[Deshmukh, 2(12): December, 2013] ISSN: 2277-9655 Impact Factor: 1.852 http: // www.ijesrt.com(C)International Journal of Engineering Sciences & Research Technology [3509-3515] IJESRT INTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCH TECHNOLOGY Efficient Implementation of 64-Point FFT/IFFT for OFDM on FPGA Mr. Shreyas D. Deshmukh *1 , Mrs. Deepali Sale 2 *1,2 Lecturer, DYPIET, Pimpri, Pune-18, India shreyasdesh09@gmail.com Abstract Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation technique which divides the available spectrum into many carriers. OFDM uses the spectrum efficiently compared to FDMA. With the rapid growth of digital wireless communication in recent years, the need for high-speed mobile data transmission has increased. FPGAs have become key components in the implementation of high performance DSP systems. The objective of this paper is to design and efficiently implement FFT and IFFT blocks required for a base band OFDM transmitter and receiver on FPGA hardware. IFFT/ FFT blocks are complex to implement and main blocks of OFDM system i.e. it consumes more resources. So, a efficient technique used here in which FFT/IFFT is implemented in such a way that it consumes very less resources. This module of 64-point FFT and IFFT is designed using VHDL programming language. In this work, a pure VHDL design, integrated with some intellectual property (IP) blocks, is employed to implement an OFDM transmitter and receiver. The proposed design is map and test on Xilinx Virtex 5 FPGA and for simulation, synthesis and implementation XILINX ISE 13.1 software is used. Keywords: Orthogonal Frequency Division Multiplexing (OFDM), Field Programmable Gate Array (FPGA), Fast Fourier Transform (FFT), Quadrature Amplitude Modulation (QAM), VHDL (VHSIC Hardware Description Language). Introduction Orthogonal Frequency Division Multiplexing is a special case of multicarrier transmission, where a single data stream is transmitted over a number of lower-rate subcarriers. The main advantage of OFDM is their robustness to channel fading in wireless environment. OFDM can be seen as either a modulation technique or a multiplexing technique. In OFDM, multiplexing is applied to independent signals but these independent signals are the part of one main signal. In OFDM, the signal itself is first split into independent channels, modulated by data and then re-multiplexed to create the OFDM carrier [1]. OFDM is a technique especially suitable for wireless communication due to its resistance to inter- symbol interference (ISI) and inter-carrier interference (ICI). In single carrier system, if signal get fade or interfered then entire link gets failed where as in multicarrier system, only a small percentage of the subcarriers will be affected. FFT/IFFT are the complex and important block of OFDM system, it also requires much of the resources. So its efficient implementation regarding power and resources is must. So in this paper for implementation of FFT, very efficient and innovative technique is proposed by Koushik Maharatna, Eckhard Grass, and Ulrich Jagdhold [2] is used. This paper also gives comparison with other implementation techniques and with available IPs for FFT from various vendors. Basic of OFDM system is discussed in the section II. The concepts like guard band and cyclic prefix are discussed. Also advantages and disadvantages and of OFDM is also discussed in this section. Section III is Implementation of FFT/IFFT modules. In this section, detail description of FFT/IFFT block is given and how to implement these blocks on FPGA is also explained in this section. In Section IV various other ideas regarding efficient implementation of FFT/IFFT such as complex multiplication, number representation is discussed. It also gives the comparison of implemented architecture with various other available IPs. Section V outlines the conclusion. Basic OFDM System In OFDM, each subcarrier has an integer number of cycles within a given time interval, and the number of cycles by which each adjacent subcarrier differs is exactly one, in time domain. Due to this, the spectrum of each carrier has a null at the center frequency of the other carriers in the system, in frequency domain. This property accounts for orthogonality between the