Study of Modulation and Error Control Coding in Thick Film Digital Magnetic Recording

Abstract

This thesis is concerned with the application of Modulation and Error Correction codes to Digitally Recorded Magnetic Data.The effects of these coding schemes were measured against bitshift errors which are induced by different Non Clockloss Error Mechanisms. These Error mechanisms are Noise and Inter Symbol Interference, ISI. The Thesis has an extensive literature survey which can be divided into four main areas: Error Control Coding, Modulation Codes, Recording Techniques and the Recording Process.The theoretical and experimental results involving the Non Clockloss Error Mechanisms and their effect on the data, were derived by Monte Carlo computer simulation. Four channel models were used, for uncorrelated noise, correlatednoise and the convolution of these with ISI. The model for ISI was developed assuming a symmetrical replay pulse for two separate types of modulation coding. Two different Error correcting codes were used, these are the linear BCH code and the Non-Linear Reed Solomon Code.The results of this thesis conclude that the effects of Tape Noise and ISI are independent pulse to pulse. A strategy was developed for pulse reconstruction for Manchester Modulation code. The phenomenon of bitslip was found to be moreprevalent in fixed pulse rather than fixed rate codes