Mustafa E. Sahin

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— Femtocells have a strong potential for increasing the efficiency and coverage of next-generation broadband wireless networks. In this paper, a co-channel framework for the coexistence of orthogonal frequency division multiple access (OFDMA) based macrocell and femtocell wireless networks is proposed. It is based on utilizing the resource blocks of(More)
— Accurate detection of spectrum opportunities within the frequency band of an orthogonal frequency division multiple access (OFDMA) system carries critical importance for OFDMA-based cognitive radios. In this paper, we analyze the opportunity detection performances of energy detection and ESPRIT (estimation of signal parameters by rotational invariance(More)
— Accurate detection of spectrum opportunities within the frequency band of an orthogonal frequency division multiple access (OFDMA) system is a critical requirement for the realization of a coexisting cognitive radio. In this paper, we analyze the opportunity detection performances of energy detection and ESPRIT algorithms in the presence of timing(More)
— Cognitive radio is an enabling technology for efficient utilization of radio spectrum. In this paper, an orthogonal frequency division multiple access (OFDMA) based cognitive (opportunistic) network is considered, which co-exists with a macrocell network through utilizing its unused subcarriers. We particularly consider the uplink opportunity detection(More)
Coexistence of narrowband (NB) and multicarrier technologies will be a major concern in next generation wireless communication systems due to the co-channel interference (CCI) problem. In this paper, an efficient CCI cancellation method is proposed that may be utilized for improved coexistence of NB and multicarrier technologies. The method treats both(More)
In this paper, joint estimation of the optimal threshold, synchronization point, and integration interval is developed for ultrawideband (UWB) energy detectors employing on-off keying (OOK) modulation. Gaussian approximation of the received signal statistics is shown to enable low complexity solutions at the expense of some performance degradation. The(More)
— Spectrum awareness of orthogonal frequency division multiple access (OFDMA) based cognitive radios (CR) can be improved by enabling them to separate the primary user signals in the uplink (UL). Assuming availability of information about the basic parameters of the primary system as well as time synchronization to the first arriving user signal, two(More)
— Separating user signals in the uplink (UL) of an orthogonal frequency division multiple access (OFDMA) system without access to the subcarrier assignment scheme (SAS) is a challenging task, but it can have a number of useful applications. In this paper, a semi-blind user separation algorithm is proposed, which assumes time synchronization and availability(More)
In a continuously expanding wireless world, the number of radio systems increases every day, and efficient spectrum usage becomes a more significant requirement. Ultrawideband (UWB) and cognitive radio are two exciting technologies that offer new approaches to the spectrum usage. The main objective of this paper is to shed the first light on the marriage of(More)