A high rate matched spectral null code

A new method to construct a sliding-block matched spectral null (MSN) code with a high code rate above 0.8 for the partial response class IV (PR4) channel is described. The method partially prunes a running digital sum (RDS) trellis in a novel manner, and is approximately 1.5 times as efficient in generating available codewords compared to a conventional RDS pruning method when their digital sum variations (DSV) are the same. Simulated results with Lorentzian channels showed that practical codes with rates of 12/14 and 24/27 constructed using this method had coding gains of approximately 1 dB and 1.5 dB, respectively, in their signal-to-noise ratio (SNR) compared with the conventional code with a rate of 12/15 at a user bit density of 2.