In described embodiments, a channel allocation system, such as a white space channel allocation system, employs a server processor and database to record communication characteristics of incumbent service providers licensed or otherwise registered to operate within certain frequency spectrum. The channel allocation system allows registration of licensed service providers, or access to existing licensed service provider databases, to obtain required information of communication characteristics to form protected service contours. Based on the protected service contours, the availability of channels in areas is pre-computed. In addition, unlicensed or unregistered users, such as TV band devices (TVBDs), register with the channel allocation system and request channel lists of channels to operate on with a query. The system performs an iterative search of areas with successively finer resolution and identifies channels that might be included in a channel list in response to the query.