Architectural Synthesis of Computational Engines for Subband Adaptive Filtering

  • Authors:
  • S. Ramanathan;V. Visvanathan;S. K. Nandy

  • Affiliations:
  • Supercomputer Education and Research Centre, Indian Institute of Science, Bangalore - 560 012, India;Supercomputer Education and Research Centre, Indian Institute of Science, Bangalore - 560 012, India;Supercomputer Education and Research Centre, Indian Institute of Science, Bangalore - 560 012, India

  • Venue:
  • Journal of VLSI Signal Processing Systems
  • Year:
  • 1999

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Abstract

Architectural synthesis of low-power computational engines (hardware accelerators) for a subband-based adaptive filtering algorithm is presented. The full-band least mean square (LMS)adaptive filtering algorithm, widely used in various applications, is confronted by two problems, viz., slow convergence when the inputcorrelation matrix is ill-conditioned, and increased computational complexity for applications involving use of large adaptive filter orders. Both of these problems can be overcome by the use of a subband-based normalized LMS (NLMS) adaptive filtering algorithm. Since this algorithm is not amenable to pipelining, delayed coefficient adaptation in the NLMS updation is used, which provides the required delays for pipelining. However, the convergence speed of this subband-based delayed NLMS (DNLMS) algorithm degrades with increase inthe adaptation delay. We first present a pipelined subband DNLMS adaptive filtering architecture with minimal adaptation delay for any given sampling rate. The architecture is synthesized by using a number of function preservingtransformations on the signal flow graph (SFG) representation of thesubband DNLMS algorithm. With the use of carry-save arithmetic,the pipelined architecture can support high sampling rateslimited only by the delay of two full adders and a 2-to-1multiplexer. We then extend this synthesis methodology to synthesize a pipelined subband DNLMS architecture whose power dissipation meets a specified budget. This low-power architecture exploits the parallelism in the subband DNLMS algorithm to meet the required computationalthroughput. The architecture exhibits a novel tradeoff betweenalgorithmic performance (convergence speed) and powerdissipation. Finally, we incorporate configurability for filter order,sample period, power reduction factor, number of subbands anddecimation/interpolation factor in the low-power architecture,thus resulting in a low-power subband computational engine for adaptivefiltering.