Multiple track performance of a digital magnetic tape system : experimental study and simulation using parallel processing techniques
The primary aim of the magnetic recording industry is to increase storage capacities and transfer rates whilst maintaining or reducing costs. In multiple-track tape systems, as recorded track dimensions decrease, higher precision tape transport mechanisms and dedicated coding circuitry are required. This leads to increased manufacturing costs and a loss of flexibility. This thesis reports on the performance of a low precision low-cost multiple-track tape transport system. Software based techniques to study system performance, and to compensate for the mechanical deficiencies of this system were developed using occam and the transputer. The inherent parallelism of the multiple-track format was exploited by integrating a transputer into the recording channel to perform the signal processing tasks. An innovative model of the recording channel, written exclusively in occam, was developed. The effect of parameters, such as data rate, track dimensions and head misregistration on system performance was determined from the detailed error profile produced. This model may be run on a network of transputers, allowing its speed of execution to be scaled to suit the investigation. These features, combined with its modular flexibility makes it a powerful tool that may be applied to other multiple-track systems, such as digital HDTV. A greater understanding of the effects of mechanical deficiencies on the performance of multiple-track systems was gained from this study. This led to the development of a software based compensation scheme to reduce the effects of Lateral Head Displacement and allow low-cost tape transport mechanisms to be used with narrow, closely spaced tracks, facilitating higher packing densities. The experimental and simulated investigation of system performance, the development of the model and compensation scheme using parallel processing techniques has led to the publication of a paper and two further publications are expected.