VLSI Design of a Variable-Length FFT/IFFT Processor for OFDM-Based Communication Systems

Abstract

The technique of {orthogonal frequency division multiplexing (OFDM)} is famous for its robustness against frequency-selective fading channel. This technique has been widely used in many wired and wireless communication systems. In general, the {fast Fourier transform (FFT)} and {inverse FFT (IFFT)} operations are used as the modulation/demodulation kernel in the OFDM systems, and the sizes of FFT/IFFT operations are varied in different applications of OFDM systems. In this paper, we design and implement a variable-length prototype FFT/IFFT processor to cover different specifications of OFDM applications. The cached-memory FFT architecture is our suggested VLSI system architecture to design the prototype FFT/IFFT processor for the consideration of low-power consumption. We also implement the twiddle factor butterfly {processing element (PE)} based on the {{coordinate} rotation digital computer (CORDIC)} algorithm, which avoids the use of conventional multiplication-and-accumulation unit, but evaluates the trigonometric functions using only add-and-shift operations. Finally, we implement a variable-length prototype FFT/IFFT processor with TSMC 0.35 μm 1P4M CMOS technology. The simulations results show that the chip can perform (64-2048)-point FFT/IFFT operations up to 80 MHz operating frequency which can meet the speed requirement of most OFDM standards such as WLAN, ADSL, VDSL (256∼2K), DAB, and 2K-mode DVB

Diseño y construcción de un prototipo para la medición de distorsión armónica en redes eléctricas

“…W el factor de giro. k constante multiplicativa Sabiendo que la cantidad de datos N es par potencia de 2, se empieza a descomponer la sumatoria, dividiéndola en 2 de la siguiente manera, ecuación (2): asi tomar los 1024 datos en un periodo de la señal que corresponde a 16,66 mili segundos, a su vez, estos datos se van almacenando en un arreglo previamente declarado en la memoria ROM (memoria de solo lectura no volátil) del microcontrolador [5], [6].…”

Fast Fourier Transform Processors: Implementing FFT and IFFT Cores for OFDM Communication Systems

“…The power consumption in Table 6 where P is the power consumption with a voltage of V DD and working at f clk . By slightly modifying the expression given by (Kuo et al, 2003) as follows,…”

“…Proposals such as (Chang & Park, 2004;Serrá et al, 2004) employed a monoprocessor architecture to process the FFT. (Jiang et al, 2004;Lin, Liu & Lee, 2004) used parallel architectures and (Kuo et al, 2003) chose a cached memory monoprocessor architecture for the FFT processing in an OFDM system. However, the most widely used architectures for the FFT/IFFT processor in an OFDM system are pipeline architectures.…”

“…(Jung et al, 2005) 64 Pipeline-MDC r-2 DIT WLAN (Maharatna et al, 2004) 64 Pipeline r-2 DIT WLAN (Serrá et al, 2004) 64 Monoprocessor r-2 DIT WLAN (Lin et al, 2005) 128 Pipeline-MRMDF MR 2/2 3 DIF UWB (Saberinia, 2006) 128 Pipeline-BRMDC r-2 DIF UWB (Lee et al, 2006) 128 Pipeline-SDF r-2 4 DIF UWB (Liu et al, 2007) 64/128 Pipeline 8-path DF MR DIF UWB (Cortés et al, 2007) 128 Pipeline r-2 4 DIF UWB (Bidet et al, 1995) 8192 Pipeline-SDC r-4/2 DIF DVB-T (Lin, Liu & Lee, 2004) 8192 Parallel r-2 3 DIT DVB-T (Wang et al, 2005) 2/8 K Pipeline-SDF r-4/2 DIF DVB-T ( Lenart & Owal, 2006) 2/4/8 K Pipeline-SDF r-2 2 DIF DVB-T/H (Lee & Park, 2007) 8K Pipeline-SDF BD DVB-T (He & Torkelson, 1998) 1024 Pipeline-SDF r-2 2 DIF OFDM (Kuo et al, 2003) 64-2048 Cached memory r-2 DIT OFDM (Chang & Park, 2004) 1024 Monoprocessor r-4 DIF OFDM (Jiang et al, 2004) 64 Parallel r-2 DIT OFDM (Lin, Lin, Chen & Chang, 2004) 64 Pipeline r-2 DIF MIMO (Rudagi et al, 2010) 64 Pipeline r-2 DIT OFDM (Yu et al, 2011) 64 Pipeline r-2 DIF OFDM (Tsai et al, 2011) 64 Pipeline MR OFDM (Turrillas et al, 2010) 32 K Pipeline r-2 k DIF DVB-T2 Table 1. FFT proposals for OFDM systems…”

“…Thus, (Chang & Park, 2004;Cortés et al, 2007;He & Torkelson, 1998;Jiang et al, 2004;Jung et al, 2005;Kuo et al, 2003;Lee et al, 2006;Lin, Lin, Chen & Chang, 2004;Lin et al, 2005;Liu et al, 2007;Maharatna et al, 2004;Saberinia, 2006;Serrá et al, 2004) proposed fixed-point FFTs for N < 8192. Nevertheless, (Wang et al, 2005) also used the fixed-point format for large FFTs.…”