A method controls the operation of devices which communicate over a wireless communications channel. The method includes determining a parameter of a received signal communicated over the wireless communications channel and determining a minimum threshold value of the received signal. An average duration of fade is determined using the parameter and the minimum threshold. The method detects whether the received signal is less than the minimum threshold value. At least one of the devices is placed in a sleep mode for approximately the average duration of fade in response to the received signal being detected as less than the minimum threshold value. The determined parameter of the received signal may be the root mean square value of the received signal.