Robust soft decision metrics for a turbo decoder in a partial band jammer environment

This paper proposes a robust soft decision metric generation technique for a turbo decoder, operating in a frequency hopping spread spectrum (FHSS) system under partial band jamming conditions. The technique is based on the probability density function (pdf ) of the SNR estimator and can be implemented using a standard off-the-shelf turbo decoder. For comparison purposes we evaluate the performance of a hard eraser algorithm and a receiver with perfect knowledge of channel parameters. Results indicate that a hard eraser method yields almost optimal results under strong jamming conditions while collapsing in weak jamming conditions. Our robust soft decision metric generation technique facilitates operation under both strong and weak jamming conditions and approaches the performance of a receiver with perfect knowledge of channel parameters by 1.5 dB.