DC-FREE RUN-LENGTH-LIMITED CODES FOR MAGNETIC RECORDING

In this paper, a method to design high-efficiency codes with combined run-length and de-null constraints is presented. Using the new method, two new dc-free (1, 7) codes, with rates of 12/20 and 16/26, were dev eloped. The code efficiencies are 89.31 and 91.6%, respectively. The p roposed approach is more general than the technique used to design the existing dc-free d = 1 code. The performances of the new codes are al so compared with that of the rate 8/10 dc-free (0, 4) code. The minimu m distance analysis and the bit error rate simulation both show that w hile at low densities the proposed codes exhibit performance degradati on compared to the higher rate (0, 4) code, they perform better than t he latter as density increases, despite the code rate disadvantage.