Systematic proximity-detecting codes

This paper defines t-proximity-detecting (t-PD) codes that can detect when a received word is within distance t from the transmitted codeword, when using a four-phase asynchronous communication protocol (or other similar protocols). Proximity-detecting codes can be used to improve the performance of asynchronous buses. A nontrivial t-proximity-detecting code must be unordered. However, not all unordered codes are t-proximity-detecting. This paper characterizes t-PD codes, and presents some properties of such codes. Designs of systematic 1-PD codes, and their generalization to t-PD codes are presented, along with a bound on the number of checkbits.