MODULATION CODES FOR PRECEDED PARTIAL-RESPONSE CHANNELS

[d, k] Modulation codes for 1/(1 + D-2) preceded PR4 channels (PPR4) a nd 1/(1 + D + D-2 + D-3) preceded EPR4 channels (PEFR4) are proposed i n this paper. They differ from conventional (d, k) constrained codes i n the sense that they provide PPR with a direct control over separatio n between transitions during writing and the number of consecutive zer o-samples during reading. Their Finite State Machines (FSM), which hav e the same Shannon Capacity as their counterparts of (d, k) codes, are constructed. For comparison with the 2/3 (1,7) code, a 2/3 [1, 6] cod e for PPR4 and a 2/3 [1, 5] code for PEPR4 are designed. they have a 5 -state encoder and R-bit decoding window, and an 8-state encoder and 9 -bit decoding window, respectively. Their power spectra are calculated . As an example, error rate performances of (1, 7) PR4ML, (1, 7) PPR4M L, and [1, 6] PPR4ML are simulated under the Lorentzian model with bot h medium and electronic noises at various channel recording density. T he result shows that the [1, 6] PPR4ML outperforms both the (1,7) PR4M L and the (1, 7) PPR4ML consistently. More importantly, the [d, k] pre ceded PR (PPR) prevents error propagation which (1, 7) PR may suffer f rom, and deals with non-linearity more effectively than (1, 7) PPR. Th e technique presented in this paper is applicable to other extended PP R or preceded generalized PR (PGPR).