Study on Energy Detection-based Cooperative Sensing in Cognitive Radio Networks Rania Mokhtar Department of Electronic Engineering, Faculty of Engineering Sudan University of Science and Technology, Khartoum, Sudan Email: rania@ieee.org 1 Rashid Saeed, 2* Raed Alsaqour, and 3 Yahia Abdallah 1 Faculty of Engineering, Sudan University of Science and Technology (SUST), Khartoum, Sudan 2 Faculty of Information Science and Technology, University Kebangsaan Malaysia, Bangi, 43600, Selangor, Malaysia 3 Email: Faculty of Computer Science and Information Technology, Sudan University of Science and Technology, Khartoum, Sudan 1 eng_rashid@ieee.org, 2 raed@ftsm.ukm.my, 3 yahia@sustech.edu Abstract—Cognitive radio (CR) technology aims to achieve efficient radio spectrum utilization based on overlay spectrum sharing. Therefore, one of the main requirements of CR systems is the capability to detect and sense the presence of primary transmissions. However, sensing is affected by the behavior of the wireless channel, i.e., hidden node, interference, shadowing, and fading, which may result in wrong detection decisions. Consequently, CRs may introduce harmful interference to primary radios. Cooperative spectrum sensing can improve detection decisions by obtaining sensing information from different sources, which has been recently proposed to overcome this problem. This paper reviews cooperative sensing aspects, approaches, architecture, as well as problematic aspect and drawbacks of the control channel and associated fusion methods. Index Terms—Cognitive radio; spectrum sensing; cooperative sensing; data fusion I. INTRODUCTION The basic problem concerning spectrum sensing is the signal detection within a noisy measure. The performance of local spectrum sensing techniques is limited by the received signal strength. Spectrum sensing in a cognitive radio (CR) node (local sensing) is associated with several challenges [1]. The channel state information among a primary transmitter, a receiver, and a receiver location is unknown to a CR. The hidden node problem can arise when a blockage exists between the TV whitespace device and a TV station, but no blockage exists between the TV station and a TV receiver antenna and between the unlicensed device and the same TV receiver antenna. In such a case, a CR may not detect the presence of a TV signal and can start using an occupied channel, causing harmful interference to the TV receiver. This problem increases the requirement in the CR sensitivity to a level that outperforms primary user (PU) receivers to the extent that it becomes capable of detecting weak signals. Local node sensing may achieve an acceptable sensing result only after an exceedingly long sensing time. Considering this limitation in local spectrum sensing, the cooperation among CRs is introduced for better accuracy of PU detection. Cooperation may solve of shadowing and hidden node problem [2], as shown in Fig. 1. Cooperation is considered as the key method for the realization of a CR. Figure 1. Cooperative detection Sensing can be improved by incorporating more observations from other CRs at various locations. Network cooperation can improve sensing performance compared with local sensing, whereby cooperative sensing enhances the detection and reduces the probability of interference to a PU. Cooperative sensing is based on the fact that summing signals from two CRs can improve detection reliability by increasing the signal- to-noise ratio (SNR) if signals are correlated [3]. Cooperative spectrum sensing exploits the broadcast nature and spatial diversity of the channel. In cooperative sensing, CR receivers may estimate channel variations resulting from fading, noise, and interference by relaying messages to one another. These messages propagate redundant signals over multiple paths in the network [4]. Realization of CR and white space standard [3] employs a set of applications, such as relay channels, distributed antenna arrays, localization methods, data exchange and fusion methods as well as collaborative mapping. Cooperative sensing can be implemented in different ways based on the cooperation method and network architecture. Cooperative sensing methods JOURNAL OF NETWORKS, VOL. 8, NO. 6, JUNE 2013 1255 © 2013 ACADEMY PUBLISHER doi:10.4304/jnw.8.6.1255-1261