel over a plurality of time slots. The method also includes determining, in case of an unsuccessful transmission of the frames, whether the unsuccessful transmission is attributed to a frame collision. The method also includes determining a second backoff period based on at least the estimated channel condition if the unsuccessful transmission is not attributed to a frame collision.