Graph-Based Channel Detection for Multitrack Recording Channels
1 Qualcomm Inc., San Diego, CA 92121, USA
2 Electrical Engineering Department, Ira A. Fulton School of Engineering, Arizona State University, Tempe, AZ 85287-5706, USA
3 Seagate Technology, Pittsburgh, PA 15222-4215, USA
EURASIP Journal on Advances in Signal Processing 2008, 2008:738281 doi:10.1155/2008/738281Published: 20 January 2009
We propose a low complexity detection technique for multihead multitrack recording systems. By exploiting sparseness of two-dimensional partial response (PR) channels, we develop an algorithm which performs belief propagation (BP) over corresponding factor graphs. We consider the BP-based detector not only for partial response channels but also for more practical conventional media and bit-patterned media storage systems, with and without media noise. Compared to the maximum likelihood detector which has a prohibitively high complexity that is exponential with both the number of tracks and the number of intersymbol interference (ISI) taps, the proposed detector has a much lower complexity and a fast parallel structure. For the multitrack recording systems with PR equalization, the price is a small performance penalty (less than one dB if the intertrack interference (ITI) is not too high). Furthermore, since the algorithm is soft-input soft-output in nature, turbo equalization can be employed if there is an outer code. We show that a few turbo equalization iterations can provide significant performance improvement even when the ITI level is high.