Novel multi-level magnetic recording using modern error correction.

It has been shown that multilevel techniques operate closer to the channel capacity than binary for a bandwidth limited channel experiencing Additive White Gaussian Noise (AWGN) at increased Signal to Noise Ratio (SNR) [1]. Previous work[2] suggested that multi-level techniques, offered little, if any improvement of the magnetic recording capacity compared to the binary(two-level) system, and is eventually limited by amplitude irregularities in the magnetic channel. This paper looks at a new approach of applying powerful Error Correction Codes (ECC) on the multi-level magnetic recording channel and investigating the improvement in the performance. The main idea behind multilevel recording is to enable storing of more information bits per transition on the magnetic medium. Several magnetisation levels could be used with the multi-level channel. It is known that at higher code rates for AWGN channels, binary codes tend to deviate very quickly from their theoretical performance[1]. In order to achieve very low error-rates at a particular SNR, it is necessary to use state of the art ECC like Turbo Codes. This paper examines the use of multilevel data in conjunction with Turbo codes, for a high density magnetic recording channel, to achieve increased channel capacity for a particular SNR in the operating region of the magnetic recording devices