A method of operating a communication system, said method being performed on a server and comprising: determining an available spectrum of frequencies within a location over time, comprising determining, by the server, a geospatial usage of a spectrum with respect to time based on an expected spectrum usage of registered devices over time and based on a measured and/or estimated usage of the spectrum by unregistered devices and based on historical usage of the spectrum within the location, wherein registered devices are devices that are accessing or that are expected to access the spectrum within said location; receiving a request from a wireless device to access spectrum for a predefined duration at a first level of service; and determining whether sufficient spectrum is available to enable the wireless device to operate at the first level of service, wherein, upon a determination that sufficient spectrum is not available to enable the wireless device to operate at the first level of service, said method further comprises: determining whether sufficient spectrum is available to enable the wireless device to operate at a second level of service that is lower than the first level of service; selecting, by a processor within the communication system, a frequency band within the spectrum that is available to be used by the wireless device for the predefined duration at the second level of service; and transmitting an authorization message to the wireless device to use the selected frequency band. determining an available spectrum of frequencies within a location over time, comprising determining, by the server, a geospatial usage of a spectrum with respect to time based on an expected spectrum usage of registered devices over time and based on a measured and/or estimated usage of the spectrum by unregistered devices and based on historical usage of the spectrum within the location, wherein registered devices are devices that are accessing or that are expected to access the spectrum within said location; receiving a request from a wireless device to access spectrum for a predefined duration at a first level of service; and determining whether sufficient spectrum is available to enable the wireless device to operate at the first level of service, wherein, upon a determination that sufficient spectrum is not available to enable the wireless device to operate at the first level of service, said method further comprises: determining whether sufficient spectrum is available to enable the wireless device to operate at a second level of service that is lower than the first level of service; selecting, by a processor within the communication system, a frequency band within the spectrum that is available to be used by the wireless device for the predefined duration at the second level of service; and transmitting an authorization message to the wireless device to use the selected frequency band. determining whether sufficient spectrum is available to enable the wireless device to operate at a second level of service that is lower than the first level of service; selecting, by a processor within the communication system, a frequency band within the spectrum that is available to be used by the wireless device for the predefined duration at the second level of service; and transmitting an authorization message to the wireless device to use the selected frequency band.