Fast Fourier Transform for high speed OFDM wireless multimedia system

Future Wireless multimedia systems require higher data rate and robust transmission of information. Orthogonal Frequency Division Multiplexing (OFDM) is being actively considered for the potential candidate for the next generation wireless communication systems. Fast Fourier Transform (FFT) is one of the key building blocks to implement OFDM transceiver systems. Thus its efficient implementation is desirable. In this paper, principles of OFDM are described. FFT computational requirements for this emerging technology for wireless multimedia systems are identified. The corresponding VLSI design options for FFT implementations to meet these requirements are presented. Trade offs between hardware footprint, speed, and power are analyzed. An alternative FFT realization is considered where constant geometry architecture with pipelining and parallel processing is used. In this realization, the architecture of each FFT stage is identical. As a result, the hardware implementation for one stage can be repeatedly used, i.e. the outputs of an FFT stage are fed back to the same hardware. In addition, it is shown that, while a ROM is employed to store the twiddle factors, memory access requirement is eliminated. This approach is promising to meet the high-speed FFT requirements for this application.