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Fahimeh Jasbi - IEEE Xplore Author Profile

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Cognitive radio allows secondary users (SUs) to exploit the underutilized radio spectrum of the primary networks. To fully utilize the primary spectrum and maximize spectral efficiency, overlay and underlay transmissions, which exploit the white and gray spaces, respectively, should be used together. However, for underlay, the SUs need to transmit at low power to avoid causing harmful interference...Show More
This paper proposes the use of an overloaded hybrid MC-CDMA system to improve the spectral efficiency of Cognitive Radio (CR) network. The overlay transmission in the unused parts of the spectrum is full-loaded MC-CDMA signals with scrambling. The underlay signal, using a separate scrambling code from the overlay signals, utilizes the whole spectrum taking into account of the interference threshol...Show More
Cognitive Radio (CR) aims to access the spectrum opportunistically mainly by two access strategies, overlay and underlay. Overlay can utilize the spectrum whenever the primary system is off. On the other hand, underlay can utilize the spectrum at any time with considering the interference limit of the primary system. However, by using hybrid methods and performing proper equalization technique, sp...Show More