Abstract: A wireless access unit (12) for providing an interface between a satellite communications system (32) and a plurality of terrestrial user devices (14-26) in a centralized or distributed architecture includes a spectrum allocation unit (92) for dynamically allocating spectrum to the plurality of terrestrial user devices (14-26) based on a spectral environment about the wireless access unit (12). A spectrum scan unit (60) scans the spectral environment about the wireless access unit (12) and generates a spectrum signal indicative thereof. An environment understanding unit (61) provides signal information corresponding to signal emitters in proximity to the distributed or centralized network. A spectrum table (90) assembles data related to the spectral environment and the proximity emitters for use by the spectrum allocation unit (92) in dynamically allocating spectrum.