2002 Asilomar Conf. on Signals, Systems, and Computers, Nov. 3-6, Pacific Grove, CA

A Real-Time Embedded Software Implementation of a Turbo Encoder and Soft Output Viterbi Algorithm based Turbo Decoder

M. Farooq Sabir, Rashmi Tripathi, Brian L. Evans, and Alan C. Bovik

Department of Electrical and Computer Engineering, Engineering Science Building, The University of Texas at Austin, Austin, TX 78712-1084
mfsabir@ece.utexas.edu - bevans@ece.utexas.edu - bovik@ece.utexas.edu


Turbo codes are used for error protection, esp. in wireless systems. A turbo encoder consists of two recursive systematic convolutional component encoders connected in parallel and separated by a random interleaver. A turbo decoder, which is iterative, is typically based on either a Soft Output Viterbi Algorithm (SOVA) or a maximum a posteri (MAP) algorithm. MAP is roughly three times more computationally complex than SOVA, but provides 0.5 dB of coding gain. In this paper, we implement a turbo encoder and SOVA-based turbo decoder in real-time software on a TMS320C6700 digital signal processor (DSP). The contributions of this paper are:

  1. first publicly available implementation of a SOVA-based turbo decoder on a C6000 DSP,
  2. speedup of 162x for the encoder on a C6200 DSP and 11.7x for the decoder on a C6700 DSP over level three C compiler optimization, and
  3. dataflow modeling for a turbo channel coding subsystem.

COPYRIGHT NOTICE: All the documents on this server have been submitted by their authors to scholarly journals or conferences as indicated, for the purpose of non-commercial dissemination of scientific work. The manuscripts are put on-line to facilitate this purpose. These manuscripts are copyrighted by the authors or the journals in which they were published. You may copy a manuscript for scholarly, non-commercial purposes, such as research or instruction, provided that you agree to respect these copyrights.

Last Updated 12/11/05.