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Team Collaborators Sponsors Related Publications	There has been a tremendous increase in areal density since the advent of the first magnetic drives. Such an increase was almost always achieved by scaling down the area of a bit by reducing its length and width. But, the magnetic industry has reached a critical point where the particle size can no longer be reduced. In order to achieve storage densities of 1 Tb/in^2 and higher, many novel architectures have been proposed. Two such architectures are heat-assisted magnetic recording (HAMR) and two-dimensional magnetic recording (TDMR).
Software Intranet	Heat-Assisted Magnetic Recording (HAMR) In HAMR system, the magnetic medium is heated before the data is recorded and subsequently cooled to room temperature almost instantaneously. The heating enables bits to be recorded in a smaller area and the instantaneous cooling ensures their stability. In this project, we study, from a read channel perspective, the unique characteristics of the system induced by heating the medium. For example, as shown in the figure, a common observation is that the heating results in the curvature of the magnetic transitions. The study is performed using a sophisticated simulator (C, MPICH) that incorporates a numerical channel model developed in Seagate Research. The simulator is capable of incorporating non-linear impairments in the system like partial erasure and NLTS.
	Two-Dimensional Magnetic Recording (TDMR) TDMR is uniquely different from HAMR and other storage technologies because it relies more on novel signal processing algorithms, including detection and decoding. TDMR attempts to store one bit in very few grains of the magnetic medium with an ultimate goal of storing 1 bit/grain. TDMR can, in principle, achieve the highest possible storage density for a given medium, unless some non-binary magnetic storage techniques are developed in the future. However, formidable challenges need to be addressed before some conclusions on achievable densities can be derived. They arise as a consequence of the fact that the area of a bit in a TDMR system is comparable to the grain area. Since, conventional media are used to store information in TDMR, the grain boundaries are irregular and form the primary source of noise. In addition to irregular boundaries, the random distribution of grains in the medium, along with the high areal density necessitates the need for the information storage process to be viewed as a two-dimensional system. Therefore, there is a need for developing two-dimensional (2D) signal processing algorithms and 2D detectors and codes/decoders. Below is an example of a magnetized medium, where the medium is modeled as a plane partitioned by Voronoi regions.
	Project Members Prof. Bane Vasic Rathnakumar Radhakrishnan Anantha Raman Krishnan Sundararajan Sankaranarayanan Collaborators Dr. Fatih Erden (Seagate) Dr. Kheong Sann Chan (DSI, Singapore) Sponsors Seagate INSIC
	Recent Related Publications Journals ∙ Sann C. K.,Radhakrishnan R., Eason K.,Elidrissi R. M., Miles J.,Vasic B.,Krishnan A. R., Channel models and detectors for two-dimensional magnetic recording (TDMR). [pdf] ∙ Krishnan A., Radhakrishnan R., Vasic B., Kavcic A., Ryan B., Erden F., Two-dimensional magnetic recording: Channel models and detectors, accepted for publication in IEEE Trans. Magn. (Invited). [pdf] ∙ Krishnan A., Radhakrishnan R., Vasic B., Read-channel modeling for two-dimensional magnetic recording, accepted for publication in IEEE Trans. Magn. ∙ Radhakrishnan R., Erden F., He C., Vasic B., Transition response characteristics of heat-assisted magnetic recording (HAMR) system and their performance with maximum transition run (MTR) codes, IEEE Trans. Magn., vol. 43, no. 6, pp. 2298-2300, June 2007. [pdf] ∙ Radhakrishnan R., Vasic B., Erden F., He C., Characterization of Heat-Assisted Magnetic Recording Channels, in ser. DIMACS Series in Discrete Mathematics and Theoretical Computer Science, February 2008, vol. 73, pp. 23-40. [pdf] Conferences ∙ Krishnan A., Radhakrishnan R., Vasic, B., Performance of LDPC codes in two-dimensional magnetic recording systems, submitted to IEEE Global Telecommunications Conference (GLOBECOM), Dec 2009. [pdf] ∙ Krishnan A., Radhakrishnan R., Vasic B., Read-channel modeling for two-dimensional magnetic recording, in Proc. of IEEE International Magnetics Conference (INTERMAG), Sacramento, CA, May 4-8, 2009. ∙ Radhakrishnan R., Vasic B., Joint message-passing symbol-decoding of LDPC codes and partial response channels, in Proc. of IEEE International Conf. on Communications (ICC), Dresden, Germany, June 2009. [pdf] ∙ Radhakrishnan R., Sankaranarayanan S., Vasic B., Analytical performance of one-step majority logic decoding of regular LDPC codes, in Proc. of International Symposium on Information Theory (ISIT), Nice, France, pp. 231-235, June 24-29, 2007. [pdf] ∙ Radhakrishnan R., Erden F., He C., Vasic B., Transition response characteristics of heat-assisted magnetic recording, in Proc. of 10^th joint MMM/Intermag Conference, Baltimore, USA, Jan 7-11, 2007.