Physical Communication 19 (2016) 84–92 Contents lists available at ScienceDirect Physical Communication journal homepage: www.elsevier.com/locate/phycom Full length article Impact of the knowledge of nodes’ positions on spectrum sensing strategies in cognitive networks Andrea Abrardo a , Marco Martalò b,c,∗ , Gianluigi Ferrari b a Department of Information Engineering, University of Siena, Siena, Italy b Wireless Ad-hoc Sensor Network Laboratory, Department of Information Engineering, University of Parma, Parma, Italy c E-Campus University, Novedrate (CO), Italy article info Article history: Received 30 June 2015 Received in revised form 10 November 2015 Accepted 12 December 2015 Available online 22 December 2015 Keywords: Cognitive networks Information fusion False alarm Missed detection Mutual information Correlated sources abstract In this paper, we focus on cognitive wireless networking, where a primary wireless network (PWN) is co-located with a cognitive (or secondary) wireless network (CWN). The shared frequency spectrum is divided into disjoint ‘‘subchannels’’ and each subchannel is ‘‘freely’’ assigned (in a unique way) to a node of the PWN, denoted as primary user equipment (PUE). We assume that the nodes of the CWN, denoted as cognitive user equipments (CUEs), cooperate to sense the frequency spectrum and estimate the idle subchannels which can be used by the CWN (i.e., assigned to CUEs) without interfering the PWN. The sensing correlation among the CUEs is exploited to improve the reliability of the decision, taken by a secondary fusion center (FC), on the occupation status (by a node of the PWN) of each subchannel. In this context, we compute the mutual information between the occupation status and the observations at the FC, with and without knowledge of the positions of the nodes in the network, showing a potential significant benefit brought by this side information. Then, we derive the fusion rules at the FC: our numerical results, in terms of the network-wise probabilities of missed detection (MD) and false alarm (FA) at the secondary FC, indicate a significant performance improvement when knowledge of the CUEs’ positions is available at the secondary FC, confirming the mutual information-based theoretical prediction. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Dynamic spectrum access has been proposed to provide efficient radio spectrum utilization [1–3]. In such systems, a portion of the spectrum can be allocated to one or more users, which are called primary user equipments (PUEs). Such spectrum, however, may not be exclusively ∗ Corresponding author at: Wireless Ad-hoc Sensor Network Labora- tory, Department of Information Engineering, University of Parma, Parma, Italy. E-mail addresses: abrardo@dii.unisi.it (A. Abrardo), marco.martalo@unipr.it (M. Martalò), gianluigi.ferrari@unipr.it (G. Ferrari). dedicated to PUEs, but could also be utilized, with lower priority, by secondary users, also denoted as cognitive user equipments (CUEs)—the notation comes from cellular systems where the proposed techniques can also be applied. In particular, CUEs can access the same spectrum (as long as the PUEs are not using it at that moment) or can share the spectrum with the PUEs (as long as the PUEs can be properly protected from undesired interference). By doing so, the radio spectrum can be reused in an opportunistic manner or shared all the time, thus significantly improving the spectrum utilization efficiency. To support dynamic spectrum access, CUEs are required to sense the radio environment, i.e., they also are cognitive radio users [4,5]. One of the main tasks of a CUE is represented by spectrum sensing, defined as the task of http://dx.doi.org/10.1016/j.phycom.2015.12.004 1874-4907/© 2015 Elsevier B.V. All rights reserved.