Runlength constrained recording codes with ancillary channels

Coding schemes with runlength constraints (d,k)=(1,2), (1,4), (2,3), and (2,4) are presented. These coding schemes incorporate a low-rate asynchronous ancillary channel for better utilization of the capacity of the (d,k ) input-restricted channel. Error propagation and error-probability behavior was investigated by simulation. Decoding of the ancillary channel was done by simple sliding window decoders. With these decoders, neither the rate nor the error performance of the main channel was impaired by the ancillary channel