This patent describes methods and devices for spectrum sensing using sliding window energy detection. A sliding window energy detection test having a number of continuously-performed tests can be analyzed according to a desired cumulative false alarm rate to provide a corresponding, testing threshold. Based on the testing threshold and target signal to noise ratio, a testing window length is selected such that the sliding window energy detection is performed for a minimum expected discrete detection time. A sliding window energy detector can then obtain the selected testing window length and the corresponding, testing threshold for spectrum sensing.  The technology has been implemented in several IFT projects and hopefully many future products as well. This patent is the fifth approved IFT patent, and sixth granted patent by IFT Projects.