Different type of transform techniques such as Discrete Hartley transform (DHT), Discrete Cosine Transform (DCT), Fast Fourier Transform (FFT) and their inverse are used for the fast computational algorithms in digital signal processing. These transforms are used to perform the modulation and demodulation operations for the OFDM system. In this paper the three transforms are describe, these transforms are used in OFDM and shows the comparison between these different schemes used in OFDM system and also the simulation results based on the BER performances. General Terms Orthogonal Frequency Division Multiplexing, Fast Fourier Transform (FFT), Discrete Fourier transform (DFT), Discrete Fourier Transform (DFT).

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Implementation and Contrasting Comparision of Transform Techniques of OFDM

Mulberry leaf is the sole food material and its nutrition is necessary for growth regulating factors in silkworm, Bombyx mori L. Silkworm derives proteins directly from the mulberry leaves for producing nearly 70 per cent of silk. Unpruned mulberry plant was found to produce less quantity of leaves with poor quality. Periodic pruning is important to maintain vigorous young shoots and foliage with proper nutrients. In irrigated condition, where intensive cultivation is carried out, it is necessary to prune the plants to maintain their peak production. Whereas in rainfed condition mulberry is pruned to the height of 60-90 cm as middle pruning above the ground level to sustain moisture in the shoot and enhanced vegetative growth in mulberry which in turn enhance the leaf yield and quality (Rangaswami et al., 1976).

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Effect of Pruning height on Different Varieties of Mulberry in Eastern Dry Zone of Karnataka, India

With the rapid growth of digital wireless communication in recent years, the need for high
speed mobile data transmission has increased. New modulation techniques are being
implemented to keep with the desire more communication capacity. Processing power has
increased to a point where orthogonal frequency division multiplexing (OFDM) has become
feasible and economical. Since many wireless communication systems being developed use
OFDM, it is a worthwhile research topic. Some examples of applications using OFDM
include Digital subscriber line (DSL), Digital Audio Broadcasting (DAB), High definition
television (HDTV) broadcasting, IEEE 802.11 (wireless networking standard).OFDM is a
strong candidate and has been suggested or standardized in high speed communication
systems.
This thesis analyzes the factor that affects the OFDM performance. The performance
of OFDM was assessed by using computer simulations performed using Matlab.it was
simulated under Additive white Gaussian noise (AWGN) channel conditions for different
modulation schemes like binary phase shift keying (BPSK), Quadrature phase shift keying
(QPSK), 16-Quadrature amplitude modulation (16-QAM), 64-Quadrature amplitude
modulation (64-QAM) which are used in wireless LAN for achieving high data rates.
One key component in OFDM based systems is inverse fast Fourier transform/fast
Fourier transform (IFFT/FFT) computation, which performs the efficient
modulation/demodulation. This block consumes large resources in terms of computational
power.this thesis analyzes, different IFFT/FFT implementation on performance of OFDM
communication system. Here 64-point IFFT/ FFT is used. FFT is a complex function whose
computational accuracy, hardware size and processing speed depend on the type of arithmetic
format used to implement it. Due to non-linearity of FFT its computational accuracy is not
easy to calculate theoretically. The simulation carried out here, measure the effects of fixed
point FFT on the performance of OFDM. Comparison has been made between bit error rate
of OFDM using fixed point IFFT/FFT and a floating point IFFT/FFT. Simulation tests were
made for different integer part lengths, fractional part lengths by limiting the input word
lengths to 16 bits and found the suitable combination of integer part lengths and fractional
part lengths which can achieve the best bit error rate (BER) performance with respect to
floating point performance. Extensive computer simulations show that fixed point
computation provides very near result as floating point if the delay parameter is suitably
selected.

Effects of Fixed Point FFT Implementation of Wireless LAN

In this paper, the architecture of a 64-point FFT for the OFDM technique used in WLAN standards is proposed. FFT is a complex function whose computational accuracy, hardware size and processing speed depends on the type of arithmetic format used to implement it. Due to the non-linearity of FFT, its computational accuracy is not easy to calculate theoretically. Therefore statistical or simulation methods are used. A simulation method to calculate the performance (hardware size, computational accuracy) of the FFT, based on fixed-point and floating-point formats, has been used. The paper demonstrates how a simple 64-point FFT, based on the fixed point arithmetic format has a performance comparable to that of a complex floating point arithmetic format. Comparison has been made between a fixed point FFT simulation model and a floating point reference model. The results deduced from comparison have shown that both the approaches provide similar results. However, use of simple FFT model greatly reduces the size of the hardware to be used to implement the OFDM technique

A. Q. Mir

Papers

Performance analysis of a 64-point FFT/IFFT block designed for OFDM technique used in WLANs

Leaf moisture status of some mulberry genotypes as influenced by their foliar anatomy.