Y. Savaria

Bio: Y. Savaria is an academic researcher. The author has contributed to research in topics: Split-radix FFT algorithm & Twiddle factor. The author has an hindex of 1, co-authored 1 publications receiving 6 citations.

A new memory reference reduction method for FFT implementation on DSP

Abstract: Memory reference in digital signal processors (DSP) is among the most costly operations due to its long latency and substantial power consumption. In this paper, we present a new method to minimize memory references due to twiddle factors for implementing any existing fast Fourier transform (FFT) algorithms on DSP processors. The new method takes advantage of previously proposed twiddle factor reduction method (TFRM) and twiddle-factor-based butterfly grouping method (TFBBGM). It can compute two butterflies in one stage of any FFT diagram by loading only one twiddle-factor. Further memory reference reduction is done by computing butterflies with the same twiddle factor at the same time in different stages of the FFT diagram. We have applied the new method to implement radix-2 DIT FFT algorithm on TI TMS320C64x DSP. While using only 50% memory space for storing twiddle factors compared to the conventional DIT FFT implementation, the new method achieves an average reduction in the number of memory references by 79% for accessing the twiddle factors, and 17.5% reduction in the number of clock cycles.

Improved radix-4 and radix-8 FFT algorithms

Abstract: In this paper, improved algorithms for radix-4 and radix-8 FFT are presented. This is achieved by re-indexing a subset of the output samples resulting from the conventional decompositions in the radix-4 and radix-8 FFT algorithms. These modified radix-4 and radix-8 algorithms provide savings of more than 33% and 42% respectively in the number of twiddle factor evaluations or accesses to the lookup table compared to the corresponding conventional FFT algorithms without imposing any additional complexity.

An improved radix-16 FFT algorithm

Abstract: An improved radix-16 decimation-in-frequency (DIF) FFT algorithm is proposed by introducing new indices for some of the output sub-sequences resulting from the conventional radix-16 DIF decomposition of the DFT. This improved radix-16 DIF FFT algorithm achieves savings of more than 46% in the number of twiddle factor evaluations or accesses to the lookup table and address generations compared to the conventional radix-16 DIF FFT algorithm. These savings are achieved without imposing any additional computational or structural complexity in the algorithm.

Development & Implementation of Visual Approach and Parallel Distributed Architecture for 2-D DFT & UMRT computation

Abstract: i ACKNOWLEDGEMENTS iii SYMBOLS AND DEFINITIONS v LIST OF TABLES vii TABLE OF FIGURES ix TABLE OF CONTENTS xi CHAPTER 1.............................................................................................................................

Code Acquisition in Direct Sequence Spread Spectrum Communication Systems Using an Approximate Fast Fourier Transform

Abstract: This paper deals with code acquisition in communication systems with large frequency offsets. In such a situation, the receiver has to perform a 2-dimensional search in a time-frequency plane to detect a known signal. In previous publications it has been proposed to use a fast Fourier transform (FFT) to implement the search in frequency direction [1], [2], [3]. We would here like to examine the effect of using approximate FFTs. For this puropose, we restrict the angles of the complex multiplications that are used in the FFT to four or eight states. This helps to reduce the total number of real multiplications. Further, there is no need to store trigonometric values. The drawback is that the approximations lead to a degradation at the FFT output. We will show, however, that in a two-stage acquisition scheme, where the FFT is only used to obtain an estimate of the frequency offset, approximate FFTs achieve almost the same performance as a conventional FFT.

Improved Latency for Time Critical OFDM Based Systems in Vehicular Environment

Abstract: Increasing interest in mobile communication systems with high data rates and low complexity, demands heavily for an extensive research on communication techniques and their optimal implementation. The Orthogonal Frequency Division Multiplexing (OFDM) scheme has been quite extensively used in many communication standards. A hardware implementation of an OFDM based system faces more challenges with respect to the latency in the digital signal processing chain especially when used in the vehicular environment. A reduction in the latency thus becomes quite useful since the signal processing time should be as less as possible due to a quite restricted time for communication setup in the vehicular area, e.g. IEEE 802.11a/g, IEEE802.11p. The paper proposes a method to reduce the latency in such OFDM based systems by effectively combining the interleaving and a part of lFFT.