Hem Dutt Joshi

Exact SER Analysis of DFrFT-Based QPSK OFDM System over Frequency Selective Rayleigh Fading Channel with CFO

We present the exact symbol error rate (SER) expression for quadrature phase shift keying (QPSK) modulation in frequency selective Rayleigh fading channel for discrete fractional Fourier transform- (DFrFT-) based orthogonal frequency division multiplexing (OFDM) system in the presence of carrier frequency offset (CFO). The theoretical result is confirmed by means of Monte Carlo simulations. It is shown that the performance of the proposed system, at different values of the DFrFT angle parameter źź,ź is better than that of OFDM based on discrete Fourier transform.

BER Performance of SFBC OFDM System Over TWDP Fading Channel

In this letter, the performance of uncoded and space frequency block coding (SFBC) orthogonal frequency division multiplexing (OFDM) system over two-wave with diffuse power (TWDP) fading environment is analyzed. A general closed-form expressions of average bit error rate for both M-ary phase shift keying and M-ary quadrature amplitude modulation are derived using moment generating function of TWDP fading distribution. Results are verified with the benchmark results available in the literature (i.e., Rayleigh and Rician). Numerical results with various TWDP fading channel parameter (K and A) and with different modulation orders for uncoded and SFBC OFDM systems show excellent agreement with simulation results.

Study of digital image processing techniques for leaf disease detection and classification

In this paper, we address a comprehensive study on disease recognition and classification of plant leafs using image processing methods. The traditional manual visual quality inspection cannot be defined systematically as this method is unpredictable and inconsistent. Moreover, it involves a remarkable amount of expertise in the field of plant disease diagnostics (phytopathology) in addition to the disproportionate processing times. Hence, image processing has been applied for the recognition of plant diseases. The paper has been divided into two main categories viz. detection and classification of leafs. A comprehensive discussion on the diseases detection and classification performance is presented based on analysis of previously proposed state of art techniques particularly from 1997 to 2016. Finally, discussed and classify the challenges and some prospects for future improvements in this space.

Zadoff–Chu Sequence Based Timing Offset Estimation for OFDM Systems

In this article, timing synchronization in OFDM is attained with the help of Zadoff–Chu sequence as a training symbol. An algorithm based on the cross-correlation property of fractional Fourier transform (FRFT) is proposed to generate a new timing metric. In this algorithm, cross correlation of received signal and Z–Chu sequence is taken at the receiver side in FRFT domain. The mathematical analysis of proposed estimator has been done and the variance of timing metric is obtained under the effect of AWGN channel. The simulation result shows that the variance of timing metric decreases as signal to noise ratio increases. The mean and MSE of the timing offset is simulated under HYPERLAN indoor channel (type-A). The proposed estimation method has been compared with existing methods and established as a better method to combat timing offset.

Optimised periodic precoder-based blind channel estimation for MIMO-OFDM systems

ABSTRACT In modern wireless communication systems, multiple antennas at transmitter and receiver are employed along with orthogonal frequency-division multiplexing to achieve very high data rate with significant system reliability. To further enhance system performance, blind channel estimation techniques are employed whenever data symbols are transmitted in blocks. These estimation techniques are computationally expensive at almost all signal-to-noise ratio values. In this paper, periodic precoder-based blind channel estimation is used to tackle problems like complexity, channel order overestimation and bandwidth expansion. The system reliability can be improved, if precoder coefficients are chosen in such a way that they have no dependency or minimum correlation with noise coefficients. The overall bit error rate (BER) is derived and simulated with dependency on periodic sequence and channel estimation error. The simulation results shows that the presented precoding scheme performs better in terms of BER with minimum channel estimation error as compared to other state-of-the-art schemes.