"Joint demodulation and decoding (JDD) can be used to demodulate data transmitted over noisy intersymbol interference (ISI) channels. The main aim of this thesis is to combine a soft-output greedy algorithm (SOGA) which computes the suboptimal estimates of the maximum likelihood (ML) data with outer codes for improving the overall performance of full-surface data-storage devices.
SOGA updates an estimate of user data by searching for the most likely error events in full-surface data. Hence, SOGA allows iterative processing of data estimates. This feature is very important for using the SOGA in JDD schemes. This SOGA provides ML user data estimates and soft outputs which give a measure of reliability of individual bit decisions.
This SOGA is combined with outer codes like simple parity-check code, Hamming codes, and low-density parity-check codes (LDPC) to achieve higher data storage density. The SOGA attempts to minimize the metric of received data according to the ML criterion. But the SOGA gets trapped at local minima that prevent it from finding the ML data. The use of outer codes in JDD schemes pushes the greedy algorithm out of local minima and allows for an overall improvement in bit error rate.
The bit-error rate (BER) performance of JDD is better than that of SOGA without any outer codes. Finally performances of JDD scheme with simple parity- check code, Hamming code, and LDPC codes are compared. It is found that BER performances of JDD with LDPC codes is slightly better than that of JDD with parity-check codes and Hamming codes at high signal to noise ratio (SNR) values. It can also be concluded that performance is better when bits in the same codeword are spaced as far apart as possible"--Abstract, page iii.
Weeks, William IV
Kosbar, Kurt Louis
Morgan, Ilene H.
Electrical and Computer Engineering
M.S. in Electrical Engineering
University of Missouri--Rolla
viii, 40 pages
© 2003 Shivaprasad Kotagiri, All rights reserved.
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Kotagiri, Shivaprasad, "Joint demodulation and decoding for full-surface data" (2003). Masters Theses. 2342.
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