The Radio Frequency Spectrum
The Radio Frequency spectrum is in the range of frequencies from 3 kHz to 300 GHz and is a finite resource that is used for wireless communications and services. Demands for wireless communication in consumer electronics and personal high data rate networks are continuously increasing, as have quality of service requirements in terms of throughput, reliability, and availability of wireless services. It is expected that there will be a considerable increase in the number of devices making use of different wireless standards and technologies in the future. On the one hand, there will be greater provision and access to broadband multimedia services but on the other hand getting multiple heterogeneous radio systems to coexist harmoniously in a shared spectrum is challenging.
The Spectrum Utilization Database should provide TV White Space devices with available channels and power limitations in UHF and VHF bands based on their location.
As a finite resource, it is important that the frequency spectrum is used and managed carefully. Government agencies throughout the world regulate Spectrum usage and assign portions of the spectrum over time and covering large geographical areas to license holders or for certain services. [Spectrum usage is congested in particular regions of the spectrum space whilst others are totally underutilized.]
In the first years of research for TV White Space spectrum sensing methods were developed and implemented for TV signal detection and several companies sent their prototype devices to be tested by regulators. However, after regulators determined that the use of spectrum sensing as a stand-alone method could not sufficiently protect incumbent TV spectrum users research into the use of Spectrum Databases began to develop.
Currently, databases are the dominant dynamic spectrum sharing approach for TV White Space. However, there are still many challenges left for Satellite bands since the characteristics of satellite and signals differ from terrestrial systems.
Databases take their signals from national FS Registries, gain information about FSS terminals, and calculate where and how FSS users can be allowed to operate in the bands. The objective is to find least congested channels; to determine spectrum utilization; and, subsequently, to provide TV White Space devices with available channels and power specifications in the UHF and VHF bands based on location and to prevent unlicensed users from interfering with licensed UHF and VHF users.