As shown, the cellular base station may initially wait for a ‘defer’ period after determining that the medium is available. In the illustrated example scenario, such a period may last for 43 μs (e.g., 16 μs+3*9 μs), though other lengths of time are also possible (e.g., for different priority levels or for any of various other reasons). After the defer period, if the medium is still available, the cellular base station may begin a contention period, in which the cellular base station may randomly (or pseudorandomly) select a contention window value within a specified range (which may similarly depend on priority level and/or any of various other considerations). In the illustrated example scenario, the contention window may be 7 Wi-Fi slots. During each Wi-Fi slot of the contention window, the cellular base station may perform carrier sensing to determine if the medium is still available. If it is determined that the medium is still available, the backoff counter may be reduced by one and the process may continue in the next Wi-Fi slot. Once the backoff counter reaches 0, the cellular base station may begin transmitting a reservation signal on the medium. The reservation signal may be transmitted until the next cellular slot boundary, at which time the cellular base station may perform cellular communication on the unlicensed frequency channel, such as LTE LAA data transfer with one or more UE devices.