Evaluation of Shadowing Effect on Channel Observation for Spectrum Sharing Access

Spectrum sharing, in which multiple wireless systems share the same radio resources, has been considered to improve frequency utilization efficiency. As a spectrum sharing without control signals, a technique that observes the usage of radio resources, called channel occupation ratio, used by other systems and selects a vacant channel has been considered. However, previous studies have simplified the model of the interfering system, which is different from the real environment. In wireless communications, fluctuations in received power occur due to shadowing caused by the location and the surrounding environment. Previous studies have not clarified the effect of received power fluctuation due to shadowing on observing the occupancy rate. This letter formulates the effects on the observation results of received power fluctuations due to the location of interfering stations and shadowing. Computer simulations with randomly placed interfering stations and shadowing environments show that the proposed formulation almost matches the observed results.