Iterative channel estimation and decoding of turbo coded SFBC-OFDM systems

Hakan Doǧan*, Hakan A. Çirpan, Erdal Panayirci

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)

Abstract

We consider the design of turbo receiver structures for space-frequency block coded orthogonal frequency division multiplexing (SFBC-OFDM) systems in the presence of unknown frequency and time selective fading channels. The Turbo receiver structures for SFBC-OFDM systems under consideration consists of an iterative MAP Expectation/Maximization (EM) channel estimation algorithm, soft MMSE-SFBC decoder and a soft MAP outer-channel-code decoder. MAP-EM employs iterative channel estimation and it improves receiver performance by re-estimating the channel after each decoder iteration. Moreover, the MAP-EM approach considers the channel variations as random processes and applies the Karhunen-Loeve (KL) orthogonal series expansion. The optimal truncation property of the KL expansion can reduce computational load on the iterative estimation approach. The performance of the proposed approaches are studied in terms of mean square error and bit-error rate. Through computer simulations, the effect of a pilot spacing on the channel estimator performance and sensitivity of turbo receiver structures on channel estimation error are studied. Simulation results illustrate that receivers with turbo coding are very sensitive to channel estimation errors compared to receivers with convolutional codes. Moreover, superiority of the turbo coded SFBC-OFDM systems over the turbo coded STBC-OFDM systems is observed especially for high Doppler frequencies.

Original languageEnglish
Pages (from-to)3090-3101
Number of pages12
JournalIEEE Transactions on Wireless Communications
Volume6
Issue number8
DOIs
Publication statusPublished - Aug 2007
Externally publishedYes

Funding

Manuscript received January 5, 2006; revised May 11, 2006; accepted August 16, 2006. The associate editor coordinating the review of this paper and approving it for publication was D. Huang. This research has been conducted within the NEWCOM Network of Excellence in Wireless Communications funded through the EC 6th Framework Programme and the Research Fund of Istanbul University under Projects 513/05052006, T-856/02062006, UDP-838/27072006, and UDP-732/05052006. This work was also supported in part by the Turkish Scientific and Technical Research Institute (TUBITAK) under Grant 104E166. Part of the results of this paper were presented at the the 4th International Symposium on Turbo Codes & Related Topics, Munich, Germany, April 3-7, 2006.

FundersFunder number
EC 6th Framework Programme
TUBITAK104E166
Turkish Scientific and Technical Research Institute
Istanbul ÜniversitesiT-856/02062006, 513/05052006, UDP-732/05052006, UDP-838/27072006

    Keywords

    • EM algorithm
    • MAP channel estimation
    • OFDM systems
    • Space-frequency coding
    • Turbo receiver

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