Orthogonal frequency division multiplexing (OFDM) provides an effective and low complexity means of eliminating inter symbol interference for transmission over frequency selective fading channels. In OFDM systems, channel estimation is very crucial to demodulate the data coherently. For good channel estimation, spectral efficiency and lower computational complexity are two important points to be considered. In this paper, we explore Iterative channel estimation based on Least Square (LS) and Minimum Mean Square Error (MMSE) methods in order to improve Mean Square Error (MSE) by applying the Iteration. Using the appropriate adaptive algorithm, it is shown that with adequate number of iteration, channel estimation can be improved by reducing computational complexity. It has been shown that MSE improves if the initial estimate is better than primary LS or MMSE estimate.
A microstrip fractal antenna has been introduced in the following paper. The iterations of hexagons are placed over one another in such a way that they do not overlap and each and every hexagon is clearly visible. The presented antenna has been fed with 50Ω probe. The antenna operates at a frequency of 0.6 GHz giving the input return loss of about -13.5 dB. The performance of the antenna has been evaluated using HFSS, V12, from Ansoft. The resulting antenna has a ground plane side each of 7cm. The antenna can find wide variety of applications in LTC5540, cognitive radio, radar systems, satellite communication, and highspeed digital clock generation. The paper aims to construct antennas using fractal patterns in order to obtain desired performance properties such as compact size and multi-band behaviour. The hardware has also been designed keeping in mind all the physical considerations and the results were obtained by plotting the radiation pattern on the graph paper using the antenna turn table.
This paper proposes bargaining for online transaction or for online purchase of a particular product that plays an important role in the benefit of the online retailers and customer as well, keeping profit margin into consideration. Customers get benefited by purchasing the product at its best possible value. Price of a particular product is set for a particular day, totally depends on the analysis made on the historical data of a product sold i.e. last seven days or last week, which is called as dynamic pricing. Online bargain is continuously ongoing process for which the price of the product for next day to be set is calculated at the end of each day. Calculation of the price to be set is done by the data gathered from different website into the main server. Wherein the processing takes place and compares the price set with amount entered by the customer for negotiation. Customer has two attempts for bargain that offers best price so as to deal or exit from the process. Process of bargain takes place if amount entered by the customer falls in the range of bargaining frame. In this proposed paper two types of profit will be attained by the retailer.
In this paper, we propose a method of genetic algorithm (GA) for information retrieval (IR) based on Singular Value Decomposition and Principal Component Analysis. The main difficulty in GA based IR system is processing of high dimensional input strings, as affects the performance in terms of retrieval time. In proposed work, we tried to reduce the high dimensional input data to low dimensional in order to improve retrieval time. Singular Value Decomposition (SVD) and Principal Component Analysis (PCA) computations are done on input data streams to produce reduced rank matrix approximation and orthogonal transformations. With this reduced matrix we got promising results in terms of computation time when GA is applied for IR. Experiments were performed on sample dataset of 2500 input documents and weighted vectors are generated. Information retrieval is done using two techniques PCA-GA and SVD-GA with all classical matching functions. It is found that PCA-GA performs well as compared to SVD-GA in terms of computational time.
Artificial Neural Networks has number of applications in the various fields like filtering, pattern recognition, function approximation and control problems. Number of non-linear transformation problems can be solved using these fields. Randomizing the various parameters is a common paradigm like random initialization of weights to zero and generating weights randomly. To minimize the error the first order or second order derivatives are used. The training of the neural network is done so that the error is minimized. In this paper the artificial neural network parameter weights are initialized to zero and are generated randomly during the training of the network. Then the error obtained is compared when there is no change in the back-propagation algorithm and when changes are done with weights zero and random both. The results indicate that it is feasible to perform training by initializing the weights to zero also though the results are higher approximately by a factor of two or three from the results obtained when the weights are generated randomly and learning rates made Gaussian.
Data transfer is a big overhead for cloud workflows due to pay-as-use business model of cloud environment. In such environment, the cost arising from data transfers between resources as well as execution costs must also be taken into account during scheduling based upon user`s Quality of Service (QoS) constraints. In this paper, we present Priority based Genetic Algorithm BCHGA to schedule workflow applications to cloud resources that optimize the total cost of workflow within the user`s specified budget. Each workflow`s task is assigned priority using bottom level (b-level) and top level (t-level). To increase the population diversity, these priorities are then used to create the initial population of BCHGA. The proposed algorithm is simulated in java and evaluated with synthetic workflows based on realistic workflows from the different areas by considering the pricing model of cloud service provider like Amazon. The simulation results show that our proposed algorithm has a promising performance as compared to Standard Genetic Algorithm (SGA).
Image Compression plays a critical role in several important and diverse applications and has motivated the need for better image compression algorithms. Wavelets provide a powerful method for image compression; wavelet transform and wavelet packet transform have proved to be efficient and useful tools for image processing in the recent years. This paper aims at comparing different parameters of some well known wavelets at various threshold values concerning the quality of the reconstructed image. This paper attempts to compare compression performance using wavelet transform and wavelet packet transform for level 5 decomposition and highlights most desirable characteristics of wavelets.
In this paper, the zero voltage switching (ZVS) in active clamp forward converter is investigated. The investigation starts with discussing the basic operating principle of active clamp forward converter (ACFC). The current mode control ZVS ACFC design procedure is also presented in detail. A prototype forward converter with dc input of 16V, output voltage 5V operating at rated output load of 4A and a switching frequency 400 khz is provided to analyse the main mosfet switching waveform under zero voltage condition.
As computing technology becomes more tightly coupled into dynamic and mobile world of the Internet of Things (IoT), security mechanism becomes more stringent, less flexible and intrusive. Scalability issue in the IoT makes Identity Management (IdM) of ubiquitous things more challenging. Forming ad-hoc network, interaction between these nomadic devices to provide seamless service extend the need of new identities to the things, addressing and IdM in the IoT. New identities and identifier format to alleviate the performance issue is introduced in this paper. This paper presents novel Context-aware Clustering with Hierarchical Addressing (CCHA) scheme for the things with new identifier format. Simulation results shows that CCHA achieves better performance with less energy expenditure, less end-to-end delay and more throughput. Results also show that CCHA significantly reduces the failure probability. Furthermore, this paper also presents the framework for IdM in the IoT and mathematical model for queuing analysis.
In this paper, we present the significance of computer simulation program, such as ORCAD PSPICE, in analyzing, first order approximations of circuit behavior, a closed loop, non-isolated dc-dc converter with synchronous rectifier circuit. Following techniques have been adopted to simplify the process of simulation. They are: (1) Ideal switches are incorporated in the power stage of the converter to eliminate the gate diver requirement which in turn reduces the simulation run time; (2) Diodes are connected in series with switches, which eliminates dead time control circuit, to prevent cross conduction of switches and (3) TL494 Pspice model, which is readily available in library of most of the versions of the ORCAD PSPICE, is employed for pulse width modulation. As an example, non-inverting synchronous buck boost converter is considered for demonstrating the approach. Simulation was carried out for an input voltage range of 6 to 35V and load resistance was varied from 12 to 48 Ohms. Output voltage was regulated at 12V for both input voltage and load current perturbation. Physical prototype was implemented and simulation result was tested for steady state output.
Energy efficiency is an imperative design consideration in wireless network due to the inadequate battery life of mobile terminals. Next to power management techniques, a considerable investigation needs to be dedicated on low-power routing algorithmic design to augment the energy efficiency of such systems. This work demonstrates an efficient and low-power design in ad-hoc networks with required QoS by means of optimization of AODV routing algorithm. This work evaluates optimized AODV route information based IEEE 802.11g ad-hoc network incorporating OFDM radio network interfaces along with DCF-MAC protocol by means of OPNET Modeler TM to realize an energy-efficient IEEE 802.11g network.
Morphological analyzer is a tool which identifies and analyzes the internal structure of given word and also gives the morphological and grammatical information associated with the given word. Kannada is an inflectional, derivational, agglutinative and morphologically very rich language. Developing a well-fledged morphological analyzer (MA) for Kannada is a challenging task. In this paper, a hybrid MA for Kannada verbs is proposed as a part of machine translation system from Kannada to any other language. This model is developed using suffix-stripping, rule-based and paradigm-based approaches. The performance of this model is tested against a set of verbs randomly taken from a well-known dictionary called “Kannada Rathna Kosha” [1].
Routing has always been one of the key challenges in mobile ad hoc networks. Ad hoc networks prefer reactive routing over proactive routing due to the rapid changes in nodes position. Geographic position based routing is a convenient method to route a packet from a source to a destination based on the local information alone. Geographic forwarding implements a greedy routing technique that selects a forwarding node that is closer to the destination than itself. If this fails the packet is trapped in a dead end caused by holes and/or obstacles. In this paper, we present a routing scheme, which avoid dead ends and also packet loss. This scheme finds an efficient forwarding node which is a reliable non concave node with high residual energy levels to forward an incoming packet. Through simulation experiments it is proved that our scheme solves the dead end problem and also packet loss.
Intel 8051 microcontroller based capacitance meter has been developed based on the time lag involved in charging and discharging the capacitor. The value of the capacitance is shown using a LED interface. Continuous and precise measurement required for a two phase flow sensor is obtained using the PC connected via RS-232 interface. The instrument covers a range of 0.0125 pF to 1000uF with a resolution of 0.0125 pF. The system is successful in the measurement of capacitance with an accuracy of 0.5%.
This paper presents impact of seasonal variation of soil resistivity on performance indices of grounding system. The grounding system initially designed for uniform soil, may become two layer or multilayer soil structure due to seasonal variation such as rainy, early spring and winter season. The formation of low or high resistivity soil layers leads to change grounding grid resistance and affects the most stringent safety criterion like step and touch voltages on the ground surface. The grounding system is extensively analysed for various seasons like raining and freezing in winter considering two layer soil model due to formation of low or high resistivity soil layers. Moreover, safety is analysed using multilayer soil model for some cases. The study reveals that the grounding grid designed for uniform soil may becomes unsafe during freezing and early spring. Therefore, grounding system must be designed very carefully. Use of long vertical ground rods can effectively attenuates the seasonal influence and improves the safety of grounding system. The simulation has been carried out by using Autogrid-Pro grounding software of SES & technology, Canada.
In this paper, a rectangular inset feed microstrip antenna with defected ground plane for UWB application is presented. It is found that by making symmetrical T-shape slots just beneath the radiating patch in the ground plane results UWB characteristics. Parasitic effect is minimized by optimization in the shape of slot like width and length, so that uniform return loss is obtained in the entire UWB range. The simulated and fabricated antenna design shows return loss below -12 dB and voltage standing wave ratio below 2 in the entire UWB range. A very wide impedance bandwidth of 11.2 GHz at -10dB return loss has been obtained. Further, band notching property to avoid the signal interference from existing WiMax system in the environment has been obtained by varying ground structure. The effect of first T-cut slot in ground structure has been observed to result band notching from 3.28 to 4.58 GHz. Therefore, the proposed antenna overcomes the signal interference problem with existing WiMax IEEE 802.16 system and can be suitably used for UWB application.
The present silicon based devises such as IGBT and MOSFET operate at low switching frequencies of about 40 kHz and 100 kHz respectively. This means that we need to have some other new device that can switch in the range of MHz and which is more efficient than the silicon based devices. As for as high speed devices are concerned, we have SiC and GaN devices. Although SiC is an efficient and matured device, it is found to be costlier (10 times) than silicon based devices. Due to this, its application is limited to high power converters. The next emerging power electronic device is GaN (Gallium nitride). Only few manufacturers have released the product in low voltage and current level. As for as the cost is concerned, by 2015, it will be within the range of today's silicon device price. GaN device offers five key characteristics: high dielectric strength, high operating temperature, high current density, high speed switching and low on resistance. In this paper we present the results of the mathematical model developed to characterize the switching and conduction losses in GaN and CoolMOS switches. GaN device models are then used in a 500W DC-DC Boost converter to calculate efficiency and compared with that of CoolMOS device.
In Modern communication systems, design and development of wireless sensor network plays a very crucial role, especially for broadcast communication. This paper describes a medium access control protocol for wireless sensor networks designed for broadcast communication. The RI-MAC (Random Interference Medium Access Control) protocol uses random slot assignment in each MAC frame, along with knowledge of neighbors' transmission schedules to mitigate some of the energy wasting problems with existing MAC protocols. RI-MAC conserves energy, transmits messages fairly among the nodes in the system, and is adaptive to changes in the topology. Preliminary evaluation tests indicate that RI-MAC uses less energy than CSMA.
In this paper existing sliding mode control for nonlinear dynamic systems is demonstrated and its performance is evaluated against conventional PID controller . The changes in system dynamics occurs due to parametric uncertainties and external disturbances. Here it is shown that the sliding mode control based on the variable structure control is a robust control technique against parametric uncertainties and external disturbances. The effect of chattering in SMC is reduced using a boundary layer approach. The PID controller being a fixed structure control system is sensitive to parametric uncertainties and external disturbances. The sliding mode control and PID controller are illustrated in computer simulation for modeled spring-mass dashpot system and coupled tank system. Finally the performances of SMC are compared with conventional PID controller for the above systems to show the dominance of SMC over conventional PID controller.
A software birthmark is a set of characteristics extracted from an executable program. It is difficult to remove by modifying the program binary and is specific enough to distinguish it from other programs. Software birthmark techniques are used to detect program theft by determining the similarity between two different programs. In this paper, we propose a software birthmark based on a graph-based structure comparison scheme. By enhancing the function level comparison and the basic block level comparison algorithms, we show that software birthmarks can have improved resilience compared to those of the original graph-based structure comparison scheme.
