Keyhole effect in MIMO wireless Channels - Measurements and Theory

Research output: Contribution to journalArticle


It has been predicted theoretically that for some environments, the capacity of wireless multiple-input multiple-output systems can become very low even for uncorrelated signals; this effect has been termed "keyhole" or "pinhole". In this paper the first unique measurements of this effect are presented. The measurements were performed in a controlled indoor environment that was designed to obtain a keyhole channel. We analyze limitations due to measurement imperfections for measurement-based capacity calculations and keyhole investigations. We further present a bound for the higher eigenmodes as a function of the finite measurement signal-to-noise ratio and multipath component leakage. The bound is compared to the measurement results and shows excellent agreement. Finally, we analyze the envelope distribution and, as expected from theory, it follows a double-Rayleigh distribution


Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Electrical Engineering, Electronic Engineering, Information Engineering


  • measurements, pinhole, eigenvalue, double-Rayleigh, capacity, MIMO, keyhole
Original languageEnglish
Pages (from-to)3596-3604
JournalIEEE Transactions on Wireless Communications
Issue number12
Publication statusPublished - 2006
Publication categoryResearch