20 sonuçlar
Arama Sonuçları
Listeleniyor 1 - 10 / 20
Yayın On the extraction of the channel allocation information in spectrum pooling systems(IEEE, 2007-04) Öner, Mustafa Mengüç; Jondral, Friedrich K.The spectrum pooling strategy allows a license owner to share a part of his licensed spectrum with a secondary wireless system (the rental system, RS) during its idle times. The coexistence of two mobile systems on the same frequency band poses many new challenges, one of which is the reliable extraction of the channel allocation information (CAI), i.e. the channel occupation of the licensed system (LS). This paper presents a strategy for the extraction of the CAI based on exploiting the distinct cyclostationary characteristics of the LS and RS signals and demonstrates, via simulations, its application on a specific spectrum pooling scenario, where the LS is a GSM network and the RS is an OFDM based WLAN system.Yayın On the effect of random sampling jitter on cyclostationarity based spectrum sensing algorithms for cognitive radio(IEEE, 2009) Öner, Mustafa MengüçCognitive radio is an enabling technology, which is expected to lead to a more efficient utilization of the available spectral resources due to its flexibility and its ability to sense its spectral environment. Recently, spectrum sensing methods based on exploiting the cyclostationary characteristics of communication signals have been drawing considerable interest. Imperfections in the cognitive radio receiver that affect the cyclic statistics of a signal of interest may lead to a degradation in the performance of spectrum sensing algorithms based on cyclostationarity. One such typical source of imperfection is random timing jitter in the sampling process. In this work, we explore the effect of random sampling jitter on the second order cyclostationary statistics of wide sense cyclostationary signals. General analytical expressions are derived for the cyclic statistics of sampled signals in the presence of sampling jitter and specific results are provided for two cases of interest. Subsequently, the effect of the jitter on a spectrum sensing algorithm is investigated via simulations.Yayın On the effects of random timing jitter on spectrum sensing algorithms based on cyclostationarity(IEEE, 2009) Öner, Mustafa MengüçCognitive radio is an enabling technology, which is expected to lead to a more efficient utilization of the available spectral resources due to its flexibility and its ability to sense its spectral environment. Recently, spectrum sensing methods based on exploiting the cyclostationary characteristics of communication signals have been drawing interest. In practice, imperfections in the signal generation or reception may affect the cyclic statistics of a signal of interest, leading to a degradation in the performance of cyclostationarity-exploiting spectrum sensing schemes based on an ideal signal model. A typical source of imperfection is random timing jitter, which can occur at the transmitter side, most notably in the form of pulse timing jitter for digitally modulated signals, or at the receiver side in the form of sampling jitter. In this work, we explore the effect of random timing jitter on the second order cyclostationary statistics of wide sense cyclostationary signals. General analytical expressions are derived for the cyclic statistics of signals in the presence of sampling and pulse timing jitter and specific results are provided for cases of practical interest. Subsequently, the effect of the both jitter types on a cyclostationary-based spectrum sensing algorithm is investigated via simulations.Yayın Automatic modulation classification for mimo systems using fourth-order cumulants(IEEE, 2012) Mühlhaus, Michael S.; Öner, Mustafa Mengüç; Dobre, Octavia Adina; Jkel, Holger U.; Jondral, Friedrich K.Automatic classification of the modulation type of an unknown communication signal is a challenging task, with applications in both commercial and military contexts, such as spectrum surveillance, cognitive radio, and electronic warfare systems. Most of the automatic modulation classification (AMC) algorithms found in the literature assume that the signal of interest has been transmitted using a single antenna. In this paper, a novel AMC algorithm for multiple input multiple output (MIMO) signals is proposed, which employs fourth-order cumulants as features for classification. First, perfect channel state information (CSI) is assumed. Subsequently, a case of more practical relevance is considered, where the channel matrix is unknown and has to be estimated blindly by employing independent component analysis (ICA). The performance of the proposed classification algorithm is investigated through simulations and compared with an average likelihood ratio test (ALRT) which can be considered as optimum in the Bayesian sense, but has a very high computational complexity.Yayın Spectral correlation of a digital pulse stream modulated by a cyclostationary sequence in the presence of timing jitter(IEEE-INST Electrical Electronics Engineers Inc, 2009-02) Öner, Mustafa MengüçCyclostationarity is an inherent characteristic of many communication signals, which can be exploited for performing various signal processing tasks. Imperfections in the signal generation that affect the cyclic statistics of a signal may lead to a degradation in the performance of signal processing algorithms which make use of this cyclostationary behaviour. One typical source of imperfection encountered in digital signalling techniques is random jitter in the pulse timing. In this work, we systematically derive analytical expressions for the cyclic statistics of digital baseband signalling schemes in the presence of timing jitter, under the assumption that the generating wide sense cyclostationary data sequence and the stationary jitter process are statistically independent.Yayın MIMO sinyalleri için uzay-zaman blok kodu klasifikasyonu(IEEE, 2014-04-26) Turan, Merve; Öner, Mustafa Mengüç; Çırpan, Hakan AliBilinmeyen haberleşme sinyallerinin gözü kapalı ve işbirliksiz tanınması için geliştirilen teknikler, hem askeri hem de sivil uygulamalarda kullanım bulmuştur. Çok Girdili Çok Çıktılı (MIMO) haberleşme sistemleri, sinyal tanıma sistemleri için üstesinden gelinmesi gereken yeni problemler ortaya koymaktadır. MIMO haberleşmesinde kullanılan uzay zaman kodlarının gözükapalı tanınması bu problemlerin en önemlilerinden biri olarak görülebilir. Bu çalışmada uzay zaman blok kodlanmış sinyal vektörlerinin döngüsel-durağan (cyclostationary) karakteristiklerinin farklı uzay zaman blok kodlarını birbirinden ayırdetmek amacıyla kullanıldığı yenilikçi uzay-zaman kodu tanıma algoritmaları öneriyoruz.Yayın Joint modulation classification and antenna number detection for MIMO systems(IEEE, 2016-01-07) Turan, Merve; Öner, Mustafa Mengüç; Çırpan, Hakan AliNoncooperative classification of the modulation type of communication signals finds application in both civilian and military contexts. Existing modulation classification methods for multiple-input multiple-output (MIMO) communication systems commonly require a priori information on the number of transmit antennas employed by the multiantenna transmitter, which, in most of the noncooperative scenarios involving modulation classification, is unknown and needs to be blindly extracted from the received signal. Since the problems of MIMO modulation classification and detection of the number of transmit antennas are highly coupled, we propose a decision theoretic approach for spatial multiplexing MIMO systems that considers these two tasks as a joint multiple hypothesis testing problem. The proposed method exhibits a high performance even in moderate to low SNR regimes while requiring no a priori knowledge of the channel state information and the noise variance.Yayın Signal identification for multiple-antenna wireless systems: achievements and challenges(IEEE, 2016-01-18) Eldemerdash, Yahia A.; Dobre, Octavia Adina; Öner, Mustafa MengüçSignal identification is an umbrella term for signal processing techniques designed for the identification of the transmission parameters of unknown or partially known communication signals. Initially a key technology for military applications such as signal interception, radio surveillance and electronic warfare, signal identification techniques recently found applications in commercial wireless communications as an enabling technology for cognitive receivers. With the advance and rapid adoption of multiple-input multiple-output (MIMO) communication systems in the last decade, extension of signal identification methods to include this transmission paradigm has become a priority and focus of intensive research efforts. The aim of this work is to provide a comprehensive state-of-the-art survey on algorithms proposed for the new and challenging signal identification problems specific to MIMO systems, including space-time block code (STBC) identification, MIMO modulation identification, and detection of the number of transmit antennas. Finally, concluding remarks on MIMO signal identification are provided along with an outline of the open problems and future research directions.Yayın A low complexity modulation classification algorithm for MIMO systems(IEEE-INST Electrical Electronics Engineers Inc, 2013-10) Mühlhaus, Michael S.; Öner, Mustafa Mengüç; Dobre, Octavia Adina; Jondral, Friedrich K.A novel algorithm is proposed for automatic modulation classification in multiple-input multiple-output spatial multiplexing systems, which employs fourth-order cumulants of the estimated transmit signal streams as discriminating features and a likelihood ratio test (LRT) for decision making. The asymptotic likelihood function of the estimated feature vector is analytically derived and used with the LRT. Hence, the algorithm can be considered as asymptotically optimal for the employed feature vector when the channel matrix and noise variance are known. Both the case with perfect channel knowledge and the practically more relevant case with blind channel estimation are considered. The results show that the proposed algorithm provides a good classification performance while exhibiting a significantly lower computational complexity when compared with conventional algorithms.Yayın Air interface identification for Software Radio systems(Elsevier GMBH, 2007) Öner, Mustafa Mengüç; Jondral, Friedrich K.Reconfigurable Software Radio (SR) equipment is considered as the next evolutionary step in the mobile communications. One of the most crucial properties of a SR terminal is that it is capable of using a wide range of air interface standards, providing a seamless interoperability between different standards and an enhanced roaming capability, paving way to a more flexible and efficient use of spectral resources. This multimode operation has to be supported by a number of key functionalities, one of which is the air interface identification. A SR terminal, when switched on, has to be able to locate and identify the air interfaces available in the frequency environment, and while connected to a network, it has to monitor the presence of alternative air interfaces to perform interstandard handover if necessary. In our work, we propose exploiting the distinct cyclostationary properties of signals from different air interfaces as features for air interface identification.
