Low-Complexity Block Turbo Equalization for OFDM Systems in Time-Varying Channels

• Published in: IEEE transactions on signal processing Vol. 56; no. 11; pp. 5555 - 5566
• Main Authors: Fang, Kun, Rugini, Luca, Leus, Geert
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.11.2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Applied sciences; Banded structure; Bit error rate; Blocking; Channels; Computer science; Computer simulation; Criteria; Degradation; Detection, estimation, filtering, equalization, prediction; Digital video broadcasting; Equalization; Equalizers; Exact sciences and technology; Frequency division multiplexing; Information, signal and communications theory; Intercarrier interference; Intersymbol interference; Mathematics; Miscellaneous; Multiplexing; OFDM; Orthogonal Frequency Division Multiplexing; orthogonal frequency-division multiplexing (OFDM); Signal and communications theory; Signal processing; Signal, noise; Telecommunications and information theory; Time-varying channels; turbo equalization; Turbo equalization; OFDM; intercarrier interference; time-varying channels; Performance evaluation; Estimation error; Time variable channel; Parameter estimation; Bit error rate; Intercarrier interference; Frequency domain method; Iterative method; Equalizer; Equalization; Subcarrier; Algorithm; Implementation; Mean square error; Simulation; Channel estimation; Orthogonal frequency division multiplexing; Signal processing; orthogonal frequency-division multiplexing (OFDM); turbo equalization
• ISSN: 1053-587X; 1941-0476
• DOI: 10.1109/TSP.2008.929129

We propose low-complexity block turbo equalizers for orthogonal frequency-division multiplexing (OFDM) systems in time-varying channels. The presented work is based on a soft minimum mean-squared error (MMSE) block linear equalizer (BLE) that exploits the banded structure of the frequency-domain channel matrix, as well as a receiver window that enforces this banded structure. This equalization approach allows us to implement the proposed designs with a complexity that is only linear in the number of subcarriers. Three block turbo equalizers are discussed: two are based on a biased MMSE criterion, while the third is based on the unbiased MMSE criterion. Simulation results show that the proposed iterative MMSE BLE achieves a better bit error rate (BER) performance than a previously proposed iterative MMSE serial linear equalizer (SLE). The proposed equalization algorithms are also tested in the presence of channel estimation errors.