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Coding for informed decoders

We consider coding for a channel producing errors, where a side-channel (not known to the encoder) possibly informs the decoder about a part of the information that is encoded in the transmitted codeword. The objective is to design a code of which the correction power is enhanced if some information symbols are known to the decoder. Such a form of channel coding we call "coding for informed decoders". A possible application is in the field of address retrieval on optical media. The sector address on optical media is part of a header which is protected by an error correcting code. Under many circumstances much of the header information of the current sector can be inferred from the previously read sectors and the table of contents. The application of coding for informed decoders to sector header protection allows for reliable local address retrieval, which is especially important during writing. We describe the general concept, and provide two constructions for coding for informed decoders.