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Search Results: 1 - 10 of 3470 matches for " spectrum "
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Performance Evaluation of Spectrum Detection in Cognitive Radio Network  [PDF]
Shubhangi Mahamuni, Vivekanand Mishra
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2014, DOI: 10.4236/ijcns.2014.711049
Abstract: In mobility management, detection of spectrum hole plays very important role for doing spectrum handoff mechanism. Operation of the cognitive radio depends on the spectrum sensing which is the most important task in case of cognitive radio network. Detection of spectrum holes (underutilized sub-bands of the radio spectrum) estimates average power, throughput and utilized time for each spectrum hole. But in case of reactive spectrum handoff mechanism, spectrum handoff delay becomes tedious task. So in order to make spectrum handoff mechanism efficient our scheme proposed spectrum handoff mechanism with negligible spectrum handoff delay. In this paper we had real time experimental setup with the spectrum handoff mechanism. We investigate algorithm for spectrum handoff mechanism which strongly minimizes spectrum handoff delay of cognitive radio network using spectrum detection method for sensing spectrum holes.
Detection Proposal Schemes for Spectrum Sensing in Cognitive Radio  [PDF]
Nawaf Hadhal Kamil, Xiuhua Yuan
Wireless Sensor Network (WSN) , 2010, DOI: 10.4236/wsn.2010.24048
Abstract: The most important components of the cognitive radio concept is its ability to measure, sense and learn. One also should be aware of the parameters related to the radio channel characteristics and the availability of spectrum and power. In cognitive radio technology, primary users can be defined as the users who have the highest priority on the usage of a specific part of the spectrum. Secondary users, have lower priority, and should not cause any interference to the primary users when using the technology. Therefore, the secondary users need to have certain cognitive radio capabilities, such as sensing the spectrum to check whether it is being used by primary user or not, and changing the radio parameters to exploit the unused part of the spectrum. In this paper we proposed a new approach for spectrum sensing, In the first approach the primary signal is known so we use the code value with match filter to detect the primary user, on the other hand, when the primary user signal is unknown we proposed a new strategy for energy detection in both non-cooperation and cooperation schemes. Then we will prove by simulation results that the new approach is better than the conventional energy detection.
PV Characterization System Outdoors—Case Study in Brazil  [PDF]
Pedro Rodrigues Silva, Patrícia Romeiro da Silva Jota, Ana Paula Batista
Journal of Power and Energy Engineering (JPEE) , 2017, DOI: 10.4236/jpee.2017.512014
Abstract: Photovoltaic modules (PV) are tested in the industry in standard conditions and their characteristics are given in the datasheet. After installation on the site, its performance is not evaluated separately of the other parts of the PV generator. Nevertheless some discrepancies of the expected generation and the measured ones are verified. To deal with these discrepancies it is worth characterizing the module on the site and acquire data in an easy and inexpensive way. This paper presents a proposed characterization system as well as its application. A module test was performed on a site located in Brazil. At these latitudes it is common to have high amount of ultraviolet components. The characterization system measures separately the ultraviolet component, as well as the visible and global irradiations. The results obtained are analyzed and the effect of the UV variation is observed, proving the importance of doing this characterization on site after implementation of the PV system.
A Novel Cooperative Spectrum Sharing Algorithm Based on Optimal Cognitive Radio User Selection  [PDF]
Mohammad Bigdeli, Bahman Abolhassani
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2012, DOI: 10.4236/ijcns.2012.51002
Abstract: In this paper, we consider the problem of cognitive radio (CR) user selection to maximize overall CR network (CRN) throughput when the available spectrum bandwidth is less than the demand by all CR users. We formulate optimal CR user selection problem. Then, based on approximation of the average received signal to interference plus noise ratio (SINR) and adaptive modulation and coding (AMC), we estimate the required bandwidth of CR users with different required quality of services (QoSs). Using the principle of optimality, we propose a novel cooperative spectrum sharing algorithm for a CRN. The proposed algorithm not only achieves exhaustive search performance but also its complexity is in the order of N × M versus 2N for exhaustive search, where N is the number of CR users, and M is the spectrum pool size. Extensive simulation results illustrate that the proposed algorithm significantly outperforms the existing algorithms that ignore optimal CR user selection. Also, these results illustrate a better fairness criterion than those of previous works.
Mixed Contiguous and Aggregated Spectrum Allocation Algorithm for CR based TD-LTE System  [PDF]
Xiaoyan Liu, Qingyi Quan, Peng Lei, Wenbin Guo, Wenbo Wang
Communications and Network (CN) , 2013, DOI: 10.4236/cn.2013.53B2055
Abstract: Cognitive Radio (CR) is a promising technology to increase the efficiency of spectrum by opportunistic access. However, in many cases the sensed spectrum is so broken that it cannot be utilized sufficiently with traditional continuous spectrum allocation strategy. Spectrum aggregation can make full use of narrow spectrum fragments while the overhead it brings may reduce the overall performance of the system. This paper proposes a Mixed Contiguous and Aggregated Spectrum Allocation (MixCASA) algorithm for CR based TD-LTE Networks. This algorithm combines contiguous with discontiguous spectrum allocation together in order to guarantee the feasibility and efficiency of system. Simulation results show that the MixCASA algorithm can increase the number of allocated channels, and reduce the overhead brought by excessive spectrum aggregation as well.
Spectroscopic Phenomenological Estimation of the Functional State of the Human Organism in Rate and Pathology  [PDF]
Michail Yurevich Dolomatov, Nikolay Vasilevich Kalashchenko, Sergei Vladislavovich Dezortsev, Timur Ramilevich Araslanov
International Journal of Clinical Medicine (IJCM) , 2011, DOI: 10.4236/ijcm.2011.22015
Abstract: Express-evaluation of functional state of organism is the urgent question in connection with extension of the number of facts, affecting people in conditions of environment. Considering the variety of different effects, preferences might be given to integral activities. To our opinion, that kind of evaluation may be given by the phenomenological absorption spectroscopy analysis of biological liquids, which regards blood and its components as one and indivisible light-absorbing system without separating into individual compounds. We determine blood and its components as a system of quasi-particles in excited state. This way, all of physicochemical properties of such kind of system are formed by its effective energy characteristics, connected with absorption spectrums in UV and VIS radiation [1].
A Cross Layer Optimization Based on Variable-Power AMC and ARQ for MIMO Systems  [PDF]
Shu-Ming Tseng, Wei-Shun Lei
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2010, DOI: 10.4236/ijcns.2010.35066
Abstract: To improve spectrum efficiency (SE), the adaptive modulation and coding (AMC) and automatic repeat request (ARQ) scheme have been combined for MIMO systems. In this paper, we add variable power subject to power constraint in each AMC mode. We use KKT optimization algorithm to get the optimal transmit power and AMC mode boundaries. The numerical results show that the average SE is increased by about 0.5 bps/Hz for 2 × 2 MIMO systems with Nakagami fading with parameter m = 2 when SNR is around 15 dB and the ARQ retransmission is twice.
Clinical and therapeutic implications of psychiatric comorbidity in high functioning autism/Asperger syndrome: An Italian study  [PDF]
Silvia Giovinazzo, Sara Marciano, Grazia Giana, Paolo Curatolo, Maria-Cristina Porfirio
Open Journal of Psychiatry (OJPsych) , 2013, DOI: 10.4236/ojpsych.2013.33034
Abstract: The present study describes the occurrence of psychiatric comorbid disorders in a cohort of 86 high functioning autism (HFA)/Asperger syndrome (AS) patients, examined at Child Neurology and Psychiatry Unit of Tor Vergata University. 38 patients out of 86 (44.2%) presented one or more psychiatric comorbidities, such as mood disorders, Attention Deficit/Hyperactivity Disorder (ADHD), Tourette syndrome (TS), anxiety disorders, including obsessive-compulsive disorder (OCD), and psychotic symptoms. We compared our sample with the evidences from the scientific literature on psychiatric comorbidity in ASD patient, in particular in HFA/AS. In this paper we focus on the high frequency of comorbid psychiatric disorders in HFA/AS patients, such as mood disorders, Attention Deficit/Hyperactivity Disorder (ADHD), Tourette syndrome (TS), anxiety disorders, including obsessive-compulsive disorder (OCD), and psychosis, including schizophrenia. We analyzed rates of all psichiatric comorbidities diagnosed in a sample of HFA/AS subjects and we compared findings from our study with the evidences from the scientific literature on psychiatric comorbidity in ASD patients, in particular HFA/AS. We point out that comorbid psychiatric symptoms can be hardly diagnosed, because they could present atipically in ASDs then in general population. Furthermore, they could be masked by ASD core symptoms.
Vector Boson Mass Spectrum from Extra Dimension  [PDF]
Dao Vong Duc, Nguyen Mong Giao
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.47133

Based on the mechanism for mass creation in the space-time with extradimensions proposed in our previous work, (arXiv: 1301.1405 [hep-th] 2013) we consider now the mass spectrum of vector bosons in extradimensions. It is shown that this spectrum is completely determined by some function of compactification length and closely related to the metric of extradimensions.

Method of Forming Stable States of Dense High-Temperature Plasma  [PDF]
Stanislav I. Fisenko, Igor S. Fisenko
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.44068

The concept of gravitational radiation as a radiation of one level with the electromagnetic radiation is based on theoretically proved and experimentally confirmed fact of existence of electron’s stationary states in own gravitational field, characterized by gravitational constant K = 1042 G (G-Newtonian gravitational constant) and by irremovable space-time curvature. The received results strictly correspond to principles of the relativistic theory of gravitation and the quantum mechanics. The given work contributes into further elaboration of the findings considering their application to dense high-temperature plasma of multiple-charge ions. This is due to quantitative character of electron gravitational radiation spectrum such that amplification of gravitational radiation may take place only in multiple-charge ion high-temperature plasma. In elaboration of the authors’ works [1-4], an essential instantiation of the concept of fusion plasma’s steady states formation (as the last paragraph outlines) and boundary conditions refinement in the electron’s stationary-states-in-proper-gravitational-field problem are appended to this article.

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