Usman Muhammad - Academia.edu (original) (raw)
Papers by Usman Muhammad
2018 1st International Conference on Power, Energy and Smart Grid (ICPESG)
In this paper, we propose a new Demand Side Management (DSM) algorithm for multiple homes. For th... more In this paper, we propose a new Demand Side Management (DSM) algorithm for multiple homes. For this purpose, two type of loads are consider: discrete and continuous. The focus of this work is to minimize the energy consumption cost with new and old pricing scheme and reduce Peak to Average Ratio (PAR) to increase the efficiency of smart grid. In doing so, the load scheduling problem is mathematically formulated as a knapsack problem which later on solved by using the proposed heuristic based Genetic Algorithm (GA). For validation, the simulation results have conducted and compared against different cases: unscheduled vs. scheduled (Old pricing) and unscheduled vs. scheduled (New pricing). Simulation results show that the proposed strategy is efficiently able to handle different types of loads to reduce the daily electricity bill, while reducing the peak load demand as well.
Gut, May 19, 2016
Accurate optical characterisation and removal of small adenomas (<10 mm) at colonoscopy would ... more Accurate optical characterisation and removal of small adenomas (<10 mm) at colonoscopy would allow hyperplastic polyps to be left in situ and surveillance intervals to be determined without the need for histopathology. Although accurate in specialist practice the performance of narrow band imaging (NBI), colonoscopy in routine clinical practice is poorly understood. NBI-assisted optical diagnosis was compared with reference standard histopathological findings in a prospective, blinded study, which recruited adults undergoing routine colonoscopy in six general hospitals in the UK. Participating colonoscopists (N=28) were trained using the NBI International Colorectal Endoscopic (NICE) classification (relating to colour, vessel structure and surface pattern). By comparing the optical and histological findings in patients with only small polyps, test sensitivity was determined at the patient level using two thresholds: presence of adenoma and need for surveillance. Accuracy of iden...
2014 12th International Conference on Frontiers of Information Technology, 2014
Energy management is an acute challenge for battery powered devices. In this work, we consider a ... more Energy management is an acute challenge for battery powered devices. In this work, we consider a cognitive radio (CR) equipped with energy harvested finite capacity battery. The cognitive radio harvests energy from radio frequency (RF) source (primary channel) as well as from non-RF sources (ambient sources such as wind, solar, and vibration). Energy harvesting from the primary channel occurs only if the channel is found in busy state and energy of the signal is above a certain threshold. The harvested energy is consumed in channel sensing, processing and subsequent transmission. The spectrum sensing decision is controlled optimally by partially observable Markov decision process (POMDP) according to the available energy of the CR and status of the primary channel. Such decision results in an optimized utilization of energy. The cognitive radio enhances throughput by transmitting in the hybrid mode adapting the overlay or underlay mode depending on the sensing and transmission energy. Throughput improvement of the cognitive radio is shown through simulations where throughput in the hybrid mode is compared with the overlay-only mode. Simulations also show the effect of channel idle probability and harvested energy on the throughput.
Health Technology Assessment, 2015
BackgroundComputerised cognitive behaviour therapy (cCBT) has been developed as an efficient form... more BackgroundComputerised cognitive behaviour therapy (cCBT) has been developed as an efficient form of therapy delivery with the potential to enhance access to psychological care. Independent research is needed which examines both the clinical effectiveness and cost-effectiveness of cCBT over the short and longer term.ObjectivesTo compare the clinical effectiveness and cost-effectiveness of cCBT as an adjunct to usual general practitioner (GP) care against usual GP care alone, for a free-to-use cCBT program (MoodGYM; National Institute for Mental Health Research, Australian National University, Canberra, Australia) and a commercial pay-to-use cCBT program (Beating the Blues®; Ultrasis, London, UK) for adults with depression, and to determine the acceptability of cCBT and the experiences of users.DesignA pragmatic, multicentre, three-armed, parallel, randomised controlled trial (RCT) with concurrent economic and qualitative evaluations. Simple randomisation was used. Participants and r...
Japanese Journal of Applied Physics, 2014
High piezoelectric field in green light-emitting diodes (LEDs) has been a challenge for direct me... more High piezoelectric field in green light-emitting diodes (LEDs) has been a challenge for direct measurement for a long time. In this work, we report the direct experimental measurement of the large piezoelectric field in green LEDs by using single- and double-quantum-well samples with the electroreflectance spectroscopy at room temperature. Comparison with the theoretical prediction indicates that there is an influence of defects in reducing the piezoelectric field in green LED samples.
Science China Chemistry, 2014
ABSTRACT The present study reports a highly selective and stable catalytic approach for producing... more ABSTRACT The present study reports a highly selective and stable catalytic approach for producing tetralin, an important chemical, solvent, and H2 storage material. Transition metal phosphides (MoP, Ni2P, Co2P, and Fe2P) were prepared by wet impregnation and temperature-programmed reduction and characterized by x-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), EDX mapping, scanning electron microscopy (SEM), transmission electron microscopy (TEM), brunauer-emmett-teller (BET), temperature-programmed desorption of ammonia (NH3 -TPD), and fourier transform infrared spectroscopy of pyridine (pyri-dine-FTIR). Of all the transition metal phosphides MoP was formed at a lower reduction temperature, which resulted in small-er particle size that enhanced the overall surface area of the catalyst. The existence of weak, moderate, and Lewis acidic sites over MoP were responsible for its high tetralin selectivity (90%) and stability during the 100 h reaction on-stream in a fixed-bed reactor. coal tar, naphthalene, transition metal phosphides, selective hydrogenation, tetralin
Journal of Renewable and Sustainable Energy, 2013
In the perspective of fossil fuel depletion, the importance of renewable and substitute fuels is ... more In the perspective of fossil fuel depletion, the importance of renewable and substitute fuels is remarkable. In this study, clean liquid-fuel was obtained from tar through catalytic hydrorefining method. Hydrorefining catalysts were prepared by impregnation, containing tungsten-nickel (W-Ni), molybdenum-nickel (Mo-Ni), tungsten-molybdenum-nickel (W-Mo-Ni), and tungsten-molybdenum-cobalt (W-Mo-Co). c-alumina was used as catalysts supporter. The clean liquid fuel product was analyzed by Fourier transform infrared spectroscopy, gas chromatographymass spectrometry, elemental analyzer, octane number for gasoline fraction and cetane-number for diesel fraction, and Engler distillation range. The rules of sulfur and nitrogen content were also investigated. The overall product yield was up to 97%, and the sulfur and nitrogen content was less than 70 ppm. The W-Mo-Ni/c-Al 2 O 3 catalyst showed high performance in catalytic hydrofinishing and good stabilization under required conditions. V
American Journal of Plant Sciences, 2012
Sunflower (Helianthus annuus L.) has emerged as an economically important crop in Pakistan due to... more Sunflower (Helianthus annuus L.) has emerged as an economically important crop in Pakistan due to its significant share in vegetable oil production. The plant metabolic processes require protein to increase the vegetative, reproductive growth and yield of the crop. The protein is wholly dependent upon the amount of nitrogen fertilization available for plant use. A two-year field study was conducted in 2008 and 2009. The objective was to determine the effect of different nitrogen (N) levels (N 1 = 0 kg•ha-1 , N 2 = 60 kg•ha-1 , N 3 = 120 kg•ha-1 , N 4 = 180 kg•ha-1 and N 5 = 240 kg•ha-1) on three sunflower hybrids (Hysun-33, Hysun-38 and Poineer-64A93) in agro-climatic conditions of Gujranwala, a sub-humid region in the centre of the Punjab province of Pakistan. A randomized complete block design split plot experiment was setup with cultivars in the main plots and N levels in the subplots. Results showed that Hysun-38 gave maximum TDM (15815 kg•ha-1) and maximum grain yield (3389 kg•ha-1), while minimum TDM (14640 kg•ha-1) and grain yield (3125 kg•ha-1) was observed in Hysun-33. Among different N rates evaluated, N 4 gave maximum TDM (17890 kg•ha-1) and grain yield (3809 kg•ha-1) compared to the other N rates. The maximum oil content (46.2%) was observed in Hysun-38 without application of N fertilizer (N 1), while the minimum oil content (40.6%) was observed from N 5 treatment. In conclusion, the application of 180 kg•ha-1 N to Hysun-38 provided the best combination for good yield in sunflower crop under the prevailing sub-humid conditions of Pakistan.
IEEE Sensors Journal, 2014
ABSTRACT In this paper, we consider a hybrid underlay-overlay cognitive radio with energy harvest... more ABSTRACT In this paper, we consider a hybrid underlay-overlay cognitive radio with energy harvesting. In the considered system, secondary user can harvest energy from the primary user’s signal as well as from the other ambient sources, such as solar, wind, vibration and so on. Energy is harvested from the primary user’s signal when the primary channel is found in busy state. The secondary user either operates in one of the two transmission modes; overlay and underlay in order to maximize the throughput, remains in the sleep mode in order to conserve energy, or harvests energy from the primary channel in order to maximize the remaining energy. To maximize long-term throughput of the system, we propose an access strategy in which the partially observable Markov decision process framework is used to determine action of the secondary user, and energy threshold is used to determine the transmission mode (overlay or underlay) of secondary user. Simulations show that for certain values of the system parameters, the considered system provides 60% improved throughput than overlay-only cognitive radio and 43% enhanced throughput than a hybrid cognitive radio system harvesting energy only from the ambient sources. However, increasing the throughput also increases computational burden on the secondary user, which may increase latency and energy requirements of the system.
ABSTRACT In this paper, uncertainty in the spectrum sensing arising from channel destructive effe... more ABSTRACT In this paper, uncertainty in the spectrum sensing arising from channel destructive effects such as shadowing and fading, is controlled by proposing a non-uniform reliability based cooperative spectrum sensing (CSS) technique. Channel conditions are quantified into non-uniform reliabilities which are assigned to users based on their congruence with the global observation. An identification tag (IT), assigned on the bases of correlation between secondary user’s local observation and the primary signal status, is used to detect malicious users (MU). In the proposed scheme, unreliable as well as malicious users (always busy, always free, and always opposite) are discarded from the network leading to improved inference accuracy. Simulation results show the advantage of our proposed scheme over the conventional CSS.
ABSTRACT In this paper, uncertainty in the spectrum sensing arising from channel destructive effe... more ABSTRACT In this paper, uncertainty in the spectrum sensing arising from channel destructive effects such as shadowing and fading, is controlled by proposing a non-uniform reliability based cooperative spectrum sensing (CSS) technique. Channel conditions are quantified into non-uniform reliabilities, which are assigned to users as their identification tags (IT), and are used by the fusion center to exclude the unreliable users from the global decision. IT is used to detect malicious users (MU). Two strategies have been proposed in this work to discard the unreliable as well as malicious users (of type always opposite and always busy) from the network which leads to improved inference accuracy. The simulation results show the effectiveness of our proposed strategies where our proposed strategies demonstrates better detection performance and consider fewer users than the conventional CSS and Chair-Varshney optimum rule, in the presence of malicious users.
IEEE Sensors Journal, 2014
ABSTRACT String matching algorithms used in bioinformatics can be applied to scenarios in cogniti... more ABSTRACT String matching algorithms used in bioinformatics can be applied to scenarios in cognitive radios where reports of cooperative spectrum sensing nodes need to be compared with each other. Cooperative spectrum sensing is susceptible to security risks where malicious users who participate in the process falsify the spectrum sensing data, thus affecting cognitive radio network performance. In this work, an efficient spectrum sensing system is developed where each cognitive radio (CR) user senses the spectrum multiple times within an allocated sensing period. Each CR user quantizes its decision to predefined levels so as to achieve a trade-off between bandwidth utilization and decision reporting accuracy. The reports for all the CR users are compared at the fusion center using Smith-Waterman algorithm (SWA), an optimal algorithm for aligning biological sequences used in bioinformatics, and similarity indices are computed. Robust mean and robust deviation of the similarity indices are calculated and a threshold is determined by these values. The CR users who have similarity indices below the given threshold are declared malicious and their reports are discarded. The local decisions of the remaining CR users are combined using the modified rules of decision combination to take a global decision. Simulation results show that our proposed scheme performs better than conventional schemes with and without malicious users.
Routledge International Studies in Money and Banking, 2003
Islamic economics is a comprehensive and independent economic theory which defines economic princ... more Islamic economics is a comprehensive and independent economic theory which defines economic principles in accordance with Islamic law and taking into account, all aspects of human life: the spiritual, material, social and political aspects et cetera. Just like many other economic systems, the Shari'ah aspires to attain economic ideals such as efficient and equitable use of resources, full employment and satisfaction of basic human needs such as food, shelter and clothing. However, it differs fundamentally from man-made laws in defining the economic problem by adding a moral and religious dimension as part and parcel of the problem. In fact, whereas, the conventional economic systems are based on principles such as scarcity, self-interest, opportunity, cost-benefit and free functioning, Islam on the contrary allows human beings to exploit the world's resources to the best of their ability in a spirit of justice and brotherhood towards human beings and putting in consideration that profit should not be earned to the detriment of the environment. All these are addressed in the different topics of this book .
Lecture Notes in Computer Science, 2008
This paper presents vision based self-localization of tiny autonomous mobile robots in a known bu... more This paper presents vision based self-localization of tiny autonomous mobile robots in a known but highly dynamic environment. The problem covers tracking the robot position with an initial estimate to global self-localization. The algorithm enables the robot to find its initial position and to verify its location during every movement. The global position of the robot is estimated using trilateration based techniques whenever distinct landmark features are extracted. Distance measurements are used as they require fewer landmarks compared to methods using angle measurements. However, the minimum required features for global position estimation are not available through the entire state space. Therefore, the robot position is tracked once a global position estimate is available. Extended Kalman filter is used to fuse information from multiple heterogeneous sensors. Simulation results show that the new method that combines the global position estimation with tracking results in significant performance gain.
2013 IEEE 24th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), 2013
ABSTRACT Network simulators have gained an increased importance in the research community to an e... more ABSTRACT Network simulators have gained an increased importance in the research community to an extent that approximately 11% of the research papers that appeared in the proceedings of leading international conferences used network simulators to test their claims. It is anticipated that due to the several advantages network simulators will become more prevalent in the research community in future. However, with the growing popularity of the network simulators, challenges in the form of consistent revelations about their inaccuracies have started to seriously question the use of such simulators and simulation based research. This paper attempts to answer the questions (1) How can assumptions/simplifications in modeling affect realism of simulations? (2) How credibility of simulation based research be improved?, and (3) What necessary steps must be taken to make network simulators credible? The paper provides deliberated recommendations for improving the authenticity of simulation based experiments. The authors believe that the discussion in this paper will greatly facilitate the repeatability of simulation based research and will help researchers to select the most suitable (credible) simulator.
2018 1st International Conference on Power, Energy and Smart Grid (ICPESG)
In this paper, we propose a new Demand Side Management (DSM) algorithm for multiple homes. For th... more In this paper, we propose a new Demand Side Management (DSM) algorithm for multiple homes. For this purpose, two type of loads are consider: discrete and continuous. The focus of this work is to minimize the energy consumption cost with new and old pricing scheme and reduce Peak to Average Ratio (PAR) to increase the efficiency of smart grid. In doing so, the load scheduling problem is mathematically formulated as a knapsack problem which later on solved by using the proposed heuristic based Genetic Algorithm (GA). For validation, the simulation results have conducted and compared against different cases: unscheduled vs. scheduled (Old pricing) and unscheduled vs. scheduled (New pricing). Simulation results show that the proposed strategy is efficiently able to handle different types of loads to reduce the daily electricity bill, while reducing the peak load demand as well.
Gut, May 19, 2016
Accurate optical characterisation and removal of small adenomas (<10 mm) at colonoscopy would ... more Accurate optical characterisation and removal of small adenomas (<10 mm) at colonoscopy would allow hyperplastic polyps to be left in situ and surveillance intervals to be determined without the need for histopathology. Although accurate in specialist practice the performance of narrow band imaging (NBI), colonoscopy in routine clinical practice is poorly understood. NBI-assisted optical diagnosis was compared with reference standard histopathological findings in a prospective, blinded study, which recruited adults undergoing routine colonoscopy in six general hospitals in the UK. Participating colonoscopists (N=28) were trained using the NBI International Colorectal Endoscopic (NICE) classification (relating to colour, vessel structure and surface pattern). By comparing the optical and histological findings in patients with only small polyps, test sensitivity was determined at the patient level using two thresholds: presence of adenoma and need for surveillance. Accuracy of iden...
2014 12th International Conference on Frontiers of Information Technology, 2014
Energy management is an acute challenge for battery powered devices. In this work, we consider a ... more Energy management is an acute challenge for battery powered devices. In this work, we consider a cognitive radio (CR) equipped with energy harvested finite capacity battery. The cognitive radio harvests energy from radio frequency (RF) source (primary channel) as well as from non-RF sources (ambient sources such as wind, solar, and vibration). Energy harvesting from the primary channel occurs only if the channel is found in busy state and energy of the signal is above a certain threshold. The harvested energy is consumed in channel sensing, processing and subsequent transmission. The spectrum sensing decision is controlled optimally by partially observable Markov decision process (POMDP) according to the available energy of the CR and status of the primary channel. Such decision results in an optimized utilization of energy. The cognitive radio enhances throughput by transmitting in the hybrid mode adapting the overlay or underlay mode depending on the sensing and transmission energy. Throughput improvement of the cognitive radio is shown through simulations where throughput in the hybrid mode is compared with the overlay-only mode. Simulations also show the effect of channel idle probability and harvested energy on the throughput.
Health Technology Assessment, 2015
BackgroundComputerised cognitive behaviour therapy (cCBT) has been developed as an efficient form... more BackgroundComputerised cognitive behaviour therapy (cCBT) has been developed as an efficient form of therapy delivery with the potential to enhance access to psychological care. Independent research is needed which examines both the clinical effectiveness and cost-effectiveness of cCBT over the short and longer term.ObjectivesTo compare the clinical effectiveness and cost-effectiveness of cCBT as an adjunct to usual general practitioner (GP) care against usual GP care alone, for a free-to-use cCBT program (MoodGYM; National Institute for Mental Health Research, Australian National University, Canberra, Australia) and a commercial pay-to-use cCBT program (Beating the Blues®; Ultrasis, London, UK) for adults with depression, and to determine the acceptability of cCBT and the experiences of users.DesignA pragmatic, multicentre, three-armed, parallel, randomised controlled trial (RCT) with concurrent economic and qualitative evaluations. Simple randomisation was used. Participants and r...
Japanese Journal of Applied Physics, 2014
High piezoelectric field in green light-emitting diodes (LEDs) has been a challenge for direct me... more High piezoelectric field in green light-emitting diodes (LEDs) has been a challenge for direct measurement for a long time. In this work, we report the direct experimental measurement of the large piezoelectric field in green LEDs by using single- and double-quantum-well samples with the electroreflectance spectroscopy at room temperature. Comparison with the theoretical prediction indicates that there is an influence of defects in reducing the piezoelectric field in green LED samples.
Science China Chemistry, 2014
ABSTRACT The present study reports a highly selective and stable catalytic approach for producing... more ABSTRACT The present study reports a highly selective and stable catalytic approach for producing tetralin, an important chemical, solvent, and H2 storage material. Transition metal phosphides (MoP, Ni2P, Co2P, and Fe2P) were prepared by wet impregnation and temperature-programmed reduction and characterized by x-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), EDX mapping, scanning electron microscopy (SEM), transmission electron microscopy (TEM), brunauer-emmett-teller (BET), temperature-programmed desorption of ammonia (NH3 -TPD), and fourier transform infrared spectroscopy of pyridine (pyri-dine-FTIR). Of all the transition metal phosphides MoP was formed at a lower reduction temperature, which resulted in small-er particle size that enhanced the overall surface area of the catalyst. The existence of weak, moderate, and Lewis acidic sites over MoP were responsible for its high tetralin selectivity (90%) and stability during the 100 h reaction on-stream in a fixed-bed reactor. coal tar, naphthalene, transition metal phosphides, selective hydrogenation, tetralin
Journal of Renewable and Sustainable Energy, 2013
In the perspective of fossil fuel depletion, the importance of renewable and substitute fuels is ... more In the perspective of fossil fuel depletion, the importance of renewable and substitute fuels is remarkable. In this study, clean liquid-fuel was obtained from tar through catalytic hydrorefining method. Hydrorefining catalysts were prepared by impregnation, containing tungsten-nickel (W-Ni), molybdenum-nickel (Mo-Ni), tungsten-molybdenum-nickel (W-Mo-Ni), and tungsten-molybdenum-cobalt (W-Mo-Co). c-alumina was used as catalysts supporter. The clean liquid fuel product was analyzed by Fourier transform infrared spectroscopy, gas chromatographymass spectrometry, elemental analyzer, octane number for gasoline fraction and cetane-number for diesel fraction, and Engler distillation range. The rules of sulfur and nitrogen content were also investigated. The overall product yield was up to 97%, and the sulfur and nitrogen content was less than 70 ppm. The W-Mo-Ni/c-Al 2 O 3 catalyst showed high performance in catalytic hydrofinishing and good stabilization under required conditions. V
American Journal of Plant Sciences, 2012
Sunflower (Helianthus annuus L.) has emerged as an economically important crop in Pakistan due to... more Sunflower (Helianthus annuus L.) has emerged as an economically important crop in Pakistan due to its significant share in vegetable oil production. The plant metabolic processes require protein to increase the vegetative, reproductive growth and yield of the crop. The protein is wholly dependent upon the amount of nitrogen fertilization available for plant use. A two-year field study was conducted in 2008 and 2009. The objective was to determine the effect of different nitrogen (N) levels (N 1 = 0 kg•ha-1 , N 2 = 60 kg•ha-1 , N 3 = 120 kg•ha-1 , N 4 = 180 kg•ha-1 and N 5 = 240 kg•ha-1) on three sunflower hybrids (Hysun-33, Hysun-38 and Poineer-64A93) in agro-climatic conditions of Gujranwala, a sub-humid region in the centre of the Punjab province of Pakistan. A randomized complete block design split plot experiment was setup with cultivars in the main plots and N levels in the subplots. Results showed that Hysun-38 gave maximum TDM (15815 kg•ha-1) and maximum grain yield (3389 kg•ha-1), while minimum TDM (14640 kg•ha-1) and grain yield (3125 kg•ha-1) was observed in Hysun-33. Among different N rates evaluated, N 4 gave maximum TDM (17890 kg•ha-1) and grain yield (3809 kg•ha-1) compared to the other N rates. The maximum oil content (46.2%) was observed in Hysun-38 without application of N fertilizer (N 1), while the minimum oil content (40.6%) was observed from N 5 treatment. In conclusion, the application of 180 kg•ha-1 N to Hysun-38 provided the best combination for good yield in sunflower crop under the prevailing sub-humid conditions of Pakistan.
IEEE Sensors Journal, 2014
ABSTRACT In this paper, we consider a hybrid underlay-overlay cognitive radio with energy harvest... more ABSTRACT In this paper, we consider a hybrid underlay-overlay cognitive radio with energy harvesting. In the considered system, secondary user can harvest energy from the primary user’s signal as well as from the other ambient sources, such as solar, wind, vibration and so on. Energy is harvested from the primary user’s signal when the primary channel is found in busy state. The secondary user either operates in one of the two transmission modes; overlay and underlay in order to maximize the throughput, remains in the sleep mode in order to conserve energy, or harvests energy from the primary channel in order to maximize the remaining energy. To maximize long-term throughput of the system, we propose an access strategy in which the partially observable Markov decision process framework is used to determine action of the secondary user, and energy threshold is used to determine the transmission mode (overlay or underlay) of secondary user. Simulations show that for certain values of the system parameters, the considered system provides 60% improved throughput than overlay-only cognitive radio and 43% enhanced throughput than a hybrid cognitive radio system harvesting energy only from the ambient sources. However, increasing the throughput also increases computational burden on the secondary user, which may increase latency and energy requirements of the system.
ABSTRACT In this paper, uncertainty in the spectrum sensing arising from channel destructive effe... more ABSTRACT In this paper, uncertainty in the spectrum sensing arising from channel destructive effects such as shadowing and fading, is controlled by proposing a non-uniform reliability based cooperative spectrum sensing (CSS) technique. Channel conditions are quantified into non-uniform reliabilities which are assigned to users based on their congruence with the global observation. An identification tag (IT), assigned on the bases of correlation between secondary user’s local observation and the primary signal status, is used to detect malicious users (MU). In the proposed scheme, unreliable as well as malicious users (always busy, always free, and always opposite) are discarded from the network leading to improved inference accuracy. Simulation results show the advantage of our proposed scheme over the conventional CSS.
ABSTRACT In this paper, uncertainty in the spectrum sensing arising from channel destructive effe... more ABSTRACT In this paper, uncertainty in the spectrum sensing arising from channel destructive effects such as shadowing and fading, is controlled by proposing a non-uniform reliability based cooperative spectrum sensing (CSS) technique. Channel conditions are quantified into non-uniform reliabilities, which are assigned to users as their identification tags (IT), and are used by the fusion center to exclude the unreliable users from the global decision. IT is used to detect malicious users (MU). Two strategies have been proposed in this work to discard the unreliable as well as malicious users (of type always opposite and always busy) from the network which leads to improved inference accuracy. The simulation results show the effectiveness of our proposed strategies where our proposed strategies demonstrates better detection performance and consider fewer users than the conventional CSS and Chair-Varshney optimum rule, in the presence of malicious users.
IEEE Sensors Journal, 2014
ABSTRACT String matching algorithms used in bioinformatics can be applied to scenarios in cogniti... more ABSTRACT String matching algorithms used in bioinformatics can be applied to scenarios in cognitive radios where reports of cooperative spectrum sensing nodes need to be compared with each other. Cooperative spectrum sensing is susceptible to security risks where malicious users who participate in the process falsify the spectrum sensing data, thus affecting cognitive radio network performance. In this work, an efficient spectrum sensing system is developed where each cognitive radio (CR) user senses the spectrum multiple times within an allocated sensing period. Each CR user quantizes its decision to predefined levels so as to achieve a trade-off between bandwidth utilization and decision reporting accuracy. The reports for all the CR users are compared at the fusion center using Smith-Waterman algorithm (SWA), an optimal algorithm for aligning biological sequences used in bioinformatics, and similarity indices are computed. Robust mean and robust deviation of the similarity indices are calculated and a threshold is determined by these values. The CR users who have similarity indices below the given threshold are declared malicious and their reports are discarded. The local decisions of the remaining CR users are combined using the modified rules of decision combination to take a global decision. Simulation results show that our proposed scheme performs better than conventional schemes with and without malicious users.
Routledge International Studies in Money and Banking, 2003
Islamic economics is a comprehensive and independent economic theory which defines economic princ... more Islamic economics is a comprehensive and independent economic theory which defines economic principles in accordance with Islamic law and taking into account, all aspects of human life: the spiritual, material, social and political aspects et cetera. Just like many other economic systems, the Shari'ah aspires to attain economic ideals such as efficient and equitable use of resources, full employment and satisfaction of basic human needs such as food, shelter and clothing. However, it differs fundamentally from man-made laws in defining the economic problem by adding a moral and religious dimension as part and parcel of the problem. In fact, whereas, the conventional economic systems are based on principles such as scarcity, self-interest, opportunity, cost-benefit and free functioning, Islam on the contrary allows human beings to exploit the world's resources to the best of their ability in a spirit of justice and brotherhood towards human beings and putting in consideration that profit should not be earned to the detriment of the environment. All these are addressed in the different topics of this book .
Lecture Notes in Computer Science, 2008
This paper presents vision based self-localization of tiny autonomous mobile robots in a known bu... more This paper presents vision based self-localization of tiny autonomous mobile robots in a known but highly dynamic environment. The problem covers tracking the robot position with an initial estimate to global self-localization. The algorithm enables the robot to find its initial position and to verify its location during every movement. The global position of the robot is estimated using trilateration based techniques whenever distinct landmark features are extracted. Distance measurements are used as they require fewer landmarks compared to methods using angle measurements. However, the minimum required features for global position estimation are not available through the entire state space. Therefore, the robot position is tracked once a global position estimate is available. Extended Kalman filter is used to fuse information from multiple heterogeneous sensors. Simulation results show that the new method that combines the global position estimation with tracking results in significant performance gain.
2013 IEEE 24th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), 2013
ABSTRACT Network simulators have gained an increased importance in the research community to an e... more ABSTRACT Network simulators have gained an increased importance in the research community to an extent that approximately 11% of the research papers that appeared in the proceedings of leading international conferences used network simulators to test their claims. It is anticipated that due to the several advantages network simulators will become more prevalent in the research community in future. However, with the growing popularity of the network simulators, challenges in the form of consistent revelations about their inaccuracies have started to seriously question the use of such simulators and simulation based research. This paper attempts to answer the questions (1) How can assumptions/simplifications in modeling affect realism of simulations? (2) How credibility of simulation based research be improved?, and (3) What necessary steps must be taken to make network simulators credible? The paper provides deliberated recommendations for improving the authenticity of simulation based experiments. The authors believe that the discussion in this paper will greatly facilitate the repeatability of simulation based research and will help researchers to select the most suitable (credible) simulator.