Research On Key Technologies Of Hard Disk Read/Write Channel

As high capacity, high stability equipment, hard disks occupy a dominant position in the storage area. Improvement in read/write channels allows the substantial increase in hard disk capacity. Currently relevant research on read/write channels represents on the improvement of coding technique and the simulation of the read/write channel.A permutated concatenated encoding/decoding method is adopted because traditional concatenated encoding method has a deficiency in restraining error propagation. By permuted the order of RS(Reed-Solomon)correction code and RLL (Run Length Limited codes)in concatenated coding, this new coding method can effectively restrain error propagation and thus reducing the bit error rate. Encoding includes encoding user data into the first limited sequences through HRRLL(High-Rate Run Length Limited codes)encoder, bit-expanding to a middle sequences which is used for RS encoder to create parity-check symbols, encoding the parity-check symbols to the second limited sequences through LRRLL(Low-Rate Run Length Limited codes)encoder and finally combining the first and the second limited sequences to a recording sequences. Decoding includes subtracting the first and the second limited sequences from the recording sequences, decoding the second limited sequences through LRRLL decoder and meanwhile bit-expanding the first limited sequences to a middle sequences, combining middle sequences with parity-check symbols in order to decoding the middle sequences through RS decoder, bit-compressing the decoded middle sequences and the result is finally decoded through HRRLL decoder to recover user data.A simulation of read/write channel is established and the design method of all the primary aspects in digital part is especially discussed. Results of the equalization and Viterbi detection are analyzed under the model given different SNR. The system can not only be used as a experiment platform for designing disk read/write channel, but the result of simulation can be taken as theoretical bases for optimizing given read/write channel.