A variable-redundancy hybrid ARQ scheme using invertible convolutional codes

Nonstationary channels (e.g., digital mobile communication channels) require adaptive error control schemes for reliable communication. On these channels, a particular transmission may encounter no errors. Hence, it is desirable to split an encoded sequence into subsequences that are sent in successive transmissions such that each subsequence contains all the information necessary to recover the original message in case of no errors. When errors are present, the subsequences are combined to perform error correction. We show that invertible convolutional codes have this property, and can be used to provide incremental redundancy in a variable-redundancy hybrid ARQ (VR-HARQ) scheme. Invertible convolutional codes provide an alternative to polynomial division otherwise required to extract the original message in convolutional VR-HARQ schemes.< >