Refinements of Multi-Track Viterbi Bit-Detection

Abstract

In optical storage, data can be arranged on the disc in a meta-spiral consisting of a large number of bit-rows with a small track-pitch. Successive revolutions of the meta-spiral are separated by a narrow guard band. For high storage densities, such a system results in severe 2-D inter-symbol interference. In the multi-track Viterbi algorithm (MVA) of Krishnamoorthi and Weeks, the complex problem of 2-D bit-detection is broken down into a number of smaller bit-detection problems on sets of adjacent bit-rows called stripes. We improve the bit error rate (bER) performance of such a 2-D bit-detector via a number of measures such as: 1) weighing of the separate contributions to the branch metrics from each bit-row in a stripe and 2) inclusion of an additional contribution to the branch metrics from a bit-row adjacent to a stripe. In addition, we reduce the computational complexity by varying the number of bit-rows per stripe during successive iterations of the MVA, and through the use of local sequence feedback.