Abstract
In this dissertation, three new DC free coding schemes are presented.
The first is inspired by the balancing scheme by Knuth, as well as the work by
Frontana, Jamieson and Fair. It is a multi-mode, low-disparity scheme, that controls
the running digital sum (RDS) of a sequence by creating an inversion point, indicated
by a number of redundant prefix bits. The number of prefix bits can be varied in the
design of a specific scheme, allowing the designer to trade code rate for DC suppression
performance.
The second scheme uses the same concepts, applied to run-length limited (RLL)
sequences. The new scheme inserts a fixed-length, inverting marker at a point in each
codeword such that the overall sequence’s RDS is minimised.
The third coding scheme is a variable-length scheme applied to run-length limited
sequences. It inserts special marker runs, of a reserved run-length, whenever the RDS
exceeds a threshold value. A Markov chain model is presented, allowing the code
rate and RDS variance to be accurately predicted when encoding maxentropic RLL
sequences. A lower RDS variance reflects better DC-suppression performance.
M.Ing. (Electrical Engineering)