ABSTRACT
A new coding technique is proposed that translates
user information into a constrained sequence using very long codewords.
Huge error propagation resulting from the use of long
codewords is avoided by reversing the conventional hierarchy
of the error control code and the constrained code.
The new technique is exemplified by focusing on (d,k)-constrained codes.
A storage-effective enumerative encoding scheme is proposed for translating
user data into long dk sequences and vice versa.
For dk runlength-limited codes, estimates are given
of the relationship between coding efficiency versus encoder and decoder
complexity. We will show that for most common d,k values a code rate of less
than 0.5% below channel capacity can be obtained by using hardware
mainly consisting of a ROM look-up table of size 1 kbyte. For selected values
of d and k, the size of the look-up table is much smaller.
The paper is concluded by an illustrative numerical example of a rate
256/466, (d =2, k =15) code, which provides a serviceable 10% increase in
rate with respect to its traditional rate 1/2, (2,7) counterpart.
Key Words: enumerative coding, constrained code, recording code, run-length-limited