Faculty Publications
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Publications by NITK Faculty
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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 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.