Runlength violation of weakly constrained code

Guided scrambling (GS) is used to control the runlength within codewords as well as to suppress dc components. A weakly constrained code designed by using a GS technique violates the imposed κ-constraint with low probability, but achieves a code rate close to the channel capacity. In this study, the probability that codewords violate the k-constraint was measured by using convolutional GS and by using Galois-Field (GF)-addition GS. The occurrence probability of each runlength was also computed and then compared to a 24/25(0,8) block code having a high code rate and to the maxentropic runlength limited (RLL) sequence. The comparison shows that codes designed by these GS techniques attain extremely high code efficiency