MDC Based FFT-IFFT Processor for WiMax and 3GPP LTE Systems

MDC Based FFT-IFFT Processor for WiMax and 3GPP LTE Systems
Authors:R.BHANU PRAKASH, G.SRINIVASULU

Abstract: The IFFT/FFT algorithms are the prior choice for many real time processing systems due to their execution speed, flexibility and precision. The FFT/IFFT processor is widely used in various areas such as 3GPP LTE communications, speech and image processing, medical electronics and seismic processing, etc Specifically, in the modern technologies like WiMax and 4G communication systems (OFDM), FFT and inverse FFT play a very important role. Applications based on FFT such as signal and image processing require high computational power, plus the ability to choose the algorithm and architecture to implement it. Proposed method considerably decreases the chip area because the memory requirement usually dominates the chip area in an FFT/IFFT processor, by using the proposed memory scheduling, MDC architecture is proved suitable for FFT/IFFT processors in WiMax and LTE systems, because the butterflies and multipliers are capable of achieving a 100% utilization rate, meanwhile, the characteristics of simple control provided by MDC is maintained in the proposed design using Verilog language in Xilinx software.. This processor can be used in IEEE 802.16 WiMAX and 3GPP LTE applications. The processor was implemented with an UMC 90-nm CMOS technology. 

Keywords: Fast Fourier Transform (FFT), Memory Scheduling, WiMAX, 3GPP LTE.

INTRODUCTION 

        Modern communication technologies IEEE 802.16 WiMax and LTE systems(4G) are capable of very high range of data transmission and reception. ie in terms of MBps and GBps. To process these range of data the demand for long length, high-speed and low-power FFT has increased. OFDM systems are used in these systems to transmit data with higher data rate and avoid Inter Symbol Interference (ISI). In an OFDM communication system, the broadband is partitioned into many orthogonal sub-carriers, in which data is transmitted in a parallel fashion, thus the data rate for each sub-carrier is lowered by a factor of N in a system with N sub-carriers. By this method, the channel is divided into many narrowband flat fading sub-channels. This makes the OFDM system more resistant to the multipath frequency selective fading than the single carrier communication system. The sub-carriers are totally independent and orthogonal to each other. The sub-carriers are placed exactly at the nulls in the modulation spectral of one another. The OFDM transmitter and receiver contain Inverse Fast Fourier Transform (IFFT) and Fast Fourier Transform (FFT), respectively.

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