UPPER-BOUNDS ON ACHIEVABLE STORAGE DENSITY - A 2-DIMENSIONAL APPROACH

This paper compares two upper bounds on achievable storage density in rigid-disk magnetic recording systems, Each upper bound equals the cap acity of a communication channel that models a physical recording syst em, The upper bounds arise by relaxing physical constraints to make th e models tractable, Medium capacity is an upper bound on the density o f information that a magnetic medium can accommodate, It is independen t of the particular method of storage and retrieval, We model the magn etic medium as a two-dimensional waveform channel with additive white Gaussian noise, and we compute medium capacity as the Shannon capacity of this channel, Single-head capacity is an upper bound on the densit y of information that a single-head recording system can reliably stor e and retrieve from the medium, We model the single-head recording pro cess as a one-dimensional waveform channel with linear impulse respons e, correlated Gaussian noise, and cross-talk, We show that for a typic al thin-film system, medium capacity exceeds single-head capacity by m ore than a factor of 40, This result suggests that the use of novel re cording techniques that account for the two-dimensional nature of the medium can achieve significant gains in storage density.