In described embodiments, a channel allocation system, such as a white space (WS) channel allocation system, employs a method to populate a WS database with channel availability information for areas with protected or otherwise registered service user information server. Communication characteristics of incumbent service providers licensed or otherwise registered to operate within certain frequency spectrum are plotted over a geographic area. The channel allocation system then divides the area into tiles, and determines whether each tile can be characterized for channel availability and, for those tiles that are uncharacterized, further divides the tiles into tiles of finer resolution. Based on information in the WS database, availability of channels in areas is pre-computed, and then an iterative search of areas with successively finer resolution identifies white space channels that might be included in the channel list in response to a query from a unlicensed or unregistered user.