Faculty Publications
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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 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 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 Performance analysis of FSOC system over generalized turbulence channel with pointing errors using Po1SK signalling technique(Institute of Electrical and Electronics Engineers Inc., 2021) Palliyembil, V.; Krishnan, P.; Jagadeesh, V.K.; Muthuchidamdaranathan, P.; Ekpo, S.Optical Wireless communication (OWC) is used to provide high speed wireless connectivity to end users. OWC along the outdoor environment is called Free Space optical Communication (FSOC). Along with the high speed performance of this technology, it is cheap, secure and easy to install. In this work, the performance analysis of an FSOC system employing Polarization shift keying (PoISK) modulation over Málaga (M)-distributed channel is carried out. The communication channel is also considered as inducing pointing error fading. The closed-form expressions for BER and channel capacity for this proposed system are derived to quantitatively analyse the performance. © 2021 IEEE.Item Long haul, repeaterless, coherent optical multichannel communication systems employing hybrid multiplexing schemes wherein Wavelength Division Multiplexing (WDM) and Optical Code Division Multiplexing (OCDM) are combined is analyzed in the presence of performance limiting factors such as Inter Channel Interference (ICI), Stimulated Raman Scattering (SRS) and detector shot noise. Error control coding techniques in the form of rate 1/2 convolutional codes are employed in the system to counter these performance limiting factors. It is seen that the use of error control coding technique can enhance the system performance to such an extent that a Bit Error Rate (BER) performance of less than 10-8 is achievable without crossing the SRS power threshold for as many as 1000 to 1200 channels. Advantages of the hybrid multiplexed system over systems relying solely on WDM or OCDM are also discussed along with the advantages of using error control coding compared to optical amplification in countering the performance degrading factors.(Fachverlag Schiele und Sohn GmbH, Coding to enhance performance of hybrid multiplexed coherent optical communication systems in the presence of ICI and SRS) Kumar, M.S.; Bhat, K.N.H.; Umesh, G.2003Item Optimization of WDM lightwave systems (BAC) design using error control coding(Academic Press Inc., 2007) Mruthyunjaya, H.S.; Umesh, G.; Kumar, M.In a binary asymmetric channel (BAC) it may be necessary to correct only those errors which result from incorrect transmission of one of the two code elements. In optical fiber multichannel systems, the optical amplifiers are critical components and amplified spontaneous emission noise in the optical amplifiers is the major source of noise in it. The property of erbium doped fiber amplifier is nearly ideal for application in lightwave long haul transmission. We investigate performance of error correcting codes in such systems in presence of stimulated Raman scattering and amplified spontaneous emission noise with asymmetric channel statistics. Performance of some best known concatenated coding schemes is reported. © 2006 Elsevier Inc. All rights reserved.Item Design and construction of BCH codes for enhancing data integrity in multi level flash memories(Inderscience Publishers, 2012) Rajesh Shetty, K.; Ramakrishna, K.; Prashantha Kumar, H.; Sripati, U.Flash memories have found extensive application for use in storage devices. The storage capacity and reliability of these devices have increased enormously over the years. With increase in density of data storage, the raw bit error rate (RBER), associated with the storage device increases. Error control coding (ECC) can be used to reduce the RBER to acceptable values so that these devices can be employed to store information in applications where data corruption is unacceptable. In this paper, we describe the synthesis of BCH codes for flash memories based on multi level cell (MLC) concept. This is in continuation of our work on synthesis of BCH codes for improving the performance of flash memories based on single level cells (SLC). The improvement in device integrity resulting from the use of these codes has been quantified in this paper along with computation of parameters which allows modelling of flash memory as an equivalent channel. While synthesising codes, we have adhered to the limitations imposed by the memory architecture. Use of these codes in storage devices will result in considerable enhancement of device reliability and consequently open up many new applications for this class of storage devices. © 2012 Inderscience Enterprises Ltd.Item Hybrid scheme for CFO cancellation in OFDM systems(Acta Press, 2013) Savitha, H.M.; Kulkarni, M.In this paper, we combine maximum likelihood estimation (MLE) technique with improved sinc power (ISP) pulse shaping to cancel inter-carrier interference caused by carrier frequency offset in coded orthogonal frequency division multiplexing (OFDM) systems, thereby achieving an improved bit error rate (BER) performance as compared to the above two schemes. The BER performance of the OFDM system was checked for ISP pulse shaping alone, MLE technique with low pass filtering, and a hybrid scheme of MLE technique with ISP pulse shaping. It has been shown that, at normalized carrier frequency offset of 0.2 and BER of 10-5, the hybrid scheme with convolutional coding could achieve a BER performance improvement of around 1.78 and 4.83 dB, respectively, as compared to MLE technique with low pass filtering and ISP pulse shaping alone. © International Journal of Modelling and Simulation 2013.Item Gridable Electric Vehicle (GEV) Aggregation in Distribution Network to Support Grid Requirements: A Communication Approach(Walter de Gruyter GmbH info@degruyter.com, 2017) Hampannavar, S.; Chavhan, S.; Yaragatti, U.R.; Naik, A.Electric Vehicles (EV) can be connected to the grid for power transaction and also serve as distributed resource (DR) or distributed energy storage system (DESS). The concept of connecting group of EVs or gridable EVs (GEV) to the grid is called Vehicle-To-Grid (V2G). V2G is a prominent energy storage system as it is flexible and can be used to support the grid requirements in order to meet the time varying load demand. Optimal placement of GEV aggregation in power distribution network is very challenging and helps in maintaining stability of the power system for a shorter duration of time. In this paper, algorithm is developed for estimating parameters like Ploss, Qloss, Vpu based on past history and wireless access support for Control and Monitoring Unit (CMU) to aggregator agent communication is proposed using Long Term Evolution (LTE) protocol. The load flow studies are carried using MiPOWER software in order to obtain the optimal location for the placement of GEV aggregation in power distribution network. LTE physical layer is modeled using MATLAB/SIMULINK and the performance is analyzed using bit error rate (BER) v/s signal to noise ratio (SNR) curves. © 2017 Walter de Gruyter GmbH, Berlin/Boston 2017.