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Sridevi, K.
- Effect of Fragment SIZE and Contention Window on the Performance of IEEE 802.11 WLANs
Authors
1 Department of ECE, GITAM Institute of Technology, GITAM University, Visakhapatnam, A.P., IN
Source
Wireless Communication, Vol 4, No 9 (2012), Pagination: 467-471Abstract
Wireless communications is, by any measure, the fastest growing segment of the communications industry. The IEEE has standardized the 802.11 protocol for Wireless Local Area Networks. The IEEE 802.11 standard has defined two different access mechanisms in order to allow multiple users to access a common channel, the Distributed Coordination Function (DCF) and a centrally controlled access mechanism called the Point Coordination Function (PCF). DCF is a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) scheme with Binary Exponential Backoff algorithm (BEB). DCF describes two techniques to employ for packet transmission: the two-way handshaking technique called basic access mechanism and an optional four way handshakin technique, known as request-to send/clear-to-send (RTS/CTS) mechanism. In noisy channel, data packets become erroneous, and retransmission reduces the throughput. IEEE 802.11 allows fo fragmentation tuning and rate selection to achieve highest throughput in bad channel conditions. If an error rate is known, the parameters like fragment size and contention window can be adjusted to obtain the maximum throughput. In this paper, an analytic model is developed to evaluate the throughput of IEEE 802.11 wireless networks over noisy channels using constant backoff window. The optimal Contention window and fragment size are calculated using this model.
Keywords
IEEE 802.11b, BER, Fragmentation, Contention Window.
- Comparison of Percentage of Emission in Optical Communication for Different Receivers
Authors
1 Department of Electronic and Communication Engineering, GIT, GITAM University, Visakhapatnam, IN
Source
Networking and Communication Engineering, Vol 3, No 14 (2011), Pagination: 890-893Abstract
A review of free space optical communications systems is presented. Communication topics such as modulation and detection are discussed in relation to optical links. Negative channel effects such as scattering and absorption are investigated with respect to their impact on the channel and the associated bit error rates. The challenges posed by atmospheric disturbances are considered. New sources and detectors in transmitter and receiver circuits are proposed. Finally, power link budgets are prepared for free space systems to illustrate the losses incurred during transmission.Keywords
Free Space Optical Communication, Modulation, Detection, IMPATT Diode.- An Insight into Adaptive Elliptical and Hexagonal Arrays Synthesis using Normalized Fractional Least Mean Squares Algorithm
Authors
1 Department of ECE, GITAM University, Visakhapatnam - 530045, Andhra Pradesh, IN
2 Department of ECE, VR Siddhartha Engineering College, Vijayawada - 520007, Andhra Padesh, IN
Source
Indian Journal of Science and Technology, Vol 9, No 26 (2016), Pagination:Abstract
Background: Over the last two decades the use of adaptive arrays in wireless industry has seen a rapid growth. Smart antennas have the capability of ability to direct its main beam towards the desired user and supress nulls at the same time. Methods: In this paper, two different arrays namely elliptical and hexagonal arrays are considered. Four stochastic gradient based algorithms; Least Mean Squares (LMS), Fractional Least Mean Squares (FLMS), Normalized Least Mean Squares (NLMS) and Normalized Fractional Least Mean Squares (NFLMS) are evaluated. Findings: From the results conducted it is shown that hexagonal array using Normalized Fractional Least Mean squares algorithm as the weighting scheme provide optimum results in terms of side lobe reduction and more precise main beam direction when compared to the other array configuration taken into consideration. Applications: Smart antennas increase signal range, suppress the interfering signals to a minimum range which provide greater advantage in wireless systems.Keywords
Antenna Arrays, Array Factor, NFLMS, Side Lobe Reduction, Smart Antennas.Full Text
- Performance Evaluation of Smart Antennas Employing Adaptive Elliptical and Hexagonal Arrays using Particle Swarm Optimization and Genetic Algorithm
Authors
1 Department of ECE, GITAM University, Visakhapatnam - 530045, Andhra Pradesh, IN
2 Department of ECE, VR Siddhartha Engineering College, Vijayawada - 520007, Andhra Pradesh, IN
Source
Indian Journal of Science and Technology, Vol 9, No 26 (2016), Pagination:Abstract
Background: With the advent of smart antennas, there has been a phenomenal technological development in wireless communications industry. They paved path to number of new inventions that gave a boost to mobile industry. In this paper a comparison on elliptical array and hexagonal array of uniformly excited isotropic antennas are studied. Methods: The configurations generate maximum directive beam with reduced side lobe level. Two optimization techniques were used, particle swarm optimization and genetic algorithm. Both the arrays are evaluated in terms of efficient null placing and side lobe levels reduction using the algorithms taken into consideration. Findings: Hexagonal array using particle swarm optimization has better beam forming capabilities with reduced side lobe levels when compared elliptical array configuration. Applications: Smart antennas combat signal fading and suppress interfering signals from unwanted directions and thereby increase the capacity of wireless systems.Keywords
Array Synthesis, Elliptical Array, GA, Hexagonal Array, PSO, Smart Antennas.Full Text
- Image Reader for Visually Impaired People
Authors
1 Department of Electronics and Communication Engineering, Sri Eshwar College of Engineering, Coimbatore, TamilNadu, IN
Source
Digital Image Processing, Vol 11, No 2 (2019), Pagination: 33-34Abstract
In this society there are millions of visually impaired people, our paper introduces an innovative, efficient and real-time cost effective technique that enables user to hear the contents of text images instead of reading through them. It combines the concept of Optical Character Recognition (OCR) and Text to Speech Synthesizer (TTS) in Raspberry pi. This type of system helps visually impaired people to interact with computers effectively through vocal interface. Text Extraction from color images is a challenging task in computer vision. Text-to-Speech conversion is a method that scans and reads English alphabets and numbers that are in the image using OCR technique and changing it to voices. This paper describes the design, implementation and experimental results of the device. This device consists of two modules, image processing module and voice processing module. The device was developed based on Raspberry Pi v2 with 900 MHz processor speed.
Keywords
OCR, Text to Speech Converter, Image and Voice Processing.References
- Optical Character Recognition (OCR) enhancement using an approximate string matching technique - KraisakKesorn and PhornsiriPhawapoothayanchai Department of Computer Science and Information Technology, Faculty of Science, Naresuan University, Phitsanulok, Thailand
- Text to Speech Conversion System using OCR – Jisha Gopinath, Aravind, Pooja Chandra, Saranya S, Department of Electronics and Communication, SBCEW, Kerala, India