Copyright © 2018 Authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. International Journal of Engineering & Technology, 7 (2.21) (2018) 228-231 International Journal of Engineering & Technology Website: www.sciencepubco.com/index.php/IJET Research paper Investigations on wavelet and Fourier transform based channel estimation in MIMO-OFDM system B. Somasekhar 1* , Ch.Mohana Krishna 2 , Y. Murty 3 1 Dept. of ECE, Anil Neerukonda Institute of Technology &Sciences, Visakhapatnam, Andhra Pradesh, India. 2 Dept. of ECE, SITAM College of Engineering, Vizianagaram, Andhra Pradesh, India. 3 Dept. of ECE, RGUKT IIIT Nuzividu, Andhra Pradesh, India. *Corresponding author E-mail: bssekharme@gmail.com Abstract In this paper channel estimation methods for MIMO-OFDM system are investigated based on Fourier Transform and Wavelet Transform. The channel estimation algorithm based on Discrete Fourier Transform (DFT) cause energy leakage in multipath channel with non-sample-spaced time delays. Discrete Cosine Transform (DCT) based channel estimator can mitigate the drawback of Discrete Fourier Transform based channel estimator, when the non-sample spaced path delays are available in multipath fading channels. Wavelet based systems provide better spectral efficiency because of no cyclic prefix requirement, with narrow side lobes and also exhibit improved BER performance. Simulation results reveal that the DWT based transform outperforms the conventional DFT and DCT based channel estimator in terms of bit error rate and mean square error. Keywords: Discrete Fourier Transform (DFT), Discrete Cosine Transform (DCT), Discrete Wavelet Transform (DWT), Channel Estimation. 1. introduction The Discrete Wavelet Transform (DWT) is broadly considered as an efficient approach to replace FFT in the conventional OFDM systems due to its better time-frequency localization, bit error rate improvement, interference minimization, and improvement in bandwidth efficiency. The design of transmitter and receiver for wavelet modulation is presented in [1]. This wavelet modulation evaluates the bit error rate in presence of additive white Gaussian noise. Kucur et al. [2] proposed a multicarrier modulation based on time-frequency localization of the pulse shaping that reduces both narrowband interference and multipath channel interference. Marius Oltean et al.[3] analyzed the bit error rate performance of DWT based multicarrier modulation for frequency-selective and time-variant channel. Angrisani et al. [4] investigated the significant effect of presence of noise on the performance of OFDM receiver. DWT based OFDM has the ability to combat the narrow band interference as the wavelets possess high spectral containment properties and making the system more robust beside inter-carrier interference. Comparison between Fourier based and Wavelet based OFDM is presents in [5,6]. Khaizuran Abdullah et al. [7] conclude that to select a suitable wavelet method i.e, the new modulation scheme (wavelet packet modulation) which is used instead of the conventional OFDM. Mohammed Aboud Kadhim et al[8] propound that by reducing PAPR in DWT based OFDM systems we can use the traditional sinusoid carriers of the FFT based OFDM instead of using suitable wavelets. The simulation results showed that the Complementary Cumulative Distribution Function of PAPR for the DWT based OFDM signal achieved about 7dB improvement than the traditional OFDM signals at 10 -3 of CCDF. Rohit Bodhe et al. [9] adopted DWT in place of FFT for frequency translation by using different modulation schemes i.e. 16-QAM, 32-QAM, 64-QAM and 128- QAM for both DWT and FFT based OFDM system model to achieve better performance in terms of Bit Error Rate for AWGN channel. It was found that all the wavelets perform better as compared to the IFFT-FFT implementation. El-Khamy et al. [10] proposed the use of discrete wavelet transform (DWT) in OFDM systems to mitigate the degrading effect of inter symbol interference successfully without using any cyclic prefix (CP). Therefore, bandwidth is conserved and the spectral efficiency is also improved. Anfal Ali Alansari [11] introduced the “Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing” (MIMO-OFDM) system with Discrete Wavelet Transform (DWT) which offered new improvement performance results which have not been exist in either individual MIMO or OFDM. The performance results of the individual OFDM, MIMO and MIMO-OFDM systems are discussed and a comparison between these systems is done. Somasekhar et al. [12] presented a pilot aided channel estimation for MIMO/ OFDM system in time-varying wireless channels. The performance analysis between Fourier BEM, DPSS models, Legendre and chebyshev polynomial based on Mean Square Error (MSE) is present. Simulation results show that the DPSS-BEM model outperforms the Fourier Basis expansion model. Govinda Raju et al. [13] presented the Haar and Daubechies based orthonormal wavelets which have the capability of reconstructing the transmitted signal at the receiver and the effect of noise is minimized using wavelet denoising for different values of SNR on AWGN channel. 2. DFT and DCT based channel estimation in MIMO-OFDM In OFDM systems, it is necessary to estimate the channel to obtain the channel state information (CSI), to overcome the distortion caused by fading.