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Research Letters in Communications
Volume 2007, Article ID 53517, 4 pages
Research Letter

Simplified LLRs for the Decoding of Single Parity Check Turbo Product Codes Transmitted Using 16QAM

School of Information Technology and Engineering (SITE), University of Ottawa, Ottawa, Ontario, Canada K1N 6N5

Received 20 August 2007; Accepted 1 October 2007

Academic Editor: Guosen Yue

Copyright © 2007 Maher Arar et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Iterative soft-decision decoding algorithms require channel log-likelihood ratios (LLRs) which, when using 16QAM modulation, require intensive computations to be obtained. Therefore, we derive four simple approximate LLR expressions. When using the maximum a posteriori probability algorithm for decoding single parity check turbo product codes (SPC/TPCs), these LLRs can be simplified even further. We show through computer simulations that the bit-error-rate performance of (8,7)2 and (8,7)3 SPC/TPCs, transmitted using 16QAM and decoded using the maximum a posteriori algorithm with our simplified LLRs, is nearly identical to the one achieved by using the exact LLRs.