Impact of Erroneous Transmission on Secondary Spectrum Access

Sammanfattning: The rapid development and deployment of wireless devices demand for the efficient spectrum usage to ensure quality of service. Thus, regulatory bodies opened new dimensions regarding the sharing of spectrum among the owners, keeping the respect of exclusive users as a primary objective. The main concern of secondary spectrum access is to protect primary licensed user from harmful interference of secondary devices. Accordingly, there are some rules to control interference aggregation to the primary victim, and this is accomplished by characterizing the aggregate interference. Statistical models of interference aggregation have been considered in previous studied. But, in real systems, secondary users do not follow the rules all the time and there might be erroneous transmission due to different reasons. In this thesis we developed a statistical model of aggregate interference when we take erroneous transmissions into account. In addition, probability distribution of the aggregate interference is approximated through its cumulants. The derived approximation shows a good agreement with Monte Carlo simulation result in tail region under specific conditions. It is also shown that even a single wrongdoer may dramatically degrade spectrum sharing opportunities particularly when it is relatively close to the primary receiver depending on the transmitted power to the victim receiver. Finally, impacts of erroneous transmission on the secondary access under variations in the density of opportunistic users and their probability of wrong transmission are investigated.