Vignan University

About: Vignan University is a education organization based out in Guntur, Andhra Pradesh, India. It is known for research contribution in the topics: Computer science & Control theory. The organization has 1138 authors who have published 1381 publications receiving 7798 citations.

Trust Establishment in Chaotic Cognitive Environment to Improve Attack Detection Accuracy Under Primary User Emulation

Abstract: In this paper, we propose a novel algorithm for primary user emulation attack detection and removal in cognitive radio networks, which are driven by chaotic tag-based sequencing for communication. Our proposed approach demonstrates the use of the look-up table-based challenge sequences which are monitored by the cognitive base station and act as the first line of defense against any primary user emulation attacker. This ensures that almost all of the attackers are suppressed, and for the remaining attackers if any, we use a tag-based chaotic communication system, wherein each of the requests from secondary users is sent like a chaotic noise sequence on the channel, and the receiving entity decodes this sequence in order to get the signal communicated by an authorized transmitter. If there is any communication by an attacker, then it is detected immediately, as none of the receiving entities can decode the signals sent by these unwanted attacker nodes. This ensures that our system guarantees greater than 99% detection and identification of attackers in primary user emulation attacks.

Spatio-temporal estimation of rainfall patterns in north and northwestern states of India between 1901 and 2015: change point detections and trend assessments

Abstract: Change point detection and trend analysis are the adopted techniques of time series analysis. We have applied non-parametric methods on the temporal and spatial-scale data of 115 years between 1901 and 2015 from ten different federal states in the north and the northwestern India to examine the change points as well as to estimate the future scenarios by examining the past trends. The change points were examined by Pettitt’s test, Standard Normal Homogeneity (SNH) test, and Buishand’s test, whereas the trend analyses of monthly, annual, and seasonal rainfall data were carried out using Sen’s slope estimator after assessing their statistical significance by Mann–Kendall (M-K) test. The trend analyses showed non-zero slope values and a few among them were of statistical significance. The results of our statistical experiment concluded that the trends of reduction in winter, pre-monsoon, and post-monsoon rainfalls would have notable effects on the rain-fed agricultural production in the near future, particularly in the areas without proper irrigation facility (e.g., parts of Uttar Pradesh). More extreme events of higher rainfall in some states (e.g., Goa, Maharashtra, and Jammu and Kashmir), however might cause disasters like landslide and flooding.

An efficient sliding–mode current controller with reduced flickering for quadratic buck converter used as LED lamp driver

Abstract: This paper presents mathematical analysis, design and simulation of a quadratic buck converter used as LED lamp driver, and the performance of the converter is compared with two different control strategies. The objective is to provide tight regulation of the LED current that can operate over a wide range of DC input voltages. The first control strategy is the non–linear Sliding–Mode (SM) current controller, and its design aspects include choice of sliding surface, deriving existing and stability conditions, control parameter selection and their analysis. This paper also throws light on Average Current–Mode (ACM) controller. The operation, modelling, designing and transfer function derivation for the inner current and outer voltage loops of the quadratic buck converter are presented. The tuning of controllers for the ACM controller is done using Bode plots, for achieving desired phase and gain margins. The simulation is done using PSIM software and the results are presented.