Intermediate checksums for improving goodput over error-prone links

When a frame transmitted over an error-prone link is hit by bit errors, it is retransmitted entirely, despite the fact that often only a few bits are erroneous. In this paper we propose to not use a single checksum covering all data bits, but multiple checksums covering only parts of a frames data block (a chunk). In case of a retransmission only the chunks with a wrong checksum are retransmitted. We show analytically that for high bit error rates and a time-invariant binary symmetric channel this approach can give significant advantages in terms of goodput over the traditional scheme using only a single checksum per frame. In addition, we propose a simple scheme for adapting the chunk size to the current channel conditions and present first results for this, indicating that for bad channel conditions close-to-optimal goodput is achieved.