Turbo Codes for Error Correction in Impulsive Noise Environments

T. Faber, T. Scholand, and P. Jung (Germany)

Keywords

Cauchy Distribution, Gaussian Mixture Distribution (GMD), Impulsive Noise, Iterative Processing, Log Likelihood Ratio (LLR), Maximum APosteriori (MAP), Rayleigh Fading, TurboCodes, UMTS

Abstract

In the recent years, iterative (“turbo”) processing techniques with soft-in/soft-out components have received considerable attention. Examples are turbo decoding, turbo equalization, and turbo multi-user detection. The authors shall consider the application of Turbo-Codes to environments with impulsive white noise. Impulsive noise has a non-Gaussian nature and is e.g. found in many wireless channels due to impulsive phenomena of radio-frequency interference and also in power line and in digital subscriber line communication systems. A detector/Turbo decoder concept, derived from turbo equalization, shall be presented. The illustrated concept avoids numerical instabilities. It shall be shown that Turbo-Codes facilitate considerable performance improvements over non-coded systems. Furthermore, for benchmarking reasons, the deployment of a conventional rate 1/2 convolutional code with constraint length 5 and octal generators 238,358 will be taken into account.

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