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Ahmed, M. Ejaz,Ju Bin Song,Zhu Han,Doug Young Suh IEEE 2014 IEEE TRANSACTIONS ON MOBILE COMPUTING Vol.13 No.9
<P>In cognitive radio networks, the main objective of spectrum sensing is to exploit spectrum holes left by the primary users (PUs). Different PUs' traffic patterns might provide different opportunities for second user (SU) spectrum access. In this paper, we identify the PUs' traffic patterns and then maximize SU transmission accordingly. First a theoretical framework is developed to cluster PU traffic patterns based on a Bayesian nonparametric inference model, in which the number of traffic types is unknown. Second, in order to exploit the spectrum holes, we study a sensing-transmission structure to optimize the SU transmission strategy. Specifically, we exploit the short and long transmission opportunities based on the PU traffic pattern and channel idle time distribution. Finally, we propose a threshold-based sensing-transmission method that optimizes the SU utility, while protecting PU transmissions. Both sensing and transmission errors are considered for perfect sensing with/without acknowledgement-based transmission and imperfect sensing, respectively. From the simulation results, we show that the proposed technique outperforms the nonparametric mean shift clustering algorithm. Furthermore, we utilize these clustering results to optimize the SU's transmission strategy with perfect and imperfect sensing. We compare our proposed technique with the probabilistic sensing-transmission structure and show the performance gain in terms of throughput.</P>
Energy-Arrival-Aware Detection Threshold in Wireless-Powered Cognitive Radio Networks
Ahmed, Muhammad Ejaz,Kim, Dong In,Kim, Jin Young,Shin, Yoan IEEE 2017 IEEE Transactions on Vehicular Technology VT Vol.66 No.10
<P>Traffic patterns associated with different primary user (PU) channels may provide different spectral access and energy harvesting opportunities in wireless-powered cognitive radio networks (WP-CRNs). Considering this, we propose traffic-specific optimal spectrum sensing policy such that the expected transmission rate of secondary user (SU) is maximized under the energy causality and PU collision constraints in orthogonal frequency-division multiple access (OFDMA)-based WP-CRN. Toward this, we cluster N subcarriers (subchannels) into K clusters (where K = N) and derive an optimal energy detection threshold for the SU under each traffic pattern. Using traffic features, we propose an unsupervised and nonparametric classification technique to determine the number of unique traffic patternsK over all subchannels. Then, the traffic patterns are used to predict the idle/busy period statistics for subchannels, based upon which SU identifies harvest and transmit PU subchannels for energy harvesting and data transmission, respectively. We derive an optimal detection threshold based on the harvested energy such that it maximizes the expected transmission rate of SU while protecting PU from collision. We demonstrate the effectiveness of the proposed scheme in terms of rate gains under design constraints and show the optimal detection threshold under various energy arrival rates.</P>
Antioxidant Activity with Flavonoidal Constituents from Aerva persica
Ejaz Ahmed,Muhammad Imran,Abdul Malik,Muhammad Ashraf 대한약학회 2006 Archives of Pharmacal Research Vol.29 No.5
A new flavanone Persinol (1) and the new flavanone glucosides persinosides A (2) and B (3), along with known flavonoids (4 and 5) have been isolated from the ethyl acetate soluble fraction of the whole plants of Aerva persica. Their structures were elucidated on the basis of extensive analysis of nuclear magnetic resonance (1D & 2D-NMR) spectral data. All of them showed profound antioxidative activities by DPPH and cytochrome-c-reduction assays using the HL-60 cell culture system.
Traffic-Aware Optimal Spectral Access in Wireless Powered Cognitive Radio Networks
Ahmed, Muhammad Ejaz,Kim, Dong In,Choi, Kae Won IEEE Computer Society 2018 IEEE TRANSACTIONS ON MOBILE COMPUTING Vol.17 No.3
<P>Traffic patterns associated with different primary users (PUs) might provide different spectral access and energy harvesting opportunities to secondary users (SUs) in wireless powered cognitive radio networks (WP-CRNs). Since the traffic applications have their own distinctive patterns, spectral access and energy harvesting opportunities are also expected to be distinctive. In this paper, we propose a novel approach to identify the PU traffic patterns and estimate the energy harvested from each traffic pattern so that SU can maximize its capacity accordingly. More specifically, we propose a theoretical framework based on a variational inference algorithm to cluster various traffic patterns and design a threshold-based SU transmission strategy by taking into account the spectral access and energy harvesting opportunities for each traffic pattern, so as to optimize SU transmission. Through simulations, we demonstrate the effectiveness of the proposed scheme in terms of throughput gains and show the transmission thresholds under various traffic applications (patterns). Further, we illustrate the effects of different collision costs on throughput for different traffic applications using real wireless traces.</P>
Antioxidant Activity with Flavonoidal Constituents from Aerva persica
Ahmed Ejaz,Imran Muhammad,Malik Abdul,Ashraf Muhammad The Pharmaceutical Society of Korea 2006 Archives of Pharmacal Research Vol.29 No.5
A new flavanone Persinol (1) and the new flavanone glucosides persinosides A (2) and B (3), along with known flavonoids (4 and 5) have been isolated from the ethyl acetate soluble fraction of the whole plants of Aerva persica. Their structures were elucidated on the basis of extensive analysis of nuclear magnetic resonance (1D & 2D-NMR) spectral data. All of them showed profound antioxidative activities by DPPH and cytochrome-c-reduction assays using the HL-60 cell culture system.
Distributed Channel Allocation Using Kernel Density Estimation in Cognitive Radio Networks
M. Ejaz Ahmed,김주석,Runkun Mao,송주빈,Husheng Li 한국전자통신연구원 2012 ETRI Journal Vol.34 No.5
Typical channel allocation algorithms for secondary users do not include processes to reduce the frequency of switching from one channel to another caused by random interruptions by primary users, which results in high packet drops and delays. In this letter, with the purpose of decreasing the number of switches made between channels, we propose a nonparametric channel allocation algorithm that uses robust kernel density estimation to effectively schedule idle channel resources. Experiment and simulation results demonstrate that the proposed algorithm outperforms both random and parametric channel allocation algorithms in terms of throughput and packet drops.
Graph Compression by Identifying Recurring Subgraphs
무하메드이자즈아메드 ( Muhammad Ejaz Ahmed ),이정훈 ( Jeonghoon Lee ),나인혁 ( Inhyuk Na ),손샘 ( Sam Son ),한욱신 ( Wook-shin Han ) 한국정보처리학회 2017 한국정보처리학회 학술대회논문집 Vol.24 No.1
Current graph mining algorithms suffers from performance issues when querying patterns are in increasingly massive network graphs. However, from our observation most data graphs inherently contains recurring se mantic subgraphs/substructures. Most graph mining algorithms treat them as independent subgraphs and perform computations on them redundantly, which result in performance degradation when processing massive graphs. In this paper, we propose an algorithm which exploits these inherent recurring subgraphs/substructures to reduce graph sizes so that redundant computations performed by the traditional graph mining algorithms are reduced. Experimental results show that our graph compression approach achieve up to 69% reduction in graph sizes over the real datasets. Moreover, required time to construct the compressed graphs is also reasonably reduced.
Lipoxygenase Inhibitory Constituents from Indigofera oblongifolia
Sharif, Ahsan,Ahmed, Ejaz,Malik, Abdul,Riaz, Naheed,Afza, Nighat,Nawaz, Sarfraz Ahmad,Arshad, Muhammad,Shah, Muhammad Raza,Chaudhary, Muhammad Iqbal The Pharmaceutical Society of Korea 2005 Archives of Pharmacal Research Vol.28 No.7
Indigin, alkylated xanthene (1) and indigoferic acid (2) have been isolated from the chloroform soluble fraction of Indigofera oblongifolia, along with $\beta$-sitosterol (3) and 3-hydroxybenzoic acid (4), which are reported for the first time from this species. Their structures were determined through spectroscopic techniques. Both the new compounds 1 and 2 showed significant activity against enzyme lipoxygenase, while 2 further showed moderate inhibition against BChE.