4Ã\x974 MIMO Experimental Test-bed using COTS at ISM Band

This paper presents the implementation of a 4times4 multiple input multiple output (MIMO) test-bed that is employed for channel characterization using virtual MIMO indoor channel sounding technique. The 4times4 MIMO operates at ISM frequency of 2.45 GHz with 5 MHz of bandwidth using low cost commercially available off-the-shelf components (COTS). The system benefits from direct conversion transceiver units, reported before. Channel propagation measurements were performed in a rich multi-path environment by employing a virtual MIMO indoor wireless channel sounding as well as a direction of arrival (DOA) estimation algorithms. The channel sounding technique employs sequential switching of 1times4 single input multiple output (SIMO) channels to realize a virtual 4times4 MIMO experiments in a stationary channel environment. A hardware calibration method is also developed as a critical part of the MIMO evaluation. The DOA experiment, which employs a linear four-element patch antenna array at the receiver and a single patch antenna at the transmitter, provides a maximum of 15 degrees offset using Bartlett algorithm. The measured channel response matrix is also verified through comparison with other published results