Faculty Publications
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Publications by NITK Faculty
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Item Performance analysis of energy efficient asymmetric coding and modulation schemes for wireless sensor networks(2010) Kamath, G.M.; Shekar, Y.; Abhijith, K.G.; Sripati, U.; Kulkarni, M.Wireless Sensor Networks generally operate under severe energy constraints. In many cases, the networks are star connected with battery-powered nodes sensing data and sending it to a centrally-powered base station, whose energy constraints are more fore-bearing than that of the nodes. In this paper, an approach for energy efficient communication by using different channel codes on the base-station to node link (downlink) and node to base-station link (uplink) is proposed and analysed for such a network topology. This is in effect shifting complexity from the node to the base station while continuing to have the same BER performance. Also the use of more energy efficient modulation schemes are explored. ©2010 IEEE.Item Performance Comparison of Hard and Soft-decision Turbo Coded OFDM Systems(IEEE Computer Society, 2010) Savitha, H.M.; Kulkarni, M.This paper compares the performance of hard and soft-decision turbo coded Orthogonal Frequency Division Multiplexing systems with Quadrature Phase Shift Keying (QPSK) and 16-Quadrature Amplitude Modulation (16-QAM). The results show that the softdecision method greatly outperforms the hard-decision method. Using simplified algorithm for the soft-output demapper in the 16-QAM constellation, the complexity of the demapper is greatly simplified. ©2010 IEEE.Item A novel method for jammer localization in large scale sensor networks(2010) Rau, A.V.; Raghuvara, R.; Shashimohan, V.; Kulkarni, M.Sensor networks, by their very nature, are vulnerable to network security threats, with Denial of Service by radio jamming being one of the most common. It is more useful to detect jamming reactively than to proactively avoid it. We describe a method of countering jamming wherein some nodes just outside the jammed region form groups and transmit their locations to the Base Station for localization. These nodes are downstream in the hop-count based gradient broadcast routing sense. We also estimate the exact position of the jammer using the centre of curvature method. Simulation results show that the error in estimation of the jammer location is as low as 1.03m, accurate enough for real-time response. ©2010 IEEE.Item An improved turbo decoding scheme for impulsive channel(2010) Savitha, H.M.; Kulkarni, M.This paper proposes a novel turbo decoding scheme for additive white class A noise (AWAN) channel. It compares the performance of turbo coded systems with Quadrature Phase Shift Keying (QPSK) and 16-Quadrature Amplitude Modulation (16-QAM) on AWAN channel with two different channel values-one computed as per additive white Gaussian noise (AWGN) channel conditions and the other as per AWAN channel conditions. The results show that the use of appropriate channel value in turbo decoding helps to combat the impulsive noise more effectively. Also, the Bit error rate (BER) performance of the proposed model for AWAN channel is compared with that of AWGN channel. It is observed that they exhibit comparable BER performance. ©2010 IEEE.Item MIMO radar with spatial-frequency diversity for improved detection performance(2010) Shanbhag, K.V.; Deb, A.; Kulkarni, M.The Multiple Input Multiple Output (MIMO) radar concept exploits the independence between signals at the array elements unlike beamforming which presumes a high correlation between signals either transmitted or received by an array. Radar Cross Section (RCS) of a complex target varies with both transmitted frequency and target geometry. By widely separating transmit and receive antennas, MIMO radar systems observe a target simultaneously from different aspects resulting in spatial diversity, thus improving the detection performance. Also by utilizing different frequencies, independent RCS of the target can be observed, thus resulting in frequency diversity. In this paper, the spatial and the frequency diversities are studied together to bring out the combined benefits. The system proposed will not only have several antennas appropriately spaced but also several operating frequencies appropriately spaced, providing a better detection performance than conventional MIMO radar systems for the same transmission power. The simulation results exhibit a better detection performance of the proposed system as compared to MIMO radar systems with only spatial diversity. ©2010 IEEE.Item A simple single seeded region growing algorithm for color image segmentation using adaptive thresholding(2011) Verma, O.P.; Hanmandlu, M.; Susan, S.; Kulkarni, M.; Jain, P.K.In this paper, we present a region growing technique for color image segmentation. Conventional image segmentation techniques using region growing requires initial seeds selection, which increases computational cost & execution time. To overcome this problem, a single seeded region growing technique for image segmentation is proposed, which starts from the center pixel of the image as the initial seed. It grows region according to the grow formula and selects the next seed from connected pixel of the region. We use intensity based similarity index for the grow formula and Otsu's Adaptive thresholding is used to calculate the stopping criteria for the grow formula. We apply the proposed method to the Berkley segmentation database images and discuss results based on Liu's F-factor that shows efficient segmentation. © 2011 IEEE.Item Performance analysis of fountain codes with Robust Soliton distribution for erasure channels(2011) Prakash, G.; Nayak, M.; Kulkarni, M.; Sripati, U.Fountain Codes are essentially Forward Error Correction (FEC) codes, which were developed for applications involving multicasting or for delivering large amounts of content to multiple recipients simultaneously. FEC increases the reliability of a system in a noisy environment. Luby Transform codes (LT codes) which come from a new coding family of the Fountain codes are the first realization of rateless codes which can generate potentially limitless code words from data. In this paper, a performance analysis of Fountain codes for erasure channels, which use the Robust Soliton distribution for encoding the data packets and belief propagation to decode the received packets has been carried out Results show that the overhead during decoding is around 11.2%. © 2011 IEEE.Item Energy efficient shortest path routing protocol for wireless sensor networks(2011) Shivaprakasha, K.S.; Kulkarni, M.Wireless Sensor Networks (WSNs) have become one of the emerging trends of the modern communication systems. Routing plays a vital role in the design of a WSNs as normal IP based routing will not suffice. Design issues for a routing protocol involve various key parameters like energy awareness, security, QoS requirement etc. Energy awareness is one of the vital parameters, as the batteries used in sensor nodes cannot be recharged often. Many energy aware protocols were proposed in the literature. In this paper, we propose a new Energy Efficient Shortest Path (EESP) algorithm for WSNs, which manages uniform load distribution amongst the paths so as to improve the network performance as compared to the traditional shortest path routing strategy. © 2011 IEEE.Item A novel hybrid scheme using MLE with pulse shaping for ICI cancellation in OFDM systems(2012) Savitha, H.M.; Kulkarni, M.Carrier frequency offset (CFO) in orthogonal frequency division multiplexing systems results in heavy degradation to the system performance. Pulse shaping and Maximum likelihood estimation (MLE) are two of the several techniques available in the literature for reducing the undesired effects caused by CFO using inter carrier interference (ICI) cancellation and CFO correction respectively. In this paper, we combine these two techniques to cancel ICI further, thereby achieving a better bit error rate (BER) performance than the BER achieved by either of the two above mentioned schemes. It has been shown that around 1.7 dB BER performance improvement could be achieved using the new hybrid scheme as compared to MLE technique with low pass filtering. Further, the hybrid scheme adopted in this work is less sensitive to CFO compared to pulse shaping scheme. © 2012 IEEE.Item Geographical location based hierarchical routing strategy for wireless sensor networks(2012) Kumar, P.; Chaturvedi, A.; Kulkarni, M.The overall performance and thus the achievable efficiency of wireless sensor networks (WSNs) rely on the type of protocols deployed to support particular application in hand. In WSN, network's lifetime depends upon the residual energy of individual nodes. In this paper; a brief survey comprises of various reported methodologies that make uses of geographical location attributes for routing in WSN is presented. To assist the routing algorithm on location aspect of the source and destination as well as other intermediate nodes; a location index is formulated based on binary encoded spatial frames. The merit of proposed spatial encoding scheme is its supportiveness on scalability aspects, so it can be easily tailored to accommodate hierarchy based network architectures. Further, the scheme incorporates an effective mechanism to select cluster heads for each cluster in such a way so as to avoid the localization of hot spot effects right from cluster level to network level. © 2012 IEEE.