A Note on the Shannon Capacity of Runlength-Limited Codes

It is proven that 100-percent efficient fixed-rate codes for runlength-limited (RLL) (d, k) and RLL charge-constrained (d, k; c) channels are possible in only two cases, namely (d,k;c) = (0,1;1) and (1,3;3). Specifically, the binary Shannon capacity of RLL (d, k) constrained systems is shown to be irrational for all values of (d, k),0 ≤ d. < © 1987 IEEE