In space, radiation particles can introduce temporary or permanent errors in memory systems. To protect against potential memory faults, either thick shielding or error correcting codes (ECC) are used. Thick shielding translates into increased mass and conventional ECCs designed for memories are typically capable of only correcting a single error and detecting a double error. Decoding is usually performed through hard-decisions where bits are treated as either correct or flipped in polarity. In this work, we demonstrate that low-density parity-check (LDPC) codes that are already prevalent in many communication applications can also be used to protect memories in space. We develop a channel that models memory error events in a space radiation environment. We describe how to compute soft symbol reliabilities on our channel and compare the performance of soft-decision decoding LDPC codes against conventional hard-decision decoding of Reed-Solomon (RS) codes and Bose-Chaudhuri-Hoquenghem (BCH) codes for a specific memory structure.

In this work, a new analytical approach is used to evaluate the error performance of bit-patterned media (BPM) magnetic recording channels that employ one-dimensional (1D) and two-dimensional (2D) generalized partial response (GPR) equalizers to combat the significant inter-track interference (ITI) expected in BPM magnetic recording systems. The probability density function of ITI is obtained analytically and is used to estimate the bit error rate (BER) from the Viterbi detector. The proposed method takes into account most of the important factors affecting the BER such as ITI, un-equalized intersymbol interference (ISI), colored noise and the distance and the multiplicity of error events. In this work, it is shown that for 1D channels, modeling ITI and un-equalized ISI by Gaussian PDFs leads to inaccurate BERs and that the non-Gaussian distribution of the ITI and un-equalized ISI must be taken into account for more accurate BER estimates. This method provides fast and accurate estimates of BERs for moderate to high signal-to-noise ratios (SNRs). By using this analytical method, time-consuming numerical simulations for error performance evaluation can be avoided.

Concatenations of inner low-density parity-check (LDPC) codes and outer Reed-Solomon (RS) codes were evaluated in magnetic recording channel models by simulations using field programmable gate arrays (FPGAs). Fixed inner LDPC codes were used and the optimal code rates for the outer RS code were obtained. It is observed that the outer RS codes do not always improve sector error rates for a fixed user bit density. The effect of various parameters on the sector error rates was evaluated and discussed.

An analytical method to identify lists of the most probable error events for arbitrary partial response (PR) targets is described. The dominant error events are extracted via a computer search considering not only the minimum distance but also additive white noise amplification and data-dependent transition jitter noise. The method uses an efficient scheme to take into account the effect of data-dependent transition jitter noise. Combining the error event analysis and a multinomial model, approximate sector error rates can be calculated without the need for time-consuming simulations. The results from the analytical method are compared with simulation results.