An efficient parallelization technique for high throughput FFT-ASIPs

Fast Fourier transformation (FFT) and its inverse (IFFT) are used in orthogonal frequency division multiplexing (OFDM) systems for data (de)modulation. The transformations are the kernel tasks in an OFDM implementation, and are the most processing-intensive ones. Recent trends in the electronic consumer market require OFDM implementations to be flexible, making a trade-off between area, energy-efficiency, flexibility and timing a necessity. This has spurred the development of application-specific instruction-set processors (ASIPs) for FFT processing. Parallelization is an architectural parameter that significantly influence design goals. This paper presents an analysis of the efficiency of parallelization techniques for an FFT-ASIP. It is shown that existing techniques are inefficient for high throughput applications such as ultra wideband (UWB), because of memory bottlenecks. Therefore, an interleaved execution technique which exploits temporal parallelism is proposed. With this technique, it is possible to meet the throughput requirement of UWB (409.6 Msamples/s) with only 4 non-trivial butterfly units for an ASIP that runs at 400MHz