Performance of free space optical communication using M-array receivers at atmospheric conditions

Abstract: In free space optical (FSO) communication links, atmospheric parameters including absorption, scattering and turbulence have significant impacts on the quality of laser beams propagating through the atmosphere. Absorption and/or scattering, due to atmospheric particles result in optical losses, whereas turbulence contributes to the intensity scintillation that can severely impair the operation of FSO communications systems. In this paper, using a modified model we analyze the atmospheric effects on the signal-to-noise ratio (SNR) and the bit error rate (BER) of an FSO system. We show that there is an improvement in BER when using M-array receivers instead of one a single receiver

Waste Dump Site Selection by Using Fuzzy VIKOR

Considering the nature of open pit mines, harvest volume, it usually is required to remove a lot of waste to access to mineral planned grade. So, one of the most important part of open pit mines design, is waste dump site selection. Many factors are effective in waste dump site selection. These factors are sometimes in conflict with each other. So selecting the desired location for waste dump is a process complex and multi-criteria decision making. There are a variety of methods for decision making under complicated condition, such as fuzzy, Delphi, multi-criteria decision making and Expert system methods can be hinted. VIKOR method, which is one of the decision making multi criteria methods, is useful tool for decision-making. On the other hand with regard to uncertainty in decision-making, fuzzy approach is a useful tool for this purpose. This article has tried to select the best waste dump site in Sari Gunay Gold Mine by Fuzzy VIKOR. The results show that C position has a higher priority than other positions

The Impact of Managerial Credibility on Affective Organizational Commitment: An Empirical Study in the Sport Sector of Iran

The paper aims to study the impact of credibility of manager on employees’ affective commitment. Data were collected using a questionnaire including managerial credibility and affective commitment measures. A sample of 212employeesfrom a number of organizations operating in the sport sector of Iran was used. Confirmatory factor analysis (CFA) and a linear regression analysis were used to test the relationship between managerial credibility and affective commitment. In addition, ANOVA analysis was used to determine the effect of demographic characteristics on perceptions of manager credibility. The findings indicated that the relationship between and affective commitment is positive and significant. Moreover, when people perceive manager credibility, they feel more affectively attached to their organizations, experience a sense of obligation/loyalty towards them, and feel less instrumentally committed. Sampling was one of the limitations identified in this study. The fact that convenience sampling was used meant that results were not immediately transferable to the general working population. If samples were drawn from a wider range of demographics, then the results become more meaningful. By utilizing credibility, managers can promote affective organizational commitment and, thus, individual and organizational performance. It allows them to experience senses of purpose, self-determination, enjoyment and belonging. The paper contributes by filling a gap in the organization and management literature, in which empirical studies on managerial credibility as an antecedent of affective organizational commitment have been scarce until now.Key words: Credibility; Affective commitment; Employe

Performance of sub-carrier modulated Free-Space Optical communication link in negative exponential atmospheric turbulence environment

Free-Space Optical (FSO) communication is reputed for its ability to proffer solution to the access network bottle-neck but when used over long range communication links, it suffers from scintillation caused by the atmospheric turbulence. The scintillation is modelled using the negative exponential distribution. Hereby, we present the outage probability and the bit error probability equations of digital sub-carrier intensity modulated FSO system in atmospheric turbulence

A modified model of the atmospheric effects on the performance of FSO links employing single and multiple receivers

In free space optical (FSO) communication links, atmospheric effects including absorption, scattering and turbulence have significant impacts on the quality of the laser beam propagating through the free space channel. Absorption and/or scattering due to the atmospheric particles result in optical losses, whereas turbulence contributes to the intensity scintillation which can severely impair the operation of FSO links. In this paper, using a modified model we analyze the atmospheric effects on the signal-to-noise ratio (SNR) and the bit error rate (BER) performance of an FSO system. We show that for multiple detectors with the same surface area as a single detector there is a critical link range less than which the SNR decreases for larger values of M

Blickling homily 7

In free space optical (FSO) communication links, atmospheric turbulence has a significant impact on the quality of a laser beam propagating through the atmosphere. Turbulence results in intensity scintillation, which can severely impair the operation of target designation and FSO communications systems. Two important parameters for describing quality of FSO communications systems are the signal-to-noise ratio (SNR) and the bit error rate (BER). In this paper, using a modified model we analyze the effect of atmospheric turbulence on the SNR and BER for an FSO system in both weak and strong turbulence conditions

Terrestrial free-space optical links with temporal diversity

In this work, the performance of subcarrier intensity modulated terrestrial free-space optical communication link is analysed in the presence of noise and atmospheric turbulence induced fading. To ameliorate channel fading we propose subcarrier time delay diversity (TDD) in which delayed versions of the original data are retransmitted on different subcarriers. The most efficient TDD is obtained with single re-transmission with an estimated gain of up to 4.5 dB in weak turbulence

Error performance of terrestrial free space optical links with subcarrier time diversity

In this work, the performance of binary phase shift keying (BPSK) subcarrier intensity-modulated terrestrial free-space optical (FSO) communication link is analysed in the presence of noise and atmospheric turbulence. To ameliorate channel fading caused by the atmospheric turbulence, we propose a subcarrier time delay diversity (STDD) scheme in which the delayed versions of the original data are re-transmitted on different subcarriers. In short range links, a single re-transmission scheme results in an estimated gain of up to 4.5 dB in received irradiance. With sufficient link margins, short range FSO links might be able to cope without the use of any diversity techniques but for links spanning over 1 km, turbulence induced fading effect must be compensated for. In this study, the authors show that the subcarrier STDD is a viable scheme for this purpose

Free-space optical communication employing polarization shift keying coherent modulation in atmospheric turbulence channel

A binary polarization shift keying (2PolSK) scheme with a coherent heterodyne receiver for a free space optical (FSO) link through atmospheric turbulence channel is proposed and discussed. The maximum ratio combining (MRC) and equal gain combining (EGC) spatial diversity techniques have been applied to mitigate the turbulence induced irradiance fluctuation with bit error rate (BER) expressions derived for each. The communication channel is modelled as a gamma-gamma channel. The analysis of the 2PolSK characteristics is based on the error performance in turbulence regimes from weak to strong. Simulation results show that using the proposed system with MRC offers the best performance but at the cost of high system complexity

A Survey on Perception Methods for Human-Robot Interaction in Social Robots

10.1007/s12369-013-0199-6International Journal of Social Robotics6185-11