Combined ECC/RLL codes

Two novel combined error-correcting/run-length-limited (ECC/RLL) trellis codes are presented. One is a two-state (1,3) code with a Hamming distance 4, and the other is a four-state (2,6) code with a hamming distance 3. Each of these codes is decoded by a Viterbi decoder. A second coding scheme is discussed that uses a long constraint convolutional ECC code and a standard RLL modulation code. A single sequential decoder decides both codes by finding the best path through a single tree which describes both of them. Two RLL codes were utilized: a Miller (1,3) code and a (2,7) sliding block code. A comparison of the performance of these competing schemes shows that the code with sequential decoding, while requiring a much more complex decoder, far outperforms the simpler trellis codes, due to the long constraint length of the code used for sequential decoding