A Quantitative Analysis of Spectral Occupancy Measurements for Cognitive Radio

Cognitive radio (CR) is viewed as a possible solution to the problem of radio spectrum congestion. The CR technique utilizes a temporarily unoccupied licensed band. Before investigating the technical and political implications of CR, it is necessary to know to what extent the licensed bands are temporally unoccupied. This paper describes a spectral occupancy measurement campaign conducted in the frequency range between 806 MHz and 2750 MHz in urban Auckland, New Zealand. The purpose of the measurement is to identify potential spectral opportunities for CR. Statistical analysis of the measurement results are presented in the form of noise distributions, signal amplitude probability distributions, and spectral occupancy rates as percentages of time. These analyses indicate that, on average, the actual spectral usage in this band is only about 6.2%. Pint-to-point links and some mobile uplink channels are identified as the most probable candidates for future CR operations. These results suggest that CR could bring significant gains in spectral usage. These results also imply that, in order to provide a reliable detection of the primary signal, cooperative sensing techniques may be necessary to mitigate various wireless channel effects.