Directional and cooperative spectrum occupancy measurements in the 2.4 GHz ISM band

This paper presents directional and cooperative spectrum occupancy measurements in the 2.4 GHz industrial, scientific and medical band. Spectrum occupancy characterises the efficiency of spectrum use in terms of identifying the proportion of time that a given frequency channel is occupied. Directional spectrum occupancy measurements are carried out using two separately located measurement devices with directional antennas to capture the influence of the spatial dimension on the spectrum use. The measurements from the different antennas are further combined using decision fusion techniques to get cooperative spectrum occupancies that give a more accurate view of the actual spectrum use. The resulting directional and cooperative spectrum occupancies are valuable input to the development of future cognitive radio systems where unoccupied channels could be accessed opportunistically. The measurements results indicate that the spectrum occupancy can vary significantly in the same office environment depending on the measurement location and direction.