Soft-in soft-out Reed-Solomon decoding using critically subsampled filterbanks

In the last decade, there has been a growing interest in soft decoding techniques. These techniques are used in the context of concatenated codes, with Turbo codes as the main example, but are almost never applied to existing classical codes. In this paper, the family of Reed-Solomon codes is considered and the complexity problem of Soft-In Soft-Out RS decoding is tackled by breaking RS codes into several smaller subcodes. The decomposition, presented here, is based on filterbanks with one subcode in each subband. The critical subsampling is then crucial if the filterbank is going to be used in a soft decoding setup. This paper focuses on the construction of such filterbanks, starting from non-critically subsampled filterbanks and evolving to a critically subsampled filterbank.