Implementation of High Speed MDC FFT/IFFT Processor for MIMO-OFDM Systems

Abstract

ABSTRACT:The architecture of multipath delay commutator (MDC) and memory scheduling are the basic concepts used to implement fast Fourier transform (FFT) processors with variable length. These FFT processors are used in orthogonal frequency division multiplexing systems, having multiple number of inputs and multiple number of outputs. Depending on this MDC architecture, we implement the fft/ifft processor based design which is proposed in this paper. In this design we implement ram, fifo, input buffer and output sorting buffer. The functionality verification and the synthesis is carried out using XILINX ISE 12.3i and shows the reduced delay values. KEYWORDS:Fast Fourier Transform (FFT), memory scheduling, multiple-input and multiple-output (MIMO), orthogonal frequency division multiplexing (OFDM), output sorting, pipeline based multipath delay commutator (MDC), WiMAX. I.INTRODUCTIONWhen we require a data to be encoded at multiple frequencies then the popular scheme generally used is orthogonal frequency division multiplexing. This type of scheme is famous at wideband digital communication. Whether it may be wired or wireless such as television, broadcasting of audio, internet accessing, wireless networks and is widely used in latest technology like 4G mobile communication. Digital multi carrier modulation technique is used for OFDM, When we require to carry parallel streaming of data, a large spaced orthogonal sub-carrier signals are used in which each sub-carrier undergo convolution modulation like quadrature amplitude modulation or phase shift keying. OFDM have capability of channel equalization because it uses slowly modulated narrow band signals instead of using one highly modulated wide band signal. Using OFDM, FFT can be implemented without loss in efficiency. Narrow band co channel interfacing becomes very robust using ofdm .it is very less sensitive over time synchronization errors. These type of OFDM signals have broad range of usage in WLAN under the standard of 802.11a,and digital radio systems standards like DAB/ERUKA 147,Terristial Digital TV systems(DVB-T)and Terrestrial Digital mobile systems(DVB-T) Fast Fourier transform are used to compute discrete Fourier transform and also for its inverse .These technique used to convert to signals from time to frequency domain and vice versa.fft makes numeric algorithm as simple such that it is used in image processing and signal processing applications. In previous DFT is existed ,in which the fastness drawback has overcome by fft.Ofdm uses reverse fft and transmitter side and fft and the receiver side to perform modulation and demodulation efficiently. Fft with ofdm is used cpu like intel Pentium at 1.26GHZ frequency and is able to calculate a 8 192 fft with in 576µs using FFTW, and in cpu called intel Pentium M AT 1.6 GHZ frequency and able to within 387 µs. a compared to earlier generation cpu ,a wide range of fft-ofdm based cpu named intel core 2 duo which operates at3 Ghz frequency and able to perform the operations at 96.MIMO-OFDM defines multi input a...