Coding for Transverse-Reads in Domain Wall Memories

Transverse-read is a novel technique to detect the number of '1's stored in domain wall memory, also known as racetrack memory, without shifting any domains. Motivated by this technique, we propose a novel scheme to combine transverse-read and shift-operations such that the number of shift-operations can be reduced while still achieving high capacity. We also show that this scheme is helpful to correct errors in domain wall memory. A set of valid words in this transverse-read channel is called a transverse-read code. We first present several properties of transverse-read codes and show that they are equivalent to constrained codes. Then, we compute the maximal asymptotic rate of transverse-read codes for several parameters. Next, we construct achieving capacity codes with efficient encoding/decoding algorithms. Finally, we discuss transverse-read codes which correct shift-errors in domain wall memory.