A rate 8/9 sliding block trellis code with stationary detector for magnetic recording

A new trellis code for partial-response magnetic recording channels, that eliminates most frequent errors while keeping the code trellis invariant in time, is proposed. Previously published codes either had lower code density or resulted in time varying trellises with a period of 9, thus requiring a higher complexity of detectors. The new code introduces dependency between codewords to achieve the same coding constraints as an 8/9 code, with the same code density, resulting in a trellis that has a period of two. The new trellis code eliminates two states in every second step of the E²PR4 trellis, requiring a 14-state two-step sequence detector