Power control and diversity in feedback communications over a fading channel

Ilkka Saarinen, Aarne Mämmelä

    Research output: Contribution to journalArticleScientificpeer-review

    3 Citations (Scopus)


    Pilot-symbol-assisted modulation system using feedback minimum mean-square error (MMSE) power control in subject to an unavoidable feedback delay, and in conjunction with diversity, is considered over a slow Rayleigh fading channel. Feedback MMSE power control is defined as a power-control function, with feedback MMSE predictions of the current channel fading gains as input that minimizes the system-error probability. The use of feedback requires causality, and an MMSE predictor has to be employed for the purpose of power control. Previously, in the literature, the predictor was used also in detection. The pilot-symbol system with MMSE power control is shown to achieve a clear performance improvement by employing a smoother, instead of the predictor, in detection. Furthermore, the performance loss caused by a feedback delay of 10%-20% from the channel coherence time appeared to be minor with reasonable bit-error rate levels. Finally, additional performance improvement using low-order diversity was shown to be considerable.
    Original languageEnglish
    Pages (from-to)1857 - 1861
    Number of pages5
    JournalIEEE Transactions on Communications
    Issue number11
    Publication statusPublished - 2004
    MoE publication typeA1 Journal article-refereed


    • Rayleigh channels
    • delays
    • diversity reception
    • error statistics
    • feedback
    • least mean squares methods
    • power control
    • telecommunication control
    • feedback communication
    • low-order diversity
    • minimum mean square error
    • pilot-assisted modulation system
    • system-error probability
    • closed-loop method


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