Iterative Multihead Multitrack Detection Scheme for Bit-Patterned Media Recording

An iterative multihead multitrack detection scheme for bit-patterned media recording is described in this letter. The scheme employs two iterative strategies with multihead, multitrack detection where three tracks are simultaneously processed to accurately estimate the channel with track misregistration (TMR) and effectively detect the data by using intertrack interference ( ITI ) information with high reliability. The first outer iteration aims to compensate for the TMR effect, and the second inner iteration aims to improve the reliability of the data. In the outer iteration, the TMR effect is compensated by modifying the generalized partial response (GPR) target to a channel that reflects the TMR estimated by a TMR estimator using an expectation and maximization algorithm. In the inner iteration, iterative equalization and decoding (IED) is conducted between the two-dimensional partial response maximum-likelihood detector and the low-density parity check decoder based on the revised GPR target. Since each track has a different channel performance according to the amount of ITI information in the multitrack detection, we design the GPR target and the code rate separately for each track to maximize the overall channel performance. The bit error rate performances of the proposed IED scheme are compared with the conventional IED scheme when the areal density is 2 $\text{Tb/in}^{2}$ . Simulation results show that the IED scheme has more than 2 dB gain compared with the conventional IED scheme for 30 $\%$ TMR.