Frame synchronization for PPM-encoded longitudinal position words in magnetic tape storage

Abstract

Frame synchronization is studied for pulse-position modulation-encoded longitudinal position (LPOS) words that are embedded in servo patterns written on tape. After introducing soft-output detection of LPOS symbols, the problem of LPOS frame synchronization using soft outputs from the LPOS detector is considered. An efficient LPOS framesynchronization algorithm that is robust in the presence of transition noise found in magnetic recording channels is then proposed. Finally, the performance of hard-decision LPOS frame synchronization is compared by simulations with that of the proposed soft-decision algorithm, and a hardware implementation of the overall scheme is illustrated.