Turbo equalization improves communication system performance by iteratively exchanging information between soft-input soft-output (SISO) equalizer and SISO channel decoder. The trellis-based maximum a posteriori probability (MAP) algorithm serves as the optimum SISO equalizer for turbo equalization. However, MAP algorithm is unsuitable for systems with large modulation constellation size and severe inter-symbol interference (ISI) due to its prohibitively high computational complexity. In this paper, an improved SISO block decision feedback equalizer (BDFE) is proposed for low complexity turbo equalization. Unlike other sub-optimum equalizers which perform symbol by symbol detection, the proposed equalizer generates the soft output for each data bit by collecting information from a sequence of samples as in MAP algorithm. The sequence-based equalization is enabled by using not only soft a priori input from channel decoder, but also hard a priori information obtained from BDFE in previous iteration. The combination of soft a priori information and hard a priori information renders better performance with less iterations compared to other sub-optimum algorithms. In addition, the computational complexity of the proposed algorithm is on the same order as conventional SISO BDFE algorithm, and is much lower compared to the trellis-based MAP algorithm.
J. Wu et al., "Improved BDFE Using a Priori Information for Turbo Equalization," IEEE Transactions on Wireless Communications, Institute of Electrical and Electronics Engineers (IEEE), Jan 2008.
The definitive version is available at https://doi.org/10.1109/TWC.2008.060463
Electrical and Computer Engineering
National Science Foundation (U.S.)
United States. Office of Naval Research
Keywords and Phrases
Block Decision Feedback Equalization; Iterative Equalization; Sequence Detection; Turbo Equalization
Article - Journal
© 2008 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.