Telecommun Syst DOI 10.1007/s11235-013-9708-z Study the effect of PAPR on wideband cognitive OFDM radio networks Hefdhallah Sakran · Mona Shokair · El Sayed El-Rabaie · Omar Nasr © Springer Science+Business Media New York 2013 Abstract Cognitive radio (CR) technology is viewed as a novel approach for maximizing the utilization of the ra- dio electromagnetic spectrum. Spectrum sensing methods are often used for finding free channels to be used by CR. Recently, Orthogonal Frequency Division Multiplexing sys- tem (OFDM) has been suggested as a candidate technology for multicarrier-based CR systems. However, one problem that appears in OFDM systems is the high Peak to Average Power Ratio (PAPR). In this paper, the effect of PAPR reduc- tion of the primary signal on the performance of the multi- band joint detection for wideband spectrum sensing and the profit of the primary user will be investigated. Moreover, the optimal solutions for the multi-band joint detection for the non-cooperative and cooperative schemes will be analyzed by considering the primary user’s PAPR reduction. Also, the wideband cooperative spectrum sensing to improve the sig- nal detection with high reduction in the PAPR will be sug- gested. Simulation results show that the PAPR reduction de- creases the total price of the primary user and the aggregate opportunistic throughput of the secondary user. The coop- erative scheme is effective in improving the performance in terms of the aggregate opportunistic throughput with PAPR reduction. H. Sakran ( ) · M. Shokair · E.S. El-Rabaie Faculty of Engineering, IBB University, IBB, Yemen e-mail: hefdh_sakran@yahoo.com M. Shokair e-mail: i_shokair@yahoo.com E.S. El-Rabaie e-mail: srabie1@yahoo.com O. Nasr Faculty of Engineering, Cairo University, Giza, Egypt e-mail: omaranasr@ieee.org Keywords PAPR · Cognitive OFDM · Cooperative spectrum sensing · Energy decision scheme 1 Introduction The number of wireless applications have been growing over the last decade. Most of the frequency spectrum has already been licensed by government agencies, such as Federal Communications Commission (FCC). Therefore, there is an apparent spectrum scarcity for new wireless applications and services. CR [1–3] has been considered as a key mech- anism in addressing the problem of spectrum scarcity [4–6] in wireless communication systems. Spectrum sensing [7, 8] is the most important task among others for establishing the CRs because they need to sense the spectrum and decide to use the spectrum band if a spectrum hole exists, which is described in detail in [9–12]. In addition, they need to sense the spectrum periodically to sense the primary user reap- pearance. Actually, because of the attractive features of OFDM sys- tems, it has been successfully used in numerous wireless standards and technologies. It plays an important role in realizing the cognitive radio concept as well by providing a proven, scalable, and adaptive technology for the air in- terface [13]. The challenges of OFDM based CR can be grouped into three categories which are described in details in [14]. One of these categories is related to PAPR reduc- tion and the effect of this reduction on the spectrum sensing. The problem of reducing PAPR occurring in cognitive radio has been studied before [15–19]. Qingwen in [15] proposed new adaptive algorithm with low complexity. This new adaptive algorithm is based on combining between adaptive PAPR reduction technology and power adjustment. Selec- tive Mapping Method (SLM) is another technique to reduce