MMSE turbo equalisation for real-valued symbols

Guido Dietl, Wolfgang Utschick

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

This paper deals with iterative or turbo receivers where the maximum a posteriori detector has been replaced by a widely linear filter minimising the mean square error, that is the widely linear Wiener Filter (WF). In communication systems where the transmitted symbols can be assumed to be realisations of a non-circular random variable, widely linear processing outperforms the linear one. Besides the non-circularity due to the a priori information fed back in the turbo scheme, we investigate real-valued modulation alphabets which are non-circular even if the a priori information is zero. We derive the widely linear WF for this case and observe that the number of floating point operations involved in its computation, is higher than the one of the linear WF. Nevertheless, they have the same order of computational complexity. Moreover, we reveal the relationship between the proposed widely linear equaliser and interference cancellation based on the available a priori information. Simulation results of a frequency-selective turbo system show that despite of the increased computational complexity, the performance gain of widely linear processing compared to the linear one, is negligible. However, in systems without turbo feedback, the widely linear WF outperforms tremendously the linear one.

Original languageEnglish
Pages (from-to)351-359
Number of pages9
JournalEuropean Transactions on Telecommunications
Volume17
Issue number3
DOIs
StatePublished - May 2006

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