A 60-Mode High-Throughput Parallel-Processing FFT Processor for 5G/4G Applications

This article presents a 60-mode high-throughput parallel-processing memory-based fast Fourier transform (FFT) processor for fifth-generation (5G)/4G applications. The proposed architecture adopts a multi-FFT parallel-processing scheme to significantly reduce the idle computation cycles of small point FFT due to the deep pipeline. The proposed scheme can narrow the throughput gap between different FFT sizes. In conjunction with the parallel processing scheme, a configurable 16-parallelism butterfly unit is proposed to support a maximum of five radix-3, four radix-4, three radix-5, two radix-8, or one radix-9 operation in one cycle. Furthermore, this article demonstrates conflict-free memory access with a parallel method based on fusion shift combined with a hopping-based method to simplify the data arrangement at different radix stages. According to the orthogonal frequency division multiplexing (OFDM) application characteristics, our processor is extended to support many additional commonly used functions, such as zero padding, cyclic prefix insertion, and 7.5-kHz frequency shift, which can simplify the system call in 5G/4G applications. The FFT processor has been successfully integrated into a small-cell base station baseband system-on-chip (SoC) and taped out at the TSMC 12-nm technology. The implementation result reveals that the die area of the proposed processor is 0.374 mm2 with a power consumption of 235.5 mW at 1 GHz, and the processor supports a balanced throughput up to 3.92 GS/s at all 60-mode, which is better than that of the state-of-the-art (SOTA) designs.