Koffi-Clement Yao - Academia.edu (original) (raw)

Papers by Koffi-Clement Yao

International Journal of Digital Information and Wireless Communications, 2018

Full-Duplex has been emerged in Cognitive Radio Network in order to avoid the silence period of t... more Full-Duplex has been emerged in Cognitive Radio Network in order to avoid the silence period of the Secondary User (SU) during the Spectrum Sensing. SU should monitor the Primary User (PU) activities in order to avoid any harmful interference. The conventional Full-Duplex Cognitive Radio (FD-CR) systems are based on the Self-Interference Cancellation, where a problem of Residual Self-Interference and Hardware Imperfections leads to an important loss in the detection performance. In this paper, we develop spectrum sensing techniques for FD-CR based on the Blind Source Separation (BSS). In BSS, multi receiving antennas are required to detect the presence of the Primary User (PU) signal without the need for a silence period during the spectrum sensing. This fact enhances the data rate of the SU. In addition, this algorithms do not require any priori knowledge about the SU or the PU signal. Experimental results show that in addition to eliminating the silence period, the performance of our developed algorithms based on BSS outperforms the classical spectrum sensing Energy Detector (ED).

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Copyright

HAL (Le Centre pour la Communication Scientifique Directe), Feb 1, 2000

This paper addresses the problem of non-cooperative spectrum sensing in very low signal noise rat... more This paper addresses the problem of non-cooperative spectrum sensing in very low signal noise ratio (SNR) conditions. In our approach, detecting an unoccupied bandwidth consists to detect the presence or absence of a communication signal on this bandwidth. Major well known communication signals may contain hidden periodicities, we use the Recurrence Quantification Analysis (RQA) to reveal the hidden periodicities. RQA is very sensitive to a reliable estimation of the phase space dimension m or the time delay τ. In view of the limitations of algorithms proposed in the literature, we have proposed a new algorithm to estimate simultaneously the optimal values of m and τ. The new proposed optimal values allow the states reconstruction of the observed signal and then the estimation of the distance matrix. This distance matrix has particular properties which we have exploited to propose the Recurrence Analysis based Detector (RAD). RAD can detect a communication signal in a very low SNR condition. Using Receiver Operating Characteristic curves, our experimental results corroborate the robustness of our proposed algorithm comparing to classical widely used algorithms.

HAL (Le Centre pour la Communication Scientifique Directe), Sep 3, 2018

In Cognitive Radio, spectrum sensing methods can be classified in three categories: temporal, fre... more In Cognitive Radio, spectrum sensing methods can be classified in three categories: temporal, frequential and hybrid (temporal and frequential) methods. Temporal methods require a long observation period; frequential and hybrid methods have a high calculation cost and they are very sensitive to frequency resolution. In very low signal-tonoise ratio (SNR) and non-cooperative conditions, spectrum sensing methods present some limitations. To overcome these shortcomings, we propose a new blind strategy to detect the unoccupied spectral bands during a very short observation period. This new strategy is a temporal method based on Recurrence Quantification Analysis (RQA) of the received signal. Since the recurrence level in a communication signal is different from that of White Gaussian Noise, the detector can evaluate the recurrence level of the observed signal to detect the presence of a communication signal over a given spectral bandwidth. First, we estimate the three fundamental parameters of the recurrence matrix: the time delay parameter, the embedding dimension and the recurrence threshold. With these parameters, during a detection stage, the detector evaluates the recurrence level through the recurrence rate and compare it to a predetermined threshold estimated in absence of the signal of interest. The spectrum sensing based on RQA is very fast, free of frequency resolution issue and able to distinguish communication signal from a White Gaussian Noise. The results of our simulations prove the robustness of proposed RQA detector acting over limited number of samples and under very low SNR conditions.

HAL (Le Centre pour la Communication Scientifique Directe), Oct 26, 2017

IEEE Transactions on Cognitive Communications and Networking, Sep 1, 2022

HAL (Le Centre pour la Communication Scientifique Directe), Sep 12, 2017

The detection of signal presence is a crucial job carried out through spectrum sensing in cogniti... more The detection of signal presence is a crucial job carried out through spectrum sensing in cognitive radio systems. A tradeoff between detection accuracy and detector complexity is tackled often in researches. Amongst different spectrum sensing techniques, conventional energy detection is widely used due to its simplicity of implementation, however, it is sensitivity to noise variation makes it unreliable in low signal-to-noise-ratio environments. This manuscript proposes the use of scattering-based detector for spectrum sensing in the context of cognitive radio to provide reliable signal detection. Through scattering transform, signal features are enhanced whereas noise variations effects are reduced which enhances the detection results. The proposed detector is tested for chirp and spread spectrum signals in additive white Gaussian noise channel. Performance evaluation is conducted through calculation of detection probability for several signal-to-noise ratio values. Through MonteCarlo simulations, the proposed detector proves reliability of detection as compared to energy detection which provides false detection decision when noise only considered for detection.

The blind recognition of communication parameters is an important research topic in both commerci... more The blind recognition of communication parameters is an important research topic in both commercial and civilian systems. In this paper, we investigate the blind recognition of the modulation. Currently most part of the existing algorithms assumes that the transmitter uses a single-antenna. This study extends the problem for multiple-antennas (MIMO) systems. We adopt a Maximum Likelihood approach for the blind recognition of the modulation and we consider two different situations. First, we assume the channel knowledge at the receiver side and we expose the optimal solution which is called Average Likelihood Ratio Test (ALRT). Then, we relax this assumption and we propose a second method based on a Hybrid Likelihood Ratio Test (HLRT).

This paper provides a novel blind spectrum sensing technique based on cepstral analysis in interw... more This paper provides a novel blind spectrum sensing technique based on cepstral analysis in interweave cognitive radio (CR) system. The main scope of this work is to mitigate the problem of weak signal detection so as to allow for interference-free spectrum sharing. The misdetection problem of a possible legitimate user occupies a desired frequency band leads to erroneous sensing results. Based on the periodicity revealing property of cepstral analysis approaches, we formulate a spectrum sensing technique based on the autocepstrum concept. We employ the proposed approach to detect a spread spectrum (SS) primary user (PU) signal. The blind theme of the proposed approach implies that no knowledge of the spreading code employed in a SS signal is provided at the CR receiver. The distribution of the detection test statistic is derived under the null hypothesis based on Neyman-Pearson lemma (NPL). The corresponding detection threshold is analytically computed. The performance of the proposed spectrum sensing algorithm is compared with conventional energy detection (CED) in terms of detection probability. As a result, the proposed detector outperforms CED, and indicates lower misdetection probability in low signal-to-noise (SNR) ratio environment.

HAL (Le Centre pour la Communication Scientifique Directe), Sep 11, 2007

La reconnaissance aveugle des paramètres d'une communication est une thématique importante dans l... more La reconnaissance aveugle des paramètres d'une communication est une thématique importante dans le contexte des récepteurs auto-configurants et de la guerreélectronique. Actuellement, peu de recherches se focalisent sur la reconnaissance aveugle du codage spatio-temporel utilisé dans les communications sans fil multi-émetteurs. Pour caractériser ces codages, nous proposons une nouvelle fonction de contraste basée sur des propriétés matricielles remarquables de statistiques d'ordre 2. L'utilisation de cette fonction de contraste en entrée d'un classifieur SVM permet la reconnaissance automatique du codage. Les performances de notre algorithme sontévaluées pour la reconnaissance de 3 types de codage (multiplexage spatial, codage d'Alamouti et codage OTSBC3 de rendement 1 2).

HAL (Le Centre pour la Communication Scientifique Directe), Mar 30, 2008

The issue addressed in this paper is the determination of the number of communication signals in ... more The issue addressed in this paper is the determination of the number of communication signals in a sensor array. Most of the available algorithms rely on the spatial uncorrelation of the additive noise. In practice, this condition is rarely satisfied when the receivers are not sufficiently spaced (MIMO communications for example). In this paper, we propose a new method to detect the number of communication signals based on the fact that the signals are independent and non gaussian and that the background noise is gaussian. By using an Independent Component Analysis in conjunction with Kolomogorov-Smirnov (K-S) tests, the method can detect as many communication signals as the number of receiver antennas. Simulations results show that our method performs well in many environments like those with spatially correlated noise.

HAL (Le Centre pour la Communication Scientifique Directe), Jun 1, 2008

International audienc

IEEE Transactions on Wireless Communications, Sep 1, 2008

The blind recognition of communication parameters is a key research issue for commercial and mili... more The blind recognition of communication parameters is a key research issue for commercial and military communication systems. The results of numerous investigations about symbol timing estimation, modulation recognition as well as identification of the number of transmitters have been reported in the literature. But, to our knowledge, none of them have dealt with the recognition of the Space-Time Block Codes (STBC) used in multiple transmitter communications. In order to blindly recognize the STBC of a wireless communication, this paper proposes a method based on the space-time correlations of the received signals. Under perfect timing synchronization and under ideal conditions (full rank channel and a number of receivers greater or equal to the number of transmitters), it shows that the Frobenius norms of these statistics present non-null values whose positions only depend on the STBC at the transmitter side. A classifier for the space-time code recognition of 5 linear STBC (Spatial Multiplexing, Alamouti Coding, and 3 Orthogonal STBC using 3 antennas) is presented. Simulations show that the proposed method performs well even at low signal-to-noise ratios.

HAL (Le Centre pour la Communication Scientifique Directe), Dec 12, 2016

The methods of dynamic access to spectrum developed in Cognitive Radio require efficient and robu... more The methods of dynamic access to spectrum developed in Cognitive Radio require efficient and robust spectrum detectors. Most of these detectors suffer from four main limits: the computational cost required for the detection procedure; the need of prior knowledge of Primary User's (PU) signal features; the poor performances obtained in low SNR (Signal to Noise Ratio) environment; finding an optimal detection threshold is a crucial issue. In this paper, we propose a blind detection method based on the cyclostationary features of communication signals to overcome the four limits of spectrum sensors. In order to reduce the computational cost, the FFT Accumulation Method has been adjusted to estimate the cyclic spectrum of the intercepted signal. Then, the spectrum coherence principle is used to catch the periodicity hidden in the cyclic autocorrelation function of this signal. The hidden periodicity is revealed by the crest factor of the cyclic domain profile. The detection of PU's signal is achieved by comparing the embedded periodicity level with a predetermined threshold related to the crest factor. This threshold varies randomly dependent on the SNR. Then, we have modelized the distribution law of the threshold in order to select the optimal value. Using the crest factor of the cyclic domain profile as a detection criterion has permitted to develop a spectrum sensor which is able to work in a blind context. Simulation results corroborate the efficiency and robustness of the proposed detector compared with the classical Energy Detector.

HAL (Le Centre pour la Communication Scientifique Directe), Mar 27, 2014

Spectrum Sensing is the main part in the Cognitive Radio system. In fact many researches have bee... more Spectrum Sensing is the main part in the Cognitive Radio system. In fact many researches have been realized the last decade, and several techniques have been proposed to perform the Spectrum Sensing. This manuscript deals with this subject by presenting the most used techniques, by categorizing them as Cooperative and Blind, according to their requirements.

The main aim of the Spectrum Sensing (SS) in a Cognitive Radio system is to distinguish between t... more The main aim of the Spectrum Sensing (SS) in a Cognitive Radio system is to distinguish between the binary hypotheses H0: Primary User (PU) is absent and H1: PU is active. In this paper, Machine Learning (ML)-based hybrid Spectrum Sensing (SS) scheme is proposed. The scattering of the Test Statistics (TSs) of two detectors is used in the learning and prediction phases. As the SS decision is binary, the proposed scheme requires the learning of only the boundaries of H0-class in order to make a decision on the PU status: active or idle. Thus, a set of data generated under H0 hypothesis is used to train the detection system. Accordingly, unlike the existing MLbased schemes of the literature, no PU statistical parameters are required. In order to discriminate between H0-class and elsewhere, we used a one-class classification approach that is inspired by the Isolation Forest algorithm. Extensive simulations are done in order to investigate the efficiency of such hybrid SS and the impact of the novelty detection model parameters on the detection performance. Indeed, these simulations corroborate the efficiency of the proposed one-class learning of the hybrid SS system.

Physical Communication, Jun 1, 2020

To enhance the error performance of impulse radio UWB transceivers, we introduce in this manuscri... more To enhance the error performance of impulse radio UWB transceivers, we introduce in this manuscript a novel modulation scheme based on exploiting the symmetry properties of transmitted waveforms. Parity Modulation utilizes odd versus even pulses to represent binary data, while the detector relies on a time reverser and non-coherent cross correlator. The analytical expression of power spectral density has been derived; then, considering different orders of Gaussian derivatives as pulse waveforms, the spectral characteristics have been optimized to comply with the UWB emission regulation. The bit error rate formula in an AWGN channel has been developed, while our simulation measurements showed a significant performance gain for 2 Gbps Parity over 1 Gbps Pulse Position Modulation and 2 Gbps On Off Keying. A reference-based parity scheme has been eventually proposed to enhance robustness against multi-path effects, interesting results have been achieved in terms of error probability in a realistic channel, with a compromise between data rate and complexity.

In this paper, we enhance the performance of Pulse Position Modulation scheme applied with Impuls... more In this paper, we enhance the performance of Pulse Position Modulation scheme applied with Impulse Radio Ultra WideBand transmission, while the receiver is based on non-coherent energy detection. By exploiting the time properties of Gaussian pulse derivatives, it was possible to adjust the modulation index in order to improve the data rate in compromise with the error probability. For the 5th Gaussian waveform, we succeeded in increasing the information rate by 25 % with a notable reduction in the bit error rate simultaneously. The transmission speed can be further boosted by 33 % at the cost of additional errors collected at receiver side, which depend on the signal-to-noise ratio and generated pulse dynamics.

In this paper, we present a new detector for cognitive radio system based on the Canonical Correl... more In this paper, we present a new detector for cognitive radio system based on the Canonical Correlation Significance Test (CCST). Unlike existing CCST approaches, which can only be applied on Multi-Antenna System (MAS), our algorithm can be extended for both Single Antenna System (SAS) and MAS. For SAS, the proposed algorithm exploits the time diversity of cyclostationary signals in order to detect the Primary User (PU) signal. Our simulation results shows that our algorithm outperforms well-known cyclostationary algorithm [9]. For MAS, our algorithm uses both spatial and time diversities to apply the CCST. Numerical results are given to illustrate the performance of our algorithm and verify its efficiency for special noise cases (spatially correlated and spatially colored). The simulation results show the superiority of the performance of the proposed detector compared to the recently CCST proposed algorithm [1].