A node is configured for connection to a massive multiple-input, multiple-output (MIMO) array to provide spatially multiplexed channels in an unlicensed frequency band. The node includes a memory configured to store samples of non-spatially filtered signals received by the node during a first listen-before-talk (LBT) operation used to acquire the unlicensed frequency band. The node also includes a processor configured to determine, based on a number of previously stored samples, a duration of a silent time interval during which the node collects samples of non-spatially filtered signals and stores the samples in the memory. The node further includes a transceiver configured to perform a second LBT operation to acquire the unlicensed frequency band using a spatial filter determined based on the samples stored in the memory.