Non-binary error correcting codes with noiseless feedback, localized errors, or both

The two models described in this paper having as ingredients feedback resp. localized errors give possibilities for code constructions not available in the standard model of error correction and also for probabilistic channel models. For the feedback model we present here a coding scheme, which we call the rubber method, because it is based on erasing letters. It is the first scheme achieving the capacity curve for q ges 3. It could be discovered only in the g-ary case for q ges 3, because the letter zero is not used as an information symbol, but solely for error correction. However an extension of the method from using single zeros to blocks of zeros also gives Berlekamp´s result - by a different scheme. In the model with feedback and localized errors the help of feedback is addressed. We give an optimal construction for one-error correcting codes with feedback and localized errors