A spectrum management system comprising: circuitry (1601, 1603, 1605) configured to obtain resource information of a primary communication system, the information including an interference tolerance of the primary communication system, obtain resource information of a secondary communication system and a desired communication quality for the secondary communication system, estimate a critical region of the primary communication system based on resource information of the primary communication system and resource information of the secondary communication system, the critical region of the primary communication system being one or more regions with a lower communication quality in a coverage area of the primary communication system due to interference of the secondary communication system, estimate a critical region of the secondary communication system based on resource information of the primary communication system and resource information of the secondary communication system, the critical region of the secondary communication system being one or more regions with a lower communication quality in a coverage area of the secondary communication system due to interference of the primary communication system,, assess an optimum communication quality available to the secondary communication system over the available resources in the critical region of the secondary communication system, and allocate resources to the secondary communication system based on a comparison of the optimum communication quality of the secondary communication system if the available resources are used and the desired communication quality; wherein if the optimum communication quality of the secondary communication system is above the desired communication quality, the circuitry is configured to allocate a subset of the available resources to the secondary communication system. circuitry (1601, 1603, 1605) configured to obtain resource information of a primary communication system, the information including an interference tolerance of the primary communication system, obtain resource information of a secondary communication system and a desired communication quality for the secondary communication system, estimate a critical region of the primary communication system based on resource information of the primary communication system and resource information of the secondary communication system, the critical region of the primary communication system being one or more regions with a lower communication quality in a coverage area of the primary communication system due to interference of the secondary communication system, estimate a critical region of the secondary communication system based on resource information of the primary communication system and resource information of the secondary communication system, the critical region of the secondary communication system being one or more regions with a lower communication quality in a coverage area of the secondary communication system due to interference of the primary communication system,, assess an optimum communication quality available to the secondary communication system over the available resources in the critical region of the secondary communication system, and allocate resources to the secondary communication system based on a comparison of the optimum communication quality of the secondary communication system if the available resources are used and the desired communication quality; obtain resource information of a primary communication system, the information including an interference tolerance of the primary communication system, obtain resource information of a secondary communication system and a desired communication quality for the secondary communication system, estimate a critical region of the primary communication system based on resource information of the primary communication system and resource information of the secondary communication system, the critical region of the primary communication system being one or more regions with a lower communication quality in a coverage area of the primary communication system due to interference of the secondary communication system, estimate a critical region of the secondary communication system based on resource information of the primary communication system and resource information of the secondary communication system, the critical region of the secondary communication system being one or more regions with a lower communication quality in a coverage area of the secondary communication system due to interference of the primary communication system,, assess an optimum communication quality available to the secondary communication system over the available resources in the critical region of the secondary communication system, and allocate resources to the secondary communication system based on a comparison of the optimum communication quality of the secondary communication system if the available resources are used and the desired communication quality; wherein if the optimum communication quality of the secondary communication system is above the desired communication quality, the circuitry is configured to allocate a subset of the available resources to the secondary communication system.