Robust transmission power and position estimation in cognitive radio

Abstract

As the wireless communication services grow quickly, the seriousness of spectrum scarcity has been on the rise gradually. Recently, the FCC (Federal Communications Commission) announced very interesting reports [1], [2]. It pointed out that more than 70% of radio spectrum is underutilized in certain times or geographic locations. This means that spectrum scarcity is not due to fundamental lack of spectrum but wasteful static spectrum allocations. A Cognitive Radio(CR), introduced by Joseph Mitola III [4], is receiving a great attention to overcome spectrum scarcity. However, unified definition of a CR and well-organized scenarios to be applied CR systems do not still exist. Thus, in this thesis, we regarded CRs as one of the spectrum sharing schemes and then categorized CR technologies. And we proposed the fundamental technology to exploit opportunistic resource. Especially the transmission power and position of the primary user in CR is very precious information because these information of the primary user determines the spatial resource. This opportunistic spatial resource is available to secondary users to exploit it. To find position of the primary user, we try to use existing positioning or localization schemes based on ranging techniques but those require the primary user’s transmission. Since most primary users in CR are legacy system, there are no beacon protocol to advertise useful information such as transmission power. Some of existing localization schemes don’t require the transmission power, but those don’t work in $It\{Outer case}$ that the primary user is out of convex hull of secondary users’ coordinates. We propose the constrained optimization method to estimate transmission power and position without the prior information of the transmission power. Also, we do extensive simulations on two major cases of network deployments to prove that the proposed constrained optimization method increases performance in mean square error(MSE) between true...