Frame Synchronization for PPM-Encoded Longitudinal Position Words in Magnetic Tape Storage

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 frame-synchronization 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.