Performance of turbo detection in a variable rate wireless system using linear block codes and interleaving

Linear block coding with an iterative detecting-decoding process, namely, turbo detection, is examined for data transmission within the framework of the HIPERLAN Type 1 standard. By means of simulations, performance is evaluated in Gaussian and frequency selective Rayleigh fading channels and the turbo detection method is shown to offer superior performance when compared to soft-decision algorithms; although its high potential is restricted by the predefined standard, which makes use of a single error-correcting BCH(31, 26) code and a block interleaver of depth 16. In order to improve the performance, we devise an alternative variable coding system, having the same physical layer as HIPERLAN, but with the additional channel coding options of a three error-correcting BCH(31, 16) code, or of a seven error-correcting BCH(31, 6) code. Besides having a modular structure, which adapts easily to different information rates, this approach allows the system to work at lower signal-to-noise ratios (SNRs), ensuring user connectivity under very hostile channel conditions.